Rapid Ecological Integrity Assessment Metrics to Restore Wildlife Habitat and Biodiversity for Shortleaf Pine–Oak Ecosystems

Nordman, Carl; Faber-Langendoen, Don; Baggs, Joanne

doi:10.3390/f12121739

Open AccessArticle

Rapid Ecological Integrity Assessment Metrics to Restore Wildlife Habitat and Biodiversity for Shortleaf Pine–Oak Ecosystems

by

Carl Nordman

^1,*

,

Don Faber-Langendoen

¹ and

Joanne Baggs

²

¹

NatureServe, Conservation Science Division, Arlington, VA 22202, USA

²

USDA Forest Service, Southern Region, Atlanta, GA 30309, USA

^*

Author to whom correspondence should be addressed.

Forests 2021, 12(12), 1739; https://doi.org/10.3390/f12121739

Submission received: 1 October 2021 / Revised: 11 November 2021 / Accepted: 30 November 2021 / Published: 9 December 2021

(This article belongs to the Special Issue Applied Forest Classification)

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Abstract

:

Open woodlands dominated by shortleaf pine (Pinus echinata Mill.) and oak are historically an important component of the landscape across the southeastern United States. These ecosystems support numerous wildlife species, many of which have declined in recent years as the amount and condition of their habitat have declined. Land managers and private landowners need guidance on how to efficiently and accurately quantify the condition and wildlife habitat value of the pine stands that they manage. Here we provide a set of rapid assessment metrics, based on NatureServe’s ecological integrity assessment (EIA) method, to (a) identify exemplary tracts that provide the best habitat for key wildlife species, and (b) monitor restoration efforts to assess progress toward the improved quality of existing tracts. To ensure an ecologically appropriate scaling of metrics, we distinguished six types of shortleaf pine–oak woodland: A.—Interior Highlands shortleaf pine–oak (including A.1—shortleaf pine–oak forest and woodlands; A.2—shortleaf pine–bluestem woodlands); B—montane longleaf pine–shortleaf pine woodlands; C—southern Appalachian pine–oak woodlands; D—West Gulf coastal plain shortleaf pine–oak woodlands; and E—southeast coastal plain and Piedmont shortleaf pine–oak woodlands. We relied on a narrative conceptual model and peer review-based indicator selection to identify a core set of 15 stand-level metrics (two were optional). Individual assessment points (thresholds) and ratings (Excellent, Good, Fair, and Poor) were developed that were sensitive to the distinct attributes of each of the five shortleaf pine–oak and Appalachian pine–oak types. Values for the metrics can all be collected using rapid field methods, such as using basal area prisms and ocular (visual) estimates of cover. Protocols for the consistent application of these EIA methods are provided. A case study is presented from the Cherokee National Forest in Tennessee. These methods provide improved and rapid EIA metrics for all shortleaf pine–oak ecosystems in the southeastern US to help guide conservation-minded landowners in assessing the biodiversity and priority wildlife values of shortleaf pine–oak and southern Appalachian pine–oak ecosystems.

Keywords:

indicators; ecological restoration; forest management; prescribed fire; pine–oak woodlands; Pinus echinata

1. Introduction

The open savannas and woodlands dominated by southern yellow pines are historically a large component of the landscape across the southeastern United States. These pine savannas and open, usually grassy, woodlands are dominated by longleaf (Pinus palustris Mill.), slash (Pinus elliottii Engel.), shortleaf (Pinus echinata Mill.), loblolly (Pinus taeda L.), pitch (Pinus rigida Mill.), and Table Mountain (Pinus pungens Lamb.) pines (taxonomy follows the PLANTS database [1]). They support high plant and animal diversity, with over 900 plant species considered endemic to this and adjacent ecosystems [2], and they are an integral part of the North American coastal plain biodiversity hot spot [3]. They provide several key ecosystem services, including hunting and other outdoor recreation, watershed protection, and high-quality, sustainable forest products, such as poles and pilings, in addition to high biodiversity. However, despite their importance, these open pine ecosystems have experienced many management challenges. As human populations increased, and land management practices and land-use patterns changed, these once-dominant open pine ecosystems were cleared for agriculture and/or development, resulting in significant declines in both the extent and quality of open pine ecosystems across the southeast [4]. In addition, a lack of wildland fire has adversely affected ecosystem structure and function, as well as the flora and fauna that rely on the ecological conditions created by frequent low-intensity fire [5].

Longleaf-dominated woodlands have been the focus of southern pine stand restoration [6,7,8,9,10,11,12] but other open pine stands in the region that are dominated by shortleaf pine, as well as pitch pine and Table Mountain pine in the southern Appalachians, have also experienced substantial declines. Stands of shortleaf pine and shortleaf pine–oak are estimated to have declined by over 90% and have continued to decline since 1980 [5]. These shortleaf pine woodlands provide a habitat for many of the same plant and animal species that depend on longleaf pine ecosystems, further south. However, their ecological characteristics are not the same as those of longleaf ecosystems. The longleaf pine rapid assessment metrics were extended to include other southern open pine ecosystems [9]; there is a need to account for the distinctive features of shortleaf, pitch, and Table Mountain pine–oak woodlands. Recognition of this need led the Southern Region of the Forest Service to support the Shortleaf Pine Initiative, which published a shortleaf pine restoration plan [13]. That plan provided some guidance on assessing ecological conditions but gave no developed set of metrics to guide restoration.

Developing assessment methods of ecological condition necessitates careful consideration of the complexity of terrestrial ecosystems. It is important to develop, test and validate indicators that provide reliable, cost-effective, easily measured, and ecologically meaningful information on ecological integrity. If well-chosen, indicators can also provide early signs of ecosystem degradation and identify areas at risk of ecosystem collapse [14,15]. These methods are broadly referred to as ecological integrity assessment (EIA) methods [16,17,18,19,20,21,22].

Here we propose a set of rapid EIA metrics that can be applied to any of the shortleaf and southern Appalachian pine ecosystems in the southeast, building on the EIA methods previously developed for longleaf pine woodlands [8,9]. Our goal is, in part, to provide the Forest Service with an assessment method that can be applied to all such pine–oak ecosystems of the National Forests of the Southern Region of the Forest Service, as well as other federal, state, private and Native American lands in the region. Specifically, we address three objectives:

To provide a common framework for delineating the various broadly distinct shortleaf pine–oak (SPO) and Appalachian pine–oak (AP) ecosystems.
Product: Classification of SPO and AP ecosystems, including distribution according to ecoregion and National Forests.
To define the desired reference conditions that can guide the management of SPO and AP ecosystems, where the primary objective is the conservation of wildlife and biodiversity maintenance.
Product: A set of reference conditions for SPO and AP ecosystems, evaluated using ecological integrity indicators.
To provide a rapid EIA assessment protocol that is usable by land managers to assess the condition of stands.
Product: A protocol, usable in the field, that guides the evaluation process, using indicators with ratings of Excellent, Good, Fair, and Poor.

1.1. Definition of Southern Open Pine Ecosystems

We define SPO and AP ecosystems broadly, in concert with the definition of Southern yellow pine ecosystems that was used to guide the longleaf work [8]:

Southern open pine woodlands include large-scale (or formerly large-scale) ecosystems dominated by an open canopy of southern yellow pine trees and used by a great variety of game and non-game wildlife species and plants. Typical dominant species include not only the longleaf pine (Pinus palustris) and shortleaf pine (Pinus echinata) but also pitch pine (Pinus rigida), Table Mountain pine (Pinus pungens), loblolly pine (Pinus taeda), and slash pine (Pinus elliottii). In the coastal plain, longleaf pines historically occurred in extensive large-scale patches, whereas in the Appalachians, pine woodlands often occur in smaller patches on ridges or dry slopes. Historically, these open pine ecosystems contained a diverse ground cover composed of native warm-season grasses and forbs, often with some low shrubs and only sparse tall shrubs. These open conditions were maintained by natural processes, including fires and grazing. These ecosystems are to be found from the West Gulf coastal plain and the Ozark and Ouachita Mountains to the southern Appalachians, Piedmont, the Atlantic and East Gulf coastal plains, and south into the Florida Peninsula.

1.2. Priority Wildlife Species

A list of 64 representative wildlife species was developed for the SPO and AP ecosystems (Appendix A, Table A1). Of these, 18 are rare or focal species for this project (Appendix A, Table A2). Based on the literature and an expert review, populations of these species should respond positively in open pine landscapes with improved ecological integrity [6,7,8,9,13].

1.3. Management of Southern Open Pine Forests

There is a variety of forest management approaches available to regenerate oak and pine stands, but prescribed fire is very important for limiting the encroachment of fire-intolerant trees, and for maintaining the open grass and low shrub-dominated groundcover that is preferred by wildlife [5,13]. Specific management goals will vary with the intent of the landowners and land managers, but may include timber harvesting, including high-value and small diameter timber (e.g., biomass), the use of herbicides to reduce competition (particularly to control invasive exotic plants), the reseeding of native groundcover species (such as native warm-season grasses, native legumes and other native plants appropriate for the site), mechanical midstory reduction, managed grazing, and other methods.

1.4. Purpose

The purpose of these rapid ecological assessment metrics is to help guide ecological restoration forest management decisions in distinct shortleaf pine–oak ecosystems. We demonstrate the usefulness of ecological classification for developing these metrics. We provide methods to repeatably measure ecological integrity and to enable the assessment of changes in condition using the categories of Excellent, Good, Fair, and Poor. As forest management or ecological restoration decisions are implemented, the metrics presented here can enable the assessment of progress over time and can be applied in conjunction with other common timber cruising or wildlife survey methods.

2. Materials and Methods

2.1. Ecological Integrity Assessment Methods: Metrics-Based Approach

NatureServe and its network partners from various state Natural Heritage Programs, in collaboration with a variety of agency partners, have developed methods to assess ecosystem condition, using the concept of ecological integrity [19,20,21,23]. Ecological integrity can be defined as “an assessment of the structure, composition, function, and connectivity of an ecosystem as compared to reference ecosystems operating within the bounds of natural or historical disturbance regimes” [19,24]. To have integrity, an ecosystem should be relatively unimpaired across a range of ecological attributes and spatial and temporal scales.

Our approach to developing metrics for SPO and AP ecosystems builds on the collaborative process used for longleaf pine metrics [8,25]. Core to the methodology is coherent and consistent conceptual ecological models for specific ecosystem types that identify the major ecological factors and key attributes for which indicators are most needed. The process of modeling and indicator selection leads to a practical set of metrics, by which field measures of the indicators can be collected and rated categorically as Excellent, Good, Fair, or Poor. Indicators can be developed for various data sources (Level 1—remote-sensing data, Level 2—rapid field data, and Level 3—intensive field data), but here we emphasize Level 2 rapid assessment methods. Our goal was to develop field metrics that were easy to apply, fast, repeatable, ecologically relevant, sensitive to conditions, and complementary (not redundant). We followed a six-step process for assessing ecological integrity, as described by others [18,19,21,26,27], namely:

Specify the ecosystem types
Develop the conceptual models of ecosystem types
Specify the level of assessment
Select the indicators and metrics
Determine metric ratings (assessment points/thresholds)
Provide assessment tools

2.1.1. Specification of Ecosystem Types

Ecological classifications help managers better understand natural variability within and among ecosystem types, and thus play an important role in helping to distinguish sites that differ across a gradient of conditions and stressors. Given the diversity of SPO and AP types, it is critical to organize existing knowledge about their location in the landscape, how they function, and how management decisions affect those functions. We can then organize this knowledge into a conceptual model or descriptive summary of how the ecosystem functions (see Step 2, below).

Shortleaf pine is the most widespread pine species in the eastern United States, occurring in 22 states, with a range of over 1,140,000 square km (440,000 square miles) [28]. It is found in pine-dominated stands and as a component of mixed oak forests and open woodlands. It can grow on a range of soil types, aspects, geology, and hydrologic gradients [13,29]. To classify this variation into ecosystem types, we used the classification of southern open pine woodlands, as developed for the United States National Vegetation Classification (USNVC), a federal standard for classification of the vegetation of the United States [30], and part of the International Vegetation Classification [25,31]. We emphasized types at the USNVC group and alliance levels, the same level(s) at which longleaf pine assessments methods were developed [8] and the level at which wide-scale mapping of vegetation is now available [32]. We developed five SPO groups and one AP group that served as our base units for developing rapid assessment metrics (Table 1, Figure 1). We briefly describe the ecological characteristics of these groups, in preparation for developing conceptual models.

Interior Highlands Shortleaf Pine–Oak
A.1.
Interior Highlands Shortleaf Pine–Oak Forests and Woodlands
These dry, dry-mesic, and mesic Interior Highlands shortleaf pine–oak forests and woodlands have their most extensive areas in the Ozark–Ouachita Highlands, with shortleaf pines and oaks (Quercus spp.) as the canopy codominants, generally mixed with hickories (Carya spp.) and other hardwoods. The mid-story is sparse, the tall shrub layer is sparse to patchy, and the short shrub layer may be patchy to dense. The herbaceous understory is dominated by graminoids, including the little bluestem (Schizachyrium scoparium (Michx.) Nash), oat grass (Danthonia spp.), woodoats (Chasmanthium spp.), and Pennsylvania sedge (Carex pensylvanica Lam.), with various forbs, such as elmleaf goldenrod (Solidago ulmifolia Muhl. ex Willd.), and pale purple coneflower (Echinacea pallida Moench.).
A.2.
Interior Highlands Shortleaf Pine–Bluestem Woodlands
These dry and dry-mesic Interior Highlands shortleaf pine–bluestem woodlands have their most extensive areas on long ridges in the Ouachita Highlands, with shortleaf pine as the canopy dominant, the subcanopy and midstory are open with scattered oaks, hickories, and other hardwoods. The tall shrub layer is largely absent, and the short shrub layer is very open. The understory is characterized by big bluestem (Andropogon gerardii L.) and little bluestem, as well as other prairie grasses, legumes, and various other forbs.
Montane Longleaf Pine–Shortleaf Pine Woodlands
Mountain longleaf pine–shortleaf pine woodlands occur on dry sites and ridges in certain Appalachian or Piedmont areas of Alabama, Georgia, and the Carolinas. These pine woodlands have longleaf pine and shortleaf pine as the canopy dominants, which are generally mixed with oaks, hickories, and other hardwoods. Open tall and short shrub layers are common, and in more open stands, the understory is characterized by Elliott’s bluestem (Andropogon gyrans Ashe.), splitbeard bluestem (Andropogon ternarius Michx.), big bluestem, oatgrass, little bluestem, Indian grass (Sorghastrum nutans Nash), other prairie grasses and forbs including greater tickseed (Coreopsis major Walter), tick trefoil (Desmodium spp.), and lespedeza (Lespedeza spp.).
Southern Appalachian Pine–Oak Woodlands
Southern Appalachian pine–oak woodlands mainly occur in the Southern Appalachian Mountains, including the Cumberland Mountains and plateaus. These open woodlands have pitch pine and shortleaf pine, mixed with oak at lower elevations, and, at middle elevations and on slopes and steep ridges, pitch pine and Table Mountain pine mixed with oak are to be found. These Southern Appalachian pine–oak woodlands tend to be shorter-statured than other shortleaf pine–oak woodlands, have more sparse herbaceous cover, dense short shrubs (particularly heathland plants), and more open tall shrubs, midstory and canopy. These ecosystems can occur on rugged slopes.
West Gulf Coastal Plain Shortleaf Pine–Oak Woodlands
These West Gulf Coastal Plain upland woodlands are dominated by a mix of shortleaf pine and loblolly pine with hardwoods, primarily the white oak (Quercus alba L.), southern red oak (Quercus falcata Michx.), post oak (Quercus stellata Wangenh.), as well as the scrub oaks, bluejack oak (Quercus incana W.Bartram), sand post oak (Quercus margaretta Small.), and Arkansas oak (Quercus arkansana Sarg.). Other trees include the black oak (Quercus velutina Lam.), mockernut hickory (Carya tomentosa K.Koch), black hickory (Carya texana Buckl.), hawthorn (Crataegus spp.), and hop hornbeam (Ostrya virginiana Mill.). The midstory, tall, and short shrub layers are open. The graminoid layer is from open to very dense; some typical grasses include woodoats, roundseed panicgrass (Dichanthelium sphaerocarpon Gould), and little bluestem.
Southeastern Coastal Plain and Piedmont Shortleaf Pine–Oak Woodlands
These southeastern coastal plain upland woodlands occur east of the Mississippi River. They are dominated by a mix of shortleaf pine with hardwoods, primarily white oak, southern red oak, post oak, scarlet oak, and scrub oaks such as the bluejack oak and sand post oak. Other trees include black oak, mockernut hickory, hawthorn, red maple (Acer rubrum), sourwood (Oxydendrum arboreum DC.), and hop hornbeam. The midstory, tall, and short shrub layers are open. The graminoid layer is open to very dense; some typical grasses include blackseed speargrass (Piptochaetium avenaceum Parodi.), poverty oatgrass (Danthonia spicata L.), woodoats, roundseed panicgrass, and little bluestem.

2.1.2. Develop Conceptional Models

Historic information on natural processes and the natural range of variation (NRV) for SPO groups show that these ecosystems are adapted to frequent, two- to twenty-year return interval fires, needing burning for natural regeneration [33,34]. As with longleaf pines, fire plays a key role in maintaining forest structure and composition. More frequent fires result in an open woodland structure, and an open overstory of either pure pine or, more often, mixed pine and oak. There is a variable shrub layer and, often, a well-developed herbaceous understory of grasses and wildflowers. Fire limits the encroachment of fire-intolerant hardwoods and less fire-tolerant conifers (especially the eastern red cedar). Even in closed-canopy forests, infrequent fires maintain shortleaf pine forest types in mixed pine stands [13,29].

Altered fire regimes, in terms of intensity, frequency, and season of burn, have drastically changed the ecosystem of the shortleaf pine forest. Lack of fire allows the establishment of fire-intolerant hardwood species, such as water oak (Quercus nigra L.), sweetgum (Liquidambar styraciflua L.), tulip poplar (Liriodendron tulipifera L.), and red maple [35,36,37]. Shortleaf pine recruitment is reduced due to a lack of fires [38]. In the southern Appalachians, where prescribed fire has been reintroduced, the recruitment of shortleaf pines is often lacking, due to the absence of a seed source from mature trees [39]. Loss of shortleaf pines and an open canopy structure had a negative impact on many wildlife species [13].

The general fire regime, ecosystem structure, and compositional diversity of SPO and AP ecosystems, as described above, share many basic features with longleaf pine woodlands, and we can largely use the conceptual models of that system, as developed by Loudermilk et al. (2011) [40] and Hanberry et al. (2018) [41], for developing our assessment method (Figure 2).

Using this conceptual model as a guide, we structured our selection of indicators to span the following key ecological attributes.

Canopy:

Canopy and midstory trees: indicators are needed that measure both pine and hardwood abundance and distinguish fire-tolerant pines and hardwoods from fire-intolerant pines and hardwoods; these measures track the degree to which woodland management and fire regime is maintaining a fire-tolerant tree composition.
Canopy cover and size: Indicators are needed to assess the degree to which woodland management and the fire regime maintain an open and mature canopy structure.

Shrubs and Herbs:

Indicators are needed to assess the amounts of tall and short shrub cover, graminoid and overall herbaceous cover, including the cover of invasive plants.

Soils:

Indicators are needed to assess damage to the soil profile caused by management and other activities (including past land use).

Visually, our conceptual model is captured by historic images of SPO and AP systems that reflect the open woodland conditions of the model (see photos in Figure 3) and by various restoration efforts already put in place to reintroduce those historic conditions (Figure 3).

2.1.3. Specify the Level of Assessment

To develop an effective, rapid condition assessment metric approach, our protocols needed to be:

Able to distinguish condition/ecological integrity of remnant stands and restored stands using metrics that are, where necessary, sensitive to particular types of open pine ecosystems
Repeatable, based on clearly defined protocols
Quick to apply in the field, with multiple locations assessed in a site visit of 2–4 h
Relatively simple and easy for field crews to implement
Able to detect change over time (for monitoring)
Contribute information to regional assessments.

We developed indicators that met these criteria as follows:

Canopy—The abundance of southern yellow pine and hardwood can be measured using either (a) estimates of the basal area from 2 × BAF (basal area factor) metric prism or 10 × BAF English prism from at least four locations within an assessment area, or (b) direct measures of all stems that are 12.7 cm (5”) diameter or greater at 1.37 m (54”), diameter at breast height (DBH) in centimeters. In both cases, measures are converted to basal area measures in m²/ha (ft²/acre). Basal area metrics are documented using metric system (SI) units, but the English units are also provided as they are commonly used by managers within the United States.

Fire tolerance—To ensure consistency in the indicator process, we developed a list of tree species that are considered largely fire-tolerant or fire-intolerant (see Nordman et al., 2021) [42]. This was achieved through a literature review, and with expert input. Factors contributing to hardwood fire tolerance include:

Bark resistance to fire
Ability to resprout after fire
How well any downed leaves burn in fuel beds
How fire influences recruitment
Regular occurrences of fire in stands that have been frequently burned over a long period of time.

Mid-Story, Shrubs and Herbs—Taking visual (ocular) estimates of percentage cover, typically using 5%–10% intervals.

Composition—Emphasizing tree species identification. Researchers should rely on growth form categories for shrubs and herbs, but the option of collecting species composition data should be provided, given the widespread availability of floristic quality assessment (FQA) methods. The one exception is that invasive plant species need to be distinguished from noninvasive species.

Soils—Reliance on visual (ocular) estimates of soil disturbance.

2.1.4. Select the Indicators and Metrics

Metrics specify both the measures needed to quantify the indicators, and also the rating scale by which those measures indicate the levels of ecological integrity. To guide the selection process, the following criteria were used for each metric: (a) representing a key ecological attribute or ecosystem service (from the conceptual model), (b) not being too noisy/variable (i.e., both short and long-term trends should be detectable), (c) not being prone to measurement error, (d) cost-effective, (e) feasible (including the speed and ease of measurement in the field), (f) relevant to management objectives, and (g) commonly being collected.

2.1.5. Determine Metric Assessment Points/Thresholds

Using knowledge of the natural range of variation (NRV) as a guide to the reference condition, we can approximate both the natural variation in a metric and the variation caused by stressors. In this step, we established ecological “assessment points” that distinguished expected or acceptable conditions from undesired ones that warrant further evaluation or management action (see Bennetts et al., 2007) [43], regarding “assessment points” versus “thresholds” as guides for assessing the ecosystem’s condition). We use four rating categories for condition (Excellent, Good, Fair, and Poor) for each of the metrics, using assessment points that can be readily measured as part of a rapid assessment protocol. We conducted a literature review for insights into the factors driving changes in the various indicators of ecological integrity, and characteristic wildlife [42]. We then refined the metric ratings for SPO types that are already partly covered by the Longleaf Pine–Oak (LPO) project [8,9], and we established new metric ratings for the AP. An example using our metric and assessment points approach is shown in Table 2.

2.1.6. Provide Assessment Tools

We developed definitions for the metrics, shown in Table 3, and summary tables (Appendix B) for each of the six SPO and AP groupings, showing the metrics and their ratings, following the format shown in Table 2 and Table 4.

Protocols are also needed to ensure that consistent and clear guidance is provided to field crews on how data are gathered for each metric. We developed protocols that included the following key pieces of information: (1) definition of the metric, (2) rationale for the selection of the metric, (3) measurement protocol, (4) metric ratings, (5) data for metric ratings, (6) scaling rationale, (7) citations.

2.2. Peer-Review Workshops to Refine the Metrics

Peer review meetings were held with the Forest Service staff and external partners in January and February 2021. In these meetings, we conducted a systematic review of all metrics, including an evaluation of the assessment points. In the introductory meeting, we presented the need for monitoring of these ecosystems, the background, characteristic wildlife, rapid EIA approach, and goals in the development of the rapid assessment metrics for SPO and AP ecosystems. In each of the three subsequent meetings, we reviewed the metric ratings for the various SPO and AP groups in a specific region: namely, the Interior Highlands (Ozark and Ouachita Highlands, Groups A.1 and A.2), the Montane and Southern Appalachian (Groups B and C) and the Coastal Plain and Piedmont (Groups D and E). All review comments were tracked, and a formal peer review response form summarizes how we addressed these comments (available on request from J.B.).

2.3. Case Study of EIA Metrics

To advance our understanding of the use of metrics, we evaluated the condition of stands, utilizing an existing dataset from the Cherokee National Forest in eastern Tennessee. Here, and across the Southern Region of the Forest Service, plot data is collected to measure the effects of prescribed fire [44,45]. We selected 11 sites that correspond to the AP group where shortleaf or pitch pine stands were being managed and monitored. Stands varied according to the levels of oaks and southern yellow pines present. Each site has a different fire history related to frequency and seasonality, with 6 sites experiencing some prescribed burning and 5 sites that did not.

We used the relevant plot measurements (basal area, canopy cover, species, etc.) to assign a score based on metrics variants that were appropriate for the AP group. Absolute cover was converted to canopy cover, based on Jennings et al. (2009) [46] and, for 2 midstory metrics, the basal area was used to estimate canopy cover. The monitoring protocol generally specifies data collection for 10 of the 14 metrics; 4 canopy, 4 midstory/shrub, and 2 ground layer metrics; however, shrubs (2 metrics) and ground cover (2 metrics) were not consistently collected because some portions of the fire-effects monitoring protocol are optional, based on the objectives of the prescribed burn. Thus, only 6 metrics were sufficiently measured across the plots. The presence of invasive species, forest soil disturbance, and the canopy cover of southern yellow pine were not scored for all plots.

3. Results

3.1. Ecosystem Types

Our initial set of SPO and AP types provided a suitable framework for guiding our development of metrics. One refinement to the Interior Highlands shortleaf pine–oak group (A) was to split it into two groups: A.1, Interior Highlands shortleaf pine–oak Forest and woodlands (IH1); and A.2, Interior Highlands shortleaf pine–bluestem woodland (IH2). This refinement was made early in the process and reflects the very different site conditions and fire regimes that shape these two groups. Another refinement was to split West Gulf coastal plain pine–oak woodlands (WG) from the southeast coastal plain and Piedmont shortleaf pine–oak woodlands (CP) because in the West Gulf coastal plain group, loblolly pine and shortleaf pine are both important canopy-dominant trees. These distinctions are also recognized at the USNVC group or alliance levels (Table 1).

3.2. Metrics List

Our peer review-based process identified 15 stand metrics (Table 3). For the stand metrics, there are 6 canopy metrics, 4 midstory/shrub metrics, 4 ground layer metrics, and 1 soil metric. A brief definition and the measures used for each metric are provided in Table 3 and in Appendix B. Full documentation for each metric can be found in the study by Nordman et al. (2021) [42].

As indicated by the conceptual model, the relative roles of pines and hardwoods are important indicators of these ecosystems, and the canopy and midstory metrics emphasize these attributes. Both VCAN4—Canopy Fire-Intolerant Tree Basal Area and VMID2—Midstory Fire-Intolerant Tree Cover include both hardwoods and conifers (the longleaf metrics only included hardwoods) because several conifers, such as red cedar (Juniperus virginiana L.) and eastern white pine (Pinus strobus L.) are relatively fire-intolerant in the region where SPO and AP groups are found. Overall stand structure is assessed via VCAN3—Southern Yellow Pine Stand Size Structure and VCAN6—Stand Density Index. The stand density index is optional because it is a complex metric to interpret, and it has not yet been developed for AP. Thus, five main metrics are developed to characterize the canopy layer.

Shrub and herb layer indicators are used as good short- to medium-term responders to fire regimes, and thus help interpret fire dynamics. VGRD2—Native Graminoid Cover is broader than the equivalent LPO Native Warm Season Grass metric because a mix of cool and warm season grasses occur in many SPO and AP groups. VGRD3—Floristic Quality Index, Mean C replaced the LPO Native Wiry Graminoid Cover metric because it more comprehensively assesses all species. It does require greater botanical expertise and thus is an optional metric, but the metric has been widely applied in many condition assessments, such that we encourage its development and use.

SDIS1—Forest Soil Disturbance assesses the soil condition directly, rather than the LPO usage of plant indicators to track soil disturbance (Herbaceous Indicators of Soil Disturbance). Our metric both reduces the botanical expertise required for the metric and is a more direct measure of the key ecological attribute being measured.

3.3. Metric Assessment Points

The metric assessment points, varied by SPO and AP types, reflective of their different biological and ecological characteristics, are shown in Table 4.

3.3.1. Canopy

Generally, reference (excellent) conditions include both a dominant pine component and a smaller amount of fire-tolerant hardwoods, such that pines contribute at least 25% cover, and broadly have a 2:1 ratio of fire-tolerant southern pines to fire-tolerant hardwoods, especially oaks. However, Interior Highlands shortleaf pine forest and woodlands contain a higher proportion of fire-tolerant hardwoods. Poor conditions are indicated whenever fire-intolerant hardwoods are three- to four times more abundant than southern pines.

West Gulf coastal plain (WG) and southeast coastal plain–Piedmont (CP) woodland types showed differences in their dominant pines but otherwise prompted the same assessment points across all metrics, sometimes distinct from the Interior and Appalachian woodlands (Southern Pine abundance in VCAN1 and VCAN2) and sometimes similar. Similarly, Interior Highlands had the same assessment points as montane longleaf pine–shortleaf pine woodlands (ML) and AP, sometimes shared with the coastal plain groups. ML had a distinct metric variant (VCAN3.v2) related to the distinctive character of montane longleaf pine ecosystems; namely, the flat-topped crowns in older mature longleaf trees. AP has a metric variant related to the smaller-diameter trees of these pines compared to the others. Thus, the metric ratings were sensitive to the distinct canopy characteristics of each group.

3.3.2. Midstory/Shrub

In general, SPO and AP groups have very open midstories, in reference (excellent) conditions. As with the canopy, the midstory patterns were broadly consistent among the groups, with midstory fire-tolerant hardwoods having no more than 2–10% cover when in excellent condition, and greater than 35%–50% when in poor conditions. Fire-intolerant hardwoods also prompt low percentages when stands are in excellent condition, and thresholds for poor conditions are 20%–30% cover.

Shrub metrics vary much more widely from group to group. Tall shrub cover for excellent condition varies from <5%–10% (most groups) to as much as 30% (Interior Highlands shortleaf pine–oak forest and woodlands, IH1), and short shrub cover varies from <20% (most groups) to less than 50% (AP). Similarly, poor conditions are typically encountered when tall shrub cover exceeds 25%–30%, but this cover could be as high as 50% in IH1. AP stands out as largely having a dominant low shrub heath layer in reference conditions, rather than graminoid, herbaceous, or tall shrub layers, with as much as 50% of low shrub cover being part of (excellent) reference conditions, with poor conditions only occurring when the low shrub heath cover exceeds 80%.

3.3.3. Ground Layer

As with the shrub layers, herbaceous and graminoid cover varies from as little as 15% in AP to as much as 35%–45% or more in the SPO groups. As noted above, AP stands out as largely having a heath rather than a graminoid or herbaceous understory. The various SPO and AP groups shared metric variants in various combinations, reflecting the individual responses of their key ecological attributes. However, as with the Canopy and Midstory metrics, the WG and CP always shared metric variants, and the Interior Highlands shortleaf pine–bluestem woodland IH2 and ML often shared the same ground layer metric variant.

3.4. Metric Summaries by Open Pine Group

As part of our collaborative process to create metrics, we determined that various combinations of each SPO and AP group varied enough to justify its own set of metrics. The metrics are summarized for each of the six habitat groups in Appendix B. The full documentation of these metric protocols [42] is available for download from NatureServe at: https://www.natureserve.org/projects/developing-rapid-assessment-metrics-measuring-open-pine-ecosystem-health-southeastern-0 (accessed on 12 November 2021).

Our effort to develop rapid assessment metrics resulted in 15 stand metrics. Together, these 15 metrics serve as the best indicators of ecological condition for SPO and AP woodlands. When taken together, these indicators can help land managers and other interested parties understand the ecological condition of their open shortleaf pine–oak stands. These 15 metrics are in four subsets, representing the canopy, midstory, ground layer, and soils. This approach of grouping metrics by strata allows users to assess the condition of the various layers separately [47].

3.5. Case Study

To advance our understanding of the use of metrics, we evaluated the condition of stands, utilizing an existing dataset. We selected 11 sites on the Cherokee National Forest where shortleaf or pitch pine was present. The overstory composition included oaks and southern yellow pines; this method may have selected plots that may not be dominated by southern yellow pines. For the analysis, 5 sites were selected (Table 5) with measurements prior to fire (baseline) or controls (no fire management), measured during 2005–2008. For sites with prescribed fire, the 6 plots were (1) measured between 2004 and 2006 after 4 to 7 years, after one prescribed fire, and (2) measured between 2016 and 2019 and had at least one additional prescribed fire. Each of the 6 metrics was individually scored and used to determine the overall stand-level condition score.

The preliminary analysis shows that the metrics helped characterize existing condition in order to evaluate sites. For the 5 sites evaluated with one prescribed fire history, the overall condition score was the same as sites with no fire (2.9—Good vs. 2.9—Good). For the 6 sites with two prescribed fires, the overall condition score did improve (to 3.2) due to the improved score in both the fire-tolerant hardwood basal area (VCAN4 1.4 to 2.3) and fire-intolerant trees metric (VCAN5 1.6 to 2.0); that is, fire helped remove the fire-intolerant tree species.

4. Discussion

4.1. Metrics-Based Approach and Reference Conditions

The metrics-based approach, used here to assess ecosystem condition, uses a well-tested EIA methodology for screening and vetting the merits of each metric, from reviewing source literature to peer review and field-testing. Our goal was to build on expert knowledge from past work on longleaf pine woodlands [8] and from existing expertise across the SPO and AP regions. The six-step protocol for developing metrics proved effective for guiding peer reviewer input on all metrics. Our team used the information and viewpoints gathered from these interactions to revise the draft metrics and produce the final assessment method.

There is concern that the current ecological conditions of ecosystems are changing so rapidly that reference conditions based on the natural range of variation (NRV), or historical range of variation (HRV), as conducted here, may no longer be relevant to our assessment of current conditions. However, there are various ways in which NRV remains an important guide [48,49]:

First, it is the knowledge of natural variability that informs our goals and evaluations of current conditions, but this knowledge does not a priori constrain how we state desired conditions for excellent or good ecological integrity or the level of ecosystem services.
Second, to suggest that we can simply take over the management of natural ecosystems without understanding NRV is to invite failures in these complex systems.
Third, the purpose of understanding NRV is not to lock us in the past but to ensure that we connect the historical ecological patterns and processes to the present and future.
Fourth, understanding NRV will ensure that we can anticipate change and emphasize resilience in the face of future changes.

Our models and our understanding of the NRV of SPO and AP can also be informed by sites that represent reference (excellent) conditions. As described by Brooks et al. (2016) [50], reference sites represent those areas that are intact or with minimal human disturbance, i.e., “reference standard” or “exemplary ecosystem occurrences.” Typically, the initial approach to identifying reference sites is to rely on a combination of factors, including naturalness, apparent ecological integrity, and lack of evidence of human disturbances, leading to degradation. Naturalness and integrity are often judged by historical fidelity (connectivity in time), a full complement of native species, characteristic species dominance and productivity, the presence of typical ecological processes such as fire, flooding, and windstorms, and minimal evidence of anthropogenic stressors [51]. The model, attributes, and metrics that document reference conditions can be adjusted through adaptive management feedback loops.

Although not described here, we also recommend assessing the landscape context, an important part of assessing ecological condition. The four landscape-scale metrics we recommend are absolute patch size, contiguous natural land cover, land use index, and perimeter with natural buffer [19]. These metrics help us distinguish between areas that may have high levels of integrity at a smaller scale but may not sustain priority wildlife long-term because of their isolation, proximity to developed areas, or small stand size.

4.2. Wildlife and Ecological Integrity Assessments

Open pine habitats, especially those dominated by longleaf pine or shortleaf pine, provide the last refuge for many at-risk and declining vertebrates and many more at-risk and declining plant species. A few species that depend on the open stand conditions being represented by excellent to good condition include the red-cockaded woodpecker (Picoides borealis), Bachman’s sparrow (Aimophilus aestivalis), northern bobwhite (Colinus virginianus), brown-headed nuthatch (Sitta pusilla), pine warbler (Setophaga pinus), prairie warbler (Setophaga discolor), and others (Appendix A). Our approach provides regional managers with methods for more accurately documenting progress toward their goals for increasing the area of excellent to good stands of open pine woodland habitat [42,52,53,54].

4.3. Application of Metrics

The method provided here is for rapid, stand-level applications and, generally, can be applied at sets of points or small plots across stands, in a manner similar to a timber cruise. To implement these rapid assessment metrics, users must first choose the SPO or AP group (the open pine ecosystem type) that best fits the area they are managing and want to evaluate. This choice could be based on one of two situations: (1) the area of interest is currently one of the SPO or AP groups and the manager wants to know its current condition; or (2) the manager wishes to restore one of these SPO or AP groups in an area that has been degraded and whose current land cover is not open pine. For the latter situation, managers will need to work with available potential site models, such as the BioPhysical setting models of LANDFIRE, or the terrestrial ecological inventory units of the Forest Service.

The data presented herein is not intended to be regulatory or administratively prescriptive, nor to conflict with any manager’s ability to meet their underlying legislative mandates. As the data and recommendations put forth here reflect the contemporary collective expertise of many ecologists, foresters, biologists, and researchers, we encourage partnerships to iteratively update and refine these data and recommendations, as we increase our knowledge and understanding of wildlife species habitat needs and management strategies within open pine ecosystems across the southeastern United States. With sufficient investment in the assessment of current stand conditions and the identification of opportunities for restoration, we hope that we can contribute to reversing the decline of shortleaf pine–oak ecosystems across the region.

Author Contributions

Conceptualization, C.N., D.F.-L. and J.B.; methodology, C.N. and D.F.-L.; formal analysis, C.N., D.F.-L. and J.B.; data curation, C.N. and D.F.-L.; writing—original draft C.N., D.F.-L. and J.B., writing—review and editing, C.N., D.F.-L. and J.B. visualization, C.N., D.F.-L. and J.B. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the US Department of Agriculture, Forest Service, grant number 19-CS-11083100-171, including 2 modifications.

Data Availability Statement

Data and appendices (with English units Metrics and Metric Ratings) are made available through the NatureServe website. https://www.natureserve.org/projects/developing-rapid-assessment-metrics-measuring-open-pine-ecosystem-health-southeastern-0 (accessed on 12 November 2021).

Acknowledgments

This publication is built on a substantial body of work for longleaf and shortleaf pine–oak ecosystems, completed by NatureServe and partners. We thank the USDA Forest Service for their support of this shortleaf pine assessment method. We also appreciate the peer review comments received from researchers and land managers throughout the Southeast and southern Appalachian regions, as documented by Nordman et al. (2021). In particular, the scientists of the Forest Service, Southern Research Station and scientists at Land-Grant Universities have helped greatly improve our understanding of these open pine–oak ecosystems. We also thank the South Atlantic Landscape Conservation Cooperative, an affiliate of the US Fish and Wildlife Service and other conservation partners, in supporting open pine assessments in the region. NatureServe is a network-based organization, and our strength in the US comes from the Natural Heritage Programs, many of whom have worked with NatureServe to advance these ecological integrity assessment methods. We would also like to thank the reviewers who provided feedback on the earlier versions of this manuscript. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the US Government. USDA is an equal opportunity provider, employer, and lender.

Conflicts of Interest

The authors declare no conflict of interest.

Appendix A. Priority Wildlife Species

Table A1. Representative wildlife species of shortleaf pine–oak and Appalachian pine–oak ecosystems Focal and rare taxa are in bold. For each taxon, the NatureServe Global Rank (GRank) is provided (G1 = Critically Imperiled, G2 = Imperiled, G3 = Vulnerable, G4 = Apparently Secure, and G5 = Secure). Subspecies ranks are shown as T ranks (e.g., G5T1). The Endangered Species Act (ESA) listing includes EN = Endangered, TH = Threatened.

Taxon	Scientific Name	Common Name	Nature Serve GRank	ESA Listing
Bird	Paucaea (Aimophila) aestivalis	Bachman’s sparrow	G3
Bird	Antrostomus vociferus	Whip-poor-will	G5
Bird	Bonasa umbellus	Ruffed grouse	G5
Bird	Buteo platypterus	Broad-winged hawk	G5
Bird	Antrostomus (Caprimulgus) carolinensis	Chuck-wills-widow	G5
Bird	Catharus fuscenscens	Verry	G5
Bird	Certhia ameriana	Brown creeper	G5
Bird	Chaetura pelagica	Chimney swift	G4
Bird	Colaptes auratus	Northern flicker	G5
Bird	Colinus virginianus	Northern bobwhite	G4
Bird	Contopus virens	Eastern wood-pewee	G5
Bird	Steophaga (Dendroica) dominica	Yellow-throated warbler	G5
Bird	Dryocopus pileatus	Pileated woodpecker	G5
Bird	Empidonax minimus	Least flycatcher	G5
Bird	Empidonax virescens	Acadian flycatcher	G5
Bird	Geothlypis formosa	Kentucky warbler	G5
Bird	Helmitheros vermivorum	Worm-eating warbler	G5
Bird	Hylocichla mustelina	Wood thrush	G4
Bird	Limnothlypis swainsonii	Swainson’s warbler	G4
Bird	Melanerpes erythrocephalus	Red-headed woodpecker	G5
Bird	Parkesia motacilla	Louisiana waterthrush	G5
Bird	Dryobates (Picoides) borealis	Red-cockaded woodpecker	G3	EN
Bird	Pipilo erythrophthalmus	Eastern towhee	G5
Bird	Piranga olivacea	Scarlet tanger	G5
Bird	Scologpax minor	American woodcock	G5
Bird	Selurus aurocapilla	Ovenbird	G5
Bird	Setophaga pinus	Pine warbler	G5
Bird	Setophago discolor	Prairie warbler	G5
Bird	Sitta pusilla	Brown-headed nuthatch	G4
Bird	Spizella passerine	Chipping sparrow	G5
Bird	Spizella pusilla	Field sparrow	G5
Bird	Steophaga discolor	Prairie warbler	G5
Bird	Toxostoma rufum	Brown thrasher	G5
Invertebrate	Bombus spp.	Bumblebees
Invertebrate	Danaus plexippus	Monarch butterfly	G4
Invertebrate	Nicrophorus americanus	American burying beetle	G3	EN
Invertebrate	Speyeria cybele	Great-spangled fritillary	G5
Invertebrate	Speyeria diana	Diana fritillary	G2
Mammal	Corynorhinus rafinesquii	Rafinesque’s big-eared bat	G3
Mammal	Eptesicus fuscus	Big brown bats	G5
Mammal	Lasionycteris noctivagans	Silver-haried bats	G3
Mammal	Lasiurus cinereus	Hoary bats	G3
Mammal	Lasiurus seminolus	Seminole bat	G5
Mammal	Microtus chrotorrhinus carolinensis	Southern rock vole	T3
Mammal	Myotis grisescens	Gray bat	G4	EN
Mammal	Myotis leibii	Eastern small-footed bat	G4
Mammal	Myotis lucifugus	Little brown bat	G3
Mammal	Myotis septentrionalis	Northern long-eared bat	G1	TH
Mammal	Myotis sodalis	Indiana bat	G2	EN
Mammal	Neotoma floridana haematoria	Southern Appalachian woodrat	T4
Mammal	Neotoma magister	Alleghany woodrat	G3
Mammal	Perimyotis subflavus	Tri-colored bat	G2
Mammal	Silogale putorius	Spotted skunks	G4
Mammal	Ursus americanus	Black bear	G5
Amphibian	Plethodon welleri	Weller’s salamander	G3
Reptile	Crotalus horridus	Timber rattlesnake	G4
Reptile	Elaphe guttata guttata	Corn snake	G5
Reptile	Eumeces anthracinus	Coal Skink	G5
Reptile	Heterodon platirhinos	Eastern hognose snake	G5
Reptile	Lampropeltis triangulum triangulus	Eastern milk snake	G5
Reptile	Pituophis melanloeucas	Northern pinesnake	G4
Reptile	Regina septemvittata	Queen snake	G5
Reptile	Terrapene carolina	Eastern box turtle	G5
Reptile	Virginia valeriae valeriae	Eastern earthsnake	G5

Table A2. Focal and rare species of shortleaf pine–oak and Appalachian pine–oak woodlands. SGCN = species of greatest conservation need.

Taxon	Common Name	Scientific Name	Project Area States Where it Occurs	States Where Listed as SGCN in 2015 State Wildlife Action Plan
Bird	Peucaea (Aimophila) aestivalis	Bachman’s sparrow	All project area states	AL, AR, FL, GA, KY, LA, MO, MS, NC, OK, SC, TN, TX, VA
Bird	Colinus virginianus	Northern bobwhite	All project area states	AR, DC, DE, FL, GA, IA, IL, IN, KS, KY, LA, MA, MD, MO, MS, NC, NJ, NY, OH, OK, SC, TN, TX, VA, WI, WV
Bird	Dryobates (Picoides) borealis	Red-cockaded woodpecker	All project area states, except KY, MO, TN (Extirpated)	AL, AR, FL, GA, KY (Extirpated), LA, MD, MS, NC, OK, SC, TX, VA
Invertebrate	Bombus spp.	Bumblebees	All project area states	GA, NC, VA (Bombus affinus), GA (Bombus borealis)
Invertebrate	Danaus plexippus	Monarch butterfly	All project area states	AR, CA, CO, CT, DE, GA, IA, ID, IL, KS, LA, MD, ME, MI, MN, MO, NJ, OH, OR, NC, ND, NH, PA, RI, VT, WA
Invertebrate	Nicrophorus americanus	American burying beetle	AR, OK, TX (presumed or possibly extirpated from many states)	AL, AR, CT, DE, IL, KS, MA, MO, NC, NE, NJ, OH, OK, PA, RI, SD, TN, TX, VA
Invertebrate	Speyeria diana	Diana fritillary	AL, AR, GA, KY, NC, OK, SC, TN, VA, WV	AR, GA, OH, OK, SC, TN, VA, WV
Mammal	Corynorhinus rafinesquii	Rafinesque’s big-eared bat	All project area states	AL, AR, FL, GA, IL, IN, KY, LA, MO, MS, NC, OH, OK, SC, TN, TX, WV
Mammal	Lasionycteris noctivagans	Silver-haired bats	All project area states	AK, CT, DE, IA, ID, IN, LA, MA, MD, ME, MN, MO, MS, NH, NJ, NV, NY, OH, OR, PA, RI, SD, VA, VT, WA, WV
Mammal	Lasiurus cinereus	Hoary bats	All project area states	CO, CT, DE, ID, IN, MA, MD, ME, MS, MN, MS, NH, NJ, NV, NY, OH, OR, RI, SC, VA, VT, WA, WV
Mammal	Microtus chrotorrhinus carolinensis	Southern rock vole	MD, NC, TN, VA, WV	MD, NC, TN, VA, WV (Microtus chrotorrhinus)
Mammal	Myotis grisescens	Gray bat	AL, AR, FL, GA, KS, KY, IL, IN, MO, MS (possibly extirpated), NC, OK, SC, TN, VA	AL, AR, FL, GA, KS, KY, IL, IN, MO, MS, NC, OK, TN, VA
Mammal	Myotis lucifugus	Little brown bat	All project area states, except LA, TX	AK, AL, AR, CO, CT, DE, GA, IA, ID, IN, KS, MA, MD, ME, MI, MN, NC, ND, NE, NH, NJ, NV, NY, OH, PA, RI, SC, TN, TX, UT, VA, VT, WI, WV, WY
Mammal	Myotis septentrionalis	Northern long-eared bat	All project area states, except TX	All project area states, except FL, KY, TX
Mammal	Myotis sodalis	Indiana bat	All project area states, except FL, LA, TX	All project area states, except FL, LA, SC, TX
Mammal	Neotoma magister	Alleghany woodrat	AL, IN, KY, MD, NC, NJ, NY, OH, PA, TN, VA, WV	AL, IN, KY, MD, NC, NJ, NY, OH, PA, TN, VA, WV
Mammal	Perimyotis subflavus	Tri-colored bat	All project area states	AL, CT, FL, GA, IA, IN, LA, MA, MD, ME, MI, MN, NC, NE, NH, NJ, NY, OH, OK, PA, RI, SC, TX, VA, VT, WI, WV
Amphibian	Plethodon welleri	Weller’s salamander	NC, TN, VA	NC, TN, VA

Appendix B. Metric and Metric Ratings for Each Shortleaf Pine–Oak Group and Southern Appalachian Pine–Oak Group

Here we summarize the metric ratings for each shortleaf pine–oak or Appalachian pine–oak group. Please refer to Nordman et al., 2021 for more detailed information on each of the metrics.

Table A3. Interior Highlands shortleaf pine–oak forests and woodlands.

A.1. Interior Highlands Shortleaf Pine–Oak Forests and Woodlands (Dry and Mesic Highlands Pine Woodlands)
Canopy Metrics
	Excellent	Good	Fair	Poor
1. Canopy: Southern Yellow Pine Basal Area	>8.0 to 17.2 m²/ha basal area of shortleaf pine	6.9 to 8.0 or >17.2 to 20.7 m²/ha basal area of shortleaf pine	2.3 to <6.9 or >20.7 to 25.3 m²/ha basal area of shortleaf pine	<2.3 or >25.3 m²/ha basal area of shortleaf pine
2. Southern Yellow Pine Canopy Cover	>25% to 70% canopy cover of shortleaf pine	20%–25% or >70% to 80% canopy cover of shortleaf pine	10% to <20% or >80 to 90% canopy cover of shortleaf pine	<10% or >90% canopy cover of shortleaf pine
3. Southern Yellow Pine Stand Size Structure	Basal area ≥ 4.6 m²/ha of shortleaf pine trees > 35 cm DBH class	Basal area ≥ 2.3–4.6 m²/ha of shortleaf pine trees > 35 cm DBH class	Shortleaf pine trees > 35 cm DBH class are present, but < 2.3 m²/ha basal area of those large trees	No shortleaf pine trees > 35 cm DBH are present
4. Canopy: Fire-Tolerant Hardwood Basal Area	≤11.5 m²/ha BA of fire-tolerant hardwood trees	>11.5 to 13.8 m²/ha BA of fire-tolerant hardwood trees	>13.8 to 16.1 m²/ha BA of fire-tolerant hardwood trees	>16.1 m²/ha BA of fire- tolerant hardwood trees
5. Canopy: Fire-Intolerant Tree Basal Area	≤2.3 m²/ha BA of fire-intolerant trees	>2.3 to 4.6 m²/ha BA of fire-intolerant trees	>4.6 to 6.9 m²/ha BA of fire-intolerant trees	>6.9 m²/ha BA of fire-intolerant trees
6. Stand Density Index (applies to shortleaf pine) (optional)	SDI = 65–135 (14%–30% of maximum SDI of 450)	SDI = 45–65 or 135–180 (10%–14% or 30%–40% of maximum SDI of 450)	SDI = 20–45 or 180–225 (4%–10% or 40%–50% of maximum SDI of 450)	SDI < 20 or >225 (<4% or >50%, 270 is 60% of maximum SD of 450)
Midstory/Shrub Metrics
	Excellent	Good	Fair	Poor
1. Midstory: Fire-Tolerant Hardwood Cover	2% to <20% cover of midstory fire- tolerant hardwoods	20% to 40% cover of midstory fire-tolerant hardwoods	>40% to 50%, or <2% cover of midstory fire- tolerant hardwoods	>50% cover of midstory fire-tolerant hardwoods
2. Midstory: Fire-Intolerant Tree Cover	<10% cover of fire-intolerant tree midstory	10% to 20% cover of fire-intolerant tree midstory	>20% to 30% cover of fire-intolerant tree midstory	>30% cover of fire-intolerant tree midstory
3. Tall Shrub (3–10 ft tall) Cover	Tall shrubs average < 30% cover	Tall shrubs average 30%–40% cover	Tall shrubs average > 40% to 50% cover	Tall shrubs average > 50% cover
4. Short Shrub (<3 ft tall) Cover	Short shrubs average < 20% cover	Short shrubs average 20%–30% cover	Short shrubs average > 30% to 45% cover	Short shrubs average > 45% cover
Ground Layer Metrics
	Excellent	Good	Fair	Poor
1. Overall Native Herbaceous Ground Cover	35%–80% herbaceous cover	20% to <35% or >80% herbaceous cover	10% to <20% herbaceous cover	<10% herbaceous cover
2. Native Graminoid Cover	>25% to 85% cover of all native graminoids	>20% to 25% or >85% cover of native graminoids	10%–20% cover of all native graminoids	<10% cover of all native graminoids
3. Floristic Quality Index, Mean C (Optional)	Mean C > 4.00	Mean C is 3.01 to 4.00	Mean C is 2.01 to 3.00	Mean C < 2.00
4. Invasive Plant Presence/Distribution	Invasive nonnative plant species absent	Invasive nonnative plant species present in any stratum but sporadic (<1% cover)	Invasive nonnative plant species uncommon in any stratum (1%–5% cover)	Invasive nonnative plant species common in any stratum (>5% cover)
Soil Metric
1. Forest Soil Disturbance	Soil Disturbance Class 0	Soil Disturbance Class 1	Soil Disturbance Class 2	Soil Disturbance Class 3

Table A4. Interior Highlands shortleaf pine–bluestem woodlands.

A.2.Interior Highlands Shortleaf Pine–Bluestem Woodlands (Dry and Mesic Highlands Pine Woodlands)
Canopy Metrics
	Excellent	Good	Fair	Poor
1. Canopy: Southern Yellow Pine Basal Area	>8.0 to 17.2 m²/ha basal area of shortleaf pine	6.9 to 8.0 or >17.2 to 20.7 m²/ha basal area of shortleaf pine	2.3 to <6.9 or >20.7 to 25.3 m²/ha basal area of shortleaf pine	<2.3 or >25.3 m²/ha basal area of shortleaf pine
2. Southern Yellow Pine Canopy Cover	>25% to 70% canopy cover of shortleaf pine	20%–25% or >70% to 80% canopy cover of shortleaf pine	10% to <20% or >80% to 90% canopy cover of shortleaf pine	<10% or >90% canopy cover of shortleaf pine
3. Southern Yellow Pine Stand Size Structure	Basal area ≥ 4.6 m²/ha of shortleaf pine trees > 35 cm DBH class	Basal area ≥ 2.3–4.6 m²/ha of shortleaf pine trees > 35 cm DBH class	Shortleaf pine trees > 35 cm DBH class are present, but < 2.3 m²/ha basal area of those large trees	No shortleaf pine trees > 35 cm DBH are present
4. Canopy: Fire-Tolerant Hardwood Basal Area	≤4.6 m²/ha BA of fire-tolerant hardwood trees	>4.6 to 6.9 m²/ha BA of fire-tolerant hardwood trees	>6.9 to 9.2 m²/ha BA of fire-tolerant hardwood trees	>9.2 m²/ha BA of fire- tolerant hardwood trees
5. Canopy: Fire-Intolerant Tree Basal Area	≤2.3 m²/ha BA of fire-intolerant trees	>2.3 to 4.6 m²/ha BA of fire-intolerant trees	>4.6 to 6.9 m²/ha BA of fire-intolerant trees	>6.9 m²/ha BA of fire-intolerant trees
6. Stand Density Index (applies to shortleaf pine) (optional)	SDI = 65–135 (14%–30% of maximum SDI of 450)	SDI = 45–65 or 135–180 (10%–14% or 30%–40% of maximum SDI of 450)	SDI = 20–45 or 180–225 (4%–10% or 40%–50% of maximum SDI of 450)	SDI < 20 or >225 (<4% or >50%, 270 is 60% of maximum SD of 450)
Midstory/Shrub Metrics
	Excellent	Good	Fair	Poor
1. Midstory: Fire-Tolerant Hardwood Cover	2% to <10% cover of midstory fire-tolerant hardwoods	10%–30%, or <2% cover of midstory fire- tolerant hardwoods	>30% to 40% cover of midstory fire-tolerant hardwoods	>40% cover of midstory fire-tolerant hardwoods
2. Midstory: Fire-Intolerant Tree Cover	<5% cover of fire-intolerant tree midstory	5%–10% cover of fire-intolerant tree midstory	>10% to 20% cover of fire-intolerant tree midstory	>20% cover of fire-intolerant tree midstory
3. Tall Shrub (3–10 ft tall) Cover	Tall shrubs average < 5% cover.	Tall shrubs average 5%–10% cover.	Tall shrubs average > 10% to 25% cover.	Tall shrubs average > 25% cover.
4. Short Shrub (< 3 ft tall) Cover	Short shrubs average < 20% cover	Short shrubs average 20%–25% cover	Short shrubs average > 25% to 40% cover	Short shrubs average > 40% cover
Ground Layer Metrics
	Excellent	Good	Fair	Poor
1. Overall Native Herbaceous Ground Cover	>45% to 80% herbaceous cover	30%–45% or >80% herbaceous cover	15% to <30% herbaceous cover	<15% herbaceous cover
2. Native Graminoid Cover	>25% to 85% cover of all native graminoids	20% to 25% or >85% cover of native graminoids	10% to <20% cover of all native graminoids	<10% cover of all native graminoids
3. Floristic Quality Index, Mean C (Optional)	Mean C > 4.00	Mean C is 3.01 to 4.00	Mean C is 2.01 to 3.00	Mean C < 2.00
4. Invasive Plant Presence/Distribution	Invasive non-native plant species absent	Invasive non-native plant species present in any stratum but sporadic (<1% cover)	Invasive non-native plant species uncommon in any stratum (1%–5% cover)	Invasive non-native plant species common in any stratum (>5% cover)
Soil Metric
1. Forest Soil Disturbance	Soil Disturbance Class 0	Soil Disturbance Class 1	Soil Disturbance Class 2	Soil Disturbance Class 3

Table A5. Montane longleaf pine–shortleaf pine woodlands.

B. Montane Longleaf Pine–Shortleaf Pine Woodlands
Canopy Metrics
	Excellent	Good	Fair	Poor
1. Canopy: Southern Yellow Pine Basal Area	>8.0 to 17.2 m²/ha basal area of longleaf and/or shortleaf pine	6.9 to 8.0 or >17.2 to 20.7 m²/ha basal area of longleaf and/or shortleaf pine	2.3 to <6.9 or >20.7 to 25.3 m²/ha basal area of longleaf and/or shortleaf pine	<2.3 or >25.3 m²/ha basal area of longleaf and/or shortleaf pine
2. Southern Yellow Pine Canopy Cover	>25% to 70% canopy cover of longleaf and/or shortleaf pine	20%–25% or >70% to 80% canopy cover of longleaf and/or shortleaf pine	10% to <20% or >80% to 90% canopy cover of longleaf and/or shortleaf pine	<10% or >90% canopy cover of longleaf and/or shortleaf pine
3. Southern Yellow Pine Stand Size Structure	Basal area ≥ 4.6 m²/ha of longleaf pine and/or shortleaf pine trees > 35 cm DBH class or flat-top longleaf pine is present	BA ≥ 2.3–4.6 m²/ha of longleaf and/or shortleaf pine trees > 35 cm DBH class. No flat-top longleaf pine is present.	Longleaf and/or shortleaf pine trees > 35 cm DBH class are present, but at <2.3 m²/ha BA. No flat-top longleaf pine is present.	No longleaf and/or shortleaf pine trees > 35 cm DBH, nor is flat-top longleaf pine present
4. Canopy: Fire-Tolerant Hardwood Basal Area	≤4.6 m²/ha BA of fire- tolerant hardwood trees	>4.6 to 9.2 m²/ha BA of fire-tolerant hardwood trees	>9.2 to 11.5 m²/ha BA of fire-tolerant hardwood trees	>11.5 m²/ha BA of fire- tolerant hardwood trees
5. Canopy Fire- Intolerant Tree Basal Area	≤2.3 m²/ha BA of fire-intolerant trees	>2.3 to 4.6 m²/ha BA of fire-intolerant trees	>4.6 to 6.9 m²/ha BA of fire-intolerant trees	>6.9 m²/ha BA of fire-intolerant trees
6. Stand Density Index (applies to longleaf pine) (optional)	SDI = 55–120 (14%–30% of maximum SDI of 400)	SDI = 40–55 or 120–160 (10%–14% or 30%–40% of maximum SDI of 400)	SDI = 15–40 or 160–200 (4%–10% or 40%–50% of maximum SDI)	SDI < 15 or >200 (<4% or >50%, 240 is 60% of maximum SD of 400)
Midstory/Shrub Metrics
	Excellent	Good	Fair	Poor
1. Midstory: Fire-Tolerant Hardwood Cover	2% to <10% cover of midstory fire-tolerant hardwoods	10%–30%, or <2% cover of midstory fire-tolerant hardwoods	>30% to 40% cover of midstory fire-tolerant hardwoods	>40% cover of midstory fire-tolerant hardwoods
2. Midstory: Fire-Intolerant Tree Cover	<5% cover of fire-intolerant tree midstory	5% to 10% cover of fire-intolerant tree midstory	>10% to 20% cover of fire-intolerant tree midstory	>20% cover of fire-intolerant tree midstory
3. Tall Shrub (3–10 ft tall) Cover	Tall shrubs average < 15% cover.	Tall shrubs average 15%–20% cover.	Tall shrubs average > 20% to 30% cover.	Tall shrubs average > 30% cover.
4. Short Shrub (<3 ft tall) Cover	Short shrubs average < 20% cover	Short shrubs average 20%–25% cover	Short shrubs average > 25% to 40% cover	Short shrubs average > 40% cover
Ground Layer Metrics
	Excellent	Good	Fair	Poor
1. Overall Native Herbaceous Ground Cover	>45% to 80% herbaceous cover	30%–45% or >80% herbaceous cover	15% to <30% herbaceous cover	<15% herbaceous cover
2. Native Graminoid Cover	>25% to 85% cover of all native graminoids	20%–25% or >85% cover of all native graminoids	10% to <20% cover of all native graminoids	<10% cover of all native graminoids
3. Floristic Quality Index, Mean C (Optional)	Mean C > 4.00	Mean C is 3.01 to 4.00	Mean C is 2.01 to 3.00	Mean C < 2.00
4. Invasive Plant Presence/Distribution	Invasive non-native plant species absent	Invasive nonnative plant species present in any stratum but sporadic (<1% cover)	Invasive nonnative plant species uncommon in any stratum (1%–5% cover)	Invasive nonnative plant species common in any stratum (>5% cover)
Soil Metric
1. Forest Soil Disturbance	Soil Disturbance Class 0	Soil Disturbance Class 1	Soil Disturbance Class 2	Soil Disturbance Class 3

Table A6. Southern Appalachian pine–oak woodlands.

C. Southern Appalachian Pine–Oak Woodlands
Canopy Metrics
	Excellent	Good	Fair	Poor
1. Canopy: Southern Yellow Pine Basal Area	>8.0 to 17.2 m²/ha basal area of pitch pine, Table Mountain pine and/or shortleaf pine	4.6 to 8.0 or >17.2 to 20.7 m²/ha basal area of pitch pine, Table Mountain pine and/or shortleaf pine	2.3 to <4.6 or >20.7 to 25.3 m²/ha basal area of pitch pine, Table Mountain pine and/or shortleaf pine	<2.3 or >25.3 m²/ha basal area of pitch pine, Table Mountain pine and/or shortleaf pine
2. Southern Yellow Pine Canopy Cover	>25% to 70% canopy cover of pitch pine, Table Mountain pine and/or shortleaf pine	20%–25% or >70% to 80% canopy cover of pitch pine, Table Mountain pine and/or shortleaf pine	10% to <20% or >80% to 90% canopy cover of pitch pine, Table Mountain pine and/or shortleaf pine	<10% or >90% canopy cover of pitch pine, Table Mountain pine and/or shortleaf pine
3. Southern Yellow Pine Stand Size Structure	BA ≥ 4.6 m²/ha of pitch pine, Table Mountain pine and/or shortleaf pines > 30 cm DBH class	BA ≥ 2.3–4.6 m²/ha of pitch pine, Table Mountain pine and/or shortleaf pines > 30 cm DBH class	Pitch pine, Table Mountain pine and/or shortleaf pines > 30 cm DBH class are present, but at < 2.3 m²/ha BA	No pitch pine, Table Mountain pine or shortleaf pines > 30 cm DBH
4. Canopy: Fire-Tolerant Hardwood Basal Area	<4.6 m²/ha BA of fire-tolerant hardwood trees	>4.6 to 6.9 m²/ha BA of fire-tolerant hardwood trees	>6.9 to 9.2 m²/ha BA of fire-tolerant hardwood trees	>9.2 m²/ha BA of fire-tolerant hardwood trees
5. Canopy: Fire-Intolerant Tree Basal Area	≤2.3 m²/ha BA of fire-intolerant trees	>2.3 to 4.6 m²/ha BA of fire-intolerant trees	>4.6 to 6.9 m²/ha BA of fire-intolerant trees	>6.9 m²/ha BA of fire-intolerant trees
Midstory/Shrub Metrics
	Excellent	Good	Fair	Poor
1. Midstory: Fire-Tolerant Hardwood Cover	2% to <10% cover of midstory fire-tolerant hardwoods	10%–30%, or <2% cover of midstory fire-tolerant hardwoods	>30% to 40% cover of midstory fire-tolerant hardwoods	>40% cover of midstory fire-tolerant hardwoods
2. Midstory: Fire-Intolerant Tree Cover	<10% cover of fire-intolerant tree midstory	10% to 20% cover of fire-intolerant tree midstory	>20% to 30% cover of fire-intolerant tree midstory	>30% cover of fire-intolerant tree midstory
3. Tall Shrub (3–10 ft tall) Cover	Tall shrubs average < 15% cover.	Tall shrubs average 15%–20% cover.	Tall shrubs average > 20% to 30% cover.	Tall shrubs average > 30% cover.
4. Short Shrub (<3 ft tall) Cover	Short shrubs average < 50% cover	Short shrubs average 50%–70% cover	Short shrubs average > 70% to 80% cover	Short shrubs average > 80% cover
Ground Layer Metrics
	Excellent	Good	Fair	Poor
1. Overall Native Herbaceous Ground Cover	>15% herbaceous cover	5 to 15% herbaceous cover	<5% herbaceous cover	Herbaceous cover absent
2. Native Graminoid Cover	>10% cover of all native graminoids	5% to 10% cover of all native graminoids	Native graminoids present, but with < 5% cover	Native graminoids absent
3. Floristic Quality Index, Mean C (Optional)	Mean C > 4.00	Mean C is 3.01 to 4.00	Mean C is 2.01 to 3.00	Mean C < 2.00
4. Invasive Plant Presence/Distribution	Invasive non-native plant species absent	Invasive non-native plant species present in any stratum but sporadic (<1% cover)	Invasive non-native plant species uncommon in any stratum (1%–5% cover)	Invasive non-native plant species common in any stratum (>5% cover)
Soil Metric
1. Forest Soil Disturbance	Soil Disturbance Class 0	Soil Disturbance Class 1	Soil Disturbance Class 2	Soil Disturbance Class 3

Table A7. West Gulf coastal plain shortleaf pine–oak woodlands.

D. West Gulf Coastal Plain Shortleaf Pine–Oak Woodlands (Dry and Mesic Hilly Pine Woodlands)
Canopy Metrics
	Excellent	Good	Fair	Poor
1. Canopy: Southern Yellow Pine Basal Area	6.9–19.5 m²/ha basal area of shortleaf, loblolly, and/or longleaf pine	4.6 to <6.9 or >19.5 to 23.0 m²/ha basal area of shortleaf, loblolly, and/or longleaf pine	2.3 to <4.6 or >23.0 to 26.4 m²/ha basal area of shortleaf, loblolly, and/or longleaf pine	<2.3 or >26.4 m²/ha basal area of shortleaf, loblolly, and/or longleaf pine
2. Southern Yellow Pine Canopy Cover	>25% to 75% canopy cover of shortleaf, loblolly, and/or longleaf pine	>15% to 25% canopy cover or >75% to 85% canopy cover of shortleaf, loblolly, and/or longleaf pine	10%–15% canopy cover or >85 to 95% canopy cover of shortleaf, loblolly, and/or longleaf pine	<10% cover or >95% cover of shortleaf, loblolly, and/or longleaf pine
3. Southern Yellow Pine Stand Size Structure	BA ≥ 4.6 m²/ha of shortleaf, loblolly, and/or longleaf pine trees > 35 cm DBH class	BA ≥ 2.3–4.6 m²/ha of shortleaf, loblolly, and/or longleaf pine trees > 35 cm DBH class	Shortleaf, loblolly, and/or longleaf pine trees > 35 cm DBH class are present, but < 2.3 m²/ha basal area of those large trees	No shortleaf, longleaf, or loblolly pine trees > 35 cm DBH are present
4. Canopy: Fire-Tolerant Hardwood Basal Area	<4.6 m²/ha BA of fire-tolerant hardwood trees	>4.6 to 6.9 m²/ha BA of fire-tolerant hardwood trees	>6.9 to 9.2 m²/ha BA of fire-tolerant hardwood trees	>9.2 m²/ha BA of fire-tolerant hardwood trees
5. Canopy: Fire- Intolerant Tree Basal Area	≤2.3 m²/ha BA of fire-intolerant trees	>2.3 to 4.6 m²/ha BA of fire-intolerant trees	>4.6 to 6.9 m²/ha BA of fire-intolerant trees	>6.9 m²/ha BA of fire-intolerant trees
6. Stand Density Index (applies to shortleaf and loblolly pine) (optional)	SDI = 55–155 (12%–34% of maximum SDI of 450)	SDI = 35–55 or 155–205 (8%–12% or 34%–45% of maximum SDI of 450)	SDI = 20–35 or 205–225 (4%–8% or 45%–50% of maximum SDI of 450)	SDI < 20 or >225 (<4% or >50%, 270 is 60% of maximum SD of 450)
Midstory/Shrub Metrics
	Excellent	Good	Fair	Poor
1. Midstory: Fire-Tolerant Hardwood Cover	2% to <10% cover of midstory fire-tolerant hardwoods	10%–20%, or <2% cover of midstory fire- tolerant hardwoods	>20% to 35% cover of midstory fire-tolerant hardwoods	>35% cover of midstory fire-tolerant hardwoods
2. Midstory: Fire- Intolerant Tree Cover	<10% cover of fire-intolerant tree midstory	10% to 20% cover of fire-intolerant tree midstory	>20% to 30% cover of fire-intolerant tree midstory	>30% cover of fire-intolerant tree midstory
3. Tall Shrub (3–10 ft tall) Cover	Tall shrubs average < 15% cover.	Tall shrubs average 15% to 20% cover.	Tall shrubs average > 20% to 30% cover.	Tall shrubs average > 30% cover.
4. Short Shrub (<3 ft tall) Cover	Short shrubs average < 20% cover	Short shrubs average 20%–30% cover	Short shrubs average > 30% to 45% cover	Short shrubs average > 45% cover
Ground Layer Metrics
	Excellent	Good	Fair	Poor
1. Overall Native Herbaceous Ground Cover	35%–80% herbaceous cover	20% to <35% or >80% herbaceous cover	10% to <20% herbaceous cover	<10% herbaceous cover
2. Native Graminoid Cover	25%–100% cover of all native graminoids	>15% to <25% cover of all native graminoids	10%–15% cover of all native graminoids	<10% cover of all native graminoids
3. Floristic Quality Index, Mean C (Optional)	Mean C > 4.00	Mean C is 3.01 to 4.00	Mean C is 2.01 to 3.00	Mean C < 2.00
4. Invasive Plant Presence/Distribution	Invasive nonnative plant species absent	Invasive nonnative plant species in any stratum present but sporadic (<1% cover)	Invasive nonnative plant species uncommon in any stratum (1%–5% cover)	Invasive nonnative plant species common in any stratum (>5% cover)
Soil Metric
1. Forest Soil Disturbance	Soil Disturbance Class 0	Soil Disturbance Class 1	Soil Disturbance Class 2	Soil Disturbance Class 3

Table A8. Southeastern coastal plain and Piedmont shortleaf pine–oak woodlands.

E. Southeastern Coastal Plain and Piedmont Shortleaf Pine–Oak Woodlands (Dry and Mesic Hilly Pine Woodlands)
Canopy Metrics
	Excellent	Good	Fair	Poor
1. Canopy: Southern Yellow Pine Basal Area	6.9–19.5 m²/ha basal area of shortleaf and/or longleaf pine	4.6 to <6.9 or >19.5 to 23.0 m²/ha basal area of shortleaf and/or longleaf pine	2.3 to <4.6 or >23.0 to 26.4 m²/ha basal area of shortleaf and/or longleaf pine	<2.3 or >26.4 m²/ha basal area of shortleaf and/or longleaf pine
2. Southern Yellow Pine Canopy Cover	>25% to 75% canopy cover of shortleaf and/or longleaf pine	>15% to 25% canopy cover or >75% to 85% canopy cover of shortleaf and/or longleaf pine	10%–15% canopy cover or > 85% to 95% canopy cover of shortleaf and/or longleaf pine	<10% cover or >95% cover of shortleaf and/or longleaf pine
3. Southern Yellow Pine Stand Size Structure	BA ≥ 4.6 m²/ha of shortleaf and/or longleaf pine trees > 35 cm DBH class	BA ≥ 2.3–4.6 m²/ha of shortleaf and/or longleaf pine trees > 35 cm DBH class	Shortleaf and/or longleaf pine trees > 35 cm DBH class are present, but < 2.3 m²/ha basal area of those large trees	No shortleaf or longleaf pine trees > 35 cm DBH are present
4. Canopy: Fire-Tolerant Hardwood Basal Area	<4.6 m²/ha BA of fire-tolerant hardwood trees	>4.6 to 6.9 m²/ha BA of fire-tolerant hardwood trees	>6.9 to 9.2 m²/ha BA of fire-tolerant hardwood trees	>9.2 m²/ha BA of fire-tolerant hardwood trees
5. Canopy: Fire- Intolerant Tree Basal Area	≤2.3 m²/ha BA of fire-intolerant trees	>2.3 to 4.6 m²/ha BA of fire-intolerant trees	>4.6 to 6.9 m²/ha BA of fire-intolerant trees	>6.9 m²/ha BA of fire-intolerant trees
6. Stand Density Index (applies to shortleaf pine) (optional)	SDI = 55–155 (12–34% of maximum SDI of 450)	SDI = 35–55 or 155–205 (8%–12% or 34%–45% of maximum SDI of 450)	SDI = 20–35 or 205–225 (4%–8% or 45%–50% of maximum SDI of 450)	SDI < 20 or >225 (< 4% or >50%, 270 is 60% of maximum SD of 450)
Midstory/Shrub Metrics
	Excellent	Good	Fair	Poor
1. Midstory: Fire-Tolerant Hardwood Cover	2% to <10% cover of midstory fire- tolerant hardwoods	10%–20%, or <2% cover of midstory fire- tolerant hardwoods	>20% to 35% cover of midstory fire-tolerant hardwoods	>35% cover of midstory fire-tolerant hardwoods
2. Midstory: Fire- Intolerant Tree Cover	<10% cover of fire-intolerant tree midstory	10% to 20% cover of fire-intolerant tree midstory	>20% to 30% cover of fire-intolerant tree midstory	>30% cover of fire-intolerant tree midstory
3. Tall Shrub (3–10 ft tall) Cover	Tall shrubs average < 15% cover.	Tall shrubs average 15% to 20% cover.	Tall shrubs average > 20% to 30% cover.	Tall shrubs average > 30% cover.
4. Short Shrub (<3 ft tall) Cover	Short shrubs average < 20% cover	Short shrubs average 20%–30% cover	Short shrubs average > 30% to 45% cover	Short shrubs average > 45% cover
Ground Layer Metrics
	Excellent	Good	Fair	Poor
1. Overall Native Herbaceous Ground Cover	35%–80% herbaceous cover	20% to <35% or >80% herbaceous cover	10% to <20% herbaceous cover	<10% herbaceous cover
2. Native Graminoid Cover	25%–100% cover of all native graminoids	>15% to <25% cover of all native graminoids	10%–15% cover of all native graminoids	< 10% cover of all native graminoids
3. Floristic Quality Index, Mean C (Optional)	Mean C > 4.00	Mean C is 3.01 to 4.00	Mean C is 2.01 to 3.00	Mean C < 2.00
4. Invasive Plant Presence/Distribution	Invasive nonnative plant species absent	Invasive nonnative plant species in any stratum present but sporadic (<1% cover)	Invasive nonnative plant species uncommon in any stratum (1%–5% cover)	Invasive nonnative plant species common in any stratum (>5% cover)
Soil Metric
1. Forest Soil Disturbance	Soil Disturbance Class 0	Soil Disturbance Class 1	Soil Disturbance Class 2	Soil Disturbance Class 3

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Figure 1. Geographic distribution map of the five major shortleaf pine–oak and Southern Appalachian pine–oak groups (A–E, colored outlines), the National Forest units (brown outlines), and Level III Ecoregions of North America (in greens, labels in black italics). The Interior Highlands shortleaf pine–oak ecosystem (A) is classified into two groups: A.1—Interior Highlands shortleaf pine–oak forest and woodlands; A.2—Interior Highlands shortleaf pine–bluestem woodland. These two groups occur within the same region and separate locally, based on topographic position, substrate, and disturbance history.

Figure 2. Conceptual model diagram of pine–hardwood population dynamics and model components. Reprinted with permission from Ref. [40]. Copyright 2011 the longleaf pine model of Loudermilk et al. Reprinted with permission from Ref. [41]. Copyright 2021 Elsevier. Copyright 2018 Hanberry et al.

Figure 3. Photos: (top left) virgin shortleaf pine (10/29/1924), Irons Fork, Oden Ranger District, Ouachita, NF (notice the man standing to the left) #FHS2303. (top right) Thinned 75-year-old shortleaf pines (10/1/1937) on an old field site in Union County, Arkansas #FHS2323. (lower left) Appalachian oak–pine woodland. (lower right) Interior Highlands shortleaf pine–bluestem woodlands after growing-season burn, Cold Springs–Poteau Ranger District, Ouachita, NF. Photos used with permission, courtesy of the Forest History Society, Durham, NC (top left, top right), Gary P. Fleming, Virginia DCR-DNH, © DCR-DNH, Gary P. Fleming (lower left), Clay Van Horn, USDA Forest Service, Ouachita NF, a public domain image (lower right). Reprinted with permission from Ref. [42]. Copyright 2021 NatureServe and the USDA Forest Service.

Table 1. Shortleaf Pine–Oak and Southern Appalachian Pine–Oak groups. The first column shows the project name for the groups; the second and third columns provide the official code and name for each equivalent USNVC group and alliance type [25].

Southern Open Pine Groups	USNVC Group Name	USNVC Alliance Name
A. Interior Highlands Shortleaf Pine–Oak A.1 Interior Highlands Shortleaf Pine–Oak Forest and Woodlands	Interior Highlands Pine–Oak Forest and Woodland (G012a)	Ozark–Ouachita Shortleaf Pine–Oak Forest—Woodland (A2083)
A.2 Interior Highlands Shortleaf Pine–Bluestem Woodland	Interior Highlands Pine–Oak Forest and Woodland (G012a)	Ozark–Ouachita Shortleaf Pine–Bluestem Woodland (A2082)
B. Montane Longleaf Pine–Shortleaf Pine Woodlands	Interior Highlands Pine–Oak Forest and Woodland (G012c)	Montane Longleaf Pine–Shortleaf Pine Woodland (A3272)
C. Southern Appalachian Pine–Oak Woodlands	Southern Appalachian Virginia Pine–Table Mountain Pine Woodland (G905)	Appalachian Table Mountain Pine–Pitch Pine–Chestnut Oak Woodland (A0677)
C. Southern Appalachian Pine–Oak Woodlands		Appalachian Shortleaf Pine–Oak Woodland (A3269)
D. West Gulf Coastal Plain Pine–Oak Woodlands	Western Gulf Coastal Plain Pine–Oak Forest and Woodland (G013)	West Gulf Coastal Plain Scrub Oak–Shortleaf Pine Sandhill Woodland (A0386)
		West Gulf Coastal Plain Shortleaf Pine–Post Oak Forest (A3129)
		West Gulf Coastal Plain Loblolly Pine–White Oak Forest (A3130)
E. Southeast Coastal Plain and Piedmont Shortleaf Pine–Oak Woodlands	Interior Highlands Oak–Pine Forest and Woodland (G012b)	Upper Coastal Plain Shortleaf Pine–Oak Woodland (A3270)
	Piedmont–Coastal Plain Oak–(Pine) Forest and Woodland (G165)	Piedmont Post Oak–Hickory–Pine Woodland (A3294)

Table 2. Example of metric and assessment points. The metric and ratings for VMID1: Midstory Fire-Tolerant Hardwood Cover, as developed for the Southern Appalachian pine–oak group, allows for a greater proportion of fire-tolerant oaks under natural conditions than for the southeast group.

Metric Rating	Southeast Coastal Plain and Piedmont Shortleaf Pine–Oak Woodlands	Southern Appalachian Pine–Oak Woodlands
EXCELLENT (A)	2% to <10% cover of midstory fire-tolerant hardwoods	2% to <10% cover of midstory fire-tolerant hardwoods
GOOD (B)	10% to <20% cover of midstory fire-tolerant hardwoods	10% to <30% cover of midstory fire-tolerant hardwoods
FAIR (C)	20% to 35% cover of midstory fire-tolerant hardwoods	30% to 40% cover of midstory fire-tolerant hardwoods
POOR (D)	>35% cover of midstory fire-tolerant hardwoods	>40% cover of midstory fire-tolerant hardwoods

Table 3. Ecological integrity metrics to assess the shortleaf pine–oak and Appalachian pine–oak groups. Fifteen stand metrics are provided, two being optional, for the canopy, midstory and shrub, herbaceous cover, and soil.

Metric	Metric Definition	Metric Measures	# of Variants
CANOPY METRICS	Canopy trees, defined as any tree that has 5” diameter at breast height (DBH) or greater.
VCAN1. Canopy: Southern Yellow Pine Basal Area	Combined basal area in m²/ha of trees, 12.7 cm in DBH or greater, that are southern yellow pine species appropriate to the Southern Open Pine Group (broad ecosystems used in this document).	x m²/ha basal area of y pine	2
VCAN2. Southern Yellow Pine Canopy Cover	Percentage of the ground within the plot covered by the general extent of southern yellow pine canopy trees, as determined via a visual (ocular) estimate. Southern yellow pine canopy is defined as showing canopy trees primarily of shortleaf pine, or with mixed loblolly pine or (mountain) longleaf pine, with stems 12.7 cm in diameter or greater at 1.37 m, diameter at breast height (DBH).	x% canopy cover of y pine	2
VCAN3. Southern Yellow Pine Stand Size Structure	Southern yellow pine, especially shortleaf pine size structure, including the presence of large (greater than or equal to 35.6 cm DBH (30.5 cm for southern Appalachian pine–oak) southern yellow pines, characteristic of the assessed ecosystem.	Basal area ≥ x m²/ha of y pine trees ≥ z” DBH class	3
VCAN4. Canopy: Fire-Tolerant Hardwood Basal Area	Combined basal area (m²/ha) of all fire-tolerant canopy hardwood trees > 12.7 cm DBH.	x to y m²/ha BA of fire-tolerant hardwood trees	4
VCAN5. Canopy: Fire-Intolerant Tree Basal Area	Combined basal area (m²/ha of all fire-intolerant canopy hardwood and conifer trees > 12.7 cm DBH.	x to y m²/ha BA of fire-intolerant trees	1
VCAN6. Stand Density Index	An index of tree density that incorporates the size (quadratic mean diameter) and density (trees per acre) of trees in a stand.	SDI = x–y (x%–y% of maximum SDI of z)	3
MIDSTORY/SHRUB METRICS	Midstory is any fire-intolerant woody stem (including tall shrubs, trees, and woody vines) that is greater than 3.0 m tall, up to the height of the bottom of the tree canopy. Shrubs are woody stems < 3.0 m tall.
VMID1. Midstory: Fire-Tolerant Hardwood Cover	Percentage of the ground within the plot or assessment area covered by fire-tolerant hardwood tree midstory foliage, branches, and stems as determined by ocular (visual) estimate.	x% to y% cover of midstory fire-tolerant hardwoods	3
VMID2. Midstory: Fire-Intolerant Tree Cover	Percentage of the ground within the plot or assessment area covered by fire-intolerant hardwood and conifer tree midstory foliage, branches, and stems as determined by ocular (visual) estimate.	x% to y% cover of fire-intolerant hardwood midstory	2
VSHR1. Tall Shrub (0.9–3.0 m tall) Cover	An assessment of amount of cover of tall shrubs (0.9–3.0 m tall) and small broad-leaved trees less than 3.0 m tall.	Tall shrubs average x% to y% cover	3
VSHR2. Short Shrub (<0.9 m tall) Cover	An assessment of amount of cover of short shrubs (<0.9 m tall).	Short shrubs, average x%–y% cover	3
GROUND LAYER METRICS	Ground layer consisting of all herbaceous (non-woody) species.
VGRD1. Overall Native Herbaceous Ground Cover	Percentage cover of all (native) herbaceous species in the ground layer.	x% to y% herbaceous cover	3
VGRD2. Native Graminoid Cover	Percentage cover of all native graminoid cover in the ground layer. Native graminoids include grasses and grass-like plants (grasses, sedges, and rushes, including beaked rushes).	x% to y% cover of all native graminoids	3
VGRD3. Floristic Quality Index, Mean C (optional)	The Floristic Quality Index is based on the plant species that are present in an assessment area, and their coefficients of conservatism, or C-values. Each species has a C-value, which is an integer from 0 to 10 assigned by botanical experts. High C-values indicate a native plant’s fidelity to natural areas with natural processes. Low C-values indicate weedy plants that commonly occur in ruderal habitats, such as old fields or vacant lots. The integer 0 is typically reserved for exotics.	Mean C x to y	1
VGRD4. Invasive Plant Presence/Distribution	Percentage cover of all invasive species in all layers.	Invasive non-native plant species, x% to y% cover	1
SOIL METRICS	Measures of visible soil surface and profile disturbance
SDIS1. Forest Soil Disturbance	This metric describes surface conditions that affect site sustainability, hydrologic function, and site productivity, using standardized visual disturbance classes, with 0 showing no visual disturbance and 3 = severely disturbed.	Soil disturbance class = x	1

Table 4. Metric assessment points for the various SPO and AP groups. Groups that share the same metric assessment points are assigned the same variant number (e.g., IH, ML and AP groups all have the same values for VCAN1, so they are assigned to variant 1. IH = Interior Highlands shortleaf pine–oak. IH1 = Interior Highlands shortleaf pine–oak forest and woodlands; Interior Highlands shortleaf pine–bluestem woodland; ML = montane longleaf pine–shortleaf pine woodlands; AP = Southern Appalachian pine–oak woodlands; WG = West Gulf coastal plain pine–oak woodlands; EP = southeast coastal plain and Piedmont shortleaf pine–oak woodlands.

METRICS	Measures	Variant and Group Codes		Metric Rating
CANOPY METRICS			Excellent	Good	Fair	Poor
VCAN1. Canopy: Southern Yellow Pine Basal Area	x m²/ha basal area of y pine(s)	v1.IH-ML-AP	BA (8.0–17.2)	(6.9–8.0 or 17.2–20.7)	(2.3 to <6.9 or > 20.7 to 25.3)	(<2.3 or >25.3)
		v2.WG-CP	BA (6.9–19.5)	(4.6 to <6.9 or >19.5–23.0)	(2.3 to <4.6 or >23.0 to 26.4)	(<2.3 or >26.4)
VCAN2. Southern Yellow Pine Canopy Cover	x% canopy cover of y pine(s)	v1.IH-ML-AP	>25%–70%	20%–25% or >70%–80%	10% to <20% or >80%–90%	<10% or >90%
		v2.WG-CP	>25%–75%	>15%–25% or >75%–85%	10%–15% or >85%–95%	<10% or >95%
VCAN3. Southern Yellow Pine Stand Size Structure	Basal area ≥ x m²/ha of y pine trees ≥ z cm DBH class	v1.IH-WG-CP DBH >35 cm	BA > (>4.6)	BA > (>2.3–4.6)	BA < (<2.3), but SP present	< SP absent
		v2.ML DBH > 35 cm	As above but with flat-top longleaf	As above, but with no flat-top longleaf present	but no flat-top longleaf present	but no flat-top longleaf present
		v3.AP DBH > 30 cm	BA > (>4.6)	BA > (>2.3–4.6)	BA < (<2.3), but SP present	< SP absent
VCAN4. Canopy: Fire-Tolerant Hardwood Basal Area	X to y m²/ha BA of fire-tolerant hardwood trees	v1.IH1	BA < (<11.5)	BA > (>11.5–13.8)	BA > (13.8–16.1)	BA > (>16.1)
		v2.IH2-AP-WG-CP	BA < (4.6)	BA > (4.6 to 6.9)	BA > (6.9 to 9.2)	BA > (9.2)
		v3.ML	BA < (4.6)	BA > (4.6 to 9.2)	BA > (9.2 to 11.5)	BA > (11.5)
VCAN5. Canopy: Fire-Intolerant Tree Basal Area	X to y m²/ha BA of fire-intolerant trees	v1, All	BA < (2.3)	BA > (2.3 to 4.6)	BA > (4.6 to 6.9)	BA > (6.9)
VCAN6. Stand Density Index (not applied to AP) (optional)	SDI = x–y (x–y% of maximum SDI of z)	v1.IH	SDI = 65–135	45–65 or 135–180	20–45 or 180–225	<20 or >225
		v2.ML	SDI = 55–120	40–55 or 120–160	15–40 or 160–200	<15 or >200
		v3.WG-CP	SDI = 55–155	35–55 or 155–205	20–35 or 205–225	<20 or >225
MIDSTORY/SHRUB METRICS			Excellent	Good	Fair	Poor
VMID1. Midstory: Fire-Tolerant Hardwood Cover	x% to y% cover of midstory fire-tolerant hardwoods	v1.IH1	2% to <20%	20% to 40%	40% to 50%, or <2%	>50%
		v2.IH2-ML-AP	2% to <10%	10%–30% or <2%	>30% to 40%	>40%
		v3.WG-CP	2% to <10%	10%–20% or <2%	>20% to 35%	>35%
VMID2. Midstory: Fire-Intolerant Hardwood Cover	x% to y% cover of fire-intolerant hardwood midstory	v1.IH1-AP-WG-CP	<10%	10%–20%	>20%–30%	>30%
		v2.IH2-ML	<5%	5%–10%	>10%–20%	>20%
VSHR1. Tall Shrub (3–10 ft tall) Cover	Tall shrubs average x% to y% cover.	v1.IH1	<30%	30%–40%	>40%–50%	>50%
		v2.IH2	<5%	5%–10%	>10%–25%	>25%
		v3. ML-AP-WG-CP	<15%	15%–20%	>20%–30%	>30%
VSHR2. Short Shrub (< 3 ft tall) Cover	Short shrubs average x% to y% cover	v1.IH1-WG-CP	<20%	20%–30%	>30%–45%	>45%
		v2.IH2-ML	<20%	20%–25%	>25%–40%	>40%
		v3.AP	<50%	50%–70%	>70%–80%	>80%
GROUND LAYER METRICS			Excellent	Good	Fair	Poor
VGRD1. Overall Native Herbaceous Ground Cover	x% to y% herbaceous cover	V1.IH1-WG-CP	35%–80%	20% to <35% or > 80%	10% to <20%	<10%
		v2.IH2-ML	>45%–80%	30%–45% or >80%	15% to <30%	<15%
		v3.AP	>15%	5%–15%	<5%	0%
VGRD2. Native Graminoid Cover	x% to y% cover of all native graminoids	v1.IH-ML	>25%–85%	20%–25% or >85%	10% to <20%	<10%
		v2.AP	>10%	5%–10%	<5%	0%
		v3.WG-CP	25%–100%	>15% to <25%	10% to <15%	<10%
VGRD3. Floristic Quality Index, Mean C (optional)	Mean C x to y	v1, All	Mean C > 4.00	3.01 to 4.00	2.01 to 3.00	<2.00
VGRD4. Invasive Plant Presence/ Distribution	Invasive non-native plant species x% to y% cover	v1, All	Absent	Present < 1%	1% to 5%	>5%
SOIL METRIC		Excellent	Good	Fair	Poor
SDIS1. Forest Soil Disturbance	Soil disturbance class = x	v1, All	Soil Disturbance Class 0	1	2	3

Table 5. Case study showing metric ratings for Cherokee National Forest, using the southern Appalachian pine–oak woodlands. Six metrics (see Table 3 for descriptions) assessed sites managed with prescribed fire (n = 6) between two time periods and baseline sites (n = 5). For sites with prescribed fire, the plots were (1) measured after 4 to 7 years, after one prescribed fire between 2004 and 2006, and (2) measured between 2016 and 2019, after at least one additional prescribed fire. Five sites were selected with measurements prior to fire (baseline) or controls (no fire management), measured between 2005 and 2008. Evaluation scale: 4.0 to 3.5 = excellent (dark green), 2.5 to <3.5 = good (light green), 1.5 to <2.5 = fair (yellow), <1.5 = poor (red) [8].

	Baseline (n = 5)	Prescribed Fire History (n = 6)
CANOPY AND MIDSTORY METRICS	No Fire	4–7 Years after First Fire	10–14 Years after 2 or More Fires
VCAN1. Canopy: Southern Yellow Pine Basal Area	2.2	2.5	2.7
VCAN3. Southern Yellow Pine Stand Size Structure	2.6	2.7	2.7
VCAN4. Canopy: Fire-Tolerant Hardwood Basal Area	1.4	2.2	2.3
VCAN5. Canopy: Fire-Intolerant Tree Basal Area	1.6	1.8	2.0
VMID1. Midstory: Fire-Tolerant Hardwood Cover	4.0	3.7	3.7
VMID2. Midstory: Fire-Intolerant Tree Cover	3.8	3.3	4.0
Overall Condition Score	2.9	2.9	3.2

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Nordman, C.; Faber-Langendoen, D.; Baggs, J. Rapid Ecological Integrity Assessment Metrics to Restore Wildlife Habitat and Biodiversity for Shortleaf Pine–Oak Ecosystems. Forests 2021, 12, 1739. https://doi.org/10.3390/f12121739

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Nordman C, Faber-Langendoen D, Baggs J. Rapid Ecological Integrity Assessment Metrics to Restore Wildlife Habitat and Biodiversity for Shortleaf Pine–Oak Ecosystems. Forests. 2021; 12(12):1739. https://doi.org/10.3390/f12121739

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Nordman, Carl, Don Faber-Langendoen, and Joanne Baggs. 2021. "Rapid Ecological Integrity Assessment Metrics to Restore Wildlife Habitat and Biodiversity for Shortleaf Pine–Oak Ecosystems" Forests 12, no. 12: 1739. https://doi.org/10.3390/f12121739

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Rapid Ecological Integrity Assessment Metrics to Restore Wildlife Habitat and Biodiversity for Shortleaf Pine–Oak Ecosystems

Abstract

1. Introduction

1.1. Definition of Southern Open Pine Ecosystems

1.2. Priority Wildlife Species

1.3. Management of Southern Open Pine Forests

1.4. Purpose

2. Materials and Methods

2.1. Ecological Integrity Assessment Methods: Metrics-Based Approach

2.1.1. Specification of Ecosystem Types

2.1.2. Develop Conceptional Models

2.1.3. Specify the Level of Assessment

2.1.4. Select the Indicators and Metrics

2.1.5. Determine Metric Assessment Points/Thresholds

2.1.6. Provide Assessment Tools

2.2. Peer-Review Workshops to Refine the Metrics

2.3. Case Study of EIA Metrics

3. Results

3.1. Ecosystem Types

3.2. Metrics List

3.3. Metric Assessment Points

3.3.1. Canopy

3.3.2. Midstory/Shrub

3.3.3. Ground Layer

3.4. Metric Summaries by Open Pine Group

3.5. Case Study

4. Discussion

4.1. Metrics-Based Approach and Reference Conditions

4.2. Wildlife and Ecological Integrity Assessments

4.3. Application of Metrics

Author Contributions

Funding

Data Availability Statement

Acknowledgments

Conflicts of Interest

Appendix A. Priority Wildlife Species

Appendix B. Metric and Metric Ratings for Each Shortleaf Pine–Oak Group and Southern Appalachian Pine–Oak Group

References

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