Search Results (29)

Restoration of the longleaf pine forest ecosystem is critical for biodiversity. However, the mixed hardwood forests can grow naturally in the same area. There are limited studies comparing soil organic matter and nutrient contents for restoring longleaf pine forests from the mixed hardwood forest areas in the southeastern USA. In this study, a comparison of the contents in soil organic matter, macro-nutrients, trace metal elements, and litterfall amount, was conducted on the 16 forest stands (4 treatments including stand stages × 4 replicants) at William B. Bankhead National Forest in Alabama through the space-replace-time approach. The results indicate that longleaf pine forests have lower contents of soil organic matter, macro-nutrients, most trace metal elements, and litterfall amount than mixed hardwood forests. However, longleaf pine forests have higher soil Ca, Ba, and Pb contents than hardwood forests. Soil Fe content has more correlations with the contents of other metal elements than soil Mn. The results suggest that multiple ecosystem functions, including soil ecology, must be considered in the regional restoration of the longleaf pine ecosystem. Longleaf pine forests with a certain amount of mixed hardwood trees may be a good way to maintain soil organic matter and nutrients. Full article

Prescribed fire is increasingly utilized for conservation and restoration goals, yet there is limited empirical evidence supporting its effectiveness in reducing wildfire-induced damages to highly valued resources and assets (HVRAs)—whether natural, cultural, or economic. This study evaluates the efficacy of prescribed fire in reducing wildfire severity to LANDFIRE-defined vegetation classes and HVRAs impacted by the 2017 West Mims event, which burned across both prescribed-fire treated and untreated areas within the Okefenokee National Wildlife Refuge. Wildfire severity was quantified using the differenced normalized burn ratio (dNBR) index, while treatment records were used to calculate the prescribed frequency and post-treatment duration, which is defined as the time elapsed between the last treatment and the West Mims event. A generalized additive model (GAM) was fit to model dNBR as a function of post-treatment duration, fire frequency, and vegetation type. Although dNBR exhibited considerable heterogeneity both within and between HVRAs and vegetation classes, areas treated with prescribed fire demonstrated substantial reductions in burn severity. The beneficial effects of prescribed fire were most pronounced within approximately two years post-treatment with up to an 88% reduction in mean wildfire severity. However, reductions remained evident for approximately five years post-treatment according to our model. The mitigating effect of prescribed fire was most pronounced in Introduced Upland Vegetation-Shrub, Eastern Floodplain Forests, and Longleaf Pine Woodland when the post-treatment duration was within 12 months. Similar trends were observed in areas surrounding red-cockaded woodpecker nesting sites, which is an HVRA of significant ecological importance. Our findings support the frequent application of prescribed fire (e.g., one- to two-year intervals) as an effective strategy for mitigating wildfire severity to HVRAs. Full article

Longleaf pine (Pinus palustris Mill.) is a conifer historically associated with an open forest ecosystem that extended across much of the coastal plain of the Southeastern United States. It now exists mainly in isolated fragments following the conversion of forests and the long-term disruption of the low-intensity fire regime upon which the species depends. Recent decades have seen efforts to restore longleaf pine forests by government and private landowners. This was reflected in analyses of national forest inventory data during two time periods, ca. 2009–2015 and 2016–2021, that showed increases in the estimated number of longleaf pine trees, the area of the longleaf pine forest type, and the number and area of planted longleaf pine, along with growth in mean plot-level longleaf pine carbon and importance value. At the same time, we found a decrease in the overall forest area containing longleaf pine, manifested across a variety of other forest types. These results point to a dynamic through which forests dominated by longleaf pine are becoming more widespread via restoration, while forests in which the species is a less important component are transitioning to other forest types or land uses. We also detected a decrease over time in the estimated number of longleaf seedlings across most states and forest types and a decline in naturally regenerated longleaf pine. To further assess regeneration trends in longleaf pine, we calculated the estimated proportion of small trees (seedlings and saplings) for the entire species and for seed zone sub-populations. We found a species-wide decrease in the proportion of small trees, from 82.1 percent to 75.1 percent. This reduction was most pronounced along the edges of the species distribution and could indicate less sustainable levels of regeneration in some areas. These results underscore the challenges of facilitating natural regeneration in this important species. Full article

The longleaf pine (Pinus palustris P. Mill.) forest type occupied a much greater area in the United States prior to the arrival of Europeans, estimated to be around 37.2 million hectares. This area has been greatly reduced, and these ecosystems now occupy only about 1.2 to 1.6 million hectares. However, there has been a great interest in the restoration of this forest type mainly due to concerns about the loss of ecosystem services associated with these forests; the improved seedling quality and yield potentials bolster those efforts. Beyond that, existing stands are actively managed through different types of practices, including thinnings, prescribed burns often to manipulate the vegetation of other species, and the various timings of clearcuts. Thus, managers need tools to estimate site quality and ultimately productivity. A commonly used measure of site quality is site index, or the height of some defined dominant portion of the stand at a standardized base or index age. The primary objectives are to summarize the 16 existing equations to estimate site index and dominant height in naturally regenerated longleaf pine stands and to examine and visually compare their predicted behavior across a range of site quality and age conditions. Important considerations when using site index of anamorphism and polymorphism as well as base-age invariance are reviewed. Biologically, polymorphism is often considered advantageous since for many species differences in site quality not only result in different asymptotic dominant heights, but also varying rates in their approach to the asymptote. Of the 16 equations examined, only nine of them were polymorphic in nature, but all equations were base-age invariant. There is not an individual equation that is clearly superior because, for instance, it is either anamorphic in nature, is polymorphic but developed based on anamorphic curves, fit using data obtained from temporary plots, or it is limited geographically. Given these limitations, others can use this publication as a reference to determine which equation they feel is best for their particular situation. Full article

Monitoring water consumption dynamics across the geographic range of an ecosystem may indicate the possible variation and stress in a biome. Here, model output data based on remote sensing (1979–2022) were used to examine the water consumption dynamics and effects on cone production in three geographic margins in the longleaf pine’s range (i.e., Bladen Lake State Forest, Escambia Experimental Forest, and Kisatchie National Forest) under varying climatic conditions. Results indicated that the mean annual transpiration at Escambia was approximately 431 mm and that at Bladen and Kisatchie was 500 mm. Mean monthly transpiration peaked twice (June and October) at Escambia but only once (August) at Bladen and Kisatchie. The mean annual evapotranspiration ranged from approximately 900 mm at Kisatchie to about 791 mm at Escambia and Bladen. The mean annual transpiration/evapotranspiration ratio was about 0.65 at Bladen and 0.55 at Escambia and Kisatchie. A significant correlation existed between evapotranspiration and specific humidity across the sites on a monthly scale but not on a yearly scale. Significant negative relationships existed between precipitation and the ratios of transpiration/precipitation and evapotranspiration/precipitation on the yearly scale across the sites. Negative power relationships were observed between precipitation and the specific humidity/precipitation ratio on monthly and yearly scales. Cone production was generally highest in years with moderate water consumption. These results provide baseline information on how hydrological and ecological processes of longleaf pine forests interact with climate across broad spatial and temporal scales. Full article

While many tree species occur across the Coastal Plain of the southeastern United States, longleaf pine (Pinus palustris C. Lawson) savannas and woodlands once dominated this region. To quantify longleaf pine’s past primacy and trends in the Coastal Plain, we combined seven studies consisting of 255,000 trees from land surveys, conducted between 1810 and 1860 with other descriptions of historical forests, including change to the present day. Our synthesis found support that Pinus palustris predominantly constituted 77% of historical Coastal Plain trees and upland oaks (Quercus) contributed another 8%. While Pinus still dominates these forests today (58% of all trees), most are now either planted loblolly (Pinus taeda L.) or slash (Pinus elliottii Engelm.) pines. Water oak (Quercus nigra L.), live oak (Quercus virginiana Mill.), sweetgum (Liquidambar styraciflua L.), and red maple (Acer rubrum L.) have increased their proportions compared to historical surveys; both longleaf pine and upland oaks have declined to ≤5% of all trees. Our work also supports previous estimates that longleaf pine originally dominated over 25–30 million ha of Coastal Plain forests. As late as the early 1900s, longleaf pine may still have covered 20 million ha, but declined to 7.1 million ha by 1935 and dropped to 4.9 million ha by 1955. Longleaf pine’s regression continued into the mid-1990s, reaching a low of about 1.3 million ha; since then, restoration efforts have produced a modest recovery to 2.3 million ha. Two centuries of overcutting, land clearing, turpentining for chemicals, fire exclusion followed by forest densification by fire-sensitive species, and other silvicultural influences, including widespread loblolly and slash pine plantations, have greatly diminished the Coastal Plain’s once extensive open longleaf pine forests. Full article

Prairie and savanna ecosystems have declined dramatically worldwide. In the Southeastern United States, longleaf pine savannas have been reduced to less than 3% of their pre-European range. Restoring longleaf pine across the area has become a regional goal. Little bluestem (Schizachyrium scoparium (Michx.) Nash) is critical to carrying the ecologically important fire through this ecosystem in some longleaf pine savannas. Little bluestem has a range that spans most of north America and is thought to display ecotypic variation. As a part of a longleaf pine restoration project in Camden, SC, we investigated whether the seed source of little bluestem and the site preparation techniques impacted the survival and growth of broadcasted seeds. In the field and greenhouse, we compared locally and commercially sourced seeds and field site preparation techniques including discing, raking, or no treatment. At the end of the growing season, there were significantly more plants grown from seeds collected locally compared to plants from seeds available commercially. Plants grown from locally collected seeds also invested more heavily in roots than plants grown from commercial seeds. Site preparation techniques did not appear to significantly impact plant survival. Collecting seed locally will help to ensure long-term restoration success by establishing populations of plants that are adapted to the local environmental conditions. Full article

Historically abundant longleaf pine (Pinus palustris Mill.) trees were once a leading source of profit and ecosystem services across the southeastern United States. The widespread decline in longleaf numbers following European colonization has prompted substantial restoration efforts, though much is still not understood about longleaf growth and reproductive processes. In this study, we used Pearson and regression correlation analysis to quantify the relationship between cone production, radial growth, and climate signals in longleaf pine trees at three sites across their range. We documented a high amount of intersite variability; trees at all three sites experienced significant relationships between reproduction, radial growth, and climate, though in different and sometimes contrasting ways. We found a roughly equivalent number of significant cone growth and climate correlations with extreme climate events (e.g., heat stress, hurricane frequency) as with average climate conditions, and highlight the need to consider both over multiple spans of time. This study provides a new understanding of how climate variables relate to the relationship between growth and reproduction in longleaf pine trees. Full article

Longleaf pine (Pinus palustris Mill.) savannas and woodlands are known for providing numerous ecosystem services such as promoting biodiversity, reducing risk of wildfire and insect outbreaks, and increasing water yields. In these open pine systems, there is also interest in managing carbon (C) in ways that do not diminish other ecosystem services. Additionally, there may be management strategies for accomplishing these same objectives in plantations and degraded stands that developed from natural regeneration. For example, C accumulation in live trees and C storage in harvested wood products could be increased by extending rotations and converting plantations to multi-aged stands. Belowground C storage could be enhanced by incorporating pyrogenic C into the mineral soil before planting longleaf pines in clearcut areas, but this may be contrary to findings that indicate that minimizing soil disturbance is important for long-term soil C storage. We suggest examining approaches to reduce total ecosystem C emissions that include using targeted browsing or grazing with domesticated livestock to supplement prescribed burning, thereby reducing C emissions from burning. The mastication of woody vegetation followed by a program of frequent prescribed burning could be used to reduce the risk of substantial C emissions from wildfires and to restore function to savannas and woodlands with hardwood encroachment and altered fire regimes. Many of these approaches need to be validated with field studies or model simulations. There is also a need to improve the estimates of dead wood C stocks and C storage in harvested wood products. Finally, eddy covariance techniques have improved our understanding of how disturbances influence longleaf pine C dynamics over multiple time scales. However, there is a need to determine the degree to which different silvicultural approaches, especially those for adapting ecosystems to climate change, influence C accumulation. Overall, our review suggests that there are numerous opportunities for research on C dynamics in longleaf pine ecosystems, and these systems are likely well-positioned to accomplish C objectives while offering other ecosystem services. Full article

Sporadic cone (or seed) production challenges longleaf pine forest restoration. Characterizing annual cone production change from long-term monitored data provides functional information on the foundational species of this imperiled ecosystem. In this study, permutation entropy (PE) and phase change were used to analyze longleaf pine annual cone production based on cone counts from four sites (Escambia Experimental Forest, Blackwater River State Forest, The Jones Center at Ichauway, and Sandhills State Forest). PE is an analytical tool to measure the complexity of a dynamic system while phase change characterizes the stage of self-organization. Results indicate that PE at each site was close to 1.0 (largely random changes in annual cone production) and generally increased with time. The positive association between the permutation entropy of cone production and average air temperature at different times was significant at two sites (Blackwater River State Forest and The Jones Center at Ichauway). The frequency distribution of phases (e.g., Poor (P), Fair (F), Good (G), Bumper (B)) in cone production followed negative power laws. Phase P could transition to any stage, but more than 50% remained in P across sites. For phase G, it would revert to P more than 50% of the time. Phase B would shift to P, except at Sandhills State Forest. The average lasting time of phase P was approximately 3.7 years. The overall relationship between the interval time of phase B and cone production was not statistically significant. Similarly, the overall relationship between cone production in phase B and the phase change times between consecutive B phases was not statistically significant. These results provide information on the ecological complexity of cone (or seed) production. Our methods can be helpful for estimating the occurrence of bumper cone (or seed) production, the lasting period between phase changes, and providing a tool for predicting natural regeneration potential over time for longleaf pine and other tree species (e.g., masting species). Full article

The sporadic cone production of longleaf pine (Pinus palustris Mill.) challenges the restoration of the longleaf pine ecosystem. While much has been learned about longleaf pine cone production at the stand level, little information exists at the tree level regarding cone production and energy allocational strategy. This study aims to analyze cone production and diameter growth of approximately ten sampled longleaf pine trees at seven sites across the southeastern USA over the past twenty years. The results indicate that three-year cycles dominated the cone production dynamics, but longer cycles (four years and more) also occurred. The dynamics of entropy in cone production varied among trees. Taylor’s law, which describes the correlation between average and variance, existed in cone production for the majority of trees. Lagged cone production at one and two years was not autocorrelated among trees across sites. No significant relationships existed between tree diameter (or basal area) growth and cone production among trees across sites. This study provides new information on cone production at the individual tree level and narrows down the possible mechanisms. The results will be helpful in developing strategies for the management and modeling of longleaf pine cone production. Full article

Prescribed fire is used globally as a habitat restoration tool and is widely accepted as supporting biotic diversity. However, in fire-prone ecosystems, research has sometimes documented post-fire reduction in ant diversity and accompanying changes in seed removal behavior. This is concerning because ants provide important ecosystem services that can aid in restoration efforts, including seed dispersal. In this study, we examined the immediate impacts of fire in the well-studied ant community of longleaf pine forests (LLP) in the SE USA. We surveyed seed-removing ant species in a LLP sandhill ecosystem to investigate the effects of prescribed fire and coarse woody debris (CWD), a nesting and foraging resource, on ant community composition and ant–seed interactions. Seed-removing ants comprised a significant portion of detected ant species (20 of 45); eight of these species are documented removing seeds for the first time. Following an experimentally applied low-intensity summer burn, decreases in seed remover detection were observed, along with reductions in the number of seeds removed, across both burned and unburned areas; neither prescribed fire nor proximity to CWD significantly influenced these factors. Together, these results show that seed-removing ant species constitute a substantial proportion of the LLP sandhill ant community and are relatively robust to habitat changes mediated by low-intensity prescribed burning during the growing season. Considering ant community resiliency to fire, we can infer that using prescribed fire aligns with the goals of restoring and maintaining biotic diversity in this fire-prone ecosystem. Full article

Longleaf pine forests are economically and culturally valued ecosystems in the southeastern United States. Efforts to restore the longleaf pine ecosystem have risen dramatically over the past three decades. Longleaf pine restoration generally involves varying degrees of forest harvesting and frequent applications of prescribed fire. Thus, it is important to understand their interactions with the atmosphere on a large scale. In this study, we analyzed 14 parameters of aerosols, gasses, and energy from three areas with longleaf pine restoration (named Bladen in eastern NC, Escambia in southern AL and northern FL, and Kisatchie in central LA, USA) from 2000 to 2021 using multiple satellites. Averaged across the areas, the monthly aerosol optical depth at 483.5 nm was about 0.022, and the monthly aerosol single scattering albedo was 0.97. Black carbon column mass density averaged 7.46 × 10⁻⁷ kg cm⁻² across these areas, but Kisatchie had a higher monthly dust column mass density (2.35 × 10⁻⁴ kg cm⁻²) than Bladen or Escambia. The monthly total column ozone and CO concentration averaged about 285 DU and 135 ppbv across the three areas. Monthly SO₂ column mass density was significantly higher in Bladen (4.42 × 10⁻⁶ kg cm⁻²) than in Escambia and Kisatchie. The monthly surface albedo in Escambia (0.116) was significantly lower than in the other areas. The monthly total cloud area fraction averaged about 0.456 across the three areas. Sensible and latent heat net flux and Bowen ratios significantly differed among the three areas. Bowen ratio and total cloud area fraction were not significantly correlated. Net shortwave of the forest surface averaged about 182.62 W m⁻² across the three areas. The monthly net longwave was much lower in Bladen (−90.46 W m⁻²) than in Escambia and Kisatchie. These results provide the baseline information on the spatial and temporal patterns of interactions between longleaf pine forests under restoration and the atmosphere and can be incorporated into models of climate change. Full article

(1) Silvicultural applications that manipulate woody debris loading and the structural composition of a forest can have both short and long-term effects on biogeochemical cycling. Longleaf pine forests have been the historically dominant community types throughout much of the Southeastern United States. Fire exclusion, hardwood encroachment, and resource exploitation have severely reduced the amount of remaining longleaf pine habitats, making ecological restoration necessary. The silvicultural treatments used to reestablish these communities have been widespread, leading to some skepticism regarding the sustainability of certain restoration practices. (2) This study aimed to understand how overstory manipulation and woody debris management affected soil water retention rates and nutrient availability. Using a randomized complete block design, abiotic responses to biomass harvesting, conventional harvesting, and mastication treatments were measured across a soil moisture gradient in the South Carolina sandhills. (3) Our findings indicate that mastication increased soil moisture retention rates by 37% and 41%, on average, compared to conventional harvesting and biomass harvesting, respectively. (4) Additionally, soil nutrient stocks did not decline following any management practice, indicating that both biomass harvesting and mastication treatments may not necessarily impact site productivity in a negative manner. These findings imply that mastication treatments keep moisture retention high and do not immediately change soil nutrient availability in longleaf pine forests. Long-term vegetation response studies should continue to document successional trends in conjunction with moisture retention rates and long-term nutrient pulsing. Full article