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Forests, Volume 10, Issue 3 (March 2019)

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Cover Story (view full-size image) There is a long history of experimental research in the Luquillo Experimental Forest in Puerto [...] Read more.
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Open AccessArticle
Influence of 3D Spruce Tree Representation on Accuracy of Airborne and Satellite Forest Reflectance Simulated in DART
Forests 2019, 10(3), 292; https://doi.org/10.3390/f10030292
Received: 22 February 2019 / Accepted: 19 March 2019 / Published: 26 March 2019
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Abstract
Advances in high-performance computer resources and exploitation of high-density terrestrial laser scanning (TLS) data allow for reconstruction of close-to-reality 3D forest scenes for use in canopy radiative transfer models. Consequently, our main objectives were (i) to reconstruct 3D representation of Norway spruce ( [...] Read more.
Advances in high-performance computer resources and exploitation of high-density terrestrial laser scanning (TLS) data allow for reconstruction of close-to-reality 3D forest scenes for use in canopy radiative transfer models. Consequently, our main objectives were (i) to reconstruct 3D representation of Norway spruce (Picea abies) trees by deriving distribution of woody and foliage elements from TLS and field structure data and (ii) to use the reconstructed 3D spruce representations for evaluation of the effects of canopy structure on forest reflectance simulated in the Discrete Anisotropic Radiative Transfer (DART) model. Data for this study were combined from two spruce research sites located in the mountainous areas of the Czech Republic. The canopy structure effects on simulated top-of-canopy reflectance were evaluated for four scenarios (10 × 10 m scenes with 10 trees), ranging from geometrically simple to highly detailed architectures. First scenario A used predefined simple tree crown shapes filled with a turbid medium with simplified trunks and branches. Other three scenarios used the reconstructed 3D spruce representations with B detailed needle shoots transformed into turbid medium, C with simplified shoots retained as facets, and D with detailed needle shoots retained as facets D. For the first time, we demonstrated the capability of the DART model to simulate reflectance of complex coniferous forest scenes up to the level of a single needle (scenario D). Simulated bidirectional reflectance factors extracted for each scenario were compared with actual airborne hyperspectral and space-borne Sentinel-2 MSI reflectance data. Scenario A yielded the largest differences from the remote sensing observations, mainly in the visible and NIR regions, whereas scenarios B, C, and D produced similar results revealing a good agreement with the remote sensing data. When judging the computational requirements for reflectance simulations in DART, scenario B can be considered as most operational spruce forest representation, because the transformation of 3D shoots in turbid medium reduces considerably the simulation time and hardware requirements. Full article
(This article belongs to the Special Issue Forestry Applications of DART Model)
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Open AccessArticle
Linking Terrestrial LiDAR Scanner and Conventional Forest Structure Measurements with Multi-Modal Satellite Data
Forests 2019, 10(3), 291; https://doi.org/10.3390/f10030291
Received: 25 January 2019 / Revised: 19 March 2019 / Accepted: 22 March 2019 / Published: 26 March 2019
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Abstract
Obtaining information on vertical forest structure requires detailed data acquisition and analysis which is often performed at a plot level. With the growing availability of multi-modal satellite remote sensing (SRS) datasets, their usability towards forest structure estimation is increasing. We assessed the relationship [...] Read more.
Obtaining information on vertical forest structure requires detailed data acquisition and analysis which is often performed at a plot level. With the growing availability of multi-modal satellite remote sensing (SRS) datasets, their usability towards forest structure estimation is increasing. We assessed the relationship of PlanetScope-, Sentinel-2-, and Landsat-7-derived vegetation indices (VIs), as well as ALOS-2 PALSAR-2- and Sentinel-1-derived backscatter intensities with a terrestrial laser scanner (TLS) and conventionally measured forest structure parameters acquired from 25 field plots in a tropical montane cloud forest in Kafa, Ethiopia. Results showed that canopy gap-related forest structure parameters had their highest correlation (|r| = 0.4 − 0.48) with optical sensor-derived VIs, while vegetation volume-related parameters were mainly correlated with red-edge- and short-wave infrared band-derived VIs (i.e., inverted red-edge chlorophyll index (IRECI), normalized difference moisture index), and synthetic aperture radar (SAR) backscatters (|r| = −0.57 − 0.49). Using stepwise multi-linear regression with the Akaike information criterion as evaluation parameter, we found that the fusion of different SRS-derived variables can improve the estimation of field-measured structural parameters. The combination of Sentinel-2 VIs and SAR backscatters was dominant in most of the predictive models, while IRECI was found to be the most common predictor for field-measured variables. The statistically significant regression models were able to estimate cumulative plant area volume density with an R2 of 0.58 and with the lowest relative root mean square error (RRMSE) value (0.23). Mean gap and number of gaps were also significantly estimated, but with higher RRMSE (R2 = 0.52, RRMSE = 1.4, R2 = 0.68, and RRMSE = 0.58, respectively). The models showed poor performance in predicting tree density and number of tree species (R2 = 0.28, RRMSE = 0.41, and R2 = 0.21, RRMSE = 0.39, respectively). This exploratory study demonstrated that SRS variables are sensitive to retrieve structural differences of tropical forests and have the potential to be used to upscale biodiversity relevant field-based forest structure estimates. Full article
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Open AccessArticle
The Relationship between Stem Diameter Shrinkage and Tree Bole Moisture Loss Due to Transpiration
Forests 2019, 10(3), 290; https://doi.org/10.3390/f10030290
Received: 12 February 2019 / Revised: 7 March 2019 / Accepted: 21 March 2019 / Published: 23 March 2019
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Abstract
The responsiveness of four types of stem diameter shrinkage indicators to sap flow changes was compared under four air temperature and cloudiness conditions: above 0 °C below 80% cloud cover days; above 0 °C large percentage cloud cover days; low temperature below 80% [...] Read more.
The responsiveness of four types of stem diameter shrinkage indicators to sap flow changes was compared under four air temperature and cloudiness conditions: above 0 °C below 80% cloud cover days; above 0 °C large percentage cloud cover days; low temperature below 80% cloud cover days; and low temperature large percentage cloud cover days. In this study, we investigated the effects of indicative functions of relatively easy-to-access stem diameter shrinkage on variation characteristics of sap flow. High-resolution-based stem diameter shrinkage is related to changes in tree moisture content. Stem diameter shrinkage indicators are adopted to confirm sap flow changes resulting from transpiration pull, which may enhance the power of stem diameter shrinkage as an index for tree bole moisture loss. After measuring stem diameter variations, the following stem diameter shrinkage indicators were calculated: maximum daily shrinkage, daily stem diameter increment, daily stem diameter variation, and tree water deficit-induced stem shrinkage (TWD). Sap flow was measured synchronously, and stem diameter shrinkage indicators were analyzed to confirm their responses to sap flow. TWD was positively correlated (r ≥ 0.317) with daily variations in sap flow and reached extremely significant levels (p ≤ 0.001) under all conditions. TWD and maximum daily shrinkage were able to better reflect the correlation between changes in stem diameter and sap flow on a daily scale, except large percentage cloud cover days with low temperatures. Changes in stem diameter had no correlation with sap flow during low temperature and large percentage cloud cover days. Among all stem diameter shrinkage indicators, TWD showed the highest correlation (r ≥ 0.601 and p ≤ 0.001) with sap flow under all conditions, except during large percentage cloud cover days with low temperatures. The stem diameter shrinkage indicators did not reflect sap flow changes during large percentage cloud cover days with low temperatures. The indicator that best reflected moisture loss of trees was TWD. Full article
(This article belongs to the Section Forest Ecophysiology and Biology)
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Open AccessArticle
Twenty-Five Years of Aboveground Biomass and Carbon Accumulation Following Extreme Wind Damage in an Old-Growth Forest
Forests 2019, 10(3), 289; https://doi.org/10.3390/f10030289
Received: 25 January 2019 / Revised: 4 March 2019 / Accepted: 21 March 2019 / Published: 23 March 2019
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Abstract
Modeling of carbon dynamics at the landscape, regional, and continental scales is currently limited by few empirical studies of biomass and carbon accumulation after some types of disturbances. For temperate forests of North America, only three previous studies described biomass and carbon accumulation [...] Read more.
Modeling of carbon dynamics at the landscape, regional, and continental scales is currently limited by few empirical studies of biomass and carbon accumulation after some types of disturbances. For temperate forests of North America, only three previous studies described biomass and carbon accumulation after wind disturbances, and those were limited by either coarse temporal resolution of the first several decades, or limited time span. Here, 25 years of aboveground biomass and carbon accumulation following severe wind disturbance of an old-growth hemlock-northern hardwoods forest of northwestern Pennsylvania are documented to characterize the temporal trends with fine temporal resolution and extend into the third decade post-disturbance. Mature undisturbed forest at the site supported roughly 296 Mg ha−1 live aboveground biomass and 148 Mg ha−1 of carbon. The disturbance reduced the aboveground woody biomass to ~7 Mg ha−1, and carbon to ~3.5 Mg ha−1. During regrowth, biomass and carbon accumulated slowly at first (e.g., 2–4 Mg ha−1 year−1 for biomass and 1–2 Mg ha−1 year−1 for carbon), but at increasing rates up through approximately 17 years post-disturbance, after which accumulation slowed somewhat to roughly 3.4 Mg ha−1 year−1 of biomass and 1.7 Mg ha−1 year−1 of carbon. It appears that the rates reported here are similar to rates observed after wind disturbance of other temperate forests, but slower than accumulation in some tropical systems. Notably, in tropical forests, post-windthrow accumulation is often very rapid in the first decade followed by decreases, while in the results reported here, there was slow accumulation in the first several years that increased in the second decade and then subsequently slowed. Full article
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Open AccessArticle
Forestland Concession, Land Rights, and Livelihood Changes of Ethnic Minorities: The Case of the Madhupur Sal Forest, Bangladesh
Forests 2019, 10(3), 288; https://doi.org/10.3390/f10030288
Received: 14 February 2019 / Revised: 4 March 2019 / Accepted: 19 March 2019 / Published: 23 March 2019
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Abstract
Forestland concession has been the dominant governance tool for the acquisition of natural state-owned forest resources in many tropical countries, including Bangladesh. Moreover, the forestland concession process confers the holder a bundle of rights. The Sal forests of Bangladesh are treated as some [...] Read more.
Forestland concession has been the dominant governance tool for the acquisition of natural state-owned forest resources in many tropical countries, including Bangladesh. Moreover, the forestland concession process confers the holder a bundle of rights. The Sal forests of Bangladesh are treated as some of the greatest concession forests, as a number of ethnic minorities use these forests for their daily living. Therefore, the objectives of the study were to assess the impacts of Sal forestland concession and land rights on the livelihood development of the ethnic minorities living in the Madhupur Sal Forest (MSF) area of Bangladesh. Using both qualitative and quantitative data collection techniques, the study found out that about two thirds of the original Sal forestland was grabbed by the state and non-state actors. As a result, the ethnic minority inhabitants have lost their traditional land and free access rights to the Sal forests. The process of losing ethnic minorities’ land and forest access rights has been enhanced by the institutional arrangements of the state, which had also created severe conflicts between the Forest Department and the ethnic communities. The study also revealed that the forestland concession has negatively affected the five livelihood capitals development of the ethnic minorities, consequently, their forest-based livelihood has shifted to non-securing jobs or poor income sources, like daily wage labor and subsistence agriculture. Despite this, the development drivers have emphasized the Sal forests and biodiversity conservation, while the livelihood development of the ethnic minorities has been ignored from every level. Therefore, this study would recommend establishing a legitimate process in order to settle the issue of traditional land and the forest rights of ethnic minorities, which could also attain the conservation and development goals of the Sal forests. Full article
(This article belongs to the Section Forest Economics and Human Dimensions)
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Open AccessArticle
The Resistance of Scots Pine (Pinus sylvestris L.) Half-sib Families to Heterobasidion annosum
Forests 2019, 10(3), 287; https://doi.org/10.3390/f10030287
Received: 12 February 2019 / Revised: 14 March 2019 / Accepted: 21 March 2019 / Published: 23 March 2019
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Abstract
This study observed the genotypic variation among Scots pine (Pinus sylvestris L.) half-sib families’ susceptibility to Heterobasidion annosum. Scots pine susceptibility was tested in 12 half-sib families by inoculating them with four different H. annosum strains. At two, six, and ten [...] Read more.
This study observed the genotypic variation among Scots pine (Pinus sylvestris L.) half-sib families’ susceptibility to Heterobasidion annosum. Scots pine susceptibility was tested in 12 half-sib families by inoculating them with four different H. annosum strains. At two, six, and ten months after the inoculations, the susceptibility indicators (incidence rate, pathogen spread, and mortality rate) were compared and the total phenolic compounds (TPC) in the inoculated and control groups determined using the Folin–Ciocalteu method. Among half-sib families, significant differences were found for seedling mortality (range: 1.3%–21.2%); however, the differences in incidence rate (range: 54%–77%) and pathogen spread (range: 24–53 mm) were not significant. The incidence rate among half-sib families correlated positively and significantly (r = 0.72, p < 0.05) with the mortality rate, while the pathogen spread correlated negatively with mortality, although the correlation was not significant (r = −0.29, p > 0.05). The TPC comparison with susceptibility indicators showed that the half-sib families with lower susceptibility were characterized by the ability to increase TPC after inoculation compared to the control group. This tendency was most apparent in stems and roots six and two months after inoculation, respectively. Correlation analyses revealed that higher TPC in stems six months after inoculation determined a lower incidence rate (r = −0.32, p < 0.05), while higher Change in concentration of total phenolic compounds (TPCΔ) indicated a lower pathogen spread (r = −0.60, p < 0.05). The lowest incidence of the pathogen was determined in half-sib families with the highest TPCΔ in the roots two months after inoculation. The lower susceptibility of Scots pine half-sib families is based on a combination of enhanced constitutive and inducible phenolic defense mechanisms. The data may facilitate the selection of Scots pine half-sib families with low susceptibility for breeding programs and forest management strategies. Full article
(This article belongs to the Special Issue Forest Health: Fungal and Insect Ecology)
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Open AccessArticle
Ponderosa Pine Regeneration, Wildland Fuels Management, and Habitat Conservation: Identifying Trade-Offs Following Wildfire
Forests 2019, 10(3), 286; https://doi.org/10.3390/f10030286
Received: 18 February 2019 / Revised: 7 March 2019 / Accepted: 19 March 2019 / Published: 22 March 2019
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Abstract
Increasing wildfires in western North American conifer forests have led to debates surrounding the application of post-fire management practices. There is a lack of consensus on whether (and to what extent) post-fire management assists or hinders managers in achieving goals, particularly in under-studied [...] Read more.
Increasing wildfires in western North American conifer forests have led to debates surrounding the application of post-fire management practices. There is a lack of consensus on whether (and to what extent) post-fire management assists or hinders managers in achieving goals, particularly in under-studied regions like eastern ponderosa pine forests. This makes it difficult for forest managers to balance among competing interests. We contrast structural and community characteristics across unburned ponderosa pine forest, severely burned ponderosa pine forest, and severely burned ponderosa pine forest treated with post-fire management with respect to three management objectives: ponderosa pine regeneration, wildland fuels control, and habitat conservation. Ponderosa pine saplings were more abundant in treated burned sites than untreated burned sites, suggesting increases in tree regeneration following tree planting; however, natural regeneration was evident in both unburned and untreated burned sites. Wildland fuels management greatly reduced snags and coarse woody debris in treated burned sites. Understory cover measurements revealed bare ground and fine woody debris were more strongly associated with untreated burned sites, and greater levels of forbs and grass were more strongly associated with treated burned sites. Wildlife habitat was greatly reduced following post-fire treatments. There were no tree cavities in treated burned sites, whereas untreated burned sites had an average of 27 ± 7.68 cavities per hectare. Correspondingly, we found almost double the avian species richness in untreated burned sites compared to treated burned sites (22 species versus 12 species). Unburned forests and untreated burned areas had the same species richness, but hosted unique avian communities. Our results indicate conflicting outcomes with respect to management objectives, most evident in the clear costs to habitat conservation following post-fire management application. Full article
(This article belongs to the Section Forest Ecology and Management)
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Open AccessArticle
The Joint Effects of Precipitation Gradient and Afforestation on Soil Moisture across the Loess Plateau of China
Forests 2019, 10(3), 285; https://doi.org/10.3390/f10030285
Received: 4 February 2019 / Revised: 20 March 2019 / Accepted: 20 March 2019 / Published: 22 March 2019
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Abstract
Understanding the dependence of soil moisture changes following afforestation on the precipitation gradient and afforested vegetation types is crucial for improving ongoing afforestation projects, and to guide future restoration strategies in water-limited regions. For this study, we characterized afforestation-induced changes in soil moisture [...] Read more.
Understanding the dependence of soil moisture changes following afforestation on the precipitation gradient and afforested vegetation types is crucial for improving ongoing afforestation projects, and to guide future restoration strategies in water-limited regions. For this study, we characterized afforestation-induced changes in soil moisture at depths of 0–3.0 m across a precipitation gradient in the semi-arid Loess Plateau of China. A paired experiment was conducted across 15 sites, where native grasslands served as the baseline hydrology. The results showed that korshinsk peashrub (Caragana korshinskii Kom.), sea buckthorn (Hippophae rhamnoides L.), and black locust (Robinia pseudoacacia L.) afforestation caused an overall strong decline in soil moisture content at depths of below 2.2 m. The degree of soil moisture decline at the regional scale did not vary between different afforested vegetation types but was contingent on precipitation. With decreasing precipitation gradients, afforestation increased the cost of deep soil moisture. Precipitation restrictions began to appear at mean annual precipitation (MAP) = 520 mm, and were intensified at MAP = 380 mm, which could be employed to divide the Loess Plateau into different ecological regions. Because of this, different strategies should be assigned in future restoration practices to these ecological regions to align with localized precipitation conditions. It will likely be prudent to encourage afforestation in areas with MAP of more than 520 mm, while advocating alternative grassland restoration in areas with MAP of less than 380 mm. Full article
(This article belongs to the Special Issue Managing Forests and Water for People under a Changing Environment)
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Open AccessArticle
Assessing the Ability of Image Based Point Clouds Captured from a UAV to Measure the Terrain in the Presence of Canopy Cover
Forests 2019, 10(3), 284; https://doi.org/10.3390/f10030284
Received: 21 February 2019 / Revised: 15 March 2019 / Accepted: 20 March 2019 / Published: 22 March 2019
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Abstract
Point clouds captured from Unmanned Aerial Systems are increasingly relied upon to provide information describing the structure of forests. The quality of the information derived from these point clouds is dependent on a range of variables, including the type and structure of the [...] Read more.
Point clouds captured from Unmanned Aerial Systems are increasingly relied upon to provide information describing the structure of forests. The quality of the information derived from these point clouds is dependent on a range of variables, including the type and structure of the forest, weather conditions and flying parameters. A key requirement to achieve accurate estimates of height based metrics describing forest structure is a source of ground information. This study explores the availability and reliability of ground surface points available within point clouds captured in six forests of different structure (canopy cover and height), using three image capture and processing strategies, consisting of nadir, oblique and composite nadir/oblique image networks. The ground information was extracted through manual segmentation of the point clouds as well as through the use of two commonly used ground filters, LAStools lasground and the Cloth Simulation Filter. The outcomes of these strategies were assessed against ground control captured with a Total Station. Results indicate that a small increase in the number of ground points captured (between 0 and 5% of a 10 m radius plot) can be achieved through the use of a composite image network. In the case of manually identified ground points, this reduced the root mean square error (RMSE) error of the terrain model by between 1 and 11 cm, with greater reductions seen in plots with high canopy cover. The ground filters trialled were not able to exploit the extra information in the point clouds and inconsistent results in terrain RMSE were obtained across the various plots and imaging network configurations. The use of a composite network also provided greater penetration into the canopy, which is likely to improve the representation of mid-canopy elements. Full article
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Open AccessArticle
Harvesting Design by Capital Return
Forests 2019, 10(3), 283; https://doi.org/10.3390/f10030283
Received: 5 March 2019 / Revised: 14 March 2019 / Accepted: 19 March 2019 / Published: 22 March 2019
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Abstract
One can suspect that capital return rate in forestry can be maximized by growing trees experiencing a value-adding assortment transition. Such a situation may or may not endure. We investigate the financial feasibility of a few harvesting schedules for a semi-shade-tolerant tree species. [...] Read more.
One can suspect that capital return rate in forestry can be maximized by growing trees experiencing a value-adding assortment transition. Such a situation may or may not endure. We investigate the financial feasibility of a few harvesting schedules for a semi-shade-tolerant tree species. Some example stands have experienced commercial low thinning, whereas others have experienced young stand cleaning only. High thinning is computationally combined with quality thinning, and further growth of trees is estimated using an applicable growth model. High capital return rates are gained by diameter-limit cutting to the transition diameter between pulpwood and sawlogs. Repeated thinnings lead to a reduction in the capitalization during several decades, the system approaching a stationary state. The transient forest stands investigated show a significant excess capital return, in relation to the stationary state, and this excess return is due to transient tree size distribution. Correspondingly, capital return rate gained in rotation forestry is somewhat higher than that of stationary continuous-cover forestry, and the volumetric yield is much higher. The productive capacity of stands previously thinned from below has been apparently ruined by that treatment. Full article
(This article belongs to the Section Forest Economics and Human Dimensions)
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Open AccessArticle
Effects of Spatial Pattern of Forest Vegetation on Urban Cooling in a Compact Megacity
Forests 2019, 10(3), 282; https://doi.org/10.3390/f10030282
Received: 25 February 2019 / Revised: 16 March 2019 / Accepted: 18 March 2019 / Published: 22 March 2019
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Abstract
Urban forests can be an effective contributor to mitigate the urban heat island (UHI) effect. Understanding the factors that influence the cooling intensity of forest vegetation is essential for creating a more effective urban greenspace network to better counteract the urban warming. The [...] Read more.
Urban forests can be an effective contributor to mitigate the urban heat island (UHI) effect. Understanding the factors that influence the cooling intensity of forest vegetation is essential for creating a more effective urban greenspace network to better counteract the urban warming. The aim of this study was to quantify the effects of spatial patterns of forest vegetation on urban cooling, in the Shanghai metropolitan area of China, using correlation analyses and regression models. Cooling intensity values were calculated based on the land surface temperature (LST) derived from remote sensing imagery and spatial patterns of forest vegetation were quantified by eight landscape metrics, using standard and moving-window approaches. The results suggested that 90 m × 90 m was the optimal spatial scale for studying the cooling effect of forest vegetation in Shanghai’s urban area. It also indicated that woodland performed better than grassland in urban cooling and the size, shape, and spatial distribution of woodland patches had significant impacts on the urban thermal environment. Specifically, the increase of size and the degree of compactness of the patch shape can effectively reduce the LST within the woodland. Areas with a higher percentage of vegetation coverage experienced a greater cooling effect. Moreover, when given a fixed amount of vegetation covers, aggregated distribution provided a stronger cooling effect than fragmented distribution and increasing overall shape complexity of woodlands can enhance the cooling effect on surrounding urban areas. This study provides insights for urban planners and landscape designers to create forest adaptive planning strategies to effectively alleviate the UHI effect. Full article
(This article belongs to the Special Issue Planning and Optimization of Urban and Peri-urban Forests)
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Open AccessArticle
Effects of Seed Size and Sand Burial on Germination and Early Growth of Seedlings for Coastal Pinus thunbergii Parl. in the Northern Shandong Peninsula, China
Forests 2019, 10(3), 281; https://doi.org/10.3390/f10030281
Received: 4 March 2019 / Revised: 17 March 2019 / Accepted: 19 March 2019 / Published: 22 March 2019
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Abstract
This paper examines the effects of seed size and the depth of sand burial on seed germination and seedling development for Pinus thunbergii. Parl. Seeds from 20- to 30-year old trees grown in the coastal area of Yantai were divided into three [...] Read more.
This paper examines the effects of seed size and the depth of sand burial on seed germination and seedling development for Pinus thunbergii. Parl. Seeds from 20- to 30-year old trees grown in the coastal area of Yantai were divided into three size categories (large, medium, and small). The seeds were sown in pots with different depth of sand, and their germination and seedling growth during the first month were investigated. Results showed that large seeds possessed the highest 1000-seed weight and soluble sugar concentration. Large and medium seeds had a higher germination rate, germination index, vigor index, and seedling biomass than small seeds. With the increase in seed size, root mass ratio, root/shoot ratio, specific root length, and specific root area decreased, whereas leaf mass ratio increased. Sand burial depth significantly influenced seed germination and seedling growth, and the highest germination rate and seedling biomass were achieved with 2–3 cm sand burial. We also found that seedling biomass was positively related to germination rate, germination index, and vigor index, but was negatively related to mean germination time. Moreover, seedling biomass was negatively correlated with root mass ratio and root/shoot ratio, but positively correlated with leaf mass ratio, specific root length, and specific root area. The results suggest that seed size and sand burial depth are key factors in the regeneration of the coastal P. thunbergii forest. Full article
(This article belongs to the Special Issue Natural Plant Regeneration Ecology in Forest Ecosystems)
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Open AccessArticle
Visualizing Current and Future Climate Boundaries of the Conterminous United States: Implications for Forests
Forests 2019, 10(3), 280; https://doi.org/10.3390/f10030280
Received: 21 February 2019 / Revised: 7 March 2019 / Accepted: 19 March 2019 / Published: 22 March 2019
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Abstract
Many potential geographic information system (GIS) applications remain unrealized or not yet extended to diverse spatial and temporal scales due to the relative recency of conversion from paper maps to digitized images. Here, we applied GIS to visualize changes in the ecological boundaries [...] Read more.
Many potential geographic information system (GIS) applications remain unrealized or not yet extended to diverse spatial and temporal scales due to the relative recency of conversion from paper maps to digitized images. Here, we applied GIS to visualize changes in the ecological boundaries of plant hardiness zones and the Köppen-Trewartha classification system between current climate (1981–2010) and future climate (2070–2099), as well as changing climate within stationary state boundaries of the conterminous United States, which provide context for the future of forests. Three climate models at Representative Concentration Pathway (RCP) 8.5 were variable in climate projections. The greatest departure from the current climate in plant hardiness zones, which represent the coldest days, occurred where temperatures were coldest, whereas temperatures in the southeastern United States remained relatively stable. Most (85% to 99%) of the conterminous US increased by at least one plant hardiness zone (5.6 °C). The areal extent of subtropical climate types approximately doubled, expanding into current regions of hot temperate climate types, which shifted into regions of warm temperate climate types. The northernmost tier of states may generally develop the hottest months of the southernmost tier of states; Montana’s hottest month may become hotter than Arizona’s current hottest month. We applied these results to demonstrate the large magnitude of potential shifts in forested ecosystems at the end of the century. Shifts in ecological boundaries and climate within administrative boundaries may result in mismatches between climate and ecosystems and coupled human–environment systems. Full article
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Open AccessArticle
Modelling and Predicting the Growing Stock Volume in Small-Scale Plantation Forests of Tanzania Using Multi-Sensor Image Synergy
Forests 2019, 10(3), 279; https://doi.org/10.3390/f10030279
Received: 29 January 2019 / Revised: 18 March 2019 / Accepted: 19 March 2019 / Published: 21 March 2019
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Abstract
Remotely sensed assisted forest inventory has emerged in the past decade as a robust and cost efficient method for generating accurate information on forest biophysical parameters. The launching and public access of ALOS PALSAR-2, Sentinel-1 (SAR), and Sentinel-2 together with the associated open-source [...] Read more.
Remotely sensed assisted forest inventory has emerged in the past decade as a robust and cost efficient method for generating accurate information on forest biophysical parameters. The launching and public access of ALOS PALSAR-2, Sentinel-1 (SAR), and Sentinel-2 together with the associated open-source software, has further increased the opportunity for application of remotely sensed data in forest inventories. In this study, we evaluated the ability of ALOS PALSAR-2, Sentinel-1 (SAR) and Sentinel-2 and their combinations to predict growing stock volume in small-scale forest plantations of Tanzania. The effects of two variable extraction approaches (i.e., centroid and weighted mean), seasonality (i.e., rainy and dry), and tree species on the prediction accuracy of growing stock volume when using each of the three remotely sensed data were also investigated. Statistical models relating growing stock volume and remotely sensed predictor variables at the plot-level were fitted using multiple linear regression. The models were evaluated using the k-fold cross validation and judged based on the relative root mean square error values (RMSEr). The results showed that: Sentinel-2 (RMSEr = 42.03% and pseudo − R2 = 0.63) and the combination of Sentinel-1 and Sentinel-2 (RMSEr = 46.98% and pseudo − R2 = 0.52), had better performance in predicting growing stock volume, as compared to Sentinel-1 (RMSEr = 59.48% and pseudo − R2 = 0.18) alone. Models fitted with variables extracted from the weighted mean approach, turned out to have relatively lower RMSEr % values, as compared to centroid approaches. Sentinel-2 rainy season based models had slightly smaller RMSEr values, as compared to dry season based models. Dense time series (i.e., annual) data resulted to the models with relatively lower RMSEr values, as compared to seasonal based models when using variables extracted from the weighted mean approach. For the centroid approach there was no notable difference between the models fitted using dense time series versus rain season based predictor variables. Stratifications based on tree species resulted into lower RMSEr values for Pinus patula tree species, as compared to other tree species. Finally, our study concluded that combination of Sentinel-1&2 as well as the use Sentinel-2 alone can be considered for remote-sensing assisted forest inventory in the small-scale plantation forests of Tanzania. Further studies on the effect of field plot size, stratification and statistical methods on the prediction accuracy are recommended. Full article
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Open AccessArticle
Genetic Diversity and Population Structure of Alnus cremastogyne as Revealed by Microsatellite Markers
Forests 2019, 10(3), 278; https://doi.org/10.3390/f10030278
Received: 7 February 2019 / Revised: 7 March 2019 / Accepted: 18 March 2019 / Published: 21 March 2019
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Abstract
Alnus cremastogyne Burk. is a nonleguminous, nitrogen-fixing tree species. It is also the most important endemic species of Alnus Mill. in China, possessing important ecological functions. This study investigated population genetic variation in A. cremastogyne using 175 trees sampled from 14 populations native [...] Read more.
Alnus cremastogyne Burk. is a nonleguminous, nitrogen-fixing tree species. It is also the most important endemic species of Alnus Mill. in China, possessing important ecological functions. This study investigated population genetic variation in A. cremastogyne using 175 trees sampled from 14 populations native to Sichuan Province with 25 simple sequence repeat (SSR) markers. Our analysis showed that A. cremastogyne has an average of 5.83 alleles, 3.37 effective alleles, an expected heterozygosity of 0.63, and an observed heterozygosity of 0.739, indicating a relatively high level of genetic diversity. The A. cremastogyne populations in Liangshan Prefecture (Meigu, Mianning) showed the highest level of genetic diversity, whereas the Yanting population had the lowest. Our analysis also showed that the average genetic differentiation of 14 A. cremastogyne populations was 0.021. Analysis of molecular variance (AMOVA) revealed that 97% of the variation existed within populations; only 3% was among populations. Unweighted pair-group method with arithmetic means (UPGMA) clustering and genetic structure analysis showed that the 14 A. cremastogyne populations could be clearly divided into three clusters: Liangshan Prefecture population, Ganzi Prefecture population, the other population in the mountain area around the Sichuan Basin and central Sichuan hill area, indicating some geographical distribution. Further analysis using the Mantel test showed that this geographical distribution was significantly correlated with elevation. Full article
(This article belongs to the Section Forest Ecophysiology and Biology)
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Open AccessArticle
Influence of Scan Density on the Estimation of Single-Tree Attributes by Hand-Held Mobile Laser Scanning
Forests 2019, 10(3), 277; https://doi.org/10.3390/f10030277
Received: 17 February 2019 / Revised: 15 March 2019 / Accepted: 19 March 2019 / Published: 21 March 2019
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Abstract
Nowadays, forest inventories are frequently carried out using a combination of field measurements and remote sensing data, often acquired with light detection and ranging (LiDAR) sensors. Several studies have investigated how three-dimensional laser scanning point clouds from different platforms can be used to [...] Read more.
Nowadays, forest inventories are frequently carried out using a combination of field measurements and remote sensing data, often acquired with light detection and ranging (LiDAR) sensors. Several studies have investigated how three-dimensional laser scanning point clouds from different platforms can be used to acquire information traditionally collected with forest instruments, such as hypsometers and callipers to detect single-tree attributes like tree height and diameter at the breast height. The present study has tested the performances of the ZEB1 instrument, a type of hand-held mobile laser scanner, for single-tree attributes estimation in pure Castanea sativa Mill. stands cultivated for fruit production in Central Italy. In particular, the influence of walking scan path density on single-tree attributes estimation (number of trees, tree position, diameter at breast height, tree height, and crown base height) was investigated to test the efficiency of field measures. The point clouds were acquired by walking along straight lines drawn with different spacing: 10 and 15 m apart. A single-tree scan approach, which included walking with the instrument around each tree, was used as reference data. In order to evaluate the efficiency of the survey, the influence of the walking scan path was discussed in relation to the accuracy of single-tree attributes estimation, as well as the time and cost needed for data acquisition, pre-processing, and analysis. Our results show that the 10 m scan path provided the best results, with an omission error of 6%; the assessment of single-tree attributes was successful, with values of the coefficient of determination and the relative root mean square error similar to other studies. The 10 m scan path has also proved to decrease the costs by about €14 for data pre-processing, and a saving of time for data acquisition and data analysis of about 37 min compared to the reference data. Full article
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Open AccessArticle
Forest Growing Stock Volume Estimation in Subtropical Mountain Areas Using PALSAR-2 L-Band PolSAR Data
Forests 2019, 10(3), 276; https://doi.org/10.3390/f10030276
Received: 26 February 2019 / Revised: 15 March 2019 / Accepted: 16 March 2019 / Published: 20 March 2019
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Abstract
Forest growing stock volume (GSV) extraction using synthetic aperture radar (SAR) images has been widely used in climate change research. However, the relationships between forest GSV and polarimetric SAR (PolSAR) data in the mountain region of central China remain unknown. Moreover, it is [...] Read more.
Forest growing stock volume (GSV) extraction using synthetic aperture radar (SAR) images has been widely used in climate change research. However, the relationships between forest GSV and polarimetric SAR (PolSAR) data in the mountain region of central China remain unknown. Moreover, it is challenging to estimate GSV due to the complex topography of the region. In this paper, we estimated the forest GSV from advanced land observing satellite-2 (ALOS-2) phased array-type L-band synthetic aperture radar (PALSAR-2) full polarimetric SAR data based on ground truth data collected in Youxian County, Central China in 2016. An integrated three-stage (polarization orientation angle, POA; effective scattering area, ESA; and angular variation effect, AVE) correction method was used to reduce the negative impact of topography on the backscatter coefficient. In the AVE correction stage, a strategy for fine terrain correction was attempted to obtain the optimum correction parameters for different polarization channels. The elements on the diagonal of covariance matrix were used to develop forest GSV prediction models through five single-variable models and a multi-variable model. The results showed that the integrated three-stage terrain correction reduced the negative influence of topography and improved the sensitivity between the forest GSV and backscatter coefficients. In the three stages, the POA compensation was limited in its ability to reduce the impact of complex terrain, the ESA correction was more effective in low-local incidence angles area than high-local incidence angles, and the effect of the AVE correction was opposite to the ESA correction. The data acquired on 14 July 2016 was most suitable for GSV estimation in this study area due to its correlation with GSV, which was the strongest at HH, HV, and VV polarizations. The correlation coefficient values were 0.489, 0.643, and 0.473, respectively, which were improved by 0.363, 0.373, and 0.366 in comparison to before terrain correction. In the five single-variable models, the fitting performance of the Water-Cloud analysis model was the best, and the correlation coefficient R2 value was 0.612. The constructed multi-variable model produced a better inversion result, with a root mean square error (RMSE) of 70.965 m3/ha, which was improved by 22.08% in comparison to the single-variable models. Finally, the space distribution map of forest GSV was established using the multi-variable model. The range of estimated forest GSV was 0 to 450 m3/ha, and the mean value was 135.759 m3/ha. The study expands the application potential of PolSAR data in complex topographic areas; thus, it is helpful and valuable for the estimation of large-scale forest parameters. Full article
(This article belongs to the Special Issue Remote Sensing Technology Applications in Forestry and REDD+)
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Open AccessArticle
Genome-Wide Identification and Transcriptional Expression Profiles of the F-box Gene Family in Common Walnut (Juglans regia L.)
Forests 2019, 10(3), 275; https://doi.org/10.3390/f10030275
Received: 10 February 2019 / Revised: 13 March 2019 / Accepted: 15 March 2019 / Published: 20 March 2019
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Abstract
The common walnut (or Persian walnut), Juglans regia L., is an economically important temperate tree species valued for both its edible nut and high-quality wood. F-box gene family members are involved in plant development, which includes regulating plant development, reproduction, cellular protein degradation, [...] Read more.
The common walnut (or Persian walnut), Juglans regia L., is an economically important temperate tree species valued for both its edible nut and high-quality wood. F-box gene family members are involved in plant development, which includes regulating plant development, reproduction, cellular protein degradation, response to biotic and abiotic stresses, and flowering. However, in common walnut (J. regia), there are no reports about the F-box gene family. Here, we report a genome-wide identification of J. regia F-box genes and analyze their phylogeny, duplication, microRNA, pathway, and transcriptional expression profile. In this study, 74 F-box genes were identified and clustered into three groups based on phylogenetic analysis and eight subfamilies based on special domains in common walnut. These common walnut F-box genes are distributed on 31 different pseudo-chromosomes. The gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and microRNA profiles showed that the F-box gene family might play a critical role in the flowering of common walnut. The expressions were significantly higher in female flowers and male flowers compared with leaf and hull tissues at a transcriptome level. The results revealed that the expressions of the F-box gene in female flowers were positively correlated with male flowers, but there was no correlation between any other tissue combinations in common walnut. Our results provided insight into the general characteristics of the F-box genes in common walnut. Full article
(This article belongs to the Section Forest Ecophysiology and Biology)
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Open AccessArticle
Effects of Hygrothermal Environment in Cooling Towers on the Chemical Composition of Bamboo Grid Packing
Forests 2019, 10(3), 274; https://doi.org/10.3390/f10030274
Received: 28 February 2019 / Revised: 15 March 2019 / Accepted: 16 March 2019 / Published: 19 March 2019
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Abstract
Bamboo grid packing (BGP) is a new kind of cooling packing, used in some Chinese hyperbolic cooling towers, which has excellent potential to complement or replace cooling packing made of polyvinyl chloride (PVC), cement, and glass fiber-reinforced plastic. For bamboo applications, mechanical properties [...] Read more.
Bamboo grid packing (BGP) is a new kind of cooling packing, used in some Chinese hyperbolic cooling towers, which has excellent potential to complement or replace cooling packing made of polyvinyl chloride (PVC), cement, and glass fiber-reinforced plastic. For bamboo applications, mechanical properties and service life are matters of concern; this is strongly associated with bamboo’s chemical composition and mass loss. To better understand the mechanics of mechanical property deterioration and service life reduction, this study investigated the effects of hygrothermal environments in cooling towers on the chemical and elemental composition, mass loss, Fourier-transform infrared (FTIR) spectrum, and color changes of BGP. The results showed that BGP that had been in service for nine years in cooling towers exhibited major decreases in content of hemicellulose and benzene-ethanol extractives, as well as a significant increases in the content of α-cellulose and lignin. Exposure to the hygrothermal environment led to a decrease of oxygen content and around 8% mass loss, as well as an increase in carbon content compared to control samples. The hot water flow in cooling towers not only hydrolyzed hemicellulose, but also degraded some functional groups in cellulose and lignin. The lightness (L*) and chromaticity (a* and b*) parameters of the used BGP all decreased, except for the a* value of the outer skin. The total color change (ΔE*) of the inner skin of used BGP exceeded that of the outer skin. Full article
(This article belongs to the Special Issue Wood Properties and Processing)
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Open AccessReview
Acquisition of Forest Attributes for Decision Support at the Forest Enterprise Level Using Remote-Sensing Techniques—A Review
Forests 2019, 10(3), 273; https://doi.org/10.3390/f10030273
Received: 10 February 2019 / Revised: 8 March 2019 / Accepted: 15 March 2019 / Published: 19 March 2019
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Abstract
In recent decades, remote sensing techniques and the associated hardware and software have made substantial improvements. With satellite images that can obtain sub-meter spatial resolution, and new hardware, particularly unmanned aerial vehicles and systems, there are many emerging opportunities for improved data acquisition, [...] Read more.
In recent decades, remote sensing techniques and the associated hardware and software have made substantial improvements. With satellite images that can obtain sub-meter spatial resolution, and new hardware, particularly unmanned aerial vehicles and systems, there are many emerging opportunities for improved data acquisition, including variable temporal and spectral resolutions. Combined with the evolution of techniques for aerial remote sensing, such as full wave laser scanners, hyperspectral scanners, and aerial radar sensors, the potential to incorporate this new data in forest management is enormous. Here we provide an overview of the current state-of-the-art remote sensing techniques for large forest areas thousands or tens of thousands of hectares. We examined modern remote sensing techniques used to obtain forest data that are directly applicable to decision making issues, and we provided a general overview of the types of data that can be obtained using remote sensing. The most easily accessible forest variable described in many works is stand or tree height, followed by other inventory variables like basal area, tree number, diameters, and volume, which are crucial in decision making process, especially for thinning and harvest planning, and timber transport optimization. Information about zonation and species composition are often described as more difficult to assess; however, this information usually is not required on annual basis. Counts of studies on forest health show an increasing trend in the last years, mostly in context of availability of new sensors as well as increased forest vulnerability caused by climate change; by virtue to modern sensors interesting methods were developed for detection of stressed or damaged trees. Unexpectedly few works focus on regeneration and seedlings evaluation; though regenerated stands should be regularly monitored in order to maintain forest cover sustainability. Full article
(This article belongs to the Special Issue Forest Landscape Management: From Data to Decision)
Open AccessArticle
Amazon Fund 10 Years Later: Lessons from the World’s Largest REDD+ Program
Forests 2019, 10(3), 272; https://doi.org/10.3390/f10030272
Received: 27 December 2018 / Revised: 12 February 2019 / Accepted: 26 February 2019 / Published: 19 March 2019
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Abstract
Results-Based Funding (RBF) for Reducing Emissions from Deforestation and Forest Degradation (REDD+) has become an important instrument for channeling financial resources to forest conservation activities. At the same time, much literature on conservation funding is ambiguous about the effectiveness of existing RBF schemes. [...] Read more.
Results-Based Funding (RBF) for Reducing Emissions from Deforestation and Forest Degradation (REDD+) has become an important instrument for channeling financial resources to forest conservation activities. At the same time, much literature on conservation funding is ambiguous about the effectiveness of existing RBF schemes. Many effectiveness evaluations follow a simplified version of the principal-agent model, but in practice, the relation between aid providers and funding recipients is much more complex. As a consequence, intermediary steps of conservation funding are often not accounted for in effectiveness studies. This research paper aims to provide a nuanced understanding of conservation funding by analyzing the allocation of financial resources for one of the largest RBF schemes for REDD+ in the world: the Brazilian Amazon Fund. As part of this analysis, this study has built a dataset of information, with unprecedented detail, on Amazon Fund projects, in order to accurately reconstruct the allocation of financial resources across different stakeholders (i.e., governments, NGOs, research institutions), geographies, and activities. The results show that that the distribution of resources of the Amazon Fund lack a clear strategy that could maximize the results of the fund in terms of deforestation reduction. First, there are evidences that in some cases governmental organizations lack financial additionality for their projects, which renders the growing share of funding to this type of stakeholder particularly worrisome. Second, the Amazon Fund allocations did also not systematically have privileged the municipalities that showed the recent highest deforestation rates. rom the 10 municipalities with the higher deforestation rates in 2017, only 2 are amongst the top 100 receiving per/Ha considering the 775 municipalities from Legal Amazon. Third, the allocation of the financial resources from the Amazon Fund reflects the support of different projects that adopt significantly diverging theories of change, many of which are not primarily concerned with attaining further deforestation reductions. These results reflect the current approach adopted by the Amazon Fund, that do not actively seek areas for intervention, but instead wait for project submissions from proponents. As a consequence, project owners exert much influence on to the type of activities that they support how deforestation reduction is expected to be attained. The article concludes that the Amazon Fund as well as other RBF programs, should evolve over time in order to develop a more targeted funding strategy to maximize the long-term impact in reducing emissions from deforestation. Full article
(This article belongs to the Special Issue The Performance of REDD+: From Global Governance to Local Practices)
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Open AccessArticle
Immediate and Delayed Effects of Severe Winds on an Old-Growth Forest in Kentucky: A Forty-Year Retrospective
Forests 2019, 10(3), 271; https://doi.org/10.3390/f10030271
Received: 22 February 2019 / Revised: 13 March 2019 / Accepted: 15 March 2019 / Published: 19 March 2019
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Abstract
Wind disturbance is an important factor that can affect the development of the forests of the Central Hardwood Region of the United States. However, there have been few long-term studies of the recovery of these systems following wind damage. Long-term studies of protected [...] Read more.
Wind disturbance is an important factor that can affect the development of the forests of the Central Hardwood Region of the United States. However, there have been few long-term studies of the recovery of these systems following wind damage. Long-term studies of protected forest systems, such as Dinsmore Woods in Northern Kentucky, within the fragmented forest of this region are valuable as they provide a resource to document and understand the effect of both abiotic and biotic challenges to forest systems. This study is a 40-year analysis of both overstory and understory changes in the forest system at Dinsmore Woods as the result of damage caused by severe winds in the spring of 1974. The forest was surveyed before and immediately following the windstorm and then at 10-year intervals. Although the windstorm had an immediate effect on the forest, the pattern of damage was complex. The forest canopy (diameter at breast height (DBH) ≥ 30 cm) experienced an irregular pattern of damage while in the subcanopy (DBH ≤ 30 cm) there was a 25% reduction in total basal area. However, the major effects of the windstorm were delayed and subsequently have altered forest recovery. Ten years following the disturbance declines were seen in total density and basal area in the canopy and subcanopy of the forest as a consequence of windstorm damage. In the past 20 years the total basal area of the canopy has increased and exceeds the pre-disturbance total basal area. In contrast, the subcanopy total basal area continued to decline 20 years post-disturbance and has not recovered. Further openings in the canopy and subcanopy due to the delayed windstorm effects helped to establish a dense understory of native shrubs and sugar maple which have affected tree regeneration and is reflected in the continual decline in species diversity in the subcanopy and sapling strata over the 40-year period. Full article
(This article belongs to the Section Forest Ecology and Management)
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Open AccessArticle
Implementing Climate Change and Associated Future Timber Price Trends in a Decision Support System Designed for Irish Forest Management and Applied to Ireland’s Western Peatland Forests
Forests 2019, 10(3), 270; https://doi.org/10.3390/f10030270
Received: 31 January 2019 / Revised: 12 March 2019 / Accepted: 14 March 2019 / Published: 18 March 2019
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Abstract
Research Highlights: Predicting impacts on forest management of Climate Change (CC) and dynamic timber prices by incorporating these external factors in a Forest Management Decision Support System (FMDSS). Background and Objectives: Forest managers must comply with Sustainable Forest Management (SFM) practices, including considering [...] Read more.
Research Highlights: Predicting impacts on forest management of Climate Change (CC) and dynamic timber prices by incorporating these external factors in a Forest Management Decision Support System (FMDSS). Background and Objectives: Forest managers must comply with Sustainable Forest Management (SFM) practices, including considering the long-term impacts that CC and the bioeconomy may have on their forests and their management. The aims of this study are: (1) incorporate the effects of CC and Dynamic Prices (DP) in a FMDSS that was developed for Ireland’s peatland forests, (2) analyse the impact of global climate and market scenarios on forest management and forest composition at the landscape level. Materials and Methods: Remsoft Woodstock is a strategic planning decision support system that is widely used for forest management around the world. A linear programming model was developed for Ireland’s Western Peatland forests while using Woodstock. Data from Climadapt, which is an expert-based decision support system that was developed in Ireland, were used to include CC effects on forest productivity and species suitability. Dynamic market prices were also included to reflect the changing demands for wood fibre as part of the European Union (EU) and global effort to mitigate CC. Results: DP will likely have more impact on harvest patterns, volumes, and net present value than CC. Higher assortment prices, especially for pulpwood, stimulate the harvesting of forests on marginal sites and off-set some of the negative CC growth impacts on forest profitability. Conclusions: Incorporating CC and bioeconomy prices in a forest decision support system is feasible and recommendable. Foresters should incorporate the expected global changes in their long-term management planning to mitigate the negative effects that un-informed management decisions can have on the sustainability of their forests. Full article
(This article belongs to the Special Issue Forest Landscape Management: From Data to Decision)
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Open AccessArticle
The Effects of Copper and Silver Nanoparticles on Container-Grown Scots Pine (Pinus sylvestris L.) and Pedunculate Oak (Quercus robur L.) Seedlings
Forests 2019, 10(3), 269; https://doi.org/10.3390/f10030269
Received: 13 February 2019 / Revised: 12 March 2019 / Accepted: 14 March 2019 / Published: 17 March 2019
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Abstract
Metal nanoparticles (NPs) are finding ever-wider applications in plant production (agricultural and forestry-related) as fertilisers, pesticides and growth stimulators. This makes it essential to examine their impact on a variety of plants, including trees. In the study detailed here, we investigated the effects [...] Read more.
Metal nanoparticles (NPs) are finding ever-wider applications in plant production (agricultural and forestry-related) as fertilisers, pesticides and growth stimulators. This makes it essential to examine their impact on a variety of plants, including trees. In the study detailed here, we investigated the effects of nanoparticles of silver and copper (i.e., AgNPs and CuNPs) on growth, and chlorophyll fluorescence, in the seedlings of Scots pine and pedunculate oak. We also compared the ultrastructure of needles, leaves, shoots and roots of treated and untreated plants, under transmission electron microscopy. Seedlings were grown in containers in a peat substrate, prior to the foliar application of NPs four times in the course of the growing season, at the four concentrations of 0, 5, 25 and 50 ppm. We were able to detect species-specific activity of the two types of NP. Among seedling pines, the impact of both types of NP at the concentrations supplied limited growth slightly. In contrast, no such effect was observed for the oaks grown in the trial. Equally, it was not possible to find ultrastructural changes in stems and roots associated with the applications of NPs. Cell organelles apparently sensitive to the action of both NPs (albeit only at the highest applied concentration of 50 ppm) were chloroplasts. The CuNP-treated oaks contained large plastoglobules, whereas those dosed with AgNP contained large starch granules. The NP-treated pines likewise exhibited large numbers of plastoglobules, while the chloroplasts of NP-treated plants in general presented shapes that changed from lenticular to round. In addition, large osmophilic globules were present in the cytoplasm. Reference to maximum quantum yields from photosystem II (Fv/Fm)—on the basis of chlorophyll a fluorescence measurements—revealed a slight debilitation of oak seedlings following the application of both kinds of NP at higher concentrations. In contrast, in pines, this variable revealed no influence of AgNPs, as well as a favourable effect due to the CuNPs applied at a concentration of 5 ppm. Our research also showed that any toxic impact on pine or oak seedlings due to the NPs was limited and only present with higher concentrations. Full article
(This article belongs to the Section Forest Ecophysiology and Biology)
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Open AccessArticle
Artificial Neural Networks and Linear Regression Reduce Sample Intensity to Predict the Commercial Volume of Eucalyptus Clones
Forests 2019, 10(3), 268; https://doi.org/10.3390/f10030268
Received: 12 January 2019 / Revised: 21 February 2019 / Accepted: 7 March 2019 / Published: 17 March 2019
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Abstract
Equations to predict Eucalyptus timber volume are continuously updated, but most of them cannot be used for certain locations. Thus, equations of similar strata are applied to clonal plantations where trees cannot be felled to fit volumetric models. The objective of this study [...] Read more.
Equations to predict Eucalyptus timber volume are continuously updated, but most of them cannot be used for certain locations. Thus, equations of similar strata are applied to clonal plantations where trees cannot be felled to fit volumetric models. The objective of this study was to use linear regression and artificial neural networks (ANN) to reduce the number of trees sampled while maintaining the accuracy of commercial volume predictions with bark up to 4 cm in diameter at the top (v) of Eucalyptus clones. Two methods were evaluated in two scenarios: (a) regression model fit and ANN training with 80% of the data (533 trees) and per clone group with 80% of the trees in each group; and (b) model fit and ANN training with trees of only one clone group at ages two and three, with sample intensities of six, five, four, three, two, and one tree per diameter class. The real and predicted v averages did not differ in sample intensities from six to two trees per diameter class with different methods. The frequency distribution of individuals by volume class by the two methods (regression and ANN) compared to the real values were similar in scenarios (a) and (b) by the Kolmogorov–Smirnov test (p-value > 0.01). The application of ANN was more effective for total data analysis with non-linear behavior, without sampled environment stratification. The Prodan model also generates estimates with accuracy, and, among the regression models, is the best fit to the data. The volume with bark up to 4 cm in diameter at the top of Eucalyptus clones can be predicted with at least three trees per diameter class with regression (root mean square error in percentage, RMSE = 12.32%), and at least four trees per class with ANN (RMSE = 11.73%). Full article
(This article belongs to the Section Forest Inventory, Quantitative Methods and Remote Sensing)
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Open AccessCommunication
Some Lessons Learned on Early Survival and Growth of Containerized, Locally-Sourced Ponderosa Pine Seedlings in the Davis Mountains of Western Texas, US
Forests 2019, 10(3), 267; https://doi.org/10.3390/f10030267
Received: 15 February 2019 / Revised: 13 March 2019 / Accepted: 13 March 2019 / Published: 16 March 2019
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Abstract
The ponderosa pine forests in the Davis Mountains of western Texas recently experienced a major mortality event caused, in part, by an extended regional drought that predisposed trees and stands to mortality from both western pine beetle and wildfires. The loss of many [...] Read more.
The ponderosa pine forests in the Davis Mountains of western Texas recently experienced a major mortality event caused, in part, by an extended regional drought that predisposed trees and stands to mortality from both western pine beetle and wildfires. The loss of many overstory pines and the scarcity of natural ponderosa pine regeneration pose a considerable challenge to restoration. A commissioned study investigated artificial regeneration using containerized ponderosa pine seedlings with multiple planting seasons and vegetation management alternatives. Early survival was statistically greater for dormant season plantings than monsoon season plantings. Vegetation management treatments influenced early growth, survival, and herbivory rates. Physical weed control, which consisted of fibrous weed mats around the base of planted seedlings, showed early advantages over some vegetation management treatments in growth, survival and herbivory deterrence, but all vegetation management treatments had similar survival and herbivory results after 2.5 years. Early survival was poor in all treatments, mainly due to herbivory, which was identified as the principal short-term obstacle to artificial regeneration of ponderosa pine in the Davis Mountains. The larger question regarding feasibility of recovery in this isolated population, particularly if local climatic conditions become increasingly unfavorable, remains. Full article
(This article belongs to the Special Issue Forest Post-Fire Regeneration)
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Open AccessArticle
Contrasting Species Diversity and Values in Home Gardens and Traditional Parkland Agroforestry Systems in Ethiopian Sub-Humid Lowlands
Forests 2019, 10(3), 266; https://doi.org/10.3390/f10030266
Received: 5 February 2019 / Revised: 9 March 2019 / Accepted: 11 March 2019 / Published: 15 March 2019
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Abstract
Understanding the complex diversity of species and their potential uses in traditional agroforestry systems is crucial for enhancing the productivity of tropical systems and ensuring the sustainability of the natural resource base. The aim of this study is the evaluation of the role [...] Read more.
Understanding the complex diversity of species and their potential uses in traditional agroforestry systems is crucial for enhancing the productivity of tropical systems and ensuring the sustainability of the natural resource base. The aim of this study is the evaluation of the role of home gardens and parklands, which are prominent tropical agroforestry systems, in the conservation and management of biodiversity. Our study quantified and compared the diversity of woody and herbaceous perennial species and their uses in traditional home gardens and parkland agroforestry systems under a sub-humid climate in western Ethiopia. A sociological survey of 130 household respondents revealed 14 different uses of the species, mostly for shade, fuelwood, food, and as traditional medicine. Vegetation inventory showed that the Fisher’s α diversity index and species richness were significantly higher in home gardens (Fisher’s α = 5.28 ± 0.35) than in parklands (Fisher’s α = 1.62 ± 0.18). Both systems were significantly different in species composition (Sørenson’s similarity coefficient = 35%). The differences occurred primarily because of the high intensity of management and the cultivation of exotic tree species in the home gardens, whereas parklands harbored mostly native flora owing to the deliberate retention and assisted regeneration by farmers. In home gardens, Mangifera indica L. was the most important woody species, followed by Cordia africana Lam. and Coffea arabica L. On the other hand, Syzygium guineense Wall. was the most important species in parklands, followed by C. africana and M. indica. The species diversity of agroforestry practices must be further augmented with both indigenous and useful, non-invasive exotic woody and herbaceous species, particularly in parklands that showed lower than expected species diversity compared to home-gardens. Full article
(This article belongs to the Special Issue Causes and Consequences of Species Diversity in Forest Ecosystems)
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Open AccessArticle
Functional Crown Architecture of Five Temperate Broadleaf Tree Species: Vertical Gradients in Leaf Morphology, Leaf Angle, and Leaf Area Density
Forests 2019, 10(3), 265; https://doi.org/10.3390/f10030265
Received: 6 February 2019 / Revised: 8 March 2019 / Accepted: 8 March 2019 / Published: 15 March 2019
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Abstract
The morphology, inclination, and spatial distribution of leaves in different parts of tree crowns are important determinants of the radiation, momentum, and gas exchange between the canopy and the atmosphere. However, it is not well known how these foliage-related traits vary among species [...] Read more.
The morphology, inclination, and spatial distribution of leaves in different parts of tree crowns are important determinants of the radiation, momentum, and gas exchange between the canopy and the atmosphere. However, it is not well known how these foliage-related traits vary among species differing in successional status. We measured leaf size, leaf mass area (LMA), leaf inclination (angle to the horizontal), leaf area density (LAD), total leaf area (leaf area index, LAI), and leaf area distribution across the crown in adult trees of five common, early to late-successional tree species (Betula pendula Roth, Quercus petraea (Matt.) Liebl., Carpinus betulus L., Tilia cordata Mill., and Fagus sylvatica L.) using different canopy access techniques and the harvest of foliated trees (29 trees in total). Leaf size increased continuously with crown depth in B. pendula and T. cordata but peaked at mid-crown in Q. petraea, C. betulus, and F. sylvatica to decrease toward the shade crown. By contrast, LMA and leaf angle decreased continuously with crown depth in all species, but the pattern of vertical change varied. The mid/late- and late-successional species had higher LAI, lower shade-leaf LMA, lower leaf angles (shade and sun crown), and higher LAD in the uppermost sun crown in comparison to early successional B. pendula. We assume that the most peripheral sun leaf layer is partly acting as a shield against excess radiation, with foliage properties depending on the structure of the shade crown. We conclude that the vertical change in leaf morphology, inclination, and spatial distribution in tree crowns is highly species specific, with partial dependence on the species’ position in succession. Full article
(This article belongs to the Special Issue Tree Crown Dynamics and Morphology)
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Open AccessArticle
Effect of Drought on Outbreaks of Major Forest Pests, Pine Caterpillars (Dendrolimus spp.), in Shandong Province, China
Forests 2019, 10(3), 264; https://doi.org/10.3390/f10030264
Received: 24 January 2019 / Revised: 7 March 2019 / Accepted: 8 March 2019 / Published: 15 March 2019
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Abstract
As the main defoliators of coniferous forests in Shandong Province, China, pine caterpillars (including Dendrolimus suffuscus suffuscus Lajonquiere, D. spectabilis Butler, and D. tabulaeformis Tsai et Liu) have caused substantial forest damage, adverse economic impacts, and losses of ecosystem resources. Therefore, elucidating the [...] Read more.
As the main defoliators of coniferous forests in Shandong Province, China, pine caterpillars (including Dendrolimus suffuscus suffuscus Lajonquiere, D. spectabilis Butler, and D. tabulaeformis Tsai et Liu) have caused substantial forest damage, adverse economic impacts, and losses of ecosystem resources. Therefore, elucidating the effects of drought on the outbreak of these pests is important for promoting forestry production and ecological reconstruction. Accordingly, the aim of the present study was to analyse the spatiotemporal variation of drought in Shandong Province, using the Standard Precipitation Index, and to investigate the impact of drought on the outbreak of pine caterpillar infestations. Future trends in drought and pine caterpillar populations were then estimated using the Hurst exponent. The results showed that: (1) Drought decreased gradually and showed a wetting trend from 1981 to 2012, with frequency decreasing on a decadal scale as follows: 1980s > 1990s > 2000s > 2010s; (2) The total area of pine caterpillar occurrence decreased strongly from 1992 to 2012; (3) Long-term or prolonged drought had a greater positive impact on pine caterpillar outbreak than short-term drought; (4) In the future, a greater portion of the province’s area will experience increased wetting conditions (57%) than increased drought (43%), and the area of pine caterpillar outbreak is estimated to decrease overall. These findings help elucidate the relationship between drought and pine caterpillar outbreak in Shandong Province and, hence, provide a basis for developing preventive measures and plans. Full article
(This article belongs to the Special Issue Dieback on Drought-Prone Forest Ecosystems)
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Open AccessArticle
Host Phylogenetic Relatedness and Soil Nutrients Shape Ectomycorrhizal Community Composition in Native and Exotic Pine Plantations
Forests 2019, 10(3), 263; https://doi.org/10.3390/f10030263
Received: 1 March 2019 / Revised: 12 March 2019 / Accepted: 12 March 2019 / Published: 15 March 2019
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Abstract
Exotic non-native Pinus species have been widely planted or become naturalized in many parts of the world. Pines rely on ectomycorrhizal (ECM) fungi mutualisms to overcome barriers to establishment, yet the degree to which host specificity and edaphic preferences influence ECM community composition [...] Read more.
Exotic non-native Pinus species have been widely planted or become naturalized in many parts of the world. Pines rely on ectomycorrhizal (ECM) fungi mutualisms to overcome barriers to establishment, yet the degree to which host specificity and edaphic preferences influence ECM community composition remains poorly understood. In this study, we used high-throughput sequencing coupled with soil analyses to investigate the effect of host plant identity, spatial distance and edaphic factors on ECM community composition in young (30-year-old) native (Pinus massoniana Lamb.) and exotic (Pinus elliottii Engelm.) pine plantations in China. The ECM fungal communities comprised 43 species with the majority belonging to the Thelephoraceae and Russulaceae. Most species were found associated with both host trees while certain native ECM taxa (Suillus) showed host specificity to the native P. massoniana. ECM fungi that are known to occur exclusively with Pinus (e.g., Rhizopogon) were uncommon. We found no significant effect of host identity on ECM communities, i.e., phylogenetically related pines shared similar ECM fungal communities. Instead, ECM fungal community composition was strongly influenced by site-specific abiotic factors and dispersal. These findings reinforce the idea that taxonomic relatedness might be a factor promoting ECM colonization in exotic pines but that shifts in ECM communities may also be context-dependent. Full article
(This article belongs to the Special Issue The Ecology of Fine Roots and Mycorrhizas in Forests)
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