Shrub Density Research Articles

Potential of Multitemporal Lidar for the Detection of Subtle Archaeological Features under Perennial Dense Forest

This paper presents a method for the merging of lidar-derived point clouds of the same area taken at different moments, even when these are not co-registered. The workflow also incorporates the filtering of vegetation allowing the classification of unclassified point clouds using the ground points of reliable coverages. The objective is to produce a digital terrain model by joining all ground points to generate a higher resolution model than would have been possible using a single coverage. The workflow is supplemented by a multi-scale relief visualisation tool that allows for better detection of archaeological micro-reliefs of variable size even in areas of complex topography. The workflow is tested in six Iberian Iron Age sites, all of them located in mountain areas with dense Mediterranean perennial forests and shrub vegetation.

Use of Mobile Laser Scanning (MLS) to Monitor Vegetation Recovery on Linear Disturbances

Seismic lines are narrow, linear corridors cleared through forests for oil and gas exploration. Their inconsistent recovery has led to Alberta’s forests being highly fragmented, resulting in the need for seismic line restoration programs and subsequent monitoring. Light detection and ranging (LiDAR) is becoming an increasingly popular technology for the fast and accurate measurement of forests. Mobile LiDAR scanners (MLS) are emerging as an alternative to traditional aerial LiDAR due to their increased point cloud density. To determine whether MLS could be effective for collecting vegetation data on seismic lines, we sampled 17 seismic lines using the Emesent Hovermap™ in leaf-on and leaf-off conditions. Processing the LiDAR data was conducted with GreenValley International’s LiDAR 360 software, and data derived from the point clouds were compared to physically measured field data. Overall, the tree detection algorithm was unsuccessful at accurately segmenting the point clouds. Complex vegetation environments on seismic lines, including small conifers with obscured stems or extremely dense and tall shrubs with overlapping canopies, posed a challenge for the software’s capacity to differentiate trees As a result, tree densities and diameters were overestimated, while tree heights were underestimated. Exploration of alternative algorithms and software is needed if measuring vegetation data on seismic lines with MLS is to be implemented.

Florida sandhill crane use and nesting in managed dry prairie

Florida sandhill crane use and nesting in managed dry prairie

Predator avoidance influences selection of neonatal lambing habitat by Sierra Nevada bighorn sheep

AbstractTo improve lifetime reproductive success, maternal ungulates should pursue behavioral strategies that reduce risk of offspring mortality. Predation is a leading cause of neonatal mortality; thus, maternal ungulates should select habitat that reduces risk of predation on vulnerable neonates. We examined selection of habitat across subpopulations of federally endangered Sierra Nevada bighorn sheep (Ovis canadensis sierrae) within Sierra Nevada, California, USA, 2008–2018. Our objectives were to understand how maternal Sierra Nevada bighorn minimize risk of predation through selection of habitat and to quantify current and future potential neonatal habitat across the Sierra Nevada. Mountain lions (Puma concolor) are the predominant predators of adult Sierra Nevada bighorn; thus, we hypothesized females would select habitat that minimized risk of predation from mountain lions. We developed a used‐available resource selection function to quantify patterns of habitat selection and produced predictive maps identifying highly selected lambing habitat across the Sierra Nevada. Our top model demonstrated females selected habitat where the relative probability of encountering mountain lions was low and near escape terrain. Selection for vegetation type was dependent on risk of encounter with mountain lions; when risk of encounter was low, females selected shrub cover. This suggests that when risk of encountering mountain lions was low, females may have selected areas with dense shrubs to reduce risk of being detected by other predators such as coyotes (Canis latrans) and golden eagles (Aquila chrysaetos). As risk of encountering mountain lions increased, females avoided all vegetation types other than barren, suggesting that despite increased risk of encounter, females may have been able to mitigate overall mortality risk by selecting habitat where approaching mountain lions could be detected and avoided. Our predictive models and resulting maps demonstrate differences in prevalence and connectivity of highly selected lambing habitat across subpopulations, which may explain differences in lamb recruitment and adequacy of lambing habitat observed among subpopulations. Recolonization into historical ranges and increasing connectivity between Sierra Nevada bighorn subpopulations is an important conservation need for species recovery and long‐term viability of fragmented subpopulations.

Microhabitat selection of blue eared pheasant (Crossoptilon auritum) during breeding period in Helan Mountains, China

Habitat degradation and fragmentation are crucial factors which result in biodiversity loss among the world. Understanding how species respond to the habitat change is helpful and essential for the conservation of the endangered ones. Therefore, the aim of current study is to explore how to carry out biodiversity conservation from the perspective of the habitat selection of species. We studied the microhabitat selection of blue eared pheasant ( Crossoptilon auritum) during its breeding time (including mating, incubation, and feeding periods). The field research was carried out from April to August in 2014 at Helan Mountains, China. Six nests of blue eared pheasants were found; 323 used plots and 171 control plots were recorded. Results indicated that blue eared pheasants prefer mountainous coniferous forest at shady slope with domination of Picea crassifolia, and its habitat selection was mainly influenced by shrub density, tree density, altitude, slope degree, hiding cover, water resource, and human disturbance. However, there were slight differences among the three periods. Our study firstly compared factors that affect the microhabitat selection of blue eared pheasants among the three periods of its breeding time. Meanwhile, combining the current study with the previous ones, specific strategies could be applied on the works of endangered species and biodiversity conservation.

Insectivorous Bats in Eastern Mediterranean Planted Pine Forests—Effects of Forest Structure on Foraging Activity, Diversity, and Implications for Management Practices

Bats are primarily forest mammals and forest structure may affect their communities through the level of vegetation clutter. Pine plantations are typically even-aged managed forests that lack structural complexity. However, an understory layer can enhance the heterogeneity of these forests, making them suitable for several animal taxa. We hypothesized that species composition, richness, and foraging activity of insectivorous bats in pine plantations vary according to forest structure, specifically with the density of the understory. We measured pine density, Diameter at Breast Height (DBH), canopy closure, and vegetation cover of 29 pine (Pinus halepensis) plantations of the Judean Lowlands, Israel, and collected acoustic data on resident bats. We found that bat species richness and total activity increased in forests with large tree DBH and dense shrubs. Cluttered-habitat species foraged preferentially in forests with large tree DBH and high pine density, while open-habitat species preferred forests with well-developed canopies and dense shrubs. Pipistrellus pipistrellus and Eptesicus serotinus foraged in mature forests with well-developed bushes and these species are endangered in Israel. We conclude that mature planted pine forests with a well-developed under-canopy are suitable foraging grounds for insectivorous bats. Management plans for planted pine forests should consider our findings to support bat populations, including rare and endangered species.

Responses of birds to vineyard abandonment in Slovakia

Vineyards are semi-natural, human-modified ecosystems where the extent of natural elements is determined primarily by the type of management and by the abandonment rate. In this study, we analyzed bird assemblages in 40 vineyard plots in six wine-growing regions of Slovakia. We examined bird communities on managed and abandoned vineyards to identify possible patterns. Environmental and spatial predictors of species richness and abundance were analyzed using partial redundancy analysis (pRDA) and a generalized additive model (GAM). Bird communities were influenced by both environmental and spatial factors. As expected, elevation explained most of the variation in bird assemblages. Tree coverage was found to be more important than the vineyard abandonment rate in explaining the observed variability. Only a portion of the variance in the species data reported by pRDA was accounted for by the difference in vineyard abandonment degree. Our results show that the species richness of all birds was positively correlated to vegetation density (captured by NDVI). Herb and shrub cover had less effect on bird species richness than tree cover and the presence of traditional agricultural vineyard landscapes. However, shrub density emerged as a key explanatory factor for the abundance of habitat specialists. Our study shows that, depending on whether the goal is to promote the diversity and abundance of farmland or non-farmland bird species, different conservation biology approaches should be used. Increasing the landscape diversity and avoiding large vineyard abandonment are necessary if we are to stem the decline of valuable farmland species. • The area of managed vineyards in Slovakia continues to decrease. • The species richness of all birds positively correlated to NDVI. • Tree coverage was found to be one of the most important factors in explaining bird species variation. • The shrub density turned out to be a key explanatory factor of habitat specialist abundance. • Bird abundance and species richness increased continuously with the presence of the traditional agricultural landscape.

Contribution of species and functional richness to carbon storage in eucalypt woodland restoration

Biologically diverse forest and woodland restoration can mitigate climate change and biodiversity loss. Understanding the trade-off between carbon storage and biodiversity is important to maximise the value of restoration opportunities. Ecological theory suggests biological diversity contributes positively to carbon storage until the relationship plateaus (i.e., species are added with no effect on carbon storage), and yet in practice, tree monocultures are perceived to sequester more carbon than diverse plantings. Here, we measured the contribution of plant diversity to carbon storage in trees and shrubs ten years after planting for yate (Eucalyptus occidentalis) woodland restoration. We found no evidence for a trade-off between carbon storage and plant diversity. We planted yate with mixes of yate woodland species including native grasses, shrubs, and trees. Ten years after planting, grass establishment was poor, and density of trees and shrubs was patchy. There was some unassisted recruitment of woody species. Diversity was measured as observed species richness and observed functional richness, which incorporated taxonomic diversity, structural diversity, and presence/absence of nitrogen-fixing legumes. Carbon stocks measured were above and belowground tree and shrub biomass, leaf and twig litter biomass, and organic carbon (%) in the topsoil. Across all three carbon stocks diverse yate plantings sequestered as much carbon as yate monocultures. Observed species richness had a weak negative effect on tree and shrub biomass in the best linear mixed model but this effect diminished with the removal of an outlier. Tree density had a positive effect on tree and shrub biomass in models with and without the outlier. There was no effect of diversity on litter biomass and soil organic carbon. Instead, linear mixed models of these stocks showed the influence of soil properties. Litter biomass increased with soil potassium and decreased with soil pH. Soil organic carbon increased with initial soil organic carbon and soil nitrogen. There are potential additional biodiversity benefits of diverse plantings that we did not measure (e.g., soil erosion control, wildlife habitat). We call for more field experiments to explore these potential benefits and to generate the ecological knowledge needed to improve the quality of global forest and woodland restoration efforts.

Recommendations to enhance breeding bird diversity in managed plantation forests determined using LiDAR.

Widespread afforestation is a crucial component of climate mitigation strategies worldwide. This presents a significant opportunity for biodiversity conservation if forests are appropriately managed. Within forests, structural and habitat diversity are known to be critical for biodiversity but pragmatic management recommendations are lacking. We make a comprehensive assessment of the effects of habitat variables on bird populations using data from over 4000 ha of forested landscape. We combine high-resolution remote sensing data with comprehensive management databases to classify habitat attributes and measure the response of six taxonomic and functional diversity metrics: species richness, Shannon diversity, functional richness, functional evenness, functional divergence, and functional dispersion. We use a novel approach that combines hierarchical partitioning analysis with linear models to determine the relative importance of different habitat variables for each bird diversity metric. The age class of forest stands was consistently the most important variable across all bird diversity metrics, outperforming other structural measures such as horizontal and vertical heterogeneity and canopy density. Shrub density and gap fraction were each significantly associated with one bird diversity metric. In contrast, variables describing within-stand structural heterogeneity (vertical and horizontal) were generally less important while tree species identity (e.g., conifer or broadleaved) was not significant for any bird diversity metric. Each of the six bird diversity metrics had different patterns of independent variable importance and significance, emphasizing the need to consider multiple diversity metrics in biodiversity assessments. Similarly, the optimal resolution for remote sensing metrics varied between structural variables and bird diversity metrics, suggesting that the use of remote sensing data in biodiversity studies could be greatly improved by first exploring different resolutions and data aggregations. Based on the results from this comprehensive study, we recommend that managers focus on creating habitat diversity at the between-, rather than exclusively within-stand scale, such as by creating a matrix of different age classes, to maximize bird diversity. This recommendation for forest managers is powerful yet pragmatic in its simplicity.

Foraging habitat selection of shrubland bird community in tropical dry forest

AbstractHabitat loss due to increasing anthropogenic disturbance is the major driver for bird population declines across the globe. Within the Eastern Ghats of India, shrubland bird communities are threatened by shrinking of suitable habitats due to increased anthropogenic disturbance and climate change. The development of an effective habitat management strategy is hampered by the absence of data for this bird community. To address this knowledge gap, we examined foraging sites for 14 shrubland bird species, including three declining species, in three study areas representing the shrubland type of forest community in the Eastern Ghats. We recorded microhabitat features within an 11 m radius of observed foraging points and compared these data with similar data from random plots. We used chi‐square to test the association between plant species and bird species for sites where they were observed foraging. We observed significant differences between foraging sites of all the study species and random plots, thus indicating selection for foraging habitat. Using linear discriminant analysis, we found that the microhabitat features important for the bird species were shrub density, vegetational height, vertical foliage stratification, grass height, and percent rock cover. Our results show that diet guild and foraging strata influence the foraging microhabitat selection of a species (e.g., ground‐foraging species differed significantly from other species). Except for two species, all focal birds were associated with at least one plant species. The plant‐bird association was based on foraging, structural, or behavioral preferences. Several key factors affecting foraging habitat such as shrub density can be actively managed at the local scale. Strategic and selective harvesting of forest products and a spatially and temporally controlled livestock grazing regime may allow regeneration of scrubland and create conditions favorable to birds.

“Perchoo,” or the Music of Mourning

“Perchoo,” or the Music of Mourning

UJI AKTIVITAS ANTIBAKTERI EKSTRAK ETANOL KULIT BATANG SANTIGI (Pemphis acidula) TERHADAP BAKTERI Escherichia coli DENGAN METODE DIFUSI CAKRAM

Santigi plant (Pemphis acidula) is a plant from the Lythraceae family in the form of a dense shrub or small tree. People in Buru Regency use this plant as a daily treatment, one of which is to treat diarrhea. Santigi plant (Pemphis acidula) contains chemical compounds that function as antibacterial. Antibacteria are substances that inhibit and kill. Escherichia coli is a gram-negative bacterium that causes infection in the intestines and causes diarrhea. This study aims to determine the antibacterial activity of the bark of santigi (Pemphis acidula) against bacteria Escherichia coli. This research is an experimental laboratory research. The study used a thick 95% ethanolic extract of santigi stem bark (Pemphis acidula), variations in extract concentration were 20%, 40%, 60%, 80%, and 100%, for negative control using distilled water and for positive control using cotrimoxazole. In antibacterial testing of the ethanolic extract of the santigi stem bark (Pemphis acidula) against Escherichia coli bacteria, it showed that at concentrations of 20%, 40%, 60%, 80% and 100% sensitive to inhibit bacterial growth with an inhibition zone diameter of 12.3 mm, 14.17 mm, 16.00 mm, 17.00 mm, and 17.67 mm. The negative control did not have antibacterial activity and did not have an inhibition zone diameter, positive control had an inhibition zone diameter of 39.33 mm. The results showed that the bark of santigi has an inhibitory power against the growth of Escherichia coli bacteria with a strong category.

Small effects of livestock grazing intensification on diversity, abundance, and composition in a dryland plant community.

Livestock grazing is a globally important land use and has the potential to significantly influence plant community structure and ecosystem function, yet several critical knowledge gaps remain on the direction and magnitude of grazing impacts. Furthermore, much of our understanding of the long-term effects on plant community composition and structure are based on grazer exclusion experiments, which explicitly avoid characterizing effects along grazing intensity gradients. We sampled big sagebrush plant communities using 68 plots located along grazing intensity gradients to determine how grazing intensity influences multiple aspects of plant community structure over time. This was accomplished by sampling plant communities at different distances from 17 artificial watering sources, using distance from water and cow dung density as proxies for grazing intensity at individual plots. Total vegetation cover and total grass cover were negatively related to grazing intensity, and cover of annual forbs, exotic cover, and exotic richness were positively related to grazing intensity. In contrast, species richness and composition, bunchgrass biomass, shrub density and size, percentage cover of bare ground, litter, and biological soil crusts did not vary along our grazing intensity gradients, in spite of our expectations to the contrary. Our results suggest that the effects of livestock grazing over multiple decades (mean=46 years) in our sites are relatively small, especially for native perennial species, and that the big sagebrush plant communities we sampled are somewhat resistant to livestock grazing. Collectively, our findings are consistent with existing evidence that indicates the stability of the big sagebrush plant functional type composition under current grazing management regimes.

Response of understorey vegetation in chir pine forests to prescribed burning in Shiwalik region of Himalaya

Aim: The present investigation was carried out to understand the impact of controlled/prescribed burning on understorey vegetation in chir pine (Pinus roxburghii) forests of Shiwalik region to manage the summer fire damage. Methodology: Chir pine forest areas of two hectares (ha) each were selected at three sites in Shiwalik region of Himalaya for prescribed burning. Each forest area was delineated into three plots of which one plot was burnt during mid-winter in the year 2017 (B1) and another plot burnt twice (B2) during 2017 and 2018 whereas the third was kept unburnt plot (C) in each site. The phytosociological attributes of understorey vegetation were studied in November, 2018. The difference in density of shrubs (plants 25 m-2) and herbs (plants m-2) in unburnt (C), once burnt (B1) and twice burnt (B2) was analyzed through critical difference (CD). Results: Total density (plants 25m-2) of shrubs ranged from 7.15 to 12.95 in unburnt (C), 3.90 to 8.40 in once burnt (B1) and 2.25 to 4.65 in twice burnt (B2) plots whereas total density (plants m-2) of herbs varied from 25.83 to 44.95 in unburnt (C), 33.20 to 75.92 in once burnt (B1) and 29.31 to 90.93 in twice burnt (B2) plots. The density of shrubs was significantly higher in unburnt plots (C) as compared to burnt plots and vice versa for herbs. The Shanonn Wiener Index (H) ranged from 1.76 to 2.39 for shrubs and 2.32 to 3.15 for herbs. Interpretation: The density of herbs was higher in burnt plots and it was vice versa for shrubs. The prescribed burning enhanced diversity of herbs while shrubs diversity decreased with burning.

A Parametric Study of Fire Risks of Green Roofs to Adjacent Buildings

The susceptibility of plants to burn raises concerns about fire hazard that green roofs may pose to buildings. Main concerns relate to cases when such roofs are poorly maintained or stressed by drought conditions which leads to drying out of plants and the accumulation of dead organic material, greatly increasing the availability of fuel load. Existing standard safety measures aim to prevent the spread of fire through the vegetation cover. However, fire spread by thermal radiation is not considered. In this study, fire risk of exposure of adjacent buildings to radiant heat flux produced by fire on green roofs was assessed. Based on generally accepted maximum tolerable radiant heat flux to exposed facades of 12.5 kW/m2, the minimum safe separation distances were obtained for different conditions. Wildland fire behavior model was used to determine flame lengths which is the necessary parameter for a radiation model. Several vegetation types, moisture content scenarios and wind speeds were taken as variables. It was found that by providing the vegetation with reasonably high moisture content the fire risk can be greatly reduced, especially for grass-covered roofs. Since wind also has a strong effect on flame size, considering the exposure of a green roof to wind can bring better understanding of fire risk to adjacent buildings. At no-wind condition and at extremely low moisture content separation distances are as short as 3.1 m for dense shrubs and 2.4 m for tall dense grass.

Woody Species Composition, Structure, and Carbon Stock of Coffee-Based Agroforestry System along an Elevation Gradient in the Moist Mid-Highlands of Southern Ethiopia

There is a limited effort in Ethiopia to study scientifically the ecological features of traditional coffee-based agroforestry systems. This study was initiated to determine the structure, composition, and carbon stock of woody species along an elevation gradient of a traditional coffee-based agroforestry system in Yirgacheffe district, southern Ethiopia. Woody plants’ inventory was conducted in thirty-eight sampling quadrats (20 ∗ 20 m) along five elevation contours and eight transects. Thirty-eight soil samples were taken from randomly selected subplots at 0–30 cm soil depths. In this study 32, woody plant species representing 23 families were recorded. Species richness ranged from 13–17 along the elevation gradient. Woody plant diversity indices appear to have a slight variation with increasing elevation gradient. Shade tree and coffee shrub density, DBH, and height showed significant variations along the elevation gradient. Total aboveground woody biomass carbon stock along elevation gradient ranged from 11.07 to 27.48 Mg·ha−1. Soil organic carbon stock was slightly different across elevation gradients with a mean range of 83.91 to 89.29 Mg·ha−1. These indicate that the agroforestry system has significant potential of storing and enhancing ecosystem carbon stocks across all the elevation gradients. The findings generally show that agroforestry systems in the study area are diverse, structurally complex with significant carbon storage in the soil and woody biomass.

Advances in the carbon sink potential of terrestrial ecosystems in China

<p indent="0mm">The “carbon peak and carbon neutrality” concept has become a major demand for global climate governance and ecological civilization construction in China. Understanding the potential of terrestrial carbon sequestration and its response to climate change and human activities is very important for accurately predicting the impacts of future climate change on terrestrial ecosystems and is the basic premise for human beings to cope with climate change. Based on the perspective of terrestrial ecosystem carbon storage and carbon sinks, this paper summarizes the carbon storage of forest, shrub, grassland, farmland and wetland ecosystems of China, thus assessing the carbon sink potential of the Chinese terrestrial ecosystem and its response to different climate change scenarios and human activities. The evaluation results varied greatly due to different research methods and data. The average biomass carbon density of China’s forests and grasslands was approximately 55.7 and 4.8 Mg C ha⁻¹, respectively, which were lower than the average values of the global forests (94.2 Mg C ha⁻¹) and grasslands (7.2 Mg C ha⁻¹), mainly due to larger areas of young forests and extensive grazing. The average biomass carbon density of the wetland was approximately 4.1 Mg C ha⁻¹, which varied greatly for different types of wetland vegetation, and the highest value was located in coastal wetland vegetation (9.6 Mg C ha⁻¹). The biomass carbon density of shrub and farmland was approximately 4.8–9.6 and 3.06–7.1 Mg C ha⁻¹, respectively. The carbon sink potential of China’s main terrestrial ecosystems (forest, shrub, grassland and farmland) estimated by different methods varied greatly. According to the eighth (2009–2013) and ninth (2014–2018) inventory data of China’s forest resources and other inventory data, the latest result of the carbon storage increase rate of China’s terrestrial ecosystem was estimated to be approximately <sc>0.28 PG C a⁻¹.</sc> Ecological engineers should greatly promote the carbon sink potential of terrestrial ecosystems. The terrestrial ecosystem carbon sink of six major national ecological engineering projects in China reached approximately 132 Tg C a⁻¹, of which more than half (74 Tg C a⁻¹, 56%) was attributed to the implementation of ecological engineering projects. The carbon sink increase was approximately 14.7 and 14 Tg C a⁻¹ from the conversion of farmland to grassland engineering area and natural forest protection engineering area, respectively, and approximately 7.0−12 Tg C a⁻¹ in each of the other five engineering areas. Thus, it is necessary to constantly improve the assessment methods of terrestrial ecosystem carbon reserves and carbon sinks and constantly update the assessment results based on the latest data. The shortcomings of the existing studies are put forward in this paper. (1) Integrated research on the carbon sink function of China’s terrestrial ecosystems in different periods and different emission scenarios in the future is insufficient, especially on the sink potential of different kinds of major ecological projects in the same region. (2) Impact research on nitrogen deposition and its interaction with climate change and atmospheric CO₂ concentration on the carbon sink potential of China’s terrestrial ecosystems is still insufficient, especially regarding the carbon sink potential of major national ecological projects. (3) Research on the climate change risk of carbon sequestration in China’s terrestrial ecosystems has not been conducted. Finally, this research identifies research activities on carbon storage and carbon sinks in China’s terrestrial ecosystems in the future, including carbon sink potential and a risk assessment of major national ecological projects, the simulation technology of the regional terrestrial ecosystem carbon budget with high spatial heterogeneity, and the dynamic downscaling method and correction technology of meteorological data under different climate change scenarios, to provide scientific support for the systematic management optimization scheme of increasing sinks in China’s terrestrial ecosystem and to serve the strategy of national carbon neutrality.

Response strategies of woody seedlings to shading and watering over time after topsoil translocation in dry-hot karst region of China

Translocating topsoil from an appropriate donor forest is a promising strategy to restore seriously degraded sites. However, some dominant or constructive species did not survive due to plant stress in the seedling stage, which ultimately led to a poor community structure and low similarity between new communities and donor forest. In this study, we replaced the topsoil of karst rocky desertification with forest topsoil and imposed different shading and watering treatments following quadratic saturation D-optimum design. Richness, abundance, height and base diameter of woody species (trees + shrubs) were measured yearly to construct mathematical equation between them and shade degrees (SD) and water quantity (WQ) by using multiple stepwise regression. Results displayed a positive linear relationship between richness of woody species and SD at the second year of topsoil translocation, which changed to a parabolic relationship at the fifth year with a maximum 30.8 species when SD was 37.5 %. The positive linear relationship between density of woody species, shrubs and trees and SD at the second year transformed into a parabolic relationship at the fifth year, and density reached maximum 6.3, 3.7 and 3.8 seedlings/m2 when SD were 41.7, 38.9 and 45.0%, respectively. In contrast, the density of Paliurus orientalis and Sophora viciifolia turned into a negative linear relationship with SD at the fifth year. Moreover, although the effect of SD and WQ on height of woody species increased over time, shading inhibited base diameter of shrubs and height of Quercus cocciferoides, Sapium sebiferum and Fraxinus malacophylla at the fifth year. We concluded that no-shading and heavy shading reduced species diversity, and light to moderate shading should be recommended in first 2–3 years after topsoil translocation to enhance woody species survival and accelerate similar forest community establishment providing guidance for the management, regeneration and restoration of native forest in semi-arid areas.

Carbon Sink under Different Carbon Density Levels of Forest and Shrub, a Case in Dongting Lake Basin, China

Terrestrial ecosystems play a critical role in the global carbon cycle and climate change mitigation. Studying the temporal and spatial dynamics of carbon sink and the driving mechanisms at the regional scale provides an important basis for ecological restoration and ecosystem management. Taking the Dongting Lake Basin as an example, we assessed the carbon sinks of forest and shrub from 2000 to 2020 based on the maps of biomass that were obtained by remote sensing, and analyzed the dynamics of carbon sinks that were contributed by different biomass carbon density levels of constant forest and shrub and new afforestation over the past two decades. The results showed that the carbon sink of forest and shrub in the Dongting Lake Basin grew rapidly from 2000 to 2020: carbon sink increased from 64.64 TgC between 2000 and 2010, to 382.56 TgC between 2010 and 2020. The continuous improvement of biomass carbon density has made a major contribution to carbon sink, especially the carbon density increase in low carbon density forests and shrubs. Carbon-dense forests and shrubs realized their contribution to carbon sink in the second decade after displaying negative carbon sink in the first decade. Carbon sink from new afforestation increased 61.16% from the first decade to the second decade, but the contribution proportion decreased. The overall low carbon density of forest and shrub in the Dongting Lake Basin and their carbon sink dynamics indicated their huge carbon sequestration potential in the future. In addition to continuously implementing forest protection and restoration projects to promote afforestation, the improvement of ecosystem quality should be paid more attention in ecosystem management for areas like Dongting Lake Basin, where ecosystems, though severely degraded, are important and fragile, to realize their huge carbon sequestration potential.

Logging legacies in a plant biodiversity hotspot: Altered distribution and abundance patterns of the shrub layer in the southern Appalachians

Altered disturbance regimes in forest ecosystems can lead to the formation of dense, persistent understory vegetation composed of a small number of dominant species. This understory layer often limits tree seedling recruitment, decreases biodiversity, and can alter forest ecosystem structure and functioning. In the southern Appalachians – one of the most biodiverse regions in North America – pervasive logging in the 19th and early 20th centuries may have contributed to the formation of a dense understory shrub layer that suppresses plant diversity and tree recruitment, but the evidence for this idea has been mixed. To help clarify this issue, we tested whether (a) the two dominant understory shrub taxa (Kalmia latifolia and evergreen Rhododendron species) were more common or more abundant in areas with a history of intense logging than in areas undisturbed by logging, and (b) the relationships between the understory shrub layer and environmental gradients that drive regional biodiversity and plant distributions in the Southern Appalachians (e.g., climate, soils) differ in logged versus undisturbed areas. We used publicly available, extensive, and spatially explicit data on vegetation, climate, topography, soils, solar radiation, and logging history in Great Smoky Mountains National Park to build beta and binomial regression models of shrub frequency and cover as a function of logging history and environmental variables. Contrary to our expectation and speculations in the literature, we found that the dominant shrub taxa were more common (frequent) in areas with no logging history. However, we also found that logging history effects on shrub abundance (cover) varied along environmental gradients. For example, in topographically shaded landscape positions evergreen Rhododendron thickets exhibited greater cover in logged areas than in areas with no logging history. On the other hand, Rhododendron thickets exhibited lower cover in logged areas than in areas with no logging history at low elevations. Thus, conservation planning and forest management in topographically complex regions need to consider both landscape context (e.g., elevation, landscape position) and past logging as important interacting drivers that either facilitate or suppress local formation of dense shrub understories that can ultimately impact tree regeneration patterns, biodiversity, and ecosystem functioning.