Landscape-scale Environmental Variables Research Articles

Landscape-scale environmental variables are associated with burrowing crayfish distribution patterns in an Alabama watershed

Landscape-scale environmental variables are associated with burrowing crayfish distribution patterns in an Alabama watershed

Large-scale factors controlling biological communities in the Iberian Peninsula: an insight into global change effects on river ecosystems

The ongoing global environmental change poses a serious threat to rivers. Comprehensive knowledge of how stressors affect biota is critical for supporting effective management and conservation strategies. We evaluated the major gradients influencing spatial variability of freshwater biodiversity in continental Spain using landscape-scale variables representing climate, land use and land cover (LULC), flow regime, geology, topography, and diatom (n = 117), macroinvertebrate (n = 441), and fish (n = 264) communities surveyed in minimally impacted streams. Redundancy analysis identified the environmental factors significantly contributing to community variability, and specific multivariate analyses (RLQ method) were used to assess trait–environment associations. Environmental variables defined the major community change gradients (e.g., mountain–lowland). Siliceous, steep streams with increased precipitation levels favored stalked diatoms, macroinvertebrates with aquatic passive dissemination, and migrating fish. These traits were replaced by adnate diatoms, small macroinvertebrates, and non-migratory fish in lowland streams with warmer climates, calcareous geology, agriculture, and stable flow regimes. Overall, landscape-scale environmental variables better explained fish than diatom and macroinvertebrate community variability, suggesting that these latter communities might be more related to local-scale characteristics (e.g., microhabitat structure, substrate, and water physicochemistry). The upslope environmental gradient of river networks (e.g., slope, temperature, and LULC changes) was paralleled to the observed taxonomy-based and trait-based spatial variability. This result indicates that global change effects on riverine biodiversity could emerge as longitudinal distribution changes within river networks. Implementing management actions focusing simultaneously on water temperature, hydrological regime conservation (e.g., addressing LULC changes), and river continuity might be the best strategy for mitigating global change effects on river biodiversity.

Positive effects of projected climate change on post-disturbance forest regrowth rates in northeastern North American boreal forests

Forest anthropogenic and natural stand-replacing disturbances are increasing worldwide due to global change. Many uncertainties regarding the regeneration and growth of these young forests remain within the context of changing climate. In this study, we investigate the effects of climate, tree species composition, and other landscape-scale environmental variables upon boreal forest regrowth following clearcut logging in eastern Canada. Our main objective was to predict the effects of future climate changes upon post-logging forest height regrowth at a subcontinental scale using high spatial resolution remote sensing data. We modeled forest canopy height (estimated from airborne laser scanning [LiDAR] data over 20 m resolution virtual plots) as a function of time elapsed since the last clearcut along with climate (i.e. temperature and moisture), tree species composition, and other environmental variables (e.g. topography and soil hydrology). Once trained and validated with ∼240 000 plots, the model that was developed in this study was used to predict potential post-logging canopy height regrowth at 20 m resolution across a 240 000 km2 area following scenarios depicting a range of projected changes in temperature and moisture across the region for 2041–2070. Our results predict an overall beneficial, but limited effect of projected climate changes upon forest regrowth rates in our study area. Stimulatory effects of projected climate change were more pronounced for conifer forests, with growth rates increasing between +5% and +50% over the study area, while mixed and broadleaved forests recorded changes that mostly ranged from −5% to +35%. Predicted increased regrowth rates were mainly associated with increased temperature, while changes in climate moisture had a minor effect. We conclude that such growth gains could partially compensate for the inevitable increase in natural disturbances but should not allow any increase in harvested volumes.

Variation in Diversity Pattern of Plants along Environmental Variables at Qazi Nag Range, Kashmir Region, Western Himalaya

Species composition and abundance patterns in eighteen forest sites from 1700m to 3400m elevation were studied to evaluate species diversity and richness at Qazi Nag Range, Kashmir region, Western Himalaya. Evaluation of species diversity was determined by Shannon-Weiner's index of diversity (H') Sheldon evenness index (E) and Margalef species richness index (R'). Species diversity values ranged from 3.497 to 2.773 at 1700m and 3400m respectively whereas species richness varied from 1.83 (1700m) to 0.8 at 3200m. The species diversity and richness values were recorded higher from 2300 to 2600 m having best combination of heat and precipitation which ensure survival of more species. Diversity values declined towards upper and lower reaches, which might be due to flow of individuals from both upslope and low-lying areas. Correlation analyses showed that the environmental variables as altitude and potassium were found negatively correlated with diversity index while pH, EC Organic matter and soil saturation were recorded positively correlated with species diversity. This study highlights the importance of local and landscape scale environmental variables on species diversity and vegetation patterns in Kashmir Region, Western Himalaya

Fragment connectivity shapes bird communities through functional trait filtering in two types of grasslands

Habitat fragmentation is considered one of the most severe threatening factors for global biodiversity. Here we assessed, how local and landscape scale environmental variables, such as fragment size (small vs. large) and landscape configuration (measured as connectivity index) relates to bird community composition, species richness, abundance and functional diversity. We surveyed 60 grassland fragments in Hungary, belonging to two different threatened grassland types, namely forest-steppes and kurgans. Forest-steppes are natural mosaics of grasslands and forests at the contact zone between closed-canopy temperate forests and steppe grasslands. Kurgans are ancient burial mounds, found on the Eurasian steppe and forest steppe zone. These fragments were embedded in plantation forestry, respectively, agricultural matrix with gradients of size and connectivity. Both habitats are threatened by forestry and agricultural intensification, though these fragments may serve as important wildlife refuges. Our findings revealed that forest-steppe birds were more diverse and abundant in large and well-connected than in small isolated fragments. High connectivity affected ground nesting birds in small forest-steppe fragments positively. Birds inhabiting kurgan area showed higher trait similarity in well-connected than in isolated fragments. Bird abundance of kurgans associated with small home range size and ground feeding habit were higher in connected compared to isolated fragments. Highly isolated kurgans filtered for more specialised bird species but not for generalists. We provide conservation implications for enhancing grassland specialist bird communities, which consist of preservation of large, well-connected grassland fragments within production landscapes and through reconsideration of the currently used intensive forestry.

Multilevel decomposition of spatial and environmental effects on nearshore fish assemblages in tropical semi-enclosed ecosystems

We investigated the effects of local- and landscape-scale environmental variables and spatial structure at three hierarchical levels (i.e. type of system, individual systems, and zones within each system) on the fish species composition and abundance in bays and coastal lagoons in southeastern Brazil. The effects were assessed at the assemblage level, and between and within habitat use groups. Exclusive and shared effects of environmental, hierarchical, and spatial variable sets were quantified by variation partitioning, and individual environmental effects were assessed by partial canonical correspondence analyses. The hierarchical and spatial structures were more relevant for habitat use groups less widespread due to the lower dependence on estuarine areas, and influenced primarily the landscape-scale environmental differences between individual systems. At the assemblage level, the exclusively environmental effects were primarily indicative of the marine (e.g., higher depth, pH, and transparency) versus continental (e.g., greater distance from the ocean and mangrove cover) influence. Estuarine, marine migrant, and marine straggler species were more widespread across these gradients, but the former species were primarily associated with greater mangrove cover and the marine stragglers with a higher marine influence. Semi-diadromous and freshwater species were less associated with greater mangrove cover and primarily restricted to coastal lagoons. The different multi-scale environmental effects within each group reinforced the relevance of intra- and inter-specific differences in environmental tolerances and requirements, and evidenced the relevance of the connectivity between alternative habitats in maintaining the structure of fish assemblages. Disentangling multilevel spatial and environmental effects, this study evidenced the critical roles of the maintenance of the environmental heterogeneity in nearby estuarine habitats for nearshore fish assemblages in different types of tropical semi-enclosed estuarine ecosystems.

Bird Communities in Urban Riparian Areas: Response to the Local- and Landscape-Scale Environmental Variables

Understanding how environmental changes driven by urbanization impact the biodiversity in urban riparian areas has great importance for landscape planning and river ecosystem conservation. There have been many studies on the response of bird communities to different environmental variables in urban parks; however, although supporting some of the highest bird diversities, case studies in urban riparian areas remain limited. In existing research, few studies have considered the impact of both local waterfront characteristics and surrounding environmental variables at a larger scale. In this study, we selected birds as the indicator to clarify their response to both local- and landscape-scale environmental variables in riparian areas of Tsing river, Beijing, in terms of (a) vegetation composition, (b) human disturbance, (c) land cover, and (d) landscape connectivity. We hypothesized that birds with different biological characteristics may respond differently to environmental variables. Birds were then further grouped according to the habitat type, residential type, and feeding type. It turned out that the coverage of grass and the disturbance of pedestrians are the most influential variables. Besides, compared with the land cover and landscape connectivity, the total contribution of vegetation characteristics and human disturbance accounts for the main proportion of explained variance. Information pertaining to these environmental variables can provide evidence to support bird conservation efforts in urban areas, and the identified distance threshold provides a basis for future landscape connectivity assessments.

Using maximum entropy modeling to predict suitable habitat locations for the Cutshin Crayfish (Cambarus taylori)

The Cutshin Crayfish (Cambarus taylori) is a recently described species which is endemic to the Middle Fork of the Kentucky River basin. The Middle Fork of the Kentucky River lies within the anthracite coal fields of Eastern Kentucky, and thus a conservation assessment of C. taylori is warranted. The goal of this study was to predict suitable habitat locations for C. taylori through use of maximum entropy modeling (MaxEnt). The Middle Fork of the Kentucky River’s crayfish fauna was surveyed during the summer of 2014. The occurrence data from this study coupled with landscape scale environmental variables—such as stream order and land use data—was used to create the model. The mean area under the receiver operating characteristic curve (AUC) value was 0.898, showing the model had high predictive accuracy. The model indicated high probability of occurrence in streams at the southern end of the basin, and a low probability of occurrence at the northern end of the basin. Stream order and stream sinuosity had the highest contribution to the model showing that C. taylori prefers 3rd and 4th order streams with low sinuosity. Although the AUC value showed high predictive accuracy for the model, predicted sites will need to be ground validated to confirm the model’s predictive accuracy.

Landscape features associated with the roosting habitat of Indiana bats and northern long-eared bats

Context Bat conservation in the eastern United States faces threats from white nose syndrome, wind energy, and fragmentation of habitat. To mitigate population declines, the habitat requirements of species of concern must be established. Assessments that predict habitat quality based upon landscape features can aid species management over large areas. Roosts are critical habitat for many bat species including the endangered Indiana bat (Myotis sodalis) and the threatened northern long-eared bat (M. septentrionalis). Objectives While much is known about the microhabitat requirements of roosts, translating such knowledgeintolandscape-level management isdifficult.Our goal was to determine the landscape-scale environmental variables necessary to predict roost occupancy for both species. Methods Using MaxLike,a presence-onlyoccupancy modeling approach, with known roost sites, we identified factors associated with roosting habitat. Spatially independent roost locations were particularly limited for northern long-eared bats resulting in differences in study areas and sample sizes between the two species. Results Occupancy of Indiana bat roosts was greatest in areas with[80 % local forest cover within broader landscapes (1 km) with \40 % forest, \ 1k m of perennial streams but[ 1 km from intermittent streams and in areas with poor foraging habitat. Northern longearedroostoccupancywasgreatestinareaswith[80 % regional but fragmented forest cover with greater forest edge approximately 4 km from the nearest major road. Conclusions Landscape features associated with roost occupancy differed greatly between species suggesting disparate roosting needs at the landscape scale, which may require independent management of roost habitat for each species.

Climatic, edaphic and fire regime determinants of biome boundaries in the eastern Cape Floristic Region

Landscapes of the eastern Cape Floristic Region are extremely rich in biomes. Analysis of the determinants of boundaries between biomes can generate insights and predictions that are useful for the applied ecological sciences. Here we used a historical data set and multivariate methods to explore the determinants of the boundaries of Forest, Fynbos, Grassland, Renosterveld and Thicket biomes in a 1200km2 area of the Kouga region. The data set comprised 203 (10m×10m) sites with corresponding landscape-scale environmental variables, and 100 sites with corresponding site-bound edaphic (physical and chemical) variables. Of the landscape variables, soil drainage and fire exposure had the strongest biome-specific associations: most Grassland occurred on seasonally waterlogged soils and Renosterveld on moderately drained soils. While Forest was exclusively associated with landscapes protected from fire, much Fynbos and Thicket were found in areas exposed to fires of intermediate frequency; however, in these situations Fynbos is restricted to sandstone-derived soils and thicket to shale-derived soils. Other strong patterns were the restriction of Forest to sandstone-derived soils and of Thicket to soils of deep to intermediate depth. Soils of the majority of Fynbos and Grassland were shallow, rocky and infertile, while those of Forest and Thicket were deep, rock-free and fertile, especially in terms of oxidizable carbon and total nitrogen. The relatively high fertility of Forest and Thicket soils is attributed canopy-induced enrichment in the prolonged absence of fire. Renosterveld occupied soils of intermediate fertility. These patterns can provide useful insights for developing experimental approached to simultaneously assess the determinants of multiple boundaries in the biome-rich landscape of the eastern Cape Floristic Region.

A freshwater ecoregion delineation approach based on freshwater macroinvertebrate community features and spatial environmental data in Taizi River Basin, northeastern China

The ecoregion is currently widely used as the basic geospatial unit in freshwater biodiversity conservation. The popularly used delineation is usually based on the assumption that attributes of aquatic ecosystems are influenced by landscape-scale environmental variables. However, few ecoregion delineations attempt to establish the local validity of this assumption prior to delineation, and few studies check the correspondence of the derived ecoregion boundaries with the distributions of attributes of aquatic biota. In this study, we established an approach to overcome these shortcomings. The notable features of the approach are: (1) the delineation variables were filtered through a series of analytical steps to select those that best represented the aquatic community traits, and which avoided redundancy in the data; (2) the method was quantitative and repeatable; and (3) the derived ecoregion boundaries were checked for consistency with the spatial attributes of aquatic biota. The approach was applied in the Taizi River Basin, northeast China. The procedure proposed here filtered out altitude and annual precipitation as the best variables to include in the freshwater ecoregion delineation. Then, using the quantitative ISODATA classification method, the basin was classified into three ecoregions. A test of accuracy indicated that freshwater ecoregions matched well with the spatial distribution pattern of macroinvertebrate community attributes. Statistical analysis showed that natural geographical attributes and river attributes were different in the three ecoregions, and indices representing macroinvertebrate community attributes are significantly different as a whole among the three ecoregions. The case study proved this approach effective on ecoregion delineation.

Population responses of the Endangered White-breasted ThrasherRamphocinclus brachyurusto a tourist development in Saint Lucia – conservation implications from a spatial modelling approach

SummaryTourism development is one of the main contemporary drivers of habitat loss and fragmentation within the Caribbean Islands biodiversity hotspot. In Saint Lucia, construction of a hotel and golf course within coastal dry forest is directly threatening the largest known subpopulation of the Endangered White-breasted ThrasherRamphocinclus brachyurus. Understanding how the species is responding to ongoing landscape change and identifying priority sites for conservation are imperative for planning its long-term conservation. In this study, a four year White-breasted Thrasher monitoring dataset (2006–2009) and landscape-scale environmental variables were used to: a) identify, characterise and map spatio-temporal patterns of White-breasted Thrasher encounter rate (an abundance proxy) within and outside the tourist development site; b) determine landscape-scale environmental variables that influence such patterns, and c) produce an island-wide predictive map of potentially suitable habitat. Observed patterns in encounter rates within and outside the development site were consistent with thrashers being displaced from cleared areas of forest and crowding into intact forest patches to the north and west of the golf course. A year after the period of the most extensive habitat clearance, White-breasted Thrasher numbers declined markedly leading to a 55% reduction in encounter rate within the development site over the four years of the study. The habitat suitability model predicted that a range of sites outside of the known geographic range of the thrasher are potentially suitable, some of which merit further surveys for potentially undetected populations. Given these findings, it is vital that patches of suitable dry forest adjacent to the tourist development are protected and contiguous natural habitat inside the tourist development is preserved.

Associations of Bird Species Richness and Community Composition with Local and Landscape-scale Environmental Factors in Borneo

A comprehensive understanding of variables associated with spatial differences in community composition is essential to explain and predict biodiversity over landscape scales. In this study, spatial patterns of bird diversity in Central Kalimantan, Indonesia, were examined and associated with local-scale (habitat structure and heterogeneity) and landscape-scale (logging, slope position and elevation) environmental variables. Within the study area (c. 196 km2) local habitat structure and heterogeneity varied considerably, largely due to logging. In total 9747 individuals of 177 bird species were recorded. Akaike's information criterion (AIC) revealed that the best explanatory models of bird community similarity and species richness included both local- and landscape-scale environmental variables. Important local-scale variables included liana abundance, fern cover, sapling density, tree density, dead wood abundance and tree architecture, while important landscape-scale variables were elevation, logging and slope position. Geographic distance between sampling sites was not significantly associated with spatial variation in either species richness or similarity. These results indicate that deterministic environmental processes, as opposed to dispersal-driven stochastic processes, primarily structure bird assemblages within the spatial scale of this study and confirm that highly variable local habitat measures can be effective means of predicting landscape-scale community patterns.