Relative Contribution Of Environmental Variables Research Articles

White-rumped Vulture’s Habitat Suitability Prediction using MaxEnt in Arunachal Pradesh

Few reports showed that White-rumped vulture is present in Arunachal Pradesh. However, they were reported from a few places only. Such sightings suggest that either the region is not explored completely or the habitats are not suitable for the species. Therefore, knowing and predicting the habitat suitability of WRV and revealing the relative contribution of environmental variables determining such distribution can be important for their protection and conservation. The present study was based on the current distribution of WRV in Arunachal Pradesh that we had surveyed from 2016 to 2020. We followed the road count and point count methods to obtain primary occurrence data. Also, secondary data on occurrence records and data on environmental variables (landscape variables, anthropogenic variables, and climatic variables) were obtained and used. The data were processed using ArcMap. 29 occurrence records (filtered) and 11 environmental variables were used to build the prediction model using maximum entropy (MaxEnt). The MaxEnt predicted model showed high accuracy with area under the receiver operating characteristic curve value equals to 0.95 and True Skill Statistics value equals to 0.87. Of the total area, only 2629.63 km2 (3.20 %) is suitable for WRV while the majority of the area is unsuitable (79542.84 km2) (96.79 %). The elevation (32.2%), land use land cover (31.7%), and normalized difference vegetation index of November (26.7%) were the most influencing variables impacting the distribution of WRV. Among bioclimatic variables, the mean temperature of the warmest quarter and precipitation of the wettest quarter had the highest contribution. This work is the first attempt to understand the spatial distribution of WRV and the environmental factors associated with their distribution in the state. The findings can be relevant for designing conservation efforts to conserve this species in the state.

Climatic Variables Differentially Influence Neotropical Plant Species of Conservation Concern

ABSTRACT Knowing how and to what extent environmental parameters affect threatened species facilitates the understanding of their specific microhabitat requirements. In this study, we examined the response patterns of four threatened tropical plant species to variations in temperature, precipitation, and physiographic variables, and analyzed the relative contributions of environmental variables to the observed distributions of the species. The studied species are Bursera coyucensis, Cryosophila argentea, Guatteria anomala, and Vatairea lundellii and are cataloged into specific risk categories in the Mexican Official Standard NOM-059-SEMARNAT. Our findings suggest differences in ranges of temperature and precipitation (for example, C. argentea exhibited narrower ranges compared to G. anomala and V. lundellii in precipitation) and similarity in ranges of slope across species distributions. We also found that most species distributions respond non-linearly to variations in environmental variables. These results contribute to defining the environmental spaces of these species. The partial and combined effects of climatic variables, and the range of environmental distributions reported here, have intrinsic implications for the adaptation capacity, plasticity, and survival of these species to environmental variation. This information could be useful to promote conservation activities such as the creation of microhabitats with optimal environmental preferences through sustainable silviculture.

Influence of niche and neutral processes on fish communities associated with changes in macrophyte rafts along the hydrological cycle

Aquatic macrophytes add structural complexity to the environment, which influences fish species. The structure of macrophytes rafts can vary depending on the hydrological cycle and space availability. Thus, the objective of the present study was to evaluate which predictors associated with environmental conditions, composition of macrophyte species and spatial factors can affect fish communities in different hydrological regimes. The study was carried out in oxbow lakes in the Amazon, in the middle Purus River, Amazonas, Brazil. Samples of fish and macrophytes were collected during the flood, receding and drought periods, and environmental variables were measured in all macrophytes rafts. Partial redundancy analysis was applied to quantify the relative contribution of environmental variables, macrophyte composition and spatial factors in the fish community. Our study revealed that environmental conditions and macrophyte species composition, and both spatially structured as well, were the main factors that explained changes in fish composition in floating meadows of oxbow lakes. Corroborating our predictions, the variations in the fish communities were explained mainly by niche-based processes, including environmental conditions and macrophyte species composition as an environmental component, which varied over the hydrological cycle. The spatial component was more important during flooding, environmental conditions during receding, and macrophyte species composition during the drought hydrological regime. However, the shared explanations that indicated a spatially structured environment, both for environmental conditions and for composition of macrophytes, were greater during all hydrological regimes, also supporting our prediction.

Multimodel inference to quantify the relative importance of abiotic factors in the population dynamics of marine zooplankton

Abstract The effect of multiple stressors on marine ecosystems remains poorly understood and most of the knowledge available is related to phytoplankton. To partly address this knowledge gap, we tested if combining multimodel inference with generalized additive modelling could quantify the relative contribution of environmental variables on the population dynamics of a zooplankton species in the Belgian part of the North Sea. Hence, we have quantified the relative contribution of oceanographic variables (e.g. water temperature, salinity, nutrient concentrations, and chlorophyll a concentrations) and anthropogenic chemicals (i.e. polychlorinated biphenyls) to the density of Acartia clausi. We found that models with water temperature and chlorophyll a concentration explained ca. 73% of the population density of the marine copepod. Multimodel inference in combination with regression-based models are a generic way to disentangle and quantify multiple stressor-induced changes in marine ecosystems. Future–oriented simulations of copepod densities suggested increased copepod densities under predicted environmental changes.

Consistent, congruent or redundant? Lotic community and organisational response to disturbance

Although different organisms and metrics are used in aquatic ecosystem assessment, deciding which organism group(s) or community level to apply tends to be based on the local level of taxonomic expertise, rather than the discriminatory power or precision of a given response to specific stressors. We compare the response of two different organism groups (fish and invertebrates) and ecological traits (fish guilds and invertebrate traits) to putative stress gradients, using northern Portuguese rivers as a case study. The rivers covered a quality gradient ranging from reference conditions to high levels of disturbance across classes of ecological status within designated Water Framework Directive monitoring networks. We tested three hypotheses: 1) Ecological traits respond better to regional level human impacts (e.g. land use), while taxa better respond to local factors (e.g. habitat changes or water quality); 2) Invertebrate traits or fish guilds respond to a wider range of anthropogenic disturbances compared to taxa and are not as strongly affected by temporal variation; 3) these two communities respond differently along the studied gradients.We used canonical correspondence analyses, including partial correspondence analysis and principal response curves to analyze change in composition and metrics and the relative contribution of environmental variables for each biological data set. We carried out analyses between sites and along a temporal gradient, complemented by linkage trees and logistic regressions. Conclusions are more complex than the formulated hypotheses. Although both invertebrate and fish communities revealed a similar ability to assess impairment, invertebrates responded more strongly to local disturbances, whereas the fish composition or traits/guilds were more sensitive to larger scale variation. Results for temporal variation analyses suggested that invertebrate traits more accurately detected change in environmental factors but variation in the taxonomic composition of fish species also followed a temporal gradient. Differences on community response reinforce the importance of a combined approach, using types of community data, to detect environmental impacts.

Disentangling the local-scale drivers of taxonomic, phylogenetic and functional diversity in woody plant assemblages along elevational gradients in South Korea.

Recently, new alternative matrices of biodiversity such as phylogenetic and functional diversity as a complement to species diversity have provided new insights into the mechanisms of community assembly. In this study, we analyzed the phylogenetic signals of five functional traits and the relative contribution of environmental variables and distance matrices to the alpha and beta components of taxonomic, phylogenetic and functional diversity in woody plant assemblages along four local elevational transects on two different mountains. We observed low but significant phylogenetic signals of functional traits, which suggest that phylogenetic dispersion can provide a rough approximation of functional dispersion but not perfect correlations between phylogenetic and functional diversity. Taxonomic alpha diversity showed a monotonic decline with elevation, and climatic variables were the main drivers of this pattern along all studied transects. Furthermore, although the phylogenetic and functional alpha dispersions showed different elevational patterns including increase, decrease and no relationship, the underlying processes driving the patterns of both types of alpha dispersion could be explained by the gradients of climatic and habitat variables as well as biotic interactions such as competition. These results suggest that both alpha dispersion patterns may be significantly controlled by niche-based deterministic processes such as biotic interactions and environmental filtering in our study areas. Moreover, the beta diversity with geographical distances showed distance-decay relationships for all transects. Although the relative importance of the environmental and geographical distances for beta diversity varied across the three facets of diversity and the transects, we generally found that environmental distances were more important for the beta components of the three facets of diversity. However, we cannot discriminate the effects of both distances on the three facets of diversity. Therefore, our study suggests that niche-based deterministic processes, potentially combined with neutral processes such as dispersal limitation and demographic stochasticity, may influence patterns of woody plant assemblage turnover in our study areas.

Relative contribution of multiple stressors on copepod density and diversity dynamics in the Belgian part of the North Sea

The effect of multiple stressors on marine ecosystems is poorly understood. To partially bridge this knowledge gap we investigated the relative contribution of environmental variables to density and diversity dynamics of the zooplankton community in the Belgian part of the North Sea. We applied multimodel inference on generalized additive models to quantify the relative contribution of chlorophyll a, temperature, nutrients, salinity and anthropogenic chemicals (i.e. polychlorinated biphenyls and polycyclic aromatic hydrocarbons) to the dynamics of calanoid copepod species in the Belgian part of the North Sea. Temperature was the only predictor consistently showing a high importance in all models predicting the abundances of the selected copepod species. The relative contribution of other predictors was species-dependent. Anthropogenic chemicals were important predictors for three out of six species indicating that chemical mixtures at low concentrations should not be left unattended when performing risk assessments in a natural environment.

Spatial variability of potassium in agricultural soils of the canton of Fribourg, Switzerland

Potassium (K) is a crucial element for plant nutrition and its availability and spatial distribution in agricultural soils is influenced by many agro-environmental factors. In Switzerland, a soil monitoring network (FRIBO) was established in 1987 with 250 sites distributed over the whole of the canton of Fribourg (representing 4% of the surface area of Switzerland), whose territory is shared between the Swiss Midlands and the Western Alp foothills. In this study area, diverse geological deposits (sandstone, marlstone, silts and calcareous rocks), soil types (Cambisols, Gleysols, Rendzinas, Luvisols and Fluvisols) and land uses (cropland, permanent grassland and mountain pasture) are present, making the network interesting for assessing the relative contribution of environmental variables and land use management on soil properties. The aims of the present study were to (i) characterize the soil K status in the Fribourg canton according to four different extraction methods; (ii) analyse the spatial variability of soil K in relation to land use, soil type, soil parent material and topography; (iii) evaluate the spatial predictability of K at the canton level; and (iv) analyse the implications for K fertilization management. The overall amount of soil total K averaged 13.6g·kg−1 with significant variations across the sites (5.1–22.1g·kg−1). The spatial distribution of total K content was influenced by relatively extended soil forming processes, as suggested by (i) a significant global spatial autocorrelation measure at the 10km scale (Moran's I=0.43); (ii) significant differences observed among soil types and soil parent materials and (iii) significant correlations with land attributes such as elevation (r=−0.51). On the other hand, available mean K forms were significantly different among land uses, with the highest mean values of available K encountered in permanent grasslands, from 46.3mg·kg−1 (water extraction) to 198mg·kg−1 (acetate ammonium+EDTA extraction). All K forms (total and available) showed similar spatial regional patterns for all spatial interpolation methods, with areas dominated by permanent grassland and crops presenting higher values. However, these trends were less pronounced for the available K forms due to the prevalence of on-farm management practices for these K forms (e.g. fertilization), likely inducing high spatial and temporal variability. This hypothesis was supported by spatial clustering of low and/or high K fertility status that could be related to local particular farming practices. Grasslands require particular attention with regard to overall high K fertility status.

Using Species Distribution Models to Predict Potential Landscape Restoration Effects on Puma Conservation.

A mosaic of intact native and human-modified vegetation use can provide important habitat for top predators such as the puma (Puma concolor), avoiding negative effects on other species and ecological processes due to cascade trophic interactions. This study investigates the effects of restoration scenarios on the puma’s habitat suitability in the most developed Brazilian region (São Paulo State). Species Distribution Models incorporating restoration scenarios were developed using the species’ occurrence information to (1) map habitat suitability of pumas in São Paulo State, Southeast, Brazil; (2) test the relative contribution of environmental variables ecologically relevant to the species habitat suitability and (3) project the predicted habitat suitability to future native vegetation restoration scenarios. The Maximum Entropy algorithm was used (Test AUC of 0.84 ± 0.0228) based on seven environmental non-correlated variables and non-autocorrelated presence-only records (n = 342). The percentage of native vegetation (positive influence), elevation (positive influence) and density of roads (negative influence) were considered the most important environmental variables to the model. Model projections to restoration scenarios reflected the high positive relationship between pumas and native vegetation. These projections identified new high suitability areas for pumas (probability of presence >0.5) in highly deforested regions. High suitability areas were increased from 5.3% to 8.5% of the total State extension when the landscapes were restored for ≥ the minimum native vegetation cover rule (20%) established by the Brazilian Forest Code in private lands. This study highlights the importance of a landscape planning approach to improve the conservation outlook for pumas and other species, including not only the establishment and management of protected areas, but also the habitat restoration on private lands. Importantly, the results may inform environmental policies and land use planning in São Paulo State, Brazil.

Climatic distribution of citrus black spot caused by Phyllosticta citricarpa. A historical analysis of disease spread in South Africa

Citrus black spot (CBS), caused by Phyllosticta citricarpa, is one of the main fungal diseases of citrus worldwide. The Mediterranean Basin is free of the disease and thus phytosanitary measures are in place to avoid the entry of P. citricarpa in the EU territory. However, the suitability of the climates present in the Mediterranean Basin for CBS establishment and spread is debated. As a case study, an analysis of climate types and environmental variables in South Africa was conducted to identify potential associations with CBS distribution. The spread of the disease was traced and georeferenced datasets of CBS distribution and environmental variables were assembled. In 1950 CBS was still confined to areas of temperate climates with summer rainfall (Cw, Cf), but spread afterwards to neighbouring regions with markedly drier conditions. Actually, the hot arid steppe (BSh) is the predominant climate where CBS develops in South Africa nowadays. The disease was not detected in the Mediterranean-type climates Csa and Csb as defined by the Koppen-Geiger system and the more restrictive Aschmann’s classification criteria. However, arid steppe (BS) climates, where CBS is prevalent in South Africa, are common in important citrus areas in the Mediterranean Basin. The most noticeable change in the environmental range occupied by CBS in South Africa was the amount and seasonality of rainfall. Due to the spread of the disease to dryer regions, the minimum annual precipitation in CBS-affected areas declined from 663 mm in 1950 to 339 mm at present. The minimum value precipitation of warmest quarter also declined from 290 to 96 mm. Strong spatial autocorrelation in CBS distribution data was detected, so further modelling efforts should consider the relative contribution of environmental variables and spatial effects to estimate the potential geographical range of CBS.

Latitudinal Variation in Termite Species Richness and Abundance along the Brazilian Atlantic Forest Hotspot

AbstractIn this study, we investigated the termites of the Brazilian Atlantic Forest, one of the most threatened biodiversity hotspots in the world, in regularly spaced sites from 7° S to 27° S latitude. To our knowledge, this is the only report of a latitudinal survey of termites at species level performed with a standardized sampling protocol. We evaluate termite diversity and abundance, and describe patterns of species composition based on feeding groups along the latitudinal gradient. We also describe the relative contribution of environmental variables to explain diversity patterns. Termite assemblages were investigated by standardized surveys at 15 Atlantic Forest sites, on six transects divided into five sections of 10 m², with 30 sections per site (or 300 m²/site), which were investigated by one trained person for one hour. Observed species richness and abundance were negatively correlated with latitude. The influence of latitude was explained mainly by variables related to temperature, precipitation and ambient energy (potential evapotranspiration). Our results also suggest that temperature exerts a greater constraint on Atlantic Forest termites than productivity, because ambient productivity increases with latitude in this forest but termite diversity decreases. Termite species richness in the Atlantic Forest showed a different pattern than those described for other organisms, increasing in diversity where the coastal‐forest strip narrows. Overall, our results indicate comparatively high termite species richness at northeastern sites and a significant impoverishment of termite assemblages in the southeastern and southern regions of the Atlantic Forest.

Effect of environmental gradients on the quantity and quality of fallen logs in Tsuga longibracteata forest in Tianbaoyan National Nature Reserve, Fujian province, China

We investigated the quantity and quality of fallen logs in different Tsuga longibracteata forest communities in the Tianbaoyan National Nature Reserve. We used redundancy analysis to determine the spatial distribution of fallen logs in the different forest communities and to analyze the relationships among stand structure, topographic factors and human disturbance. The volume, covered area, mean log length and number of fallen logs differed significantly among forest types (P 0.05). The log volume and covered area in different forest types showed the following trend: T. longibracteata pure forest elevation > slope position > bole height > tree height > slope aspect > density > basal area > slope gradient. The relative contribution of environmental variables on the total variance was topography (76%) > disturbance (42%) > stand structure (35%). Topography and disturbance combined explained 83% of the variance. Fallen logs quantity and quality were negatively related to elevation and slope position, and positively associated to human disturbance. The log volume decreased from northern to southern slopes. Environmental factors had the highest impact on class I (slightly decayed), and lowest impact on class V (highly decayed).

Scale‐dependent influence of environmental variables on species distribution: a case study on five coastal benthic species in the Baltic Sea

Statistical modelling can be used to relate biological survey data to environmental factors, thereby providing a basis for predictive mapping of species or communities. Although environmental variables vary and influence biota at different scales, models are often fitted without discussion of how scale dependency influences the results. In this study, we analysed the relative importance of environmental factors for the distribution of aquatic species as a function of extent, using data on the cover of five common benthic species (four macrophytes and one animal), from 1731 sites along the Swedish Baltic Sea coast. We modelled the cover and distribution of the five species in relation to salinity, depth, slope, wave exposure and substrate in scale steps from 25 to 1500 km, and analysed the relative contribution of the environmental variables to each species model. The average total deviance explained by the models was generally quite high, and decreased with increasing scale for all macrophyte species, while it increased for the animal, the Baltic Sea blue mussel Mytilus edulis. The relative contribution of different environmental variables changed with scale, and responses also differed between species. The average contribution of salinity increased for all species when moving from local to Baltic Sea scale, and for the Baltic Sea blue mussel it was the single most important factor at the Baltic Sea scale. The average contribution of depth decreased with increasing scale for all species. However, regardless of scale, depth was the most important environmental factor to explain the distribution of all but one of the investigated macrophyte species. This shows that fine scale predictor variables can be of major importance also for species distribution models covering large areas.

Response of fish assemblages to water quality in boreal rivers

The relationship between fluvial fish assemblages and environmental variables including water quality was studied by nonmetric multidimensional scaling (NMS) and generalised regression neural network (GRNN). Fish assemblages in the studied boreal rivers in Central Finland showed a higher response to water quality than to other environmental variables such as altitude and river width. Of the water quality parameters, total phosphorus, oxygen saturation in winter and solids had the highest influence on fish assemblages. Brown trout (Salmo trutta L.) responded to water quality strongly by favouring pristine waters. Among other fish species, the responses were lighter, and the relative contribution of environmental variables varied. Percentage of fishless sites, i.e. no catch in electrofishing, was 4.4% when pH ≥ 6, and 38.2% when pH < 6. However, the most effective way to influence the fish assemblage composition, and to raise the fish-based FIFI integrity index value, would be to reduce loading of solids and phosphorus, rather than depressing acidification.

Regional and local environmental factors structuring undisturbed benthic macroinvertebrate communities in the Mondego River basin, Portugal

The relative contribution of environmental variables in explaining the structure variation of undisturbed benthic macroinvertebrate communities was investigated over three seasons at 18 sites of the Mondego River basin, Portugal. Sampling sites located at distinct altitudes (2-840m), presented a consistent pattern of water conductivity values through seasons, always showing the highest values in lowland water-courses. Streams showed highly variable hydraulic conditions from intermittent to perennial systems, so discharge-related factors were expected to influence their communities' structure. Ninety-nine macroinvertebrate taxa were recorded at the undisturbed sites, ranging from a minimum of 32 during spring to a maximum of 63 during summer. Taxon richness at a site was the only significantly different descriptive measure among seasons. Regression analysis applied to undisturbed data revealed spring (-), channel width (-), dissolved oxygen (+), total dissolved solids (-) and chlorophyll-a (-) as the strongest predictors of family richness, while invertebrate abundance was highly related to organic content of sediment (+) and levels of dissolved oxygen (+) (ordered by significance). Community family composition was related with environmental variables through canonical correspondence analyses which showed that the most significant natural environmental-gradient affecting invertebrate distribution was a spatial variation of sediment grain size, altitude and stream bed geology explained by conductivity. As expected, discharge-related variables such as dissolved oxygen, current speed and channel width were main factors in defining a secondary seasonal gradient. This was reinforced by the results of a similarity percentage breakdown procedure, which showed differences in the invertebrate composition between seasons and between sites within the same season. These findings recognize the importance of local factors but also indicate the significance of larger-scale factors such as stream geology and altitude in structuring the undisturbed benthic invertebrate communities in this area.