Relative Importance Of Abiotic Factors Research Articles

Prey resources are equally important as climatic conditions for predicting the distribution of a broad‐ranged apex predator

AbstractAimA current biogeographic paradigm states that climate regulates species distributions at continental scales and that biotic interactions are undetectable at coarse‐grain extents. However, advances in spatial modelling show that incorporating food resource distributions are important for improving model predictions at large distribution scales. This is particularly relevant to understand the factors limiting the distribution of widespread apex predators whose diets are likely to vary across their range.LocationNeotropical Central and South America.MethodsThe harpy eagle (Harpia harpyja) is a large raptor, whose diet is largely comprised of arboreal mammals, all with broad distributions across Neotropical lowland forest. Here, we used a hierarchical modelling approach to determine the relative importance of abiotic factors and prey resource distribution on harpy eagle range limits. Our hierarchical approach consisted of the following modelling sequence of explanatory variables: (a) abiotic covariates, (b) prey resource distributions predicted by an equivalent modelling for each prey, (c) the combination of (a) and (b), and (d) as in (c) but with prey resources considered as a single prediction equivalent to prey species richness.ResultsIncorporating prey distributions improved model predictions but using solely biotic covariates still resulted in a high‐performing model. In the Abiotic model, Climatic Moisture Index (CMI) was the most important predictor, contributing 76% to model prediction. Three‐toed sloth (Bradypus spp.) was the most important prey resource, contributing 64% in a combined Abiotic‐Biotic model, followed by CMI contributing 30%. Harpy eagle distribution had high environmental overlap across all individual prey distributions, with highest coincidence through Central America, eastern Colombia, and across the Guiana Shield into northern Amazonia.Main ConclusionsWith strong reliance on prey distributions across its range, harpy eagle conservation programmes must therefore consider its most important food resources as a key element in the protection of this threatened raptor.

Abiotic Regulation: Landslide Scale and Altitude Regulate Functional Traits of Regenerating Plant Communities After Earthquakes

Regeneration and assembly of a plant community after a large-scale natural disturbance are affected by many factors. The relative importance of abiotic factors represented by the external environment and the biological factors inside the plant community during this process is still unexplored. This work investigated the regions affected by the Wenchuan earthquake, focusing on areas with the highest intensity (XI degrees) of this earthquake, and the process of community assembly through functional traits on landslides. The aim of this study was to understand the importance of factors influencing community assembly from the perspective of functional traits. The main conclusion is presented as follows: after the regeneration of large earthquake-induced landslides, community-level functional traits covering many plant organs, such as roots, stems, leaves and seeds, are obviously different from those unaffected by landslides. Functional traits do not show strong phylogenetic conservatism. Overall, community traits are divergent or random, and the degree of divergence among the different traits varies. Species composition and alpha diversity have minimal effect on community functional traits during the process of landslide restoration. Landslide scale and altitude significantly affected community-level functional traits in the process of community assembly. All the findings suggested that the functional traits of regenerating vegetation after the earthquake changed significantly and that the functional traits depended more on abiotic regulation than on evolutionary and species-specific factors.

The daily effect is more important than the diurnal effect when shaping photosynthetic picoeukaryotes (PPEs) communities in Lake Taihu at a small temporal scale.

As major primary producers in aquatic systems, the diversity and community composition dynamics of photosynthetic picoeukaryotes (PPEs) have been investigated in recent years. Here, we explored the 3-day diurnal succession of the PPE community in a highly eutrophic lake in early spring using a combination of flow cytometric sorting and high-throughput sequencing. Our results showed that the PPEs were the dominant group of autotrophic picophytoplankton, although they had relatively low diversity and were dominated by the Stephanodiscaceae family in early spring in Lake Taihu. Furthermore, PPE abundance was significantly higher at night than during the day, probably due to their high specific rate of carbon uptake during the day and rapid proliferation at night. Several environmental variables had a significant influence on the PPE community composition, and the daily effect was more important than the diurnal effect when shaping the PPE community in Lake Taihu at a temporal scale of 3 days. Furthermore, based on the variation partitioning analysis (VPA), the relative importance of abiotic factors (deterministic processes) to short-term succession was low, explaining only 20.44% of the PPE community variation. We therefore conclude that stochastic processes determined PPE community assembly over a short temporal scale based on a neutral community model (NCM).

Positive co‐occurrence between feeding‐associative savannah fishes depends on species and habitat

Abstract Understanding the relative importance of abiotic factors and biotic interactions in determining species co‐occurrence is a fundamental goal in ecology. Most studies of ecology of freshwater fishes have focused on negative biotic interactions (competition and predation), and much less is known about more positive interactions. The goal of this study was to quantify the relative importance of habitat features and biotic interactions (positive and negative) on co‐occurrence of three pairs of feeding‐associative Leporinus (L.) fishes in rivers of central Brazil (L. friderici–L. octomaculatus, L. striatus–L. octomaculatus, L. friderici–L. striatus). We sampled 146 sites on two rivers of central Brazil and used two‐species occupancy models to examine the relative importance of habitat features and commensalistic feeding association for determining co‐occurrence of the three species pairs. Using an information–theoretic framework, we compared weight‐of‐evidence for models containing effects of habitat covariates only, biotic interactions only, and their combination. Model evidence supported the hypothesis that feeding activity of L. friderici facilitates occurrence of L. octomaculatus and that the interaction is mediated by habitat covariates. In contrast, most evidence suggested that occurrence of L. striatus is independent of L. friderici, and is instead determined entirely by habitat features. Evidence for facilitation of L. octomaculatus by L. striatus was mixed—there is evidence supporting the habitat‐only hypothesis as well as habitat‐mediated facilitation. Our results suggest that positive interactions can affect co‐occurrence among freshwater fishes, at least for species that interact strongly. More facultative interactions, such as those between L. friderici and L. striatus, may be less important, at least in certain abiotic contexts. This study indicates that biotic interactions between species of freshwater fish can be evident beyond the microhabitat scale to positively influence species co‐occurrence and adds to evidence from other groups of freshwater organisms indicating the importance of biotic interactions in facilitating species co‐occurrence.

Plasticity in root symbioses following shifts in soil nutrient availability during long‐term ecosystem development

Abstract The vast majority of terrestrial plants form root symbioses with arbuscular mycorrhizal (AM) fungi to enhance nutrient (particularly phosphorus, P) acquisition. However, some plant species also form dual symbioses involving ectomycorrhizal (ECM) fungi, with a subset of those also forming triple symbioses also involving dinitrogen (N2)‐fixing bacteria. It has been suggested that these plants show plasticity in root symbioses to optimise nutrient acquisition depending on the type and strength of soil nutrient limitation (e.g., N vs. P), yet empirical evidence remains limited. Alternatively, the degree of investment or “preference” in particular root symbioses might simply reflect differences in inoculum potential among soils of contrasting nutrient availability, reflecting adaptations of root symbionts to different edaphic conditions. Here, we grew two co‐occurring plant species forming triple (AM/ECM/N2‐fixing; Acacia rostellifera) or dual (AM/ECM; Melaleuca systena) symbioses in soils of increasing age and contrasting nutrient availability from an Australian long‐term soil chronosequence to disentangle the relative importance of abiotic factors (e.g., soil nutrient availability and stoichiometry) and biotic factors (e.g., soil inoculum potential) in determining root colonisation patterns and functional outcomes of these multiple root symbioses. For both plant species, we found clear hump‐shaped plant growth patterns along the pedogenesis‐driven gradient in soil nutrient availability, with peak growth in intermediate‐aged soils, while high levels of mycorrhizal colonisation by the “preferred” root symbionts were maintained across all soils. We found large increases (540%) in foliar manganese concentrations with increasing soil age and declining P availability, suggesting that plants may be relying on the release of carboxylates to help acquire P in the most P‐impoverished soils. Finally, we found that soil abiotic properties, such as strong differences in soil nutrient availability, are generally more important than soil inoculum potential in explaining these shifts in our plant and root responses. Synthesis. Our study suggests that plants capable of forming multiple root symbioses show plasticity in their nutrient‐acquisition strategies following shifts in soil nutrients during long‐term ecosystem development, yet maintain a preference for certain root symbionts despite changes in soil microbial inoculum.

Spatial scale dependence of factors driving climate regulation services in the Americas

AbstractAimA key hypothesis in macroecology is that the relative importance of factors driving ecological phenomena changes with spatial scale. However, studies on ecosystem services usually ignore this. Here, we test how the importance of factors related to climate regulation services varies with spatial extent (i.e., area of assessment) and how covariation among factors affects scale dependencies.LocationThe Americas.Time periodPresent.Major taxa studiedPlants.MethodsWe combined a multi‐model inference framework with variance partitioning to quantify the importance of factors that could potentially influence climate regulation services (i.e., albedo, evapotranspiration and primary productivity). We quantified abiotic (climate, soil, heterogeneity in soils/topography), biotic (open vegetation, forest area and biomass, plant functional traits) and anthropogenic (forest fragmentation, managed vegetation, non‐vegetated surfaces) conditions and tested their importance in relation to climate regulation services at spatial extents ranging from 9 × 103 to 1 × 106 km2.ResultsWe found that the importance of abiotic factors in relation to climate regulation services increases with spatial extent. However, we found no evidence for a change from primarily biotically to abiotically driven climate regulation services with increasing spatial extent. All spatial extent dependencies were heavily influenced by covariation between abiotic, biotic and anthropogenic factors. After accounting for covariation, we found a primacy of abiotic factors as drivers of climate regulation services across spatial extents. Biotic and anthropogenic factors were less important than abiotic factors, and their independent effects were conserved across spatial extents.Main conclusionsOur results show that the relative importance of abiotic factors related to climate regulation services depends on spatial extent. Biotic and anthropogenic factors are less important for climate regulation services than abiotic factors, and this hierarchy is scale invariant. Our findings suggest that spatial extent dependence needs to be quantified and assessed in climate‐change mitigation projects that focus on ecosystem services.

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.

Soil organic carbon and soil structure are driving microbial abundance and community composition across the arid and semi-arid grasslands in northern China

Microbial biogeography through the study of the assembly rules of microbes has the potential to yield ecological information that is generalizable for a wide range of microorganisms. Here we performed a large-scale field investigation of the distribution patterns of microbes across the arid and semi-arid grassland ecosystems covering an area of 690,000 km2 in northern China. Soil microbial abundance and community composition were examined through quantifying microbial phospholipid fatty acids (PLFAs) at fifty sampling sites along environmental gradients. A multi-model inference analysis identified soil organic carbon (SOC) as a key driving factor for microbial biomass and quantified its effect. Structural equation models (SEM) were further fitted to the data to provide a better mechanistic resolution of direct and indirect pathways that connected PLFAs and environmental variables. The SEM analysis also supported that SOC was the main positive predictor of microbial biomass, while MAT served as the main negative factor via an indirect pathway. To visualize complex relationships between microbial community and environmental variables we engaged in a redundancy analysis. The result showed that PLFA profiles could be largely explained by the soil variables including soil structure (PSD) and pH. Overall, our report through the analysis of an unprecedented amount of primary data yields unique insights into the relative importance of abiotic factors in shaping microbial communities at large scales.

Role of topography and soils in grassland structuring at the landscape and community scales

Abstract The relative importance of abiotic factors in community assembly is debated and thought to be dependent on the scale. I investigated the relative role of topography and soils as structuring agents at the landscape and the community scales in 126 subalpine calcareous grasslands in the Pyrenees, in terms of species composition and abundance. I wished to know: (1) the role of abiotic factors in the organization of plant communities across the landscape; (2) how much of the variation in community distribution was accounted for by abiotic factors; and (3) how well their role applied to the distribution of dominant species at the landscape and the community scales. The hypothesis was: abiotic factors play an important role in community distribution in the landscape, but species interactions are more important within communities. Multivariate methods generated four communities, organized in two contrasting groups along the main vegetation axis, which explained 13% of the variation: mesic grasslands ( Nardus stricta and Festuca nigrescens communities) and xeric grasslands ( Carex humilis and Festuca gautieri communities). Mesic communities were more acidic and fertile than xeric communities. Changes in the abiotic environment, accounting for up to 80% of the variation in the vegetation, were smooth, while the transition between xeric and mesic grasslands was sharp in terms of species composition. The distribution in the landscape of the first main species from each community was closely related to abiotic factors, which modeled poorly the abundance of the main species at smaller scales. At the within-community scale, the explanatory power of biotic relationships was community dependent, producing the most significant models for plants highly dominant within their communities, such as N. stricta and F. gautieri . Contrary to current hypothesis, there was a shift from mainly positive relationships among dominant species in fertile mesic communities to mainly negative in infertile xeric ones.