Relative Importance Of Environmental Conditions Research Articles

Patterns of diversity in subtidal marine macrofaunal communities: Insights from a semi-enclosed bay system in the Northeast Atlantic

The complexity of describing patterns and scales of variation in the distribution of species has created a delay in our understanding of the natural world. Understanding ecological functioning is essential to develop ecosystem management projects and to uphold conservation measures. The objective of the present study was to describe the variation in the structure of subtidal marine macrofaunal communities in a semi-enclosed bay system in the Northeast Atlantic to determine the relative importance of environmental conditions (e.g., water depth and position in the Ría) and processes (e.g., colonisation). Four different sites were selected along the Ría de Vigo, two sampling sites were allocated to the outermost part of the Ría and the other two sampling sites in the middle part of the Ría, both with different depths each (4–5 m and 11–12 m), and sampled at 1-, 3-, and 6- months of colonisation. Our results suggest a distinction between the community 1 month of colonisation and the remaining, with the Mollusca and Arthropoda species responsible for creating the most dissimilarities. At a local diversity level, the communities did not reveal significant differences in the factor’s ‘depth’ or ‘position in the Ría’. Through the application of beta diversity, significant patterns of variation emerged, revealing the significant importance of the deeper sites in maintaining unique and diverse communities in that region.

Environmental conditions and litter nutrients are key determinants of soluble C, N, and P release during litter mixture decomposition

Plant litter-derived dissolved compounds leaching is an important process for soil carbon (C) sequestration and nutrient cycling. However, knowledge of the biotic and abiotic drivers of dissolved compound release from litter mixture remains limited. Here, we evaluated the loss of soluble C, N, and P during litter mixtures decomposition across an alpine treeline ecotone, and we sought to assess the relative importance of environmental conditions, litter diversity (functional dissimilarity (Rao) and community-weighted mean (CWM) traits), litter chemistry (C quality, nutrients, and stoichiometry) and microbe drive dissolved compound release during the decomposition process. The results showed that dissolved compound release from litter mixtures deviated from predictions based on litter monoculture, with predominantly synergistic effects, and the hierarchical drivers suggested: temperature strongly regulated the release of dissolved compounds and its non-additivity. In particular, freeze-thaw cycles and seasonal snow accelerated the synergistic effects on dissolved compound loss. Litter CWM and Rao traits only accelerated soluble C release and the synergistic effects of soluble P at the last stage of dissolved compound loss, respectively. Litter nutrients directly drove the release of soluble C and P at different stages. Litter C quality and microbes regulated the release of soluble C and P via direct effects, and stoichiometry had an indirect impact, which mainly before 40 % of initial mass loss. Yet, litter chemistry showed a minimal effect on soluble N release, so controls established for the release of soluble C and P might not be valid for soluble N during decomposition. Collectively, our findings advocate the decomposition environment and litter nutrients are key factors for controlling the dissolved compounds leaching, then followed by the interactions of litter C quality, stoichiometry, litter functional diversity, and microbe, which is important for understanding soil organic matter pool and soil fertility in alpine ecosystems.

Global Sensitivity Analysis of Environmental, Water Quality, Photoreactivity, and Engineering Design Parameters in Sunlight Inactivation of Viruses.

Sunlight-mediated inactivation of microorganisms is a low-cost approach to disinfect drinking water and wastewater. The reactions involved are affected by a wide range of factors, and a lack of knowledge about their relative importance makes it challenging to optimize treatment systems. To characterize the relative importance of environmental conditions, photoreactivity, water quality, and engineering design in the sunlight inactivation of viruses, we modeled the inactivation of three-human adenovirus and two bacteriophages-MS2 and phiX174-in surface waters and waste stabilization ponds by integrating solar irradiance and aquatic photochemistry models under uncertainty. Through global sensitivity analyses, we quantitatively apportioned the variability of predicted sunlight inactivation rate constants to different factors. Most variance was associated with the variability in and interactions among time, location, nonpurgeable organic carbon (NPOC) concentration, and pond depth. The photolysis quantum yield of the virus outweighed the seasonal solar motion in the impact on inactivation rates. Further, comparison of simulated sunlight inactivation efficacy in maturation ponds under different design decisions showed that reducing pond depth can increase the log inactivation at the cost of larger land area, but increasing hydraulic retention time by adding ponds in series yielded greater improvements in inactivation.

Trait dependent roles of environmental factors, spatial processes and grazing pressure on lake phytoplankton metacommunity

Using metacommunity theory to understand the mechanisms shaping community structure is a promising framework that has been widely applied to ecological research. In lakes, the spatial pattern of phytoplankton assemblages depends on the relative importance of environmental conditions, spatial processes, and biotic interactions (e.g., grazing pressure), but the inclusion of the latter two factors was often overlooked. We tested how these three factors contributed to phytoplankton community composition in a shallow lake by separating the responses of taxonomic and trait compositions (i.e., nine species traits groups) of phytoplankton in Lake Changhu, China. Our results indicated that the taxonomic composition of phytoplankton assemblages in Lake Changhu are mainly determined by environmental factors (7.6 ± 1.3%), followed by spatial processes (4.7 ± 1.0%) and grazing pressure (2.9 ± 0.5%). However, for the nine species traits groups, relative influences of environmental, spatial and grazing factors were trait specific, suggesting that different mechanisms were responsible for community composition supporting the potential advantages of using traits in water quality assessment. More specifically, some traits (e.g., large cell size and filamentous) may be excellent candidates for biomonitoring in lakes as they are predominantly driven by environmental factors (12.4% and 17.2% for large cell size and filamentous respectively), while other traits (e.g., unicellular and non-motile) are controlled largely by spatial processes or grazing and may not be suitable as bio-indicators. We also advocate inclusion of biotic factors (e.g., grazing pressure) in community studies, since we have found relatively weak but unneglectable effects of grazing on structuring phytoplankton community (2.9 ± 0.5% for taxonomic composition while 3.1 ± 4.1% for trait composition). In general, our findings suggest that a combination of metacommunity theory and the use of traits provide a useful framework for assessing driving factors structuring phytoplankton community in lakes, and such framework can be very useful for future lake bioassessment and management efforts.

Phytoplankton community interactions and environmental sensitivity in coastal and offshore habitats

Assessing the relative importance of environmental conditions and community interactions is necessary for evaluating the sensitivity of biological communities to anthropogenic change. Phytoplankton communities have a central role in aquatic food webs and biogeochemical cycles, therefore, consequences of differing community sensitivities may have broad ecosystem effects. Using two long‐term time series (28 and 20 years) from the Baltic Sea, we evaluated coastal and offshore major phytoplankton taxonomic group biovolume patterns over annual and monthly time‐scales and assessed their response to environmental drivers and biotic interactions. Overall, coastal phytoplankton responded more strongly to environmental anomalies than offshore phytoplankton, although the specific environmental driver changed with time scale. A trend indicating a state shift in annual biovolume anomalies occurred at both sites and the shift's timing at the coastal site closely tracked other long‐term Baltic Sea ecosystem shifts. Cyanobacteria and the autotrophic ciliate Mesodinium rubrum were more strongly related than other groups to this trend with opposing relationships that were consistent across sites. On a monthly scale, biotic interactions within communities were rare and did not overlap between the coastal and offshore sites. Annual scales may be better able to assess general patterns across habitat types in the Baltic Sea, but monthly community dynamics may differ at relatively small spatial scales and consequently respond differently to future change.

Life history and environmental influences on population dynamics in sockeye salmon

Understanding linkages among life history traits, the environment, and population dynamics is a central goal in ecology. We compared 15 populations of sockeye salmon (Oncorhynchus nerka) to test general hypotheses for the relative importance of life history traits and environmental conditions in explaining variation in population dynamics. We used life history traits and habitat variables as covariates in mixed-effect Ricker models to evaluate the support for correlates of maximum population growth rates, density dependence, and variability in dynamics among populations. We found dramatic differences in the dynamics of populations that spawn in a small geographical area. These differences among populations were related to variation in habitats but not life history traits. Populations that spawned in deep water had higher and less variable population growth rates, and populations inhabiting streams with larger gravels experienced stronger negative density dependence. These results demonstrate, in these populations, the relative importance of environmental conditions and life histories in explaining population dynamics, which is rarely possible for multiple populations of the same species. Furthermore, they suggest that local habitat variables are important for the assessment of population status, especially when multiple populations with different dynamics are managed as aggregates.

Random Forests Analysis: a Useful Tool for Defining the Relative Importance of Environmental Conditions on Crown Defoliation

Defoliation is one of the most important parameters monitored in the International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests). Defoliation is an indicator for forest health and vitality. Conventional statistical analysis shows weak or not significant correlations between tree crown defoliation and climatic conditions or air pollution parameters, because of its high variability. The study aims to evaluate the most important factors among climatic, pollutants (Nox and NHy) and stand parameters affecting crown defoliation of the main European tree species (Fagus sylvatica, Picea abies, Quercus ilex, Pinus sylvestris and Quercus petraea) through application of a new and powerful statistical classifier, the random forests analysis (RFA). RFA highlighted that tree crown defoliation was mainly related to age in P. abies, to geographic location in F. sylvatica and to air pollution predictors in Q. ilex, while it was similarly linked to meteorological and air pollution predictors in P. sylvestris and Q. petraea. In this study, RFA has proven to be, for the first time, a useful tool to discern the most important predictors affecting tree crown defoliation, and consequently, it can be used for an appropriate forest management.

Higher plasticity in ecophysiological traits enhances the performance and invasion success of Taraxacum officinale (dandelion) in alpine environments

Phenotypic plasticity has long been suggested to facilitate biological invasions in changing environments, allowing a species to maintain a good ecophysiological performance. High-mountain habitats have been particularly useful for evaluation of the relative importance of environmental conditions in the colonization and invasion process, because they have heterogeneous and stressful climatic conditions, inducing photoinhibition. Light intensity is one of the most changing conditions along altitudinal gradients, showing more variability in higher altitudes. In this study, we analyzed the plasticity in photoprotective strategies and performance of the invasive Taraxacum officinale. Additionally, we tested whether higher plasticity enhances competitive ability in an alpine environment We conducted an experiment to evaluate plasticity with a second generation (F2) of T. officinale individuals from 1,600 to 3,600 m, in a greenhouse with variation in light intensity. Treatments consisted of transferring 120 individuals from each altitude to two conditions of light intensity. We then recorded concentrations of photoprotection pigment, de-epoxidation state of the xanthophyll cycle, foliar angles, photochemical efficiency by fluorescence of photosystem II, total dry biomass and flower production. Additionally, we compared plasticity in both photoprotective and performance traits between T. officinale and the co-occurring native species Hypochaeris thrincioides. Finally, we performed a manipulative experiment under two light regimes in order to assess the competitive outcome between the invasive T. officinale and the native H. thrincioides. Individuals from higher altitude showed significantly greater plasticity than individuals from lower altitude. Similarly, individuals under high light intensity showed higher levels of photoprotective pigments, biomass and flower production. On the other hand, the invasive plant species showed significantly greater plasticity than the co-occurring native species, and a strong negative impact on the biomass of the native plant. Phenotypic plasticity seems to be a successful strategy in T. officinale to compete with native species and may be positively associated with the success of invasions, being greater in individuals from more heterogeneous and stressful environments.

Succession of floodplain grasslands following reduction in land use intensity: the importance of environmental conditions, management and dispersal

Summary Classical ecological theory predicts a succession towards plant communities that are determined by environmental conditions. However, in ecological restoration, species composition often remains different from the predicted target community, compromising the success of restoration measures. We analysed the relative importance of environmental conditions, management and distance to source populations for floodplain grassland succession following re‐conversion from intensive to traditional use. The study was established at 33 grassland sites in central German river valleys. Species composition, environmental variables, past and current management, and the distance to source populations of characteristic species of traditional management (indicator species) were recorded and compared using multivariate statistics. We further tested the speed of colonization by two indicator species, Silaum silaus and Serratula tinctoria, along transects from source populations into unoccupied fields. The species composition of the successional grassland was mainly determined by elevation, total soil nitrogen, distance to remnant species‐rich grasslands and frequency of mowing or grazing. Elevation and distance were negatively, and frequency was positively related to the occurrence of late successional species. Colonization by indicator species was only dependent on the distance to source populations; other explanatory variables were not significant. Migration from adjacent source sites of S. silaus and S. tinctoria into re‐converted grasslands was slow, reaching only 40 m and 15 m after 15 years. Synthesis and applications. The results demonstrated the limitations of the deterministic view on plant succession and the high relative importance of propagule availability in grassland restoration. Natural colonization will only be successful if source populations of the target species are adjacent to the restoration sites. Artificial introduction techniques are recommended to overcome dispersal barriers.

Fish Assemblages and Environmental Conditions in the Lower Reaches of Northeastern Lake Erie Tributaries

Lake Erie and its tributaries have experienced extensive changes in environmental conditions and community structure during recent decades. To assess the relative importance of environmental conditions in determining fish community composition, fish communities and their associated environmental conditions were sampled from the lower reaches and mouths of the tributaries flowing into the northeastern basin of Lake Erie. These data were used to assess relationships between habitat and fish community composition on spatial and temporal scales using correspondence analysis and canonical correspondence analysis. Multivariate analyses revealed that the fish assemblage was size structured and related to water chemistry but also showed influences due to temperature, sampling date and aquatic macrophytes. The community composition showed the effects of biotic interactions, predominantly negative predator-prey associations, but there were also assemblage differences specific to particular tributaries and sampling methodologies.

Population studies on an endemic troglobitic beetle: geographical patterns of genetic variation, gene flow and genetic structure compared with morphometric data.

Highly specialized obligatory cave beetles endemic to the French Pyrenees offer an opportunity to investigate the relative importance of environmental conditions and ecological characteristics on the organization of genetic variability, to describe the genetic structure of populations, and to assess the extent of gene flow between local populations in relation to geologic structure. Twenty-three geographically close populations of the beetle Speonomus hydrophilus occurring both in caves (reduced fluctuations in many abiotic parameters) and under the deepest layer of soil in mountains (more exposed to climatic variations) were studied. Significant genetic differentiation at 17 allozyme loci was found among populations in close proximity, as well as among those from distant parts of range. On a larger scale, genetic differences among populations appear to result from low dispersal rates between populations. The spatial patterning observed suggests that allozyme frequencies are not responding to environmentally controlled selection. Substantial genetic divergence (F(ST) = 0.112) occurred throughout the range, with important variation in levels of genetic variability (H: 0.065-0.184) among populations. A significant level of substructuring has occurred among the populations with four major geographic areas of similarity indicated. The substructuring of the species into regions suggests an influence of paleoclimatic gradient and paleoenvironment on the population's genetic structure. Also, founder effect and reduced gene flow appear to have influenced populations in the southeastern portion of the range.