Ecosystem size-induced environmental fluctuations affect the temporal dynamics of community assembly mechanisms

Understanding processes that determine community membership and abundance is important for many fields from theoretical community ecology to conservation. However, spatial community studies are often conducted only at a single timepoint despite the known influence of temporal variability on community assembly processes. Here we used a spatiotemporal study to determine how environmental fluctuation differences induced by mesocosm volumes (larger volumes were more stable) influence assembly processes of aquatic bacterial metacommunities along a press disturbance gradient. By combining path analysis and network approaches, we found mesocosm size categories had distinct relative influences of assembly process and environmental factors that determined spatiotemporal bacterial community composition, including dispersal and species sorting by conductivity. These processes depended on, but were not affected proportionately by, mesocosm size. Low fluctuation, large mesocosms primarily developed through the interplay of species sorting that became more important over time and transient priority effects as evidenced by more time-delayed associations. High fluctuation, small mesocosms had regular disruptions to species sorting and greater importance of ecological drift and dispersal limitation indicated by lower richness and higher taxa replacement. Together, these results emphasize that environmental fluctuations influence ecosystems over time and its impacts are modified by biotic properties intrinsic to ecosystem size.

Emergent dual scaling of riverine biodiversity

A prevailing paradigm suggests that species richness increases with area in a decelerating way. This ubiquitous power law scaling, the species–area relationship, has formed the foundation of many conservation strategies. In spatially complex ecosystems, however, the area may not be the sole dimension to scale biodiversity patterns because the scale-invariant complexity of fractal ecosystem structure may drive ecological dynamics in space. Here, we use theory and analysis of extensive fish community data from two distinct geographic regions to show that riverine biodiversity follows a robust scaling law along the two orthogonal dimensions of ecosystem size and complexity (i.e., the dual scaling law). In river networks, the recurrent merging of various tributaries forms fractal branching systems, where the prevalence of branching (ecosystem complexity) represents a macroscale control of the ecosystem’s habitat heterogeneity. In the meantime, ecosystem size dictates metacommunity size and total habitat diversity, two factors regulating biodiversity in nature. Our theory predicted that, regardless of simulated species’ traits, larger and more branched “complex” networks support greater species richness due to increased space and environmental heterogeneity. The relationships were linear on logarithmic axes, indicating power law scaling by ecosystem size and complexity. In support of this theoretical prediction, the power laws have consistently emerged in riverine fish communities across the study regions (Hokkaido Island in Japan and the midwestern United States) despite hosting different fauna with distinct evolutionary histories. The emergence of dual scaling law may be a pervasive property of branching networks with important implications for biodiversity conservation.

Influence of Tangible Ecosystem Goods Encroachment on Host Community Well-being: A Case of Bwindi Impenetrable National Park

The study was set out to investigate how encroachment on ecosystem tangible goods improves the host community well-being. The problem was that over harvesting of the tangible goods resulted in the degradation of the ecosystem and thus affected the quality and quantity of the tangible goods harvested and thus negatively affected the host community's wellbeing. The study had threefold objectives and these were; to describe the ecosystem destruction trends; to determine the driving forces behind the encroachment of the park ecosystems and, to ascertain the different ecosystem tangible goods harvested from the park. The literature of the study focused on local community wellbeing and encroachment as well as the causes of rampant encroachment of the ecosystems both in unprotected areas and in protected areas. The methodology of this study was majorly descriptive and considered the population of 40 households and a sample of 32 households as well the household used as a sampling unit. The results indicated that encroachment on ecosystems occurred and as a result the ecosystem size dwindled over the past three decades. Also, the results revealed that the major cause of this encroachment was scarcity of land and poverty. Whereas the most demanded ecosystem resources were timber and fuel wood. It was concluded that because there was no wellbeing amongst the host community due to poverty and scarcity of land, they were forced to encroach on the ecosystem resources. It was therefore recommended that the park and host community should find mechanisms to empower the host community in order to minimize encroachment rates.

Ecosystem size and complexity are extrinsic drivers of food chain length in branching networks

Understanding the drivers of food chain length in natural communities has intrigued ecologists since the publication of ‘food cycles’ by Elton in the early 20th century. Proposed drivers of food chain length have included extrinsic controls such as productivity, disturbance regime, and ecosystem size, as well as intrinsic factors including food web motifs. However, current theories have largely assumed simple, two-dimensional habitat architectures, and may not be adequate to predict food chain length in ecosystems which have a complex, branching structure. Here, we develop a spatially explicit theoretical model which provides an integrated framework for predicting food chain length in branching networks. We show food chain length responds independently to both ecosystem size and complexity, and that these responses are contingent upon other extrinsic and intrinsic controls. Our results show that accounting for ecosystem complexity is an important driver of food chain length and may reconcile inconsistent results from empirical studies of food chain length in river ecosystems.

TEEB-Russia: Towards National Ecosystem Accounting

Russia’s ecosystems and ecosystem services (ES) are critical not only for the country’s economy and well-being of the people but also for maintaining biodiversity and biosphere regulation around the world. Thus, the introduction of ecosystem accounting in Russia is an urgent national and international goal to which the TEEB-Russia project is dedicated. In this publication, we briefly review and discuss the main project results. Based on currently available open statistical and cartographic data, TEEB-Russia project conducted the first national assessment of terrestrial ES in Russia to derive methodological approaches to national ecosystem accounting. A range of indicators were used to assess the ES provided by ecosystems (potential) as well as the level of demand and consumption of ES by Russia’s regions, both for populations and economies. Indicators of ecosystem assets include extent (ecosystem size) and condition (productivity, phytomass, bird and plant species diversity). An analysis of the correlations between indicators of ES and ecosystem assets showed that a system of national ecosystem accounting in Russia should be regionally differentiated to take account of the strong heterogeneity of natural conditions and the socio-economic development at this level. Decision-making in spatial planning and ecosystem management should carefully consider the difference between causal relationships between indicators and correlations that arise from the simultaneous response of indicators to changes in other factors. Differences in relationships between indicators at different spatial scales should also be taken into account.

Ecosystem size and complexity dictate riverine biodiversity

Larger ecosystems support more species; this ubiquitous pattern is the foundation of current conservation schemes. However, many ecosystems possess a complex spatial structure that cannot be represented by area, and the role of such complexity in scaling biodiversity is largely unknown. Here, we use theory and extensive fish community data from two distinct geographic regions (Japan and United States) to show that ecosystem size and complexity dictate riverine biodiversity. We found that larger and more branched ‘complex’ river networks harbored greater species richness due to increased space and environmental heterogeneity. The complexity effect was comparable to the size effect, and this pattern has emerged regardless of ecological contexts. The dual control of biodiversity may be a pervasive feature that has far-reaching implications for biodiversity conservation.One sentence summaryThis study provides the first evidence that ecosystem size and complexity play comparable roles in regulating biodiversity.

How Can Be Lotic Ecosystem Size More Precisely Estimated? Comparing Different Approximations in Pre-Pyrenean and Pyrenean Mountains

Rivers are among the most biodiverse and endangered ecosystems on earth. In Europe, concern over their conservation promoted the development of legal instruments for habitat and species conservation, the Habitats Directive, and water resource management, the Water Framework Directive. This legal protection demanded the estimate of river ecosystem surface for different purposes. Different approaches allow river surface to be measured at a low cost. Some accurate techniques like satellite images or LiDAR (Light Detection and Ranging) do not always work at a large scale or for streams and small rivers. We discuss here the use of the traditional hydraulics relationship between drainage area and bankfull width as a good approach to river surface estimation. We confirm that the use of this cheap and simple method could be a good approach to estimate river surface. However, we also proved that the development of regional curves, i.e., to establish the empirical relationship based on study area data, constitutes an essential improvement to estimation.

Food Chain Length Associated with Environmental Factors Affected by Large Dam along the Yangtze River

Food chain length (FCL) is a critical measure of food web complexity that influences the community structure and ecosystem function. The FCL of large subtropical rivers affected by dams and the decisive factors are far beyond clear. In this study, we used stable isotope technology to estimate the FCL of fish in different reaches of the main stream in the Yangtze River and explored the key factors that determined the FCL. The results showed that FCL varied widely among the studied areas with a mean of 4.09 (ranging from 3.69 to 4.31). The variation of FCL among river sections in the upstream of the dam was greater than that in the downstream. Regression analysis and model selection results revealed that the FCL had a significant positive correlation with ecosystem size as well as resource availability, and FCL variation was largely explained by ecosystem size, which represented 72% of the model weight. In summary, our results suggested that ecosystem size plays a key role in determining the FCL in large subtropical rivers and large ecosystems tend to have a longer food chain. Additionally, the construction of the Three Gorges Dam has been speculated to increase the FCL in the impoundment river sections.

Effects of species traits and ecosystem characteristics on species detection by eDNA metabarcoding in lake fish communities

Although environmental DNA (eDNA) metabarcoding is acknowledged to be an exceptionally useful and powerful tool for monitoring surveys, it has limited applicability, particularly for nationwide surveys. To evaluate the performance of eDNA metabarcoding in broad-scale monitoring, we examined the effects of species ecological/biological traits and ecosystem characteristics on species detection rates and the consequences for community analysis. We conducted eDNA metabarcoding on fish communities in 18 Japanese lakes on a country-wide scale. By comparing species records, we found that certain species traits, including body size, body shape, saltwater tolerance, and habitat preferences, influenced eDNA detection. We also found that the proportion of species detected decreased significantly with an increase in lake surface area, owing to an ecosystem-size effect on species detection. We conclude that species traits, including habitat preferences and body size, and ecosystem size should be taken into consideration when assessing the performance of eDNA metabarcoding in broad-scale monitoring.