The function-dominance correlation drives the direction and strength of biodiversity-ecosystem functioning relationships

Love Thy Neighbour? Tropical Tree Growth and Its Response to Climate Anomalies Is Mediated by Neighbourhood Hierarchy and Dissimilarity in Carbon- and Water-Related Traits

Taxonomic diversity effects on forest productivity and response to climate extremes range from positive to negative, suggesting a key role for complex interactions among neighbouring trees. To elucidate how neutral interactions, hierarchical competition and resource partitioning between neighbours' shape tree growth and climate response in a highly diverse Amazonian forest, we combined 30 years of tree censuses with measurements of water- and carbon-related traits. We modelled individual tree growth response to climate and neighbourhood to disentangle the relative effect of neighbourhood densities, trait hierarchies and dissimilarities. While neighbourhood densities consistently decreased growth, trait dissimilarity increased it, and both had the potential to influence climate response. Greater water conservatism provided a competitive advantage to focal trees in normal years, but water-spender neighbours reduced this effect in dry years. By underlining the importance of density and trait-mediated neighbourhood interactions, our study offers a way towards improving predictions of forest dynamics.

Human activities weaken the positive effects of soil abiotic factors and biodiversity on ecosystem multifunctionality more than drought: A case study in China's West Liao River Basin

Watershed-scale ecosystem biodiversity has been adversely affected by human disturbances and climate change for many years, leading to degradation of ecological functions (i.e., decreased ecosystem multifunctionality, EMF). However, the driving factors and their mechanisms are unclear. Here, we analyzed the effects of human activities, climate, biodiversity, and soil abiotic factors on EMF in China's West Liao River Basin along a natural drought intensity gradient. The beneficial effects of biodiversity on EMF were influenced by the drought intensity; biodiversity increased plant density in humid zones, plant diversity in semi-arid zones, and soil microbial diversity in arid zones, thereby improving watershed EMF and indicating that drought determines the direction and strength of the effects of biodiversity on EMF. The relative abundances of soil microbial keystone taxa such as Actinomycetes and Gemmatimonadetes were the most important predictors of EMF. These results indicate that any loss of plant community diversity or plant density, soil microbial diversity, and the abundance of keystone microbial taxa could reduce EMF. Human activities and drought directly decreased EMF, but also indirectly reduced EMF by reducing soil pH and soil water content (SWC), plant diversity. As human activity increases, EMF's sensitivity to drought increases, and this implies that in regions with high levels of human activity, the effects of climate warming on EMF may be greater than expected. Overall, human activities (including direct, indirect, and total effects) are primary drivers of changes of biodiversity and soil abiotic factors in watershed ecosystems, and regulate the watershed's EMF. The results provide new insights to improve predictions of the direction, magnitude, and regulation mechanisms of EMF and its responses to global climate change.

Multiple Long-Term, Landscape-Scale Data Sets Reveal Intraspecific Spatial Variation in Temporal Trends for Bird Species

Quantifying temporal changes in species occurrence has been a key part of ecology since its inception. We quantified multidecadal site occupancy trajectories for 18 bird species in four independent long-term, large-scale studies (571 sites, ~1000 km latitude) in Australia. We found evidence of a year × long-term study interaction in the best-fitting models for 14 of the 18 species analysed, with differences in the temporal trajectories of the same species in multiple studies consistent with non-stationarity. Non-stationarity patterns in occupancy were not related to the distance from a species niche centroid; species in locations further from their niche centroid did not demonstrate differing temporal trajectories to those closer to their niche centroid. Furthermore, temporal trajectories of species were not associated with climatic values for each study relative to their niche. Our findings demonstrate the need for multiple long-term studies across a species range, especially when tailoring conservation decisions for populations.

Woody plant species richness and productivity relationship in a subtropical forest: The predominant role of common species

A long-standing key issue for examining the relationships between biodiversity and ecosystem functioning (BEF), such as forest productivity, is whether ecosystem functions are influenced by the total number of species or the properties of a few key species. Compared with controlled ecosystem experiments, the BEF relationships in secondary forest remain unclear, as do the effects of common species richness and rare species richness on the variation in ecosystem functions. To address this issue, we conducted field surveys at five sampling sites (1 ha each) with subtropical secondary evergreen broad-leaved forest vegetation. We found (1) a positive correlation between species richness and standing aboveground biomass (AGB); (2) that common species were primarily responsible for the distribution patterns of species abundance and dominance; although they accounted for approximately 25% of the total species richness on average, they represented 86-91% of species abundance and 88-97% of species dominance; and (3) that common species richness could explain much more of the variation in AGB than total species richness (common species plus rare species) at both the site and plot scales. Because rare species and common species were not equivalent in their ability to predict productivity in the biodiversity-ecosystem productivity model, redundant information should be eliminated to obtain more accurate results. Our study suggested that woody plant species richness and productivity relationship in subtropical forest ecosystem can be explained and predicted by a few common species.

Short-Term Responses of Alpine Vegetation to the Removal of Dominant versus Sparse Species

The mass ratio hypothesis posits that ecosystem functions are predominantly influenced by the dominant species. However, it remains unclear whether a species must be abundant to exert functional dominance. We conducted a removal experiment in an alpine grassland near Pudacuo National Park, Yunnan, China, to assess the community and ecosystem impacts of the removed species. We implemented four treatments as follows: exclusive removal of the most abundant species (Blysmus sinocompressus), exclusive removal of a sparse species with high individual biomass (Primula secundiflora), simultaneous removal of both species, and a control with no removals. Results showed that removing B. sinocompressus significantly reduced biomass production, supporting the mass ratio hypothesis, while removal of P. secundiflora had negligible effects. B. sinocompressus removal positively impacted community metrics like coverage, species evenness, and the Shannon diversity index, but not species richness, likely due to its spatial dominance. Conversely, P. secundiflora removal had minimal community impact, probably due to its limited influence on nearby species. This study underscores the proportionate roles of the dominant species in alpine grasslands, emphasizing that their community and ecosystem impacts are proportional to their abundance.

Geology Can Drive the Diversity-Ecosystem Functioning Relationship in River Benthic Diatoms by Selecting for Species Functional Traits

The biodiversity-ecosystem functioning (BEF) relationship has been studied extensively for the past 30 years, mainly in terrestrial plant ecosystems using experimental approaches. Field studies in aquatic systems are scarce, and considering primary producers, they mainly focus on phytoplankton assemblages, whereas benthic diatoms in rivers are considerably understudied in this regard. We performed a field study across nine rivers in Greece, and we coupled the observed field results with model simulations. We tested the hypothesis that the diversity-biomass (as a surrogate of ecosystem functioning) relationship in benthic diatoms would be affected by abiotic factors and would be time-dependent due to the highly dynamic nature of rivers. Indeed, geology played an important role in the form of the BEF relationship that was positive in siliceous and absent in calcareous substrates. Geology was responsible for nutrient concentrations, which, in turn, were responsible for the dominance of specific functional traits. Furthermore, model simulations showed the time dependence of the BEF form, as less mature assemblages tend to present a positive BEF. This was the first large-scale field study on the BEF relationship of benthic diatom assemblages, offering useful insights into the function and diversity of these overlooked ecosystems and assemblages.

A Conceptual Framework to Integrate Biodiversity, Ecosystem Function, and Ecosystem Service Models

Global biodiversity and ecosystem service models typically operate independently. Ecosystem service projections may therefore be overly optimistic because they do not always account for the role of biodiversity in maintaining ecological functions. We review models used in recent global model intercomparison projects and develop a novel model integration framework to more fully account for the role of biodiversity in ecosystem function, a key gap for linking biodiversity changes to ecosystem services. We propose two integration pathways. The first uses empirical data on biodiversity-ecosystem function relationships to bridge biodiversity and ecosystem function models and could currently be implemented globally for systems and taxa with sufficient data. We also propose a trait-based approach involving greater incorporation of biodiversity into ecosystem function models. Pursuing both approaches will provide greater insight into biodiversity and ecosystem services projections. Integrating biodiversity, ecosystem function, and ecosystem service modeling will enhance policy development to meet global sustainability goals.

Multitrophic diversity and biotic associations influence subalpine forest ecosystem multifunctionality

Biodiversity across multiple trophic levels is required to maintain multiple ecosystem functions. Yet, it remains unclear how multitrophic diversity and species interactions regulate ecosystem multifunctionality. Here, combining data from nine different trophic groups (including trees, shrubs, herbs, leaf mites, small mammals, bacteria, pathogenic fungi, saprophytic fungi and symbiotic fungi) and 13 ecosystem functions related to supporting, provisioning and regulating services, we used a multitrophic perspective to evaluate the effects of elevation, diversity and network complexity on scale-dependent subalpine forest multifunctionality. Our results demonstrate that elevation and soil pH significantly modified species composition and richness across multitrophic groups and influenced multiple functions simultaneously. We provide evidence that species richness across multiple trophic groups had stronger effects on multifunctionality than species richness at any single trophic level. Moreover, biotic associations, indicating the complexity of trophic networks, were positively associated with multifunctionality. The relative effects of diversity on multifunctionality increased at the scale of the larger community compared to a scale accounting for neighbouring interactions. Our results highlight the paramount importance of scale- and context- dependent multitrophic diversity and interactions for a better understanding of mountain ecosystem multifunctionality in a changing world. This article is protected by copyright. All rights reserved.