Species identity and the functioning of ecosystems: the role of detritivore traits and trophic interactions in connecting of multiple ecosystem responses

Ecosystems world-wide experience changes in species composition in response to natural and anthropogenic changes in environmental conditions. Research to date has greatly improved our understanding of how species affect focal ecosystem functions. However, because measurements of multiple ecosystem functions have not been consistently justified for any given trophic group, it is unclear whether interpretations of research syntheses adequately reflect the contributions of consumers to ecosystems. Using model communities assembled in experimental microcosms, we examined the relationship between four numerically dominant detritivore species and six ecosystem functions that underpin fundamental aspects of carbon and nitrogen cycling aboveand below-ground. We tested whether ecosystem responses to changes in detritivore identity depended upon species trait dissimilarity, food web compartment (aboveground, belowground, mixed) or number of responses considered (one to six). We found little influence of detritivore species identity on brown (i.e. soil-based) processes. Only one of four detritivore species uniquely influenced decomposition, and detritivore species did not vary in their influence on soil nitrogen pools (NO3 − and NH4 +), or root biomass. However, changes in detritivore identity influenced multiple aboveground ecosystem functions. That is, by serving as prey, ecosystem engineers and occasionally also as herbivores as well as detritivores, these species altered the strength of aboveground predator–herbivore interactions and plant–shoot biomass. Yet, dissimilarity of detritivore functional traits was not associated with dissimilarity of ecosystem functioning. These results serve as an important reminder that consumers influence ecosystem processes via multiple energy channels and that food web interactions set important context for consumer-mediated effects on multiple ecosystem functions. Given that species are being lost, gained and redistributed at unprecedented rates, we can anticipate that changes in species identity will have additional ecosystem consequences beyond those predicted by species’ primary functional role

Dirt is not dead: How Land use affects the living soil

Humans use land to grow crops for food, and the farming methods we use can influence the organisms that live in the soil. Soil organisms do important work, like decomposing organic matter and releasing nutrients for plant growth. By adding more pesticides and fertilizers to farmland,we can producemore crops in a smaller space. But those methods can also harm soil organisms and the work that they do. In contrast,we can use gentlermethods to growcrops,which are better for soil animals, but those methods require more land. People in all countries need food from crops to live healthy lives. Because we all share one land surface, when we decide how to use land, we need to remember how agriculture influences soil animals

A field facility to simulate climate warming and increased nutrient supply in shallow aquatic ecosystems

Global warming and excess nitrogen deposition can exert strong impacts on aquatic populations, communities, and ecosystems. However, experimental data to establish clear cause-and-effect relationships in naturally complex field conditions are scarce in aquatic environments. Here, we describe the design and performance of a unique outdoor enclosure facility used to simulate warming, increased nitrogen supply, and both factors combined in a littoral freshwater wetland dominated by common reed, Phragmites australis. The experimental system effectively simulated a 2.8°C climate warming scenario over an extended period, capturing the natural temperature variations in the wetland at diel and seasonal scales with only small deviations. Excess nitrogen supply enhanced nitrate concentrations especially in winter when it was associated with increased concentration of ammonium and dissolved organic carbon. Nitrogen also reduced dissolved oxygen concentrations, particularly in the summer. Importantly, by stimulating biological activity, warming enhanced the nitrogen uptake capacity of the wetland during the winter, emphasizing the need for multifactorial global change experiments that examine both warming and nitrogen loading in concert. Establishing similar experiments across broad environmental gradients holds great potential to provide robust assessments of the impacts of climate change on shallow aquatic ecosystem

Elevated CO\u3csub\u3e2\u3c/sub\u3e and warming shift the functional composition of soil nematode communities in a semiarid grassland

Climate change can alter soil communities and functions, but the consequences are uncertain for most ecosystems. We assessed the impacts of climate change on soil nematodes in a semiarid grassland using a 7-year, factorial manipulation of temperature and [CO2]. Elevated CO2 and warming decreased the abundance of plant-feeding nematodes and nematodes with intermediate to high values on the colonizer-persister scale (cp3-5), including predators and omnivores. Thus, under futuristic climate conditions, nematode communities were even more dominated by r-strategists (cp1-2) that feed on bacteria and fungi. These results indicate that climate change could alter soil functioning in semiarid grasslands. For example, the lower abundance of plant-feeding nematodes could facilitate positive effects of elevated CO2 and warming on plant productivity. The effects of elevated CO2 and warming on nematode functional composition were typically less than additive, highlighting the need for multi-factor studies

Biotic interactions as mediators of context-dependent biodiversity-ecosystem functioning relationships

Biodiversity drives the maintenance and stability of ecosystem functioning as well as many of nature’s benefits to people, yet people cause substantial biodiversity change. Despite broad consensus about a positive relationship between biodiversity and ecosystem functioning (BEF), the underlying mechanisms and their context-dependencies are not well understood. This proposal, submitted to the European Research Council (ERC), aims at filling this knowledge gap by providing a novel conceptual framework for integrating biotic interactions across guilds of organisms, i.e. plants and mycorrhizal fungi, to explain the ecosystem consequences of biodiversity change. The overarching hypothesis is that EF increases when more tree species associate with functionally dissimilar mycorrhizal fungi. Taking a whole-ecosystem perspective, we propose to explore the role of tree-mycorrhiza interactions in driving BEF across environmental contexts and how this relates to nutrient dynamics. Given the significant role that mycorrhizae play in soil nutrient and water uptake, BEF relationships will be investigated under normal and drought conditions. Resulting ecosystem consequences will be explored by studying main energy channels and ecosystem multifunctionality using food web energy fluxes and by assessing carbon storage. Synthesising drivers of biotic interactions will allow us to understand context-dependent BEF relationships. This interdisciplinary and integrative project spans the whole gradient from local-scale process assessments to global relationships by building on unique experimental infrastructures like the MyDiv Experiment, iDiv Ecotron and the global network TreeDivNet, to link ecological mechanisms to reforestation initiatives. This innovative combination of basic scientific research with real-world interventions links trait-based community ecology, global change research and ecosystem ecology, pioneering a new generation of BEF research and represents a significant step towards implementing BEF theory for human needs

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

Community composition is a primary determinant of how biodiversity change influences ecosystem functioning and, therefore, the relationship between biodiversity and ecosystem functioning (BEF). We examine the consequences of community composition across six structurally realistic plant community models. We find that a positive correlation between species' functioning in monoculture versus their dominance in mixture with regard to a specific function (the "function-dominance correlation") generates a positive relationship between realised diversity and ecosystem functioning across species richness treatments. However, because realised diversity declines when few species dominate, a positive function-dominance correlation generates a negative relationship between realised diversity and ecosystem functioning within species richness treatments. Removing seed inflow strengthens the link between the function-dominance correlation and BEF relationships across species richness treatments but weakens it within them. These results suggest that changes in species' identities in a local species pool may more strongly affect ecosystem functioning than changes in species richness

Ecosystem consequences of invertebrate decline

Human activities cause substantial changes in biodiversity.1,2 Despite ongoing concern about the implications of invertebrate decline,3,4,5,6,7 few empirical studies have examined the ecosystem consequences of invertebrate biomass loss. Here, we test the responses of six ecosystem services informed by 30 above- and belowground ecosystem variables to three levels of aboveground (i.e., vegetation associated) invertebrate community biomass (100%, 36%, and 0% of ambient biomass) in experimental grassland mesocosms in a controlled Ecotron facility. In line with recent reports on invertebrate biomass loss over the last decade, our 36% biomass treatment also represented a decrease in invertebrate abundance (−70%) and richness (−44%). Moreover, we simulated the pronounced change in invertebrate biomass and turnover in community composition across the season. We found that the loss of invertebrate biomass decreases ecosystem multifunctionality, including two critical ecosystem services, aboveground pest control and belowground decomposition, while harvested plant biomass increases, likely because less energy was channeled up the food chain. Moreover, communities and ecosystem functions become decoupled with a lower biomass of invertebrates. Our study shows that invertebrate loss threatens the integrity of grasslands by decoupling ecosystem processes and decreasing ecosystem-service supply

Global mismatches in aboveground and belowground biodiversity

Human activities are accelerating global biodiversity change and have resulted in severely threatened ecosystem services. A large proportion of terrestrial biodiversity is harbored by soil, but soil biodiversity has been omitted from many global biodiversity assessments and conservation actions, and understanding of global patterns of soil biodiversity remains limited. In particular, the extent to which hotspots and coldspots of aboveground and soil biodiversity overlap is not clear. We examined global patterns of these overlaps by mapping indices of aboveground (mammals, birds, amphibians, vascular plants) and soil (bacteria, fungi, macrofauna) biodiversity that we created using previously published data on species richness. Areas of mismatch between aboveground and soil biodiversity covered 27% of Earth's terrestrial surface. The temperate broadleaf and mixed forests biome had the highest proportion of grid cells with high aboveground biodiversity but low soil biodiversity, whereas the boreal and tundra biomes had intermediate soil biodiversity but low aboveground biodiversity. While more data on soil biodiversity are needed, both to cover geographic gaps and to include additional taxa, our results suggest that protecting aboveground biodiversity may not sufficiently reduce threats to soil biodiversity. Given the functional importance of soil biodiversity and the role of soils in human well-being, soil biodiversity should be considered further in policy agendas and conservation actions by adapting management practices to sustain soil biodiversity and considering soil biodiversity when designing protected areas.Peer reviewe

The geography of biodiversity change in marine and terrestrial assemblages

This work was supported by funding to the sChange working group through sDiv, the synthesis center of iDiv, the German Centre for Integrative Biodiversity Research Halle-Jena-Leipzig, funded by the German Research Foundation (FZT 118). S.A.B., H.B., J.M.C., J.H., and M.W. were supported by the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig. S.R.S. was supported by U.S. National Science Foundation grant 1400911. LHA was supported by Fundação para a Ciência e Tecnologia, Portugal (POPH/FSE SFRH/BD/90469/2012), and by the Jane and Aatos Erkko Foundation. M.D. was supported by a Leverhulme Trust Fellowship. A.E.M., F.M., and M.D. were supported by ERC AdG BioTIME 250189 and PoC BioCHANGE 727440. A.G. is supported by the Liber Ero Chair in Biodiversity Conservation.Human activities are fundamentally altering biodiversity. Projections of declines at the global scale are contrasted by highly variable trends at local scales, suggesting that biodiversity change may be spatially structured. Here, we examined spatial variation in species richness and composition change using more than 50,000 biodiversity time series from 239 studies and found clear geographic variation in biodiversity change. Rapid compositional change is prevalent, with marine biomes exceeding and terrestrial biomes trailing the overall trend. Assemblage richness is not changing on average, although locations exhibiting increasing and decreasing trends of up to about 20% per year were found in some marine studies. At local scales, widespread compositional reorganization is most often decoupled from richness change, and biodiversity change is strongest and most variable in the oceans.PostprintPostprintPeer reviewe