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When does diversity matter?: Species functional diversity and ecosystem functioning across habitats and seasons in a field experiment
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
2014 (English)In: Journal of Animal Ecology, ISSN 0021-8790, E-ISSN 1365-2656, Vol. 83, no 2, 460-469 p.Article in journal (Refereed) Published
Abstract [en]

Despite ample experimental evidence indicating that biodiversity might be an important driver of ecosystem processes, its role in the functioning of real ecosystems remains unclear. In particular, the understanding of which aspects of biodiversity are most important for ecosystem functioning, their importance relative to other biotic and abiotic drivers, and the circumstances under which biodiversity is most likely to influence functioning in nature, is limited. We conducted a field study that focussed on a guild of insect detritivores in streams, in which we quantified variation in the process of leaf decomposition across two habitats (riffles and pools) and two seasons (autumn and spring). The study was conducted in six streams, and the same locations were sampled in the two seasons. With the aid of structural equations modelling, we assessed spatiotemporal variation in the roles of three key biotic drivers in this process: functional diversity, quantified based on a spe- cies trait matrix, consumer density and biomass. Our models also accounted for variability related to different litter resources, and other sources of biotic and abiotic variability among streams. All three of our focal biotic drivers influenced leaf decomposition, but none was important in all habitats and seasons. Functional diversity had contrasting effects on decomposition between habitats and seasons. A positive relationship was observed in pool habitats in spring, associated with high trait dispersion, whereas a negative relationship was observed in riffle habitats during autumn. Our results demonstrate that functional biodiversity can be as significant for functioning in natural ecosystems as other important biotic drivers. In particular, variation in the role of functional diversity between seasons highlights the importance of fluctuations in the relative abundances of traits for ecosystem process rates in real ecosystems.

Place, publisher, year, edition, pages
John Wiley & Sons, 2014. Vol. 83, no 2, 460-469 p.
Keyword [en]
stream ecosystems, litter decomposition, species evenness, species traits, spatial-temporal variability, path analyses
National Category
Ecology
Identifiers
URN: urn:nbn:se:umu:diva-82868DOI: 10.1111/1365-2656.12142ISI: 000331469200015OAI: oai:DiVA.org:umu-82868DiVA: diva2:663622
Funder
Swedish Research Council, 621-2006-375
Available from: 2013-11-12 Created: 2013-11-12 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Ecosystem functioning in streams: Disentangling the roles of biodiversity, stoichiometry, and anthropogenic drivers
Open this publication in new window or tab >>Ecosystem functioning in streams: Disentangling the roles of biodiversity, stoichiometry, and anthropogenic drivers
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

What will happen to ecosystems if species continue to go extinct at the high rates seen today? Although ecosystems are often threatened by a myriad of physical or chemical stressors, recent evidence has suggested that the loss of species may have impacts on the functions and services of ecosystems that equal or exceed other major environmental disturbances. The underlying causes that link species diversity to ecosystem functioning include species niche complementarity, facilitative interactions, or selection effects, which cause process rates to be enhanced in more diverse communities. Interference competition, antagonistic interactions, or negative selection effects may otherwise reduce the efficiency or resource processing in diverse communities. While several of these mechanisms have been investigated in controlled experiments, there is an urgent need to understand how species diversity affects ecosystem functioning in nature, where variability of both biotic and abiotic factors is usually high. Species functional traits provide an important conceptual link between the effects of disturbances on community composition and diversity, and their ultimate outcomes for ecosystem functioning. Within this framework, I investigated relationships between the decomposition of leaf litter, a fundamental ecosystem process in stream ecosystems, and the composition and diversity of functional traits within the detritivore feeding guild. These include traits related to species habitat and resource preferences, phenology, and size. I focused on disentangling the biotic and abiotic drivers, including functional diversity, regulating ecosystem functioning in streams in a series of field experiments that captured real-world environmental gradients. Leaf decomposition rates were assessed using litter-bags of 0.5 and 10 mm opening size which allow the quantification of microbial and invertebrate + microbial contributions, respectively, to litter decomposition. I also used PVC chambers where leaf litter and a fixed number of invertebrate detritivores were enclosed in the field for a set time-period. The chemical characterisation of stream detritivores and leaf litter, by means of their nitrogen, phosphorus, and carbon concentration, was used to investigate how stoichiometric imbalance between detritivores and leaf litter may affect consumer growth and resource consumption. I found that the diversity and composition of functional traits within the stream detritivore feeding guild sometimes had effects on ecosystem functioning as strong as those of other major biotic factors (e.g. detritivore density and biomass), and abiotic factors (e.g. habitat complexity and agricultural stressors). However, the occurrence of diversity-functioning relationships was patchy in space and time, highlighting ongoing challenges in predicting the role of diversity a priori. The stoichiometric imbalance between consumers and resource was also identified as an important driver of functioning, affecting consumer growth rates, but not leaf decomposition rates. Overall, these results shed light on the understanding of species functional diversity effect on ecosystems, and indicate that the shifts in the functional diversity and composition of consumer guilds can have important outcomes for the functioning of stream ecosystems.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2013. 44 p.
Keyword
detrital food web, functional diversity, stoichiometry, nitrogen and phosphorus concentrations, recalcitrant carbon, spatial and temporal species distribution, pools and riffles, isotopes, leaf decomposition rates, land use, restoration, habitat complexity
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-82914 (URN)978-91-7459-758-5 (ISBN)
Public defence
2013-12-06, BiA401 i Biologihuset, Umeå universitet, Umeå, 09:30 (English)
Opponent
Supervisors
Funder
Swedish Research Council, 621-2006-375
Available from: 2013-11-15 Created: 2013-11-13 Last updated: 2013-11-19Bibliographically approved

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Publisher's full texthttp://doi.wiley.com/10.1111/1365-2656.12142

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Frainer, AndréMalmqvist, Björn

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