Shifts in the diversity and composition of consumer traits limit the effects of land use on stream ecosystem functioning
(English)Manuscript (preprint) (Other academic)
Abiotic disturbances that directly affect ecosystem functioning may also affect the distribution and composition of functional traits within a community. Shifts in trait composition may further enhance or even limit those effects caused by the abiotic stressors. In this work we asked whether an agricultural landuse gradient would affect both invertebrate detritivore functional diversity and leaf litter decomposition in streams. We further asked how the landuse effect on functional traits would relate to ecosystem functioning, and if their relationship would change across seasons. Using Structural Equation Modelling, which allows the partitioning of both direct and indirect relationships, we show that in the autumn land use had a positive effect on functioning, but this relationship was counteracted by a negative indirect effect on leaf decomposition. Landuse positively affected the presence of detritivore traits that were negatively related to functioning and also promoted trait dominance, which was negatively related to functioning. These results contrast with direct linear regressions between disturbance and functioning, which did not yield any relationship between the two variables. In spring, landuse had no effect on functioning, which is explained by the reduced impact of agricultural disturbances in our boreal streams. Our results emphasise the key role played by trait identity and diversity in mediating the effects of human disturbance on ecosystem functioning. Furthermore, our findings highlight the value of distinguishing the direct effects of human disturbances on ecosystem processes from those mediated through changes in the structure of trophic webs.
response and effect trait, functional diversity, biodiversity, leaf litter decomposition
IdentifiersURN: urn:nbn:se:umu:diva-82910OAI: oai:DiVA.org:umu-82910DiVA: diva2:663890