Warming, and the presence of a dominant shredder, drive variation in decomposer communities in a mountain stream
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We assessed the effects of rising temperature and presence of a dominant detritivore (Allogamus laureatus; Trichoptera, Limnephilidae) on the decomposition of submerged oak litter (Quercus robur L.) and associated detritivore and fungal communities in a mountain stream in central Portugal. It was divided longitudinally, with one half maintained at ambient temperature (mean = 12.4 °C) while the other was warmed ~3 °C above ambient temperature. Oak leaves in litter bags were incubated in both stream halves, with half of the bags containing one A. laureatus larva. Replicate bags were collected over 6 weeks to determine litter mass remaining and the detritivore and fungal communities. A. laureatus stimulated decomposition of oak litter and colonization by other shredders at ambient temperature. It also increased fungal biomass at increased temperature, and changed the community of fungi. Higher temperature inhibited A. laureatus activity, resulting in a substantial change in the strength of interactions within both fungal and detritivore assemblages, with important consequences for leaf litter decomposition.
KeywordsAquatic communities Climate change Ecosystem functioning Allogamus laureatus Species interactions
We thank Cristina Docal for the ion chromatography analyses, and Ana Lírio and João Rosa for valuable help in the field. We also thank the Company Amado and Amado Lda., Coimbra, Portugal, for the help in the construction of the heating tanks and setup of the system in the stream and the Municipality of Lousã, Portugal, for their support and help in the setup of the hydraulic infrastructures and warming facilities. We gratefully acknowledge Prof. Brian Moss and two anonymous reviewers for their comments and suggestions on an earlier version of the manuscript. This study was supported by the European Regional Development Fund (ERDF) through the COMPETE––Operational Factors of Competitiveness Program (POFC-COMPETE) and national funds through FCT––Foundation for Science and Technology, under the project “Predicting the effect of global warming on stream ecosystems” (FCT Ref: PTDC/CLI/67180/2006; COMPETE Ref: FCOMP-01-0124-FEDER-007112). Financial support granted by the FCT to VF (references SFRH/BPD/34368/2006 and SFRH/BPD/76482/2011, program POPH/FSE) is gratefully acknowledged.
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