Preconditioning effects of intermittent stream flow on leaf litter decomposition |
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| Authors: | D Dieter D von Schiller E M García-Roger M M Sánchez-Montoya R Gómez J Mora-Gómez F Sangiorgio J Gelbrecht K Tockner |
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| Institution: | 1.Department of Biology, Chemistry, and Pharmacy,Free University of Berlin,Berlin,Germany;2.Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB),Berlin,Germany;3.Department of Ecology,University of Barcelona,Barcelona,Spain;4.Department of Ecology and Hydrology,University of Murcia,Murcia,Spain;5.Department of Environmental Sciences,University of Girona,Girona,Spain;6.Department of Biological and Environmental Sciences and Technologies,University of Salento,Lecce,Italy |
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| Abstract: | Autumnal input of leaf litter is a pivotal energy source in most headwater streams. In temporary streams, however, water stress
may lead to a seasonal shift in leaf abscission. Leaves accumulate at the surface of the dry streambed or in residual pools
and are subject to physicochemical preconditioning before decomposition starts after flow recovery. In this study, we experimentally
tested the effect of photodegradation on sunlit streambeds and anaerobic fermentation in anoxic pools on leaf decomposition
during the subsequent flowing phase. To mimic field preconditioning, we exposed Populus tremula leaves to UV–VIS irradiation and wet-anoxic conditions in the laboratory. Subsequently, we quantified leaf mass loss of preconditioned
leaves and the associated decomposer community in five low-order temporary streams using coarse and fine mesh litter bags.
On average, mass loss after approximately 45 days was 4 and 7% lower when leaves were preconditioned by irradiation and anoxic
conditions, respectively. We found a lower chemical quality and lower ergosterol content (a proxy for living fungal biomass)
in leaves from the anoxic preconditioning, but no effects on macroinvertebrate assemblages were detected for any preconditioning
treatment. Overall, results from this study suggest a reduced processing efficiency of organic matter in temporary streams
due to preconditioning during intermittence of flow leading to reduced substrate quality and repressed decomposer activity.
These preconditioning effects may become more relevant in the future given the expected worldwide increase in the geographical
extent of intermittent flow as a consequence of global change. |
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