Consequences of riparian forest invasions by alien plants for litter decomposition in small streams and ponds
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Riparian forests play a crucial role in aquatic ecosystems by regulating light, temperature, channel stability and nutrient cycling. However, these forests are highly vulnerable to invasion by alien plant species, which can alter leaf litter inputs and decomposition dynamics, thereby impacting freshwater ecosystem functions. This study explores the decomposition rates of native black alder (Alnus glutinosa) and two riparian invaders, Japanese knotweed (Fallopia japonica) and Canada goldenrod (Solidago canadensis), in both headwater streams and pond mesocosms in Central Europe. We conducted experiments with 169 litter bags to assess decomposition rates and test the home-field advantage hypothesis. The hypothesis assumes that native litter decomposes faster due to the evolutionary adaptation of local decomposer communities. We found that invasive S. canadensis decomposed significantly faster than native A. glutinosa in both lotic and lentic environments. On the other hand, invasive F. japonica decomposed at a comparable rate (streams) or at a slower rate (ponds) than the native species. These findings contradict the home-field advantage hypothesis, suggesting that decomposition rates are primarily driven by litter nutrient content rather than geographic origin. The rapid breakdown of S. canadensis is likely driven by the low C:P ratio of its litter. The rapid decomposition of this litter may lead to short-term nutrient boosts that are quickly lost due to microbial activity, whereas the slow decomposition of F. japonica may limit immediate nutrient availability but extend their accessibility over longer periods. Overall, the invasion of riparian zones by species with litter traits distinct from those of native species can disrupt ecosystem processes, leading to cascading effects on aquatic food webs and nutrient cycling. Understanding the effects of riparian forest invasions on organic matter processing is essential for managing biodiversity and maintaining ecosystem integrity in freshwater environments.
Edited by
Diego Fontaneto, CNR-IRSA Water Research Institute, Verbania-Pallanza, ItalySupporting Agencies
Slovak Research and Development Agency, European Regional Development FundcE3c - Centre for Ecology, Evolution and Environmental Changes; CHANGE – Global Change and Sustainability Institute, Faculty of Sciences, University of Lisbon, Portugal
Faculty of Forestry and Wood Sciences, University of Life Sciences Prague, Praha-Suchdol, Czech Republic.
Institute of Botany, Plant Science and Biodiversity Center, Slovak Academy of Sciences, Bratislava, Slovakia
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