Community patterns and ecosystem processes in forested headwater streams along a gradient of riparian canopy openness
Majdi, Nabil; Boiché, Anatole; Traunspurger, Walter; Lecerf, Antoine
published: Sep 1, 2015
ArtNo. ESP141018701008, Price: 29.00 €
Riparian forest canopy influences stream communities and ecosystem functions primarily through providing shade and organic matter to streams. We examined effects of forest canopy cover on autotrophic and heterotrophic processes and on benthic communities of ten forested headwater streams forming a subtle gradient of canopy openness (0–25 %). We measured periphyton standing crop and litter breakdown rate, and determined decomposer biomass and community patterns of invertebrates. There was a sharp increase in periphyton biomass and the contribution of diatoms along the gradient of canopy openness. Canopy openness explained well cross-stream variations in the breakdown rates of beech leaves and wood and in fungal biomass in litter whereas it did not predict shredder density. Canopy effect on litter breakdown rates may thus have been mediated by fungi through stimulation of microbial breakdown by temperature and/or synergistic interaction with algae. Overall the litter-associated invertebrate community was not found to be strongly linked to site canopy openness. Meiofauna colonization of litter packs appeared to be largely determined by the availability of interstitial habitat (sediment) in litter packs. In addition, high dissolved organic carbon concentration in streamwater was associated with high densities of bacterial-feeding nematodes. Our results stress that even subtle changes in riparian canopy openness can affect substantially stream ecosystem functioning through effects on autotrophic (periphyton) and heterotrophic microbes (fungi).