Líffræðifélag Íslands
Líffræðiráðstefnan 2015
Erindi/veggspjald / Talk/poster V3
Helena M. Stefansdottir (1), Bjarni D. Sigurdsson (1), Edda S. Oddsdottir (2), Brynhildur Bjarnadottir(3) Gintare Medelyte (4) and Jon S. Olafsson (4)
1. Agricultural University of Iceland, Keldnaholti, 112 Reykjavik, Iceland, 2. Icelandic Forest Research, Mogilsa, 116 Reykjavik, Iceland, 3. University of Akureyri, 600 Akureyri, Iceland, 4. Institute of Freshwater Fisheries, Keldnaholti, 112 Reykjavik, Iceland.
Kynnir / Presenter: Helena M. Stefansdottir
Tengiliður / Corresponding author: Helena M. Stefansdottir (helenamarta@gmail.com)
Large-scale deforestation, loss of vegetation cover and subsequent soil erosion has been an ongoing problem in Iceland through centuries. Loss of vegetation and soil does not only affect the function of the terrestrial ecosystems, but can potentially also affect other linked ecosystems, such as freshwater streams in the same area (catchments). The present study was conducted on eight first order headwater streams and their catchments in southern Iceland, where four catchments had been eroded and four had remnant woodland vegetation and soils. Measurements of standing biomass and litter stocks were made and annual terrestrial litter production and litter transport into streams were done. Coarse- and fine-mesh litter bags with leaf litter were put into the streams to measure the decomposition rate and to evaluate the relative impact of aquatic invertebrates on the decomposition rate and the decomposer community structure. Finally the whole benthic invertebrate community in the different streams was evaluated by taking Surber samples. Calculated spatial mean annual aboveground litter production was 13.7 times higher for the remnant woodland catchments than the eroded catchments, but the litter transport into streams was only 2.8 times higher there. This indicated much stronger lateral transport of litter in the more wind exposed eroded catchments. The stream litter decomposition rate was not significantly different between the two catchment types, when only bacteria and fungi were allowed to take part in the decomposition process (fine-mesh litter bags). However, when the invertebrate fauna was also free to access the litter (coarse-mesh litter bags) the decomposition rate was 94% higher in the woodland streams. The overall invertebrate population density, number of species, Shannon-Wiener Index and Index of Similarity did not significantly differ between the two catchment types, neither for the decomposer communities inside the coarse-mesh litterbags nor in the whole benthic invertebrate community. However, in the remnant woodland streams the density of shredders was significantly higher in the coarse-mesh litter bags, partly explaining why the decomposition rates were higher there.