The relationship between land-use, hydromorphology and river biota at different spatial and temporal scales: a synthesis of seven case studies

Abstract

The aim of this paper is to summarize seven case studies that were analysed as part of research theme the interaction between land-use and climate forming part of EU-funded Euro-limpacs project Evaluating impacts of global change on European freshwater ecosystems. Different aspects of relationships between climate change, land-use at different spatial scales, in-stream hydrology and morphology, and lotic biota were studied. The papers included analyses of: i) effects of historical changes in stream hydromorphology and biota, ii) influences at different spatial scales on physical features (hydrology and morphology), and iii) influences at different spatial scales on lotic biota. A multitude of environmental variables and gradients at different spatial scales affect in-stream physical as well as biological parameters. Disentangling which of these variables extort strongest influence on hydromorphology and lotic biota seems to differ among studies as can be seen from seven papers summarized here. The studies showed a general pattern with gradients from up-stream headwaters to down-stream stream reaches with predictable changes in vegetation and hydromorphological relationships along gradient. This is of course nothing new, but rather it was surprising how many different spatial scales and types of environmental variables were found to be important in structuring in-stream physical and biotic variables in different studies. Further investigations using standardised sets of environmental variables and possibly also standardised biotic sampling methods as well as clear definitions of which spatial scales are investigated are needed to further disentangle importance of land-use at different spatial scales on in-stream hydromorphology and biota. It is also clearly necessary to widen analysis methods from correlative to such methods that investigate mechanistic relationships among variables within a catchment.