|Lischeid, G; Alewell, C; Moritz, K; Bittersohl, J: Trends in the input-output relations: The catchment budgets in Matzner, E.: Ecological Studies, Biogeochemistry of forested catchments in a changing environment: a German case study, Springer Verlag, 172, 437-456 (2004), doi:10.1007/978-3-662-06073-5_24|
One important focus of biogeochemical ecosystem studies is that of identifying sinks and sources of various substances in the system. These might be either finite or transient sinks or sources. A quantification of element budgets within catchments is of crucial importance for the identification of critical ecosystem states such as nutrient loss, acidification and contamination of waters and deterioration of soils (Ulrich 1994). However, sinks might turn into sources and vice versa over time. Thus, long-term monitoring is important when interpreting element fluxes and budgets. The latter especially holds true because element budgets and fluxes are subject to high spatial and temporal variability, causing large errors in their estimation, as has been shown previously for the Lehstenbach catchment (Manderscheid and Matzner 1995; Manderscheid et al. 2000a; Alewell et al. 2004).