Vortrag, HydroEco2006 (International Multidisciplinary Conference on Hydrology and Ecology: The Groundwater/Ecology Connection): 11.09.2006 - 14.09.2006
The relative constancy of hydrophysical and hydrochemical parameters in springs sets them apart from other lotic systems. Species composition in natural spring habitats is influenced by spatial (habitat size, distance between springs), hydrophysical (temperature, discharge) and hydrochemical conditions (nutrients, acidity). Many Central European forested catchments, especially on siliceous bedrock, have been strongly influenced by atmospheric depositions, which is reflected by the acidification of ground and surface waters. These changes in water quality particularly affect the stenoecious crenobiontic and crenophilic species. Through a regional survey based on 262 forest springs in five mountain landscapes across Central Europe (Thüringer Wald, Thüringer Schiefergebirge, Frankenwald, Fichtelgebirge, Erzgebirge) we monitored higher plants, mosses and liverworts to identify the driving forces of species composition. The temporal dynamics of springwater quality and associated vegetation were investigated by means of repeated measurements in 102 springs from 1989 to 2005. Hydrochemical conditions are found to be more important than physical or spatial factors. Low pH-values accompanied by high concentrations of Al, Cd, Zn and Mn are the main factor that is related to species composition. By means of multivariate ordination techniques Chrysosplenium oppositifolium and Cardamine amara are identified as indicator species for non-acidic water chemistry, whereas the mosses Spagnum fallax and Polytrichum commune are found to be dominant under acidic conditions. Surprisingly, changes in dominance of these selected indicator species can not be directly linked to trends in acidification. While we found a slight trend of recovery from acidification in springwater from 1989 to 2005, the indicator species did not reflect that change. This could be caused by a delayed reaction due to persistent dominance patterns (inertia). In contrast the response of the whole plant community shows first signs of recovery, which suggests a need for supplementary indicator species in the dynamic application of the monitoring system. Spring vegetation proves to be a good indicator system to characterize groundwater chemistry, which in turn reflects the geochemical and hydrological conditions of forested catchments. Spatial patterns of spring vegetation emerge at various spatial scales and can provide valuable ecological information for hydrologists and foresters. However, the response time of vegetation to shifts in springwater chemistry still has to be examined.