BIOGEOCHEMISTRY OF A CIRQUE-LAKE LANDSCAPE - AN INTERDISCIPLINARY STUDY IN A CATCHMENT OF THE NORTHERN BLACK-FOREST, GERMANY

The pedological analysis of the soil continuum in a catchment can yiel d substantial insight in flow paths, transport processes, and possible linkages between terrestrial and aquatic ecosystems. In an interdisci plinary study we investigated precipitation, lake tributaries, and soi ls of three sandstone-dominated subcatchments of a dystrophic cirque l ake during 1989 and 1990. The chemistry of tributary 1 is characterize d by relatively higher pH values, positive alkalinity at base flow, hi gher concentrations of Ca, Mg, and K, and lower dissolved organic carb on (DOC). It does not fit to the chemistry of the very acid, leached, podzolized soils in its subcatchment (weak linkage). The dominance of base flow and lower intra-annual variations in discharge and temperatu re further confirm the conclusion of a dominating vertical flow path o f soil water into the regolith and bedrock zone with substantial buffe ring in that zone (groundwater flow). Tributary 2 shows the lowest pH values and the highest concentrations of DOC, Fe, Al, and P, which fit s very well the chemistry of the very acid, leached, permanently wet s oils of its catchment (strong linkage). The dominance of storm flow wa ter with high intra-annual variations in discharge corresponds with th e high soil moisture and prevalent lateral flow path of water in the s oil cover (lateral subsurface flow). Tributary ''mix'' behaves interme diate between tributaries 1 and 2 but is more similar to that of tribu tary 1. This is due to the dominance of podzolized over reductomorphic soils in the subcatchment. Lateral transport of matter can be inferre d from the soil pattern in all catchments, but its relevance for lake inlet chemistry depends on the existence of downslope immobilization z ones.