Das Entsauerungs- und Austrocknungsexperiment im Solling : Bodenlösungschemie und Stoffhaushalt

1999

S. 55-57

12 Lit. Ang.

Unselbständiges Werk

200060452

Throughfall in a 65-year-old Norway spruce forest at Solling was chemically treated since 1991 to monitor responses of an acidiefied soil to reduced acidic deposition by using a transparent roof construction below the canopy. The manipulated throughfall, so-called "pre-industrial clean rain", was created by reducing the ambient loads of proton, sulfate and nitrate by 85%, 50% and 50%, respectively, and was distributed onto the forest floor. Soil solution chemistry showed a quick response to the reduced input, whereas the input-output budget did not indicate de-acidification in the subsoil. Prolonged summer droughts were simulated under another roofed plot in the same forest in the summers 1991-1994. It was hypothesized that during rewettings of dried soils acidification pulses can occur due to a possible accumulation of HNO3 in drought periods. However, such pulses were not evidenced in our experiment. On the contrary, nitrate concentrations in the soil solution generally decreased over the drought experiment period. In addition, soil CO2 emission rates at the drought treatment were measured throughout 1993 and 1994. The results suggested that soil droughts reduce the CO2 emission, and that soil temperature is a crucial factor influencing the emission rate during rewettings.