Auswirkungen von saurer Beregnung und Kalkung in einem Fichtenbestand (Höglwaldprojekt) : 1. Statusseminar PBWU

1989

S. 145-154

11 Lit. Ang.

Unselbständiges Werk

200060657

An acid irrigation and liming experiment in an around 80 years old Norway spruce stand (Picea abies L. Karst.) on acid hapludult (pH (H2O) 4.2, Ca/Al 0.3 at 20 cm depth) in Southern Bavaria was started in 1982. Up to now acid irrigation with 2.7 to 2.8 (mean annual input around 4 kmol H+ ha-Ü) caused only a pH decrease of 0.3 to 0.5 pH units, confined to the upper part of the organic surface layer. Almost the entire H+ addition was buffered. The main buffering reactions were cation exchange in the upper part of organic layer, and dissolution of aluminiumhydroxides mainly in the upper part of the mineral soil, which were contributing to the buffering to around 15 resp. 80% of the H+ addition. The cation exchange was connected with a strong reduction of the cation exchange capacity due to protonation of organic functional groups. Also leaching of the released cations Ca, Mg, Mn, K occurred. In the mineral soil the Al concentration increased but no change in Ca/Al and Mg/Al ratios because of leaching input from the organic layer above. Up to now the stand shows no severe damage symptoms in contrast to the ground flora and microorganisms. The absence of tree damages may be due to the fact, that the trees have access to horizons with better nutrient supply. That enables them to develop defensive mechanisms in the "Al stress" horizons as pH increase on the rhizoplan and Al complexation in the mucilage. Mobilization of heavy metals, due to acidic treatment, was observed. Only Mn effect on Oxalis is suggested. Liming caused strong increase of nitrification and nitrate leaching before the background of an ecxess N supply mainly due atmospheric N input. Al, Pb and Cu were also mobilized by liming due to a hydrolysis-induced increase of soluble organic C, forming complexes with these metals.