EVIDENCE FOR A NUTRITIONAL DISORDER OF OXALIS-ACETOSELLA L. ON ACID FOREST SOILS - I - CONTROL SITUATION AND EFFECTS OF DOLOMITIC LIMING AND ACID IRRIGATION

This paper reports on the mean cover, biometric and vitality parameter s and mineral nutrient status of wood-sorrel (Oxalis acetosella L.) on the control and experimental plots of a mature Norway spruce stand on acid soil (Hoglwald Experiment). On the control plot Oxalis showed re latively poor leaf growth and chloroses on young and older leaf blades . Mineral analyses in the Hoglwald and comparative studies on other fo rest sites indicated a very good to good supply of N and P, a moderate Ca nutrition and very high Mn concentrations of the leaves. The input of dolomitic lime led to a drastic propagation and vitalization of th e wood-sorrel. The long-lasting effect of treatment was independent of pH dynamics in the root zone. The leaf chloroses of Oxalis disappeare d completely after that treatment. The level of Ca and Mg supply clear ly improved, whereas the concentrations of P, N, Mn and Zn diminished. Surprisingly, the K nutrition also improved after liming. Oxalis reac ted to acid irrigation (sulfuric acid; pH 2.7-2.8) in comparison to no rmal watering (pH 5.0-5.5) with a continuous decrease in cover, but wi thout visible leaf necroses. The concentrations of total sulphur, SO4- S and S-org were raised, while the concentrations of Ca, Mn and Zn of the leaf blades decreased. After termination of acid input a recovery of nutrition occurred and a slow recolonization began. Preceding lime application prevented the growth-inhibiting effect of the acid irrigat ion. The study leads to the working hypothesis, that Ca nutrition may be the controlling factor for leaf growth and vegetative propagation o f Oxalis in the Hoglwald Experiment.