VARIABILITY OF WATER-QUALITY IN A SPRUCE STAND

The spatial variation of the chemical composition of soil water under a 75 year old spruce stand on a stagni-orthic Acrisol was investigated . Soil water was sampled with 72 suction probes from depths of 0.2 m a nd 0.7 m. Sampling points formed a grid of 9 x 8 nodes with an average spacing of 5 m. Sodium, potassium, magnesium and calcium concentratio ns and pH were measured on 12 dates. The statistical distribution of t he properties were mainly lognormal. Coefficients of variation mostly ranged between 20 % and 60 %. Trees had a clear influence on sample vo lumes and element concentrations. The latter increased generally in th e neighbourhood of the stem. The coefficient of variation of the prope rties was not constant through time. Maximum coefficients occurred at the beginning of the period of vegetation growth.