|Manderscheid, B; Matzner, E: Spatial Heterogeneity of Soil Solution Chemistry in a mature Norway Spruce (Picea abies (L.) Karst.) Stand, Water, Air and Soil Pollution, 85, 1185-1190 (1995)|
The determination of the average soil solution concentrations in forest soils is hindered by the spatial heterogeneity of the soil conditions ,and the stand structure on all scales. The aim of this paper is to investigate the spatial heterogeneity of the soil solution chemistry within a mature stand of Norway spruce and to evaluate the implication of this heterogeneity for the sampling design for soil solutions. The site is a 140 years old Norway spruce stand of 2.5 ha located in the German Fichtelgebirge at 800 m elevation on granitic, deeply weathered bedrock. At 35 cm soil depth, 59 ceramic suction lysimeters (5 cm length, 2 cm diameter) were installed in a systematic grid of 25 9 25 m and soil solution was sampled at 3 dates in June and July 1994. The solutions were analysed for major cations and anions. Semi-variance of the concentrations at a given date revealed no systematic spatial patterns. The coefficients of variance of the element concentrations were between 36 and 298% with highest values for NH4+-N. The implications of the observed heterogeneity for the apprupriate number of replicates was investigated by Monte Carlo simulations. As an example, the probability that the measured average concentration of SO42-S is outside a +10% range (related to the ~txue' 59 lysimeter average) is about 68% if only 3 replicates would have been used, 41% with 10 replicates and 25% with 20 replicates. Due to the generally large spatial heterogeneity of the soil solution chemistry in forest soils the number oflysimeters used must be carefully adjusted to site conditions and the specific question.