B. Manderscheid et E. Matzner, SPATIAL HETEROGENEITY OF SOIL SOLUTION CHEMISTRY IN A MATURE NORWAY SPRUCE (PICEA-ABIES (L) KARST) STAND, Water, air and soil pollution, 85(3), 1995, pp. 1185-1190
The determination of the average soil solution concentrations in fores
t soils is hindered by the spatial heterogeneity of the soil condition
s and the stand structure on all scales. The aim of this paper is to i
nvestigate the spatial heterogeneity of the soil solution chemistry wi
thin a mature stand of Norway spruce and to evaluate the implication o
f this heterogeneity for the sampling design for soil solutions. The s
ite is a 140 years old Norway spruce stand of 2.5 ha located in the Ge
rman Fichtelgebirge at 800 m elevation on granitic, deeply weathered b
edrock. At 35 cm soil depth 59 ceramic suction lysimeters (5 nm length
, 2 cm diameter) were installed in a systematic grid of 25 . 25 m and
soil solution was sampled at 3 dates in June and July 1994. The soluti
ons were analysed for major cations and anions. Semi-variance of the c
oncentrations at a given date: revealed no systematic spatial patterns
. The coefficients of variance of the element concentrations were betw
een 36 and 298% with highest values for NH4+-N. The implications of th
e observed heterogeneity for the appropriate number of replicates was
investigated by Monte Carlo simulations. As an example, the probabilit
y that the measured average concentration of SO42--S is outside a +/-1
0% range (related to the 'true' 59 lysimeter average) is about 68% if
only 3 replicates could 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 of lysimeter
s used must be carefully adjusted to site conditions and the specific
question.