assessment of changes in the phosphorus status of forest ...

19.84
n=144
NVHU< 1228
|
CMENGE< 38.15 CMENGE< 177.6
48.43
n=234
78.87
n=110
NVHU< 1761
Fig 6: Spruce : Regression tree for the dependent variable P in the humus layer
against all site and stand parameters available in the BZE-I data set (n
= 587). Here only the influence of significant factors, N and C in the
humus layer are depicted, which explain 55% of the variation in humus
P, are depicted.
The same type of regression tree analysis was carried out for a number of variables.
The number of variables (with continuous values) available for testing are given
below (no variable with discrete values was included in the regression tree, variable
with continuous values were included in the analysis). The variables included were:
concentration of elements in the foliage (N, P, K, Ca, Mg, Mn, S) and the ratio of P
concentrations in 1-yr and 3-yr needles of spruce. For the litter layer, only values of
element stores for C, N, P, K, Ca, Mg, Mn were available, for 0-10cm soil depth
values for pH, base saturation and amount of acid cations on the exchange complex
were available. For 0-30cm soil depth, stores of elements for Corg, N, P, K, Ca, Mg,
111.6
n=66
182.5
n=28
35