Fig. 5
Dependency of (a) the intercept a, and (b) the slope b of the equation iv = a + bv on the growing-season Martonne index Mgs fitted by linear models (Eqs. 2a and 2b) for Norway spruce and European beech (see Table 6 for statistical fit results). Water availability, Mgs, mostly decreases the intercept and increases the slope of the annual and inter-individual iv-v relationship. This indicates an increase of size-asymmmetric competition with increasing water availability and a more equal growth distribution between the trees in a stand in dry periods. For this evaluation we pooled the trees of the monospecific and mixed species plots