Abschlußbericht zum Forschungsprojekt ST121 - Technische ...

XII
Abstract
all examined trees, independent of the soil properties of the planting site. Moreover, the
overall root lengths (diameters >5 mm) on the up-slope side of the trees were shorter than
those of roots orientated to the down-slope side. In the long-run, this could endanger the
stability of afforested redevelopment areas against snow movement.
Both the seedlings on Ah horizons and the planted as well as the naturally regenerated spruces
on “Mull”-rendzinas showed limited biomass development (for the seedlings) and/or needle
weights and therefore a low overall vitality. Despite concentration effects in the small needles,
the spruces on “Mull”-rendzinas showed heavy nutrient deficiencies especially for N, P, Mn,
and rarely for K. On account of the low total needle masses, their internal nutrient stores were
small and correspondingly the shoot increments were low. Higher N-concentrations and more
easily decomposable N-forms in the organic layers would lead to an enhanced N-availability.
In addition, organic layers were characterised by higher contents of extractable P and K than
the mineral soils. Due to acid pH-values and a decreasing (Ca+Mg)/K ratio and therefore a
decreasing ion-antagonism for K, P- and K-availability was higher in organic layers. In
addition, the Mn-availability increased in organic layers. Thus, seedlings and naturally
regenerated plants on thick, acid organic layers showed a higher vitality and possessed a
higher total biomass (seedlings) and needle mass than spruces on “Mull”-rendzinas.
Moreover, their larger needles indicated a less pronounced deficiency of N, P, and rarely of K
and of Mn and their shoot increments were higher on account of the ability to translocate
nutrients from the higher nutrient pool in the parenchyma. In addition, highly decayed
deadwood was very favourable with regard to the nutrition and the biomass development of
the seedlings. Manuring measures resulted only in a short-term increase of needle nutrient
concentrations and growth rates. Moreover, the manuring effects were more marked on vital
trees growing on “Moder” sites.
The abundance of ectomycorrhizae (ECM) was highest in the organic soil layers of “Moder”rendzinas
compared to the mineral soil horizons. The ordination of the ECM communities and
of the exploration types revealed segregation in dependency on differences in soil horizon
properties. While Cenococcum geophilum preferred the organic soil layers, Lactarius spp.,
Tomentella spp., and Craterellus tubaeformis were generally most abundant in the mineral
soil horizons. C. geophilum was the predominant species, possibly due to enhanced
competitiveness under the prevailing site conditions. The short-distance exploration types
preferentially colonised the organic soil layer, whereas the contact types together with
medium-distance types were primarily associated with the underlying A-horizons. The spatial
niche differentiation of ECM genera and exploration types was probably caused by the soil