Beschreibung

• The project deals with coarse woody debris, decay processes in alpine forest soils, soil organisms, humus forms and their relation to climate in an Alpine area (Trentino, climosequences from 1000 m to about 2200 m asl, N- and S- facing slopes, natural coniferous forest). Planned activities are grouped among 3 different “compartments”: Coarse woody debris (CWD) → Humus forms → Soil organic matter (SOM). We have the following research questions: (i) How does climate affect coarse woody decay above and especially in the soil of alpine sites? (ii) What time scales are involved in (CWD decay as a function of climate)? How quickly is CWD integrated into SOM fractions? In which way are the decay products of CWD stabilised? (iii) What are the links between decay mechanisms and the spatial distribution of humus forms? (iv) Can the humus form serve as a proxy for the soil biota for the spatial extrapolation.

Projektlaufzeit

• 01.06.2012 - 31.12.2016

Verbund/Partnerorganisation

• Fonds zur Förderung der wissenschaftlichen Forschung (FWF) - Österreich

Ergebniszusammenfassung

• In mountain ecosystems, elevation, slope exposure, and a highly heterogeneous relief cause a high spatial variability of microclimate, soil moisture regimes, and patterns of erosion and accumulation. As a consequence, distribution patterns of humus forms as well as of soil organisms show a high spatial variability. Spatial information on humus forms is scarce especially in mountain areas, and studies on soil biodiversity are usually limited to the local scale. Within the D.A.CH. project “Effect of climate on coarse woody debris decay dynamics and incorporation into the soils of forested Alpine areas (DecAlp)” we studied natural subalpine coniferous forest ecosystems in two alpine valleys (Val di Sole, Val di Rabbi) in Trentino, Italian Alps, between ca. 1200 and 1800 m a.s.l. The aim of our Working Group “Modelling” was I. to predict the spatial distribution of humus forms as a function of environmental characteristics and II. to use humus forms as proxy for soil biota (specifically enchytraeids and microorganisms) for spatial extrapolation. Our first goal was to establish a suitable technique for the spatial modelling of humus forms. We achieved this by using a combination of classification and regression trees (CART) and fuzzy membership functions. Based on topographic data, we created prediction maps of humus form patterns depending on elevation and exposure. Moreover, we assessed the quality of various vegetation parameters as bioindicators of humus forms. Mean Landolt indicator values of the herb layer (especially the indicator value for soil reaction) displayed a close relationship with humus form properties. Furthermore, we addressed the influence of the spatial scale on humus form modelling. We considered the varying influences by elevation, microtopography and vegetation during the implementation of humus form models at the local, the slope, and the landscape scale, resulting in simulations and prediction maps of humus forms. Another part of the project dealt with humus forms as proxy of the soil biota distribution from the plot scale to the landscape scale. We modelled the spatial distribution of mull-indicating enchytraeids and of moder/mor-indicating enchytraeids and compared these prediction maps with those of humus forms. There was a strong link between the spatial distribution of humus forms and the occurrence of certain groups of enchytraeid species, which is consistent across the major part of our study area. Thus, we have shown that humus forms can be used as a proxy of the decomposer community in our study area. Humus form models and derived models of the decomposer community have great potential as tool to detect environmental conditions in mountain ecosystems and their changes, e. g. with respect to soil quality, carbon stocks, and growing conditions for plants.