Controls on soil organic matter in Swiss forests

Impact of forest productivity, land-use history, climate and physico-chemical stabilization

Soil organic matter (SOM) plays a key role for many soil functions. Based on more than 1000 soil profiles of the WSL soil data base, we are quantifying soil organic carbon storage in Swiss forests. In a NRP 68 project (Soil as a resource), we are investigating to what extent climatic conditions, historical land use, forest management and physico-chemical soil properties determine carbon storage in Swiss forest soils.

Rationale

Soil organic matter (SOM) is a key component for a number of soil functions such as soil C and nutrient storage, retention of pollutants, soil biodiversity, and soil moisture. The composition of SOM is highly heterogeneous with compounds having turnover rates of days to millennia. Although we have a qualitative knowledge on the mechanisms determining SOM storage, they are not sufficiently reflected in SOM models.

Aims

The major aim of the NRP 68 project is to identify the drivers of SOM storage in forest soils of Switzerland. Our specific objectives are

to assess how forest productivity and tree species composition affect SOM storage
to investigate if and how land-use history affects C pools in soils
to estimate the influence of climate, temperature and precipitation, on SOM stocks
to link SOM stocks to physico-chemical parameters controlling SOM stabilization
to model SOM and to evaluate the residual to measured SOM stocks