Organic matter accumulation following Pinus mugo Turra establishment in subalpine pastures

Abstract

Background: Livestock reduction or abandonment has been common on the subalpine pastures of the Northern Calcareous Alps in Austria and Germany since the mid-nineteenth century. The mosaic of Pinus mugo scrub and grassland is being increasingly recolonised by P. mugo. Aims: In this study we focus on the accumulation rate of the organic layer associated with establishment and development of Pinus mugo in non-forest plant communities. Methods: Age determination of P. mugo is used in combination with soil and existing climatic data to describe the site-dependent accumulation rates of the organic layer by using generalised linear models. Results: Mean increase of the organic layer is 12.5cm during the first 100 years. Decomposition of fresh litter is retarded in the first 30–50 years after P. mugo establishment. The residual variation of the age–depth relationship can be explained satisfactorily by using climate and habitat descriptors. Temperature, site water balance, and the presence of a clayey soil are significantly related to the depth of the organic layer. Conclusions: Organic layer accumulation after P. mugo establishment in former pastures is a long-term process exceeding the investigated period of 100–150 years. Increased needle litter input as the prime factor, together with soil properties and particular microclimatic conditions under the P. mugo canopy all contribute to controlling accumulation rates.