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Litter decomposition in mixed spruce-beech stands

concluded 06/2009



It is the declared aim of many state forest agencies to convert monocultures of Norway spruce (Picea abies), which are wide-spread in central Europe, to mixed stands of spruce and broadleaved trees, which in most cases would be European beech (Fagus sylvatica). Mixed species stands of these species may have a higher degree of ecological stability because they are less susceptible to windthrow and because nutrient cycling is tighter than in pure stands of spruce. Needle litter of Norway spruce is often less decomposable as that of the original forest, which was replaced by the plantations. As a result the forest floor layer tends to accumulate in many spruce monocultures. The build-up of the forest floor to humus forms such as moder and raw humus represents unfavourable biological soil conditions and a partial discoupling of the nutrient cycling. Additional consequences of this process may be soil acidification and podzolisation in pure spruce stands, which may further destabilise ecosystem processes. Introduction of beech, which can provide leaf litter of greater decomposability may reverse these processes and lead to more favourable humus forms that represent greater biological activity. However, it has been shown that the admixture of beech to spruce effectively leads to a reduced forest floor layer only for some soil types. This points to the importance of identifying the soil types and stand conditions for which the introduction of beech into spruce forest can lead to a significant improvement of the humus form and thus nutrient cycling. The proposed work will contribute to this by identifying sites, where admixture of F. sylvatica to P. abies stands will improve litter decomposition and thus the humus form. Specifically the research will examine how a range of environmental and litter quality factors influence the decomposition of beech and spruce litter, how litter quality is influenced by site quality, and what proportions of beech litter of a certain quality may be required to improve spruce needle decomposition.


Collaborators: Freiburg University, University of Bayreuth (Dr. B. Berg)
Funding: DAAD scholarship for M.-C. Gruselle, International PhD Programme
Duration: Oct. 2003 – Sept. 2006
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