Kinetics of litter decomposition in restored forest soils

The influence of various methods of mechanical restoration of forest soils (like dredger, row-milling and extensive milling) on the kinetics of beech litter decomposition was studied for a 0 to 48 weeks period at different soil depths and different mesh sizes. A standard hand planting area was chosen as a control site. The minicontainer-technique was proved to be a useful technique for comparative decomposition studies. The distinct gleyic luvisols at Landscheid study site showed a sigmoidal kinetic of decomposition for the mechanically restored sites and a more homogeneous one for the control site, respectively. The rate of decomposition (0-8 (12) cm depth; coarse mesh sizes) was 0.57 % week(-1) (control) and 0.03 % to 0.12 % week(-1) (mechanically restored sites) in a first period from the beginning of the exposure until week 24 and 1.50 % week(-1) and 1.45 % to 1.98 % week(-1) in a period from week 24 until 48, respectively. At the cambisols at Ellerspring and at Thiergarten study site homogeneous (control) to moderate sigmoidal (mechanical restored sites) kinetics of decomposition were found. The comparable decomposition rates varied from 1.14 % to 1.89 % week(-1) (first period) and 0.78 % to 1.58 % week(-1) (second period) at the control site and from 0.28 % to 0.96 % week(-1) (first period) and 1.45 % to 1.98 % week(-1) (second period) at the mechanically restored sites, respectively. As a consequence of the drastical altering of the physical and chemical soil properties and of the population of soil organisms which facilitate the breakdown and mineralisation of soil organic matter, litter decomposition was higher in control sites than in mechanically restored sites during the first period (in general from week 0 to 24). At the end of a second period from week 24 to 48 the decomposition rate was higher in the mechanically restored sites, especially in the deeper horizons, explainable by the positive influences of loosening, mixing and liming of the treated soils and probably by a re-establishment of decomposer organisms. The mentioned homogeneous and sigmodial decomposition kinetics can be explained by environmental changes in the treated soils, climatic conditions during the exposure period (dry spring and summer) and the aged beech litter used.