MASS-LOSS OF URTICA-DIOICA L ROOTS IN A BEECHFOREST AS AFFECTED BY SOIL FAUNA AND SOIL TYPE

Mass loss of Urtica roots was studied with it? situ litterbag experime nts in a beechforest. Effects of soil fauna were determined by compari ng litterbag mesh sizes of 0.045, 1, and 10 mm. Effects of soil type w ere studied by comparing three elevations on a hill slope of a basalt outcrop from limestone. Two size classes of Urtica roots were compared . Mass loss and nitrogen contents were determined for eleven months. T he decomposition process was modelled using a two-component exponentia l function differentiating a fast (FDF) and a slow decaying fraction ( SDF). Initial decomposition was faster for fine than for coarse roots, leaving 50-54% and 70-79% ash-free dry weight after one month, respec tively. Proportions of FDFs were estimated to be 59% for fine roots an d 25% for coarse roots, while their decay rates did not differ. The av erage SDF decay rate of coarse roots was 56% higher compared to fine r oots. Overall decomposition of fine roots was higher in coarse compare d to medium and fine mesh litterbags. Decay times for 95% of initial m aterial of fine roots was estimated to be 2.3 yr in coarse mesh compar ed to 3.6 yr in medium or fine mesh. N contents differed between mesh sizes (fine > medium > coarse), indicating a negative effect on N-immo bilization of both meso- and macrofaunal grazing. Differences between soil types were small.