Estimation of leaf-litter production by dicotyledonous plants in grasslands

As part of a study of the effects of food quality on macrodecomposers, a ne w method for estimating rates of leaf-litter production by dicotyledonous p lants has been developed and tested for three grassland sites. The method i s based on estimations of i) rates of leaf abscission by monitoring increas es in the number of leaf-scars on shoots, ii) the mean weight of leaves, Ii i) the proportion of leaves removed by herbivores, and iv) the density of s hoots, to give monthly estimates of leaf-litter production. Litter producti on by 20 species was monitored for seven months. The three sites differed i n both the pattern and amount of dicotyledonous leaf-litter production whic h was strongly influenced by the extent of vertebrate and invertebrate herb ivory. By combining the detailed litter production estimates for one year, in which all the parameters were monitored throughout the season, with more approximate estimates of standing crop of dicotyledonous plants in other y ears, more approximate estimates of annual litter production were obtained over a 20-year period. The highest rates of dicotyledonous leaf-litter prod uction were on the site subjected to the highest levels of vertebrate grazi ng, which prompted a greater diversity and abundance of forbs relative to g rasses. Production rates on this site declined when grazing pressure became very intense. (C) Elsevier, Paris.