ECOSYSTEM PROCESSES IN SEMI-ARID GRASSLANDS .2. LITTER PRODUCTION, DECOMPOSITION AND NUTRIENT DYNAMICS

Changes in tissue nutrient concentration and nutrient uptake of a C3 native grassland and a sown C4 buffel grassland community, growing on infertile sandy red earth soils near Charleville, were studied. The seasonal pattern of litter production of grasslands in the grazed and ungrazed situation was also investigated. Studies in litter decomposition of Mitchell grass are reported. The decline in the above-ground biomass growth rate of both communities over the summer growing period corresponded with a similar trend in the uptake of nitrogen and phosphorus. Moreover, tissue shoot phosphorus concentrations of all perennial grass species were always low. The total amount of nutrient absorbed (nitrogen, phosphorus) was about 35% greater for the buffel compared with the native grassland community. Both communities could be contrasted with respect to the efficiency of nutrient absorption and nutrient utilization. Continued overgrazing led to a reduction in litter and root yield. As little biomass was produced by the community over the autumn-winter period, the litter production rate could be expressed as a function of herbage yield at the commencement of the period and was found to be relatively independent of grazing pressure. The agronomic and ecological implications of these results are discussed in relation to the management of these grasslands. © 1979 CSIRO.