CARBON AND NUTRIENT RELEASE FROM DECOMPOSING LITTER OF 4 SPECIES IN AN EXCESSIVELY RAIN-FED SUBTROPICAL GRASSLAND

The release patterns of carbon and six mineral elements (N, P, K, Na, Ca and Mg) from the decomposing litter of four dominant graminaceous s pecies, namely, Arundinella khaseana, Chrysopogon gryllus, Eragrostiel la leioptera and Eulalia trispicata, were studied in an excessively ra infed subtropical grassland at Cherrapunji. Carbon (50 % of ash-free d ry mass) loss was controlled by initial lignin concentration, and the elemental release was related to the initial concentrations of the res pective elements in the litter. The release patterns of elements did n ot parallel the loss pattern of carbon; annually, greater proportions of all nutrients, with the exception of nitrogen, were lost relative t o carbon. While carbon loss rates were higher during monsoon, nutrient release rates were greater during spring (early phase of decompositio n). Soon after the spring season, a short immobilization phase of nutr ients occurred for all elements except calcium. The time of nutrient i mmobilization recorded in this study conforms with the time of higher microbial activity in soil, and maximum phytomass production and nutri ent uptake studied previously in the same grassland system. These patt erns suggest that uptake of nutrients in growing phytomass and immobil ization in microbial biomass help conserve early released nutrients fr om decomposing litter against heavy runoff and leaching losses under t he influence of exceptionally high rainfall.