The effect of plant species, weather variables and chemical composition of plant material on decomposition in a tropical grassland

Abstract

The decomposition of litter and roots of Chenopodium album, Desmostachya bipinnata and mixed grass samples for a period of 402 days and of Dichanthium annulatum and Sesbania bispinosa for a period of 278 days was studied in a tropical grassland. Litter bags positioned at midcanopy height, soil surface and at five cm depth below the soil surface and root bags placed at 5, 15, 25 and 35 cm depths belowground were used. For the total study period, the cumulative weight loss in litter bags was: Chenopodium = 76-100%; Desmostachya = 33-98%; Dichanthium = 26-96%; mixed grass = 43-99% and Sesbania = 25-99%. The weight loss in root bags was: Chenopodium = 93-100%; Desmostachya = 47-56%; Dichanthium = 71 87%; mixed grass = 61-82%; Sesbania=87-100%. The nature of plant species affected decomposition rates. The position of litter/root bags also affected the decomposition rates. The mean relative decomposition rates of litter as well as of root material were found to be highest in rainy season and lowest in winter months. Rainfall, particularly the frequency of rainfall, was an important factor affecting decomposition rates. The litter species characterized by highest concentration of nitrogen, ash, acid detergent cell wall component and lowest concentration of carbon, cellulose and lignin, decomposed rapidly. In the case of roots, the material having high nitrogen, carbon, cellulose and ash content and low C/N ratio and lignin content decomposed rapidly.