Dynamics of leaf litter decomposition of four tree species of arid western Rajasthan under varying soil moisture regimes

Abstract

Dynamics of decomposition of leaf litters of Acacia senegal, Dalbergia sissoo, Acacia tortilis and Colophospermum mopane were studied from June 2010-April 2011 at research farm of Central Arid Zone Research Institute, Regional Research Station, Bikaner (Rajasthan). The mass loss of leaf litters varied significantly with time, species and moisture content. Among different tree species, the mass loss of leaf litter followed the order A. tortilis> A. senegal > D. sissoo> C. mopane at both moisture levels (Field Capacity and 50 % field capacity). The wider C:N ratio (55: 1), high lignin (34.1 %) and lower N content (0.99 %) of C. mopane as compared to A. tortilis , A. senegal and D. sissoo resulted in lower decomposition rate of C. mopane as compared to the other species. The high lignin in C. mopane binds strongly to organic- N in litter, hence making its litter resistant to decomposition. The differences in decomposition rates among A. tortilis, A. senegal and D. sissoo litters can be attributed to variation in their N content and C:N ratio because lignin did not differ much among these litters. For all species, the decomposition data best fitted the exponential decay function. Accordingly, decomposition rate constants (k) for C. mopane were significantly lower than other species. Between the two moisture levels, the decay rate coefficient for each species were more in soils maintained at field capacity as compared to 50 % field capacity. The half lives or time required for 50% decay at field capacity soil moisture was lowest (54 days) for Acacia tortilis and highest (81 days) for litter of C. mopane. For 99% decay, litter of A. tortilis, C. mopane, D. Sissoo, A. senegal would require 390, 588, 510 and 485 days at field capacity and 495,746,675 and 568 days at 50 % field capacity, respectively.