Litter- and soil carbohydrate-carbon stocks in 2-, 4- and 10-year-old improved fallows in eastern Zambia

Abstract

This study evaluated the effects of tree species and sites on soil carbohydrates, litterfall, and litter chemistry in 2-, 4- and 10-year-old improved fallows at three sites in eastern Zambia. Between April 2002 and August 2003, litter was collected in 2-year-old tree fallows at Kalichero, Kalunga and Msekera for chemical analyses. Soil samples collected at 0–30 cm from all experiments were analysed for total soil organic carbon (SOC), but only those from 4- and 10-year-old fallows were analysed for carbohydrates. Soil arabinose- and mannose-C stocks, and carbohydrate-C percentages of SOC (7.7–20.6 %) significantly (P < 0.05) differed across tree species in 10-year-old coppicing fallows at Msekera. Converting M + F to improved fallows resulted in a decline in monosaccharide-C, carbohydrate-C stocks and carbohydrate-C percentage of SOC. There were significant (P < 0.05) variations in litterfall (0.7–2.3 t ha−1 year−1) and litter C contents (0.3–1.1 t ha−1 year−1) across 2-year-old coppicing tree fallows at Msekera. Litter production and C contents were significantly greater on sandy soils at Kalunga than on fine-textured soils at Msekera. Litter chemical contents (C, N, AUR and polyphenols) and ratios (C:N, P:N, AUR:N, and (AUR + P):N) for litter in fallows differed significantly (P < 0.05) across species and sites. In this study, the role of litter in carbon cycling in improved fallows depended on tree species and site conditions.