CARDAMOM, MANDARIN AND NITROGEN-FIXING TREES IN AGROFORESTRY SYSTEMS IN INDIA HIMALAYAN REGION .1. LITTERFALL AND DECOMPOSITION

Litterfall and decomposition were studied in agroforestry systems invo lving large cardamom (Amomum subulatum) and mandarin (Citrus reticulat a) in the Sikkim Himalaya, India. There were stands with N-2-fixing tr ees (Alnus nepalensis over large cardamom, and Albizia stipulata over mandarin agroforestry) or without them (native non-symbiotic mixed tre e species) in both systems. The total annual litter (litter + crop res idue) production was higher in the Alnus-cardamom than in the forest-c ardamom stand and in the mandarin than in the Albizia-mandarin stand. The ratio of litter production to floor litter was higher in the N-2-f ixing stands than in the non-N-2-fixing stands, indicating a faster li tter turnover in the former. Tree litterfall occurred throughout the y ear, but with marked peaks during November to April, Total soluble pol yphenolics of fresh litter were higher in N-2-fixing species than in m ixed tree species and crops. Half-life values for ash-free mass were s hortest in the leaves of N-2-fixing species. N loss was higher from N- 2-fixing Alnus and Albizia leaves, whereas P loss was faster and nearl y equal in Alnus leaf litter and cardamom residue in cardamom, and Alb izia leaf litter and crop residue in mandarin agroforestry systems. Th e P turnover in N-2-fixing Alnus and Albizia twigs was faster than in the twigs of mixed tree species. The N-2-fixing tree species increased the N and P cycling through production of more above-ground litter an d influenced greater release of these nutrients.