BIOMASS AND PRODUCTION OF FINE AND COARSE ROOTS DURING REGROWTH OF A DISTURBED SUBTROPICAL HUMID FOREST IN NORTHEAST INDIA

Seasonal variation and depthwise distribution of dry matter in roots o f different diameter classes and their annual production were studied using sequential core sampling. The investigations were carried out in three stands of a subtropical humid forest of north-east India repres enting different stages of regrowth after tree cutting. The mean annua l standing crop of fine (<2 mm in diameter) and coarse (2-15 mm diamet er) roots increased gradually from 5.4 Mg ha(-1) and 0.7 Mg ha(-1) in 7-yr old regrowth to 9.4 Mg ha(-1) and 2.8 Mg ha(-1) in 16-yr old regr owth, respectively. The contribution of fine roots to the total root m ass declined from 88% in 7-yr old regrowth to 77% in both 13 and 16-yr old regrowths, while that of coarse roots increased from 12 to 23%. A major portion of fine roots (59-62%) was present in 0-10 cm soil laye r, but the coarse roots were concentrated in 10-20 cm soil depth (38-4 8%). In ail the three stands, biomass of both fine and coarse roots fo llowed a unimodal growth curve by showing a gradual increase from spri ng/pre-rainy season to autumn/post-rainy season. Biomass to necromass ratio increased from 2.5 in the 7-yr old to 3.2 in the 16-yr old stand . The annual fine root production increased from 5.9 Mg ha(-1) to 7.7 Mg ha(-1) and total root production from 7.6 Mg ha(-1) to 14.7 Mg ha(- 1) from 7-yr to 16-yr old regrowth.