Biomass production, carbon sequestration and water transmission properties as influenced by densified plantations raised on old river bed lands in the north west Himalayas

Old river bed lands in the North West Himalayas have generally been utilized for the production of fodder and firewood but its quantative biomass production and resource (carbon and water) conservation potential have not been worked out. Plantations of three tree speciesDrumm, L.-Grewⁱa optiva Drumm, Bauhinia variegata L. and Dalbergia sissoo Roxb. were raised during 1996, at 2x2m (close), 3x2m (medium) and 4x2 m (wide) spacings and were thinned mechanically at the age of 7,12 and 15 years. The performance of D.sissoo was the best with trees attaining an average height of 9.87 m and 10.3 m in the 7^th year and 12^th year, respectively. G.optiva trees attained an average height of 5.67 m and 6.20 m at the same age. Foliage (as fodder) availability from annual prunings in G. optiva declined from the 11^th year and woody biomass from the 8^th year. More woody biomass was obtained at medium spacing and that of foliage at close spacing. First thinning in the 7^th year yielded 54.70,20.45 and 13.65t ha^-1 of woody biomass at close spacing in D.sissoo, G.optiva and B.variegata, respectively, followed by production from medium and wide spacing. During the 2^nd thinning at the 12^th year, maximum woody biomass (100.50 t ha^-1) was obtained from D.sissoo at medium spacing followed by 53.43 t ha^-1 from G.optiva at wide spacing and 34.94 t ha^-1 from B.variegata at medium spacing. Annual rate of increase of SOC in the 0–45 cm soil depth ranged from 502 to 1410 kg C ha^-1. The humification rate was determined to be 0.195. Carbon sequestration rate varied from 1.32 to 0.55t ha^-1 yr^-1 and followed the trend of D.sissoo ¼ B.variegata ¼ G.optiva