Variation of biomass and carbon pool with NDVI and altitude in sub-tropical forests of northwestern Himalaya.

In the present study, forests at three altitudes, viz., A1 (600-900 m), A2 (900-1200 m) and A3 (1200-1500 m) above mean sea level having normalised differential vegetation index (NDVI) values of N1 (0.0-0.1), N2 (0.1-0.2), N3 (0.2-0.3), N4 (0.3-0.4) and N5 (0.4-0.5) were selected for studying their relationship with the biomass and carbon pool in the state of Himachal Pradesh, India. The study reported maximum stem density of (928 trees ha-1) at the A2 altitude and minimum in the A3 and A1 with 600 trees ha-1 each. The stem densities in relation to NDVIs were observed in the order N5 > N3 > N4 > N1 > N2 and did not show any definite trend with increasing altitude. Highest stem volume (295.7 m3 ha-1) was observed in N1 NDVI and minimum (194.1 m3 ha-1) in N3 index. The trend observed for stem biomass at different altitudes was A3 > A1 > A2 and for NDVIs, it was N5 > N1 > N4 > N2 > N3. Maximum aboveground biomass (265.83 t ha-1) was recorded in the 0.0-0.1 NDVI and minimum (169.05 t ha-1) in 0.2-0.3 NDVI index. Significantly, maximum total soil carbon density (90.82 t C ha-1) was observed in 0.4-0.5 NDVI followed by 0.3-0.4 NDVI (77.12 t C ha-1). The relationship between soil carbon and other studied parameters was derived through different functions simultaneously. Cubic function showed highest r 2 in most cases, followed by power, inverse and exponential function. The relationship with NDVI showed highest r 2 (0.62) through cubic functions. In relationship between ecosystem carbon with other parameters of different altitudinal gradient and NDVI, only one positively significant relation was formed with total density (0.579) through cubic function. The present study thus reveals that soil carbon density was directly related to altitude and NDVIs, but the vegetation carbon density did not bear any significant relation with altitude and NDVI.