Variation in biomass and net primary productivity in short rotation high density central Himalayan poplar plantations

Abstract

This study describes biomass (dry weight) and net primary productivity (NPP) in four (1 to 4-yr-old) poplar ( Populus deltoides Marsh) plantations growing after clear felling of natural sal ( Shorea robusta: Dipterocarpaceae) mixed-broad leaved forest in the Tarai belt (low lying lands with high water table) adjacent to foot hills of central Himalayan mountains. The linear regression equations for all the above ground and below ground components of trees and shrubs were developed for each plantation. Understorey vegetation, forest floor biomass and litter fall were also determined from plantations. The tree density was 666 trees ha −1 for each plantation. The basal area, biomass, forest floor litter mass, tree litter fall and net primary productivity of trees increased with increase in plantation age, whereas the herb biomass and NPP significantly ( P < 0.01) decreased with increasing plantation age. The shrubs were present only in 4-yr-old plantation. The total vegetation biomass increased from 12.0 in the 1-yr-old to 113.0 t ha −1 in the 4-yr-old plantation and NPP from 19.0 in the 1-yr-old to 32.4 t ha −1 yr −1 in the 4-yr-old plantation. The biomass accumulation ratio (BAR, biomass:net production) for different tree components increased with increase in plantation age. The BAR ratio ranged from 0.6 in the 1-yr-old to 3.7 in the 4-yr-old plantation.