Effect of anthropogenic disturbance on biomass allocation to different above- and below-ground vegetation components of a dry tropical forest in India

Biotic and anthropogenic disturbances are mediating changes in species diversity and vegetation composition in different regions of the world. Such changes may affect plant biomass allocation patterns in different tree components and vegetation types. To assess the impact of anthropogenic disturbances such as grazing, lopping, harvesting of non-wood forest products, fuel wood and fodder collections on biomass allocation to different components of the vegetation, two study sites i.e., one undisturbed site and the other a disturbed site located in the Barnawapara Wildlife Sanctuary, Chhattisgarh were selected. Biomass allocation was measured by placing ten (10 m x 10 m) quadrats randomly, at both the forest sites (i.e., disturbed and undisturbed). Based on the regression equations relating tree circumference to dry weight of components (viz., bole, branch, leaf, and root), biomass of different vegetation components (i.e., above- and below-ground) was measured. Total biomass (above- and below-ground, including herbaceous shoots and litter mass) was significantly (P < 0.05) higher on the undisturbed site (360.38 t ha(-1)) compared to the disturbed site (113.99 t ha(-1)). Among different above-ground components, most of the biomass was allocated to branches followed by bole and leaf. Above-ground biomass ranged between 76.47 and 270.87 t ha(-1) with higher value at undisturbed forest site and the lower at the disturbed forest site. The below-ground biomass varied between 37.52 and 89.51 t ha(-1), and like above-ground biomass it was also higher at the undisturbed forest site and lower at the disturbed forest site. A higher (similar to 8%) biomass allocation to below-ground component was observed at the disturbed site, compared to the undisturbed site. Moreover, the proportion of biomass in the herb layer was higher at the disturbed site compared to the undisturbed site. Based on the results of present study, it can be concluded that under the disturbed conditions plants allocate major portion of the biomass to the below-ground and herbaceous components in the tropical dry deciduous ecosystems.