Hydrological fluxes from Sal (Shorea robusta) forests under various disturbance gradients of Himalayan foothills

The disturbances caused to forests by human interferences have a significant impact on forest hydrology and the nutrient cycle. The stemflow, throughfall, interception loss, and runoff are the major components of the forest hydrology and play an active role in nutrients cycling. A study was therefore carried out in the Sal forests under various disturbance gradients in Himalayan foothills to quantify the rainfall partitioned components i.e. stemflow, throughfall, and interception loss; runoff; and chemical elements in rainfall partitioned components. During the study period, a total of 37 rainfall events were recorded for the rainfall partitioning study. Results showed that the significantly highest average stemflow was observed in the undisturbed Sal forest (3.7 ± 0.2%) and lowest in the disturbed Sal forest (1.7 ± 0.1%). A significantly highest average throughfall was observed in the disturbed Sal forest (65.2 ± 1.7%) and lowest in the undisturbed forest (57.8 ± 1.8%). Although the highest average interception loss was observed in the undisturbed forest (38.5 ± 1.8%) and lowest in the disturbed Sal forest type (33.2 ± 1.8%), it was not significant (p = 0.05). Significantly highest average runoff (22.2 ± 1.7%) was observed in the disturbed Sal forest while the lowest runoff (8.5 ± 1.8%) was observed in the undisturbed Sal forest type. It was also observed that nutrient enrichment i.e. N, P, and K to the soil through stemflow and throughfall was 18.6 times, 23.1 times, and 10.8 times more as compared to incident rainfall. From the statistical analysis, it was observed that average canopy spread, ground biomass, and average crown projection area were the most important parameters of the Sal forests which affected the proportion of rainfall partitioned components and runoff.