Factors affecting the nutrient status of forest sites in a mountain watershed in Nepal

Soil and foliage samples were collected from 136 sample sites in forested areas of the Dhulikhel Watershed, Nepal. Analyses showed that the soils have small values for pH, base saturation, total nitrogen, carbon and available phosphorus. Sample sites were stratified on the basis of aspect and elevation, soil type, forest type and management and the strata were compared to determine the influence of site factors on forest soil fertility. Soils on south-facing slopes at low elevation contained significantly less total nitrogen and organic carbon compared with soils from north-facing slopes at high elevation. Foliage of both sal (Shorea robusta Gaertn.) and chir pine (Pinus roxburghii Sargent) growing on red soils (Rhodustults and Haplustults) contained significantly less phosphorus compared with non-red soils (Ustochrepts and Dystrochrepts). Soils under stands of sal have the poorest soil fertility levels in comparison with chir pine and hardwood sites. The continuous removal of base-rich litter from sal sites may account for the poor fertility conditions. Soil fertility levels are greater on sites which have been protected from biomass removal for at least 15 years relative to sites which have come under protection in the past 7 years.