Variation in soil physico-chemical properties and species composition across the altitudinal gradient in different...

Soil is a vital component of forest ecosystems, influencing productivity and ecological health. This study examines variations in soil physico-chemical properties and species composition across four forest types-Shorea robusta (Sal), Pinus roxburghii (Chir-pine), Quercus leucotrichophora (Banj-oak), and mixed Banj-oak-at elevations ranging from 600 to 1900 m asl in Nainital, Uttarakhand, India. Soil samples were collected at three depths (0-10 cm, 10-20 cm, and 20-30 cm) and analyzed for physical and chemical characteristics. Results indicated that with increasing altitude, water-holding capacity, soil moisture, total nitrogen, organic carbon, tree/shrub/herb density, species richness and tree basal area generally increased, while bulk density, porosity, and pH decreased significantly. Oak forests exhibited superior soil moisture, water retention, organic carbon, and nitrogen compared to Chir-pine and Sal forests. Mixed Banj-oak forests had the highest tree, shrub and herb density, species diversity, and basal area, followed by Banj-oak, Sal, and Chir-pine forests. These findings highlight the ecological benefits of oak-dominated forests, which enhance soil fertility and biodiversity. Consequently, oak forests should be prioritized over pine and Sal forests in afforestation and conservation programs to sustain ecosystem health and productivity in the Himalayan region.