Influence of altitude gradient and overstorey composition on soil nutrient availability in the temperate Himalayan region

Altitude and overstorey composition types are important driving factors of soil nutrient dynamics in forest ecosystems. A comprehensive understanding of these factors is essential, as improved soil attributes support the overall health, productivity, and climate regulation functions of forest ecosystems. However, limited information is available on soil nutrient availability and the factors governing their variation in temperate forest ecosystems of the north-western Himalayas. Therefore, the present study examined soil organic carbon (OC), nitrogen (N), phosphorus (P), potassium (K), pH and electrical conductivity (EC) of temperate forest soil. 36 sample plots were established across four altitudinal ranges (1500–2000, 2000–2500, 2500–3000 and 3000–3500 m amsl) and three overstorey composition types (broadleaved, mixedwood, and pure conifer) in the temperate Himalayan region of Himachal Pradesh. Soil samples were taken randomly from the forest floor (FF), top soil (0–20 cm), and sub-soil (20–40 cm) for evaluation of soil properties. The analysis demonstrated that availability of OC, N and K increased with altitude up to 2000–2500 m amsl; however P availability increased up to 2500-3000 m amsl and decreased thereafter. Soil pH was comparatively invariant with altitude, meanwhile electrical conductivity was highest at 1500–2000 m amsl. Among the overstorey composition types, nutrient availability followed the order of mixedwood > broadleaved > conifer, which might be attributed to the higher organic matter inputs and more rapid decomposition in the soils under mixedwood stands. These outcomes facilitate broadening our understandings of soil nutrient dynamics and support the development of more effective long-term forest management strategies in the Himalayan region.