Assessment of biomass and carbon stock in subtropical Sal (Shorea robusta Gaertn. f.) forests in the North Western Himalayas

Sal forests (Shorea robusta) play an important role in climate change mitigation by sequestering carbon in biomass and soil for a very long duration. Their high biomass production and resilience improve their potential to buffer climatic impacts and promote sustainable forest ecosystems. The present study assessed carbon storage across seven Sal Forest compartments representing different site qualities, using 0.1 ha sample plots laid through a systematic random sampling design. The findings revealed significant differences in biomass, carbon density and soil properties, highlighting the importance of site quality in carbon dynamics. Trees, shrubs and herbs displayed significant inter-compartmental variation for density basal area and biomass traits. The compartments viz., Rajban C₁₀, Kukron C₁₄, Kukron C₁₅, Gorakhpur C₇, and Lai C₂₈, although showing the same site quality-II, displayed significant variation for the leaf litter and vegetation carbon density traits of trees, shrubs, herbs, as well as leaf litter, dead twigs and branches, dead trees, and total detritus biomass density. Significant variations were observed in total biomass (123.89-487.35 Mg ha⁻¹), vegetation carbon density (89.89-234.26 Mg C ha⁻¹), and ecosystem carbon density (114.53-287.58 Mg C ha⁻¹) (p < 0.0001). Kukron C₁₄ had the highest values for both vegetation and ecosystem carbon density. Organic carbon (%) (Labile), non-labile carbon, and available N, P and K were found to be related to site quality, displaying a maximum in Kukron C₁₄ (SQ-II) and a minimum in Rajban C₇ (SQ-III). The level of soil organic carbon (labile and non-labile carbon (%) micro- and macronutrients declined from the 0-20 cm to the 20-40 cm soil layer. However, the micronutrients- Zn, Fe, B and Cu did not show any significant variation among various compartments. The study revealed significant variations for biomass, carbon density and micro and macronutrients across the same as well as different site qualities, which suggest that compartment-specific management is required to be planned to increase the biomass productivity, carbon storage and mitigation potential and sustainable management of the Sal Forest ecosystem.