Altitudinal and aspect-driven variations in soil carbon storage potential in sub-tropical Himalayan forest ecosystem:...

Forest soils serve as the greatest sink of terrestrial carbon (C) and have a significant impact on worldwide or regional C cycling. By reducing emissions and enhancing the C storage in forests, the environmental monitoring function of a forest ecosystem may be ensured. The study focused on measuring the densities of major nutrients in soil to gain insight into the C and nitrogen dynamics of the Himalayan sub-tropical forest ecosystem of India besides supplementing the information about the C storage potential of these forest soils. The study examined the physico-chemical properties and nutrient densities across three altitudinal ranges viz., 600-800 m (A₁), 800-1000 m (A₂) and 1000-1200 m (A₃) and two aspects, i.e. Northern (N) and Southern (S) in a randomized complete block design and data collection was done from 24 main sample plots (3 altitudinal ranges × 2 aspects × 4 replications). The soil pH, electrical conductivity, and bulk density observed a decreasing pattern with an increase in altitude, whereas a reverse trend was observed in soil organic C (SOC), total nitrogen and available phosphorus. The SOC and total nitrogen densities ranged from 20.08 to 48.35 Mg ha^-1 and 2.56 to 4.01 Mg ha^-1, respectively in an increasing trend from A₁ to A₃. The northern aspect exhibited significantly higher SOC and nitrogen densities than the southern aspects. The C storage potential of forest soils followed the order A₁ < A₂ < A₃ with significantly higher potential (nearly 1.5 times) compared to those on the southern aspect. There was a consistently significant increase in the C:N ratio (CNR) with a maximum value (10.51) at A₃ and minimum value (8.37) at A₁, however the effect of aspect remained insignificant. This research underscores the importance of considering altitude and aspect when planning forest restoration efforts, as these factors have a substantial influence on soil properties, C storage potential and CNR. Understanding the significance of CNR is critical, as it serves as a key indicator of greenhouse gas (GHG) emissions from forest soils. Ultimately, these findings empower policymakers and conservationists to make informed decisions that can contribute to the sustainable management of Himalayan forests and the global fight against climate change.