Fine Root Dynamics: Belowground Carbon and Nutrient Cycling in Oak, Pine, and Oak–Pine Mixed Forests of the Central Himalaya

Fine roots (<2 mm in diameter) are among the most functional components of the plant system, playing a critical role in nutrient and water uptake as well as in regulating the carbon cycle. Despite their importance, fine roots remain one of the least studied components of forest ecosystems, even though they make a substantial contribution to forest productivity, carbon allocation, nutrient uptake, and turnover.
In the Himalaya, banj oak (Quercus leucotrichophora) is a major forest forming species that is increasingly challenged by the encroachment of chir pine (Pinus roxburghii), along with anthropogenic disturbances and climate change. While aboveground dynamics of banj oak and chir pine forests are well documented, studies on belowground processes are limited.  The present study aims to understand fine root dynamics, including biomass, productivity, turnover, and nutrient concentration, in banj oak, chir pine, and banj oak-chir pine mixed forests, and to assess the belowground impacts of chir pine encroachment into banj oak forests.
Three sites were selected for each forest type following a reconnaissance survey. Site selection was based on forest age structure determined through phytosociological analysis. Aspect, slope, elevation, and terrain were also considered to ensure comparability among sub-sites. At each selected site, a uniform plot was established, and six sub-plots were marked for fine root sampling using the sequential coring method. Five samples were collected from each sub-plot on a monthly basis. Sampling involved removal of surface litter followed by coring up to 30 cm soil depth using an 8 cm diameter corer.  The separated roots are oven-dried at 65°C until constant weight achieved. Dried samples are grounded using a Willey mill and stored in plastic containers for further analysis.
Preliminary results indicate that fine root biomass production is highest in banj oak forests, followed by oak–pine mixed forests and pine forests, reflecting distinct patterns of carbon allocation and belowground dynamics among the three forest types. Fine root turnover rates are lowest in pine forests, suggesting rapid growth and mortality of fine roots in pine-dominated stands. The study will provide important insights into belowground processes associated with chir pine encroachment into banj oak forests and will aid in assessing ecosystem services related to fine root production, carbon cycling, and nutrient dynamics in Himalayan forest ecosystems.