Seasonal dynamics of soil and microbial respiration in the banj oak and chir pine forest of the central Himalaya, India

Abstract

This research investigates seasonal changes of root respiration (Rroot), total soil respiration (Rtotal) and microbial respiration (Rmicrobial) in three central Himalayan forest types: banj oak (BO), chir pine (CP) and banj oak regenerated (BOR). The trenching method is used to separate Rroot from Rtotal. Soil physicochemical and biological properties were compared among the forest type and seasons using one-way ANOVA. Results indicated the significant (p < 0.05) influence of forest type and season on Rtotal, Rroot and Rmicrobial. BO forest had significantly (p < 0.05) higher Rtotal than the CP forest. This was attributed to lower bulk density (BD), pH and high soil moisture, soil organic carbon (SOC), total nitrogen (TN) and microbial biomass carbon (MBC) in the BO forest. Higher soil moisture, SOC, TN and MBC in BO reflects higher microbial metabolic activity than the CP, with low soil moisture and nutrient content. The Rroot/Rtotal ratio ranged from 35 to 62 % for BO, 12 to 58 % for CP and 14 to 45 % for BOR, indicating that Rroot was an important contributor to Rtotal. The contribution of Rroot was at a maximum in the rainy season (53 %) and a minimum in the winter season (11 %), indicating the synergistic effect of optimum soil micro-climatic conditions and soil nutrient content to Rroot. In an exponential regression analysis, soil temperature better explained Rtotal (r2 = 0.81–0.82, p < 0.001). In comparison to Rmicrobial (r2 = 0.58–0.85, p < 0.001), Rroot is better explained by soil moisture (r2 = 0.59–0.88, p < 0.001) in a linear regression model. Present findings suggest that the positive effect of temperature, moisture and litter nitrogen on Rtotal are majorly regulated by forest types, which potentially increases the understanding of climate change and nutrient dynamic processes on a global scale.