Soil Respiration Variations in Temperate Rhododendron (Rhododendron arboreum) Forest of Annapurna Conservation Area (ACA) in Nepal

Abstract

Temperate forests are considered most fragile hence need to recognize their vulnerability owing to continuous climatic changes and anthropogenic activities. In this study, we assessed soil respiration (SR) by using the chamber method in a natural Rhododendron (Rhododendron arboreum) forest which is recognized as the world’s largest forest type located at Annapurna Conservation Area in the temperate region of Nepal. We evaluated the consequences of multiple ecological parameters mainly climatic and biotic factors on SR variations during the month of October in 2016 and 2017. Our results confirmed that SR well corresponded with soil temperature (ST) variables represented with the highly significant ( $p<0.05$ ) exponential curve (y = 1.049e0.529x, 2016 and y = 26.34e0.284x, 2017). And the variation in SR was mediated by a short-range (2-3°C) of ST difference in the month of October during autumn season. However, the effect of soil water content (SWC) on SR was scattered and the photosynthetic photon flux density (PPFD) stood weak to represent the SR variation. The seasonal trend of SR was compatible with the PPFD and litter input with having accountable temporal, diurnal, and interannual variations of SR, ST, SWC, and litterfall. The SR over the entire measurement period were averaged at 269.9 mg CO2 m−2·h−1 in 2016 and 295.1 mg CO2 m−2·h−1 in 2017. Our study manifested that temperate forests could store maximum soil carbon with limited emission through SR and become a larger sink of atmospheric carbon dioxide even though SR is very sensitive to environmental changes and interactively affected by multiple ecological factors. Thus, our finding is an appreciable measure for the temperate forest to understand the regional carbon balance and suggested temperate forests are valued to incorporate them in evaluating global carbon budget.