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

Background: Photosynthetic carbon released into the atmosphere in the form of carbon dioxide (CO2) which represented by soil respiration (SR), is considered the largest carbon (C) efflux of terrestrial ecosystem. Understanding the dynamics of SR is critical to coping with prevailing climate change from regional to global scale. Temperate forests are considered as most fragile hence need to recognize their vulnerability owing to continuous climatic changes and anthropogenic activities. Predicting the response of SR is essential, owing to the varying environmental factors that are most dominantly effective to become common determinants of forest carbon variability. This study aimed to assess SR by using closed chamber method in the natural Rhododendron arboretum forest in Annapurna Conservation Area (ACA) which is recognized as the world’s largest forest type located in a temperate region of Nepal. This research additionally aimed to evaluate the consequences of multiple ecological parameters mainly climatic and biotic factors on SR variations in consecutive two years measurement period in October 2016 and 2017.Results: Overall, SR in the forest well corresponded with the soil temperature (ST) variables. Within a short-range (2-3°C) of ST difference the variation in SR was recognized as highly significant (p<0.05) exponential curve (y=1.049e0.529x, 2016 and y = 26.34e0.284x, 2017). However, the effect of soil water content (SWC) on SR was scattered and clear effects of photosynthetic photon flux density (PPFD) were also not detected. Contrary to ST and SWC, seasonal trend of SR was compatible with the PPFD and litter input. The temporal, diurnal, and inter-annual variations of SR, ST, SWC and litter fall were accountable.Conclusions: Temperate forest could store the maximum amount of soil C with limited C emission through SR and become a larger sink of atmospheric CO2. SR is very sensitive to environmental changes and interactively affected by multiple ecological factors, even though it is often difficult to separate their interactions. This founding research is adequate measure in temperate Rhododendron forest; further study seeks understanding on how C emission responds to the regional climate warming, through changing precipitation and landuse, and integrates these feedbacks into global climate models and carbon budget.