The effect of Indian summer monsoon on the seasonal variation of carbon sequestration by a forest ecosystem over North‑East India

摘要

The Indian summer monsoon is one of the most important yet less understood synoptic processes on the Earth, characterizedby an increased amount of rainfall over the entire Indian landmass. The different types of forest ecosystemsexisting over the Indian region offer a tremendous carbon sequestration potential useful for the global mitigation ofclimate change as predicted by the modelling studies. The monsoon results in a strong seasonality of the ecosystematmospherecarbon exchange due to the differential availability of two key controlling parameters of photosynthesisnamely radiation and water. However, due to the sparsity of surface observations neither the carbon sequestrationpotential of these ecosystems nor its relation with the monsoon has been analysed comprehensively so far. This paperstudies the ecosystem-atmosphere CO2exchange at a tropical semi-evergreen moist deciduous forest and its relation withthe monsoon over north-east India using the eddy covariance and associated meteorological measurements. In 2016,this ecosystem acts as a net source of atmospheric CO2with net ecosystem exchange of 207.51 ± 157.37 gC m−2 year~（−1）and gross photosynthesis and ecosystem respiration of 2604.88 ± 179.43 and 2812.38 ± 22.05 gC m~（−2） year−1, respectively.The monsoon clouds are seen to introduce a bimodal pattern in the annual GPP record. The pre-monsoon and winterare the most and least favourable seasons for the photosynthetic CO2uptake by this forest canopy. Additionally, the rateof increase of photosynthesis with evapotranspiration is maximum and minimum during the pre-monsoon and winter,respectively.