Project: MetFlux India

Carbon exchange studies at natural ecosystems

The Indian forest is believed to be a net sink of CO2, but the carbon dynamics show a substantial variability in different spatial and temporal time scales. Understanding of source and sink relationship of CO2 and their variation with space and time is essential to better understand the spatio-temporal variability of carbon fluxes. The north-eastern part of India is endowed with a rich and varied biophysical environment because of its unique geographical location, relatively greater distance from the mainland, vast mountainous terrain, dense forests, heavy rainfall, wetlands and frequent floods have created a geographical remoteness of this area. Thus, it is essential to quantify the CO2 fluxes of the forest ecosystems of this region to have a better understanding of carbon dynamics. To fulfil this aim, an eddy-covariance based observation is set up at the Kaziranga National Park in Assam. We plan to monitor the exchange of CO2, H2O and energy between the forest and the atmosphere as well as to identify the environmental, plant and soil factors that control the exchange processes from intra-seasonal to decadal time scales.

Carbon and water cycle coupling at the Kaziranga forest

The carbon flux study carried out at the Kaziranga forest in Assam reveals that the ecosystem releases soil CO2 significantly higher than the other forest ecosystems in India. This characteristic feature probably makes this ecosystem a net carbon source in the atmosphere. Further, a combined analysis of precipitation isotopes and eddy-covariance data reveals that higher plant transpiration rates and productivity are strongly linked during the pre-monsoon season (March to May) but weak in other seasons.

Under the global warming scenario, the study may have concerning implications. Analysis of the rainfall data shows that rainfall in this region has decreased for several decades, especially during the pre-monsoon season. The amount of rain derived from the locally generated moisture, through transpiration, is also experiencing a reducing trend this season. This is especially significant for March-April because this is the time an enhanced hydrological cycle triggers the primary productivity. A reducing trend in rainfall may affect both the ecosystem productivity and the transpiration process. If the plant productivity weakens, it may further affect the carbon sequestration capacity of this fragile ecosystem of northeast India. So over a long-term period, the forest may emit more CO2 into the atmosphere. These studies are published as shown below:

Sarma, D, Deb Burman, P.K., Chakraborty, S., Gogoi, N., Bora, A., Metya, A., Datye, A., Murkute, C., Karipot, K. 2022 Quantifying the net ecosystem exchange at a semi-deciduous forest in northeast India from intra-seasonal to seasonal time scale. Agricul. Forest Meteor. 314 (2022) 108786.

Chakraborty, S., Burman, P.K.D., Sarma, D. et al. 2022 Linkage between precipitation isotopes and biosphere-atmosphere interaction observed in northeast India. npj Clim Atmos Sci 5, 10.;