Emissions Of Greenhouse Gas And Biochemical Properties Of Soil From Bhitarkanika Mangrove,Orissa

Coastal areas have been recognized as one of the major contributors to the atmospheric flux of greenhouse gases at local, regional and global scales. Mangrove forests are constantly affected from the anthropogenic activities mainly intensive cultivation. In a study in the tropical mangrove areas of Bhitarkanika sancturary, NE Orissa and adjoining paddy fields, a comparative estimation of emission rates of two climatologically important greenhouse gases, viz. CH4 and N2O were measured for monsoon and post-monsoon seasons. Methane emission was higher in paddy fields and varied from 2.22 to 6.0 mg.m-2.h-1 as compared to flux rates of 0.08 to 3.23 mg.m-2.h-1 from mangrove areas for the monsoon season. For the post-monsoon season, CH4 flux was higher although it maintained almost similar trend for the two ecosystems. In contrast, N2O emission flux was higher for mangrove sediments than the rice fields. Readily mineralizable carbon (RMC) and microbial biomass-C (MBC) contents were higher in the paddy soils than the native mangrove sediments so also dehydrogenase and FDA hydrolase activities, suggesting higher microbial activity in the paddy soils. Overall CH4 and N2O yields varied depending upon both the magnitude and chemical nature of the sediment C and N sources and microbial activity that were in turn affected by the salinity. Results indicate that paddy fields (anthropogenic intrusion) are bigger emitters of greenhouse gases than the mangrove sediments and together constitute a significant contributor to the global GHG budget.