Seasonal Organic Carbon Variation in a Tropical Floodplain Wetland of Lower Brahmaputra Valley, Assam, India

Amulya Kakati; S. K. Bhagabati; Rajdeep Dutta; B. K. Bhattacharjya; Bhabesh Gogoi; U. K. Das; Simanku Borah

doi:10.56093/ft.v63i2.173553

Authors

Amulya Kakati ICAR-Central Inland Fisheries Research Institute, Regional Centre, Guwahati, Assam - 781006 & College of Fisheries, Assam Agricultural University, Raha, Nagaon, Assam - 782013
S. K. Bhagabati College of Fisheries, Assam Agricultural University, Raha, Nagaon, Assam - 782013
Rajdeep Dutta College of Fisheries, Assam Agricultural University, Raha, Nagaon, Assam - 782013
B. K. Bhattacharjya ICAR-Central Inland Fisheries Research Institute, Regional Centre, Guwahati, Assam - 781006
Bhabesh Gogoi College of Agriculture, Assam Agricultural University, Jorhat, Assam - 785013
U. K. Das College of Fisheries, Assam Agricultural University, Raha, Nagaon, Assam - 782013
Simanku Borah ICAR-Central Inland Fisheries Research Institute, Regional Centre, Guwahati, Assam - 781006

https://doi.org/10.56093/ft.v63i2.173553

Keywords:

Deepor beel, wetland, soil organic carbon, carbon stock, organic matter, bulk density

Abstract

The study was aimed to assess depth-wise seasonal variability of bulk density (BD), soil organic carbon (SOC), SOC stock and soil organic matter (OM) in Deepor beel (a Ramsar site) located in lower Brahmaputra valley zone of Assam with a water spread area of about 40 km². Samples were collected during January to December, 2023 from six sites covering four seasons namely, pre-monsoon (March- May), monsoon (June-September), post-monsoon (October-November), and winter (late December-February). Samples were collected at depth intervals, 0–10 cm and 10–20 cm using a handheld metallic cylindrical core sampler measuring 200 cm in length and 2.5 cm in diameter. Results revealed that mean BD values in the wetland ranged between 0.46 ± 0.16 g cm^-3 to 1.21 ± 0.07 g cm^-3. Sub-surface soil (10–20 cm) exhibited comparatively higher BD (0.56 ± 0.07 to 1.21 ± 0.07 g cm-3) than surface soil (0–10 cm) (0.46 ± 0.16 to 1.16 ± 0.08g cm-3). SOC content ranged from 1.03% to 3.16%. Surface soil layer exhibited higher SOC content (1.38–3.16%, with mean value of 2.22 ± 0.10%) than sub-surface soil (1.03–2.07%, with mean value of 1.86 ± 0.09%). SOC stock was found to fluctuate from 4.04 to 30.9 Mg C ha^-1, OM content ranged between 1.77% and 5.44%. One way ANOVA revealed significant
seasonal differences between SOC stock and BD (p < 0.01) but SOC and OM did not show any significant seasonal variation. Results indicated that hydrological cycles strongly regulate soil organic carbon content, with enhanced accumulation during monsoon, post-monsoon and winter, and losses during pre-monsoon. The present study is the first known attempt to estimate soil carbon stocks across depths and seasons from Deepor beel, a Ramsar site of international importance. The findings of this study will help to establish a baseline dataset that may serve as a reference for future assessments of carbon storage capacity in this highly important peri-urban wetland as well as for similar ecosystems in the region, at the same time highlighting its potential as a carbon sink for climate change mitigation.