Hydroclimatic controls on methane dynamics in freshwater and non-tidal saline teal carbon wetlands of the semi-arid region: evidence from ground and satellite observations

Abstract

The shallow inland (non-tidal) wetlands recognised as teal carbon ecosystems have remained poorly constrained in methane (CH4) dynamics due to strong sensitivity to hydrological and climatic variability. The current study quantified the spatio-temporal variability of CH4 across two ecologically different Ramsar wetlands in India: Keoladeo National Park (KNP) and Sambhar Lake (SL), representing shallow inland freshwater and saline (non-tidal) ecosystems. The bias-corrected CH4 observations were integrated with multi-sensor environmental predictors. Further, the satellite-derived indicators were analysed, including vegetation productivity, surface water dynamics, land surface temperature, and hydroclimatic variability from Sentinel-5P, Landsat-8/9, MODIS, and TerraClimate, respectively. The chamber-based ground measurements showed considerably higher methane fluxes in KNP (359.01 ± 326.11 mg CH4 m−2 yr−1) than in SL (3.68 ± 0.339 × 10−5 mg CH4 m−2 yr−1), indicating strong differences in methane dynamics between the freshwater and saline wetland ecosystems. Based on satellite observations, the monthly analysis showed an increase in CH4 levels from the pre-monsoon to the monsoon and post-monsoon periods at KNP, with peak median atmospheric XCH4 values during August–October (∼1945–1965 ppb). On the other hand, SL exhibited lower background concentrations (∼1900–1930 ppb) with short-lived post-monsoon enhancements (∼1960–1970 ppb) under inundation conditions. The seasonal differences in atmospheric XCH4 were statistically significant (p < 0.05), with the higher atmospheric methane values during the monsoon and post-monsoon seasons and the minimum values during the summer and winter seasons. The correlation analysis revealed that CH4 variability in KNP is primarily controlled by vegetation productivity and moisture availability (r = ∼ 0.52) and temperature-driven microbial activity. However, SL dynamics were dominated by the hydrological intermittency and salinity stress, with strong negative associations with atmospheric moisture deficit and climatic water stress (r = −0.56). The findings demonstrated the ecosystem-specific methane regimes and supported the inclusion of inland wetlands in climate-resilient carbon accounting and wetland management frameworks.