Methane and Carbon Dioxide Flux Heterogeneity Mediated by Termite Mounds in Moist Tropical Forest Soils of Himalayan Foothills, India

Abstract

Termites are dominant soil macro-fauna in tropical forests, yet remain an uncertain component of the carbon budget in many regions. We investigated CH4 and CO2 flux patterns from termite mounds and background soils of moist tropical deciduous forests in Indian lower Himalaya from April 2015 till March 2016 using static closed chamber technique. The relation between gas fluxes and soil moisture as well as temperature were examined. Termite (Odontotermes obesus) mounds were significant localized source of CH4 (0.38 ± 0.01 mg m−2 h−1) and CO2 (1837 ± 40 mg m−2 h−1) amidst CH4 consuming (– 0.028 ± 0.001 mg m−2 h−1) or lower CO2 emitting (1120 ± 19 mg m−2 h−1) background forest soils. Gas fluxes from termite mounds were seasonally bimodal (monsoon flux being highest followed by a second mild peak in winter) and diurnally variable. Soil moisture was a significant determinant of CH4 and CO2 fluxes from termite mounds, explaining more than 50% variability. In the case of background forest soils, the combined effect of soil moisture and temperature best explained CO2 and CH4 flux variation. On scaling up, termite mounds contributed negligibly (0.3%) to total soil CO2 emission while mound-mediated CH4 emission offset net soil CH4 uptake by 2.0%. Our results suggest considerable role of termite mounds in influencing source–sink capacity of forest soils. Present data are crucial in reducing error and uncertainty due to spatiotemporal variations in case of large-scale predictions. We suggest careful future land use decisions to minimize the contribution of mound-building termites to net soil CO2 and CH4 flux from this region.