Dynamics of Carbon and Water fluxes in Grassland Ecosystem of Thar Desert

Abstract

A study was conducted during 2011-2012 in Indian Thar desert at Central Arid Zone Research experimental station under hot arid environment to understand the coupling between micrometeorological parameters and ecophysiology of a dominant C4 grass Lasiurus sindicus. Energy balance components were computed at half-hourly interval. Photosynthesis and respiration of Lasiurus sindicus was measured using Infra-red gas analyser (LICOR-6400 XT). Biomass was collected through destructive method at every 15 days interval from 2nd Week of April to 3rd week of August during the study period. During growing season, species exhibited bimodal distribution in their diurnal photosynthetic rates with first peak (13-15 μmol CO2m-2s-1) around 10:00 hours and second but higher rate (18-20 μmol CO2m-2s-1) around 16:00 hours. The maximum light use efficiency (2.73 gMJ-1) was during morning and evening hours with occasional dip (0.47gMJ-1) in the noon hours. Leaf to air vapour pressure difference was more due to more difference in leaf to air temperature from 23:00 hours to early morning 05:00 hours that might have reduced stomatal conductance. Night-time leaf temperature was consistently lower than ambient, which must have favored diffusion of gases including moisture into intercellular spaces. Leaf-air temperature difference increases progressively during night from 20:00 hours to early morning 03:00 hours. The net primary productivity showed that L. sindicus grass acted as a carbon sink and has fixed ~3.20 t ha-1 carbon. Also, it has the ability to ameliorate the extreme climate on account of fixation of carbon in vegetation and soil.