Long-term measurements of CO_2 flux and evapotranspiration in a Chihuahuan desert grassland

摘要

We measured CO_2 and evapotranspiration (ET) fluxes above a Chihuahuan desert grassland from 1996 through 2001. Averaged across six years, this ecosystem was a source (positive flux) of CO_2 in every month. Over that period, sustained periods of carbon uptake (negative flux) were rare. Averaged across all months, we estimated that CO_2 was being released into the atmosphere at a rate of + 1.5 g CO_2m~(-2)d~(-1) ( + 0.40 g Cm~(-2)d~(-1)) or + 533 g CO_2m~(-2)yr~(-1) ( + 145.3 g Cm~(-2)yr~(-1)). Average ET was 299 mm yr~(-1) with a monthly range of 0.15 mm d~(-1) in December to 2.15 mmd~(-1) in August.