Diurnal and monthly variations of carbon dioxide flux in an alpine shrub on the Qinghai-Tibet Plateau

摘要

Continuous CO_2 flux observation with eddy covariance method conducted in the alpine shrub on the Qinghai-Tibet Plateau indicates that there are distinct diurnal and monthly variations for CO_2 fluxes in the alpine shrub on the plateau. As for diurnal variation, with net CO_2 influx from 08:00 to 19:00 and net CO_2 efflux from 20:00 to 07:00, peak CO_2 flux during warm season (July) appears around 12:00 (-1.19 g CO_2 centre dot m~(-2) centre dot IT1); there is no obvious horary fluctuation for CO_2 flux during cold season (January), and horary CO_2 flux during most hours in a day is close to zero except for a small amount of net efflux (about 0.11 g CO_2 centre dot m~(-2) centre dot h~(-1)) from 11:00-17:00. As for monthly variation, with net CO_2 influx from June to September and net CO_2 efflux from January to May and October to December, the peak monthly CO_2 influx and CO_2 efflux appear in August and April, respectively. The total net CO_2 influx from June to September and total net CO_2 efflux from February to May and October to December in the alpine shrub on the Qinghai-Tibet Plateau are estimated to be 673 and 446 g CO_2 centre dot m~(-2). Results show that the alpine shrub on the Qinghai-Tibet Plateau is remarkable carbon dioxide sink under no grazing conditions and the total yearly CO_2 influx is estimated to be 227 g CO_2 centre dot m~(-2).