干旱区生态环境知识资源中心

The Ejin oasis, located on the river sides of a hyper-arid region, represents some of the richest desert ecosystems, populated with riparian forest. Water availability is the main limited factors for the distribution and growth of the forest. Currently, the water-carbon process and mechanisms in the desert riparian forest remain uncertain. The study investigated the seasonal and inter-annual variations in the gross primary productivity (GPP), evapotranspiration (ET) and ecosystem water use efficiency (WUE), and their relationships with the event (e.g., irrigation) and climatic factors. The results showed that the desert riparian forest produced new plant biomass with 0.79 g C kg(-1) of water loss during the growing season. In the study period, monthly GPP and ET was tightly coupled, and the mean cumulative GPP and ET from May-October were 676 g C m(-2) and 864 mm, respectively. Daily GPP and ET had similar relationships with global radiation (R-g), air temperature (T-a) and vapor pressure deficit at monthly scale. Consequently, the seasonal variations in WUE were not obvious in the growing season, except in September. In September, the value of WUE decreased significantly with an increase in T-a (for T-a > 15 A degrees C) after irrigation, which was attributable to the increased ET and a relatively steady GPP. It is possible that the time of irrigation is able to affect the seasonal course of WUE. The study has implications that enable more rational water management to maintain the the health and activities of the riparian forest in such a hyper-arid region.