Changes and regulations of net ecosystem CO2 exchange across temporal scales in the Alxa Desert

Abstract

Arid ecosystems are an important component of the global carbon cycle. In these ecosystems, plant functional types are particularly important in realizing many ecosystem processes such as the dynamics and regulations of net ecosystem exchange of CO2 (NEE) to the changing environment. Here, we measured the diurnal dynamics of NEE in patches of succulent and non-succulent shrubs over two growing seasons (2012 and 2013) in the Alxa Desert, located in northern China. We find that the interannual difference of NEE was greater for the non-succulent shrub than that for he succulent shrub species. Diurnal NEE changes were similar for all species and were more strongly influenced by soil moisture than by temperature. Nonetheless, these environmental factors had a greater influence on non-succulent shrubs than succulent shrubs. Our findings highlight that species with different life history traits have different NEE dynamics and vary by time scales. These dynamics are strongly tied to water availability and plant type-specific water storage capacity, with plants possessing large water storage organs maintaining their physiological functioning better under stressful conditions. Our findings on the interaction between plant type and environment could be used to improve estimates of terrestrial carbon uptake in critical desert ecosystems.