Diurnal dynamics of soil respiration and the influencing factors for three land-cover types in the hinterland of the Taklimakan Desert,China

Knowledge of soil respiration and the influencing factors in desert ecosystems is essential to understanding carbon dynamics and responses of biotic and abiotic processes in soils to climate change. In this study, soil respiration rate（R_s） for three land-cover types（shifting sandy land, sandy land with straw checkerboard barriers, and shelter forest land） in the hinterland of the Taklimakan Desert was measured in May 2015 using an automated soil CO_2 flux system. The effects of soil temperature（T_s） and soil water content（W_s） on R_s were also analyzed. The results showed that R_s values in shifting sandy land, sandy land with straw checkerboard barriers, and shelter forest land were all low and exhibited obvious diurnal fluctuations. The establishment of straw checkerboard barriers in sandy land had no significant effect on R_s, while the establishment of shelterbelts significantly increased R_s. Shifting sandy land and sandy land with straw checkerboard barriers were carbon sinks at night and early morning and were carbon sources in the daytime, while shelter forest land always acted as a carbon source during the whole day. The synergistic effect of T_s and W_s could better explain the diurnal dynamics in R_s than single factor. In shifting sandy land and sandy land with straw checkerboard barriers, W_s was identified as a limiting factor influencing the diurnal dynamics of R_s. Furthermore, a relatively strong hysteresis loop existed between R_s and T_s. In contrast, in shelter forest land, R_s was significantly influenced by T_s, and a relatively weaker hysteresis loop existed between R_s and W_s.

Precipitation Controls on Carbon Sinks in an Artificial Green Space in the Taklimakan Desert

Control of desertification can not only ameliorate the natural environment of arid regions but also convert desertified land into significant terrestrial carbon sinks,thereby bolstering the carbon sequestration capacity of arid ecosystems.However,longstanding neglect of the potential carbon sink benefits of desertification management,and its relationship with environmental factors,has limited the exploration of carbon sequestration potential.Based on CO_(2) flux and environmental factors of artificial protective forest in the Taklamakan Desert from 2018 to 2019,we found that the carbon storage capacity of the desert ecosystem increased approximately 140-fold after the establishment of an artificial shelter forest in the desert,due to plant photosynthesis.Precipitation levels less than 2 mm had no impact on carbon exchange in the artificial shelter forest,whereas a precipitation level of approximately 4 mm stimulated a decrease in the vapor pressure deficit over a short period of about three days,promoting photosynthesis and enhancing the carbon absorption of the artificial shelter forest.Precipitation events greater than 8 mm stimulated soil respiration to release CO_(2) and promoted plant photosynthesis.In the dynamic equilibrium where precipitation stimulates both soil respiration and photosynthesis,there is a significant threshold value of soil moisture at 5 cm(0.12 m^(3) m^(-3)),which can serve as a good indicator of the strength of the stimulatory effect of precipitation on both.These results provide important data support for quantifying the contribution of artificial afforestation to carbon sequestration in arid areas,and provide guidance for the development and implementation of artificial forest management measures.

Taklimakan desert carbon-sink decreases under climate change

The global carbon balance is a core issue in climate change research and a focus of in ternational policy concern[1-3].The"missing carbon sink"caused by approximately 1.6-2.0 Pg Ca-1(1 Pg=1015 g)that is currently unaccounted for,has long plagued researchers[4,5].Evidence is mounting those seemingly lifeless desert ecosystems,whose roles in the global carbon-cycle have long been neglected,exhib让the unconventional phenomenon of absorption of atmospheric CO2,sequestering enonnous amounts of CO2 and thereby creating a significant carbon-sink[6-9].