title: Sensitivity of temperate desert steppe carbon exchange to seasonal droughts and precipitation variations in Inner Mongolia, China.
abstract: Arid grassland ecosystems have significant interannual variation in carbon exchange; however, it is unclear how environmental factors influence carbon exchange in different hydrological years. In this study, the eddy covariance technique was used to investigate the seasonal and interannual variability of CO₂ flux over a temperate desert steppe in Inner Mongolia, China from 2008 to 2010. The amounts and times of precipitation varied significantly throughout the study period. The precipitation in 2009 (186.4 mm) was close to the long-term average (183.9±47.6 mm), while the precipitation in 2008 (136.3 mm) and 2010 (141.3 mm) was approximately a quarter below the long-term average. The temperate desert steppe showed carbon neutrality for atmospheric CO₂ throughout the study period, with a net ecosystem carbon dioxide exchange (NEE) of -7.2, -22.9, and 26.0 g C m⁻² yr⁻¹ in 2008, 2009, and 2010, not significantly different from zero. The ecosystem gained more carbon in 2009 compared to other two relatively dry years, while there was significant difference in carbon uptake between 2008 and 2010, although both years recorded similar annual precipitation. The results suggest that summer precipitation is a key factor determining annual NEE. The apparent quantum yield and saturation value of NEE (NEE(sat)) and the temperature sensitivity coefficient of ecosystem respiration (R(eco)) exhibited significant variations. The values of NEE(sat) were -2.6, -2.9, and -1.4 µmol CO₂ m⁻² s⁻¹ in 2008, 2009, and 2010, respectively. Drought suppressed both the gross primary production (GPP) and R(eco), and the drought sensitivity of GPP was greater than that of R(eco). The soil water content sensitivity of GPP was high during the dry year of 2008 with limited soil moisture availability. Our results suggest the carbon balance of this temperate desert steppe was not only sensitive to total annual precipitation, but also to its seasonal distribution.
authors: Key Laboratory of Arid Climatic Change and Reducing Disaster of Gansu Province, Key Open Laboratory of Arid Climatic Change and Disaster Reduction of China Meteorological Administration-CMA, Institute of Arid Meteorology, CMA, Lanzhou, China.
authors: Fulin
authors: F
authors: Yang
authors: Guangsheng
authors: G
authors: Zhou
mesh_terms: D002244:Carbon / Q000032:analysis*; D002681:China; D003889:Desert Climate; D055864:Droughts
chemical_list: D002244:Carbon
references: New Phytol. 2009;182(2):451-460
references: 19220762
references: New Phytol. 2008;177(1):209-219
references: 17944829
references: Nature. 2005 Sep 22;437(7058):529-33
references: 16177786
references: Sci Total Environ. 2011 Dec 1;410-411:182-90
references: 22024234
references: Philos Trans R Soc Lond B Biol Sci. 2008 May 27;363(1498):1849-55
references: 18267913
references: Nature. 2004 Sep 9;431(7005):181-4
references: 15356630
references: Science. 2003 Dec 5;302(5651):1719-23
references: 14657489
references: Nature. 2011 Aug 10;476(7359):160-1
references: 21833081