## 1 Introduction  
In view of the global climate system, the terrestrial carbon cycle in the context of increasing atmospheric CO\({}_{2}\) concentration and changing climate remains unclear [1; 2]. Central Asia, which lies in the interior of the Eurasian continent, covers Xinjiang Autonomous Region of China, Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan [3; 4]. The effect of climate change on the regional and interannual patterns of the terrestrial carbon dynamics have not been adequately quantified though it occupies vast land area (\(\sim\)5.6 million km\({}^{2}\)) and has potential importance and contribution to the global carbon cycle. An analysis of meteorological data has shown that the annual mean surface temperature over Central Asia increases at a mean decadal rate of 0.39 \({}^{\circ}\)C, which is larger than the average rate of 0.29 \({}^{\circ}\)C on the global scale [5]. Surface temperature trends are found to be highly inhomogeneous in space. The uncertainty in estimated tendencies for precipitation is considerably greater than that for surface temperature. [PERSON] and [PERSON] [6] reported that the regional amount of precipitation had slightly decreased during the past 50-60 years, whereas Xinjiang, China had increased by 7-16% from 1981 to 2007 [3]. The inhomogeneity of climate changes should predetermine a complex and ambiguous response of the carbon dynamics to these changes among different regions and vegetation species. Central Asia has four dominant vegetation types, namely, forest, cropland, shrubland, and grassland. The differences in water supply and nutrients among these types result in possible differences in biogeochemical processes and carbon dynamics. Therefore, different vegetation types are expected to respond differently to climate variability and change. As forests are considered to be a significant carbon sink under changing climate and occupy large fractions of global terrestrial carbon, their carbon dynamics are of great importance. Agroecosystem can be a large source of carbon emission in the consideration of many cropland practices [7]; however, cropland in Central Asia is classified as irrigated cropland and rainfed cropland, which could lead to different carbon dynamics arising [8]. Shrubland ecosystems are widely distributed in both arid and semi-arid regions, and their carbon uptake/release are controlled mainly by water availability [9; 10; 11]. Many prior works have shown that shrublands have different growth patterns distinguishing them from other vegetation types [12; 13]. Degradation of grassland is a predominant issue for Central Asia, and this can be attributed to climate change and grazing. Grazing alters grassland carbon stocks by stimulating regrowth of plant or just reducing above-ground biomass [14; 15]. Therefore, grassland carbon cycling is not only affected by climate variation, but also by human activity. It is a great challenge to study terrestrial carbon cycle through direct field observations. Inventory studies and carbon flux measurements are beneficial for evaluating the dynamics of ecosystem carbon storage for independent sites research; however, extrapolating to regional scales is considerably challenging [1]. Therefore, terrestrial ecosystem models have coupled the fundamental mechanisms in studying the interactions between climate change and carbon cycle. Among the existing terrestrial ecosystem models, biogeochemical models are the most important and widely used, such as Biome-BGC (BioGeochemical Model) [16], CENTURY [17], DeNitrification DeComposition (DNDC) [18], Dynamic Land Ecosystem Model (DLEM) [19], and Carnegie-Ames-Stanford Approach (CASA). Although the structure and function of these terrestrial ecosystem models have been improved, and most of them can be used to study regional or global carbon and nitrogen cycles, little attention has been paid to the processes of human activities, such as grazing processes and the effects of grazing on carbon and water cycles in ecosystems.