## 4 Discussion and Conclusions
### Potential Threats and Possible Reasons: Social and Natural Effects on Grassland Change  
From 2011 to 2019, the annual average precipitation in IMAR increased from 110.39 mm to 120.00 mm; The annual average temperature also increased from 3.78 \({}^{\circ}\)C to 5.02 \({}^{\circ}\)C (See supplement file, Table S1). These positive climatic factors for grassland productionresult in an increase of PNPP (See Formula (3), Section 2.3.2). However, HNPP also shows an increasing trend (Section 3.1.2), implicating the intensity of human activities. Spatially, the annual average precipitation decreases from east to west of IMAR (See supplement file, Figure S1). The analysis of spatial-temporal precipitation change, based on available data from 2010 to 2015 in a 1 km spatial resolution (See supplement file, Figure S2), shows an increasing trend of precipitation in the eastern part, where typical and meadow steppe dominated. Improving natural climatic conditions will most probably improve grassland production in these areas. However, the grassland classification results show a decreasing trend in most of these areas (Figure 3). The contrasting results are alarming for the implementation of the grassland conservation program. The additional increase of PNPP and NPP in the whole region might cover up the negative effects, especially in areas under better precipitation conditions.  
Considering SISGC implementation, [PERSON]'s field survey in 2015 revealed that SISGC had limited impact on herders' livestock production and grazing management, especially for herders in good grassland regions [48]. The compensation is much lower compared to possible market benefits and seems to be less attractive, although the subsidy and reward from central government on SISGC in IMAR are approximately 3.2 billion USD for the first round (2011-2015) [48]. Statistical data shows that stocking livestock in IMAR increased from 68.06 million to 91.92 million between 2011 and 2019 [43]. A household survey research also revealed that the overall stocking rate marginally increased significantly [49]. Herders were found to be more sensitive to market signals rather than the subsidy [48]. Local government encountered increasing supervision costs when the producer price of live sheep soared, which prompted local herders to gain more economic benefits by increasing illegal grazing [24]. The difficult tasks for local government may also lead to the malfunction of SISGC implementation to some extent. Some researchers have pointed out that the determination of a maximum stocking rate and various grazing bans have a less feasible effect under the spatial heterogeneity of grasslands and climate variability [50], and the effectiveness of conservation strategies in arid and semi-arid areas need to be discussed thoroughly [51]. Integrated management considering climate conditions, geographical characteristics and socioeconomic factors is prospected to be beneficial for regional grassland conservation [52].  
The grassland ecosystems are ecologically vulnerable and sensitive to climate change [53]. Vegetation phenology in temperate grasslands is highly sensitive [54]. [PERSON] et al. observed that the length of the growing season in grassland regions of IMAR has increased by 10.86 days from 2002 to 2014 [21]. [PERSON] et al. also revealed that during 2000 to 2015, the start of the growing season in typical steppe and desert stepe has significantly advanced by 2.2 days and 10.6 days, and the end of the growing season in desert steppe has also significantly advanced by 6.8 days [54]. Combining the phenology changing results under the background of unavoidable global climate change could help to guide grazing systems and to develop more efficient policy frameworks for grassland protection.