## 4 Discussion and Conclusions
### The Positive Effect of SISGC, Especially in the Western Semi-Desert Grassland Area  
Many researchers have tried to reveal and explore the change of grassland development, especially the degradation condition after the implementation of environmental conservation projects, such as the improvement of height, coverage, and biomass of natural grassland. However, results are often spatially and temporally inconsistent. Some studies showed that grassland condition has recovered to some extent in the past decades [24], while others claim that overall grassland condition has continued to deteriorate and grassland degradation is still the major ecological issue [25]. However, recent researches revealed that the year 2011 can be seen as a turning point for grassland dynamic trends in IMAR. By empirically analyzing the NDVI developing trend based on data of 52 counties across a 15-year timespan, results showed that there was a deteriorating trend between 2001 and 2010, followed by an improving trend since 2011 [44]. Studies of vegetation growth dynamics based on EVI since 2000 also reflected an obvious turning point in 2011 (Figure 3 in the reference research) showing a significant standard deviation in 2012 [45]. NDVI studies based on datasets of NASA's Earth Science Data Systems Programs from 2001 to 2014 also showed a visible increasing trend since 2011 (Figure 2 in the reference research) [24].  
Based on these studies, the SISGC implementation in 2011 seems to have positively contributed to local grassland conservation in IMAR. The continuous effects in the past ten years and the potential yearly adjustment for the SISGC seem more practically essential. We chose to use FVC and NPP as two main indicators for detection of grassland change in IMAR, using FVC to visualize grassland quantity and NPP to assess product quality. These two aspects are in line with the national standards of Peoples' Republic of China \"parameters for degradation, sandification and salification of rangelands (GB19377-2003)\" [46]. The indicators proved to be effective for appropriate grassland degradation monitoring in IMAR [17]. Our study results reflected the positive effects of grassland recovery since 2011. Both FVC and NPP showed an increasing trend (Section 3.1.2). [PERSON]'s research based on field survey data in IMAR also indicated that the aboveground NPP of different grassland types increased significantly between 2011 to 2013, in line with the progress of the national ecological program [47].  
Besides, our study shows that the positive effect since 2011 is spatially unbalanced. The grassland change trend classification (Figure 3) shows that most green pixels (increase) are concentrated in the western part of IMAR's grassland area, while most of the red pixels (decrease) are distributed in the upper eastern part. The grassland types in IMAR are desert sreppe, typical steppe, and meadow steppe [25] following a precipitation gradient from west to east. Thus, the increasing trend or the positive effect is more obvious in the western part with desert steppe than in the eastern part with typical and meadow steppe. For example, in Baotou, where semi-desert grasslands are characteristic, the combined NPP and FVC classification system indicates that 86.03% of grassland shows a fluctuating or a persistent increasing trend. However, in Hulunbuir, characterized by meadow and typical steppe, only 16.99% of grassland shows an increasing trend. The possible reason might be that semi-desert grassland with poor ecological conditions has a higher potential for improvement. However, the significantly lower increasing trend in typical and meadow grassland possibly reflects that these areas receive less attention.