# The Net Influence of Drought on Grassland Productivity over the Past 50 Years
## 4 Conclusions  
In this paper, we assessed the influence of drought on grassland ecological system productivity under the background of climate change. Based on the literature, the design of different simulation experiment scenarios based on the Biome-BGC ecological process model were carried out to further analyze the characteristics of precipitation and temperature changes over the past 50 years and to pave the way for further analysis of the net effects of drought. The interaction of precipitation and temperature changes on drought effects was studied at a regional scale, and the net effect of drought on NPP was analyzed at point and regional scales. The results indicate the following:  
1. On the regional scale, the current pattern of climate change plays a negative role in the grassland productivity in Inner Mongolia, aggravating the influence of drought on the grassland ecosystem to some degree. It is mainly controlled by precipitation deficit, but the temperature interferes with the precipitation during drought significantly (\(p>0.05\)). The grassland productivity decreased slightly over the past 50 years under climate change, which reveals that the decreased impact of precipitation change is larger than the increased impact of temperature change on NPP. 2. From the analysis of the overall loss level of NPP caused by drought in grassland, the total change of NPP caused by a single factor of drought ranged from \(-1140.30\) to \(15,003.30\) gC/m\({}^{2}\)/\(52\)a over the past 50 years. Specifically, the regional average losses of meadow, typical, and desert steppes are \(7005.73\) gC/m\({}^{2}\)/\(52\)a, \(8466.10\) gC/m\({}^{2}\)/\(52\)a, and \(4753.25\) gC/m\({}^{2}\)/\(52\)a, respectively. As compared with the mixed influence of drought on grassland under the background of global change, the severity of the net impact of drought as a single factor on grassland NPP are as follows: typical grassland > meadow steppe > desert steppe. Therefore, climate change may, to a certain degree, complicate the impact of drought on grassland ecosystem productivity. * 3. The net influence of drought on the NPP of different types of grassland types is varied. The percentages of the study area where drought has caused severe NPP losses (the values of NPP change are greater than zero) are about 95.4%, 95.4%, and 95.4% for meadow, typical, and desert steppe, respectively, while the areas where the NPP increased (the values of NPP change are less than zero) are about 4.6%, 8.4%, and 63.2%, respectively. Therefore, climate change increases the complexity of influence on grassland productivity by drought to some extent. The analysis of our proposed method revealed that drought due to precipitation deficit and temperature change is the main factor that reduces grassland NPP, and the practical application in the Inner Mongolia grassland also verified the validity of our method. However, there are still some limitations in this study. First, only the effects of precipitation and temperature changes on the NPP of grasslands were considered in this study, and other factors such as weathering and topographical changes were not considered. Second, human activities such as grazing, population change, water utilization, and drought resistance may also have an impact on the NPP of grasslands. Third, we only considered 50 years of data variation and did not refine the time series, such as the effect of drought on grassland NPP under a 10-year span, 5-year span, 3-year spatial span, and a 1-year span. These are the focus of our future research. [PERSON], [PERSON] ([PERSON]) and [PERSON] ([PERSON]) designed the draft framework and wrote the initial draft; [PERSON], [PERSON], [PERSON] and [PERSON] revised the draft framework and contributed equally to this work, and should be considered co-first authors. All authors have read and agreed to the published version of the manuscript. This research received financial support from The Agricultural Science and Technology Innovation Program of Chinese Academy of Agricultural Sciences.