# The Net Influence of Drought on Grassland Productivity over the Past 50 Years
## 3 Results and Discussion
### The Interaction of Precipitation and Temperature on Grassland Productivity  
Through different scenario simulation tests, we researched the average trend of productivity change in the Inner Mongolia grassland regions over the past five decades, as shown in Figure 8. There was no significant trend in the average NPP in the Inner Mongolia grassland regions over the past 50 years (\(p>0.05\)). Over the past 50 years, the regional average NPP did not present significant change (R\({}^{2}<0.05\)). Under the current pattern of climate change, the regional average NPP was 211.33 gC/m\({}^{2}\)/yr in 1961, and it increased to 366.93 gC/m\({}^{2}\)/yr in 2012, with the change value of \(-4.73\) gC/m\({}^{2}\)/10a, shown in Figure 5b. It demonstrated that the pattern of climate change had a slightly negative influence on grass  
Figure 7: Annual mean precipitation, temperature, and their changing trends in Inner Mongolia over thepast 50 years: (**a**) Average annual precipitation; (**b**) change rate of annual precipitation; (**c**) annual mean temperature; (**d**) change rate of annual mean temperature. land productivity in Inner Mongolia. In the scenario of PREC (only precipitation change), the regional average NPP also did not present a significant change trend (R\({}^{2}<0.05\)). The regional average NPP was 278.88 gC/m\({}^{2}\)/yr in 1961, and it increased to 343.83 gC/m\({}^{2}\)/yr in 2012, with the change value of \(-6.17\) gC/m\({}^{2}\)/10a, as shown in Figure 8c. It was found that the pattern of precipitation changes also had a slightly negative influence on grassland productivity in Inner Mongolia. However, in the scenario of TEMP (only temperature change), the regional average NPP increased significantly (R\({}^{2}<0.05\)). The regional average NPP average value was 228.48 gC/m\({}^{2}\)/yr in 1961, and it increased to 235.12 gC/m\({}^{2}\)/yr in 2012, with the change value of 0.59 gC/m\({}^{2}\)/10a, as shown in the Figure 8d. This showed that the pattern of temperature change had a positive influence on grassland productivity in Inner Mongolia. Grassland productivity over the past 50 years decreased slightly under the current climate change, indicating that the influence of precipitation change was greater than that of temperature change on the NPP. Therefore, the current pattern of climate change harmed Inner Mongolia grassland productivity, which may have exacerbated the effect of drought on the grassland ecosystem to some degree. However, the role of current climate change in altering the response of grassland NPP to drought cannot be ignored, as shown in Figures 9 and 10. Precipitation and temperature changes had a significant interactive effect on grassland NPP (\(p<0.05\)), and the regional NPP mean for grassland productivity in Inner Mongolia over the past 50 years ranged from \(-207.51\) in 1961 to \(-212.02\) gC/m\({}^{2}\)/yr in 2012, with a trend of \(-1.96\)/10a. Therefore, when assessing the net effect of drought on grassland ecosystems, it is important to consider the current disturbances from climate change (precipitation and temperature changes). At the same time, from the above, there is a significant decrease (\(p<0.05\)) in the effect of  
Figure 8: Interannual variations in NPP under the changing climate (CLM), precipitation only (PREC), and temperature only (TEMP) experiments. (**a**) Aggregate graph of results; (**b**) Interannual variations in NPP under the changing climate (CLM); (**c**) Interannual variations in NPP under the precipitation only (PREC), and (**d**) Interannual variations in NPP under the temperature only (TEMP) experiments. drought on grassland NPP over the past 50 years, but the effect of drought on regional NPP is decreasing significantly (\(y<0.05\)) with a trend of \(-7.44/10\)a from \(71.37\) in 1961 to \(41.81\) gC/m\({}^{2}\)/yr in 2012. This suggests that the negative effect of drought on grassland productivity has been diminishing and the promoting effect has been increasing in the past 50 years.