# The Net Influence of Drought on Grassland Productivity over the Past 50 Years
## 3 Results and Discussion
### The Net Influence on Regional Grassland Productivity of Drought over the Past Five Decades  
From the analysis of the overall level of loss over the past 50 years, the total NPP losses in Inner Mongolia caused by drought ranged from 1140.30 to 15,003.30 gC/m\({}^{2}\)/52a, especially the NPP of typical steppe loss was most seriously. Overall, for 72.9% of the regions in Inner Mongolia grassland, there were large NPP losses caused by drought, which was almost distributed over the east and southeast meadow grassland, middle and northeast typical grassland, and eastern desert grassland. There was only 27.1% of the regions where the NPP increased, which were mainly distributed over the western desert grassland. Figure 8 shows that the influence on grassland productivity of drought had spatial heterogeneity. This spatial difference may result from the sensitivity of dynamic interannual variations of grassland on climate and biomass, and a lack of understanding of the response of the climate and atmospheric composition change in the regional grassland ecosystem process [46; 47; 48]. Climate change interferes, to some extent, with the influence of drought on a grassland ecosystem, which makes the influence of drought on a grassland ecosystem more complicated. Figure 13 indicates that, over the past 50 years, the regional average net impact of drought on the NPP in the meadow, typical, and desert steppe were 7005.73, 8466.10, and 4753.25 gC/m\({}^{2}\)/52a, respectively. As compared with the mixed impact of drought on grassland under the global climate change, the typical grassland NPP losses were the most serious, the meadow steppe losses were less than typical grassland, and the desert grassland had the least NPP losses. The net impact of drought on grassland productivity changed along the gradient of meadow steppe, typical steppe, and desert grassland, presenting the \"two head low, middle high\" phenomenon. Other scholars have also found that climate change significantly changed the pattern of drought on grassland productivity [43]. Therefore, to investigate the net impact of drought on grassland productivity, the interference of climate change factors on drought influence needs to be eliminated. Figure 12: Mean annual NPP under CLM experiment for the dry, wet, and normal years based on drought intensity data (* indicates that the 0.05 significance level test has been passed, and 0 indicates the standard). Figure 13: Total NPP losses for different grassland types caused by droughts over the past 50 years. It is shown in Figure 14 that there was a large difference in the net response to drought on the NPP of different grassland types. For the meadow steppe, the areas where the NPP had large losses (NPP change great than zero) accounted for about 95.4%, which were mainly distributed in the north, middle, and west of the meadow steppe. The areas where the NPP increased in the northeast and southeast areas accounted for only 4.6% (NPP change less than zero). Regarding the distribution of drought frequency, intensity, and duration, it was severe in the northern, middle, and western parts of the meadow steepe, while in the northeast and southeast areas, it was relatively slight. For the typical steppe, the area where the NPP had large losses accounted for about 91.6%, and it was mainly distributed over the middle and south of the typical steppe. The area where the NPP increased in the northwest, southwest, and northeast areas accounted for only 8.4%. The frequency, intensity, and duration of drought were also relatively severe in the central, southern, and northeastern areas, and relatively mild in the southeast area. For the desert steppe, the area where the NPP had large losses accounted for about 36.8%, and it was mainly distributed over the northeast and southeast of the desert steppe. The area where the NPP increased in the western area accounted for 63.2% There was a severe drought that occurred in the northeastern and southeastern desert steppe, while in the western area, drought was slight.