# The Net Influence of Drought on Grassland Productivity over the Past 50 Years
## 2 Materials and Methods  
### Study Area and Data  
The Inner Mongolia grassland is the main area of temperate grassland in China, in the region of 97\({}^{\circ}\)12\({}^{\prime}\)-126\({}^{\circ}\)04\({}^{\prime}\) E and 37\({}^{\circ}\)24\({}^{\prime}\)-53\({}^{\circ}\)23\({}^{\prime}\) N. The plateau is the primary topography in the research area, constituted by the Hulun buit plateau, Xilingol plateau, and Ordos plateau. The temperature decreases from southwest to northeast, and precipitation increases from southwest to northeast, as a typical temperate continental monsoon climate [35]. The average annual temperature is from \(-5\) to 9 \({}^{\circ}\)C, while the annual precipitation is from 150 to 500 mm [36]. From the east to the west, three grassland types, namely meadow grassland, typical grassland, and desert grassland appropriating the soil types as Chernozem, chestnut soil, and brown soil, are distributed in the study area (Figure 1) [37]. The meadow steppe is concentrated in the subhumid area at the base of the Greater Hinggan mountains, dominated by perennial xerophytes and mesophytes, such as _Stipa bialensis_, _Filifolium sibiricum_, and _Leymus_; the typical steppe is mainly composed of xerophytic perennial herbaceous plants, with the dominant types being _Leymus_ and _S. bungeana_; the desert steppe is mainly composed of xerophytic perennial dwarf herbaceous plants with the dominant types being _S. klemenzii_, _S. glareosa_, and _S. breviflora_.  
The China Meteorological Data Sharing Network provides meteorological data for the past 50 years (1961-2009) from six stations in the study area ([[http://cdc.cma.gov.cn](http://cdc.cma.gov.cn)]([http://cdc.cma.gov.cn](http://cdc.cma.gov.cn)), accessed on 29 April 2022). At the same time, the grid daily data from 1961 to 2012 was used to build a Biome-BGC model, and the monthly data from 1961 to 2012 were used to build the SPI drought monitoring index. Daily maximum temperature, daily minimum temperature, daily average temperature, daily total rainfall, and daytime length data were included. The MTCLI model was used to simulate the average water vapor pressure and the average short wave radiation flux density. Monthly rainfall data were used in the calculation of SPI. In the study area, the distribution of vegetation types, at a scale of 1:1,000,000, was obtained from the China Vegetation Type Map Editorial Committee  
Figure 1: The distribution of the Inner Mongolia temperate grassland.  
([[http://www.geodata.cn](http://www.geodata.cn)]([http://www.geodata.cn](http://www.geodata.cn)), accessed on 29 April 2022). Soil data including sand, silt, and clay content and depth data were obtained from the International Soil Reference and Information Center (ISRIC, [[http://www.isric.org](http://www.isric.org)]([http://www.isric.org](http://www.isric.org)), accessed on 29 April 2022). Nitrogen deposition data and CO\({}_{2}\) data were obtained from the UK Air Pollution Information System (APIS: [[http://www.apis.ac.uk](http://www.apis.ac.uk)]([http://www.apis.ac.uk](http://www.apis.ac.uk)), accessed on 29 April 2022) and Pro Oxygen from the Mauna Loa Observatory/NASA, Hawaii ([[http://www.co2](http://www.co2) now.org]([http://www.co2](http://www.co2) now.org), accessed on 29 April 2022), respectively [38].