DOI: 10.5061/dryad.pzgmsbcpm
title: NDVI-based monitoring of long-term vegetation dynamics and responses to multi-time scales droughts in Inner Mongolia

description: The characteristics of vegetation and drought for different seasons
 between 1982 and 2015 in Inner Mongolia were studied based on the
 Normalized Difference Vegetation Index (NDVI) and the Standardized
 Precipitation Evapotranspiration Index (SPEI). The response of vegetation
 to drought over various time scales for different seasons and vegetation
 types was investigated using the maximum Pearson correlation, allowing a
 discussion about the possible causes of any changes. The results indicate
 that the vegetation NDVI in Inner Mongolia showed an increasing trend in
 different seasons, with spring vegetation NDVI (April to May) having the
 largest significant increasing rate, followed by the growing season (April
 to October), autumn (September to October), and summer (June to August).
 Accordingly, the proportion of stations with decreasing SPEI was, in
 descending order, summer, growing season, autumn, and spring.
 Additionally, the magnitude of the SPEI decrease was greater in eastern
 Inner Mongolia. NDVI and SPEI were positively correlated in most regions
 of Inner Mongolia, indicating that changes in vegetation in most parts of
 this region were affected by the spatial and temporal characteristics of
 drought, the correlation being them being strongest in the growing season,
 followed by summer, then spring and autumn. Considering the different
 types of vegetation, forests were less affected by drought, with broadleaf
 forests more affected than coniferous forests. The meadow steppes and
 typical steppes were more affected by 12-month droughts in the growing
 season and summer, 6-month droughts in spring, and 3-month droughts in
 autumn, with desert steppes mainly affected by 3-month droughts. The
 shrubs, sandy vegetation, and cropland were mostly affected by droughts in
 summer, and show a greater response to 3-month droughts in autumn.
 Finally, the water balance was found to be the most important factor
 affecting the response of vegetation to drought in Inner Mongolia.
description: We upload two datasets used in the paper, including GIMMS NDVI3g
 and SPEI dataset during 1982-2015 in Inner Mongolia region.
 (1) To monitor
 the vegetation, the GIMMS (Global Inventory Modelling and
 Mapping Studies) NDVI3g datasets were used because of their high quality,
 with 0.083° and 15-day spatial and temporal resolution,
 respectively (download from https://ecocast.arc.nasa.gov). To
 reduce the effects of atmospheric and aerosol scattering, we used the
 maximum value composite (MVC) method to develop a monthly NDVI
 dataset.  Since the vegetation in Inner Mongolia shows minimal growth or
 is covered by snow in winter, the growing season (April to October) was
 selected for this study, with the other considered seasons defined as
 spring (April to May), summer (June to August), and autumn (September and
 October).  (2)  The SPEI (<em>Standardized
 Precipitation Evapotranspiration Index</em>), was selected to
 indicate drought in the paper. It is designed to consider both
 precipitation and potential evapotranspiration when identifying droughts.
 It also captures the main impact of increased temperature on water demand
 and can be calculated over a range of timescales, reflecting the duration
 and cumulative effects of droughts. The SPEI is therefore a widely used
 index for evaluating, monitoring, and assessing drought within the
 background of global warming. The calculation of SPEI please check in the
 paper.
description: N/A