# Stronger Cumulative than Lagged Effects of Drought on Vegetation in Central Asia
## 3 Results
### Cumulative Effect of Drought on Vegetation GPP  
The space distribution patterns of vegetation GPP, the cumulative SPEI correlation (Rmax_cum), and its corresponding cumulative duration of months are illustrated in Figure 10. GPP of vegetation were positively and negatively correlated with SPEI in 92.66% and 7.34% of the regions in Central Asia, respectively, and 51.03% of the regions were significantly correlated (\(p<0.05\)). The spatial distribution of Rmax_cum showed heterogeneity, as shown in Figure 10a. Rmax_cum had a mean value of 0.33, and its values were mainly concentrated in the range of 0.20-0.50. High correlations (Rmax_cum > 0.6) were found in southern Kazakhstan, eastern Uzbekistan, southern Turkmenistan, and southwestern Tajikistan. Scattered throughout Central Asia, there was a lower correlation (Rmax_cum < 0.2). A negative correlation was mainly found in northern and eastern Kazakhstan, south-central Uzbekistan, northern Turkmenistan, southern Kyrgyzstan, and western and northern Xinjiang, China. Cumulative thoughts lasting 9-12 months covered 75.86% of Central Asia, as shown in Figure 10b, with the largest area (26.70%) occurring at the 10-month time scale, mainly in central, southern, and northeastern Kazakhstan, western Kyrgyzstan, northeastern Uzbekistan, and northern Xinjiang, China. This was followed by regions with 12 (19.94%) and 9 months of accumulation (15.15%). The shorter cumulative drought time scale (1-4 months) accounted for 13.59% of the vegetation, mainly in northern and eastern Kazakhstan, eastern Kyrgyzstan, and Xinjiang, China. The smallest proportion of the cumulative 2-month time scale was found mainly in the western and northern regions of Xinjiang, China. The responses of GPP to cumulative months of drought for different vegetation types are shown in Figure 10c, where the average number of cumulative months for vegetation was 9 months. Shrubland had the most cumulative months, with a mean of 10.65 months, followed by cropland (9.99 months), grassland (9.51 months), and forests (6.24 months). There was a significant difference between the percent area and the average value of Rmax_cum on different cumulative time scales, as shown in Figure 11. As shown in Figure 11a, the highest percentage of area, 92.76%, was found at 1 month of accumulation and when Rmax_cum was negatively correlated. Among the positive correlations, the highest percentage of the area was 22.37% at 4 months of accumulation when Rmax_cum was in the range of 0.25-0.30. Over the entire cumulative time scale of 1-12 months, the highest percentage area was observed for Rmax_cum of 0.30-0.35 (12.55%), followed by 0.35-0.40 (11.52%) and 0.25-0.30 (11.31%). There was a close correspondence between  
Figure 9: Relationship of annual mean SPEI with the (a) mean maximum correlation coefficient and (b) corresponding mean lagged months. vegetation GPP and cumulative SPEI except on the 1-month time scale. At 7-10 months, 2.96% of the vegetation had a Rmax_cum higher than 0.6. Figure 10: Distribution of the cumulative effect of drought on vegetation. (**a**) Characteristics of Rmax_cum spatial distribution of vegetation GPP and cumulative 1–12-month SPEI from 2000 to 2018. The blue areas indicate statistically significant correlations (\(p<0.05\)) and gray areas indicate statistically insignificant correlations (\(p>0.05\)); (**b**) Spatial distribution of cumulative months and percentage of area corresponding to Rmax_cum; (**c**) Distribution of cumulative months corresponding to Rmax_lag for different vegetation types. Figure 11b shows the mean Rmax_cum values for each vegetation type for a different number of cumulative months. From the vegetation overall, the average Rmax_cum value was the largest at 7 months of accumulation, 0.41, followed by 8 and 10 months of accumulation, with values of 0.39 and 0.38, respectively.