China’s deserts greening and response to climate variability and human activities

The Qaidam Basin Desert (1.25%) showed the highest proportion of browning, followed by the Taklimakan Desert (0.84%) and the Kubuqi Desert (0.67%). Greening and browning trends indicated by the seasonal NDVI. The greening and browning trends were calculated by the Theil-Sen estimator and Mann-Kendall test using the seasonal NDVI in desert areas from 2000 to 2017 (Fig 5) and the statistics are shown in Table 2. The spatial distribution of the greening and browning trends had obvious seasonal dif- ferences. In spring and winter, there was little spatial difference among the deserts, and the areas showed approximately the same degree of greening. The proportion of greening areas in spring was 73.05%, the highest among the seasons. However, the degree of the greening of NDVI in autumn was higher than that in spring, and the greening trends increased on the southern edge of the Gurbantunggut Desert, in the northwestern part of the Taklimakan Fig 5. Spatial distribution of greening and browning trends for spring (a), summer (b), autumn (c), and winter (d) in China’s desert areas from 2000 to 2017. Gray areas represent desert regions with no significant trends at the 5% confidence level. The green and brown areas indicate that the pixel has a significant greening and browning trend, respectively. https://doi.org/10.1371/journal.pone.0256462.g005 Table 2. Proportion of the area for seasonal NDVI trends. Season Significant Increase (%) Increase but not significant (%) Significant decrease (%) Decrease but not significant (%) Spring 73.05 22.30 0.76 3.89

Summer 69.37 25.95 0.96 3.72 Autumn 44.93 46.02 1.14 7.91 Winter 56.49 35.34 0.86 7.30 https://doi.org/10.1371/journal.pone.0256462.t002 PLOS ONE China’s deserts greening and response to climate variability and human activities PLOS ONE | https://doi.org/10.1371/journal.pone.0256462 August 30, 2021 9 / 20