Figure.8 Annual variations of different driving factors
Pearson’s coefficient and t -test were utilized to express the relevance between oasis transitions and driving factors in Figure 9. Among the natural driving factors, oasis transitions showed positive correlation with temperature (P -value < 0.05, r= 0.88) and insignificant correlation with precipitation. Temperature was positively related to forest (P -value < 0.01,r = 0.94) and shrubland changes (P -value < 0.01,r = 0.95). Notably, precipitation had negative effects (P -value < 0.05) on shrubland changes. It indicated that the most natural oasis changes in Tuha Basin was highly sensitive to temperature, and scarcely affected by precipitation due to the extremely low precipitation and its downward trend during 1990 and 2020 over Tuha Basin. Generally, natural factors mainly affected natural oasis with the average coefficient of 0.92 (P -value < 0.01), and had insignificant effects on artificial oasis.
All the human driving factors, population, total power of agricultural machinery, raw coal production, and total agricultural output showed positive correlations with the oasis changes, with the coefficients of 0.83, 0.94, 0.90 and 0.91 (P -value < 0.05), respectively. Cropland, shrubland and built-up changes were mainly controlled by human activities, and built-up had the most positive response to population, total agricultural machinery power, raw coal production, and agricultural output, with the coefficients of 0.93, 0.94, 0.96 and 0.98 (P -value < 0.01), respectively. Shrubland changes were influenced significantly by the total power of agricultural machinery, raw coal production, and agricultural output value, with the coefficients of 0.87, 0.89, and 0.87, respectively (P -value < 0.05). With the same coefficient of 0.89, human activities had obvious driving forces on both natural oasis and artificial oasis. Human activities mainly affected shrubland in natural oasis; the four human factors showed significant positive correlations on artificial oasis, with the coefficients of 0.86, 0.86, 0.85 and 0.89, respectively (P -value < 0.05). The spatial allocation of water resources improved with the development of agriculture and industry of Tuha Basin. Moreover, the policies supporting the shrub planting and growth were encouraged to combat desertification and reinforce sand.