Shapotou (37°27′N, 104°57′E) is located in the southeast of Tegger Desert, Zhongwei County, Ningxia Hui Autonomous Region of China. The average annual precipitation is ca.186 mm (mainly in summer), evaporation more than 2900 mm. The windy days (>5 m/s) are more than 200 days each year. Forty five years ago there was only shifting sand dunes. Since 1956 drought-resistant trees are batch planted each several years under irrigation and non-irrigation conditions. Now the stable algal crusts had formed on the to...