Responses of Nitraria sphaerocarpa Maxim. population to disturbance of blown sand in the edge of Desert Oasis
荒漠绿洲边缘区泡泡刺种群对风沙干扰的响应

Nitraria sphaerocarpa Maxim. is one of the major sand binding species in the sand lands, which mainly distributes in the arid and semi-arid area of China. The study was conducted to evaluate how the Nitraria sphaerocarpa Maxim. population responds to the disturbance of blown wind, and to establish the relationships between the depth of sand burial and the population height, coverage, density, size, and biomass, respectively. The results show as follows: Nitraria sphaerocarpa Maxim. population shows patchy and discontinuous distribution pattern. Sand burial makes the population relative independent shrub coppice dune. And the independent shrub coppice dunes can be formed by four ways, that is: 1) seedling reproduction; 2) sprouting reproduction; 3) habitat fragmentation; 4) combination of neighboring shrub coppice dunes. Water condition is one of the most important factors to control the growth of Nitraria sphaerocarpa Maxim. population, which has significant characters in size and spatial distribution, due to competing for the limited water resource. Except for the biomass, there are significant differences between population height, coverage, density, and size in Gobi and those of the population in the desert, respectively. The height, coverage, size, and biomass of the population in the desert are bigger than those in Gobi, however, the density of the population in desert is less than that in Gobi. The population height, density, size and biomass are significantly correlated with the depth of sand burial in Gobi, and the height, coverage, size and biomass are significantly correlated with the depth of the sand burial in the desert, respectively. Population height increases with increasing sand depth. Population coverage increases with increasing sand depth in desert. Also the density increases with increasing depth of sand burial in the desert, however, there is a steady decrease when the depth of sand burial is more than 100cm. The result illustrates that the depth of sand burial that is fittest for the growth of Nitraria sphaerocarpa Maxim. population is 100cm. In Gobi, the population density increases with increasing depth of sand burial. The size of the population is significantly correlated with the sand depth, which increases with increasing depth both in Gobi and the desert. The conclusion can be drawn that the characteristics of Nitraria sphaerocarpa Maxim. population are significantly correlated with the depth of sand burial due to the disturbance of blown wind and the limited water resource. Sand burial can improve its growth, however, when the depth of sand burial is more than 100cm, its growth will be gradually restrained.