Spatial Pattern Of Artemisia Ordosica Population At Different Stages Of Dunes In The Mu Us Desert

Artemisia ordosica is one of the most excellent sand fixation plants in arid semi-arid region of China, and it is also a constructive species of the Mu Us Desert. A. ordosica has a great significance in sand fixation, recovery and reconstruction of ecological system and biodiversity protection. However, little is known about the spatial patterns of A. ordosica. To explore its spatial pattern can further reveal the characteristics and the change law of the population patterns, which have great helpful to master evolutionary process of A. ordosica population. The aim of this study was to investigate and contrast the effects of sand dune stabilization on the population and spatial distribution of this desert shrub. Spatial autocorrelation, semi-variance analysis, and point-pattern analysis were used jointly in this study to investigate the spatial patterns of A. ordosica populations on dunes in Yanchi County of Ningxia, China. The results showed that:(1) Soil crust in sample plot increased gradually, the average crown decreased first and then increased, and the number of A. ordosica increased first and then decreased following sand dune fixation. And the adults number increased, the seedlings increased first and then decreased. The age structure of the population turned seedling as the main body to older, and the population from growing into a recession as the sand fixation.(2) The spatial autocorrelation and spatial heterogeneity declined gradually, the range of spatial autocorrelation decreases, and the distance between the clustered individuals shortened following sand dune fixation. This result means population pattern distribution characteristics consistent with the characteristics of spatial autocorrelation.(3) There is a significant differences in spatial distribution pattern and the relationship between the different age of A. ordosica. Seedlings were more aggregated than adults in all stage of dune stabilization, and both were more aggregated on shifting sand dunes separately. Spatial associations of the seedlings with the adults were mostly positive in shifting sand dunes, and the spatial association changed from positive to neutral in semi-fixed sand dunes. The seedlings were spaced in an almost random pattern around the adults, and their distances from the adults did not seem to affect their locations in semi-fixed sand dunes. Furthermore, spatial associations of the seedlings with the adults were negative in the fixed sand dune.These findings demonstrate that sand stabilization is an important factor affecting the spatial patterns and the vegetation growth state of A. ordosica populations in the Mu Us desert. Sand dune stabilization can change the spatial pattern of shrub population by weakening the spatial association between native shrub individuals, which may affect the development direction of desert shrubs. This paper in-depth exploration in population patterns of different fixed sand dune stage combining with the spatial autocorrelation, semi-variance analysis, and point-pattern analysis, to fully disclose spatial distribution strategy and pattern change rule of A. ordosica populations of different fixed sand dune stage.