关键词: 羊草种群, 能量分配, 生长和生殖

Abstract: In arid and semi-arid areas with sparse vegetation cover,the spatial pattern of surface soil had a definite effect on soil salinity and nutrient flow,which is of highly importance for understanding the processes of land cover change.In this paper,a total of 3 shrub types and 2 soil sampling depths (0～20 and 20～40 cm) in the arid area of oasisdesert transition belt were selected to assess the spatial heterogeneity of soil resources under shrubs.The results showed that different types of shrub had no significant effect on the particle size distribution of soil which was mainly composed of sand and silt,but significant cluster effect was observed under Tamarix ramosissima+ bare land shrub.Soils under shrub canopy had significantly higher contents of organic matter,total N and available K,compared to those in open spaces,and presented obvious “fertile island” phenomenon.Shrub types had significant effects on soil salinity,and different cluster effect existed in soils under different shrubs.The heterogeneity of soil resources resulted from a large number of factors,including climate,soil environment,height and extent of shrub canopy,stemflow,existance of other ground cover plants,and so on,many of which were mutually interactive.

Key words: Leymus chinensis population, Energy allocation, Growth and reproduction