Growth stages affect species richness and vegetation patterns of nebkhas in the desert steppes of China

Nebkhas are important indicators of land degradation in desert steppes and play an important role in the ecological and evolutionary dynamics of desert steppe ecosystems. This study examined the relationship between the diversity of plant species and nebkha morphology during different growth stages of the nebkhas. In this study, each nebkha is defined as a self-contained unit. The species composition and vegetation patterns within each unit during different stages of formation were investigated, while also the plant species within the internebkha area of the desert steppe field were examined. Results show that more than 90% of the species within the nebkha units were herbaceous. In developing nebkhas, the increase in nebkha size was associated with an increase in the herb species richness but a decrease in the overall plant density. When nebkha size was constant, similar correlations with species richness or density were found. The richness of species within the internebkha area was significantly higher compared to developing nebkhas during periods of growth, but lower when nebkha development was complete and growth hadstalled. The density of species was significantly higher in the nebkhas than the inter-nebkha area during all developmental periods. Thus, nebkhas provide a highly favorable condition for plant recruitment and survival when fully developed. However, when nebkhas are still forming, the inter-nebldia areas provide greater plant support. These results have important implications to biodiversity conservation in desert steppe fields. (C) 2015 Elsevier B.V. All rights reserved.