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

- We quantify the relationship between species richness, density and nebkhas size.
- We investigate species richness and composition in nebkhas and adjacent habitat in different nebkha growth stages.
- Total species richness increased and densities of species decreased with an increase in nebkha area.
- Nebkhas provide more favorable conditions for plants during nebkha stabilizing stage.
- Inter-nebkha areas are more favorable for plants during nebkha growing stage.

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 inter-nebkha 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 inter-nebkha area was significantly higher compared to developing nebkhas during periods of growth, but lower when nebkha development was complete and growth had stalled. 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-nebkha areas provide greater plant support. These results have important implications to biodiversity conservation in desert steppe fields.