[Effects of long-term rainfall addition on the morphological characteristics and point pattern of desert plants]

Studying the effects of rainfall change on morphological characteristics, spatial pattern and spatial correlation of desert dominant plants could help to predict the response of desert ecosystem to global climate change. We conducted a 10-year simulated rainfall addition experiment and examined the morphological characteristics, spatial pattern and spatial correlation of typical desert plant species, Nitraria tangutorum and Artemisia ordosica, under long-term simulated rainfall enhancement conditions in Ulanbuh desert, using Programita software, Ripley's K function, and Monte Carlo method. The results showed that there were significant differences in the number, height, average crown and base diameter of the desert plants under different treatments. The number, height, average crown and base diameter of N. tangutorum and A. ordosica were significantly larger than CK, all of which increased with the amount of rainfall. When the amount of rainfall addition was less than 72 mm, the branch of N. tangutorum showed cluster distribution. When it was larger than 72 mm, it showed a tendency to decrease the aggregation intensity with rainfall increasing. The spatial distribution of A. ordosica population was characterized by random distribution-cluster distribution-random distribution pattern with rainfall increasing. In terms of spatial association, branch of N. tangutorum and A. ordosica showed negative correlation under control, but no correlation or positive correlation with rainfall increasing. When the amount of rainfall increased to 144 mm, the spatial association between two species changed from negative to positive. Under the scenario of increasing rainfall, soil moisture was improved, which would lead to a positive correlation between species and be more conducive to the coexistence and growth of N. tangutorum and A. ordosica.