干旱区生态环境知识资源中心

The composition and development of sandy land plant communities in arid and semiarid environments largely depend on rainfall pulses. However, little is known about how the intensity of small rainfall events affects the emergence and growth of annuals in spring. For this study, an experiment was designed to simulate the effect of low-intensity spring rainfall events on annuals in Horqin Sandy Land, China, in May of 2011 and 2012. It included rainfall treatments of 2 mm (applied 16 times), 4 mm (applied 8 times), and 8 mm (applied 4 times), and a control check (CK, which received natural rainfall). The soil water content, species composition, seed germination, plant density, height, and coverage, and aboveground biomass were measured. Results showed that rainfall intensity had a significant influence on the emergence and growth of annuals. A rainfall of 8 mm was the threshold for germination, whether as a single rainfall event or as accumulated rainfall. The 8-mm treatment also resulted in the greatest number of seedlings, while the 2-mm treatment provided the least. Community characteristics such as species number, density, and coverage increased with rainfall intensity; height and canopy decreased; the Shannon-Wiener index showed no obvious trend. The distribution of rain amount and frequency impacted biomass accumulation: with increased rainfall intensity and extended rainfall intervals, biomass was significantly increased compared to the control check.