Studying the influence of precipitation patterns on plant community diversity, soil C:N:P ecological stoichiometric characteristics, and the relationships between key soil factors and plant community diversity is of great significance for the protection of plant community diversity in desert grasslands. This paper was studied in the desert steppe of the west of Loess Plateau using a three-year precipitation manipulation experiment (40% reduction in precipitation, 20% reduction in precipitation, natural precipitation, 20% increase in precipitation, and 40% increase in precipitation), explored the influence of changes in precipitation in dry and wet years on the diversity of plant community and soil C:N:P ecological stoichiometric characteristics. And we also explored the relationship between soil C:N:P ecological stoichiometric characteristics and the key soil factors and the diversity of plant community under changes in precipitation. The results showed that in a normal year and the drier year (2013 and 2015), Patrick richness and Shannon-Wiener diversity index were significantly low under the 20% reduction treatment compared with the control and 40% increase treatments, respectively. During the wetter year, Patrick richness and Shannon-Wiener diversity index were no different between any of the precipitation treatments. In the normal year and the drier year, the soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) contents and the carbon-nitrogen ratio (C:N), carbon-phosphorus ratio (C:P), and nitrogen-phosphorus ratio (N:P) all decreased with an increase in precipitation (the decrease in the C:N ratio was statistically significant). During the wetter year, SOC, TN, C:P, and N:P increased with an increase in precipitation. During the normal year, precipitation treatments had no significant influence on soil water content, having a limited influence on the plant community. TN, N:P, SOC, C:N, and microbial biomass nitrogen (MBN) had a more prominent influence on plant community diversity. In the wetter year, precipitation was abundant leading to a rise in soil nutrients. Water was not the most important factor limiting to plant growth whereas soil water content, soil nutrients, and ecological stoichiometric characteristics jointly regulate plant community diversity. In the drier years, precipitation treatments had a significant impact on soil water content, whereby an increase in precipitation led to high losses of soil nutrients. Therefore, soil water content was the most important factor affecting plant community diversity during drier years. These observations indicate that under dry and wet years, plant community diversity and soil C:N:P ecological stoichiometric characteristics have variable responses to precipitation and soil C:N:P effect on plant community were also different. These results provide a theoretical basis for the protection and management of desert steppe systems under future projected changes in precipitation.
Keywords: change of precipitation; desert grassland; plant community diversity; soil C:N:P; wet and dry years.