Abstract:

The desert steppe ecosystem plays a crucial role in maintaining ecological balance and preventing land degradation， but its vulnerability makes it highly susceptible to human activities such as grazing. Plants acquire and allocate resources from the soil， which is essential for their growth and reproduction. However， research on the effects of soil nutrient content and stoichiometry among different grazing conditions on plant reproductive traits is still limited. This study conducted long-term experiments with three different grazing intensities （e.g.， no-grazing， moderate grazing， and heavy grazing） in Inner Mongolia to explore how grazing intensity affects the soil stoichiometry and reproductive traits of the dominant species of the desert steppe， Reaumuria soongorica. The results demonstrated that： （1） Grazing significantly affects soil nutrient content and stoichiometry， promoting the accumulation of total carbon （TC） and total nitrogen （TN） while reducing total phosphorus （TP） levels. Moderate grazing can adjust the C∶N on the soil surface. With increasing grazing intensity， the soil C∶N， C∶P， and N∶P showed an upward trend， impacting shrubs’ nutrients absorption and utilization. （2） The soil C∶N has been recognized as a critical factor influencing plant reproduction. The decomposition of organic matter in R. soongorica may be limited by phosphorus， and its growth and reproduction are more limited by nitrogen. （3） Grazing influences the growth and reproduction of R. soongorica shrubs by affecting soil nutrients contents and stoichiometry. In response to grazing， R. soongorica reduced seed quantity but enhance seed quality. Grazing significantly reducing the mean number of seeds， while increasing the hundred-grain weight， seed-setting rate， and female fitness. Our study provided important scientific basis for the protection of the Yellow River Basin and the desert grassland degradation and restoration.

Key words: grazing intensity, soil stoichiometric, reproduction traits, female fitness