Abstract:

Rainfall and atmospheric dryness play an important role in plant growth, especially in arid area. The herbaceous layer is an important component of the plant community in the Gurbantunggut Desert, China, and it generally depends on snow melt water in early spring for germination and development, resultant with a short life span. However, few studies focused on the relationship between the growth of desert annual herbaceous plants and rainfall and atmospheric dryness. Therefore, our objectives were to determine how snow cover, precipitation and atmospheric dryness affected the ecological traits of the herbaceous plants in this typical arid zone. From 2009 to 2016,we applied four treatments of snow cover thickness (0,50%,100%,and 200% as well as 100% natural snow cover thickness) to investigate the species richness and density in 1 m ×1 m quadrats. The meteorological data and field data were used to analyze the relationship between the growth of desert annual herbaceous plants and rainfall and atmospheric dryness. It was found that thick snow cover could result in a high topsoil moisture content and then high seedling density. Although the snow cover regulated the seedling density, there was no significant difference between species richness and snow cover thickness within a year. During the period of 2009-2016,however,the species richness fluctuated inter annually. It was inferred through the analysis of meteorological data that the species richness was mainly regulated by the rainfall during the seedling construction period. Moreover, the species richness in wet year would return to the normal level after a drought year. Vapor pressure deficit (VPD) of the atmosphere reflected the degree of atmospheric dryness, and there was a significant negative correlation between the number of survival herbaceous plants and VPD under the 100% snow cover treatment from 2009 to 2016,with the R² value at 0.611 (P<0.05).There was an opposite trend between the number of survival herbaceous plants and rainfall in growing season with R² at 0.162 (P>0.05).Obviously, atmospheric dryness was more likely to determine the survival of herbaceous plants.

Key words: desert plant')">

desert plant, plant quantity, rainfall, atmospheric dryness, meteorological factor, Gurbantunggut Desert