关键词: 营养盐分布, 富营养化, 东海, 赤潮

Abstract: Ephemeral plants are a special type of plants living in an environment which is rainy in early spring and xerothermic in summer.  In Gurbantunggut Desert, they  are mainly distributed in the southern part, playing an important role in the maintenance of desert ecosystem stability and in sandfixation. However, few studies have been done on their community diversity, ecological function, and spatial distribution. By adopting stratification sampling, this paper investigated the diversity feature of ephemeral plants at 35 sites covering a total area of 3.86×10⁴ m² in the southern Gurbantunggut Desert. A total of 93 ephemeral species were recorded, belonging to 24 families and 74 genera, among which, Chenopodiaceae, Compositae, Cruciferae, and Leguminosae were the dominant families, accounting for 19.35%, 17.20%, 11.83%, and 9.68% of the total species, respectively. In terms of life form, ephemeral plants, annuals with long period of nourishment, and trees and shrubs accounted for 53.76%, 22.58%, and 16.13%, respectively. In terms of importance value, ephemeral plants accounted for 45.73%, while trees and shrubs accounted for 30.93%. Ephemeral plants had a distinct spatial differentiation. Their species number and importance value increased obviously with longitude (from west to east), but decreased with latitude (from south to north). Oppositely, annuals with long period of nourishment and trees and shrubs had a decreasing importance value with longitude (from west to east), and their importance value increased with latitude (from south to north) but species number had no distinct change with latitude. Detrended canonical correspondence analysis (DCCA) showed that the species distribution was greatly affected by slope position, longitude and latitude, annual precipitation, and the precipitation from March to May. Based on two-way indicator species analysis (TWINSPAN), the ephemeral plants in southern Gurbantunggut Desert were divided into seven communities. It was considered that, with the increase of the precipitation in Gurbantunggut Desert, the importance value and species number of ephemeral plants tended to increase, but the density of dominant species Haloxylon persicum would be decreased gradually.

Key words: Nutrient distribution, Eutrophication, East China Sea, Red tide