Vegetos

Abstract

Sand dunes are widely distributed in Gurbantunggut Desert, which is the biggest fixed/semi-fixed desert in China and exhibits obviously seasonal climate. Vegetation is considered as a key factor to fix sand dunes. Herbaceous plants contribute the most richness and diversity in desert floristics. Thus, exploring the seasonal variations in herbaceous species composition and spatial distribution on dunes will further help us understand the structure and dynamics of herbaceous communities and the mechanism of dune stability. The floristics, life-form, density, richness and coverage were surveyed from 214 plots (5 m×5 m) across two linear dunes (220 m×110 m) in spring, summer and autumn, 2010. The results showed that there were two (27), four (35) and two (8) life-forms (species) in spring, summer and autumn, respectively. There were the highest values of richness, density and coverage in summer but lowest in autumn. Density and coverage both showed clumped distribution in three seasons, but the aggregating intensities were different. The values of density and coverage at lower part of dune were higher than that at upper part in spring and summer, while they showed the opposite tendency in autumn. Density and coverage both demonstrated moderately spatially dependent with ranges from 18.5 m to 33.5 m in three seasons; and the ranges were similar to the average width of slope positions (31.4 m). In conclusion, the herbaceous composition and distribution on dunes presented obviously seasonal changes, which could reduced the competition among life-forms with different vegetative periods and improved the stability of desert ecosystem.