Abstract: In the mid-1980s,grasslands owned by the state were contracted to families for 30 to 50 years,and then increased livestock populations imposed heavy grazing pressure on Seriphidium transillense(Poljak.) Poljak.desert grasslands.Three sites with different degradation degrees were chosen on the northern slopes in Tianshan Mountains in western China to analyze the characteristics of plant populations,soil properties,and their relationships with different degradation stages.The results demonstrate that the dominant species shifted away from S.transillense into Petrosimonia sibirica(Pall.) Bunge which adopted r-strategy to produce innumerable seeds and then formed large population and consequently protected the grassland from completely collapse.The frequency,cover,yield,and density of S.transillense gradually decreased while P.sibirica increased and the feeding value of grassland became worse along with the degradation degrees.The compositional shift towards smaller,unpalatable and more ephemeral species was indicative of grassland degradation.The degradation of grassland vegetation was not in accordance with soil degradation.The surface soil had a trend of becoming coarse with the degraded degrees;however,the soil organic matter and total nitrogen steadily increased and reached the climax in over-degradation areas where the dung accumulation was the main reason for high soil nutrient content.

Key words: Seriphidium transillense(Poljak.) Poljak.desert, Degraded grassland, Soil properties, Vegetation characteristics, Northern Tianshan Mountains

摘要： 对天山北坡不同退化阶段伊犁绢蒿(Seriphidium transillense(Poljak.)Poljak.)荒漠草地植被特征和土壤特性进行分析,以期为该地区的草地恢复提供理论依据.结果表明:随着草地退化程度的加剧,伊犁绢蒿荒漠的优势种逐渐被叉毛蓬(Petrosimonia sibirica(Pall.)Bunge)替代;地带性植被伊犁绢蒿的频度、盖度、生物量和密度随着草地退化程度的加剧逐渐降低,而叉毛蓬却呈相反趋势;叉毛蓬种群在扩繁时采用"r"对策,产生大量种子迅速占领领地,阻止了草地的完全崩溃.随着伊犁绢蒿荒漠退化,草地的饲用价值劣化,草地植物种类向低矮、适口性差、短命和类短命植物过度.草地的植被退化与土壤退化不完全一致,随着草地退化,土壤表层颗粒有变粗趋势,然而土壤有机质和全氮却呈现稳定升高的趋势;极度退化地区的高养分含量主要是由家畜排泄物导致.

关键词: 伊犁绢蒿荒漠, 特征分析, 土壤特性, 植被特征