Abstract:

Based on the method of replacing time series with spatial sequence, the study explored changes of plant biomass and species diversity during degradation process of typical peatlands and swamp meadows in Gahai wetland area, Gansu province. The results showed that the above ground and below ground biomass significantly decreased at the degradation process of wetland in 2 types of wetlands, but the below ground biomass had a more significant reduction, and the proportional coefficient of below ground and above ground biomass gradually decreased. The plant community features in 2 types of wetlands obviously changed. Namely, Carex meyeriana, the dominant plant in the non-degraded peatland,was replaced by Equisetum arvense in the degraded peatlands; Kobresia tibetica, the dominant plant in the non-degraded swamp meadows, was replaced by Carex meyeriana and Artemisia sacrorum.var messerschmidtiana in the light and moderate degraded meadows, respectively. A little Artemisia frigida Willd. and Polygonum viviparum were found in highly degraded steppe. With the degradation process of Gahai wetland, the hygrophytes decreased and the mesophytes and xerophytes increased. The richness index and diversity index increased with the degradation of the peatlands, however, they firstly increased and then decreased with the degradation of the swamp meadow. Evenness index showed a contrary trend. Similarity coefficient of communities decreased gradually in the process of Gahai wetland degradation. Therefore, it indicated that the degradation succession of species diversity of plant communities in Gahai wetland changed from original to weedy communities. Therefore, we should reduce the pressure of grazing and take artificial measures to restore ecosystem function of Gahai wetland.

Key words: Gahai wetland in Gansu province, Degradation degrees, Plant biomass, Species diversity

摘要：

以尕海湿地区内的典型沼泽泥炭和沼泽化草甸为研究对象，采用空间序列代替时间序列的方法，研究了尕海湿地退化过程中植物生物量及物种多样性的变化特征。结果表明：在尕海湿地退化过程中，湿地的地上、地下生物量均显著降低，但地下生物量降低幅度较大，地下、地上生物量比例系数呈减小趋势；尕海湿地退化过程中植物群落特征发生明显变化，具体表现为，泥炭沼泽退化过程中的优势种从未退化时乌拉苔草（Carex meyeriana）演变为退化时的问荆（Equisetum arvense）。沼泽化草甸退化过程中的优势种从未退化时藏嵩（Kobresia tibetica）演变为轻度和中度退化程度时的青藏苔草（Carex moorcroftii）和密毛白莲蒿（Artemisia sacrorum.var mess-rschmidtiana）；重度退化程度时仅有零星的冷蒿（Artemisia frigida）、珠芽蓼（Polygonum viviparum）；主要伴生种表现为湿生植物逐渐消失，中、旱生毒杂草逐渐增加。泥炭沼泽的植物物种丰富度和多样性指数呈增加趋势，沼泽化草甸为先增加后降低，均匀度指数恰好相反；群落相似性系数逐渐降低。说明尕海湿地原有植物群落物种多样性分布格局向杂草型退化方向演替，建议减少放牧压力，采取人工措施促进尕海湿地生态功能恢复。

关键词: 甘肃尕海湿地, 退化程度, 植物生物量, 物种多样性