Plant species diversity of grassland plant communities in permafrost regions of the northern Qinghai-Tibet Plateau

The Qinghai-Tibetan Plateau is a key genetic resource region for plant flora and river resources in China, and has the largest and most species-rich alpine grassland ecosystem. Grassland plays a very important role in animal production, biodiversity and water conservation. Changes to grassland communities resulting from degradation of frozen soil and highway construction affect the processes of ecology. To gain insight into the contribution of biodiversity to the stability of this grassland ecosystem, there is an urgent need to study the effect of degradation of frozen soil and highway construction on the plant biodiversity of the grassland communities. A survey of biodiversity was undertaken during 2001 and 2002 along the Qinghai-Tibetan Highway from Xidatan (94°10.016′E,35°43.063′N) to the southern Tanggulashan Pass (33°07.120′E,91°52.670′N), to study the change of species diversity between plant communities, and the effect of degradation of frozen soil and highway construction on plant biodiversity of grassland communities in the permafrost regions of the Qinghai-Tibetan Plateau. Thirty-two spots were selected according to the different grassland communities present (Kobresia pygmaea meadow, Kobresia humilis meadow, Carex moorcroftii meadow and Stipa purpurea steppe community) and the successional communities series (marsh meadow, steppe meadow, steppe meadow and steppe) in the process of frozen soil degradation. Two or three sampling zones of 1 m×100 m were designed at each spot (75 in total). Each sampling zone contained ten 1 m×1 m plots which were arranged every other 10 m. In each plot, all plant species present were counted, and coverage and frequency were recorded. Environmental factors including latitude, longitude, and altitude were measured by GPS and recorded. Biomass was measured by harvesting and drying. The species diversity of the plant communities was calculated using the Shannon-Wiener (diversity) index (H), the Pielou (evenness) index (J), and richness index (species number) (S). This study showed that the richness species index (S) was not significantly different among the communities, and about ten 10 plant species were present in the survey plots for each plant community, whereas evenness index (J) and diversity index (H) were significantly different (P0.05) between the Kobresia pygmaea meadow community, the Kobresia humilis meadow community, the Carex moorcroftii meadow community, and the Stipa purpurea steppe community. Evenness index measurements decreased gradually: Kobresia pygmaea meadowStipa purpurea steppeK. humilis meadowCarex moorcroftii meadow. Diversity index decreased gradually from Kobresia pygmaea meadow community to Kobresia humilis meadow community to Carex moorcroftii meadow community to Stipa Purpurea steppe community. Compared natural communities with restored communities, this study detected that changes of richness index and evenness index were consistent with diversity index in the restoration process of Kobresia humilis meadow after the severe destruction caused by the construction of the Qinghai-Tibetan Highway in 1976. Diversity, richness, and evenness indices of communities in sampling zones 100m from the Highway were larger than those of the natural communities. Species diversity of the natural communities was greater than that of the communities 50 and 30 m from the Highway. The results of this study indicated that the restoration capacity of vegetation was weak in the permafrost regions of the Qinghai-Tibet Plateau after the severe destruction caused by the highway construction. This study also indicated that the richness index of succession plant community series kept steady within the 1 m~2 plots, but was significantly different within the 100 m~2 sampling zones in the degraded frozen soil. The changeable trend of the diversity index was in accord with the evenness index but not consistent with the richness index. Species diversity and evenness indices increased from marsh meadow to steppe meadow, and decreased from steppe meadow to steppe grassl