Abstract:

The invasion of Stellera chamaejasme has exerted an increasing impact on the alpine meadow ecosystem and animal husbandry on the Qinghai-Tibetan Plateau. In this study， we explored the relationships between S. chamaejasme communities and environmental factors on a local scale， using data for plant communities， soil characteristics， and topography collected from a typical degraded meadow in the central Qilian Mountains. The data were analyzed using two-way indicator species analysis （TWINSPAN）， detrended correspondence analysis （DCA）， and redundancy analysis （RDA）. The main findings were as follows： 1） TWINSPAN divided the 45 plots into three association types： Association Ⅰ-S. chamaejasme+Stipa purpurea+Kobresia capillifolia+Thermopsis lanceolata； Association Ⅱ- S. chamaejasme+S. purpurea+Potentilla chinensis+Saussurea pulchra； and Association Ⅲ-S. purpurea+Anemone rivularis+S. chamaejasme+Poa annua.2）The RDA analysis indicated that the distribution of S. chamaejasme was significantly affected by soil total phosphorus and soil total potassium content， followed by aspect. Soil nutrient contents played an important role in the spatial patterning of the three association types， and S. chamaejasme associations with high coverage were more susceptible to low-phosphorus and low-potassium conditions. 3）Species dominance in Associations Ⅲ， Ⅱ， and Ⅰ changed with the spread of S. chamaejasme， the importance values of the Poaceae forages P. annua and S. purpurea decreased （4.10， 3.12， 2.10），those of the Fabaceae species Gueldenstaedtia diversifolia and Medicago ruthenica initially increased and then decreased （0.28， 0.57， 0.25）， those of the Cyperaceaespecies K. capillifolia and Kobresia humilis increased （0.23， 1.18， 2.19）， and those of forbs and poisonous plants （S. chamaejasme， A. rivularis， T. lanceolata， Anaphalis lactea， and Morina kokonorica） markedly increased （6.10， 5.14， 10.08）. Over time， S. chamaejasme replaced S. purpurea and became the dominant species in Associations Ⅰ and Ⅱ， and the S. chamaejasme coverage increased （5.5%， 11.0%， 29.7%）. The results of this study reveal changes in the characteristics of plant communities in a degraded alpine meadow during S. chamaejasme invasion. These findings provide a scientific basis for the development of strategies to manage， restore， and develop the degraded alpine meadow and to effectively control S. chamaejasme.

Key words: Stellera chamaejasme, degraded alpine meadow, soil and topographic factors, two-way indicator species analysis, detrended correspondence analysis, redundancy analysis