Impact of Tower Foundation Construction of Power Transmission Line project on Plant Diversity in Alpine Meadows in the Hengduan Mountains

Abstract: background Alpine meadows is a vital component of the alpine ecosystem in the Hengduan Mountains. It is highly sensitive to climate change and human activities. The land surface disturbance caused by tower foundation construction of power transmission line project has significantly affected native vegetation and plant diversity due to harsh regional environment, short growing seasons, simple ecological structures, weak self-renewal capacity and other characteristic. Methods The research area was selected from alpine meadows above 4000m in the western of Sichuan and the southeastern of Xizang within the Hengduan Mountains. Five investigation sites were established, with 3-4 tower foundations randomly selected as sample plots at each site. The area of sample plot was corresponded to the actual construction-disturbed area of the tower foundation. This research compared the number of species and indices of plant diversity of native vegetation in western Sichuan and southeastern Xizang within the Hengduan Mountains with vegetation in construction-disturbed areas. Through surveys of species composition and calculations of biodiversity indices, the impacts on plant diversity with construction disturbance in alpine meadows were analyzed. Furthermore, environmental and soil factors, such as elevation, radiation value, mean annual temperature, mean annual precipitation, soil organic matter content, and soil gravel content were investigated and key factors influencing plant diversity caused by construction disturbance were analyzed. Results The research results indicate that: (1) After construction disturbance, the number of species decreased by 4~20, while number of new species added species ranged from 5~23, and the dominant species in 75% sample plots were varied; (2) But construction disturbance altered the physical properties of the soil, reducing the average soil organic matter content from 9.99% to 3.11%, which decreased of 6.88%;Simultaneously, it increased the gravel content in the soil from 41.21% to 65.61%, which increased of 24.40%. (3) Construction disturbance significantly reduced vegetation coverage from 98.75% in control plots to 55.88%. Simpson's, Shannon-Wiener, and Pielou indices were lower than that in control plots, which were decreased by 0.11, 0.43 and 0.12; (4) After construction disturbance, the indices of plant diversity showed significant correlations with mean annual temperature, elevation, and soil organic matter content, which were identified as limiting factors for vegetation recovery. Conclusions Tower foundation construction of power transmission line project had a significantly effects on species composition and plant diversity of alpine meadows. It is recommended that post-construction measures include topsoil restoration and temporary cover to improve plant growth conditions and promote regional vegetation recovery and sustainable ecosystem development.