College of Ecology and Environment/Key Laboratory of Biodiversity and Ecological Environment protection of the Qinghai-Xizang Plateau, Ministry of Education, Xizang University, Lhasa 850000, China
As one of the most fragile high-altitude ecosystems worldwide, the open alpine meadows on the Qinghai-Tibetan Plateau exhibit ecological stability that is highly dependent on the adaptive responses of plant communities to environmental disturbances. This study was conducted in a yak-grazed pasture located in Nian Village, Riduo Township, Maizhokunggar County, Xizang Autonomous Region, China (elevation 4 423~5 015 meters above sea level) representing the typical habitat of yakspaths during the main grazing season. Along the typical round-trip foraging paths of yaks, 190 samples were established to systematically investigate the distribution patterns of 38 dominant plant species. Niche overlap of species was quantified using the Jaccard index and Pianka index. Furthermore, Principal Coordinates Analysis (PCoA) was applied to explore the driving mechanism of interspecific relationships within plant community. The results revealed that there are 19 pairs of high niche overlapping species (Jaccard>0.7) in the community, and dominant speciessuch as Kobresia humilis and K. pygmaea pairs of species in the community,exhibit the highest niche overlap values and forming a core functional group. In contrast, 10 pairs of species with low niche overlap value (Jaccard<0.2), such as Euphorbia stracheyi and Bryophytes, demonstrated high specialization or strong habitat adaptation. Theniche overlap matrix (based on jaccard/Pianka index) confirmed that pairs of species with high niche overlap value exhibit resource sharing characteristics, whereas those who with low niche overlap values exhibit minimal competitive interaction. Principal Coordinate Analysis (PCoA)based on niche overlap matrix revealed that the first two axes collectively explain 36.9% of the variation in species relationship. Most species clustered along the first axis, forming a core group, whereas a few specific species were distinctly separated from the core cluster. These results suggested that species within the core group exhibit adaptive differentiation to similar environments, while the separated species may occupy distinct ecological niche due to specialized habitat preferences or resources utilization.
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