Niche breadth and niche overlap of typical plant communities in the plateau temperate semi-arid river valley climatic region of the Qinghai-Xizang plateau

Introduction: The alpine semi-arid river valleys of the eastern Qinghai-Xizang Plateau are characterized by strong environmental heterogeneity and ecological fragility. Herbaceous plants dominate these ecosystems; however, integrative studies linking niche differentiation, interspecific associations, and community stability remain limited, particularly under extreme alpine conditions. Methods: Based on consecutive field surveys conducted from 2021 to 2025 in Qamdo City, we investigated 109 sampling plots comprising 327 herbaceous quadrats. We quantified niche breadth and niche overlap of dominant species and analyzed interspecific associations and community stability using classical ecological indices and statistical approaches. Results: Dominant species showed clear differentiation between broad-niche generalists and narrow-niche specialists (Levins: 1.03-19.18; Shannon: 0.67-3.15). Overall niche overlap was low, with 70% of values within 0-0.5, indicating strong resource-use differentiation. The herb layer exhibited a weak and non-significant positive overall interspecific association. Significant positive associations mainly occurred among broad-niche species, whereas negative associations were concentrated among species with similar resource requirements. Community stability was insufficient, with a Euclidean distance of 17.22 from the theoretical stable point, suggesting limited structural and functional resilience. Discussion: Pronounced niche differentiation and generally weak interspecific associations represent key adaptive strategies of herbaceous communities in this alpine semi-arid valley system. These patterns reduce competitive exclusion but may also constrain overall community stability. The findings provide important ecological insights and a scientific basis for biodiversity conservation and ecosystem restoration on the Qinghai-Xizang Plateau.