Rapid Expansion of <italic>Melica przewalskyi</italic> Causes Soil Moisture Deficit and Vegetation Degradation in Subalpine Meadows.

Invasive noxious plants have important impacts on community dynamics and ecosystem functions in grasslands. Since the 1960s, the noxious plant <italic>Melica przewalskyi</italic> has spread rapidly and formed different size of patches in subalpine meadows of the Qilian Mountains, Northwest China. In this study, the species richness, vegetation structure, and soil water content are investigated from the patch edge to the center in four sizes of <italic>M. przewalskyi</italic> patches (i.e., small patch, <100 cm in canopy diameter; middle patch, 100–200 cm; large patch, 200–300 cm; and the largest patch, >300 cm). The results show that while the patches grow continuously, the dominant species changes from <italic>Stipa krylovii</italic> to <italic>M. przewalskyi</italic> with an increasing trend in plant productivity and decreasing trend in species richness and soil water content. Plant height, density, coverage, and above‐ground biomass of <italic>M. przewalskyi</italic> population increases from the patch edge to the center in small, middle, and large patches, whereas it is precisely the opposite in the largest patch. Interestingly, soil water content exhibits a decreasing trend from the patch edge to the center in all patches. The results indicate that the rapid spread of <italic>M. przewalskyi</italic> may well alter vegetation pattern and cause a severe soil moisture deficit, which would further drive the degradation of ecosystem functioning in subalpine meadows. [ABSTRACT FROM AUTHOR]