Pennisetum flaccidum Patch Formation Promotes Soil Fine Particle Enrichment and “Fertile Island” Development in Alpine Meadow of Damxung, Tibetan

Grasslands are the most widespread terrestrial ecosystem on Earth, in which plant patches, as the fundamental spatial units, play a crucial role in maintaining ecological functions. However, research on the effects of perennial herbaceous patches on soil texture and nutrient retention, as well as the mechanisms underlying these effects, remains limited. To investigate the mechanisms how patch formation influences soil texture and nutrient retention, we combined field sampling with laboratory analysis to study vegetation characteristics, soil particle composition, and nutrient content in different-sized Pennisetum flaccidum patches and unpatches in alpine meadow of Damxung, Tibetan. Results indicated that, compared to areas outside patches, patches showed increases in aboveground biomass and vegetation coverage by 289~581 g·m-² and 13~25%, respectively, while sand content decreased by 7.1~19.4%. Total carbon and total nitrogen content increased by 8.8~3.1% and 35.6~117.7%, respectively; soil organic carbon, available nitrogen, and available phosphorus content increased by 10.3~56.7%, 21.8~91.3%, and 26.2~74.9%, respectively; and soil bulk density decreased by 8.7~30.5%. Soil monofractal dimension and key soil nutrients were positively correlated with aboveground biomass, coverage, and clay content, and negatively correlated with soil bulk density and sand content. Thus, patch formation of P. flaccidum improves soil texture and enhances soil fertility in the Tibetan alpine meadow, with increased vegetation coverage and biomass playing a key role. In summary, the patchy distribution of key plants promotes fine particle enrichment and the “fertile islands” development, highlighting its practical implications for maintaining ecosystem stability, reducing soil erosion, and promoting sustainable grassland management.