Abstract: Species composition of a grassland community has significant effects on soil nutrient contents and nutrient distribution. Under grazing pressure, native plant species may be replaced by invasive or toxic weeds highly adapted to the local soil type, resulting in degraded grassland. Stellera chamaejasme is one such invasive species that has become the dominant species in degraded grassland in parts of the Qinghai region, where it is often found with patchy distribution within stands of other plant species. However, few studies have examined the effects of S. chamaejasme patches on the surrounding grassland community or on soil physical-chemical properties in degraded grassland of Qinghai-Tibet Plateau. Therefore, aboveground biomass, diversity indexes and soil nutrient contents were measured within or between S. chamaejasme patches in natural grassland or after herbicide treatment. It was found that aboveground biomass, species richness index and Shannon-Wiener index were significantly lower between patches than within patches untreated with herbicide. However, after herbicide application, the aboveground biomass and diversity indexes did not differ between and within S. chamaejasme patches. Meanwhile, soil water content, organic matter content, total nitrogen, available phosphorus, and NH4+-N contents were significantly higher within patches than between unsprayed patches. In addition, soil water, organic matter, and herbage total nitrogen contents within unsprayed patches were higher than within herbicide sprayed patches. However, available potassium content was higher within, than between patches receiving herbicide, Therefore, soil water and nutrient within-patch were higher than between-patch, demonstrating that S. chamaejasme patches had characteristics of a “fertile island”. Effective restoration of degraded S. chamaejasme grassland should include improvement measures, such as control of grassland carrying capacity, weed control, fencing and fertilization. With such measures in place, ecologically sustainable development of grassland where S. chamaejasme is present, can occur.

Key words: Stellera chamaejasme, patch, diversity index, soil nutrient, fertile island, herbicide