Abstract:

The toxic plant Euphorbia fischeriana has spread rapidly in the Hulunbuir grassland in recent years， posing a significant ecological threat. However， its invasion mechanisms and ecological impacts remain unclear. This niche analysis study aimed to elucidate the restructuring mechanisms of plant communities and soil nutrient dynamics following E. fischeriana colonization. Results revealed that as the invasion intensity of E. fischeriana increased， the dominant species in the grassland community shifted from Lespedeza bicolor （dominance： 25.93%） to E. fischeriana （dominance： 18.90%）. In severely invaded areas， plant community biomass decreased significantly by 27% compared to control plots. Concurrently， the niche breadth of major plant species contracted markedly， and the average niche overlap index among community plants increased from 0.55 to 0.65， indicating intensified interspecific competition. Furthermore， the population expansion of E. fischeriana resulted in significantly elevated soil nutrient levels. Total nitrogen， available phosphorus， and ammonium nitrogen contents increased by 41.0%， 29.8%， and 19.8%， respectively， relative to controls. Soil organic matter exhibited an initial decline followed by a gradual rise. These findings suggest that E. fischeriana restructures soil nutrient availability in degraded grasslands through a “fertility island effect”， that provides enhanced its competitive advantage over native plants while reducing grassland productivity. This dual impact of E. fischeriana threatens the sustainable development of local animal husbandry. In conclusion， controlling E. fischeriana proliferation and restoring native plant communities are critical for grassland rehabilitation. This study highlights the necessity of balancing invasive species management with soil nutrient regulation to mitigate ecological degradation.

Key words: Euphorbia fischeriana, niche, community structure, fertility island effect, grassland productivity