Mitigation of nitrogen inputs causes native Phragmites australis recovery following Spartina alterniflora invasion

Abstract Plant invasions driven by global environmental change increasingly threaten natural ecosystems. Whether reducing nitrogen (N) input can help mitigate plant invasions remainsunclear. We used ongoing N reductions in the Yangtze River to explore how N reductions affect native community recovery in estuarine marshes degraded by plant invasions. Using Google Earth images, we mapped native Phragmites australis patches and assessed changes in theirabundance in Spartina alterniflora-invaded marshes, showing that P. australis gradually recovered following reduced N input. To identify the underlying mechanisms, we transplanted N-fertilized and unfertilized S. alterniflora populations into plots with ambient and enriched N conditions and co-planted them with P. australis, respectively; the competitive advantage of S. alterniflora over P. australisdecreased with N reductions, regardless of fertilized population history, shifting the marsh from P. australisexclusion to species coexistence. Thus, nutrient reductions can shift ecosystems from being susceptible to invasion to successional recovery, offering an effective strategyfor mitigating plant invasions and facilitating landscape-scale native community recovery.