Eutrophication causes loss of plant species diversity globally, which decreases ecosystems stability. Diverse mechanisms, including competition for light or nutrients, litter accumulation, soil acidification, toxic manganese (Mn) or aluminum (Al), have been showed to be responsible for this loss. However, the mechanisms have been difficult to determine and contradictory, and only one mechanism was used to explain the species loss in a specific ecosystem.
Results/Conclusions
Here we showed three stages of plant species loss using a 11-year fertilization experiment in an Inner Mongolia grassland and most possible mechanisms underlying the loss were tested using a serial of greenhouse experiments. First stage, relative biomass of forbs increased while grasses decreased with fertilization due to the competition between grasses and forbs. There was no detectable role for light and litter. Second stage, forbs decreased while grasses recovered with the increase of manganese in the fertilized soils. Third stage, forbs and bunchgrasses decreased dramatically which rhizome grass erupted with the increase of aluminum. Mn and Al addition showed consistent species composition change with stage two and three. Thus, competition exclusion, Mn and Al toxic, are responsible for the plant biodiversity loss after eutrophication in different stages respectively.