Abstract: Here we set 90 microcosms to simulate the constructed wetlands. The microcosms were planted with 1, 2, 3 or 4 plant species and were divided into ammonium perturbed and unperturbed groups. The results showed that: (1) aboveground biomass increased with species richness in the unperturbed group, but the ammonium perturbation offset the positive effect of species richness; (2) the resistance indicated by aboveground biomass decreased with species richness; (3) the resistance negatively responded to the unperturbed biomass; (4) the presence of Acorus calamus decreased the ecosystem resistance, while the other three species had no such effect. Our study explored the effect of new type of perturbation and extended the studies on the relationship between diversity and ecosystem resistance.

Key words: photosynthesis, AMF, enzymaticactivity., rhizosphere microorganism, cucumber, Spd