3.4 Ecosystem multifunctionality
Nitrogen addition significantly affected the EMF of L. chinensis grassland in saline-sodic soil (Fig.7). The analysis of one way ANOVA showed that there were significant differences on the EMF of L. chinensisgrassland under different N addition rates (F=35.33,P <0.001, Fig.7A). The EMF was negative when N addition rates were from 0 to 60 kg ha-1, and the EMF was positive while N addition rates were from 90 to 210 kg ha-1. This demonstrated that the EMF of L. chinensis grassland increased with N addition rates increasing in saline-sodic soil, but the EMF didn’t increase when N addition rates reached enough levels (from 120 to 210 kg ha-1in the study). It was found that the relationship between the EMF and N addition level was quadratic curve model (R2=0.88116,P <0.0001, Fig.7B). In the study, the EMF was the maximum when N addition rates were 150 or 180 kg ha-1, while the EMF would decrease if N addition rate reached at 210 kg ha-1. Therefore, the EMF of L. chinensisgrassland was affected by N addition rates to a large extent in saline-sodic soil of Northeast China.