Authors’ Contributions
D.H.X. and X.W.F. conceived the study and designed the methodology; W.B.M., X.J.W. and R.Y.Z collected and analyzed the data; D.H.X., J.L.Y. and G.Q.Y. led the writing of the manuscript. All authors contributed critically to the drafts and gave final approval for publication.
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List of Figures
Fig. 1. Aboveground biomass of grasses (a, b) and community (c, d) in native grasslands and active restoration grasslands. Various alphabetical characters depict significant difference atP <0.05.
Fig. 2. Pn (net photosynthetic rate) (a, b), gs (stomatal conductance) (c, d), WUEi (instantaneous water use efficiency) (e, f) and Ci (intercellular CO2 concentration) (g, h) of grasses in native grasslands and active restoration grasslands. Various alphabetical characters depict significant difference at P <0.05.
Fig. 3. Relationship of Pn (net photosynthetic rate) (a), gs(stomatal conductance) (b), WUEi (instantaneous water use efficiency) (c) and Ci (intercellular CO2concentration) (d) with aboveground biomass of grasses in native grasslands and active restoration grasslands.
Fig. 4. Plant N (a) and P concentration (b) in native grasslands and active restoration grasslands. Various alphabetical characters depict significant difference at P <0.05.
Fig. 5. Relationship of plant N (a) and P concentration (b) with aboveground biomass in native grasslands and active restoration grasslands.
Fig. 6. Principal components analysis (PCA) for all measured photosynthesis related parameters and N and P concentration alongside degradation in native grasslands (a) and active restoration grasslands (b). AGB (aboveground biomass), Pn (net photosynthetic rate),Ci (intercellular CO2 concentration), gs(stomatal conductance), and Tr (transpiration rate), WUEi(instantaneous water use efficiency), plant N (nitrogen concentration), plant P (phosphorus concentration).
Fig. 7. Structural equation models (SEM) based on the effects of degradation level of native grasslands and replanting time of active restoration grasslands on eco-physiological properties and AGB. Black and red arrows indicate negative and positive relationships, respectively. The width of arrows is proportional to the strength of path coefficients. As in other liner models, R2 indicates the proportion of variance explained and appears above every response variable in the model. Significance levels are as follows:P <0.05,✱✱P <0.01,✱✱✱P <0.001. (a) native grasslands (χ2/DF=0.843, P =0.537, CFI=1.000, RMSEA=0.000; NFI=0.976; RFI=0.917) (b) active restoration grasslands (χ2/DF=0.881, P =0.508, CFI=1.000 RMSEA=0.000; NFI=0.985; RFI=0.947).