[Changes of four common plant populations growth and their anti-oxidative enzymatic system in desertification process].

This paper studied the changes of the growth and anti-oxidative enzymatic system of four common plant populations during the desertification process of sandy grassland. The results showed that in the process of desertification, the individual height and density and the density percentage of the populations all had a decreasing trend. The growth of Melilotoides ruthenica was more vigorous before moderate desertification (MD) stage, but restricted after that. In MD stage, the growth of Leymus chinensis was heavily restricted, and its individual height, density and density percentage accounted for 57.19%, 2.50% and 6.22% of those in original vegetation (OV) stage, respectively. The individual height and density of Cleistogenes squarrosa and Artemisia frigida increased in the stages of potential desertification (PD), light desertification (LD) or MD because of their phase status of dominant species and their stronger stress resistance. The SOD and POD activities of the common plant populations increased in PD and MD stages, but decreased in LD and heavy desertification (HD) stages. The CAT activity of Leymus chinensis was higher, whose response to desertification was not significant (P > 0.05), and that of Melilotoides ruthenica increased significantly in PD and HD stages (P < or = 0.01). The activities of the three anti-oxidative enzymes in the common plant populations, except the CAT activity of Melilotoides ruthenica, decreased in HD stage. The MDA content in the common populations increased firstly, then decreased, and finally increased from OV to MD stage, and had a significant difference in different desertification gradients (P < or = 0.05). Based on the integrated analysis of the ecological and physiological changes, it could be concluded that Leymus chinensis was more sensitive to desertification, while Melilotoides ruthenica had a stronger bioenergy.