Analysis on the soil factor and physiological response of the plants in the process of sandy desertification on grassland

The aim was to find the most practical measure to father desertification on grassland. Three-year research was carried out from 2001 to 2003 in Duolun County, Xilin Gol, Inner Mongolia, China. A series of degradation gradients or stages were established by clustering analysis, and corresponded to 5 community types. Five community types were selected as the sampling sites. Four common plant populations (i.e., Leymus chinensis, Cleistogenes squarrosa, Artemisia frigida and Melilotoides ruthenica) were chosen because of their different physiological responses to sandy desertification. The correlation analysis was made between the soil factor (5 soil indices) and the physiological response of per plant population (7 physiological indices). The results showed that in the course of the sandy desertification on grassland, the physiological response of L. chinensis, an impressible type, had more significant correlations with the soil moisture and C/N in the soil than others (P < 0.01) relatively. The soil moisture and C/N in the soil are likely the key factors for the damage on a physiological level. Its malondialdehyde (MDA) and abscisic acid (ABA) had more significant correlations than others with 5 soil indices as a whole (P < 0.01). C. squarrosa and A. frigida are of resistant types. Only the correlations of C/N among 5 soil indices with both MDAs were consistent and very significant (P < 0.01). Both ABA relations to 5 soil indices were consistent, and, similarly, were very significant (P < 0.01). M. ruthenica, a retarded type, was more sensitive to soil physical character (the soil moisture and the content of clay) than soil chemical character (the content of C, the total N and C/N in the soil), suggesting that the degradation of nutritious elements in the soil is not the leading factor in holding back its growth. Its MDA showed a more significant correlation (P < 0.01) than others as a whole, but its ABA did not show a significant correlation with each of the soil indices (P > 0.05). The synthesis result showed that MDA and ABA in the plants responded intensively to desertification stress. For each of the stress resistant types, there were different soil response mechanisms under different stages. The impressible type responded intensively to the soil moisture and C/N. The response of the resistant type to the soil factor did not appear to be a dominant factor. Altogether, the physiological response of plants mostly had a significant correlation with the C/N in the soil.