Abstract: This paper studied the changes of the main plant species leaf area and their relationships with soil factors in the process of grassland desertification under natural conditions. With the intensification of desertification, the specific leaf area (SLA) of Leymus chinensis and Cleistogenes squarrosa decreased significantly (P<0.01) at early desertification stage (gradient Ⅰ), and that of Potentilla tanacetifolia and Agrostis cristatum decreased significantly (P<0.05) at late desertification stage (gradient Ⅲ). The SLA of Carex duriuscula had no significant change (P<0.05), but that of Artemisia frigida and Melilotoides ruthenica decreased significantly from mid- and late desertification stage (P<0.05) and from early desertification stage (P<0.01), respectively. The leaf area index (LAI) of M. ruthenica increased significantly (P<0.01), while that of the others decreased significantly (P<0.01). The LAI of L. chinensis and C. squarrosa was significantly positively correlated with soil clay, C, N, and moisture contents (P<0.01), and significantly negatively correlated with soil C/N ratio (P<0.01); while the correlations of the LAI of A. frigida and M. ruthenica with the soil factors were quite opposite (P<0.05) from those for L. chinensis and C. squarrosa. The linear fitting between the LAI of C. squarrosa and soil C/N was the highest (R²=1), followed by that between the LAI of L. chinensis and soil moisture content (R²=0.992), and between the LAI of M. ruthenica and soil C/N (R²=0.268). Our results suggested that in the process of grassland desertification, soil C/N was the key factor affecting the leaf area of common species (P<0.5), with the order of the effect being C. squarrosa > L. chinensis > A. frigida > M. ruthenica.

Key words: Stratification porosity, Optical stratification porosity, Hemispherical silhouette, Secondary forest, Forest management