Abstract: Riparian vegetation on abandoned croplands after 3-year natural rehabilitation was surveyed with line transect method in Liaohe River reserve, and species composition and factors affecting biodiversity were investigated. Results showed that there were 51 species on 8 sampling sites, and the dominant species were herbs (49 species). The 51 species belonged to 46 genera and 21 families, and Compositae and Gramineae had the most species. The vegetation was mainly composed of singlespecies families, singlegenus families and single-species genera. There were a few species with high frequency and coverage, and Conyza canadensis and Artemisia capillaris as pioneer species in the community succession had the highest appearance frequency. The herbaceous species were mainly mesophytic and annual, and the weeds accounted for a larger proportion of total herbaceous species, indicating that species composition at an early restoration stage on abandoned riparian croplands was affected mainly by human activities rather than the river processes. The species diversity decreased from upstream to downstream. Correlation analysis on environmental factors indicated that Simpson diversity index, Shannon index and Pielou evenness index had positive correlations with altitude and distance from the estuary, and negative correlations with distance from the confluence of eastern and western Liaohe River and sinuosity. While Patrick richness index had negative correlations with the width between levees, and had no correlations with other factors.

Key words: karst mountain., vertical structure, density factor, seedling regeneration