Studies on the Weed Seedbank of Paddyfield along the Yangtze River in Anhui Province

There are 36 families 105 species weeds in paddyfield along the Yangtze River in Anhui Province.The dominant weed species are summer ripe weeds.Species diversity index H’(Shannon-Wiener index) is H’_{early paddyfield}>H’_{middle paddyfield}>H’_{single season late paddyfield}>H’_{double season late paddyfield} in different paddyfield,but S(Species richness)_{surface layer},H’_{surface layer}>S_{middle layer},H’_{middle layer}>S_{bottom layer},H’_{bottom layer} in the same paddyfield.Most weed seeds(74.78%) concentrated on the surface layer in the soils.Total weed seed density is 319033 seed·m^-2,with the highest summer ripe weed seed density(57.87%),lowest autumn ripe weed seed density(15.74%).The Sorensen similarity index between weed seedbank and community above ground is 0.35 with the highest similarity index of paddyfield weeds(0.41).Linear correlation fit showed lower relationship between them.The results of CCA analysis showed that environmental factors pH and Id has the most important effect on weed dominance,next be Fs and St.