Soil seed bank dynamics of degraded grassland in the crisscross eco-zone of agriculture-animal husbandry in northern China

The dynamics of seed bank of different degraded grassland in the crisscross eco-zone of agriculture-animal husbandry in northern China was studied,and the relationship between the seed bank and above ground vegetation was discussed.The results showed that the species and seed number of soil seed bank showed a decrease pattern with retrogressive succession under different disturbances,such as mowing and grazing.In light degraded grassland,these were the highest of plant species(23) and seed number(4 303) of soil bank among other stages.The percentage of Gramineae was the highest,32.3%.But only 14 plant species and 1 156 seeds presented in soil seed bank at extreme degraded stage.The percentage of Gramineae was the lowest,8.4%.Under retrogressive succession,plant species decreased,moreover,there was certain difference of plant species in soil seed bank and standing vegetation.18 plant species can't be found in the soil seed bank of middle degrading grassland,but there were only 2 plant species at extreme degraded stage.