石羊河上游干旱草原星毛委陵菜群落土壤种子库

Soil seed bank of Potentilla acaulis community in arid grassland of the upstream of Shiyang River

星毛委陵菜（Potentilla aclaulis）被认为是阻止草原进一步退化的一道＂绿色屏障＂,其群落土壤种子库的退化机制能够为草地生态恢复提供依据。通过大面积调查,研究了石羊河上游干旱草原退化演替过程中星毛委陵菜群落的土壤种子库,结果表明,土壤种子库共有19个物种,分属14个科;随着星毛委陵菜种群分盖度的增加,种子库种类及密度呈递减趋势,禾本科的密度减少,不食草种类减少,但是密度增大;在垂直方向上,种子库的种类逐层减少,密度出现0-5 cm〉10-15 cm〉5-10 cm的变化趋势;星毛委陵菜种子库很小,只占2.93%,其再生途径倾向于无性繁殖;种子库和地上植被的相似性指数平均为0.392,土壤种子库中没有发现原生地带性植被优势种群的种子,反映了草地群落退化的不可逆转性。

Potentilla acaulis is considered as a green barrier to prevent grasslands from further degradation,it has important significance on the direction and improvement of vegetation succession on grasslands,the community degradation mechanism of the soil seed bank can be used to direct grasslands ecology renewing.With field vegetation surveying and laboratory test,the paper chose and identified the seeds from 270 soil samples by adopting physical method,seedling germination and TTC,and then analyzed the soil seed bank of arid grassland＇s Potentilla acaulis community in upstream of Shiyang River.The results showed as follows：a total of 19 plants belonging to 14 families were found in the soil seed bank,3 species were annual herb and 16 species were perennial herb.There was a significant decreasing tendency of the density of grasses and an increasing tendency of non-edible grass with the increase of Potentilla acaulis＇s coverage.The number of plant species and the seed density in the shallow soil layer were larger than that in the deep one.The vertical distribution of seed bank＇s density was presented as the following precedence order： 0-5 cm＇s〉10-15 cm＇s〉5-10 cm＇s,the seeds of different functional groups also showed the same distribution pattern.The soil seed bank of Potentilla acaulis is very small,which is accounted for only 2.93% of the total seed bank,its regeneration pathway is inclined to vegetative propagation.The changes of species diversity index and evenness index tend to be uniform.However,the dominance index of the soil seed bank is opposite to the evenness index and diversity index in vegetation gradients.The average similarity index of seed bank and standing vegetation is 0.392.The similarity of species composition of the soil seed bank and vegetation species composition of the surface belongs to a moderate dissimilar level.There is no finding at the seeds of dominant population of primary zonal vegetation,which reflects the irreversibility of degradation mechanism of grassland community.The change of plant species and functional group composition in the study area basically reflects a series of degradation trend of Potentilla acaulis Community,such as community structural simplification and environmental matrix stability weakening.