Research On Soil Seed Banks Of Artemisia Giraldii Communities In Loess Hill-gully Region

The objects of this research are a series of Artemisia giraldii communities,locating in the Junger Loess Hill-gully Region.These communities are different in their growth environment-gullies of various development periods.There are five communities being studied:Ⅰ. Artemisia giraldii+annual and biennial herb community,Ⅱ.Artemisia giraldii+Poa sphondylodes community,Ⅲ.Artemisia giraldii+Stipa grandis community,Ⅳ./Caregana opulens/-Artemisia giraldii+Stipa grandis community and C.Stipa bungeana community.CommunityⅠ-Ⅳare hilly communities,while community C is the control.We survey the aboveground vegetations and soil seed banks of these communities,as well as the relationship between them.It's important for comprehensive understanding of hilly vegetation and effective vegetation restoration.The results are as follows:(1) Families,genus and species of communityⅠtoⅣshow an increasing trend.While community C locate betweenⅠandⅡin this arrangement.Compositae,Gramineae and Leguminosae occupy a fairly large proportion in these communities.Similarity coefficients among aboveground vegetations of these five communities range from 0.333 to 0.654,with a mean value 0.483.Perennial herb is the dominant life form.(2) Comparative relationship of germinating seedlings,families, genus and species among five soil seed banks is similar with aboveground vegetations,that is,Ⅳ＞Ⅲ＞Ⅱ＞C＞Ⅰ.Compositae and Gramineae occupy a fairly large proportion in these communities.Soil seed banks show higher similarity among five communities,ranging from 0.488 to 0.737 with a mean value 0.654.Perennial herb is the dominant life form.Importance values and densities of Artemisia giraldii and Artemisia commutata are the biggest two in communityⅠ-Ⅳ.While in community C,Lespedeza davurica.(3) Species of soil seed banks are lower than that of aboveground vegetations in hilly communities(exceptⅡ).Similarity coefficients between soil seed bank and aboveground vegetation in communityⅠ-Ⅳrange from 0.510 to 0.597,with a mean value 0.538.While in community C it is lower,that is,0.333.Shannon-Wiener diversity indices,Pielou evenness indices and ecological dominances of soil seed banks are also lower than that of aboveground vegetations in hilly communities.While this comparative relationship is opposite in community C.