Research On Soil Seed Bank Of Jujube Garden In Yellow River Basin Of Northern Shaanxi

Jujube tree is one of the main economic tree species of farmers in northern Shaanxi.The extensive management of jujube gardens has seriously affected the yield and quality of jujube fruit.In this paper,the research object is jujube orchard of hillside fields,terrace and sand beach in the main production area of red dates in Yanchuan County,Yan'an City.Samples are collected in spring,summer,autumn and winter.The method of indoor seed germination is adopted.The species composition,reserve,life form,vertical distribution,species diversity and similarity of soil seed bank in jujube garden were studied.The seasonal variation of soil seed bank in jujube orchard and the occurrence of soil seed bank of different site types under different management methods are discussed.It can provide some theoretical basis for weed control in jujube orchard.The results are as follows:(1)In the soil seed bank of jujube garden,22 species from 7 families germinated,and the total number of germination is 112933.33±5547.77 seeds/m~2.The species composition is mainly Gramineae and Compositae,the species life type is mainly perennial herbs(16 species),and there are only 6 species of annual herbs.The dominant species in spring,summer and winter are highly similar,including Echinochloa crusgalli,Chenopodium glaucum,Bothriochloa ischaemum,etc.Autumn is different from other three seasons.There are significant differences in dominant species among hillside fields,terrace and sand beach,which are Leymus secalinus,Portulaca oleracea and Calamagrostis epigeios.There are significant differences in the number of soil seed banks under different seasons and different site types,which are shown as follows:spring>winter>autumn>summer and hillside fields>sand beach>terrace.Under the condition of no management,the total number of soil seed bank in jujube orchards is significantly higher than that in jujube orchards under management and there is a certain correlation between the number of species and germinations.Under the condition of management,there is no obvious correlation.(2)There are significant differences in the vertical distribution of soil seed banks under different management methods.Under the condition of management,with the deepening of soil layer,the number of soil seed bank increases first and then decreases,and the main performance is 5-10 cm>0-5 cm soil layer.Under the condition of management,with the deepening of the soil layer,the overall change of the number of soil seed banks is decreasing layer by layer.In each soil layer,with the change of seasons,the number of soil seed banks in jujube orchards decreased first and then increased.There is no significant difference in the vertical change trend of the number of soil seed banks between different land type.(3)The shannon-weiner index,margalef index and pielou index of soil seed bank showed a trend of decreasing first and then increasing with the change of season,but the dominance index changes in the opposite direction.There is no significant difference in every index between spring and winter.The shannon-weiner index,margalef index and pielou index of soil seed bank in summer are significantly lower than those in spring and winter.Autumn is slightly higher than summer,but overall smaller than spring and autumn.Hillside fields and sand beach are in 3 years unmanaged conditions,the shannon-weiner index,margalef index and pielou index of soil seed bank were improved obviously.Every index of terraced fields in 10 years unmanaged state are significantly smaller than those of hillside fields and sand beach.Under the condition of management,except for the dominance index,other indexes were significantly less than those without management.(4)The coefficient of species similarity between different land types in the same season ranges from 0.571 to 1.0,and it is mainly concentrated between 0.70 and 0.83.The similarity coefficient between different seasons of the same land type ranges from0.143-0.696.The similarity coefficient range between different seasons in the same land types is 0.143-0.696.The species similarity between summer sand beach and different land types under other seasons ranges from 0.143 to 0.429.The similarity coefficient of jujube orchards is not affected by different management methods.