Study On The Characteristics Of Soil Seed Bank And Its Influencing Factors And Activation Effect In Arid Desert Mining Area

Ecological restoration in arid desert mining area has been getting increasing attention in recent year,and the scarcity of soil resources was the primary issue.However,the work of topsoil stripping,protection and utilization has not been paid much attention,resulting in the waste of great amount of soil and seed resources.In this study,Wuhai,typical coal mining city in the arid desert region of Northwestern China,was taken as the study area.The characteristics of soil seed bank（SSB）and its influencing mechanism were studied through field investigation and analysis.The activation conditions and effects of SSBs were investigated by field germination experiment under different rainfall gradient and combined application of water,fertilizer,and gibberellin.The main findings are as follows:（1）The average SSB density around Wuhai was 217～1547 seeds·m^-2,which decreased with the increase of soil depth.The persistent soil seed bank（PSSB）proportion ranged from 17.34%to 64.22%.The species and community composition of SSBs were different from those of aboveground vegetation.Soil organic matter,silt,clay and gravel content were the most important factors on PSSB and soil total phosphorus,clay content,organic matter and bulk density were the main factors on transient soil seed bank（TSSB）.SSBs in the phytocoenosium of Reaumuria songarica（Tetraena mongolica）,Salsola passerine and Stipa krylovii of gravel steppe desert and R.songarica（T.mongolica）,Oxytropis aciphylla and Stipa glareosa of sand steppe desert had high availability in vegetation restoration.（2）In the phytocoenosium of T.mongolica（R.songarica）,S.passerine and S.krylovii,the SSSB and HSSB1 had higher spatial heterogeneity.As scale increased,the spatial autocorrelation of SSSB and HSSB2 increased.In the phytocoenosium of R.songarica,O.aciphylla and S.glareosa,the SSSB and HSSB1 had lower spatial heterogeneity than HSSB2.The spatial autocorrelation of all types of SSBs presented the trend of increase and decrease alternately with scale increased.The spatial distribution of SSB was mainly correlated with shrubs（clustered under or around their canopy）,but no obvious correlation with herbaceous vegetation.（3）The edge gradient of fragmented plaques had significant positive effect on the SSB density（p=0.0001）,especially annual herbaceous species in 5～10 cm soil layer.And it had significant negative effect on the SSB richness（p<0.0001）.The patch area had significant positive effect on the SSB density（p=0.004）,but had no significant effect on SSB richness.Mining disturbance can directly affect the vertical distribution of SSBs.And it also changed soil structure,and affected vegetation growth by affecting soil moisture,organic matter,p H,thus indirectly affecting SSBs.These influence pathways are interlinked.PSSB and TSSB had different responses to disturbance.Mining disturbance had no effect on the PSSB density,but increased the TSSB density.（4）There were significant differences in the composition and number of germinated species in SSBs activated by different rainfall.In normal and high flow years,the average soil moisture content reached 8.2～18.8%and rainfall could activate 88%species and 63.47～83.3%seed number of PSSB in0～5cm layer.Combined with irrigation,nitrogen and phosphorus fertilizer and gibberellin,100%species and 94.61%seed number of PSSB could be activated.The order of influence of factors was water>phosphorus>gibberellin>nitrogen.Water was the most significant factor on SSB germination,while nitrogen had no significant effect on SSB germination and seedling growth.The optimal treatment was nitrogen 11.93 g/m³,phosphorus 11.06 g/m³,water 28.35%and gibberellin 0.09%.（5）A total of 33 species were found in the SSBs around the mining area,with an average density of720 seeds·m^-2,which reached the regional average.SSB had good buffering and anti-interference ability,so it was feasible to use for restoration in the degraded areas.However,SSBs had low SSSB density and low similarity of species composition with aboveground vegetation,so its vegetation restoration potential in mining areas was still limited.So appropriate human assistance measures such as irrigation,fertilization and resowing were needed.to achieve the goal of near-natural vegetation restoration.