Effects Of Species Combination Reseeding On Vegetation Restoration Of Abandoned Cultivated Land On The Loess Plateau Of Central Longzhong

The Loess Plateau is one of the most fragile ecological regions in China,and also a key area for ecological restoration in China.In recent years,with the development of the rural economy and the improvement of urbanization,the abandonment of farmland in the Loess Plateau has become increasingly serious,and the exposed soil surface and soil erosion caused by abandoned farmland has also become an important aspect affecting the local ecological environment.Multi-species reseeding is considered as an effective way to quickly restore abandoned farmland,while the appropriate reseeding species,the combination of reseeding species,and their relationship with the restoration process is strongly dependent on different types of abandoned farmland.Based on this,this study took the abandoned farmland of the Loess Plateau in Dingxi City,Gansu Province as the research object,set up 15 species combinations with 12 species,and monitored the changes of vegetation,soil seed bank,soil physical and chemical properties under different reseeding conditions for two consecutive years.The main results are as follows:1.Plant communities were significantly affected by reseeding.In addition to vegetation height,reseeding significantly increased（P<0.05）vegetation coverage,underground biomass,plant species richness and Shannon-Wiener diversity,and changed plant community composition（P<0.05）.Among them,gramineae reseeding was beneficial to improve vegetation cover and surface biomass,while legume reseeding was beneficial to improve plant species richness.In addition,reseeded species diversity was significantly negatively correlated with vegetation cover,plant height,aboveground biomass and vegetationβ_Bary（P<0.05）,plant species richness,plant Simpson diversity and Shannon-Wiener diversity were positively correlated（P<0.05）,but not with subsurface biomass andβJaccard（P>0.05）.2.The effect of reseeding on soil seed banks of the abandoned farmland on the Loess Plateau was not significant（P>0.05）.The density,species richness,Simpson diversity,Shannon-Wiener diversity,uniformity coefficient and community composition of soil seed banks did not change significantly after reseeding（P>0.05）and was not significantly correlated with reseeding species richness（P>0.05）,and reseeded species richness only significantly negatively affectedβ_Jaccardandβ_Bary（P<0.05）.Among them,in 2022,the reseeding combinations of 1 gramineae and 1 legume（Stipa bungeana+Lespedeza bicolor）,1 gramineae and 1 forb（Stipa bungeana+Potentilla bifurca）,4 poaceae（Stipa bungeana+Poa pratensis+Onobrychis cyri+Melilotus indicus）,2 poaceae and 2 legumes（Stipa bungeana+Poa pratensis+Lespedeza bicolor+Astragalus melilotoides）,2 poaceae and 2 forbs（Stipa bungeana+Poa pratensis+Potentilla bifurca+Incarvillea sinensis）,4 poaceae and 4 forbs（Stipa bungeana+Poa pratensis+Onobrychis cyri+Melilotus indicus+Potentilla bifurca+Incarvillea sinensis+Heteropappus hispidus+Limonium aureum）.and 12species（4 poaceae+4 legumes+4 forbs）（4 legumes:Lespedeza bicolor+Astragalus melilotoides+Onobrychis viciaefolia+Astragalus melilotoides）significantly reducedβ_Jaccard（P<0.05）.In 2022,the sowing combination of 1 gramineae and 1 forb,4 poaceae,2 poaceae and 2 legumes,4 poaceae and 4 legumes（4 poaceae+4 legumes）,4 poaceae and 4 forbs and 12 plant seeding combinations significantly reducedβ_Bary（P<0.05）.In addition,the low similarity between soil seed banks and aboveground vegetation.3.The effect of reseeding on soil physicochemical properties was not significant（P<0.05）.Reseeding only significantly increased the soil available potassium content（P<0.05）,decreased the total potassium content（P<0.05）,in the reseeding combinations of 4 poaceae and 4 legumes,and did not change the soil bulk density,p H,total carbon,total phosphorus,total phosphorus,organic carbon,nitrate nitrogen and ammonium nitrogen contents（P>0.05）in all treatments..In summary,reseeding was conducive to the rapid recovery of abandoned farmland,while the this process varied with the combination of reseeded species.Reseeding of gramineae was conducive to the restoration of vegetation coverage and productivity while increasing the number of legume species was conducive to the recovery of species diversity.