Dynamics Of Leaf Litter Decomposition Of Invasive Plants And Its Feedback Effects

Biological invasions are reportedly one of the major contributory factors to biodiversity loss worldwide.The impacts of invasive alien plant species(IAPS)on native communities are widely documented in the scientific literature,however,there is still a lack of detailed information on their impacts within the most vulnerable habitats.Although,leaf litter is one of the productivity components of terrestrial ecosystems,and its decomposition is an important link in the chemistry and nutrient cycle of terrestrial ecosystems.At the same time,litter leaves contain a lot of allelopathic substances,which decompose and release allelopathic substances in the soil,which significantly affects the allelopathy of plants.As a typical malignant weed,the invasive plant species Solidago canadensis L.and Wedelia trilobata have little reports on its effects on soil nutrient cycling and allelopathy during the decomposition of litter in the in situ ecological environment.Therefore,this study adopts greenhouse pot in situ experiments,using the invasive plant species S.canadensis and W.trilobata leaf litter as experimental materials to explore the decomposition rate and its influence on plant-soil feedback under different types of soil at varied soil depths.The purpose is to explore the decomposition of litter and its influence on its invasion,and provide a certain theoretical reference for the research on the invasion mechanism and ecological control of S.canadensis and W.trilobata.The main results of this research are as follows:Using leachate from W.trilobata leaf litter and its effects on the growth traits of both congeneric native Wedelia chinensis and itself invasive plant W.trilobata species under different plant culture was studied.The results show that:(1)Higher leachate concentrations significantly increased most traits of W.trilobata under mono and mixed culture.In contrast,many growths and physiological parameters in W. chinensis were significantly reduced in response to higher concentrations of leachate. Growth and physiological traits were higher in W.trilobata than W.chinensis at higher leachate concentrations in both mono and mixed culture.In W.trilobata,relative competition intensity(RCI)significantly increased with increasing leachate concentration. However,RCI in W.chinensis remained consistently low in response to higher leachate concentrations.(2)Overall,the addition of leachate from invasive W.trilobata had a strong allelopathic effect on native W.chinensis under mono and mixed culture.Conversely,growth and competitive ability in W.trilobata was enhanced in response to the leachate.To study the decomposition rate of S.canadensis leaf litter and its effect on soil chemical properties in different soil types under varied soil depths.The results show that:(1)Litter decomposition was higher at greater soil depths in all soil types(and was highest at 4 and 6 cm in the sandy and clay soils).Among all the soil types,the clay soil had the highest litter decomposition rate.(2)In the nutrient soil,pH increased with increasing soil depth at which litter was added,while in the clay soil,pH values were highest at depths of 4 and 6 cm.In contrast,pH was non significantly different between depths in the sandy soil.Concentration of soil nutrients, including total carbon,total nitrogen,total phosphorus,nitrate,and ammonium,were often higher at depths of 4 and 6 cm in all soil types.In contrast,total phenols and flavonoids were often lower at those same depths.To study the plant-soil feedback during biological invasion: leaf litter decomposition rate of W.trilobata,and its effects on the congeneric plant W.chinensis growth traits as well as on soil nutrients in a range of soil types at varying depths.The results show that:(1)All soils treated with litter displayed an increase in soil nutrients at depths of 2 and 4 cm; while most growth traits,leaf chlorophyll,and leaf nitrogen of W.chinensis decreased at those same depths.Therefore,litter decomposition of invasive W.trilobata resulted in a positive plant-soil feedback on its own growth,but a negative plant-soil feedback on the growth of native W.chinensis.(2)Our findings also suggest the effects of litter decomposition from an invasive plant on soils and native species can vary significantly depending on the soil depth at which the litter is deposited.