The Effects Of Phosphorus Application And Aqueous Root Extracts Of Stellera Chamaejasme On The Growth Of Leymus Chinensis And Soil Chemical Characteristics

A large number of poisonous plants that grow on degraded grasslands directly poison livestock and reduce grassland utilization,meanwhile compete with other herbages for light,moisture,nutrients and space.Stellera chameayasme is a common poisonous plant to animal on the grasslands in the north of China.It can even become a dominant species in some types of degraded grasslands.The reason why S.chameayasme has a strong competitive advantage is because animal's refusal to eat and a strong ability to resist drought and cold,but beyond that allelopathy is also an important reason.However,it is still unclear what role and ecological mechanism that allelopathy plays in the interspecies relationship between S.chameayasme and its adjacent herbages.In this study,L.chinensis was used as the experimental material to conduct a two-factor interaction experiment with phosphorus and aqueous root extracts of S.chamaejasme(ARES).Phosphate fertilization gradients were set no phosphorus(P0),low phosphorus(P1,0.52g/time·pot),and high phosphorus(P2,1.04g/time·pot);the concentration gradients of ARES were set no application(WN),20 times diluted of ARES(W20),5 times diluted of ARES,and on diluted of ARES(W0).This study intends to answer the following scientific questions: 1.Does ARES have a promoting or inhibiting effect on the growth of L.chinensis? 2.How does ARES affect physical and chemical properties of soil,especially availability of nitrogen and phosphorus? 3.What is the mechanism of allelopathy in the interspecies relationship between the S.chameayasme and adjacent herbages? The experiment lasted for 2 years.The main conclusions are as follows:(1)ARES could promote the phenotypic characteristics and biomass of L.chinensis.And this positive effect tended to increase with the increasing of ARES.but different phenotypic characteristics of L.chinensis had different sensitivity to root aqueous extract of S.chamaejasme,especially,the number of ramets and aboveground biomass.(2)Phosphate fertilizer could promote the phenotypic characteristics and biomass of L.chinensis,but their interactions had no significant effect on the growth of L.chinensis.Therefore,ARES changed the balance of nitrogen and phosphorus requirements of L.chinensis and then changed the positive effect of phosphate fertilizer on the growth of L.chinensis.(3)Phosphate fertilizer had a significant inhibitory effect on soil available nitrogen,while ARES significantly promoted soil available nitrogen.However,the interaction had no significant effect on the content of available nitrogen,but a significant difference in available phosphorus.The influence varied with different concentrations.Therefore,S.chamaejasme affected the utilization of nitrogen and then influenced the effect of phosphate fertilizer on the growth of L.chinensis.In summary,the poisonous plant S.chamaejasme might affect the growth of adjacent plants by releasing allelochemicals,and then affected the physical and chemical characteristics of the soil,especially the effectiveness of some nutrients,to obtain a certain competitive advantage.This study provided a new approach for revealing the interspecific relationships and ecological mechanisms between poisonous plants and their adjacent herbages on the grassland.