Adaptability Characteristics Of Pinus Tabulaeformis Carr And Picea Asperata Mast Seedlings To Herbaceous Competition

In the forest ecosystem,interspecies competition is one of the natural phenomena that cannot be ignored,affecting the abundance of individual plants,their survival methods,and their ability to adapt to the environment.Increasing the intensity of competition will increase the pressure of individual plants to survive and even disappear in the community.At the same time,the competitiveness of different species determines the number and dynamics of the population,which in turn determines the distribution and development of species in the community,affects the structure and function of the community,and plays an important role in maintaining the species diversity of the ecosystem.In the process of forest regeneration and development,the health of plant seedlings is crucial.As an inevitable environmental factor for plant seedlings to survive in forest ecosystems,interspecies competition affects its renewal process and may change the succession direction of forest communities.Thus,it has become one of the hotspots studied by ecologists in recent years.Therefore,it is particularly important to explore the adaptability of plant seedlings to interspecific competition.Because gramineous plants can affect the regeneration of plant seedlings by virtue of their high competitiveness,this experiment took Guandi Mountain’s early-successional-stage species of Pinus tabulaeformis Carr and late-successional-stage species of Picea asperata Mast as the research objects,and selected Poa pratensis L as the competing plants.In view of the widespread heterogeneity of soil nutrients in nature,the homogeneity of soil nutrients was set as a control.Combining the heterogeneity of soil nutrients,by analyzing the effects of no neighbours(NN),shoot of neighbours(shoot of neighbours,SN),root of neighbours(RN)and all neighbours(all neighbours,AN)on the seedlings of two target tree species under different soil nutrient distribution conditions,We discuss in depth the adaptation strategies of P.tabulaeformis Carr and P.asperata Mast seedlings in the early growth stage under ideal and realistic soil conditions.The results of the study are as follows:(1)Under homogeneous soil nutrient conditions : Compared with NN treatment,SLA of P.tabulaeformis Carr seedling leaves in SN treatment increased by 22.10%,which increased the area receiving light resources.For the root system,the absorption root SRL and SSA of P.tabulaeformis Carr seedlings increased respectively by 55.13% and 62.25%,and the RTD of P.tabulaeformis Carr seedlings decreased by35.24%.However,the coarse root SRL and SSA of the Chinese pine seedlings decreased respectively by28.6% and 52.41%,and the RTD of the Chinese pine seedlings increased by 74.02%.It can be seen that P.tabulaeformis Carr seedlings actively respond to the harm caused by less light by balancing the morphological changes of different functional roots.In terms of physiological characteristics,the SOD activity of leaf and fine roots of P.tabulaeformis Carr seedlings treated with SN decreased respectively by61.13% and 75.36%,and its antioxidant capacity decreased.(2)Compared with the NN treatment,the SLA of P.asperata Mast seedling leaves in the SN treatment increased by 13.75%,indicating that when the light conditions are weakened,the plants may increase their ability to intercept light resources,and improve the photosynthetic efficiency as much as possible to ensure the need for survival and growth.Different from the P.tabulaeformis Carr seedlings,the P.asperata Mast seedlings treated with SN increased the SRL and SSA of all roots and lowered their RTD under the ground competition conditions.The above results indicate that P.asperata Mast seedlings can actively adjust all root morphological characteristics to improve the ability of roots to absorb water and fertilizer resources from the soil and reduce the loss of water and nutrients under the condition of reduced organic matter synthesis on the ground to meet growth needs.(3)The interaction of soil nutrient distribution and herb competition has a significant impact on the comprehensive characteristics of Pinus tabulaeformis seedlings.From the research results,the seedlings of P.tabulaeformis Carr reduced the fine-rooted SRL and SSA under the underground competition treatment.However,P.tabulaeformis Carr seedlings increased leaf SOD activity under the conditions of aboveground competition and underground competition.It can be seen that the physiological response of P.tabulaeformis Carr leaves is better than the morphological response,the morphological response of the root system is better than the physiological response,and the fine root is an important sensitive response organ.(4)Under the condition of heterogeneous distribution of soil nutrients,P.asperata Mast seedlings did not show active adaptability to ground competition.On the contrary,when P.asperata Mast seedlings adapt to underground competition and aboveground+underground competition,the total root system becomes shorter and thicker,reducing its SRL and SSA.At the same time,P.asperata Mast reduced the SLA under all competitive conditions,which may be due to the P.asperata Mast seedlings changing the carbon allocation strategy to adapt to the competitive environment under the heterogeneous distribution of soil.For physiological adaptation,P.asperata Mast does not show regularity.To sum up,under the condition of heterogeneous distribution of soil nutrients,P.asperata Mast seedlings still adopt the root system’s active morphological response strategy,and the adaptability under the background of underground competition is stronger than that of aboveground competition.In summary,this experiment explored the adaptability characteristics of P.tabulaeformis Carr and P.asperata Mast seedlings to different competition modes under different soil nutrient distribution conditions,revealing that the strategies of different growth habits in the seedling stage of tree species to respond to herb competition are different.The related theories of forest competition mechanism have been improved,providing theoretical support for afforestation of P.tabulaeformis Carr and P.asperata Mast in the study area,and have certain practical significance for maintaining the sustainable development of forest ecosystems.