Effect Of Root Competition On Seedling Height Growth In Two Succession Stages

In the forest ecosystem,to study the sustainable management of forests,the first factor we should consider is forest renewal.The way and process of forest renewal will affect the level and structure of forest community in varying degrees.The growth of regenerated seedlings is an important part of the whole forest regeneration process,and high growth is the most direct indicator to measure the level of regeneration of seedlings.At present,the research on regeneration seedlings mainly focuses on the above-ground part,but the height growth of plant seedlings is determined by both the above-ground and underground parts.Studies show that the fierce root competition will significantly affect the growth and development of seedlings,so it is particularly important to explore the effect of root competition on regeneration seedlings.In order to make the research results more universal,the one-year-old seedlings of Betula platyphylla and Acer mono Maxim were selected as the research objects.Poa pratensis,a plant with high distribution in the forest,was used as competitive herbs.Soil nutrients were designed according to the heterogeneous distribution of most soils in nature.Based on the background conditions of availability and heterogeneity of nutrient distribution,the effects of root competition on the formation and development of asymmetric competition in shoot and underground parts of seedlings were described by establishing structural equation model.The mechanism and pathway of root competition were explored by combining the morphological indexes of root and leaf in shoot and underground parts of seedlings.The results are as follows:(1)According to the model of comprehensive competition intensity index of tree species,root competition intensity and crown competition intensity have very significant effects on seedling height growth.The standardized path coefficients of root competition intensity are 0.215 and0.092,respectively.Root competition intensity plays an important role in seedling height growth.(2)According to the model of root competition mechanism,the intense root competition among plants can affect the proportion of three sub-diameters of fine roots.The nutrient uptake capacity of three sub-diameters of fine roots to latent variables is the main part of the nutrient uptake function of plant roots,which ultimately affects the growth of seedling height.This phenomenon is under different nutrient distribution conditions and different root attributes.The seedlings are reflected in each other.(3)According to the model of root competition mechanism,root nutrient uptake capacity has a very significant indirect effect on seedling height growth through leaf photosynthetic capacity.Point estimation value is 0.013,accounting for 69.8% of the total effect,indicating that indirect pathway is the main way to play its role.(4)Root competition in two succession stages has different effects on seedling height growth of forest regeneration.The indirect effect of root nutrient uptake capacity on seedling height growth was 25.2% in the early succession stage,which indicated that the main way for root competition to affect seedling height growth of forest regeneration in the early succession stage was direct,while the indirect effect of root nutrient uptake capacity on seedling height growth in the late succession stage accounted for the total effect.The proportion of root competition in late succession stage was 81.9%,which indicated that the main way to influence seedling height growth of forest regeneration was indirect.This experiment explored the effect of root competition on the seedlings of forest regeneration in the process of forest regeneration,quantified the mechanism and pathway of interaction between root competition and crown competition under different conditions,helped to improve the theory of forest regeneration,and provided a theoretical basis for the related work of forest management.