Responses Of Functional Traits Of Shrub And Grass Of Quercus Variabilis Plantation To Thinned And Its Environmental Interpretation

Quercus variabilis,one of the widely distributed long-lived broad-leaved tree species in my country,has a large amount of fruit and strong sprouting ability.However,due to the lack of scientific and effective management and protection,seedlings and young trees under forest canopy grow poorly.The understory shrub and grass layer is an important part of the forest ecosystem.It not only has ecological functions such as water conservation and water and soil conservation,but also provides a good shade and nutrient environment for the early growth of seedlings,and can form a "nanny effect" and "fertilizer Island effect",which plays an important role in promoting the growth and development of understory seedlings and young trees,enhancing community continuity and forest stand regeneration potential.Thinning is an important man-made intervention to promote natural regeneration.It affects the growth process of understory vegetation by improving the canopy light environment adjusting the forest microclimate.Therefore,studying the effect of thinning on the shrub and herb of under-canopy the Quercus variabilis plantation can provide a basis for formulating scientific artificial measures to promote natural regeneration and shrub and grass management.Plant functional traits are the biological characteristics formed by plants in the long evolutionary process to adapt or reduce environmental disturbances and make full use of environmental resources,which can characterize the ability of plant resources to acquire,reflect the ability of individual plants to adapt to environmental changes.It can reveal the characteristics of plants and adaptation strategies to predict changes in plant communities and ecosystem functions.Plant functional traits are highly sensitive to environmental heterogeneity and can quickly and accurately reveal the response of plants to changes in the microenvironment in the forest and their survival strategies.This paper studies the response of the shrub and grass functional traits of Quercus variabilis plantation to thinning,and used the heterogeneity of the light environment and soil factors in the forest to explain the changes in the functional traits of the shrub and grass after thinning,which is helpful for the study of management measures.The impact on the growth of shrubs and grasses under forests can provide a basis for formulating scientific and reasonable forest tending measures.In this paper,a 40-year-old Quercus variabilis plantation on the state-owned forest farm in Dengfeng City was selected as the research object.Representative forest stands were selected for thinning treatment.The forest stands with basically the same growth environment and similar geographical locations were used as controls.One plot of 100m×100m was set up respectively.Carrying out updated diversity surveys,collect roots,stems,leaves of dominant shrubs and roots,leaves of dominant Herb with important values greater than 0.1,and soil samples,Obtain indicators of sunlight and soil physical and chemical properties on a fixed square sample plot of 100m×100m.To study the effect of thinning on the functional traits of shrubs and grass roots,stems and leaves under Quercus variabilis plantation,and analyze the relationship between soil physical and chemical properties and understory light environment indicators and the functional traits of dominant shrubs and grasses.The main research results are as follows:1.Shrub species diversity index Simpson(1.03)and Shannon-Wiener(0.56)diversity of thinned plots were significantly higher than those of unthinned plots(0.81,0.47)(P<0.05);herb species diversity index Simpson(0.64)and Margalef index(0.74)were significantly higher than the unthinned plots(0.37,0.21)(P<0.05);the dominant shrub species with important values greater than 0.1 were Vitex negundo,Grewia biloba,Ziziphus jujuba;the herbaceous plants are Carex rigescens and Deyeuxia arundinacea,and the dominant shrubs and grasses have ecological widths above 5;the thinned plots and unthinned plots have overlapping shrub niches There were 42 pairs and 18 pairs of logarithms respectively,accounting for 20%and 27.17%of the total logarithms,respectively;there were 10 pairs and 4 pairs of herbaceous species with niche overlap,accounting for 27.78%and 26.67%of the total logarithms,respectively.2.The leaf perimeter,leaf area and specific leaf area of the aboveground part of functional traits of dominant shrub Vitex and Grewia in the thinning plot were significantly higher than those in the unthinned plot(P<0.05).The total root length and root surface area of the main shrubs in the thinned plot were significantly higher than those in the unthinned plot.(P<0.05).The specific leaf area and leaf biomass of the Deyeuxia arundinacea in the thinned plot were significantly higher than those of the same herbaceous species in the unthinned plot(P<0.05).3.The comparative analysis results of the understory light environment indicators of the thinned and unthinned plots show that the understory light environment index of the thinned plots is significantly higher than the canopy opening(24.16%)and the leaf area index(1.03)of the unthinned plots.Corresponding indicators(22.62%,0.94)(P<0.05),the effective photosynthetic radiation intensity(89.25)is higher than the unthinned plot(73.15),but the difference is not significant(P>0.05);direct light and scattering under the forest in the thinned plot The light and total radiation photosynthetic quantum flux(5.71,6.05,11.71)were significantly higher than the unthinned plot(4.57,4.37,8.94)(P<0.05)and the direct sunlight time(100.33)was significantly longer than that of the unthinned plot(77.21))(P<0.05).4.Correlation analysis results of understory light environment and functional traits on shrubs and grassland showed that the leaf area of Vitex,Jujube,Carex rigescens was significantly positively correlated with the total radiation flux(P<0.05);There is a significant positive correlation between the specific leaf area of green grass and the scattered radiation under the forest(P<0.05),and the specific leaf area of Carex rigescens has a significant positive correlation with the total radiation flux under the forest(P<0.05);There is a significant positive correlation between the total leaf nitrogen content and the organic carbon content of Vitex and Grewia and Carex rigescens leaves with scattered radiation and total radiation flux(P<0.05);the leaf dry matter content is significantly negative with the direct radiation flux and total radiation flux under the forest.Correlation(P<0.05).The organic carbon content and total radiation flux of Vitex and Grewia stems were significantly(P<0.05)and significantly positively correlated(P<0.05),respectively.5.The comparative analysis results of the soil physical and chemical properties of the thinned and unthinned plots show that the soil bulk density(0.96)of the thinned plots is lower than that of the unthinned plots(1.16),but does not reach a significant level(P>0.05),not capillary The total porosity of 14.75%was significantly higher than 11.17%of the unthinned plot(P<0.05).The soil organic matter content of the thinned plot was 36.545 g/kg,which was significantly higher than that of the unthinned plot of 24.492 g/kg(P<0.05),and the distribution range was 25.586～49.67 g/kg and 19.75～29.2 g/kg,respectively.6.Correlation analysis between soil physical and chemical properties and functional traits of dominant shrubs and grass roots showed that there was a significant negative correlation between the total root length of the root system of Vitex and of Grewia and the root volume of Vitex and Jujube and soil bulk density(P<0.05).There was a significant positive correlation between the organic carbon in the roots of Vitex and jujube and the soil organic matter(P<0.05).The total nitrogen content of the roots of Vitex and Grewia was significantly negatively correlated with the soil bulk density,and there was a significant positive correlation between the soil nitrogen content(P<0.05).7.The linear regression fitting results of some main functional traits of the dominant shrubs and grassland under the forest and the light environment indicators under the forest show that the leaf area and specific leaf area of Vitex and Grewia can be linearly correlated with the scattered radiation and total radiant flux under the forest,respectively.Regression relationship(P<0.05),the dry matter content of pole pole and cotton grass leaf can establish a linear regression relationship with understory scattered radiation and understory total radiation,respectively(P<0.05).The total nitrogen content of Vitex and Grewia leaves can establish a linear regression relationship with the total radiant light and direct radiant light under the forest,respectively.The organic carbon content in the stems of Vitex and Grewia can establish a linear regression relationship with the direct radiation and scattered radiation under the forest respectively(P<0.05),which is related to the acceleration of leaf photosynthesis to promote the accumulation of organic matter and the downward transmission,which is stored in the stem.8.The results of the stepwise linear regression analysis of the main functional traits and soil physical and chemical properties of the understory dominant shrubs and grassland showed that the total root length of Vitex was related to the soil non-capillary porosity,total porosity and soil organic carbon,and the root volume and specific root length were related to Soil bulk density,soil non-capillary porosity and capillary porosity,root organic carbon and soil organic carbon and soil total phosphorus have good linear regression fitting effects,with R2 reaching 0.783,0.923,0.930,0.978,respectively,(P<0.01).There is a good linear regression relationship between root dry matter content of Grewia and soil non-capillary porosity and soil organic carbon root volume and soil bulk density(R2=0.753,P<0.05).The total root length,total nitrogen content of Grewia roots and soil bulk density,root volume and soil non-capillary porosity can be described by linear regression models(R2=0.624,0.541,P<0.01,0.05).The total root length of Carex rigescens and total soil nitrogen content and total capillary porosity,root biomass of Carex rigescens and soil bulk density and soil organic carbon,root total nitrogen content and soil total nitrogen can be described by a linear regression model(R2=0.953,0.982,0.741,P<0.01).