Leaf Traits Of Pear Orchards With Different Planting Years And Their Responses To Soil Nutrients

Plant leaf traits are the adaptive strategies of plants in response to changes in the external environment,and are closely related to the nutrient cycle of the ecosystem.Both are key indicators for exploring the function of the "plant-environment" ecosystem.This study took pear trees with different planting years（10 years,30 years,50 years,100 years,200 years,240 years,280 years,and300 years）in Liangli Town,Dangshan County,Suzhou City,Anhui Province as the research object.Changes of leaf traits,changes of C,N,P contents of "soil-leaf-dead leaves" in pear trees of different ages and their ecological stoichiometry characteristics,to clarify the balance of C,N,and P in the "soil-leaf-dead leaves" system.The stoichiometric ratio pattern of elements reveals the law of element interactions and constraints.The correlation between leaf traits and soil nutrients was explored to further clarify the influence of soil factors on leaf traits,to explore the regulation mechanism of "soil-plant" interaction,and to provide an effective theoretical basis for the planting and management of pear trees in Dangshan County.The main findings of this trial are as follows:（1）There were significant differences in leaf area,chlorophyll content,saturated water content,specific leaf area,dry matter mass and leaf CNP of pear trees in different planting years.The leaf area,chlorophyll content,saturated water content and specific leaf area of pear trees all showed a trend of decreasing to a stable state with the increase of planting years,and the dry matter of leaves showed a continuous increase to a stable state with the increase of planting years.The C content in the leaves of the pear trees with age was 339.15-458.93 g/kg,the N content in the leaves was 6.08-12.13 g/kg,and the P content in the leaves was 0.394-0.535 g/kg;with the increase of the planting years,the C and P in the leaves of the pear trees were It first increased and then decreased to a stable trend,while the leaf N showed a decreasing trend;the ranges of C:N,C:P,and N:P of pear leaves were 32.56-64.06,827.48-940.74,13.06-25.59,respectively,with the planting With the increase of age,the leaf C:N showed a continuous rise to a stable state,and the leaf N:P showed a continuous decline to a stable state,while the leaf C:P did not show a regular change with the increase of age.There was a very significant positive correlation（P<0.01）,and a very significant negative correlation（P<0.01）between leaf C:N and N:P;leaf N and leaf area,specific leaf area reached extremely significant There was a significant correlation between leaf N and chlorophyll,saturated water content and dry matter content（P<0.05）;with the increase of planting years,the change of leaf N content showed a moderate degree of variation,and all the other leaves The trait indicators showed weak degree of variation,indicating that the N content of pear leaves in different planting years was the key indicator affecting leaf traits.A comprehensive comparison of principal component analysis found that leaf area,leaf N content,specific leaf area,saturated water content,and chlorophyll could be used as the main indicators for evaluating leaf functional traits in Lishuwang Park.Through the comparative analysis of N:P,it is concluded that the growth of pear leaves at 10-50 years is limited by P,the growth of pear leaves at 200 years is limited by N,and the growth of pear leaves in other years is double-limited by N and P nutrients.（2）The SOC content of pear tree soil（0 ～ 20 cm）in different planting years was4.23 ～ 9.57 g/kg,TN content was 0.47 ～ 1.09 g/kg,and TP content was 0.60 ～ 0.94g/kg.With the increase of soil SOC,TN,and TP,the contents of soil SOC,TN,and TP showed a state of increasing at first and then tending to be stable,with the maximum value at 280 years and the minimum value at 10 years.The content changes all belong to the weak degree of variation;the soil C:N,C:P and N:P of pear trees in different planting years are 8.53 ～ 9.25,6.51 ～ 8.16,0.76 ～ 0.95 respectively,and the soil C:N,C:P,N: :P has no obvious regular change with the increase of planting years,and it is lower than the measurement ratio of my country’s terrestrial soil ecosystem.The soil SOC,TN and TP of different planting years showed a very significant positive correlation（P<0.01）,and the soil C:P and N:P showed a very significant positive correlation（P<0.01）.The soil nutrient content was generally low according to the soil C,N,P metering ratio.（3）The C content of the dead leaves of pear trees in different planting years was450.2-741.6 g/kg,the N content was 5.73-8.45 g/kg,and the P content was 0.29-0.39g/kg.With the increase of planting years,the overall N content of dead leaves was It showed a decreasing trend,and the P content showed a trend of rising first and then decreasing,and tended to be stable after 240 years.The C content of dead leaves had no obvious regular change with the increase of planting years;P content changes belong to weak degree of variation;with the increase of planting years,the C:N,C:P,N:P of dead leaves are 73.68-113.6,1573.61-2040.32,17.24-26.02,respectively,and the C:N of dead leaves varies with planting.The increase of age showed a trend of first rising and then decreasing,and the maximum value was obtained at 240 years,while the N:P of dead leaves showed a decreasing trend with the increase of planting years,and the maximum value was obtained at 10 years,and C:P did not show regular changes with the increase of planting years;C:N and N:P of dead leaves showed a significant negative correlation（P<0.05）.Compared with the ratio of plant dead leaves in my country and the global terrestrial ecosystem,the C content of the dead leaves of pear trees in Dangshan County is higher,while the N and P contents are at a lower level,and the overall expression is the element pattern of high C and low N and P.Moreover,the C:N and C:P ratios of dead leaves in China and the world were also significantly higher than those in my country and the world,which were limited by N,and the comprehensive performance was not conducive to the decomposition of dead leaves.（4）The C,N and P contents of "leaf-soil-dead leaves" in different planting years were as follows: plant leaves>dead leaves>soil;correlation analysis found that soil SOC,TN,and TP were all factors that significantly affected leaf traits.Linear regression analysis found that soil SOC content was the main factor affecting pear leaf traits.