Leaf Expansion Process And Leaf Area Dynamic Of Main Shrub Species In Broad-leaved Korean Pine Forest In Changbai Mountain

Broad-leaved Korean pine forest is the most typical type of forest vegetation in the mountainous areas of eastern Northeast China.The large altitude difference in the Changbai Mountain area has created diverse and rich vegetation types,showing a typical vertical zonal vegetation distribution,and the community structure is stable and complex.The diversity of its phenology has always been concerned by academia.In this study,the main shrub species of broad-leaved Korean pine forest in Changbai Mountain was taken as the research object.Through long-term phenological observation,the leaf spreading process and the dynamic changes of leaf area of 20 shrub species in broad-leaved Korean pine forest were studied.The process of fitting to the scale of the entire community.The leaf spreading process and the regression model of leaf are used to predict the seasonal dynamics of community leaf area.This study can help us understand the phenological diversity of broad-leaved Korean pine forests in Changbai Mountains,and explain the mechanism by which different tree species can coexist under the same habitat conditions.The main findings are as follows:(1)This study established a single leaf area model of 20 shrub species.The regression model using the geometric mean of leaf length and leaf width as the independent variable fit has the highest accuracy,this parameter is applicable to the change process of the leaves of each tree species,and the actual use effect is the best.Combined with the branch relationship of each tree species,the allogeneic growth model was used to fit the base diameter-leaf area model of 20 shrub species,all of which reached extremely significant levels.(2)The leaf emergence time of shrub species in broad-leaved Korean pine forest is concentrated in late April,there are 3 kind of leaf emergence patterns: flushing emergence,succeeding emergence and intermittent emergence.Among them,the species with the explosive leaf emergence pattern is the most(13 species),the continuous leaf emergence is the second(6 species),and the least is the intermittent leaf emergence(1 species).The start time of leaf expansion is concentrated at the end of April,and the average growing degree days(GDD)is 59.8 ?,the growing degree hours(GDH)was 2348.8 ?.It takes an average of 28.9 days to complete the leaf expansion,and the GDD required is 253.4 ?.the growing degree hours(GDH)was 6004.2 ?.According to the observation of the leaf spreading process of various tree species,it is found that the leaf spreading process of various tree species conforms to the "S" curve of the logical sequence,and generally presents the "slow-fast-slow" leaf spreading mode;judging from the fitting model of the tree species leaf spreading process,all three models reached extremely significant levels.The model of leaf expansion process based on calendar day(DOY)fitting has the highest accuracy,but the model based on GDD fitting has convenient data acquisition,small workload and high stability,which is the best model for fitting leaf expansion process.(3)The leaf expansion in community began in April 23.At this time,the effective accumulated temperature GDD is 54.1 ?,and the GDH is 2095.1 ?,the change ended on June 19,The duration of leaf expansion is 57 d,and the required heat is 489.2 ?;The broadening process of the broad-leaved Korean pine forest shrub species community showed an "S" curve.Therefore,the leaf spreading process of the community is a "slow fast slow balance" model;Based on the calendar days(DOY)and growth length days(GDD),the two types of community leaf spreading process models conform to the "S" type Bi Dose Resp growth curve.Considering the stability and universality of the model,the community leaf spreading process model based on GDD was the best model.