| Broad-leaved Korean pine(Pinus koraiensis)forest is a climax community in the eastern part of Northeast China.The regeneration process of Pinus koraiensis has always been concerned by the academia.The secondary forest formed after the disturbance of broad-leaved Korean pine forest is broad-leaved forest with Betula platyphylla and Populus davidiana as the dominant species.Studies have shown that Betula-Populus and broad-leaved forests are ideal sites for regeneration of Pinus koraiensis.Exploring the regenerationd environment of Pinus koraiensis will provide a valuable theoretical basis for revealing the survival strategies of Pinus koraiensis populations.In this study,takes the Betula-Populus forest as the object,and relies on digital information technology and photosynthetically active radiation instrument to deeply analyze the seasonal dynamics of forest light in Changbai Mountain.The leaf expansion process and seasonal dynamics of canopy in 25 species of woody plants of Betula-Populus forest were studied.The changes in number of leaves,single leaf area and total leaf area were recorded.A comparative study of leaf area for distribution and dynamic change of Betula-Populus.The leaf level from the measured results were attempts to stand on the plant and the entire horizontal scaling.The seasonal dynamics of the leaf area index of the community were predicted by establishing a regression model of the relationship between leaf expansion,leaf area index and temperature.The canopy photographs collected continuously using full-lens shots were used to analyze the changes in the leaf area index at the community scale.Mutual conversion and mutual verification between different scales to dynamically establish reliable prediction tools for monitoring canopy leaf area.The purpose is to reveal the canopy dynamics and phenological setting of main plants in deciduous broad-leaved forests of Changbai Mountain,and to provide basis for explaining the strategies for using light in different tree species.The main findings are as follows:(1)A single-leaf area model of 25 tree species was established by using the geometric mean of leaf length,leaf width and leaf length and width as independent variables,respectively.The mathematical model of leaf area fitted by the geometric mean of leaf length and width is the most effective,and it is the best effective parameter for rapid determination of leaf area in the field.There was a significant allometric relationship between shoots and their number of leaves,R2 reached 0.956-0.995.The allometry equation can describe the relationship between the breast diameter or base diameter and leaf area.The breast diameter or base diameter can be used as the only variable to establish a single woody area model for 16 tree species.(2)The starting time of leaf emergence was mainly concentrated in the beginning of May in Betula-Populus forest,and there were 3 kinds of leaf emergence patterns,ie,flushing emergence(19 species),suceeding emergence(4 species)and intermittent emergence(1 species);The earlier the start of leaf emergence,the earlier the end,and the start time of leaf emergence is not related to the duration time;The leaf emergence rate was affected by the temperature,the higher the temperature before leaf emergence,the faster the leaf emergence rate and the more species leaf emergence.Compared with canopy trees,the understory shrubs leaf emergence is early and the longer the duration of leaf emergence lasted;The compound leaf plants are later than the single-leaf plants and have a short duration.The leaf extension duration is not related to the leaf expansion time,and it is positively related to the leaf expansion end time.Broad-leaved tree species have a short duration of extension,a relatively high growth rate,and coniferous species of Korean pine have a long extension time and a relatively low growth rate.Compared with shrub species,the canopy species had shorter duration of leaf extension,higher relative growth rate,and larger single leaf area.The growth trend of the leaves is mainly the "S" pattern of logical growth;There is a positive correlation between the expansion of the blades and the temperature,the higher the temperature,the faster the blade expansion rate.On the whole,leaf broadleaf species were mainly concentrated in early May,with a growth degree days(GDD)of 174.4℃,hourly growth degree hours(GDH)at 4019℃,and average leaf size.For a duration of 33.9 days,the required heat GDD is 315.4℃.The required GDH is 6603.3℃.Through the fitting of the tree leaf development process model,we found that the model based on the GDH fitting was the best,followed by the GDD;from the process model of the leaf spreading,92%of the tree species leafing process conformed to the "S" logic The growth curve,while 8%of tree species meet the BiSoseResp growth curve of the double "S" type.(3)Establish a regression model of the relationship between leaf area index and temperature,not only can directly determine the seasonal variation of leaf area index(LAI)of broad-leaved mixed forest,but also has a predictive effect on the change of leaf area..At the same time,consistent results have been obtained between the leaf area index measured by the optical instrument method and the leaf area index that should be directly measured in this paper.Therefore,the method combining leaf opening survey with the DBH-leaf area model can be used as an estimating forest.The effective method of leaf area index and its dynamic change.There was a significant negative correlation between the leaf area index of the community and the canopy transmittance(k=-8.4094,R2=0.98176,p<0.001).That is,with the development of the leaf,the leaf area of the community was increasing.The light transmittance of the community layer is lower,and the photosynthetically active radiation in the forest is getting smaller and smaller.At the same time,there was also a significant negative correlation between leaf area index and canopy width(k=-0.01478,R2=0.98145,p<0.001). |
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