| Tree growth is not only related to their own biological characteristics,but also affected by environmental factors.Therefore,it is basis of forest management to study the growth of trees and their response to climate change.Chinese fir(Cunninghamia lanceolata(Lamb.)hook.)is a fast growing coniferous tree species in the subtropical region.Because of its high quality,it plays an important role in the supply of various forest by-products in human society.In this study,using the MBD(manual band dendrometer)to measure the inter-annual radial growth data,and the fixed sample plot to collect the annual radial growth data,the radial growth law of Chinese fir plantation and its respond to climate factors were studied at the Huitong National Field Station for Scientific Observation and Research of Chinese Fir Plantation Ecosystem(Huitong Ecological Station).The main results are as follows:(1)Climate change in the study area:The annual average temperature from 1983 to 2019 showed an upward trend,with a change range of 15.8-17.9℃ and an annual trend rate of 0.25℃/10 a.A significant temperature change point from low to high occurs in 2012;the total annual precipitation in the past 36 years had a change range of 906 mm-1724 mm with a trend rate of 23.7 mm/10 a.The overall trend was upward,but no significant mutation time point was found;the annual average relative humidity fluctuated 76%-91%in 36 years,with a tendency rate of 0.17%/10 a,and no significant mutation time point was found.(2)Inter-annual radial growth of Chinese fir:The radial growth of Chinese fir started in March and stopped in November,and the monthly dynamic changes of the average radial growth rate of Chinese fir all showed a "M" shape,and the peak values appeared in April and August,which showed a double peak curve.There were some differences among different diameter classes of Chinese fir.The larger the diameter class,the more obvious the double peak pattern,the dominant species especially.The annual average monthly cumulative growth curve show a shape of "S",and the Gompertz model was successfully constructed to show the annual radial growth of Chinese fir.The fitting results explain more than 98%of monthly radial increment data.The environmental factors(air temperature,precipitation and relative humidity)had certain influence on the annual growth of Chinese fir.Temperature and precipitation had significant effect on the radial growth of Chinese fir(P<0.001),while relative humidity had weak effect on growth.The annual diameter growth of Chinese fir was the most sensitive to temperature,and the correlation with temperature increased with the diameter class.In spring,autumn and winter,temperature promoted radial growth,while inhibited in hot summer.(3)Annual radial growth of Chinese fir:The diameter distribution of Chinese fir changed from left to right with the increase of forest age.In the young age of forest,the small-diameter trees grow slowly or even in the growth process,but large-diameter trees grow gradually.However,large-diameter trees grow slowly with the increase of forest age.The annual growth rate of Chinese fir increased at the early stage of growth,and then decreased to a steady growth stage.The trees radial cumulative growth of different diameter classes showed that the pressed tree was less than the average tree which was less than the dominant tree.The relationship between annual radial growth and climate factors showed that there was a positive correlation between temperature and annual diameter growth in most months,while the negative correlation between precipitation and growth was more than that between temperature and growth.Relative humidity had a significant role in promoting inter annual radial growth.(4)Relationship between annual and inter-annual radial growth of Chinese fir:The radial growth of Chinese fir showed a similar trend in two time resolution scales.The radial growth of different diameter classes showed dominant tree>average tree>pressed tree on two time resolution scales,and the total amount of inter-annual radial growth was consistent with the law of annual radial growth.There were similarities and differences in the response of radial growth to climate factors in two time scales.The air temperature had a positive correlation with the radial direction in two time scales,and the correlation increased with the increased of the diameter class,and the precipitation had a certain after effect on growth,which leaded to certain differences between precipitation on annual dynamic growth and annual radial growth.Relative humidity had more influence on the inter annual radial growth.This study provides basic data for the annual and inter-annual radial growth of Chinese fir and for the growth and change of Chinese fir under climate change.In addition,the theoretical basis for the sustainable development,correct prediction and scientific management of subtropical forest ecosystem is provided in this study,which enriches the content of forest ecology. |
PDF Full Text Request