Radial Growth Of Cunninghamia Lanceolata And Its Response To Climatic Factors

Cunninghamia lanceolata is a common afforestation tree species in China.As one of the fast-growing tree species,it has high economic value.The current researches on Cunninghamia lanceolata mainly focus on tree-ring climatology,lack of physiological mechanism and the study of radial growth dynamics on a short time scale and its relationship with climate factors.In this paper,we used a belt-shaped trunk radial measuring instrument to continuously monitor Cunninghamia lanceolata of different forest ages in Jiangle National Forest Farm,Fujian Province from July 2017 to July 2019.Use the maximum method to extract the daily radial growth,use the Gompertz model to simulate the radial cumulative growth,determine the growth season,and perform correlation analysis and sliding correlation analysis through R software and SPSS software.The results show that:(1)The diurnal radial change dynamics of different forest ages of Cunninghamia lanceolata showed obvious day-night alternation,and the average diurnal radial change regularity between the growing season and the non-growing season was consistent.Temperature is the main factor affecting the difference in the diurnal dynamics of tree species in the north and south.(2)The radial cumulative growth of Cunninghamia lanceolata of different forest ages all experienced the "S"-shaped process of slow growth stage,fast growth stage,and weak growth stage,which coincided with the change process of daily amplitude: weak change stage,strong change stage,and medium change stage.And the cumulative growth of different forest age radii showed a trend of middle-age wood(6.298mm)>young wood(4.28mm)>near mature wood(3.84mm)>mature wood(0.24mm).(3)Using the Gompertz model,it is concluded that the annual growth period of Cunninghamia lanceolata is longer,and the annual growth period of different forest ages gradually shortens with the increase of the forest age,but the start time of the growing season moves backward as the forest age increases.The growth periods are: early February to late October(young forest),late February to late September(middle-age forest),early March to late July(near mature forest).The maximum value method was used to obtain the monthly growth difference of Cunninghamia lanceolata of different forest ages,and the main growth period(April to July)of mature wood was obtained.(4)On a one-day scale,as the forest age increases,the sensitivity of radial growth to meteorological factors decreases,and young trees are more susceptible to precipitation and temperature.Water can promote the radial growth of Cunninghamia lanceolata,and as the time is extended to 7 days,the promotion effect of precipitation on different forest ages increases,and the average temperature of middle-aged wood and near-mature wood shows obvious inhibition.(5)Sliding correlation analysis with a window of 21 days showed that the correlation between the radial growth of different forest ages and meteorological factors is in good agreement.The precipitation at the beginning(3-4 months)and the end(September-October)of the growing season Promote the radial growth of Cunninghamia lanceolata,while precipitation in May and July played the opposite effect.The response of temperature to radial growth also varies within the year.In May,the fastest growth rate,the lowest temperature is the main influencing factor,which can promote the radial growth of Cunninghamia lanceolata.At the beginning of the growing season(end of March and early April)and August The average temperature and the highest temperature will inhibit the radial growth of Cunninghamia lanceolata.Therefore,when managing Cunninghamia lanceolata plantations,the rainfall intensity should be increased at the beginning of the growing season,and the average temperature should be controlled to promote the radial growth of Cunninghamia lanceolata.The study of the radial change characteristics of Cunninghamia lanceolata at different forest ages and its response to meteorological factors provides an important way and foundation for dendrochronology and reconstruction of high-resolution environmental evolution history,and better planning the survival strategies of the monitored tree species at different ages.