不同水分状况下几种幼树地径日变化研究

目的]研究几种幼树在不同土壤水分条件下的地径变化规律。方法]以油松、侧柏、元宝枫和刺槐为试材,测定了土壤含水率为18.75%1、6.47%、13.13%、9.78%和7.50%时的地径日变化规律。结果]不同水分处理对幼树的地径日变化有显著影响。在土壤含水率为18.75%时,刺槐的日最大收缩量(MDS)最小,为0.144 mm;土壤含水率为7.50%时,其MDS值则增大至0.356 mm。在土壤含水率为16.47%时,元宝枫的MDS值最小,而土壤含水率7.50%时的MDS值最大。在土壤含水率为7.50%时,油松和侧柏地径的MDS值最大,其他各处理水平的MDS值很接近。油松、元宝枫和刺槐晴天的每日最大收缩量比阴天大。结论]不同试材地径的最大值均出现在上午8:00,每日的茎直径最小值出现在午后。

Study on Ground Diameter Diurnal Variation of Several Young Tree under Different Water Conditions

Objective] The aim was to study the ground diameter change law of several young tree under different water contents.Method] With Pinus tabulaeformis,Platycladus orientalis,Acer truncatum and Robinia pseudoacacia as tested materials,the diurnal variation law of ground diameter in the soil with the water content of 18.75%,16.47%,13.13%,9.78% and 7.50% resp.were determined.Result] The treatments with different water contents had a significant influence on the diurnal variation law of ground diameter in several young trees.When the soil water content was 18.75%,the maximum daily shrinkage(MDS) of R.pseudoacacia was the least,being 0.144 mm,and it increased to 0.356 mm when the soil water content was 7.50%.When the soil water content was 16.47%,the MDS value of A.truncatum was the least,while its value was the biggest when the soil water content was 7.50%.When the soil water content was 7.50%,the MDS value of P.tabulaeformi,and P.orientalis was the biggest and the MDS value of several young tree in other treatments was similar.The MDS values of P.tabulaeformis,A.truncatum and R.pseudoacacia in clear day were bigger then that in cloudy day.Conclusion] The maximum of ground diameter of different tested material all appeared at am 8:00 and the minimum stem diameter all appeared in afternoon.