不同密度杉木林内辐射与叶面积垂直分布对生长的影响

INFLUENCES OF RADIATION AND LEAF AREA VERTICAL DISTRIBUTION ON THE GROWTH OF CHINESE FIR YOUNG PLANTATION WITH DIFFERENT DENSITIES

本文通过对八年生杉木人工林内太阳辐射与叶面积垂直分布的观测与研究,用计算机绘图与计算,得出以下结果:杉木叶面积的垂直分布和叶面积指数与密度有关,冠形因密度增加由圆锥形变为圆柱形,叶面积指数是先上升后下降。杉木林内辐射的消减随密度的增加而加剧,在冠层深3/4处趋于平缓,当郁闭度低于0.85时,林冠下辐射有回升。用累加叶面积指数分层计算林冠消光系数,可减少因叶片分布不均匀而产生的误差。用累计值计算辐射,可简化观测与计算。用辐射吸收率、叶面积指数、杉木个体生物量及年均生物增长量4个指标对杉木林生长作综合评价,八年生杉木林生长的较适宜密度是2m×1m。

A study on the radiation and leaf area vertical distribution in relation to the growth of 8-year-old Chinese fir plantations of 5 densities was conducted. The leaf area vertical distribution and LAI were closely related to stem density. The crown form varies from conic to cylindric with the increase of stem density. The LAI rises at first and then declines with the increase of density. The extinction of radiation sharpened when the crown density increased. The extinction leveled at the depth of 3/4 forest heights from the tops of forest canopies.Calculating the extinction coefficients by means of accumulated leaf area index separately for each crown layer can minimize the errors caused by the irregularity of leaf distribution.Four indices, i. e., absorption of radiation, LAI, biomass of individual tree and averaged annual increment of biomass were used to have a comprehensive evaluation on the growth of Chinese fir of 5 densities. The results showed that the plantation with a stem density of 2m×1 m was the best one among the 5 young plantations.