林窗面积对桉树林分内格木生长、形态及生物量分配的影响

Effects of gap size on growth,morphology and biomass distribution of Erythrophleum fordii in Eucalyptus plantation

【目的】研究林窗面积对桉树林分内格木生长、形态及生物量分配的影响,探寻适用于桉树与珍贵树种格木混交的种植方式。【方法】在广西凭祥市热带林业实验中心林区,以桉树人工林内林窗面积分别为96,150,216,294,384和486 m^(2)6种生境中的格木幼树为研究对象,采用随机抽样法,对格木的生长状况、叶片形态、干形和一级枝条特征进行调查分析,并测算取样植株主干、根系、枝条和叶片的生物量。【结果】(1)随着林窗面积增大,格木的胸径、树高、树冠长度、平均冠幅和树冠比率均呈先增加后减小的趋势,其在216和294 m^(2)林窗中生长表现最佳;叶片长度、叶片宽度、平均单叶面积和叶片长宽比均呈减小趋势,但叶片长宽比在各种林窗间无显著差异;比叶面积和叶面积指数则随林窗面积增加而增大。(2)在干形指标方面,216和294 m^(2)林窗明显提高了格木树干的通直度、圆满度并降低了尖削度。(3)格木的一级分枝基径、枝条长度和枝条数量以及枝间距均随林窗面积增大而增加,一级分枝角度的变化与之相反;总体分枝率、逐步分枝率和枝径比均呈现先增大后减小的趋势。(4)格木主干、枝条和叶片生物量均表现为216和294 m^(2)林窗中最大,根系生物量以486 m^(2)林窗中最大;6种林窗生境中,格木主干生物量占全株生物量的比例为42.01%~50.13%,根系占比为22.32%~25.89%,枝条占比为15.18%~18.04%,叶片占比为12.18%~15.33%。【结论】林窗面积对桉树林内格木的生长、叶片和树干形态及生物量分配有明显影响。在桉树与格木混交经营过程中,适宜面积的林窗更有利于格木生长发育及生物量积累,建议将林窗面积控制在200~300 m^(2),以达到促进格木生长和培育高品质木材的目的。

【Objective】This paper studied the effects of gap size on growth,morphology and biomass distribution of Erythrophleum fordii in Eucalyptus plantation to explore suitable planting methods for Eucalyptus and precious tree species-E.fordii.【Method】E.fordii saplings of six forest gaps(96,150,216,294,384 and 486 m^(2))in Eucalyptus plantation on experimental center of tropical forestry of Ping-xiang,Guangxi were studied.Then random sampling method was performed to survey growth,leaf,trunk shape and first-order branches morphological characteristics before plant main trunk,root,branch and leaf biomass were calculated.【Result】(1)With the increase of gap area,the diameter at breast height,tree height,crown length,crown diameter and crown ratio of E.fordii saplings increased first and then decreased with optimal values in types 216 and 294 m^(2).The leaf length,width,single leaf area and leaf length width ratio decreased,and leaf length width ratio showed insignificant differences.The specific leaf area and leaf area index increased with increasing gap area.(2)In terms of trunk shape index,the forest gap types of 216 and 294 m^(2)significantly improved stem straightness and stem fullness,while reduced taperingness.(3)The base diameter,length,number and spacing of first-order branches of E.fordii saplings increased with increasing gap area,while branching angles decreased.The overall bifurcation ratio,stepwise bifurcation ratio and branch diameter ratio increased first and then decreased.(4)The biomasses of main trunk,branch and leaf of E.fordii were the largest in forest gaps 216 and 294 m^(2),and maximum of root was in 486 m^(2).The ratios of main trunk,root,branch and leaf to total biomass were 42.01%-50.13%,22.32%-25.89%,15.18%-18.04%,and 12.18%-15.33%,respectively.【Conclusion】Gap size had significant impacts on growth,leaf morphology,stem form and biomass distribution of E.fordii in Eucalyptus plantation.In mixed Eucalyptus and E.fordii,appropriate forest gap will be beneficial to growth and biomass accumulation of E.fordii.The suggested sizes of forest gap were 200-300 m^(2).