林隙对香樟和枫香幼苗早期生长阶段功能性状的影响

探究林隙对不同需光性树种早期生长特征和功能性状的影响，对揭示林隙微生境影响次生林内幼苗更新机制具有重要意义。以亚热带次生林中耐荫常绿树种香樟和阳性落叶树种枫香幼苗为试验对象，研究大林隙(D/H介于1.5—2.0)、中林隙(D/H介于1.0—1.5)和小林隙(D/H介于0.5—1.0)对不同需光树种幼苗早期(1—3年生)生长特征和功能性状的影响。结果表明：(1)林隙大小对两种幼苗的生长均有显著影响。其中，中林隙可显著促进香樟2—3年生幼苗的生长，大林隙对枫香1—3年生幼苗的生长均具有显著促进作用。(2)对林隙环境因子与幼苗功能性状的关系进行冗余分析表明，香樟幼苗功能性状的变化与林隙土壤有机质含量、水解性氮含量、酸碱度和有效磷含量密切相关，而枫香幼苗功能性状则主要受林隙土壤酸碱度、有机质含量、水解性氮含量、土壤含水率、冠层透光率和土壤有效磷含量的影响。(3)维持较高的根重比、细根比根长、叶碳氮比和叶碳磷比是幼苗应对林隙环境影响的重要生理生态调节机制。

Effect of forest gap on functional traits of Cinnamomum camphora and Liquidambar formosana seedlings at early growth stage

Elucidating the effect of forest gap on early seedlings growth and functional traits among different light-demanding tree species is of great significance to reveal the underlying mechanism by which seedling regeneration is subject to microenvironment of gap in secondary forest. In this study, the seedlings of tree species, including shade-tolerant evergreen (C. camphora) and light-demanding deciduous (L. formosana) species in subtropical secondary forest, were used to study the effect of gap size (large gap, D/H=1.5-2.0; medium gap, D/H=1.0-1.5; small gap, D/H=0.5-1.0) on growth and functional traits at the early seedling stage (1-3 years old). The research results showed that (1) the significant growth of seedlings was observed among gap sizes. The growth of 2, 3-year-old C. camphora seedlings and 1-3-year-old L. formosana seedlings were significantly enhanced when growing in medium gap and big gap, respectively. (2) The relationships between environmental factors of forest gap and functional traits of seedlings were examined by using redundancy analysis. We found that the functional traits of C. camphora seedlings were correlated strongly with soil organic matter, hydrolyzable nitrogen, pH value and available phosphorus in forest gap, whereas the functional traits of L. formosana seedlings were mainly affected by pH value, soil organic matter, hydrolyzable nitrogen, soil water content, light intensity of canopy and available phosphorus. (3) Maintaining the higher root mass ratio, specific root length, leaf carbon to nitrogen ratio and leaf carbon to phosphorus ratio were key ecophysiological traits to reduce the negative impact of environmental change on the seedlings growth in forest gap.