广西弄岗喀斯特森林9种主要树种水力结构功能特征及其相关性分析

Analyses on functional characteristics of hydraulic architecture of nine main tree species in karst forest in Nonggang of Guangxi and their correlations

为了解喀斯特地区树种适应水分亏缺生境的内在机制,选择广西弄岗喀斯特森林9种主要树种,分析树种间水力结构及相关性状的差异及相关性。结果显示:供试9种树种间的最大边材比导率、最大叶片比导率、胡伯尔值、木质部导管直径及木材密度存在极显著(P<0.01)差异,其中,海南椴〔Diplodiscus trichospermus(Merrill)Y.Tang〕的最大边材比导率、最大叶片比导率以及木质部导管直径均最大,但胡伯尔值和木材密度最小。干季和湿季,供试9种树种间木质部导水率丧失百分比(PLC)均存在极显著差异,且金丝李(Garcinia paucinervis Chun et How)的PLC值均最高,分别为44.39%和38.92%。除闭花木〔Cleistanthus sumatranus(Miq.)Muell.Arg.〕、海南椴和淡黄金花茶(Camellia flavida Chang)外,其他6种树种PLC值在干季和湿季间无显著(P>0.05)差异,表明喀斯特地区树种耐干旱能力普遍较强。相关性分析结果表明:单叶叶面积与最大边材比导率、木质部导管直径和叶片净光合速率呈极显著(P<0.01)或显著(P<0.05)正相关,但与木材密度呈极显著负相关。综上所述,喀斯特地区木材密度较大的树种虽然耐旱性较强,但木质部水分运输效率会降低,进而使叶片净光合速率降低;反之,木材密度较小的树种虽然有利于木质部水分运输效率提高及碳固定,但是其耐旱性降低;水力结构功能特征间的关系既存在协同也存在一定的权衡。

In order to understand the internal mechanism of tree species in karst area adapting to water deficit habitat,nine main tree species in karst forest in Nonggang of Guangxi were selected,and the differences and correlations of hydraulic architecture and related traits among tree species were analyzed.The results show that there are extremely significant(P<0.01)differences in maximum sapwood specific hydraulic conductivity,maximum leaf specific hydraulic conductivity,Huber value,xylem vessel diameter,and wood density among nine test tree species,in which,maximum sapwood specific hydraulic conductivity,maximum leaf specific hydraulic conductivity,and xylem vessel diameter of Diplodiscus trichospermus(Merrill)Y.Tang are all the largest,while its Huber value and wood density are the smallest.In drought and wet seasons,there are extremely significant differences in percentage loss of xylem hydraulic conductivity(PLC)among nine test tree species,and the PLC values of Garcinia paucinervis Chun et How are all the largest,which are 44.39%and 38.92,respectively.Except Cleistanthus sumatranus(Miq.)Muell.Arg.,D.trichospermus,and Camellia flavida Chang,there are no significant(P>0.05)differences in PLC values of the other six tree species between drought and wet seasons,indicating that tree species in karst area generally possess relatively strong drought tolerance.The correlation analysis result shows that single leaf area shows extremely significant(P<0.01)or significant(P<0.05)positive correlations with maximum sapwood specific hydraulic conductivity,xylem vessel diameter,and leaf net photosynthetic rate,but shows an extremely significant negative correlation with wood density.In conclusion,although tree species with relatively large wood density in karst area possess relatively strong drought tolerance,the water transport efficiency of xylem will decrease,and thus reduce leaf net photosynthetic rate;on the contrary,tree species with relatively small wood density are beneficial to improve water transport efficiency of xylem and carbon fixation,but their drought tolerance are reduced;it is suggested that there are both synergistic and some tradeoff relationships among functional characteristics of hydraulic architecture.