亚热带常绿阔叶林11个树种的细根形态及碳氮含量研究

Fine root morphology and carbon and nitrogen contents of 11tree species in subtropical evergreen forest

【目的】研究江西大岗山常绿阔叶次生林中11个树种的细根形态、组织化学元素含量与根序之间的关系。【方法】以大岗山次生林内6个受外生菌根侵染的树种(刨花润楠、小叶青冈、拟赤杨、丝栗栲、檵木和梓木)和5个受内生菌根侵染的树种(山乌桕、深山含笑、杉木、木荷和油桐)为研究对象,采用根序分级法对根系进行分级后,测量并比较各树种前5级根之间根长、比根长及C、N含量的差异。【结果】在细根形态方面,11个树种的根长均表现出随序级升高而增大的趋势,而比根长的表现则相反;在细根C、N含量方面,除3个树种(山乌桕、檵木和梓木)5级根C含量小于4级根、1个树种(油桐)2级根C含量小于1级根外,其余7个树种根组织的C含量均表现为随序级升高而增加;11个树种中除山乌桕外,其余10个树种根组织的N含量均表现为随序级升高而降低;在C/N上,有9个树种的C/N随序级升高而增加,其余2个树种(山乌桕和梓木)4级根的C/N略高于5级根。在不同树种间,同一序级的细根在细根形态和C、N含量上差异明显。6个受外生菌根侵染树种的根长和C、N含量均较5个内生菌根侵染树种大,而比根长以外生菌根侵染树种相对较小。【结论】11个树种前5级根根长、比根长、C含量、N含量和C/N随着序级增加而表现出相似的变化规律,生长在根系先端的1级根根长、C含量和C/N最小,比根长和N含量最大,随着序级的增加,根长、C含量和C/N增加,而比根长和N含量降低。受外生菌根侵染的树种,其根长、C含量和N含量均大于受内生菌根侵染的树种。11个树种之间细根形态和C、N含量存在明显差异,表明不同树种对地下环境的适应策略及对土壤养分的利用效率存在差异。

[Objective] Fine root morphology and relationship between chemical element contents and root orders of 11 tree species in evergreen secondary forest in Dagangshan,Jiangxi Province were studied. [Method] 5 species infected by arbuscular mycorrhizae （AM） （Sapium discolor,Michelia maudiae, Cunninghamia lanceolata, Schima superba and Vernicia fordii） and 6 species infected by ectomycorrhizae （EM） （Machilus pauhoi , Cyclobalanopsis rnyrsini folia , Alniphyllurn fortunei , Castanopsis fargesii , Loropetalum chinense and Catalpa ovata） in the secondary forest in Dagangshan were studied. Each individual root was graded by branching order method. Root length, specific root length, and C and N contents of first five roots of each tree species were determined and compared. [Result] Length of fine roots increased as the increase of root order for all species, while specific root length decreased as the increase of root order. Except that carbon contents in the 5th roots of three species （Sapiurn discolor, Loropetalum chinense and Catalpa ovate） were less than those of the 4th roots and carbon contents of the 2nd root of Vernicia fordii was less than that of the first root,carbon contents of the rest 7 species increased as the increase of root order. Nitrogen contents of 10 out of the 11 species （except Sapiurn discolor） decreased with the increase of root order. C/N of 9 species increased as the increase of root order, while C/N in the 4th roots of Sapium discolor and Catalpa ovate were slightly higher than those of the 5th roots. Fine root morphology and C and N contents in the same order roots had significant differences. Root lengths,and C and N contents of the 6 species infected by ectomycorrhizae were larger than those of the 5 species infected by arbuscular mycorrhizae,while the specific root lengths of the 6 species colonized by ectomycorrhizae were smaller. [Conclusion] Root lengths,specific root lengths,C and N contents and C/N of the first five roots of all species had similar trend. The first roots （in the distal end of a root system） had the lowest root lengths,C contents and C/N,and the largest root lengths and N contents. With the increase of root order, root lengths,C contents and C/N increased, but the root lengths and N contents decreased. Root lengths, and C and N contents of species infected by ectomycorrhizae were larger than those of the species infected by arbuscular mycorrhizae. The obvious differences in fine root morphology and contents of C and N of 11 species indicated that different species had different adaptive strategies to underground environment and use efficiencies of soil nutrient.