岷江上游4个栽培树种细根功能性状垂直分布的差异性

细根(直径≤2 mm)功能性状及垂直分布格局是反映植物对土壤资源吸收策略和影响森林地下生态过程的关键。本研究以岷江上游4个人工林树种连香树(Cercidiphyllum japonicum)、白桦(Betula platyphylla)、华山松(Pinus armandii)和油松(P.tabuliformis)为对象,调查不同海拔树木细根功能性状及其在不同土层间的垂直分布格局,并分析细根功能性状分布与构型之间的相关关系。结果表明:阔叶树种比针叶树种有更大的根长密度、生物量、比根长和比表面积,而直径反之;4个树种细根集中在0~20 cm土层,根长密度和生物量在较高海拔地段均显著大于较低海拔,且均随土壤深度增加而减少,但比根长、比表面积和直径无显著的海拔差异,随土层加深也无明显的垂直变化规律;针阔树种间的细根构型差异显著,但不受海拔差异的影响,阔叶树的细根分支强度与一级根数量显著大于针叶树种;一级根数和根尖密度与比根长以及分根比与根长密度和生物量均呈显著正相关,而分叉与几个细根功能参数均呈负相关;随着土层深度增加,细根总生长量明显减少,但细根资源利用效率和策略不变;5个细根功能性状的垂直分布格局差异明显,且受树种特性影响显著,细根分支构型对其垂直分布及资源获取策略具有显著影响。

Differential vertical distribution of functional traits of fine roots of four cultivated tree species in the upper reaches of Minjiang River.

Functional traits of fine roots(≤2 mm in diameter) and their vertical distribution patterns reflect plant resource absorption strategy and determine belowground ecological processes in forests. A stratified excavation method was used to examine fine-root functional traits,vertical distribution and architecture of four cultivated trees(Cercidiphyllum japonicum,Betula platyphylla,Pinus armandii,and P. tabuliformis). The results showed that root length density,fine root biomass,specific root length(SRL) and specific root surface area(SRA) of broad-leaf species were higher than those of coniferous species and that average diameter of fine root was smaller in broad-leaf species. Root length density and fine root biomass of all the four species decreased significantly with increasing soil depth and concentrated in 0-20 cm soil layer. Moreover,trees grown in high elevation areas had higher root length density and fine root biomass than those in low elevation. There were no significant differences in SRL,SRA and fine root diameter among soil layers or elevations. There were significant differences of fine root architecture among species,with the highest first-order root number,tip density and bifurcation being found in Betula platyphylla,and the highest branching ratio in Cercidiphyllum japonicum. However,fine-root architecture did not differ across the elevations. The SRL was positively correlated with the number of first-order roots and tip density,the branching ratio was positively associated with root length density and fine root biomass,but all functional traits decreased with bifurcations. These results indicated that fine root architecture had significant effects on their vertical distribution and resource acquisition strategy.