川西亚高山岷江冷杉外生菌根形态随海拔梯度的分化

Differentiation of ectomycorrhizal morphology in Abies faxoniana along an elevation gradient in a subalpine forest of western Sichuan Province,China

外生菌根真菌是一类有助于植物生长及应对环境变化的重要共生真菌类群。深入认识外生菌根特征有助于理解植物对环境变化的响应规律。本研究在四川省卧龙自然保护区巴郎山脉设置海拔2850、3000、3194、3413和3593 m 5个样地,利用中心象限法进行土块样品(10 cm×10 cm×10 cm)采集,通过分析各海拔每土块中岷江冷杉外生菌根形态个数、形态多样性及养分获取类型等指标,研究岷江冷杉外生菌根形态特性随海拔的变异特征及土壤环境因子的作用。结果表明:1)菌根形态为橘黄色或橘色、单轴羽状分支或不分支、菌套表面光滑、无或少见外延物、根尖直筒型或膨大的菌根类型是卧龙自然保护区岷江冷杉外生菌根的主要形态类型。该形态类型在研究区内的侵染率最高,为12.4%;2)随着海拔的升高,岷江冷杉外生菌根形态多样性下降,每土块内的形态个数减少;3)单因素方差分析结果表明,不同海拔上无外延菌丝或极少外延菌丝的紧密接触类型(CE)和短距离养分获取类型(SDE)外生菌根侵染率有显著差异,CE类型外生菌根侵染率随着海拔的升高而增加;4)土壤环境因子对岷江冷杉外生菌根形态在海拔上的变异有一定的影响,冗余分析(RDA)表明,土壤全氮含量、全磷含量、土壤温度、土壤含水率、pH值及酸性磷酸酶活性对岷江冷杉外生菌根形态在海拔上的变异有显著影响,其中土壤全氮含量和土壤温度的影响最大,分别解释了岷江冷杉形态特征变异的5.4%和4.9%。本研究揭示了岷江冷杉外生菌根形态形成在海拔上的差异,为进一步研究亚高山针叶树种菌根策略对环境变化的响应机制提供了科学依据。

Ectomycorrhizal fungi are an important group of symbiotic fungi beneficial to plant growth and their environmental adaptation.An explicit clarification of the trait of ectomycorrhizal fungi would facilitate our understanding of plant responses to environmental change.We set up sampling plots at five elevations(2850,3000,3194,3413,3593 m)in the Balong Mountain within the Wolong Nature Reserve of Sichuan Province,and collected cubic soil samples(10 cm×10 cm×10 cm)from those plots by point centered quarter method.Based on examination of the morphological types and diversity of ectomycorrhizal roots of Abies faxoniana in each soil sample,we examined the variations in morphological traits of ectomycorrhizal roots of A.faxoniana along the elevational gra-dient and the effects of soil environmental factors.Results showed that:1)The major ectomycorrhizae of A.faxoniana in Wolong Nature Reserve was orange or yellow in color,with smooth mantle and no or few extensional hyphae,and cylindric or inflated root tips.This type of ectomycorrhizae occurred with highest rate of colonization(12.4%)in the study area.2)With the increases of elevation,the morphological diversity of ectomycorrhizae in A.faxoniana declined and the morphological types per cubic soil sample significantly decreased.3)There were significant differences between the ectomycorrhizae of contact exploration type(CE)and short distance exploration type(SDE)at different elevations,while the colonization rate of CE increased significantly with elevation.4)Soil factors drove the variations of ectomycorrhizal morphology in A.faxoniana along the elevational gradient.Redundancy analysis(RDA)showed that soil total nitrogen(TN),soil temperature(Ts),soil water content(SWC),pH,soil acid phosphatase(ACP)and soil total phosphorus(TP)had significant effects on ectomycorrhizal morphology in A.faxoniana,among which TN and Ts being the greatest and explaining 5.4%and 4.9%of the total variations.Our results clari-fied the variations in the occurrence of ectomycorrhizal morphology in A.faxoniana along elevational gradient,which provided scientific evidence for further studying the mechanisms underlying the responses to environmental changes in mycorrhizal strategy in coniferous species of subalpine forests.