横断山脉高山栎组外生菌根侵染特征及其影响因素

Characteristics and influencing factors of ectomycorrhizae infection in Quercus sect.Heterobalanus of Hengduan mountains

【目的】明确高山栎组外生菌根侵染状况及其与各生境因素间的相互关系。【方法】以四川、西藏地区的高山栎组的根系和土壤为研究材料,观察高山栎组外生菌根(Ectomycorrhizae,ECM)的形态特征,测定ECM侵染率,探究ECM侵染率与土壤丛枝菌根真菌(Arbuscular mycorrhizal fungi,AMF)孢子密度、海拔、土壤pH值、土壤有机碳(SOC)、速效钾(AK)、全氮(TN)、全磷(TP)和氮磷比(N∶P)的关系。【结果】研究区内高山栎组ECM形态较为单一,主要为单轴羽状分支和单轴分支,解剖结构观察到ECM真菌在高山栎组根皮层细胞间形成哈蒂氏网,ECM侵染率较高,在51.37%~ 58.68%范围内,侵染强度都为4级,但在树种和生活型水平上均无显著性差异(P>0.05)。高山栎组AMF孢子平均密度为123.92个/g,土壤pH值、SOC、速效钾、TN、TP和N∶P分别为5.32、43.22 g/kg、53.9 g/kg、1.03 g/kg、113.33 mg/kg和5.58。因子分析结果表明8个生境因子对ECM侵染率均有影响,其中ECM侵染率与土壤速效钾和TN含量显著正相关(P<0.05),与其他因素均未显示显著相关关系(P>0.05)。【结论】高山栎组ECM真菌喜弱酸性土壤,土壤中AMF孢子的扩繁不会排斥ECM的侵染,N、K元素是影响ECM侵染的主导因素,另外,不同海拔下高山带高山栎林小生态系统中各生境因素的综合变化也会影响ECM的侵染。当ECM侵染趋于“饱和”状态时会通过反馈改变土壤pH值,但对土壤C素的调节并不明显。

【Objective】To clarify the infection characteristics of the Ectomycorrhizae (ECM) of the Quercus sect.Heterobalanus (QSH) and its interrelationship with various habitat factors.【Method】The roots and soil of QSH in Sichuan and Tibet were used as research materials to observe the morphological characteristics of ECM in QSH,determine the ECM infection rate and analyze the relationship between ECM infection rate and arbuscular mycorrhizal fungi (AMF) spore density,elevation,soil pH,soil organic carbon (SOC),available potassium (AK),total nitrogen (TN),total phosphorus (TP) and N∶P.【Result】The ECM morphology of QSH in the study area relatively single,mainly consisting of single-axis pinnate branches and single-axis branches.The anatomical structure observed that the ECM formed Hartig net between the root cortical cells of the QSH,and the infestation rate of ECM was high,in the range of 51.37%-58.68%,and the infection intensity were all of level 4,but there were no significant difference in the level of species and life forms(P>0.05).The average density of AMF spores was 123.92 per gram,the mean soil pH was 5.32,and the average contents of soil SOC,AK,TN,TP,and N∶P were 5.32,43.22 g/kg,53.9 g/kg,1.03 g/kg,113.33 mg/kg,and 5.58,respectively.Factor analysis showed that all 8 habitat factors had an impact on ECM infection rate,and the ECM infection rate was significantly positively correlated with soil available K and TN content (P<0.05),while no significant correlation was shown with other factors (P>0.05).【Conclusion】TheECM in the QSH plant prefers a weakly acidic environment,and the expansion of AMF spores in the soil does not exclude ECM infection.N and K elements were the dominant factors affecting ECM infection.In addition,the comprehensive changes of various habitat factors in the small ecosystem of QSH forests at different altitudes can also affect ECM infection.Furthermore,the ECM can change soil pH through feedback when its infection tends to a saturated state,but the regulation of soil C is not significant.