Institute of Ecology and Earth Sciences, University of Tartu, 46 Vanemuise, Tartu, 51014, Estonia.
Department of Forest Sciences, University of Helsinki, Helsinki, 00014, Finland.
New Phytol. 2017 Aug;215(3):977-991. doi: 10.1111/nph.14643. Epub 2017 Jun 6.
The tree root-mycorhizosphere plays a key role in resource uptake, but also in the adaptation of forests to changing environments. The adaptive foraging mechanisms of ectomycorrhizal (EcM) and fine roots of Picea abies, Pinus sylvestris and Betula pendula were evaluated along a gradient from temperate to subarctic boreal forest (38 sites between latitudes 48°N and 69°N) in Europe. Variables describing tree resource uptake structures and processes (absorptive fine root biomass and morphology, nitrogen (N) concentration in absorptive roots, extramatrical mycelium (EMM) biomass, community structure of root-associated EcM fungi, soil and rhizosphere bacteria) were used to analyse relationships between root system functional traits and climate, soil and stand characteristics. Absorptive fine root biomass per stand basal area increased significantly from temperate to boreal forests, coinciding with longer and thinner root tips with higher tissue density, smaller EMM biomass per root length and a shift in soil microbial community structure. The soil carbon (C) : N ratio was found to explain most of the variability in absorptive fine root and EMM biomass, root tissue density, N concentration and rhizosphere bacterial community structure. We suggest a concept of absorptive fine root foraging strategies involving both qualitative and quantitative changes in the root-mycorrhiza-bacteria continuum along climate and soil C : N gradients.
根系-菌根共生体在资源获取中起着关键作用，但也在森林适应不断变化的环境中起着关键作用。本研究沿着从温带到亚北极的欧洲北方森林（北纬 48°至 69°之间的 38 个地点）的梯度，评估了欧洲云杉、欧洲赤松和欧洲白桦的外生菌根（EcM）和细根的适应觅食机制。描述树木资源获取结构和过程的变量（吸收性细根生物量和形态、吸收根中的氮浓度、外生菌丝体（EMM）生物量、根相关 EcM 真菌群落结构、土壤和根际细菌）用于分析根系功能特征与气候、土壤和林分特征之间的关系。每单位林分基面积的吸收性细根生物量从温带森林显著增加到北方森林，同时伴随着根尖端更长、更细、组织密度更高、每根长度的 EMM 生物量更小以及土壤微生物群落结构的变化。发现土壤碳（C）：氮（N）比解释了吸收性细根和 EMM 生物量、根组织密度、N 浓度和根际细菌群落结构变化的大部分可变性。我们提出了一个吸收性细根觅食策略的概念，涉及沿气候和土壤 C：N 梯度的根-菌根-细菌连续体的定性和定量变化。
