杉木细根养分捕获模式与可塑性机理

Fine root acclimation to different environmental conditions is crucial for growth and sustainability of forest trees. Relatively small changes in fine root functional traits, such as fine root standing biomass, morphology or mycorrhizal symbiosis, may result in a large change in forest carbon, nutrient and water cycles. Different fine root foraging strategies are adjusted in a fluctuating belowground environment. It is hypothesized that environment factors (latitude, mean annual precipitation, temperature), neighbor plants and microbial community are key roles in regulating fine root foraging strategies in Chinese fir (Cunninghamia lanceolata) forests. In plots and yield control experiments and microcosm experiments, variations of fine root functional traits are investigated by root morphological traits, and the relationship between functional traits and microbial components are calculated by diversity and community structure in arbuscular mycorrhizal fungi (AMF) and rhizospheric microorganisms via fungal DNA barcoding and phospholipid fatty acids (PLFA). Fine root foraging strategies across a latitude gradient are evaluated by extensive foraging strategy and intensive foraging strategy based on fine root functional traits. .Fine root plasticity enables trees to forage for heterogeneous resource patches, which is elucidated by morphological plasticity, physiological plasticity and mycorrhizal plasticity. Under monoculture and mixed culture conditions, morphological plasticity is tested for trade-offs among root foraging scale (total root mass and length of structural roots), precision (ln-ratio of root lengths in resource-rich and resource-poor patches). And physiological plasticity is characterized by measuring nutrient uptake kenetics and metabolomic fingerprint under C input conditions. Mycorrhizal plasticity in responses to the resource patches of root exudates, organic matters and allelochemicals, is assessed by measuring AM morphological traits and mycorrhizal mycelia traits such as AM hyphae length, hyphae density and biomass. Also nutrient transfer between root and patches via mycorrhizal mycelia networks is calculated by 15N signature or elements stoichiometry amount fine root, mycorrhizal mycelia and rhizosperic soil. .The results from these innovative experiments will lead to significant advances in our understanding the mechanisms underlying the impact of fine root functional traits on fine root foraging strategies across the environment gradient. Conducting experiments with fine root plasticity will aid in identifying general patterns in Chinese fir that apply across regional scale. By generating empirical functions, the results also will be useful for understanding the importance of complex studies on respective regulatory mechanisms in changing climate and sustainable production in Chinese fir forests, thereby impacting other areas of science.

细根养分捕获模式与表型可塑性对树木生长和可持续性至关重要。细根功能性状（如生物量,形态特征和菌根共生）相对小的改变足以导致森林生态系统碳、养分和水分循环的巨大变化。为区分环境因子、邻居树种和微生物群落对杉木细根养分捕获的影响，本项目拟采用野外控制实验与模拟实验相结合的技术路线，借助AM真菌DNA条形码和磷脂脂肪酸指纹图谱方法，研究杉木AM真菌多样性和根际微生物群落特征，揭示细根功能性状的环境梯度变异特征及对养分捕获模式的影响机制；对比连栽代际和混交类型对细根养分捕获形态塑性（广布性和精确性）的影响，采用代谢指纹方法评价碳输入方式对细根养分捕获生理塑性的影响；利用15N同位素示踪和生态化学计量学方法解析细根对不同资源斑块的菌根塑性响应以及AM根外菌丝网络介导的养分迁移机制，从功能性状变异特征角度探明杉木细根养分捕获模式与表型可塑性响应机理，为杉木人工林可持续经营提供理论依据和技术支撑。

细根养分捕获模式与表型可塑性对树木生长和可持续性至关重要。细根属性（如形态、构型、化学成分、菌根侵染和寿命等）的微小变化就能显著影响森林生态系统碳、养分和水分循环。本项目聚焦细根属性为基础的养分捕获模式，旨在揭示细根属性特征沿环境梯度变异规律及其对细根养分捕获模式的影响，探明环境因子、邻居树种和微生物群落影响下的杉木细根养分捕获的模式与表型可塑性响应机理，检验根际互惠假设，为拓展植物-微生物间的互作机制研究以及实现杉木人工林可持续经营提供新的思路和理论依据。.为此，项目组系统研究了细根的根系属性与表型可塑性特征，发现杉木属粗细根型种（一级根直径约0.6mm），其主要形态属性指标沿纬度梯度无明显变异，而落叶松细根比根长随纬度升高显著变长具有规律性；发现杉木吸收根属性对管理措施的响应方式不同，而吸收根属性的表型可塑性能解释养分添加和冠层调控对根系养分吸收策略的影响；提出了两种新的细根养分捕获模式——光介导养分捕获策略和养分捕获策略；定量评价了杉木细根养分捕获能力与根系属性可塑性的关系，发现氮磷添加显著改变了杉木细根构型，同时添加氮磷比单独添加氮或磷降低养分捕获能力，杉木细根构型属性特征（二叉分支指数，DBI）与养分捕获能力敏感性具有明显线性负相关性；系统阐述了根际互惠假设，提出了混交促进杉木人工林地力提升的新机制，通过对根系养分捕获模式、微生物群落结构和化感自毒作用比较分析，基于混交促进细根属性改变，提高养分吸收能力，并改善微生物群落结构；促进环二肽等化感物质降解减弱自毒作用等系列结果，结合植物-土壤反馈假说，提出与杉木连栽导致土壤负反馈相反，与阔叶树种混交则产生正反馈效应，即混交有助于形成精度养分捕获模式下的细根功能属性特征，既能促进菌根真菌孢子萌发提高根外菌丝产量和菌丝网络养分捕获能力，又能从混交树种迁移更多养分以促进杉木生长。培养博士生1名和硕士生2名，共同发表10篇研究论文。

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