A computer program for characterizing root system branching patterns

A computer program is presented which measures the length, branching patterns and distribution of link length within a root system. The program skeletonizes digitized images of root systems, loads these images into a binary tree data structure and uses this data structure to characterize the root systems. Measurements of the root length and topological parameters of root systems of Senecio vulgaris made by hand and by computer program were linearly related, with r² values greater than 0.99 in all cases.     

Estimation of tree root lengths using fractal branching rules: a comparison with soil coring for Grevillea robusta

Previous theoretical research has suggested that lengths of tree roots can be estimated on the basis of their branching characteristics, if branching has a fractal pattern that is independent of root diameter. This theory and its underlying assumptions was tested for Grevillea robusta trees at a site in Kenya by comparing estimates of root length from conventional soil coring and the output of a fractal branching algorithm. The trees were in a 4-year-old stand established on a 3 × 4 m planting grid. Root lengths (L _r) in four units of the planting grid were estimated by soil coring. Branching characteristics determined by examination of 32 excavated roots from 16 trees were: The number of branches at each branching point; the length of links between branching points (L _l); the diameter of root tips; and parameters which describe the change in diameter at each branching point. Each was found to be independent of root size. These data were used to parameterise a branching algorithm, which was then used to estimate numbers of root links in the four grid units (n _l) from root diameters at the bases of the four trees at the corners of each unit. Root lengths, from L _r = n₁ L₁, severely underestimated L _r. This discrepancy probably resulted from inaccuracy in the parameterisation of the branching algorithm, as output from the algorithm was very sensitive to small changes in parameter values. Use of fractal branching rules alone to estimate roots length does not appear possible unless the algorithm is calibrated to adjust for errors in parameter estimation. Calibration can be achieved by calculation of an 'effective link length', L ^eff ₁, from L _r/n _l, where L _r is measured by a reference method such as soil coring.     

Accurate root length measurement by image analysis

Algorithms for estimating root length by image analysis should lead to results that have no systematic error (bias), be insensitive to preferential root orientation, valid across a wide range of sample sizes and adjust for overlap between roots in samples, to reduce the effort needed in spreading out root systems. We propose a new algorithm that forms a compromise between small bias and robustness (insensitivity to variation in sample size and preferential root orientation), and provide a simple way of dealing with root overlap. Image analysis was performed on a Macintosh computer using the public domain NIH Image program. The digital image of the root was processed to get the thinned image (skeleton). The numbers of orthogonally and diagonally connected pairs of pixels (N _o and N _d, respectively) in the skeleton were counted separately and used for length (L) calculation. A new length calculation equation was introduced so that the effect of orientation on length calculation was minimized; L=[N d ²+(N _d+N _o/2)²]^1/2+N _o/2. The maximum error due to orientation of a single line was evaluated for an ideal line, and the analysis revealed that the new equation was less affected by orientation than previous equations. Copper wire and rice (Oryza sativa L.) roots containing both primary and fine secondary root were measured manually and with image analysis. The two methods showed good agreement within 1.5%. The proposed image analysis method yielded length estimates with CV from 0.23 to 0.88%, which was lower than the CVs of the line-intersect method. Moreover, the lengths of overlapping samples were calculated correctly because the image analysis method distinguished an overlapping pixel from a thinned image, while the calculation with the line-intersect method showed underestimation because overlaps were not considered in that method. This revised version was published online in June 2006 with corrections to the Cover Date.     

Influence of root density on the critical soil water potential

Estimation of root water uptake in crops is important for making many other agricultural predictions. This estimation often involves two assumptions: (1) that a critical soil water potential exists which is constant for a given combination of soil and crop and which does not depend on root length density, and (2) that the local root water uptake at given soil water potential is proportional to root length density. Recent results of both mathematical modeling and computer tomography show that these assumptions may not be valid when the soil water potential is averaged over a volume of soil containing roots. We tested these assumptions for plants with distinctly different root systems. Root water uptake rates and the critical soil water potential values were determined in several adjacent soil layers for horse bean (Vicia faba) and oat (Avena sativa) grown in lysimeters, and for field-grown cotton (Gossypium L.), maize (Zea mays) and alfalfa (Medicago sativa L.) crops. Root water uptake was calculated from the water balance of each layer in lysimeters. Water uptake rate was proportional to root length density at high soil water potentials, for both horse bean and oat plants, but root water uptake did not depend on root density for horse bean at potentials lower than −25 kPa. We observed a linear dependency of a critical soil water potential on the logarithm of root length density for all plants studied. Soil texture modified the critical water potential values, but not the linearity of the relationship. B E Clothier Section editor     

星毛委陵菜根系构型对草原退化的生态适应

对轻度、中度、重度和极度退化的草原群落中星毛委陵菜(Potentilla acaulis)根系构型参数及相应的土壤水分、容重和硬度等指标进行了分析, 以研究星毛委陵菜根系构型对草原退化的生态适应性。结果表明: 1)在以大针茅(Stipa grandis)为建群种的典型草原中, 随着退化程度的加剧, 星毛委陵菜在群落中的作用逐渐增强, 其根幅、根深、一级垂向根数、分蘖子株数和水平分蘖根长度显著增加; 2)根表面积、二级侧根长度、总根长和根分叉数4个根系构型参数是解释星毛委陵菜根系构型对草原退化生态适应的首选指标, 解释力依次减小, 累计贡献率为92.34%; 3)直径2 mm以下的根系对单株系星毛委陵菜的根表面积和总根长影响显著; 4)阔腰倒锥体三维根系构型是星毛委陵菜适应草原退化并使之成为建群种的优势构型。     

亚热带6种树种细根序级结构和形态特征

以福建省建瓯市万木林自然保护区内占优势的6种天然林树种(沉水樟Cinnamomum micranthum,CIM;观光木Tsoongiodendron odorum Chun,TOC;浙江桂Cinnamomum chekiangense,CIC;罗浮栲Castanopsis fabri,CAF;细柄阿丁枫Altingiagracilipes,ALG;米槠Castanopsis carlesii,CAC)为研究对象,对其1—5级细根的结构,形态特征及生物量进行了分析。结果表明:沉水樟,细柄阿丁枫和米槠细根分支比表现出在1,2级(4倍以上)明显大于其它序级(3倍左右);其余3种树种则是在3,4级的细根分支比最大,其中浙江桂达到8.65倍,其它序级则大致为3倍左右。6种树种1,2级细根数量占到总数的70%—90%。6种树种细根直径,根长,组织密度随序级升高逐渐增大,比根长减小,生物量未表现出一致的变化规律,6种树种生物量主要集中在高级根部分。方差分析表明,树种对细根分支比例有显著影响(P<0.05),浙江桂和米槠细根分支水平对分支比例有极显著影响(P<0.01),其余4种树种分支水平对分支比例有显著影响(P<0.05),树种和分支水平的交互作用对6种树种细根分支比均有极显著的影响(P<0.01);树种对细根根长,直径以及生物量均有极显著影响(P<0.01),对比根长有显著影响(P<0.05),而对组织密度的影响则不显著(P>0.05);树种和序级的交互作用对细根根长,直径以及生物量均有极显著影响(P<0.01),对组织密度有显著影响(P<0.05),对比根长影响不显著(P>0.05)。序级对6种树种细根根长,直径,比根长以及生物量的影响并未达到一致,对6种树种细根组织密度有极显著影响(P<0.01)。树种间1—4级根的比根长变异主要由组织密度引起,而5级根的比根长变异则由直径引起,同时在1级根中组织密度与直径呈现出权衡的关系。6种树种细根数量,直径,根长,比根长,组织密度以及生物量与序级之间回归分析发现它们与序级之间具有指数函数,线性函数,二次函数,三次函数或者幂函数关系。     

干旱条件下接种AM真菌对小马鞍羊蹄甲幼苗根系的影响

为了探讨岷江干旱河谷丛枝菌根真菌(AMF)对寄主植物幼苗根系的影响,通过接种购买的AMF摩西球囊霉菌(Funneliformis mosseae)到优势乡土灌木小马鞍羊蹄甲(Bauhinia faberi var.microphylla)幼苗,在重度、中度和轻度干旱条件下培养3个月,研究不同干旱条件下AMF对幼苗根系形态特征、结构特征、功能性状的影响。方差分析结果表明:(1)3种干旱胁迫条件下,接菌均显著增加了幼苗的根总长、根表面积、根分枝数、根尖数(P0.001),在中度胁迫和轻度胁迫下,接菌显著促进根鲜重、根体积的增加(P0.001),轻度胁迫条件下接菌幼苗的根鲜重、根总长、根表面积、根体积、根尖数最高并显著高于其它处理,但接菌与未接菌的根平均直径之间没有显著差异;(2)接菌幼苗根系趋向于叉状分支结构,在重度胁迫时,叉状分支趋势更显著(P0.001);(3)接菌幼苗的根比例都显著小于未接菌的,但幼苗比根长不存在显著差异。相关分析结果表明:菌根侵染率与根鲜重、根总长、根表面积、根体积、根分枝数、根尖数呈极显著正相关(P0.001),与拓扑指数、根比例呈极显著负相关(P0.001)。研究表明,在干旱条件下,AMF虽然没有提高生长初期的根系的吸收效率,但接种AMF显著影响幼苗根系形态特征和结构特征,更利于植物适应干旱环境,并且AMF对幼苗根系的促生作用随着干旱胁迫程度减轻而提高。     

Relationships between root diameter,root length and root branching along lateral roots in adult,field-grown maize

Background and Aims Root diameter, especially apical diameter, plays an important role in root development and function. The variation in diameter between roots, and along roots, affects root structure and thus the root system’s overall foraging performance. However, the effect of diameter variation on root elongation, branching and topological connections has not been examined systematically in a population of high-order roots, nor along the roots, especially for mature plants grown in the field.Methods A method combining both excavation and analysis was applied to extract and quantify root architectural traits of adult, field-grown maize plants. The relationships between root diameter and other root architectural characteristics are analysed for two maize cultivars.Key Results The basal diameter of the lateral roots (orders 1–3) was highly variable. Basal diameter was partly determined by the diameter of the bearing segment. Basal diameter defined a potential root length, but the lengths of most roots fell far short of this. This was explained partly by differences in the pattern of diameter change along roots. Diameter tended to decrease along most roots, with the steepness of the gradient of decrease depending on basal diameter. The longest roots were those that maintained (or sometimes increased) their diameters during elongation. The branching density (cm^–1) of laterals was also determined by the diameter of the bearing segment. However, the location of this bearing segment along the mother root was also involved – intermediate positions were associated with higher densities of laterals.Conclusions The method used here allows us to obtain very detailed records of the geometry and topology of a complex root system. Basal diameter and the pattern of diameter change along a root were associated with its final length. These relationships are especially useful in simulations of root elongation and branching in source–sink models.     

Plant growth promoting rhizhobacteria (PGPR)-mediated root proliferation in black pepper (Piper nigrum L.) as evidenced through GS Root software

Abstract

Pseudomonas fluorescens strains which are proven biocontrol agents in black pepper against foot rot (caused by Phytophthora capsici ) were also found to enhance root proliferation and fibre root production. Experiments conducted in the greenhouse with five efficient strains of P. fluorescens (IISR-6, IISR-8, IISR-11, IISR-13 and IISR-51) showed that the bacterial strains could significantly increase the root biomass of the plants (30 – 135%). Parameters for total root length, root area and root tips were estimated by scanning the entire root system and analysis through GS Root® software (PP systems, Winterstreet, USA). All the strains increased the root length in the treated plants (12 – 127%), the highest being with IISR-6, which was on a par with IISR-11 and IISR-51. A similar trend was observed with the total root area after bacterization (43 – 200%). The P. fluorescens treated plants had a higher number of feeder roots as evidenced by the increased number of root tips (82 – 137%). The enhanced growth parameters upon root bacterization could be corroborated with the production of the plant growth hormones IAA & GA by the bacterial strains and their P-solubilization potential.     

Consequences of root growth kinetics and vascular structure on the distribution of lateral roots

It has been proposed that the acropetal initiation of lateral roots is a built‐in process specified as part of the general process of cell division and differentiation in the parent root tip. Conversely, it is commonly reported that root branching is essentially a variable feature. In the present study, the interlateral distance along the parent root has been investigated using three banana varieties (Musa spp.) grown in two substrates. The pattern of lateral root initiation was obscured by variations of root growth patterns and vascular structure among roots, genotypes and substrates. A framework model is formulated showing the influence of growth pattern and vascular structure on branching density. The model raises a distinction between growth components which should not affect the branching density (i.e. rate of cell division) and which may affect it (i.e. size of mature cells and number of transverse divisions performed by cells executing their trajectory in the meristem). It appears also that lateral root density and root growth rate might be independently modulated by appropriate changes of root growth patterns, in banana and presumably many other taxa.     

华北山地6个外生菌根树种的根属性及其与菌根侵染率的关系

该研究以共存于同一暖温带森林的6个外生菌根(ECM)树种为研究对象,测定分析不同根序(1～5级)和功能根系(吸收细根和运输细根)的主要形态和构型属性及ECM侵染率,探究不同外生菌根树种的根属性变异模式及其与菌根真菌侵染程度的关系。结果表明:(1)随着根序的增加,不同树种根直径和单根长度均增加,而比根长和根分支强度均降低;根属性在同一根序下均存在显著的种间差异,尤其是2个裸子植物(落叶松和油松)的根直径较其他4个被子植物大。(2)同一树种的所有根属性在吸收细根和运输细根之间均有显著差异;吸收细根和运输细根的根直径、比根长和根组织密度在树种间均存在显著差异,而其单根长度和根分支强度在树种间无显著差异。(3)ECM侵染率以落叶松最高,千金榆和白桦最低,且与根尖直径呈显著正相关关系,与根尖比根长呈显著负相关关系。研究发现,基于根序或者功能根系,根属性在种间的变异模式不完全一致,单根长度和根分支强度在两个功能根系中均没有表现出显著的种间差异;吸收细根的比根长和根分支强度的变异系数较大,对环境变化有较敏感的响应;古老树种的根直径相对较粗,对菌根真菌的依赖性更高。     

Fine root architecture, morphology, and biomass of different branch orders of two Chinese temperate tree species

We have limited understanding of architecture and morphology of fine root systems in large woody trees. This study investigated architecture, morphology, and biomass of different fine root branch orders of two temperate tree species from Northeastern China—Larix gmelinii Rupr and Fraxinus mandshurica Rupr —by sampling up to five fine root branch orders three times during the 2003 growing season from two soil depths (i.e., 0–10 and.10–20 cm). Branching ratio (R _b) differed with the level of branching: R _b values from the fifth to the second order of branching were approximately three in both species, but markedly higher for the first two orders of branching, reaching a value of 10.4 for L. gmelinii and 18.6 for F. mandshurica. Fine root diameter, length, SRL and root length density not only had systematic changes with root order, but also varied significantly with season and soil depth. Total biomass per order did not change systematically with branch order. Compared to the second, third and/or fourth order, the first order roots exhibited higher biomass throughout the growing season and soil depths, a pattern related to consistently higher R _b values for the first two orders of branching than the other levels of branching. Moreover, the differences in architecture and morphology across order, season, and soil depth between the two species were consistent with the morphological disparity between gymnosperms and angiosperms reported previously. The results of this study suggest that root architecture and morphology, especially those of the first order roots, should be important for understanding the complexity and multi-functionality of tree fine roots with respect to root nutrient and water uptake, and fine root dynamics in forest ecosystems.     

种子散布位置对格氏栲幼苗根系形态及生长特征的影响

种子从母株掉落于地面萌发后,其根系在不同散布位置(凋落物上层、土壤表层和凋落物下层)的生长形态影响幼苗定居及建成,而目前对其根系形态及生长特征的了解并不充分,限制了对幼苗根系在不同散布下适应策略的理解。为此,以格氏栲(Castanopsis kawakamii)为研究对象,通过模拟种子在凋落物中位置,设置凋落物上层(种子下层铺垫2 cm和4 cm凋落物,U2和U4处理)、土壤表层与凋落物下层(种子上层覆盖0、2、4、6 cm和8 cm凋落物,CK、D2、D4、D6和D8处理)等3种散布,探讨不同散布位置对格氏栲幼苗根系9个生长指标的影响。结果表明：(1)种子散布位置对幼苗根干物质质量具有显著影响,D2处理达最大值。(2)D2处理的幼苗根长、根表面积、根尖数、分枝数和比根长高于其它处理;根系平均直径在D6处理达最大值。(3)相关分析表明根长、根表面积、根尖数、分枝数和比根长与根系平均直径呈显著负相关关系。(4)对根系9个生长指标提取主成分后聚类为4个类群,D2与D4处理各划分一类;U2与U4处理划分一类,其余三个处理划分一类。综上所述,凋落物浅层覆盖(D2处理)适宜格氏栲根系生长;凋落物...     

外生菌根菌对油松幼苗抗氧化酶活性及根系构型的影响

研究盆栽条件下,接种褐环乳牛肝菌(Suillus luteus)和红汁乳菇(Lactarius hatsudake)对油松(Pinus tabulaeformis)苗木生长,抗氧化酶活性和根系构型的影响。结果表明:(1)褐环乳牛肝菌和红汁乳菇均可与油松合成外生菌根,并显著提高苗木的苗高、地径、鲜重和干重。(2)接种褐环乳牛肝菌苗木针叶抗氧化酶(SOD、CAT、POD)活性分别比接种红汁乳菇苗木高14.77%、20.77%、34.68%;接种褐环乳牛肝菌苗木根系抗氧化酶(SOD、CAT、POD)活性分别比接种红汁乳菇苗木高8.54%,4.34%,33.31%;接种处理苗木抗氧化酶活性均显著高于不接种处理。接种处理苗木根长、表面积、体积、平均直径、根尖数、分叉数显著高于不接种处理;接种处理间苗木只有根尖数存在显著差异;接种褐环乳牛肝菌的油松根系分支成80°—90°的一级侧根数占23.81%,显著多于接种红汁乳菇和对照苗木。研究表明,接种褐环乳牛肝菌和红汁乳菇均能促进油松苗木生长,提高油松体内抗氧化酶活性,扩大苗木根系的吸收范围,其中褐环乳牛肝菌各方面的促进效果要优于红汁乳菇。     

樟树(Cinnamomum camphora)幼苗细根形态对氮磷添加和幼苗密度的响应

全球氮沉降对森林生态系统结构和功能的影响已成为现代生态学研究热点之一,我国华南地区氮沉降的增长引起了土壤酸化和磷限制加剧等一系列生态问题。密度制约着植物个体对环境资源的吸收利用,是自然界中十分重要的选择压力之一。因此研究樟树(Cinnamomum camphora)幼苗的细根形态对氮磷添加和密度的响应,有利于了解亚热带树木根系对氮沉降和磷添加与林分密度的响应过程和机制,并为全球变化背景下樟树林生态系统的管理提供依据。本研究以1年生樟树幼苗为试验材料,选择氯化铵(NH_4Cl)作为氮肥以模拟大气氮沉降,并且以二水合磷酸二氢钠(NaH_2PO_4·2H_2O)模拟磷添加,氮磷处理设置4个水平,即对照、施N、施P和施N+P;种植密度设置10、20、40和80株/m~2 4个水平。测定各处理樟树幼苗细根的根长、表面积、体积和根尖数,分析氮磷添加、密度和两者交互作用对樟树幼苗细根的影响。研究结果表明,与对照处理相比,N、P和N+P处理促进了幼苗细根长度、表面积、体积以及根尖数的增加。低密度条件下的N添加对幼苗根系形态的促进效果强于P添加。N+P处理对10、20、40株/m~2幼苗根系形态的促进效果最佳,而各处理对80株/m~2幼苗根系形态的促进效果均无显著性差异。随着种植密度的增大,幼苗细根长度、表面积、体积和根尖数均减少。樟树幼苗的细根长度、表面积、体积和根尖数在各密度间和不同氮磷添加处理间均有显著性差异,密度和氮磷处理间的交互作用对根系形态各指标均无显著影响。     

不同分类系统下油松幼苗根系特征的差异与联系

植物根序和径级不仅反映细根的形态结构, 而且能反映根系的一些生理特征, 如细根寿命和周转等。该文以二年生油松(Pinus tabulaeformis)幼苗根系为研究对象, 系统比较了根序分类方法和径级分类方法在描述根系特征上的优缺点, 探索了两者之间的内在联系。结果表明: 二年生油松幼苗最多可包括6级根序, 直径的变化范围为0.169-3.877 mm。按根序划分, I-VI级根序的总根长和总根表面积主要集中在前3级根序, 这3级根序的根占总根长的78.77%和总根表面积的62.72%。前3级根序的比根长是后3级根序比根长的1.3-3.0倍, 比根面积是后3级比根面积的1.0-1.5倍。按常用的径级(以0.5、1.0、1.5和2.0 mm为阈值)划分方法, 油松幼苗大部分根系直径≤1.5 mm, 此区间细根的根长和根表面积占总根长的93.76%和总根表面积的84.35%。直径≤1.5 mm的细根平均比根长是>1.5 mm细根比根长的3-7倍, 比根面积的1.5-3.0倍。由于油松根序和径级之间有显著的指数关系, 依据径级最大程度反映根序的原则, 提出了新的径级划分方法, 即以0.4、0.8、1.3和2.0 mm为阈值对油松幼苗根系径级重新进行划分。此时, 上述区间可分别包括I级、II级、III级、IV级、V级根序中根尖数的93.22%、86.37%、75.96%、70.47%和76.67%。同时也可分别涵盖各径级根长的89.34%-70.83%、根面积的86.01%-76.12%以及体积的87.73%-76.12%。此时, 根系不同径级与根序之间可以建立起良好的对应关系。这些结果表明, 通过合理划分径级区间可以较好地反映根序 特征。     

西南喀斯特石漠化环境适生植物细根构型及其与细根和根际土壤养分计量特征的相关性

以西南喀斯特石漠化环境适生植物构树(Broussonetia papyrifera)、花椒(Zanthoxylum bungeanum)、刺梨(Rosa roxburghii)、火棘(Pyracantha fortuneana)为研究对象,采用挖掘法采集完整的细根根系,分析细根构型特征及其与细根和根际土壤C、N、P养分元素化学计量特征之间的相关性,探讨细根构型特征对石漠化贫瘠土壤生境的响应。结果表明:构树、花椒、刺梨、火棘细根构型均趋向于鱼尾形分支模式,细根拓扑指数分别为0.93、0.95、0.95和0.94。4种适生植物的细根连接长度较长,但细根根系分支率较小。构树、刺梨细根分支前后横截面积比不存在显著差异且分别为1.04、1.03,基本符合Leonardo da Vinci法则。细根构型与细根和根际土壤养分有一定的相关性。主成分分析结果表明,细根N含量及细根、根际土壤中与P相关的计量比均是影响细根构型的主要因子。进一步分析表明,4种适生植物通过减少细根次级分支、根系间的重叠、延长细根连接长度以获得充足的养分来应对环境的变化,提高对养分的吸收效率以及对喀斯特环境的生态适应性。研究结果...     

Architectural analysis and modelling of the branching process of the young oil-palm root system

An architectural analysis of the root system of young oil-palm (Elaeis guineensis Jacq.) seedlings was made. In this analysis, root branching was modelled by a Markov chain (discrete-time, discrete-state space stochastic process). This study has been realized on radicles of young oil-palm seedlings which were considered as main axes which branch. We defined an elementary length unit as the smallest length between two successive lateral roots. The model was based on the analysis of a sequence of events, each event being indexed by the rank of the elementary length unit on the main axis. An event was defined as the state of the length unit, chosen between unbranched state and three branched-state categories. The branching process of the oil-palm radicle was modelled by a four-state first-order Markov chain. Consequently, the state of an elementary length unit depended only on the state of the previous one. The Markov chain was homogeneous, i.e. the transition probabilities did not depend on the rank of the elementary length unit.This study allowed us to identify a probabilistic model of root branching which was the first step in the elaboration of a stochastic model of the architecture of the oil-palm root system.     

辽东栎幼苗根系形态特征对环境梯度的响应

以辽东栎(Quercus liaotungensis)在陕西不同分布区:秦岭北坡(太白)、黄土高原南部(黄龙)和黄土高原中部(延安)为研究地点并设置样地,对1—5年生辽东栎幼苗的根系形态指标进行测定,分析辽东栎幼苗根系形态特征及其与环境因子的关系。结果表明:由秦岭北坡到黄土高原中部,黄龙地区辽东栎幼苗根系在发育前期(1—2年)低于太白和延安,总体上黄龙地区幼苗根系总长度、表面积、总体积、根尖数、平均直径、组织密度和单株生物量高于太白和延安地区。在太白地区,辽东栎幼苗根系表面积、总体积和平均直径较小,根系分岔数较大,幼苗根系主要通过提高分岔数来拓展自己的营养空间以适应环境;在黄龙和延安地区,幼苗根系表面积、总体积和平均直径较大,根系分岔数较小,幼苗根系主要是通过根系的伸长生长适应胁迫环境。3个地区辽东栎幼苗根系总长度、表面积、总体积、根尖数和分岔数随年龄的增长呈线性函数变化格局,均可用线性函数方程y=ax+b(a0,P0.05)进行描述。冗余分析表明幼苗根系分岔数、总长度、比根长和根尖数与土壤速效磷、硝态氮、速效钾、降雨量、石砾含量和速效氮呈正相关;与较高的土壤pH值、年均温和夏季气温呈负相关。未来辽东栎林抚育经营中,含石砾的湿润土壤生境更有利于辽东栎幼苗根系生长。