Assessing fine-root biomass and production in a Scots pine stand – comparison of soil core and root ingrowth core methods

Soil core and root ingrowth core methods for assessing fine-root (< 2 mm) biomass and production were compared in a 38-year-old Scots pine (Pinus sylvestris L) stand in eastern Finland. 140 soil cores and 114 ingrowth cores were taken from two mineral soil layers (0–10 cm and 10–30 cm) during 1985–1988. Seasonal changes in root biomass (including both Scots pine and understorey roots) and necromass were used for calculating fine-root production. The Scots pine fine-root biomass averaged annually 143 g/m² and 217 g/m² in the upper mineral soil layer, and 118 g/m² and 66 g/m² in the lower layer of soil cores and ingrowth cores, respectively. The fine-root necromass averaged annually 601 g/m² and 311 g/m² in the upper mineral soil layer, and 196 g/m² and 159 g/m² in the lower layer of soil cores and ingrowth cores, respectively. The annual fine-root production in a Scots pine stand in the 30 cm thick mineral soil layer, varied between 370–1630 g/m² in soil cores and between 210 – 490 g/m² in ingrowth cores during three years. The annual production calculated for Scots pine fine roots, varied between 330–950 g/m² in soil cores and between 110 – 610 g/m² in ingrowth cores. The horizontal and vertical variation in fine-root biomass was smaller in soil cores than in ingrowth cores. Roots in soil cores were in the natural dynamic state, while the roots in the ingrowth cores were still expanding both horizontally and vertically. The annual production of fine-root biomass in the Scots pine stand was less in root ingrowth cores than in soil cores. During the third year, the fine-root biomass production of Scots pine, when calculated by the ingrowth core method, was similar to that calculated by the soil core method. Both techniques have sources of error. In this research the sampling interval in the soil core method was 6–8 weeks, and thus root growth and death between sampling dates could not be accurately estimated. In the ingrowth core method, fine roots were still growing into the mesh bags. In Finnish conditions, after more than three growing seasons, roots in the ingrowth cores can be compared with those in the surrounding soil. The soil core method can be used for studying both the annual and seasonal biomass variations. For estimation of production, sampling should be done at short intervals. The ingrowth core method is more suitable for estimating the potential of annual fine-root production between different site types.     

Measuring Fine Root Turnover in Forest Ecosystems

Development of direct and indirect methods for measuring root turnover and the status of knowledge on fine root turnover in forest ecosystems are discussed. While soil and ingrowth cores give estimates of standing root biomass and relative growth, respectively, minirhizotrons provide estimates of median root longevity (turnover time) i.e., the time by which 50% of the roots are dead. Advanced minirhizotron and carbon tracer studies combined with demographic statistical methods and new models hold the promise of improving our fundamental understanding of the factors controlling root turnover. Using minirhizotron data, fine root turnover (y⁻¹) can be estimated in two ways: as the ratio of annual root length production to average live root length observed and as the inverse of median root longevity. Fine root production and mortality can be estimated by combining data from minirhizotrons and soil cores, provided that these data are based on roots of the same diameter class (e.g., < 1 mm in diameter) and changes in the same time steps. Fluxes of carbon and nutrients via fine root mortality can then be estimated by multiplying the amount of carbon and nutrients in fine root biomass by fine root turnover. It is suggested that the minirhizotron method is suitable for estimating median fine root longevity. In comparison to the minirhizotron method, the radio carbon technique favor larger fine roots that are less dynamics. We need to reconcile and improve both methods to develop a more complete understanding of root turnover.     

Contrasting fine-root production,survival and soil CO2 efflux in pine and poplar plantations

Tree root activity, including fine-root production, turnover and metabolic activity are significant components of forest productivity and nutrient cycling. Differences in root activity among forest types are not well known. A 3-year study was undertaken in red pine (Pinus resinosa Ait.) and hybrid poplar (Populus tristis X P. balsamifera cv `Tristis no. 1') plantations to compare belowground root dynamics. We measured fine-root production, mortality and standing crop, as well as soil CO₂ efflux. Pine fine-root production was only 2.9% of that of poplar during three years; 85 pine roots were observed in minirhizotron tubes compared with 4088 poplar roots. Live-root density oscillated seasonally for both species with late winter minimum and autumn maximum. Poplar reached constant maximum live-root length within the first growing season, but pine continued to increase observed fine-root length for three growing seasons. Within the first 100 days following initial appearance, 22% of the pine roots disappeared and 38% of the poplar roots disappeared. Median fine-root longevity of pine was 291 days compared with 149 days for poplar roots. Fine-root longevity increased with depth in the soil, and was greater for roots with initial diameter >0.5 mm. The probability of poplar root death from late February to May was more than three times that in any other season, regardless of root age. Despite the greater poplar root production and live-root length, fine-root biomass and soil CO₂ efflux was greater in pine. Greater metabolic activity in the pine stand may be due to greater fine-root biomass or greater heterotrophic respiration. This revised version was published online in June 2006 with corrections to the Cover Date.     

微根管在细根研究中的应用

细根（直径≤2 mm）的周转在植物生态系统碳分配过程中具有重要意义.已往细根周转研究主要采用根钻法、分室模型法和内生长法等.这些方法由于不能直接观测到细根生长动态,导致细根周转估计不准确.微根管法是一种非破坏性野外观察细根动态的方法.本文从微根管的发展、功能、安装步骤、图像采集、参数计算、影响观测因素和存在问题等方面逐一进行介绍,并通过水曲柳和落叶松微根管细根观测实例介绍在细根周转过程研究中的应用. 结果表明,微根管可以比较精确地估计出细根长度、单位面积上根长密度、单位体积上根长密度、细根生长量、细根死亡量和细根周转等.微根管是一个观察细根生长、衰老、死亡和分解过程的有效工具.微根管观测精度主要取决于微根管安装的质量和数量、微根管取样间隔期和取样数量、微根管图像分析技术等.此外,土壤质地、石砾多少、微根管材料选择、减少光系统对根系的干扰等也是影响微根管测定精度的因素.如何提高微根管测定精度将成为今后微根管在细根研究中的主要问题.     

基于土芯法的亚热带常绿阔叶林细根空间变异与取样数量估计

树木细根具有高度空间异质性,确定合理的细根取样策略是林木细根研究的前提。通过在福建省三明米槠天然常绿阔叶林内随机钻取96个土芯,分析细根生物量和形态特征的空间变异特征,并估计各指标所需的取样数量。结果表明:(1)随着径级增加,细根各指标变异系数增大,相应的取样数量增加;(2)随着土壤深度增加,单位面积细根生物量变异程度和相应的取样数量均增加。在置信水平为95%、精度为80%的条件下,直径为0-1 mm和1-2 mm的细根,分别采集16和42个样品可以满足测定单位面积细根生物量,采集17和31个样品可以满足测定单位面积细根长度,采集25和33个样品可以满足测定单位面积细根表面积。Shapiro-Wilk检验表明,除表层土壤0-1 mm细根单位面积生物量符合正态分布外,其余细根生物量和形态指标数据均不符合正态分布。研究结果为亚热带常绿阔叶林细根的合理取样提供了科学依据。     

帽儿山温带落叶阔叶林细根生物量、生产力和周转率

细根在森林生态系统能量流动与物质循环中占有重要地位,但其生物量、生产和周转测定尚存在很大的不确定性,而且局域尺度空间变异机制尚不清楚。本研究分析了帽儿山温带天然次生林活细根生物量和死细根生物量在0～100 cm剖面的垂直分布与0～20 cm细根的季节动态、生产力和周转率,对比了采用连续根钻法(包括决策矩阵法和极差法)和内生长袋(直径3和5 cm)估测细根生产力和细根周转率,并探讨了可能影响细根的林分因子。结果表明: 76.8%的活细根生物量和62.9%的死细根生物量均集中在0～20 cm土层,随着深度增加,二者均呈指数形式减少。活细根生物量和死细根生物量的季节变化不显著,可能与冬季几乎无降雪而夏季降雨异常多有关。2种直径内生长袋估计的细根生产力无显著差异;对数转换后决策矩阵、极差法和内生长法估计的细根生产力和细根周转率差异显著。随着土壤养分增加,活细根生物量和死细根生物量比值显著增加,死细根生物量显著减少,但活细根生物量、细根生产力和细根周转率均无显著变化;细根周转率与前一年地上木质生物量增长量呈显著正相关,但与当年地上木质生物量增长量无显著相关关系。     

应用微根管法测定细根指标方法评述

树木细根(直径<2mm)在森林生态系统能量流动和物质循环中起着重要的作用。原有的细根生产周转研究中常采用的土钻法、内生长法、挖掘法、根室法和土柱法等,均不能直接观察到细根的动态变化。微根管法是一种非破坏性、可定点直接观察和研究植物根系的方法,为研究细根的生长、衰老、死亡、分解和再生长的过程提供了有效的工具,尤其适用于细根周转、寿命和分解等方面的研究。但该技术不能直接测定单位面积的细根生物量、细根化学组成及细根周转对土壤碳和养分循环的影响,需要与土钻法结合。本文就运用微根管法对细根生物量、生产、周转和寿命等指标的研究方法进行了评述。     

Root Dynamics in Restored and Naturally Regenerated Atlantic White Cedar Wetlands

This work addressed the seasonal and successional factors of root dynamics in natural and restoration Atlantic white cedar (AWC) wetlands. Using minirhizotrons and soil root cores, fine root dynamics were measured in a chronosequence of reference and restoration AWC wetlands to compare trends in ecosystem development after canopy harvest. Seasonal fine root abundance, production, and mortality were sampled during a 439‐day period in one restoration and three reference AWC wetlands. Soil cores were collected to measure fine root biomass and to determine allometric relationships between root length and biomass. Significant seasonal variation of root dynamics was observed in the young reference and restoration sites. The mature and intermediate‐aged sites exhibited little seasonal variability in root abundance and mortality. Root production was variable but not seasonally consistent. Results suggest that root dynamics become less seasonal as AWC communities shift from herbaceous to woody vegetation dominance. No trend in fine root abundance along the chronosequence was observed, suggesting that roots rapidly reestablish following tree harvest. Measurements of annual root length production suggest increasing annual production with decreasing stand age. However, a reversal of this trend was observed when using production estimates calculated from minirhizotron measurements and root length–mass relationships. These findings underscore the importance of supplementing minirhizotron data with root allometric relationships when analyzing vegetation gradients. Overall, results indicate substantial differences in the form and quantity of root contributions to soil organic matter in the restoration site compared to that in the reference chronosequence. Higher initial planting densities of AWC are recommended to achieve similar contributions of roots to soil organic matter accumulation in the restoration site.     

森林生态系统根系生物量研究进展

在森林生态系统功能过程研究中,特别是在生产力和生物地化学循环方面,根系的作用不容忽视,但是,由于研究方法和研究者的观念等方面的限制,对于根系的研究还远不及地上部分受到重视。而关于细根生物量,周转率和生产力等方面的是很少有人问津。为推动我国根系生物学研究的发展,本一面地介绍了９种典型的测度细根生物量的方法。包括：收获法、钻土芯法、内生长土芯法、平衡法、根观测实验室法、土壤碳平衡法、挖土块法、间接法和     

Distribution,biomass, and dynamics of roots in a revegetated stand of <Emphasis Type="Italic">Caragana korshinskii</Emphasis> in the Tengger Desert,northwestern China

A field experiment was conducted to investigate root distribution, biomass, and seasonal dynamics in a revegetated stand of Caragana korshinskii Kom. in the Tengger Desert. We used soil profile trenches, soil core sampling, and minirhizotron measurements to measure root dynamics. Results showed that the roots of C. korshinskii were distributed vertically in the uppermost portion of the soil profile, especially the coarse roots, which were concentrated in the upper 0.4 m. The horizontal distribution of the root length and weight of C. korshinskii coarse roots was concentrated within 0.6 and 0.4 m of the trunk, respectively. The lateral distribution of fine roots was more uniform than coarse roots. Total-root and fine-root biomasses were 662.4 ± 45.8 and 361.1 ± 10.3 g m⁻², accounting for about two-thirds and one-third of the total plant biomass, respectively. Fine-root turnover is closely affected by soil water, and both of these parameters showed synchronously seasonal trends during the growing season in 2004 and 2005. The interaction between fine-root turnover and soil water resulted in the fine-root length densities and soil water content in the 0- to 1.0-m soil layer having similar trends, but the soil water peaks occurred before those of the fine-root length densities.     

Dynamics of heterorhizic root systems: protoxylem groups within the fine-root system of Chamaecyparis obtusa

To understand the physiology of fine-root functions in relation to soil organic sources, the heterogeneity of individual root functions within a fine-root system requires investigation. Here the heterogeneous dynamics within fine-root systems are reported. The fine roots of Chamaecyparis obtusa were sampled using a sequential ingrowth core method over 2 yr. After color categorization, roots were classified into protoxylem groups from anatomical observations. The root lengths with diarch and triarch groups fluctuated seasonally, whereas the tetrarch root length increased. The percentage of secondary root mortality to total mortality increased with increasing amounts of protoxylem. The carbon : nitrogen ratio indicated that the decomposability of primary roots might be greater than that of secondary roots. The position of diarch roots was mostly apical, whereas tetrarch roots tended to be distributed in basal positions within the root architecture. We demonstrate the heterogeneous dynamics within a fine-root system of C. obtusa. Fine-root heterogeneity should affect soil C dynamics. This heterogeneity is determined by the branching position within the root architecture.     

CO2 enrichment increases carbon and nitrogen input from fine roots in a deciduous forest

* Greater fine-root production under elevated [CO2] may increase the input of carbon (C) and nitrogen (N) to the soil profile because fine root populations turn over quickly in forested ecosystems. * Here, the effect of elevated [CO)] was assessed on root biomass and N inputs at several soil depths by combining a long-term minirhizotron dataset with continuous, root-specific measurements of root mass and [N]. The experiment was conducted in a CO(2)-enriched sweetgum (Liquidambar styraciflua) plantation. * CO2) enrichment had no effect on root tissue density or [N] within a given diameter class. Root biomass production and standing crop were doubled under elevated [CO2]. Though fine-root turnover declined under elevated [CO2], fine-root mortality was also nearly doubled under CO2 enrichment. Over 9 yr, root mortality resulted in 681 g m(-2) of extra C and 9 g m(-2) of extra N input to the soil system under elevated [CO2]. At least half of these inputs were below 30 cm soil depth. * Increased C and N input to the soil under CO2 enrichment, especially below 30 cm depth, might alter soil C storage and N mineralization. Future research should focus on quantifying root decomposition dynamics and C and N mineralization deeper in the soil.     

Fine root biomass estimates from minirhizotron imagery in a shrub ecosystem exposed to elevated CO2

Fine root biomass and C content are critical components in ecosystem C models, but they cannot be directly determined by minirhizotron techniques, and indirect methods involve estimating 3-dimensional values (biomass/ soil volume) from 2-dimensional measurements. To estimate biomass from minirhizotron data, a conversion factor for length to biomass must be developed, and assumptions regarding depth of view must be made. In a scrub-oak ecosystem in central Florida, USA, root length density (RLD) was monitored for 10 years in a CO₂ manipulation experiment using minirhizotron tubes. In the seventh year of the study, soil cores were removed from both ambient and elevated CO₂ chambers. Roots from those cores were used to determine specific root length values (m/g) that were applied to the long-term RLD data for an estimation of root biomass over 10 years of CO₂ manipulation. Root length and biomass estimated from minirhizotron data were comparable to determinations from soil cores, suggesting that the minirhizotron biomass model is valid. Biomass estimates from minirhizotrons indicate the <0.25 mm diameter roots accounted for nearly 95% of the total root length in 2002. The long-term trends for this smallest size class (<0.25 mm diameter) mirrored the RLD trends closely, particularly in relation to suspected root closure in this system. Elevated CO₂ did not significantly affect specific root length as determined by the soil cores. A significant treatment effect indicated smallest diameter fine roots (<0.25 mm) were greater under elevated CO₂ during the early years of the study and the largest (2–10 mm) had greater biomass under elevated CO₂ during the later years of the study. Overall, this method permits long-term analysis of the effects of elevated CO₂ on fine root biomass accumulation and provides essential information for carbon models.     

The effect of tree species diversity on fine-root production in a young temperate forest

The phenomenon of overyielding in species-diverse plant communities is mainly attributed to complementary resource use. Vertical niche differentiation belowground might be one potential mechanism for such complementarity. However, most studies that have analysed the diversity/productivity relationship and belowground niche differentiation have done so for fully occupied sites, not very young tree communities that are in the process of occupying belowground space. Here we used a 5–6 year old forest diversity experiment to analyse how fine-root (<2 mm) production in ingrowth cores (0–30 cm) was influenced by tree species identity, as well as the species diversity and richness of tree neighbourhoods. Fine-root production during the first growing season after the installation of ingrowth cores increased slightly with tree species diversity, and four-species combinations produced on average 94.8% more fine-root biomass than monocultures. During the second growing season, fine-root mortality increased with tree species diversity, indicating an increased fine-root turnover in species-rich communities. The initial overyielding was attributable to the response to mixing by the dominant species, Pseudotsuga menziesii and Picea abies, which produced more fine roots in mixtures than could be expected from monocultures. In species-rich neighbourhoods, P. abies allocated more fine roots to the upper soil layer (0–15 cm), whereas P. menziesii produced more fine roots in the deeper layer (15–30 cm) than in species-poor neighbourhoods. Our results indicate that, although there may be no lasting overyielding in the fine-root production of species-diverse tree communities, increasing species diversity can lead to substantial changes in the production, vertical distribution, and turnover of fine roots of individual species.     

高寒草甸植被细根生产和周转的比较研究

植物根系是陆地生态系统重要的碳汇和养分库,细根周转过程是陆地生态系统地下部分碳氮循环的核心环节,在陆地生态系统如何响应全球变化中起着关键作用。在全球变化敏感地区之一的青藏高原,对该地区的主要植被类型矮嵩草草甸同时采用根钻法、内生长袋法和微根管法3种观测方法研究细根生产和周转速率,并探讨了极差法、积分法、矩阵法和Kaplan-Meier法等数据处理方法对计算值的影响。研究结果显示:在估算细根净初级生产力时,根钻法宜采用积分法,内生长袋法宜选用矩阵法;由此进一步以最大细根生物量为基础,根钻法和内生长袋法估测的细根年周转速率分别为0.36 a-1和0.52 a-1,内生长袋法的估算结果是根钻法的1.44倍。对于微根管法,将其观测得到的细根长度转换为单位面积的生物量值后,采用积分法计算出细根周转速率为0.84 a-1,远高于传统方法的估算结果;若采用Kaplan-Meier生存分析方法,则计算出的细根周转速率更高达3.41 a-1。     

Fine-root growth,mortality and heavy metal concentrations in limed and fertilized Pinus silvestris (L.) stands in the vicinity of a Cu-Ni smelter in SW Finland

This study was conducted to assess 1) the growth of fine roots into ingrowth cores and fine root mortality, 2) the effects of liming and correction fertilization on fine-root growth and mortality, and 3) the concentrations of heavy metals in fine roots in control, limed or fertilized Scots pine stands at different distances from a copper-nickel smelter. Fine-root biomass in the ingrowth cores in the control plots varied between 1 (at 0.5 km from the smelter) and 252 and 271 g/m² (at 4 and 8 km, respectively). In the most polluted stand at 0.5 km, 98% of the fine roots that had grown into the ingrowth cores had died before sampling. Corresponding values for the other stands (4 and 8 km) were only 13-18%. At 0.5 km, liming increased the growth and survival of fine roots. The concentrations of Cu and Ni were also smaller in fine roots from the limed plot than those from the control plot. In the correction fertilization treatment at 0.5 km the total ingrowth of fine roots was at the same level as in the control, but less fine roots had died. Thus, the correction fertilizer treatment increased the survival but not the growth of fine roots. At 4 or 8 km, there were no significant differences in the fine-root biomass or necromass or element concentrations between the treatments. This revised version was published online in June 2006 with corrections to the Cover Date.     

Advancing the use of minirhizotrons in wetlands

Background

Wetlands store a substantial amount of carbon (C) in deep soil organic matter deposits, and play an important role in global fluxes of carbon dioxide and methane. Fine roots (i.e., ephemeral roots that are active in water and nutrient uptake) are recognized as important components of biogeochemical cycles in nutrient-limited wetland ecosystems. However, quantification of fine-root dynamics in wetlands has generally been limited to destructive approaches, possibly because of methodological difficulties associated with the unique environmental, soil, and plant community characteristics of these systems. Non-destructive minirhizotron technology has rarely been used in wetland ecosystems.

Scope

Our goal was to develop a consensus on, and a methodological framework for, the appropriate installation and use of minirhizotron technology in wetland ecosystems. Here, we discuss a number of potential solutions for the challenges associated with the deployment of minirhizotron technology in wetlands, including minirhizotron installation and anchorage, capture and analysis of minirhizotron images, and upscaling of minirhizotron data for analysis of biogeochemical pools and parameterization of land surface models.

Conclusions

The appropriate use of minirhizotron technology to examine relatively understudied fine-root dynamics in wetlands will advance our knowledge of ecosystem C and nutrient cycling in these globally important ecosystems.     

三工河流域两种琵琶柴群落细根生物量、分解与周转

细根对植物群落功能的发挥和土壤碳库及全球碳循环具有重要意义。利用连续土钻取样法和分解袋法,于2010年5—10月整个生长季节内,对三工河流域两处长势不同的琵琶柴群落的细根(φ2mm)生物量、分解与周转规律及其与土壤环境的关系进行研究。结果表明,群落1和群落2土壤容重、土壤含水量、pH和电导率等土壤因子差异显著。两群落的细根生物量表现出相同的季节和垂直变化趋势,即在5—8月逐渐增加,8月达到最大值,9—10月份逐渐下降。平均月细根生物量分别为51.55g/m2和133.93 g/m2。群落1的活细根和死细根分别占总细根生物量的69.68%和30.32%,群落2活细根和死细根分别占总细根生物量的72.61%和27.39%。在垂直变化上,随土壤深度增加细根生物量先增加后逐渐降低,其中10—20cm土壤层次细根生物量比例最大,群落1和群落2分别占46.48%和29.15%。群落1和群落2的细根年分解率分别为34.82%、42.91%。达到半分解和95%分解时,群落1需要630 d和2933 d,群落2需要467 d和2238 d。群落1和群落2的细根净生产力分别为50.67 g/m2和178.15 g/m2,细根年周转率分别为1.41次、1.69次。逐步回归分析结果显示细根动态受土壤水分、pH值、电导度等土壤因子的显著影响,琵琶柴细根具有相对较低的分解速率和较高的周转速率。     

Fine-root trait plasticity of beech (<Emphasis Type="Italic">Fagus sylvatica</Emphasis>) and spruce (<Emphasis Type="Italic">Picea abies</Emphasis>) forests on two contrasting soils

Aim

The fine roots of trees may show plastic responses to their resource environment. Several, contrasting hypotheses exist on this plasticity, but empirical evidence for these hypotheses is scattered. This study aims to enhance our understanding of tree root plasticity by examining intra-specific variation in fine-root mass and morphology, fine-root growth and decomposition, and associated mycorrhizal interactions in beech (Fagus sylvatica L.) and spruce (Picea abies (L.) Karst.) forests on soils that differ in resource availability.

Methods

We measured the mass and morphological traits of fine roots (i.e. ≤ 2 mm diameter) sampled to 50 cm depth. Fine-root growth was measured with ingrowth cores, and fine-root decomposition with litter bags. Mycorrhizal fungal biomass was determined using ingrowth mesh bags.

Results

Both tree species showed more than three times higher fine-root mass, and a ten-fold higher fine-root growth rate on sand than on clay, but no or marginal differences in overall fine-root morphology. Within the fine-root category however, beech stands had relatively more root length of their finest roots on clay than on sand. In the spruce stands, ectomycorrhizal mycelium biomass was larger on sand than on clay.

Conclusions

In temperate beech and spruce forests, fine-root mass and mycorrhizal fungal biomass, rather than fine-root morphology, are changed to ensure uptake under different soil resource conditions. Yet enhancing our mechanistic understanding of fine-root trait plasticity and how it affects tree growth requires more attention to fine-root dynamics, the functional diversity within the fine-roots, and mycorrhizal symbiosis as an important belowground uptake strategy.

     

水曲柳和兴安落叶松人工林细根分解研究

  细根分解是陆地生态系统C和养分循环的重要环节。以往的细根分解研究以埋袋法的应用为主。然而, 由于埋袋法对分解材料的干扰以及对分解环境的改变使其很难揭示原位环境下根系的自然分解过程。该研究应用微根管(Minirhizotron)技术连续3年对水曲柳(Fraxinus mandshurica)和兴安落叶松(Larix gmelinii)细根的分解过程进行原位监测, 运用Kaplan–Meier方法估算细根分解的保存率及分解期中位值(即50%细根完全分解的时间, Median root decomposition time), 做分解曲线, 用对数秩检验(Log-rank test)方法分析不同树种、直径、根序及土层对细根保存率的影响。结果表明, 伴随时间延长, 细根的保存率逐渐下降, 兴安落叶松细根保存率的下降显著快于水曲柳(p<0.001), 两树种分解期中位值分别为(82±7) d 和(317±28) d; 不同直径等级(≤0.3、0.3～0.6、＞0.6 mm)细根的分解速率不同, 两树种最长分解期中位值均出现在最细直径(≤0.3 mm)根中; 高级根分解速率显著低于一级根(p<0.05); 土壤上层分解速度快, 随着土壤深度增加细根分解速率减小。微根管技术为了解细根自然分解过程提供了有效途径。