Fine root biomass and production in Scots pine stands in relation to stand age

We determined fine root biomass and production of 15-, 35- and 100-year-old Scots pine (Pinus sylvestris L.) stands during three growing seasons. Fine roots were sampled by the soil core method. Mean (+/- SE) annual fine root biomass of Scots pine in the 15-, 35- and 100-year-old stands was 220 +/- 25, 357 +/- 21 and 259 +/- 26 g m(-2), respectively. Fine root biomass of the understory vegetation was 159 +/- 54 g m(-2), 244 +/- 30 and 408 +/- 81 g m(-2), and fine root necromass was 500 +/- 112, 1,047 +/- 452 and 1,895 +/- 607 g m(-2) in the sapling, pole stage and mature stands, respectively. Both understory and Scots pine fine root production increased with stand age. Mean annual Scots pine fine root production was 165 +/- 131, 775 +/- 339 and 860 +/- 348 g m(-2) year(-1) in the sapling, pole stage and mature stand, respectively. The respective mean annual production of all fine roots (Scots pine and understory) was 181 +/- 129, 1,039 +/- 497 and 1,360 +/- 869 g m(-2) year(-1). The Scots pine and understory fine root biomass, necromass and production varied in relation to stand age, although the variation was not statistically significant.     

Fine root biomass in relation to site and stand characteristics in Norway spruce and Scots pine stands

Variations in fine root biomass of trees and understory in 16 stands throughout Finland were examined and relationships to site and stand characteristics determined. Norway spruce fine root biomass varied between 184 and 370 g m(-2), and that of Scots pine ranged between 149 and 386 g m(-2). In northern Finland, understory roots and rhizomes (< 2 mm diameter) accounted for up to 50% of the stand total fine root biomass. Therefore, the fine root biomass of trees plus understory was larger in northern Finland in stands of both tree species, resulting in a negative relationship between fine root biomass and the temperature sum and a positive relationship between fine root biomass and the carbon:nitrogen ratio of the soil organic layer. The foliage:fine root ratio varied between 2.1 and 6.4 for Norway spruce and between 0.8 and 2.2 for Scots pine. The ratio decreased for both Norway spruce and Scots pine from south to north, as well as from fertile to more infertile site types. The foliage:fine root ratio of Norway spruce was related to basal area and stem surface area. The strong positive correlations of these three parameters with fine root nitrogen concentration implies that more fine roots are needed to maintain a certain amount of foliage when nutrient availability is low. No significant relationships were found between stand parameters and fine root biomass at the stand level, but the relationships considerably improved when both fine root biomass and stand parameters were calculated for the mean tree in the stand. When the northern and southern sites were analyzed separately, fine root biomass per tree of both species was significantly correlated with basal area and stem surface area per tree. Basal area, stem surface area and stand density can be estimated accurately and easily. Thus, our results may have value in predicting fine root biomass at the tree and stand level in boreal Norway spruce and Scots pine forests.     

Changes in fine root production and longevity in relation to water and nutrient availability in a Norway spruce stand in northern Sweden

Effects of irrigation and liquid fertilization on fine root (< 1 mm) production and longevity, and fine root (< 0.5-2 mm) biomass were studied in a Norway spruce (Picea abies (L.) Karst.) stand in northern Sweden. Fine root length production and longevity were measured by the minirhizotron technique at 0-10 cm depth in the following treatments: irrigation (I), liquid fertilization (IL) and control (C). Standing root biomass and root length density (RLD) were studied in the litter-fermented humus (LFH) layer and at depths of 0-10, 10-20 and 20-30 cm using soil cores in solid fertilized (F) and C plots. Minirhizotrons were installed in October 1994 and measurements recorded monthly from July to September 1995 and during the growing season in 1996. Soil cores were sampled in 1996. Fine root production increased significantly in IL plots compared with C plots, but the I treatment did not increase root production. Root mortality increased significantly in IL plots compared with C plots. Fine root longevity in IL plots was significantly lower compared with C and I plots. No significant difference was found between longevity of fine roots in I and C plots. Compared with C, F treatment increased fine root biomass in the LFH and mineral soil layers, and increased the amount of fine roots in mineral soil layers relative to the LFH layer. Furthermore, F increased RLD and the number of mycorrhizal root tips significantly.     

水曲柳人工林细根季节动态及其影响因素

2002年5-10月,采用连续钻取土芯法对帽儿山实验林场的水曲柳人工林细根(直径＜1 mm)生物量、比根长(SRL)和根长密度(RLD)的季节动态,以及它们与土壤N的有效性、土壤10 cm深处月均温度和含水量的关系进行研究.结果表明:水曲柳细根生物量在春季和秋季分别具有1个明显的高峰,但比根长和根长密度只有1个高峰.在春季和夏季,比根长和根长密度较高,显示细根直径较小,而秋季,这2个参数显著下降,表明细根直径次生增厚或组织密度增加.细根的季节变化与土壤N的有效性、土壤温度和土壤含水量有重要关系.其中细根生物量与土壤铵态氮含量显著相关;硝态氮含量、10 cm深处土壤的温度和土壤含水量与细根的生物量、比根长和根长密度的季节变化正相关,但均不显著(P＞0.05).4种因子的综合作用对水曲柳细根各参数的影响均达到了显著水平.不同季节细根生物量、比根长和根长密度的变化,显示出细根在生长季不同时期具有不同的生理生态功能.     

Root turnover and root necromass accumulation of Norway spruce (Picea abies) are affected by soil acidity

Fine root distribution and turnover were investigated in ca. 40-year-old pure Norway spruce (Picea abies Karst.) stands in Germany, growing on four sites that differed in soil acidity (Eberg?tzen < Barbis < Fichtelgebirge = Harz). The density of fine root biomass and necromass in different soil horizons differed among the sites. At one of the most acidic sites (Harz), fine root density in the humus layer was more than twice that at the least acidic site (Eberg?tzen). At the two most acidic sites, Fichtelgebirge and Harz, the ratio of biomass to necromass was significantly lower than at Eberg?tzen and Barbis, particularly in the subsoil layer. In each stand, clear vertical gradients in fine root length density and root tip density were observed. Most of the roots and the root tips were in the humus layer and in the first mineral soil horizon (0-10 cm). There was a significantly different decrease in specific root length (cm gDM (-1)) and specific root tip density (root tips gDM (-1)) in the more acidified stands Fichtelgebirge and Harz compared with Eberg?tzen and Barbis. Fine root production estimated by ingrowth cores and a net method was approximately twice as high in the more acidic stands Fichtelgebirge and Harz compared with Eberg?tzen and Barbis. Rates of living fine root biomass turnover were higher at the Fichtelgebirge and Harz sites than at the Eberg?tzen site. Rates of necromass turnover were similar at all sites. The results suggest that the accumulation of necromass was not due to a slower disappearance at the more acid sites, but to earlier root death. Roots contributed 46% to root + needle litter and 32% to root + total aboveground litter at the Harz site in 1997.     

Fine root biomass of Scots pine stands differing in age and soil fertility in southern Finland

The biomass of small and large fine roots (相似文献   

Effects of slash retention and wood ash addition on fine root biomass and production and fungal mycelium in a Norway spruce stand in SW Sweden

In the study reported here we examined the short-term effects (1–3 years) of slash retention (SR) and the long-term effects (13–15 years) of wood-ash application (A) on fine roots and mycorrhizae in a 40-year-old Norway spruce forest in southwest Sweden. Soil cores were used to obtain estimates of the biomass (g m⁻²) of roots in three diameter classes (<0.5, 0.5–1 and 1–2 mm), root length density (RLD), specific root length (SRL) and mycorrhizal root tip density (RTD). Fine root (<1 mm) length production and mortality, and mycelium production, were estimated using minirhizotron and mesh bag techniques, respectively. Compared with the control plots (C), the biomass of fine roots in diameter classes <0.5 mm and 0.5–1 mm was significantly higher in A plots, but lower in SR plots. In addition, RLD was significantly lower in the humus layer of SR plots than in the humus layers of C and A plots, but not in the other layers. None of the treatments affected the SRL. In all soil layers, the SR treatment resulted in significant reductions in the number of ectomycorrhizal root tips, and the mycelia production of fungi in mesh bags, relative to the C treatment, but the C and A treatments induced no significant changes in these variables. Fine root length production in the C, A and SR plots amounted to 94, 87 and 70 mm tube⁻¹ during the 2003 growing season, respectively. Fine root mortality in treated plots did not change over the course of the study. We suggest that leaving logging residues on fertile sites may result in nitrogen mineralisation, which may in turn induce reductions in root biomass, and both root and mycelium production, and consequently affect nutrient uptake and the accumulation of organic carbon in soil derived from roots and mycorrhizae.     

Biomass of fine and small roots in two Japanese black pine stands of different ages

The biomass and the spatial distribution of fine and small roots were studied in two Japanese black pine (Pinus thunbergii Parl.) stands growing on a sandy soil. More biomass of fine and small roots was found in the 17-year-old than in the 40-year-old stand. There were 62 g m⁻² of fine roots and 56 g m⁻² of small roots in the older stand, which represented mean values of 608 g for fine and 552 g for small roots per tree, respectively. In the younger stand, a total of 85 g m⁻² of fine roots and 66 g m⁻² of small roots were determined, representing a mean of 238 g for fine and 186 g for small roots per tree, respectively. Fine and small root biomasses decreased linearly with a soil depth of 0–50 cm in the older stand. In the younger stand, the fine and small roots developed only up to a depth of 30 cm. Horizontal distributions (with regard to distance from a tree) of both root groups were homogeneous. A positive correlation in the amount of biomass of fine and small roots per m² relative to tree size was found. Fine and small root biomasses increased consistently from April to July in both stands. The results also indicated earlier growth activity of the fine roots than small roots at the beginning of the growing season. The seasonal increases in fine and small root biomasses were slightly higher in the younger stand than the older stand.     

Root distribution of Fagus sylvatica in a chronosequence in western France

The distribution of fine (<2 mm diameter) and small roots (2–20 mm diameter) was investigated in a chronosequence consisting of 9-year-old, 26-year-old, 82-year-old and 146-year-old European beech (Fagus sylvatica) stands. A combination of trench wall observations and destructive root sampling was used to establish whether root distribution and total biomass of fine and small roots varied with stand age. Root density decreased with soil depth in all stands, and variability appeared to be highest in subsoil horizons, especially where compacted soil layers occurred. Roots clustered in patches in the top 0–50 cm of the soil or were present as root channels at greater depths. Cluster number, cluster size and number of root channels were comparable in all stands, and high values of soil exploitation occurred throughout the entire chronosequence. Overall fine root biomass at depths of 0–120 cm ranged from 7.4 Mg ha⁻¹ to 9.8 Mg ha⁻¹, being highest in the two youngest stands. Small root biomass ranged from 3.6 Mg ha⁻¹ to 13.3 Mg ha⁻¹. Use of trench wall observations combined with destructive root samples reduced the variability of these estimates. These records showed that variability in fine root distribution depended more on soil depth and edaphic conditions than on stand age, and suggest that trench wall studies provide a useful tool to improve estimates of fine root biomass.     

Fine root morphological adaptations in Scots pine, Norway spruce and silver birch along a latitudinal gradient in boreal forests

Variability in short root morphology of the three main tree species of Europe's boreal forest (Norway spruce (Picea abies L. Karst.), Scots pine (Pinus sylvestris L.) and silver birch (Betula pendula Roth)) was investigated in four stands along a latitudinal gradient from northern Finland to southern Estonia. Silver birch and Scots pine were present in three stands and Norway spruce was present in all stands. For three fertile Norway spruce stands, fine root biomass and number of root tips per stand area or unit basal area were assessed from north to south. Principal component analysis indicated that short root morphology was significantly affected by tree species and site, which together explained 34.7% of the total variability. The range of variation in mean specific root area (SRA) was 51-74, 60-70 and 84-124 m(2) kg(-1) for Norway spruce, Scots pine and silver birch, respectively, and the corresponding ranges for specific root length were 37-47, 40-48 and 87-97 m g(-1). The range of variation in root tissue density of Norway spruce, Scots pine and silver birch was 113-182, 127-158 and 81-156 kg m(-3), respectively. Sensitivity of short root morphology to site conditions decreased in the order: Norway spruce > silver birch > Scots pine. Short root SRA increased with site fertility in all species. In Norway spruce, fine root biomass and number of root tips per m(2) decreased from north to south. The differences in morphological parameters among sites were significant but smaller than the site differences in fine root biomass and number of root tips.     

Above- and belowground biomass and net primary production in a 73-year-old Scots pine forest

We estimated above- and belowground biomass and net primary production (NPP) of a 73-year-old Scots pine (Pinus sylvestris L.) forest stand in the Belgian Campine region. Total biomass for the stand was 176 Mg ha(-1), of which 74.4% was found in stems. The root system contained 12.6% of total biomass, most of it in coarse roots (> 5 mm). Fine roots (< 5 mm) comprised only about 1.7% of total biomass, and more than 50% of fine root biomass was retrieved in the litter layer and the upper 15 cm of the mineral soil. The ratio of belowground biomass to aboveground biomass was 0.14, which is lower than that of other Scots pine forests and other coniferous forests. Between 1995 and 2001, mean annual NPP was 11.2 Mg ha(-1) year(-1), of which 68.7% was allocated to aboveground compartments. Stems, needles and cones made relatively high contributions to total NPP compared with branches. However, branch NPP was possibly underestimated because litterfall of big branches was neglected. The proportion of total NPP in belowground components was 31.3%. Coarse root NPP (2% of total) was low compared with its biomass. Fine root NPP was 3.3 Mg ha(-1) year(-1), representing about 29.5% of total NPP; however, the estimate of fine root NPP is much more uncertain than NPP of aboveground compartments. The ratio NPP/GPP (gross primary production) was 0.32, which was low compared with other coniferous forests.     

林分年龄对落叶松人工林细根生物量的影响

【目的】随着森林的发育过程,林木个体的生长和生物量分配,以及林分水平的结构和功能均发生了明显的变化。然而,细根生物量与林分年龄的联系,目前仍然了解有限。本研究以黑龙江省帽儿山地区兴安落叶松人工林为研究对象,比较了同一林分在19年和32年生时林分水平(单位面积)和单株水平细根生物量的垂直分布和季节动态,分析了影响细根生物量变化的林分与土壤因子,旨在明确林分年龄对细根生物量的影响和潜在的机制。【方法】在生长季内的5月、7月和9月,采用土钻法获取土壤0~30 cm深度细根并测定生物量,同时测定林分特征和土壤养分和水分含量。【结果】随林龄增加,落叶松人工林单位面积细根生物量显著下降,而单株细根生物量变化不显著;与19年生林分相比,32年生林分土壤表层(0~10 cm)细根生物量占总细根生物量的比例明显下降,土壤亚表层(10~20 cm)和底层(20~30 cm)细根生物量所占比例增加,呈现出细根向深层土壤增生的趋势。土壤表层(0~10cm)单位面积细根生物量随林分年龄的变化趋势与林分密度和胸高断面积、土壤铵态氮浓度变化有关,但是单株细根生物量受林分和土壤因子的影响均不显著。【结论】林分发育过程中,落叶松细根生物量降低,细根的资源吸收策略发生了明显的改变。     

Impact factors on fine root seasonal dynamics in Fraxinus mandshurica plantations

Fine root turnover plays important roles in carbon allocation and nutrient cycling in forest ecosystems. Seasonal dynamics of fine roots is critical for understanding the processes of fine root turnover. From May to October 2002, soil core method was used for estimating the seasonal pattern of fine root (diameter < 1 mm) parameters (biomass, specific root length (SRL) and root length density (RLD)) in a Manchurian ash (Fraxinus mandshurica) plantation located at the Maoershan Experiment Station, Heilongjiang Province, northeast of China. The relationships of fine root biomass, SRL and RLD with available nitrogen in soil, average soil temperature per month in 10 cm depth and soil moisture content were analyzed. Seasonal variation of fine root biomass was significant (P < 0.05). The peak values of fine root biomass were observed both in spring and in autumn, but SRL and RLD were the highest in spring and lowest in autumn. Specific root length and root length density were higher in spring and summer, which means that fine root diameter was thinner. In autumn, both parameters decreased significantly due to secondary incrassation of fine root diameter or the increase of tissue density. Seasonal dynamics of fine roots was associated with available nitrogen in soil, soil temperature in 10 cm depth and moisture content. Fine root biomass has a significant relationship with available NH₄ ⁺-N in soil. Available NO₃ ⁻-N in soil, soil temperature in 10-cm depth and moisture content have a positive correlation with fine root biomass, SRL and RLD, although these correlations are not significant (P > 0.05). But the compound effects of soil available N, soil temperature and soil moisture content are significant to every root parameter. The variations of these three root parameters in different seasons show different physiological and ecological functions in different growing periods. Translated from Scientia Silvae Sinicae, 2006, 42(9): 7–12 [译自: 林业科学]     

Moderate drought alters biomass and depth distribution of fine roots in Norway spruce

A rain shelter experiment was conducted in a 90‐year‐old Norway spruce stand, in the Kysucké Beskydy Mts (Slovakia). Three rain shelters were constructed in the stand to prevent the rainfall from reaching the soil and to reduce water availability in the rhizosphere. Fine root biomass and necromass were repeatedly measured throughout a growing season by soil coring. We established the quantities of fine root biomass (live) and necromass (dead) at soil depths of 0–5, 5–15, 15–25 and 25–35 cm. Significant differences in soil moisture contents between control and drought plots were found in the top 15 cm of soil after 20 weeks of rainfall manipulation (lasting from early June to late October). Our observations show that even relatively light drought decreased total fine root biomass from 272.0 to 242.8 g m^?2 and increased the amount of necromass from 79.2 to 101.2 g m^?2 in the top 35 cm of soil. Very fine roots (VFR), that is, those with diameter up to 1 mm, were more affected than total fine roots defined as 0–2 mm. The effect of reduced water availability was depth‐specific; as a result, we observed a modification of vertical distribution of fine roots. More roots in drought treatment were produced in the wetter soil horizons at 25–35 cm depth than at the surface. We conclude that fine and VFR systems of Norway spruce have the capacity to re‐allocate resources to roots at different depths in response to environmental signals, resulting in changes in necromass to biomass ratio.     

Root development across a chronosequence in a Japanese cedar (<Emphasis Type="Italic">Cryptomeria japonica</Emphasis> D. Don) plantation

We investigated the biomass, vertical distribution, and specific root length (SRL) of fine and small roots in a chronosequence of Japanese cedar (Cryptomeria japonica D. Don) plantations in Nara Prefecture, central Japan. Roots were collected from soil blocks up to 50 cm in depth in five plantations of differing age: 4, 15, 30, 41, and 88 years old. Fine-root biomass reached a maximum (639 g m₋₂) in the 15-year-old stand before canopy closure, decreased in the 30-year-old stand (422 g m₋₂), and thereafter was stable. Except in the 30-year-old stand, fine-root biomass increased in deeper soil layers as stand age increased, and the depth at which the cumulative biomass of fine roots reached 90% exhibited a good allometric relationship with mean stem diameter. Both root-length density (root length per unit soil volume) and SRL decreased with soil depth in all stands, indicating that plants mainly acquire water and nutrients from shallow soils. The highest SRL was observed in the 4-year-old stand, but the relationship between SRL and stand age was unclear in older stands. The SRL in surface soils seemed to decrease with increases in root-length density, suggesting that branching of the fine-root system during development is related to density-dependent processes rather than age.     

Fine root dynamics in organic and mineral soil layers of <Emphasis Type="Italic">Cryptomeria japonica</Emphasis> D. Don plantation

Fine root dynamics and root architecture were studied in the organic and mineral soil layers of a Cryptomeria japonica plantation. Fine root biomass (<1 mm) showed seasonal changes whereas fine root biomass (1–2 mm) was unchanged over the study period. Root tips were grouped into size classes based on root tip diameter, including <0.5, 0.5–1, and 1–2 mm. Root tip density (<1 mm) was significantly correlated with fine root biomass (<1 mm). Root tip density and fine root biomass (<1 mm) increased in summer and decreased in winter, and both showed a similar seasonal pattern. Root tip dynamics influenced fine root dynamics. Root architecture as expressed by branching intensity changed with root tip production and mortality. Branching intensity also showed a similar seasonal pattern of root tip density dynamics. Root tips of both <0.5 and 0.5–1 mm were mainly produced in the organic soil layer, while root tips of 0.5–1 mm were mainly produced in the mineral soil layer. Because of the high RT1 root tip production in the organic soil layer, branching intensity was higher in the organic soil than in the mineral soil layer during summer. Root tip dynamics influenced fine root dynamics and the architecture of root systems in both organic and mineral soil layers.     

马尾松细根与土壤养分含量研究

应用根钻法研究黔中12年生马尾松(Pinus massoniana)林下不同层次土壤(0～20 cm和20～40 cm)细根的分布情况及土壤养分含量的分布,并做了相关性分析.结果表明,马尾松细根单位面积生物量、根长密度及比根长在0～20 cm土层明显高于20～40 cm土层,在0～20 cm土层中单位面积根量是20～40 cm土层的3～6倍;土壤中养分含量也随着土壤深度的增加逐渐减少;马尾松根系生物量、根长密度及比根长与土壤中有效性养分存在显著正相关关系;细根生物量、根长密度与马尾松胸径呈显著正相关关系;养分含量对生物量、根长密度的综合影响存在显著线性相关性(R~2=0.903、0.917),土壤养分(0～20 cm、20～40 cm)对马尾松胸径存在显著或极显著线性相关关系(R~2=0.878、0.934),与树高线形相关性不明显.     

Spatial heterogeneity of fine root biomass of Pinus massoniana forests in the Three Gorges Reservoir Area, China

Environmental heterogeneity is a constant presence in the natural world that significantly affects plant behavior at a variety of levels of complexity. In order to estimate the spatial pattern of fine root biomass in the Three Gorges Reservoir Area, the spatial heterogeneity of fine root biomass in the upper layer of soils (0-10 cm) in three Masson pine (Pinus massoniana) stands in the Three Gorges Reservoir Area, China, was studied in 30 m × 30 m plots with geostatistical analysis. The results indicate that 1) both the live and dead fine root biomass of stand 2 were less than those of other stands, 2) the spatial variation of fine roots in the three stands was caused together by structural and random factors with moderate spatial dependence and 3) the magnitude of spatial heterogeneity of live fine roots ranked as: stand 3 > stand 1 > stand 2, while that of dead fine roots was similar in the three stands. These findings suggested that the range of spatial autocorrelation for fine root biomass varied considerably in the Three Gorges Reservoir Area, while soil properties, such as soil bulk density, organic matter and total nitrogen, may exhibit great effect on the spatial distribution of fine roots. Finally, we express our hope to be able to carry out further research on the quantitative relationship between the spatial heterogeneous patterns of plant and soil properties.     

窄冠刺槐根系的研究

2006年10月用全挖法和分层分段挖掘法,研究了窄冠刺槐根系的分布特征、根系生物量以及不同密度林分根系空间分布特征.结果表明:窄冠刺槐个体根系水平分布在株间可达到6.6 m,在行间可达到5.0 m;主根可深达2 m以上,侧根垂直分布集中在10～40 cm土层内.窄冠刺槐根系生物量占全株生物量的16.82％,主根、侧根的生物量在根系生物量中分别占87.13％、12.87％.窄冠刺槐林分根系生物总量和根总长分别为6 160.2～10 940.55kg·hm-2和970.35～1 607.4 km·hm-2,并呈现出根系生物总量和根总长与林分密度成正相关的规律.在垂直方向上,林分根系中直径D<15 mm的根主要分布在地下0～20 cm土层内,而直径D≥15 mm的根主要分布在地下20～40 cm土层内;在水平方向上,直径D≥5 mm的根数量随距树干距离增加而减少,而直径D<1 mm的根数量则随距树干距离增大而增大,主要集中分布在距树干0.5～1.5 m范围内.     

江南油杉细根生物量空间分布及其对土壤水分的响应

【目的】探明广西不同栽培区江南油杉细根生物量的空间分布共性及其对土壤水分的响应机制。【方法】以广西3个栽培区江南油杉人工幼林为研究对象,采用根系全株分层挖掘和根系形态结构分析法,定量分析江南油杉幼树不同径级细根生物量密度、根长密度和表面积密度的空间分布特征。【结果】1)江南油杉幼林期细根生物量在垂直方向上主要分布在0~90 cm土层中,且0~60 cm范围内的细根生物量占总量的81.83%,细根生物量随土层深度的增加呈升高—降低—再升高的趋势。细根生物量在水平方向上主要分布在距树干0~100 cm范围内,其中0~50 cm细根生物量占总量的87.40%。综合不同径级根长密度和根表面积密度分析结果表明,d <5 mm径级细根是江南油杉幼树占主导地位的吸收根系,其中0.5 mm≤d <2 mm径级细根在不同样地以及不同土层中的根长密度值最大,是决定江南油杉幼树根长密度分布特征的主要根系。2)江南油杉细根总生物量、根系长度、根表面积与土壤水分含量呈显著的相关性,表明江南油杉细根分布对土壤水分含量的响应敏感。【结论】江南油杉细根生物量垂直分布的"双峰"特征有利于根系对表层土壤水分在下渗过程中的二次吸收利用。0~60 cm土层是江南油杉幼树根系发挥生理功能的主要土层,可作为该树种水肥管理的重要区域。