树木位置和胸径对人工林细根水平分布的影响

通过研究福建三明莘口林场33年生格氏栲和杉木人工林细根生物量与树木位置和胸径大小的关系,探讨人工林细根水平分布特点。用土芯法(土钻内径6 .8cm,深10 0 cm)测定细根生物量,格氏栲和杉木人工林分别随机取土芯4 1个和4 0个,同时记录离取样点最近的第1棵、第2棵和第3棵树的距离和胸径。格氏栲和杉木人工林细根生物量平均值分别为3.2 6 6 t/ hm2和2 .0 4 8t/ hm2 ,变异系数分别达37.3%和4 2 .8% ,细根生物量均遵从正态分布(p<0 .0 5 )。格氏栲和杉木人工林细根生物量均与离取样点最近第1棵、第2棵树的距离有显著的负相关,且以与最近第1棵树距离的相关系数最大。格氏栲人工林细根生物量与最近第1棵树的胸径呈显著的正相关(p<0 .0 1) ,而与最近第2、第3棵树的胸径无关(p>0 .0 5 ) ;而杉木人工林细根生物量则与最近第1、第2和第3棵树的胸径均无显著相关(p>0 .0 5 )。逐步多元线性回归分析表明,离取样点最近第1棵树距离和胸径可解释格氏栲人工林细根生物量水平变异的4 1.0 % ,而离取样点最近第1、2棵树距离则可解释杉木人工林细根生物量水平变异的4 0 .6 %。由于人工林细根水平分布呈现特定模式,规则取样估计细根生物量将产生系统误差。     

植物空间分布格局中邻体距离的概率分布模型及参数估计

最近邻体法是一类有效的植物空间分布格局分析方法,邻体距离的概率分布模型用于描述邻体距离的统计特征,属于常用的最近邻体法之一。然而,聚集分布格局中邻体距离(个体到个体)的概率分布模型表达式复杂,参数估计的计算量大。根据该模型期望和方差的特性,提出了一种简化的参数估计方法,并利用遗传算法来实现参数优化,结果表明遗传算法可以有效地估计的该模型的两个参数。同时,利用该模型拟合了加拿大南温哥华岛3个寒温带树种的空间分布数据,结果显示:该概率分布模型可以很好地拟合美国花旗松(P.menziesii)和西部铁杉(T.heterophylla)的邻体距离分布,但由于西北红柏(T.plicata)存在高度聚集的团簇分布,拟合结果不理想;美国花旗松在样地中近似随机分布,空间聚集参数对空间尺度的依赖性不强,但西北红柏和西部铁杉空间聚集参数具有尺度依赖性,随邻体距离阶数增加而变大。最后,讨论了该模型以及参数估计方法的优势和限制。     

Comparison of distance based density estimates for some arid rangeland vegetation

A method was required for determining the effect of management on extensive populations of trees and shrubs in central Australian rangelands. One useful indicator of change in these populations is the density of individuals, and there are several methods available based on distance measurement for density estimation. This study compared those procedures. Samples were drawn by computer from ground maps of actual plant distributions for Acacia aneura, Cassia nemophila and Atalaya hemiglauca and from a map generated at random. These samples were drawn to examine the properties of the nearest neighbour, point centred quarter, conditioned distance and compound T-square estimates of density. Samples were drawn by two methods: simple random sampling and semisystematic sampling. In general, there was a tendency for all estimators of density to underestimate the true density of naturally occurring populations with the compound T-square method (Byth 1982) being most robust. The compound T-square method was least biased but its variance increased for more aggregated spatial distributions. Estimates of density were not altered by the use of semisystematic sampling, when compared to simple random sampling. The spatial distributions examined in this study have not previously been studied as theoretical models. Acacia aneura and Cassia nemophila showed some aggregation of clusters, while the Atalaya hemiglauca showed a more extreme form of clustering due to its root suckering propagation.     

Unusual Fine Root Distributions of Two Deciduous Tree Species in Southern France: What Consequences for Modelling of Tree Root Dynamics?

The spatial distribution of fine roots of two deciduous tree species was investigated in contrasting growing conditions in southern France. Hybrid walnut trees (Juglans regia×nigra cv. NG23) and hybrid poplars (Populus euramericana cv. I214) were both cultivated with or without annual winter intercrops for 10 years on deep alluvial soils. Soil samples for measuring the fine root distribution of both trees and crops were obtained by soil coring down to 3-m depth at several distances and orientations from the tree trunk. The distribution of live fine roots from walnut and poplar trees was patchy and sometimes unexpected. In the tree-only stands, fine root profiles followed the expected pattern, as fine root density decreased with increasing depth and distance from the tree trunk. However, many fine root profiles under intercropped trees were uniform with depth, and some inverse profiles were observed. These distributions may result from a high degree of plasticity of tree root systems to sense and adapt to fluctuating and heterogeneous soil conditions. The distortion of the tree root system was more pronounced for the walnut trees that only partially explored the soil volume: in the tree-only stand, the walnut rooting pattern was very superficial, but in the intercropped stand walnut trees developed a deep and dense fine root network below the crop rooting zone. The larger poplars explored the whole available soil volume, but the intercrop significantly displaced the root density from the topsoil to layers below 1 m depth. Most tree root growth models assume a decreasing fine root density with depth and distance from the tree stem. These models would not predict correctly tree–tree and tree–understorey competition for water and nutrients in 3D heterogeneous soil conditions that prevail under low-density tree stands. To account for the integrated response of tree root systems to such transient gradients in soils, we need a dynamic model that would allow for both genotypic plasticity and transient environmental local soil conditions.     

基于空间结构调查的林分密度估计

利用林分空间结构抽样调查技术,采用测量抽样点到其第k株最近相邻木的距离(距离法)进行密度估计,分别选取k=4和k=6两种距离调查方法进行分析,并对Prodan、Persson、Thompson 3种不同密度估计方法的预估能力进行检验.结果表明：不同预估方法的预估能力受林木水平分布格局影响.Prodan法在均匀分布的林分中有较强的预估能力,随着分布格局聚集性增加会产生越来越大的偏差;Persson计算法在均匀及随机分布的林分中产生正偏差,但随着分布格局聚集性增加产生的相对误差接近0,预估能力增强;Thompson计算法对随机或接近随机分布的林分有较强的预估能力,而在均匀分布和聚集分布的格局中分别产生正偏差和负偏差.抽样点为49个时,选择6株木与4株木预估能力无显著差异,因此,密度估计可与选取4株相邻木的空间结构参数调查整合在一起.     

Optimization of sampling methods for within-tree populations of red oak borer, Enaphalodes rufulus (Haldeman) (Coleoptera: Cerambycidae)

In the Ozark Mountains of northern Arkansas and southern Missouri, an oak decline event, coupled with epidemic populations of red oak borer (Enaphalodes rufulus Haldeman), has resulted in extensive red oak (Quercus spp., section Lobatae) mortality. Twenty-four northern red oak trees, Quercus rubra L., infested with red oak borer, were felled in the Ozark National Forest between March 2002 and June 2003. Infested tree boles were cut into 0.5-m sample bolts, and the following red oak borer population variables were measured: current generation galleries, live red oak borer, emergence holes, and previous generation galleries. Population density estimates from sampling plans using varying numbers of samples taken randomly and systematically were compared with total census measurements for the entire infested tree bole. Systematic sampling consistently yielded lower percent root mean square error (%RMSE) than random sampling. Systematic sampling of one half of the tree (every other 0.5-m sample along the tree bole) yielded the lowest values. Estimates from plans systematically sampling one half the tree and systematic proportional sampling using seven or nine samples did not differ significantly from each other and were within 25% RMSE of the "true" mean. Thus, we recommend systematically removing and dissecting seven 0.5-m samples from infested trees as an optimal sampling plan for monitoring red oak borer within-tree population densities. This optimal sampling plan should allow for collection of acceptably accurate within-tree population density data for this native wood-boring insect and reducing labor and costs of dissecting whole trees.     

Spatial explicit distribution of individual fine root biomass of <Emphasis Type="Italic">Rhizophora mangle</Emphasis> L. (Red Mangrove) in South Florida

Fine roots are of major importance for belowground processes in mangrove ecosystems. Little is known about individual mangrove root systems, particularly the fine root component. We measured fine root biomass distribution of solitary standing Rhizophora mangle L. individuals with the dual aim of (a) deepening our understanding of the belowground ecology and allometric relations of this species; and (b) gaining further information about its climatic relevance. Twelve trees of variable height (45–240 cm) were measured on three reforested sites in south-east Florida, USA. Soil cores were collected from individual trees at transects by means of auger sampling. Fine roots were extracted, sorted, dried and weighed. Mean fine root biomass varied between 20.56–253.12 g/m². Two separate mixed-effects models led to statistically sound predictions of spatial fine root biomass distribution. The first model was based on distance function and tree height (Model 1, \(R^2 = 0.77\), p value ≤ 0.001), and the second on prop root density (Model 2, \(R^2 = 0.56\), p value ≤ 0.001). Besides the aforementioned fixed effects, the results of both models indicated random, site-specific variation with regards to fine root biomass distribution. Nevertheless, we were able to explain individual fine root biomass distribution with reference to aboveground characteristics alone. These findings may help to improve the modelling of belowground plant interaction and carbon storage in mangroves, both of which are intrinsically linked to fine roots.     

Response of fine roots to an experimental gap in a boreal Picea abies forest

We examined the initial response of the quantity and distribution of fine roots to the creation of an experimental canopy gap with a diameter of 50 m in a mature managed Norway spruce forest. Under the canopy, the fine root length densities of trees, shrubs, and grasses and herbs were 3207, 707 and 2738 m m^–2, respectively. The fine root biomass of trees, shrubs, and grasses and herbs were 182, 47 and 52 g m^–2, respectively. Two growing seasons after gap creation hardly any fine tree roots were found in the middle part of the gap. The living tree roots in the gap edge zone were mainly located within a 5-m distance from the standing edge trees. The indices developed here to show the influence of trees on fine root lenght density clearly revealed the effect of the vicinity of living trees on fine root lenght density. The root densities of grasses, herbs and dwarf shrubs did not show a clear response to gap creation despite the increase of their foliage. Our results suggest that in boreal spruce forests a gap disturbance creates a distinct tree root gap and that the gap edge trees do not extend their root systems rapidly into the formed root gap.     

√2 Rule for Controlling the Tree Pattern in Forest Cut

A forest's productivity can be optimized by the application of rules derived from monopolized circles.A monopolized circle is defined as a circle whose center is a tree and whose radius is half of the distance between the tree itself and its nearest neighbor.Three characteristics of monopolized circle are proved.(1) Monopolized circles do not overlay each other,the nearest relationship being tangent.(2)"Full uniform pattern"means that the grid of trees (a×=N) covers the whole plot,so that the distance between each tree in a row is the same as the row spacing.The total monopolized circle area with a full uniform pattern is independent on the number of trees and π/4 times the plot area.(3) If a tree is removed,the area of some trees'monopolized circle will increase without decreasing the monopolized circles of the other trees.According to the above three characteristics,"uniform index"is defined as the total area of monopolized circles in a plot divided by the total area of the monopolized circles,arranged in a uniform pattern in the same shaped plot.According to the definition of monopolized circle,the distribution of uniform index (L) = x2(2n)/2πn for a random pattern and E(L)=1/π;the variance of L is D(L)=1/nπ2.It is evident that E(L) is independent on N and the plot area;hence,L is a relative index.L can be used to compare the uniformity among plots with different areas and the numbers of trees.In a random pattern,where L is equivalent to the tree density of the plot in which the number of trees is 1 and the area is π,the influence of tree number and plot area to L is eliminated.When n→∞,D(L)→0 and L→1/π= 0.318;it indicates that the greater the number of tree is in the plots,the smaller the difference between the uniform indices will be.There are three types of patterns for describing tree distribution (aggregated,random,and uniform patterns).Since the distribution of L in the random pattern is accurately derived,L can be used to test the pattern types.The research on Moarshan showed that the whole plot has an aggregated pattern;the first,third,and sixth parts have an aggregated pattern;and the second,fourth,and fifth parts have a random pattern.None of the uniform indices is more than 0.318 (1/Ⅱ),which indicates that uniform patterns are rare in natural forests.The rules of uniform index can be applied to forest thinning.If you want to increase the value of uniform index,you must increase the total area of monopolized circles,which can be done by removing select trees."Increasing area trees"are the removed trees and can increase the value of the uniform index.A tree is an increasing area tree if the distance between the tree and its second nearest neighbor is √2 times longer than that between the tree itself and its first nearest neighbor,which is called the √2 rule.It was very interesting to find that when six plots were randomly separated from the original plot,the proportion of increasing area trees in each plot was always about 0.5 without exception.In random pattern,the expected proportion of increasing area trees is about 0.35-0.44,which is different from the sampling value of 0.5.The reason is very difficult to explain,and further study is needed.Two criteria can be used to identify which trees should be removed to increase the uniform index during forest thinning.Those trees should be (1) trees whose monopolized circle areas are on the small side and (2) increasing area trees,which are found via the √2 rule.     

The influence of sampling design on tree‐ring‐based quantification of forest growth

Tree‐rings offer one of the few possibilities to empirically quantify and reconstruct forest growth dynamics over years to millennia. Contemporaneously with the growing scientific community employing tree‐ring parameters, recent research has suggested that commonly applied sampling designs (i.e. how and which trees are selected for dendrochronological sampling) may introduce considerable biases in quantifications of forest responses to environmental change. To date, a systematic assessment of the consequences of sampling design on dendroecological and‐climatological conclusions has not yet been performed. Here, we investigate potential biases by sampling a large population of trees and replicating diverse sampling designs. This is achieved by retroactively subsetting the population and specifically testing for biases emerging for climate reconstruction, growth response to climate variability, long‐term growth trends, and quantification of forest productivity. We find that commonly applied sampling designs can impart systematic biases of varying magnitude to any type of tree‐ring‐based investigations, independent of the total number of samples considered. Quantifications of forest growth and productivity are particularly susceptible to biases, whereas growth responses to short‐term climate variability are less affected by the choice of sampling design. The world's most frequently applied sampling design, focusing on dominant trees only, can bias absolute growth rates by up to 459% and trends in excess of 200%. Our findings challenge paradigms, where a subset of samples is typically considered to be representative for the entire population. The only two sampling strategies meeting the requirements for all types of investigations are the (i) sampling of all individuals within a fixed area; and (ii) fully randomized selection of trees. This result advertises the consistent implementation of a widely applicable sampling design to simultaneously reduce uncertainties in tree‐ring‐based quantifications of forest growth and increase the comparability of datasets beyond individual studies, investigators, laboratories, and geographical boundaries.     

Influence of scattered paddock trees on surface soil properties: A study of the Northern Tablelands of NSW

Summary Surface soil conditions were assessed under three tree species on a property near Armidale on the Northern Tablelands of NSW. In both a stocked and adjacent destocked paddock, five trees each of three eucalypt species: Eucalyptus melliodora, Eucalyptus blakelyi and Eucalyptus nova‐anglica, were selected. Soil samples were collected (depth 0–10 cm) along transects 20 m in length running from beneath the tree canopy progressively outwards into the open paddock. Six additional transects were also sampled outside the influence of the trees. Soil properties at a distance from the trees differed little between the stocked and destocked paddock with only a slight acidification in the stocked paddock. However, soil properties around the scattered trees showed considerable variation between stocked and destocked equivalents and most notably in a systematic pattern with distance from the trees themselves. For example, bulk density increased significantly, whereas soil pH, carbon, nitrogen and extractable phosphorus contents all decreased significantly with distance from the trees. However, stocking and camping had modified some of these soil properties. In the stocked paddock, the systematic change in nitrogen and phosphorus with distance from the trees was less clear and the degree of dispersion of the data was largest at the most heavily camped site. In this paddock, bulk density was also generally higher whereas pH, carbon and nitrogen contents were lower compared with the destocked equivalent. Extractable phosphorus content was also higher around the trees in the stocked paddock especially where camping activity was most intense. It is concluded that, although animal camping can modify their effects, scattered trees have a beneficial effect on soil properties and in this respect they have value in the grazing system from a soil conservation perspective.     

Cross-validation of Non-linear Growth Functions for Modelling Tree Height–Diameter Relationships

Six non-linear growth functions were fitted to tree height–diameter data of ten conifer species collected in the inland Northwest of the United States. The data sets represented a wide range of tree sizes, especially large-sized trees. According to the model statistics, the six growth functions fitted the data equally well, but resulted in different asymptote estimates. The model prediction performance was evaluated using Monte Carlo cross-validation or data splitting for 25-cm diameter classes. All six growth functions yielded similar mean prediction errors for small- and middle-sized trees. For large-sized trees [e.g. DBH (diameter at breast height)>100 cm], however, five of the six growth functions (except the Gompertz function) overestimated tree heights for western white pine, western larch, Douglas-fir, subalpine fir, and ponderosa pine, but underestimated tree heights for western hemlock and Engelmann spruce. Among these five functions, the Korf/Lundqvist and Exponential functions produced larger overestimations. The Schnute, Weibull, and Richards functions were superior in prediction performance to others. The Gompertz function seemed always to underestimate tree heights for large-sized trees.     

Empirically simulated study to compare and validate sampling methods used in aerial surveys of wildlife populations

This paper compares the distribution, sampling and estimation of abundance for two animal species in an African ecosystem by means of an intensive simulation of the sampling process under a geographical information system (GIS) environment. It focuses on systematic and random sampling designs, commonly used in wildlife surveys, comparing their performance to an adaptive design at three increasing sampling intensities, using the root mean square errors (RMSE). It further assesses the impact of sampling designs and intensities on estimates of population parameters. The simulation is based on data collected during a prior survey, in which geographical locations of all observed animals were recorded. This provides more detailed data than that usually available from transect surveys. The results show precision of estimates to increase with increasing sampling intensity, while no significant differences are observed between estimates obtained under random and systematic designs. An increase in precision is observed for the adaptive design, thereby validating the use of this design for sampling clustered populations. The study illustrates the benefits of combining statistical methods with GIS techniques to increase insight into wildlife population dynamics.     

贺兰山岩羊冬春季取食生境的比较

2003年11～12月和2004年4～6月,在贺兰山设定了25条固定样线,采用直接观察法对岩羊冬春季的取食生境选择进行了研究。结果表明,岩羊冬季对12种取食生境生态因子有选择性,偏爱选择位于山地疏林草原带,优势乔木为灰榆,乔木密度〈4株、高度4～6m,灌木密度〉5株、高度〉1．3m,食物质量〉50g,人为干扰距离〈500m,距裸岩距离〈2m的地方取食。而春季对11种取食生境生态因子有选择性,偏爱选择山地疏林草原带,优势乔木为灰榆,乔木密度〈4株、高度〈6m,灌木密度5～10株、高度1．3～1．7m,食物质量〉100g,海拔高度〈2000m,距水源距离〈500m,隐蔽级50％～75％的地点。冬春季岩羊对植被类型、地形特征、优势乔木、乔木密度、乔木高度、灌木密度、灌木距离、食物丰富度、坡向、坡度、距水源距离、人为干扰距离和隐蔽级的选择存在显著差异。主成分分析表明,冬季第1主成分的贡献率达24．493％,其中绝对值较大的权系数出现在植被类型、优势乔木、乔木高度、乔木距离、灌木密度、灌木高度、海拔高度、距水源距离和人为干扰距离等生态因子：春季第1主成分的贡献率达28．777％,其中绝对值较大的权系数出现在植被类型、乔木距离、灌木高度、灌木距离、食物丰富度、海拔高度和人为干扰距离等生态因子。随着北方地区冬春季食物数量和质量的剧烈变化,贺兰山岩羊对取食生境的利用对策也将发生一定程度的改变,与其他分布区的岩羊相比,贺兰山独特的地理位置和特殊生境使其在取食生境选择上存在很大差异。     

Nest-site habitat selected by Short-toed Eagles Circaetus gallicus in Dadia Forest (northeastern Greece)

Data concerning habitat characteristics and general physiographic characteristics at 29 Short-toed Eagle Circaetus gallicus nest-sites (circular plot of 0.4 ha centred on the nest tree) were collected and compared with the same number of paired randomly selected plots in Dadia-Lefkimi-Soufli forest complex, northeast Greece. Short-toed Eagles used southern slopes for nesting and nest-sites were often located on the upper third of each slope. Nest trees were found significantly closer to rain water gullies, to the boundary of a different habitat type, and to the nearest forest opening greater than 0.5 ha than the randomly selected nest trees. Nest-sites had a significantly lower mean score of human disturbance than random sites and were found in mature pine forest associations, dominated by Calabrian Pine Pinus brutia or Black Pine P. nigra. The total tree density of Short-toed Eagle nest-sites was lower than random sites. Canopy cover in the dominant and intermediate tree layer at nest-sites was lower than at random sites. Short-toed Eagles tended to select sites for nesting that provided a combination of easy access and maximum shelter of the nest content from predators and inclement weather. The preservation of open structure of mature pine stands on south facing slopes near clearings may be critical for the continued conservation of the Short-toed Eagle in actively managed forests, such as the Dadia-Lefkimi-Soufli forest complex.     

Tree proximity,soil pathways and common mycorrhizal networks: their influence on the utilization of redistributed water by understory seedlings

Hydraulic redistribution (HR) is a process by which water moves through plant roots from moist to dry soils. An experiment was conducted to quantify the influence of common mycorrhizal networks (CMNs) and proximity to mature HR-source trees on the water relations of surrounding seedlings. Douglas-fir (Pseudotsuga menziesii var glauca (Mirb.) Franco) seedlings were planted at four distances (0.5, 1, 2.5, and 5 m) from six mature Douglas-fir trees, either directly into soil (soil plus CMN pathway) or inside 0.5 μm mesh bags (soil-only pathway). Deuterated water was used to irrigate soil beside mature trees in order to identify different HR water pathways to surrounding seedlings. This was followed by measurements of seedling deuterium enrichment, seedling water potential, soil water potential_, gravimetric soil water content, and tree root density surrounding the seedlings. There was no significantly detectable difference in the quantity of HR water transferred to seedlings having access to soil and CMN pathways or soil-only pathways of water movement. Water from the irrigation plot contributed up to 1.4% of the water of Douglas-fir seedlings. Based on the assumption that the only pathway through which seedlings could access irrigation water was through the mature trees, we estimate that as much as 21.6% of the seedling water was supplied by the nearby tree. Seedling water potential was not significantly affected either by proximity to mature trees or pathway, suggesting HR may have compensated for increasing tree competitive effects with proximity. It is also possible that the lack of difference was due to a relatively moist summer. Our results suggest that residual mature trees are potentially important for hydraulic redistribution to regenerating seedlings in harvested dry interior Douglas-fir forests.     

渭北旱塬不同龄苹果细根空间分布特征

以渭北旱塬3龄、10龄、15龄和20龄苹果树为对象,采用根钻法,沿3等分园半径方向(径向)、距树干1.0、1.5m和2 0m处设置采样点,研究了不同树龄的细根空间分布特征.结果表明,3龄苹果细根主要分布于径向1.5m以内和垂向0.5m以上,15龄和20龄苹果细根分布超出径向2.0m和垂向1.4m,10龄细根分布范围大于3龄,与15龄和20龄接近.在根系主要分布区内3龄和10龄细根分布稀疏,15龄和20龄细根分布密集;细根空间分布演化过程可分为3个阶段,即3～10龄为细根范围扩张阶段,10～15龄为细根密度扩张阶段,15～20龄为细根密度退化阶段;苹果细根空间分布无明显方向性差异;10龄、15龄和20龄苹果表层(0～20cm)平均根长密度低于下层(20～40cm),高峰值一般出现在40～80cm,此深度以下根长密度随深度递减,3龄苹果表层平均根长密度高于下层;在径向2.0m内随径向距离增大,3龄、15龄和20龄平均根长密度逐渐降低,而10龄根长密度逐渐增加.根长密度在径向变化上存在局部变异现象.     

哈尔滨市区灰喜鹊巢址选择研究

2010年6月至9月在哈尔滨市园林科学研究所实验基地采用样方法对灰喜鹊的巢址选择特征进行研究,并且利用主成分分析法对灰喜鹊巢址样方生境因子进行检验.结果表明,灰喜鹊主要选择针叶树筑巢;在同一生境中巢间距变化小,呈均匀分布;灰喜鹊巢址选择的主要因子包括营巢树高、距最近巢距离、样方内树均高、巢树胸径、距干扰源距离、距最近树距离.这说明灰喜鹊在巢址选择过程中选择巢树和其周围的小生境.     

Biomass and distribution of fine and coarse roots from blue oak (Quercus douglasii) trees in the northern Sierra Nevada foothills of California

This research adds to the limited data on coarse and fine root biomass for blue oak (Quercus douglasii Hook and Arn.), a California deciduous oak species found extensively throughout the interior foothills surrounding the Central Valley. Root systems of six blue oak trees were analyzed using three methods — backhoe excavation, quantitative pits, and soil cores. Coarse root biomass ranged from 7 to 177 kg per tree. Rooting depth for the main root system ranged from 0.5 to 1.5 m, with an average of 70% of excavated root biomass located above 0.5 m. Of the total biomass in excavated central root systems, primary roots (including burls) accounted for 56% and large lateral roots (> 20 mm diameter) accounted for 36%. Data from cores indicated that most biomass outside of the root crown was located in fine roots and that fine root biomass decreased with depth. At surface depths (0–20 cm), small-fine (< 0.5 mm diameter) roots accounted for 71%, large-fine (0.5–2.0 mm) for 25%, and coarse (> 2 mm) for 4% of total root biomass collected with cores. Mean fine root biomass density in the top 50 cm was 0.43 kg m⁻³. Fine root biomass did not change with increasing distance from the trees (up to approximately 5 m). Thus, fine roots were not concentrated under the tree canopies. Our results emphasize the importance of the smallest size class of roots (<0.5 mm), which had both higher N concentration and, in the area outside the central root system, greater biomass than large fine (0.5–2.0 mm) or coarse (> 2.0 mm) roots. This revised version was published online in June 2006 with corrections to the Cover Date.