Growth, biomass yield and biomass functions for plantation-grown Nauclea diderrichii (de wild) in the humid tropical rainforest zone of south-western Nigeria

Adequate management of forest plantation requires estimation of growth and biomass yield and consequently, the fitting of functions for estimating biomass. Growth, biomass yield and biomass functions for estimating biomass of Nauclea diderrichii plantations in Omo forest reserve, Nigeria are described. Data were obtained from 30 temporary sample plots selected from stands that are 5-30 years old. A total of 81 trees were harvested for biomass estimation. Mean tree diameter at breast height (dbh), total height and stand bole volume ranged from 9.6 to 29.3 cm; 9.0 to 23.6m and 23.27 to 535.52 m(3)ha(-1), respectively while Total Above Ground Biomass (TAGB) varied from 32.5 t ha(-1) to 287.5 t ha(-1) between 5 and 30 years. Biomass allocations to stem, branch and foliage were 84.5%, 13.5% and 3%, respectively. All biomass components could be described precisely by dbh alone (R(adj)(2)>0.97), with very low standard errors of estimates. Little improvement in the precision of the functions was achieved by including total height. In addition, the residuals of regression functions with only dbh were generally more constrained than those that included total height. Consequently, the functions with dbh alone and its derivative as independent variables were recommended for estimating biomass of opepe in Nigeria.     

Development of a Compatible Taper Function and Stand-Level Merchantable Volume Model for Chinese Fir Plantations

Chinese fir (Cunninghamia lanceolata [Lamb.] Hook) is one of the most important plantation tree species in China with good timber quality and fast growth. It covers an area of 8.54 million hectare, which corresponds to 21% of the total plantation area and 32% of total plantation volume in China. With the increasing market demand, an accurate estimation and prediction of merchantable volume at tree- and stand-level is becoming important for plantation owners. Although there are many studies on the total tree volume estimation from allometric models, these allometric models cannot predict tree- and stand-level merchantable volume at any merchantable height, and the stand-level merchantable volume model was not seen yet in Chinese fir plantations. This study aimed to develop (1) a compatible taper function for tree-level merchantable volume estimation, and (2) a stand-level merchantable volume model for Chinese fir plantations. This “taper function system” consisted in a taper function, a merchantable volume equation and a total tree volume equation. 46 Chinese fir trees were felled to develop the taper function in Shitai County, Anhui province, China. A second-order continuous autoregressive error structure corrected the inherent serial autocorrelation of different observations in one tree. The taper function and volume equations were fitted simultaneously after autocorrelation correction. The compatible taper function fitted well to our data and had very good performances in diameter and total tree volume prediction. The stand-level merchantable volume equation based on the ratio approach was developed using basal area, dominant height, quadratic mean diameter and top diameter (ranging from 0 to 30 cm) as independent variables. At last, a total stand-level volume table using stand basal area and dominant height as variables was proposed for local forest managers to simplify the stand volume estimation.     

樟子松人工林树冠表面积及体积预估模型的研究

基于樟子松(Pinus sylvestris var. mongolica)人工林6块固定标准地30株枝解析数据,在分析树冠表面积和树冠体积与林分变量和林木变量的基础上,利用幂函数建立了树冠表面积（CSA）和树冠体积(CV)的预估模型,同时还对林木材积生长量与CSA和CV进行了相关分析。研究结果表明：樟子松人工林树冠表面积和树冠体积随着林木胸径、树高和冠长的增大而增大,林木材积生长量与树冠表面积和树冠体积均明显呈线性关系。不同林分条件的樟子松人工林CSA和CV随林分年龄和胸径的增大而增大,CSA随林分密度的增大而减小,而CV与林分密度相关不紧密。林分树冠表面积和树冠体积预估模型的检验结果表明,两个模型的平均相对误差都在±8%之内,预估精度均大于91%,说明所建模型可以很好地预估樟子松人工林不同林分条件下的林木树冠表面积和树冠体积。     

Allometric equations to predict the total aboveground biomass of tree species in a planted forest in Egypt

The aim of this study is to estimate the total above‐ground biomass (TAGB), stem height (H), diameter at breast height (dbh) and basal area of five tree species (ages 7‐8 years) irrigated by municipal sewage water in the Egyptian‐Chinese friendship forest, Sadat City, Egypt. From the biomass data that obtained through destructive sampling, models for predicting aboveground biomass were developed. The highest values for stem density and height were estimated for Eucalyptus citriodora, while the lowest value for density was obtained for Dalbergia sissoo and stem height for Khaya senegalensis. The highest values for basal area and dbh were obtained for Casuarina spp., while the lowest values were recorded for Dalbergia sissoo. Eucalyptus camaldulensis had the highest stand stem biomass and TAGB (55.5, 83.9 t DW ha^‐1, respectively). In addition, Casuarina spp. had the highest leafy branches biomass (32.5 t DW ha^‐1) while Dalbergia sissoo had the lowest values for all tree components. All the generated allometric equations had high correlation coefficients at high probability levels. Moreover, the results revealed that not only the dbh data can be used as independent variable for biomass determination, but also stem height and size index are recommended for biomass estimation (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Modelling fallen branch volumes in a temperate eucalypt woodland: implications for large senescent trees and benchmark loads of coarse woody debris

Fallen branches are a substantial component of coarse woody debris and a key ecological resource. The depletion of stocks of coarse woody debris since European settlement has contributed to the degradation of Australian grassy box woodlands, including the loss of biodiversity. Restoration options for remnant woodlands include the augmentation of coarse woody debris stocks. However, the extensive modification of grassy box woodlands has left few reference sites for establishing benchmarks to guide such restoration. In this paper we demonstrate a method for predicting fallen branch debris loads in the absence of reference sites, using data from a yellow box–red gum woodland. Our methodology is in two stages: first, the total volume of branch debris under individual trees was modelled; and second, these models were applied to groups of trees to predict stand‐level loads of fallen branch debris. Although the models were developed for yellow box–red gum woodlands, the methodology would be applicable to other communities that lack reference sites. Predicted benchmark loads of fallen branch debris for yellow box–red gum woodland were between 7.0 m³ ha^?1 and 11.9 m³ ha^?1. Large senescing trees contributed the bulk of fallen branch debris. Model predictions indicated a 100‐cm diameter at breast height (dbh) tree was 10 times more likely to produce debris than a 50‐cm dbh tree, and if debris was present a 100‐cm dbh tree produced approximately 10 times the volume of branch debris produced by a 50‐cm dbh tree. These results highlight the importance of large senescing trees for the production of fallen branch debris and support the keystone role of large trees within remnant woodlands, and the need to conserve these structures. Our results also support the active management of regrowth woodland stands to facilitate the progression of individual trees to maturity and senescence. In particular, thinning of regrowth stands may promote the growth of retained trees, ensuring they contribute to fallen branch debris stocks with a minimum time lag.     

Allometric Biomass,Biomass Expansion Factor and Wood Density Models for the OP42 Hybrid Poplar in Southern Scandinavia

Biomass and biomass expansion factor functions are important in wood resource assessment, especially with regards to bioenergy feedstocks and carbon pools. We sampled 48 poplar trees in seven stands with the purpose of estimating allometric models for predicting biomass of individual tree components, stem-to-aboveground biomass expansion factors (BEF) and stem basic densities of the OP42 hybrid poplar clone in southern Scandinavia. Stand age ranged from 3 to 31 years, individual tree diameter at breast height (dbh) from 1.2 to 41 cm and aboveground tree biomass from 0.39 to 670 kg. Models for predicting total aboveground leafless, stem and branch biomass included dbh and tree height as predictor variables and explained more than 97 % of the total variation. The BEF was approaching 2.0 for the smallest trees but declined with increasing tree size and stabilized around 1.2 for trees with dbh >10 cm. Average stem basic density was more than 400 kg m^?3 for the smallest trees but declined with increasing tree height and stabilized around 355 kg m^?3, at a tree height of about 20 m. Existing biomass functions from the literature all underestimated the measured sample tree biomass. Possible explanations include not only differences in competition among trees in the examined stands and site conditions but also differences in sampling procedures. We observed that basic density increased with height above the ground. This trend may have led to the observed underestimation by existing biomass functions including only few samples from the lower end of the stems.     

How do Araucaria angustifolia trees grow in overstocked stands?

The objective of this study was to evaluate growth along the stem of Araucaria angustifolia (Bertol.) Kuntze trees competing in overstocked stands, in order to identify periods when growth and trunk shape are differentiated during the trees' lifespan. The research was carried out in a planted forest of Araucaria angustifolia established in 1946 in the Açungui National Forest in Campo Largo, Paraná, Brazil, when these trees were 65 years old. One thinning was recorded, at some time between 1970 and 1980. Forty-six trees were selected and divided into three development classes (DC) at 65 years of age; these classes considered diameter at 1.30 m (breast height, dbh) with a range of 20 cm (from 10 cm to 70 cm). In addition to dbh, total tree height, and crown height and diameter were measured in the field. From each tree, 14 disks were removed to analyze growth rings and confirm the age of the stand. Some trees in the smallest DC (10 ≤ dbh < 30 cm) were the product of natural regeneration (younger trees that grew after the initial planting). In 63% of the trees, at least one growth ring was missing at breast height. Missing rings at breast height were more common in trees with smaller dbh and crown diameters. The need for more growing space was observed at different periods during the studied lifespan of the trees from three DCs. It resulted in changes in stems shape from conical to cylindrical. Different growth patterns could be observed during the lives of some trees as they outgrew their competition.     

Determinants of tree survival at local scale in a sub-tropical forest

Tree survival is a critical driver of stand dynamics, influencing forest structure and composition. Many local-scale drivers (tree size, abiotic and biotic factors) have been proposed as being important in explaining patterns of tree survival, but their contributions are still unknown. We examined the relative importance of these local drivers on tree survival using generalized linear mixed models in an old-growth sub-tropical forest in south China at three levels (community, guild, and species). Among the variables tested, tree size was typically the most important driver of tree survival, followed by abiotic and then biotic variables. Tree size has a strongly positive effect on tree survival for small trees (10–30 cm dbh) and shade-tolerant tree species. Of the abiotic factors tested, elevation tended to be more important in affecting tree survival than other topographic variables. Abiotic factors generally influenced survival of species with relatively high abundances, for individuals in smaller size classes and for mid-tolerant species. Among biotic factors, we found that the mortality of tree species was not driven by density- and frequency-dependent effects in this sub-tropical forest, as indicated by the results of both total basal area of neighbors and the proportion of conspecific neighbors in our study. We conclude that the relative importance of variables driving patterns of tree survival varied greatly among tree size classes, species guilds, shade tolerance, density, and abundance classes in this sub-tropical forest. These results also provide critical information for future studies of forest dynamics and offer insight into forest management in this region.     

不同林分起源的相容性生物量模型构建

目前为止已有不同方法构建生物量相容性模型,但不同林分起源的生物量相容性模型很少报道。针对此问题,以150株南方马尾松(Pinus masson iana)地上生物量数据为例,利用比例平差法和非线性联立方程组法建立不同起源地上生物量以及干材、干皮、树枝和树叶各分项生物量相容的通用性模型。根据分配层次不同,两种方法又各自考虑总量直接控制和分级联合控制两种方案。从直径、树高、地径、枝下高和冠幅5个林分变量中选取不同的变量构建一元、二元和三元生物量模型,并利用加权最小二乘回归法消除生物量模型中存在的异方差性。结果为:比例平差法和非线性联立方程组法都能有效保证各分项生物量总和等于总生物量,模型预测精度满足要求。总体而言,非线性联立方程组方法比比例平差方法精度高,同时两种方法中总量直接控制法比分级联合控制法预测效果好;各分项生物量模型本身作为权函数能有效消除异方差;各分项对应的三元生物量模型预测精度最高,其次是二元生物量模型,最低是一元生物量模型,但这些差异不是很大。总之,为权衡考虑模型预测精度和调查成本,建议把直径和树高作为协变量利用总量直接控制非线性联立方程组法对不同起源生物量建模。     

三种林分生物量估算方法的比较

区域森林生物量的估算方法是人们目前关注的焦点,建立林分生物量模型成为一种趋势.本文以吉林省落叶松人工林固定样地为例,采用非线性似乎不相关回归法构建2种林分生物量模型,即基于林分变量的林分生物量模型(模型系统Ⅰ)和基于生物量换算系数的林分生物量模型(模型系统Ⅱ),给出落叶松人工林固定生物量换算系数值,并比较了3种林分生物量估算方法的预估精度.结果表明: 所建立的2种林分生物量模型中,总生物量和树干生物量模型拟合和预测效果较好,其R_a²>0.95,且均方根误差(RMSE)、平均预测误差(MPE)和平均绝对误差(MAE)都较小.树叶和树枝生物量模型拟合和预测效果相对较差,其模型的R_a²<0.95.模型系统Ⅰ和模型系统Ⅱ的预测精度均优于固定生物量换算系数法.基于生物量换算系数的林分生物量模型属于材积源生物量法,其本质与基于林分变量的林分生物量模型不同,但二者的预测效果相当.固定生物量换算系数的预测能力较差,将生物量与蓄积量之比假定为恒定常数是不恰当的.此外,为了使模型参数估计更有效,所建立的生物量模型应当考虑林分总生物量及各分项生物量的可加性.     

基于抚育间伐效应的长白落叶松人工林两阶段枯死模型

1972和1974年分别在黑龙江省江山娇林场及孟家岗林场设置10块长白落叶松人工林固定样地(8块抚育间伐样地、2块对照样地),采用连年复测数据,分析抚育间伐对人工长白落叶松样地枯死与单木枯死的影响.基于二分类变量Logistic回归,建立了样地枯死及样地内单木枯死概率的两阶段模型(Ⅰ:抚育间伐后样地水平枯死概率模型;Ⅱ:枯死样地中单木水平枯死概率模型),采用广义估计方程(GEE)方法对模型参数进行估计.根据敏感度和特异度曲线相交点确定枯死概率最优临界点.结果表明: 样地数据按照抚育间伐次数分为4组分别建模(模型1～模型4).在模型1中,地位指数、林分年龄的自然对数、抚育间伐年龄及强度为显著自变量;模型2～模型4采用主成分分析法建模,主成分包含林分年龄、每公顷株数、平均胸径及抚育间伐因子,说明抚育间伐因子对样地枯死概率有显著影响.抚育间伐对枯死样地中单木枯死概率无显著影响,单木枯死概率模型中显著性自变量为林分初植密度、年龄、林木胸径的倒数及林分中大于对象木的所有林木断面积之和.样地枯死概率模型及单木枯死概率模型Hosmer和Lemeshow拟合优度检验均不显著,模型AUC均在0.91以上,估计正确率均超过80%,说明模型拟合效果较好.     

落叶松人工林生物量模型研究

以不同年龄、不同密度的落叶松（Larix olgensis）人工林为研究对象,基于19块标准地95株标准木的树干解析、枝解析的生物量数据,研究不同大小树木因子（胸径、树高、冠幅等）与单木各分量（树干、枝、叶）生物量之间的关系,应用统计分析软件建立落叶松单木各部分生物量的回归模型。利用单木各部分生物量回归模型方程估测落叶松人工林各林分的总生物量,并分析了不同年龄及林分密度下林分生物量的变化规律：林分的生物量随年龄的增加而不断增长,树干的生物量的比例是最大的,同时也是随着年龄的增长而不断的增加,而树枝和树叶的生物量的比例比较小,林分的生物量随林分密度的增加而不断增加。最后建立林分生物量模型,为落叶松人工林的研究提供基础资料,为了解落叶松人工林的生产力,对其进行合理经营提供科学依据。     

天然更新的檫木林的生物量和生产力

通过对标准木的测定,建立相对生长方程,了福建省建阳书坊林场天然更新的檫木（Sassafras tzumu）林分的生物量和生产力,结果表明：20年生檫木林分平均现存生物量为58693kghm^-2,平均年生产力为4259kghm^-2,檫木生物量与胸径间存在极显著回归关系,大部分生物量集中于树体中下部,生物量的径级分布以20cm径级积累值最大。这些结果对阔叶林的营造及其生态系统结构与功能的研究具有现实意义。     

Estimation of stem and tree level biomass models for Prosopis juliflora/pallida applicable to multi-stemmed tree species

The aim of this paper is to develop biomass models for commonly multi-stemmed Prosopis juliflora/pallida trees. The data were collected on three of the Cape Verde islands (Maio, Santiago and Santo Antao). The dataset covers 240 trees containing 1,882 stems with stem diameter at breast height over 2 cm; of that 255 individual tree stems were sampled destructively. These calibration data were used to construct stem and tree-level models for estimation of total aboveground biomass and its fine and course fractions with diameter threshold of 5 cm. A set of parameterized biomass models for multi-stemmed Prosopis spp. trees suited for biomass estimation at tree and stem levels using appropriate set of independent variables, commonly available in forest inventory programs, was created. The effect of site (island) on tree allometry was not detected. The two-phase construction of tree biomass models based on destructive sampling limited to individual stems combined with a routine field measurement of entire multi-stemmed tree specimen represents a practicable approach leading to biomass and carbon assessment that may be generally suited for tree species with complex multi-stemmed growth form similar to that of Prosopis spp.     

杉木风景游憩林冠径与胸径关系研究

为研究杉木风景游憩林标准林分密度（立木株数）,确定合理抚育间伐强度提供科学依据。本文在福建将乐国有林场通过设置杉木人工林39块标准地和2 906株每木检尺实测数据,建立了福建将乐杉木人工林树冠径与胸径以及冠径与胸径比值(cd/D)关系,并分析了冠径与胸径比值在风景游憩林树木空间、林分密度和间伐强度中的应用。研究表明:胸径在2~43 cm之间时,相关系数(R²)达0.919 5,呈显著线性相关,其中2~35 cm模型精度较高,35~43 cm误差较大。通过对不同大小的杉木(cd/D)比值进行分析,得出随着胸径增大比值是逐渐减小的,并且减小的趋势随着胸径的增大趋于平稳,最后趋于一个常数。     

Acorn production prediction models for five common oak species of the eastern United States

Acorn production varies considerably among oak (Quercus) species, individual trees, years, and locations, which directly affects oak regeneration and populations of wildlife species that depend on acorns for food. Hard mast indices provide a relative ranking and basis for comparison of within- and between-year acorn crop size at a broad scale, but do not provide an estimate of actual acorn yield—the number of acorns that can potentially be produced on a given land area unit based on the species, number, and diameter at breast height (dbh) of oak trees present. We used 10 years of acorn production data from 475 oak trees to develop predictive models of potential average annual hard mast production by five common eastern oak species, based on tree diameter and estimated crown area. We found a weak (R² = 0.08–0.28) relationship between tree dbh and acorn production per unit crown area for most species. The relationship between tree dbh and acorn production per tree was stronger (R² = 0.33–0.57). However, this is because larger-dbh trees generally have larger crowns, not because they have a greater capacity to produce more acorns per unit crown area. Acorn production is highly variable among individual trees. We estimated that dbh of at least 60 dominant or codominant oak trees per species should be randomly sampled to obtain an adequate representation of the range of dbhs (≥12.7 cm dbh) in a given forest area, and achieve precise estimates when using these equations to predict potential acorn production. Our predictive models provide a tool for estimating potential acorn production that land managers and forest planners can apply to oak inventory data to tailor estimates of potential average annual acorn production to different forest management scenarios and multiple spatial scales. © 2011 The Wildlife Society.     

江西省丘陵区湿地松多效益经营模式适宜经营密度的研究

通过拟合林分枝叶生物量及林下植被生物量与林分郁闭度的关系求算出湿地松水保林的适宜郁闭度范围,利用林分郁闭度与林分平均直径和林分株数密度的关系式,导算出湿地松水保林的适宜密度,用公式N1=15761.64/D表示,以价值生长量最大作最优指标函数,采用动态规划方法求算出材脂两用林的最适经营密度线N2＝23625．12D^-1.1523,综合得出江西省丘陵区湿地松多效益经营模式适宜经营密度就是以上两条密度线所夹范围。     

樟子松人工林一级枝条基径和枝长模型的研究

以东北林业大学帽儿山实验林场樟子松人工林为研究对象,采用枝解析的方法,于2002年、2003年测定了53株林木（年龄17~38 a,直径8.61~21.5 cm,树高7.48~18.24 m）的树冠变量,建立了基于总着枝深度（DINC）和树冠内一级枝条基径（BD）、枝长（BL）的预估模型。对于大小相同树木的一级枝条, 这些树冠变量随着DINC的增加而增大,而林木的胸径（DBH）、树高（HT）变量又很好地反映了不同大小树木的基径和枝长的变化。采用独立检验样本对构建的树冠内一级枝条基径和枝长模型进行了拟合统计量和精度检验,结果表明：模型预测效果良好,精度均达到95%以上。构建的一级枝条基径和枝长模型为进一步合理地描述樟子松人工林树冠的形状及其变化以及三维可视化经营提供依据。     

Tree population studies in low-diversity forests,Guyana. I. Floristic composition and stand structure

Studies were undertaken on the floristic composition and stand structure of four 1 hectare plots in the lowland forests of Kurupukari, Guyana. A total of 3897 trees, covering 153 species and 31 plant families were recorded at greater than 5 cm diameter at breast height (dbh). The number of species per hectare ranged from 61 to 84 (>5.0 cm dbh) and 50–71 (>10.0 cm dbh). The total number of trees per hectare varied two-fold between study plots, with 45–50% of the trees within the 5–10 cm size-class. Mean total basal area varied from 32.39–34.63 m² per 100 m². The four most dominant plant families represented 43.8% of the total number of trees, while representing only 11.2% of the species. No one plant family dominated in more than one of the four study plots, and all four plots held at least one plant family with more than 20% of the total number of trees. Although 14 tree species were common to all four plots, only 26%–35% of the species were represented by a single tree. Between three and seven species represented 50% of the trees within all size-classes, with species dominance occurring within the highest density plot.These tropical forest types of central Guyana may represent some of the lowest diversity forests in the neotropics, whereby the total number of tree species is relatively limited, typically with six dominant canopy species, but the relative abundance of these species is highly variable between the forest types. Mechanisms influencing the competitive interactions associated with species dominance are discussed in relation to the importance of mycorrhizae and the persistence of species dominance.     

Effects of soil physicochemical properties and stand age on fine root biomass and vertical distribution of plantation forests in the Loess Plateau of China

The responses of aboveground parts of the forest to changes in environmental factors and stand age is well studied, but the same is not true for the belowground parts of the forest. Two plantation black locust (Robinia pseudoacacia L.) forest sites were taken in the Loess Plateau of China, one in the drier, infertile, more sandy area of the middle Loess Plateau, and another in the wetter, fertile, more clay-filled area of the southern Loess Plateau. At each site, both a younger (8-year-old) plantation stand and an older (30-year-old) plantation stand were included to study the effects of soil physicochemical properties and stand age on the fine root (<2?mm) biomass and vertical distribution of black locust forests. Root samples were taken with soil cores to a depth of 100?cm. The fine root biomass decreased from the middle site to the southern site for both stand ages, as expected, and the decrease could be due to a higher fine root N concentration associated with a higher fine root turnover rate at the southern site. There was a similar rooting pattern, though not deeper, in the drier, sandy site as predicted based on soil water infiltration and evaporation demands. The different effects of stand characters (e.g., tree density, tree height) on the fine root distribution as compared with the environmental properties may contribute partly to the similar pattern found in the two sites. The fine root biomass increased with stand age in both sites. In contrast to the evident difference in fine root biomass, there was no clear trend in the fine root vertical distribution pattern with stand age. Our results indicate that fine roots are likely to respond to changes in soil physicochemical properties and stand age by changing fine root biomass rather than by varying rooting pattern.