Crown radius of pedunculate oak (Quercus robur L.) depending on stem size,stand density and site productivity

Crown size is a good indicator of the growth potential of trees and is often used in forest management for outlining thinning guidelines or constructing forest growth models. The aim of this study was to analyse mean crown radius as a function of stem size, stand density and site productivity in even-aged stands of pedunculate oak (Quercus robur L.). Data included measurements of 620 trees from 53 plots in nine thinning experiments and one operational stand in Sweden, Denmark and Great Britain, representing a wide spectrum of thinning practices ranging from the strictly unthinned control to extremely heavy thinning with essentially solitary trees. Three sets of models were constructed based on different predictor variables, including indicators of individual stem size (diameter at breast height, DBH), stand density/thinning grade (quadratic mean diameter and stand basal area) and site productivity (stand top height). Preliminary results indicated a significant effect of DBH and (nominal) thinning grade on crown radius. The response pattern of the final models indicated an increasing crown radius with increasing DBH, with increasing thinning grade (decreasing stand density) and with decreasing site productivity. The models are valid for predicting the crown radius of pedunculate oak in even-aged forest stands.     

Possibilities for Harvester-based Forest Inventory in Thinnings

This study investigated the possible estimation of forest characteristics using the information collected by the harvester in first thinnings. For the analysis a complete forest inventory was carried out in a stand, which was subsequently thinned. The global mean values of tree diameter, tree height, basal area and stem density were estimated, and further, a spatial analysis was carried out to investigate whether the data collected by the harvester could be used to generate a continuous spatial model of the forest. The results indicated that the global mean diameter and height may be estimated, whereas area-related properties, such as basal area and stem density, are more difficult to estimate. The spatial distribution of the diameter and height remained similar after the thinning, whereas the basal area and stem density had become more homogeneous after the thinning. From the trees removed in the thinning a continuous spatial model of tree diameter was developed. It reproduced the spatial structure of the original trees to some extent ( R 2 = 0.27, RMSE = 14.3 mm).     

木麻黄生长与收获模型系统的研究

利用海南文昌2005年森林资源二类调查的木麻黄工业原料林样地资料,通过参数置换法,构建了以优势高模型为基础,以断面积预估为中心,将蓄积量作为目标变量的生长与收获模型系统。结果表明：组成模型系统的各模型的拟合精度较高,各模型的预估值与观测值差异不显著,适应性较好,能对木麻黄的优势高、断面积和蓄积量生长进行正确预估,可用于研究区木麻黄工业原料林的生长与收获预估。研究方法为一次性调查数据生长模型及类似模型的研建提供了经验和借鉴,并为当前缺少长期定位观测数据和大量解析木数据的森林经营单位编制森林经营方案提供了理论基础。     

Growth and structure development of semi-natural larch-spruce-fir (Larix olgensis–Picea jezoensis–Abies nephrolepis) forests in northeast China: 12-year results after thinning

Analyzing and understanding the structure and growth dynamics of semi-natural plantations is useful for their management. Since 1987, 16 plots with 4 treatments (CT: control; LT: light thinning; MT: medium thinning; and HT: heavy thinning) by 0, 20, 30 and 40% of basal area removal, respectively, and four replications were established in semi-natural larch-spruce-fir forests in northeast China. The structure and growth dynamics of semi-natural larch-spruce-fir stands and the effects of thinning on the growth, structure and diversity were examined. A mixed model repeated measures analysis of variance (RMANOVA) was used to test the effects of treatment and time.

Results showed that differences in periodic annual increment (PAI) of stand basal area and volume and the individual diameter and volume among treatments changed over time in a complex statistical interaction. Thinning, however, had a significant effect on growth at tree and stand levels 12 years after thinning while the PAI of the diameter, basal area and volume was positively correlated with thinning intensity. No significant differences were found in the total stand yield among treatments. Composition of tree species group (larch, other conifers and deciduous trees) during monitoring years did not change significantly. Moreover, no significant differences were observed in tree species and size diversity among treatments in the years following thinning. Both thinning and control plots had similar understory plant diversity after the 12 year period. Univariate point pattern analysis revealed that clumped and random distributions were dominant for tree species groups in this study. The current species composition and regeneration dynamics within these semi-natural plantations suggested a development towards mixed coniferous and broad-leaved forests. Management implications for the transformation from larch plantations towards mixed broad-leaved Korean forests with a more diverse structure, the climax vegetation in this region, were discussed.     

抚育间伐对辽东山区3种林型林分总断面积和总收获量的影响

利用几十年的定位观测数据,分析了抚育间伐对辽东山区红松人工林、天然次生蒙古栎林和人工诱导的阔叶红松林3种林型林分总断面积和总收获量的影响。结果表明:与对照区相比,抚育间伐没有提高红松人工林的林分断面积和蓄积总生长量,但极强度和强度间伐能提高红松人工林的林分断面积生长率。林分总断面积随着间伐强度的增加先升高后降低,各间伐强度均能提高林分总断面积,极强度间伐除外。抚育间伐能提高红松人工林林分蓄积生长率,弱度区除外;红松人工林林分总收获量随着间伐强度的增加先升高后降低,各间伐强度均能提高林分总收获量,中度间伐效果最好。抚育间伐能提高蒙古栎林林分断面积和蓄积总生长量、生长率以及林分总断面积和总收获量,各指标随着间伐强度的增加先升高后降低,中度间伐效果最好。抚育间伐能提高人工诱导的阔叶红松林林分断面积和蓄积总生长量、生长率以及林分总断面积和总收获量,林分断面积和蓄积总生长量、林分总断面积和林分总收获量随着间伐强度的增加而升高,林分断面积和蓄积生长率随着间伐强度的增加先升高后略有降低,强度间伐效果最好。可见,合理的间伐强度能够提高3种林型的林分总断面积和总收获量。     

抚育间伐对人工红松林生长效应的影响

利用不同间伐强度后40 a的人工红松林,连续抚育3次的长期定位观测资料,分析了抚育间伐对人工红松单木胸径和材积、林分断面积和蓄积、林分枯损和总收获量的影响。研究结果表明:间伐可以增加单木平均胸径和材积的生长率,且不同间伐强度表现为相同的规律,即中度(33.2%)强度(43.4%)弱度(23.1%)对照(0.0%);间伐后林分的断面积和蓄积生长率,具有相似的自然规律,间伐样地的生长率均高于对照;林木枯损率随间伐强度的增加而降低;间伐后的林分总收获量平均增加11.6%,间伐林分之间差别不明显。在整个研究阶段,不同的抚育阶段表现不同的规律,抚育间伐可以延缓单木胸径和材积生长速度的降幅;而不同抚育阶段内,林分断面积和蓄积生长率均为增长,也就是说,在一定阶段内间伐可以有效地提高林分平均断面积和蓄积生长率;从林分枯损状况来看,应该减少间伐间隔期。     

基于混合效应模型的杉木人工林蓄积联立方程系统

建立江西杉木人工林基于非线性混合效应方法的林分优势木平均高和断面积模型以及基于对数形式线性混合效应蓄积模型的联立方程组,利用验证数据与传统模型回归方法的模拟结果进行比较分析。结果表明,优势木平均高是联立方程组最基本的组成部分。通过考虑优势木平均高和林分断面积模型中参数的随机效应以及3个因变量间的相关性,则蓄积模型中参数的随机效应可以忽略。优势木平均高决定着林分断面积预测的准确性,而优势木平均高和林分断面积又是预测蓄积的主要误差来源。基于混合效应模型方法的模拟结果明显好于传统回归估计方法。进行预测时,通过解释联立方程组中因变量相互间的相关性,利用已被观测的变量能够提高未观测变量的估计精度。     

Vegetation structure, floristic composition and growth characteristics of Aucoumea klaineana Pierre stands as influenced by stand age and thinning

The coastal forest of Gabon abounds in monospecific secondary Aucoumea klaineana stands derived from natural regeneration after shifting cultivation. This paper aims to describe the changes in the structure and dynamics of these stands with age. It then assesses the impact of selective thinning in the upper storey on both structural and dynamic parameters.

The experiment consisted of 34 Permanent Plots in stands from establishment to more mature stages (ca. 50 years old). Thirteen plots (17–45 years old) were thinned. More than 80% of the removal came from supernumerary dominant A. klaineana.

A. klaineana represented 60% of the total density in stands ca. 15 years old but >90% of the dominant trees in older stands. The changes with age in the floristic composition of the unthinned stands showed three successional stages during which pioneer species associated with A. klaineana (from establishment to ca. 15 years) were progressively replaced by mature forest species.

Basal area increased and density decreased with age before reaching stable values at ca. 40–45 years. Mortality was very high in young stands but decreased in the older ones. Mortality generally affected small diameter individuals in the dominated storey. Diameter and basal area increments showed that the stand growth resulted from the growth of dominant A. klaineana. Diameter increments of A. klaineana were elevated during the first years of colonisation (1.9 cm/year) and were still ca. 0.7 cm/year for 50-year-old dominant trees.

Thinning did not increase the mortality of the dominant population. It favoured the individual growth of A. klaineana. The gain was substantial for dominated trees and small dominant trees (from 60 to 100%) but was lower for large dominant trees (ca. 25–30%). Therefore, stimulation of individual growth did not compensate for the loss of basal area at the stand level.     

Estimation of a basal area growth model for individual trees in uneven-aged Caspian mixed species forests

The aim of this study was to estimate a basal area growth model for individual trees in uneven-aged Caspian forests. A survey was conducted in order to find a natural forest without any harvesting activities, a so called ‘untouched forest’ and an area was selected from the Iranian Caspian forest. Three sample plots in the same aspect and of the same forest type were selected. In each plot, total tree height, diameter at breast height, distance of neighbor trees and azimuth were measured. Thirty trees were selected and drilled with increment borer to determine the increment model. Regression analysis was used to estimate the growth model. Results show that, for individual trees, there is a significant nonlinear relationship between the annual basal area increment, as the dependent variable, and the basal area. The results also show that the basal area of competing trees has a positive influence on growth. That the increment is higher with more competing neighboring trees is possibly because plots with higher volume per hectare and more competition, most likely also have higher site index or better soil or better site productivity than the plot with lower volume per hectare.     

不同间伐强度对阔叶混交林生长及径级结构的影响

通过对辽东山区阔叶混交林进行抚育间伐试验,结果表明:适度的抚育间伐可促进阔叶混交林林木胸径和蓄积生长,林分平均胸径和蓄积生长率随着间伐强度的增加先升高后降低,其中弱度间伐区林分平均胸径生长率最大,中度间伐区林分蓄积量生长率最大。间伐效果表现在伐后最初几年,随着时间的推移,林分平均胸径和蓄积生长率逐渐降低,各间伐区差异逐渐变小。随着间伐强度和林龄的增加,峰值向大径级位置偏移,分布范围明显地向大径级扩展。由不同间伐强度林分径级分布范围看,伐后4~21a,经过间伐的林分,径级分布峰值比对照区提高1~2径级。与对照区相比,各间伐区林分自然径级最大值、极差和直径离散度均有所增加,总体上表现出随着间伐强度和林龄增加而加大的趋势。综合考虑,中度间伐最有利于提高林分生产力,改善林分直径结构。     

桂西南马尾松人工林生长对不同强度采伐的动态响应

[目的]研究不同强度采伐下马尾松的生长动态,筛选适宜的采伐强度,为马尾松人工林近自然经营提供技术支撑。[方法]2007年10月在14年生马尾松人工林(保存密度1 100株·hm~(-2))内进行采伐试验,设置4个采伐强度,即保留密度分别为225、300、375、450株·hm~(-2),以不采伐为对照;其后,自2008年开始连续8 a,每2 a测定1次马尾松的胸径、树高、枝下高和冠面积等生长指标,并计算单株材积和林分蓄积量,应用方差分析和Duncan多重比较分析生长指标对不同采伐强度的动态响应。[结果]表明:采伐强度显著影响林分生长,其中,林分平均胸径、单株材积、冠面积的年均增长量随保留密度增大而减小,但均显著高于对照(P0.05)。采伐后第1 3年,马尾松冠面积增长量显著高于采伐后期,胸径则在采伐后第3 5年最高,而不同采伐强度对林分树高生长影响不明显。保留密度显著影响林分枝下高和蓄积量的动态变化,其年均增长量随密度增大而递增。5个处理间林分蓄积年均增长量的差异随林龄的增大而逐渐缩小。[结论]马尾松人工林生长对不同强度采伐的动态响应以树冠最敏感,冠面积首先陡然增大,进而引起胸径的快速生长。树高和枝下高在采伐后年均增量变化相对平稳。4个采伐强度均显著促进单株材积生长,而仅保留密度为225株·hm~(-2)的采伐对林分蓄积增长量影响显著。综合比较林分的单株材积和林分蓄积连年增长量,建议在桂西南15年生马尾松人工林近自然经营中宜选择300株·hm~(-2)的保留密度进行采伐。     

Thinning intensity and growth response in SW-European Scots pine stands

The effect of different thinning intensities on growth and yield was studied in Pinus sylvestris L. stands at the south-western limit of its distribution area (Central Spain), using five long-term thinning trials. Data were analysed collectively considering several factors (trial, block, plot and period) as random effects. Total volume and volume increment decreased with thinning intensity, this loss being more significant in the case of moderate and heavy thinning. No difference was found among treatments for total basal area or the increment in basal area. The results revealed an optimum basal area (Assmann’s definition) between 85 and 100% of the basal area in unthinned plots. Volume growth loss associated with heavy thinnings (reduction of 18% in volume increment) was smaller than that reported in Central and Northern European regions (greater than 25%). Height increment was not influenced by thinning, whereas dominant and quadratic mean diameter increments increased with the thinning intensity. The response of diameter growth to thinning was greater at younger ages (less than 50 y) and in medium-sized trees.     

Long-term growth analyses of Japanese cedar trees in a plantation: neighborhood competition and persistence of initial growth deviations

The individual growth of tree diameter at breast height (dbh) is analyzed in an even-aged plantation of Cryptomeria japonica from stand age of 45 to 94 years, to examine how the growth of individual trees has been affected by the changes in spacing resulting from thinning operations. At any age, a significant proportion (0.37–0.46) of the variation in dbh growth during a 5–11-year period was explained by dbh at the beginning of the period, probably due to greater leaf mass of larger trees. Next, either one-sided or two-sided competition was added to the model, by calculating the basal area (BA) of neighboring trees around each tree within a given radius or BA for trees having larger dbh than the focal tree within the radius. After preliminary analyses, a radius of 8 m was selected as the critical range for tree competition. Although both types of competition explained a significant proportion (0.09–0.43) of growth variation, one-sided competition was not significant at ages greater than 54 years. Based on the model at 45 years of age, the initial deviation of growth rate for each tree from the predicted rate was calculated and added to the models as a third variable. This raised the coefficient of determination up to 0.50–0.74. These findings have practical significance for forest plantation management, particularly for controlling the growth of standing trees via thinning, to produce high-quality timber in the future.     

海南岛热带天然次生林生长动态研究

本文对两类处于不同演替阶段的天然次生林,从直径生长、胸高断面积生长、材积生长、林木死亡率等方面进行了对比分析。研究结果表明:随着演替的进程,天然次生林直径生长、胸高断面生长和材积生长呈现下降趋势,林木死亡率也呈现明显的下降趋势,其主要原因是,在演替的早期阶段,速生喜光先锋种在林分中占据较高比例,进而林分表现出较高的死亡率和较高的生长力,但是随着演替的进行,喜光先锋速生树种逐步被耐荫的顶级或亚顶级树种所取代,进而表现出低生长和低的死亡率。     

Prediction of annual tree growth and survival for thinned and unthinned even-aged maritime pine stands in Portugal from data with different time measurement intervals

An annual individual tree survival and growth model was developed for pure even-aged stands of maritime pine in Portugal, using a large data set containing irregularly time-spaced measurements and considering thinning effects. The model is distance-independent and is based on a function for diameter growth, a function for height growth and a survival function. Two approaches are compared for modeling annual tree growth. The first approach directly estimates a future diameter or height using well-known growth functions formulated in difference form. The second approach estimates diameter or height using a function in differential form estimating the increment over a year period. In both approaches, the function parameters were related to tree and stand variables reflecting the competition status of the tree as well as of a thinning response factor. Variable growth and survival rates were assumed in the modeling approaches. An iterative method was used to continuously update tree and stand attributes using a cut-off to convert the survival probability for a living or a dead tree. The individual tree diameter growth model and the survival probability model were fitted simultaneously using seemingly unrelated regression (SUR). Parameters of the height function were obtained separately as the number of observations for height was much lower than the number of observations for diameter, which may affect the statistical inference and the estimation of contemporaneous cross-equation error correlation inherent to the system of equations. PRESS residuals were used to evaluate the predictive performance of the diameter and the height growth functions. Additional statistics based in the log likelihood function and also in the survival probability were computed to evaluate the survival function. The second modeling approach, which integrates components of growth expansion and decline, performed slightly better than the first approach. A variable accounting for the thinning response that was tested proved to be significant for predicting diameter growth, even if the model already included competition-related explanatory variables, namely the basal area of trees larger than the subject tree. However, this thinning response factor was not significant for predicting height growth.     

Distance-independent tree basal area growth models for Norway spruce,Douglas-fir and Japanese larch in Southern Belgium

This paper presents new harmonized distance-independent individual tree basal area growth models for Norway spruce, Douglas-fir and Japanese larch in pure even-aged stands in Southern Belgium. The selected model was originally developed for Norway spruce and Douglas-fir in neighboring France. New formulations are proposed for some of the model components in order to lower the number of fitted parameters and facilitate the fitting procedure. The resulting models integrate the most recent corresponding top-height growth models and use four simple and usually collected explanatory variables: stand age, top-height, total basal area and tree girth at breast height. The modified formulations maintain similar fitting performances and make it easier to interpret the influence of the explanatory variables on tree growth. Parameters estimates were fitted on thousands of growth measurements gathered from several monitoring plots, forest management inventories and silvicultural field experiments that represent the wide range of site conditions and of forest management scenarios applied to coniferous stands in Southern Belgium. Cross-validation of the models revealed no bias and highlighted their consistent behavior over the entire range of girth at breast height, age, top-height, site index and density represented in our dataset. Combining utility and robust performances, these models represent useful forest management tools, purposely ideal for forest simulation software development. Moreover, the flexibility and generic capabilities of the model formulation should make it easily adjustable for other species in even-aged stands.     

黑松引种试验研究

对引种的黑松进行了育苗和多点造林试验,从生长和抗逆性上进行了观测.苗期试验表明,黑松苗期在小陇山林区适应性强,苗期保存率高于油松,苗期生长表现与油松差异不显著,2年生苗木平均地径0.61 cm ,平均苗高16.30 cm.多点造林试验表明,黑松适应小陇山林区的气候、立地条件,抗鼠害能力比油松强,造林成活率和保存率比油松高,幼林生长表现与油松差异不显著.8年生黑松林分平均胸径3.20 cm,平均高2.98 m.引种获得成功,丰富了小陇山林区营造生态公益林的种质资源.     

Predicting Potential Density and Basal Area Development in the Social Forestry Plantations of Acacia nilotica in Gujarat State of India

ABSTRACT

Growth modelling is an important and effective tool for evaluating the effects of a particular management action on the future development of a forest ecosystem. However, such necessary growth models are not available for many indigenous tree species in India. Acacia nilotica is an important multipurpose tree species found in India and growth models are required for proper management of the species in the region. This paper presents equations for estimating potential stand density and predicting basal area in pure even-aged stands of A. nilotica in Gujarat State of India. Although no thinning was suggested, decrease in the number of trees in the stands was observed because of mortality due to overcrowding and some biotic factors. Relationships between quadratic mean diameter and stems per hectare were developed, which was used to establish the limiting density line. Eight different stand level models, belonging to the path invariant algebraic difference form of a non-linear growth function, were compared for projecting basal area. They can be used to predict future basal area as a function of stand variables like dominant height and stem number per hectare and are crucial for evaluating different silvicultural treatment options. The performance of the models was evaluated using different statistical criteria to recommend the suitable model for projecting the basal area in A. nilotica stands.     

Quantitative validation and comparison of a range of forest growth model types

Predictions from a range of model types (simplified process-based, a statistical state space, statistical difference, and a hybrid model) were compared to 969 measurements of forest growth across an environmental gradient. The models compared were 3-PG, CANTY, CanSPBL(1.2), and CanSPBL(water). The study made an objective comparison and validation of model types, with the main criterion for comparison being each model's ability to match actual historical measurements of forest growth in an independent data set. A number of stand level forest growth variables were compared including basal area, mean top height, and stocking over 14,058 ha of plantation-grown Pinus radiata in south-eastern New Zealand. Stand variable predictions at 195 permanent plot locations covering a range of elevations from 0 to 660 m were highly correlated with field estimates derived from plot data. The hybrid model CanSPBL(water) on average was the most accurate model in the study where predictions of stocking, basal area, and mean top height were 96%, 96%, and 96% efficient. The statistical-difference equation model CanSPBL(1.2) was equally efficient but on average 3% less accurate and slightly more biased in predictions suggesting that the hybrid model explained differences in growth due to differences water availability and soil type. The process-based model 3-PG predicted stocking and basal area 89% and 88% efficiently. Finally, the statistical state-space model CANTY predicted stocking, basal area, and mean top height 96%, 87%, and 87% efficiently. Results quantify the amount of precision that can be expected from the three model types, and suggest that each approach has strengths and weaknesses.     

不同立地及间伐强度对杉木人工林生长的影响

为探明不同立地及间伐强度对杉木人工林生长影响,在浙江庆元林场3个林区分别开展了不同间伐强度(10%～15%、16%～30%、31%～40%)对杉木（隆宫林区杉木19年生,卢峰和白领头两个林区20年生）人工林生长影响的研究。结果表明：间伐3 a后,隆宫和卢峰林区胸径、单株材积都随间伐强度加大而增加,3个林区16%～30%和31%～40%间伐强度胸径平均连年生长量、单株材积平均连年生长量都要显著高于10%～15%间伐强度,而16%～30%和31%～40%间伐强度之间差异不显著,相同林区不同间伐强度的树高平均连年生长量差异都不显著,3个林区31%～40%间伐强度的平均林分蓄积都较小,隆宫和白领头林区不同间伐强度的林分蓄积平均连年生长量之间都存在显著差异,卢峰林区16%～30%和31%～40%间伐强度林分蓄积平均连年生长量之间差异不显著,但都显著高于10%～15%间伐强度。本研究通过综合林分因子分析得出隆宫和白领头林区的最佳间伐强度16%～30%,而卢峰林区的最佳间伐强度为31%～40%。