Crown structure and leaf area index development in thinned and unthinned Eucalyptus nitens plantations

The crown structure of Eucalyptus nitens (Deane & Maiden) Maiden 6 years after thinning, and the development of stand leaf area index both immediately and 6 years after thinning, were investigated. Thinning did not alter branch angle, branching density or the relationship between branch size and branch leaf area. However, larger branches were found in the lower crown of thinned trees and the increase in leaf area as a result of thinning occurred on the northern aspect of the crown. The vertical distribution of leaf area in unthinned trees was skewed toward the top of the crown and correlated with live crown ratio. The vertical distribution of leaf area in thinned trees tended to be less skewed and was unrelated to tree size or dominance. Leaf area index, as estimated from light interception measurements, increased at a constant rate soon after thinning regardless of residual stocking. In the longer term, residual stocking had a strong influence on leaf area increase per tree and was correlated with changes in crown length.     

Influence of site in the wood quality of Eucalyptus in plantations in Brazil

Genetic materials interact with the environment in specific ways, therefore their responses in wood need to be better understood. The present study sought to evaluate the influence of different climatic conditions in Minas Gerais, Brazil on Eucalyptus grandis × Eucalyptus urophylla wood. Two six-year-old clones were cultivated in Belo Oriente, Ferros, Santa Bárbara, Itabira and Peçanha. Five trees from each clone were sampled from the base to top direction. Wood density, heartwood/sapwood ratio, vessels, fibres, and extractive and lignin contents were determined, as well as their correlation with environmental variables. Vessel diameters, heartwood/sapwood ratio, and extractive and lignin contents all increased due to higher water availability in Santa Bárbara and Itabira. In both genetic materials, the variables linked to growth and wood quality were related to environmental factors.     

Testing the suitability of the Nepal-Somers stand table projection method for Eucalyptus grandis plantations in South Africa

This study presents an application of a stand table projection method for varying stand densities of Eucalyptus grandis in South Africa. The projections of diameter at breast height (dbh) class frequencies are compatible with future values of basal area and stem number per hectare. The application requires an individual tree dbh growth function, a current stand table, and estimates of future basal area, and tree survival. The resulting stand table is adjusted by an algorithm that guarantees that the future stand table is compatible either with observed or predicted values of basal area and stem number per hectare. The results, based on a relatively small experimental dataset, are satisfactory. However, further work based on a larger dataset is required to evaluate the general suitability of the method for stand table projection of Eucalyptus grandis in South Africa, especially regarding variable site conditions. The particular contribution of this study is the fact that we were able to demonstrate the suitability of the Nepal and Somers stand table projection method for a unique dataset from a very densitysensitive Correlated Curve Trend spacing trial. We also made an attempt to present a comprehensive example of a projection to facilitate practical application of this method in the KwaZulu-Natal coastal plain of South Africa.     

Light- and nutrient-related relationships in mixed plantations of Eucalyptus and a high diversity of native tree species

New Forests - Mixed plantations composed of Eucalyptus intercropped with a high diversity of native tree species are a promising option for combining biodiversity recovery with wood production...     

The effects of stand structure on specific needle area in closed-canopy Chinese pine plantations

The specific leaf area (SLA) is an important variable reflecting the carbon gain strategy of tree growth, but the relationships between SLA and other environmental factors have not been studied extensively at the stand level. The aim of this study was to define the relationships between stand structure and SLA in order to improve the predictive value of SLA for forest management models. Various parameters of stand structure and specific needle area (SNA) were measured in 14 different even-aged and closed-canopy stands of Chinese pine (Pinus tabulaeformis Carr.). Correlation and regression analysis revealed several significant relationships between stand structure and SNA. Stand density exerted a significant effect on mean-canopy SNA (SNA_mean). Stand density was also strongly correlated to mean-layer SNA (SNA_L), especially at lower canopy layers. SNA_L increased at lower canopy layers within each stand, and the increase was greater in higher density stands. Within the range of stand densities examined in this study, the SNA_mean initially increased sharply with increasing stand density, but the rate of rise declined as the density increased. Finally, it reached stability when the stand density was above about 3,000 trees ha^?1.     

Biomass harvesting in Eucalyptus plantations in Western Australia

Australia is at an early stage of exploring the use of forest biomass to generate energy. This study evaluated the biomass yield and the productivity rates of equipment for harvesting biomass in a poor-quality eucalypt plantation. The operation consisted of a tracked feller-buncher, grapple skidder and mobile chipper. Time study methods were used to measure the harvesting operation. A multiple regression model was constructed to predict skidding productivity. Biomass production was 63.9 t ha^?1 based on the recorded load weight of eight trucks. Delays were documented and analysed. The average delay for all equipment was about 30% of working time. The study results will help guide biomass harvesting managers to estimate productivity and cost of similar operation sites.     

Diseases on Eucalyptus species in Zimbabwean plantations and woodlots

Zimbabwe embarked on planting Eucalyptus species in the early 1900s. Based on a robust breeding programme, it has become a major source of seed for other countries in and outside Africa. Tree health surveys conducted on Eucalyptus in some east and southern African countries over the past two decades have revealed several important fungal diseases that were previously not known in the region, but little is known regarding these problems in Zimbabwe. The aim of this study was to identify important Eucalyptus diseases across Zimbabwe's agroclimatic regions. Morphological characteristics and DNA sequence data were used to identify pathogens collected to species level. Widespread stem canker diseases, caused by species belonging to the Botryosphaeriaceae and Teratosphaeriaceae, and leaf spot diseases caused by fungi in the Capnodiales, were identified. Armillaria root and stem rot was restricted to a single site in the Eastern Highlands. Fungi that could cause canker or blue stain of timber were isolated from recently harvested stumps and included species of Ceratocystis and Ophiostoma. This study is the first to identify Eucalyptus pathogens to species level in Zimbabwe and we report for the first time the presence of the stem canker pathogen T. gauchensis in southern Africa. The results will provide a foundation for the formulation of future disease management strategies in the country.     

塞罕坝华北落叶松人工林立地质量评价

以华北落叶松人工林为研究对象,基于塞罕坝机械林场2012年森林资源二类调查数据,选取立地因子(坡向和土层厚度)和林分因子(树高和林龄),应用统计学方法划分立地类型,利用理查德(Richard)函数拟合立地指数,构建华北落叶松树高曲线,编制地位指数表,并对该区不同林龄(幼龄林、中龄林和近熟林)华北落叶松的6种立地类型进行立地质量评价,结果表明:阳坡中层土和阴坡厚层土立地质量为Ⅰ级,平均立地指数分别为12.15m、11.55m;阳坡厚层土和阴坡中层土立地质量为Ⅱ级,平均立地指数分别为11.39m、11.16m;阴坡薄层土和阳坡薄层土立地质量分别为Ⅲ级和Ⅳ级,平均立地指数分别为10.85m、9.87m。     

Physiological response to pruning severity in Eucalyptus regnans plantations

The photosynthetic response to pruning was measured in two Eucalyptus regnans stands, aged 2 and 3 years, located in areas of high productivity on the coast of the province of Arauco, Chile. Variables such as rates of CO₂ assimilation and stomatal conductance were measured in three ages of foliage on trees with different pruning severity treatments, which corresponded to the removal of 0 % (control), 30, 50 and 70 % of live crown length. The 2-year-old stand measurements were performed at the time of pruning and 6, 10, 14 and 18 weeks later, and the 3-year stand, 5, 9, 18 and 28 weeks after pruning. In both trials, significant differences were found between the foliage ages for all instances of measurement showing the mature foliage the highest values up to 30 % higher than old foliage. There were also significant differences between pruning severity treatments in both trials in which, in general, the highest values of CO₂ assimilation were observed among the highest pruning severity treatments with values up to 40 % higher than the unpruned trees.     

滇中桉树人工林群落比较分析

本文就滇中桉树人工林纯林、桉树混交林及其它种类的人工林调查材料,对不同林种的群落进行比较,从比较结果中分析桉树人工林生物多样性问题。通过比较分析发现：1、桉树本身的排它现象并不显著;2、桉树林下和松林的林下植物的丰富度相差不多;3、多种按树混交较单一桉树纯林的林下植物丰富。     

我国桉树人工林施肥研究进展

科学施肥是实现桉树人工林速生丰产的一个重要措施。本文从桉树人工林施肥研究的历史、桉树种植区的土壤肥力、施肥效应、营养诊断和平衡施肥等方面综述了桉树人工林施肥的研究进展,指出了目前研究中存在的问题和今后的研究方向,为我国桉树速生丰产林的可持续经营提供科学依据。     

Mycosphaerella species occurring on Eucalyptus globulus and Eucalyptus nitens plantations of Tasmania,Australia

The genus Mycosphaerella Johanson contains many pathogens capable of causing a severe impact on the growth of susceptible eucalypt species. The lack of knowledge about which species are present in Tasmania and their potential risk to the plantation industry prompted this study into the Mycosphaerella species occurring on Eucalyptus globulus and Eucalyptus nitens plantations in Tasmania. A total of 36 plantation and five road verge sites of E. globulus and E. nitens were sampled. Five Mycosphaerella species and three species from associated anamorph genera were isolated and identified in Tasmania; Mycosphaerella nubilosa, Mycosphaerella cryptica, Mycosphaerella tasmaniensis, Mycosphaerella grandis, Mycosphaerella vespa, Coniothyrium ovatum, Sonderhenia eucalypticola and Sonderhenia eucalyptorum. The most frequently isolated species with the highest incidence and severity of infection were M. cryptica and M. nubilosa. These two species appear to have the greatest potential to damage juvenile eucalypt plantations in Tasmania. A link between Mycosphaerella vespa and Coniothyrium ovatum is described for the first time.     

广西不同林龄桉树人工林叶—凋落物—土壤C、N、P生态化学计量特征

C、N、P元素的养分循环过程是影响森林生态系统结构与功能的关键因素。以广西不同林龄桉树人工林为研究对象,分析桉树幼龄林(1a)、中龄林(2a)、近熟林(3a)、成熟林(5a)、过熟林(8a)叶—凋落物—土壤的C、N、P化学计量特征及其内在联系,探讨林龄对桉树人工林生态化学计量的影响,为桉树人工林可持续经营提供参考。结果表明:1)桉树人工林叶、土壤呈现高C低N、P的元素格局,凋落物呈现高C、P低N的元素格局;叶的C、N、P含量从幼龄林到近熟林呈先增后减趋势,反映桉树人工林早期对养分需求旺盛,随年龄增大需求减小。2)不同林龄叶C、N、P差异显著(P<0.05),凋落物与土壤的N、P、C∶N、C∶P、N∶P均差异显著(P<0.05),凋落物C∶P与叶N∶P、C∶P显著正相关(P<0.05),凋落物N∶P与叶的C∶P、N∶P之间呈极显著正相关(P<0.01),说明凋落物养分源自叶,土壤与叶的C、N、P均不相关。3)与叶相比,凋落物中N、P含量偏低,C∶N、C∶P偏高;土壤C∶P、N∶P偏低,说明土壤P素分解较快,可适时施以磷肥来弥补土壤速效磷的不足;土壤C∶N偏高表明土壤有机质具有较慢的矿化作用。中龄林、近熟林和成熟林叶N∶P<14,生长过程受N限制;中龄林、近熟林和成熟林凋落物分解的主要限制性元素是N,而幼龄林凋落物分解的主要限制性元素是P。     

Corresponding patterns of site quality,decline and tree growth in a sessile oak stand

This study focuses on two rarely studied aspects of oak decline: relations with site characteristics and effects on tree growth. The study was carried out in a 5.5 ha stand in Hungary which is strongly affected by oak decline. The nearly pure sessile oak (Quercus petraea) stand of mostly coppice origin was 90 years old at the beginning of the study. Within-stand site heterogeneity was described by the herbaceous vegetation. Four ecological site types were distinguished by the species composition of herbs, and characterized by the ecological indicator values of the species. Tree growth between 1987 and 1993 was measured, and tree vigour was estimated from visual characteristics five times between 1987 and 1993. Potential volume increment of declining trees was estimated with the growth rates of healthy trees of the same size. Volume increment loss caused by oak decline was also assessed. Significant positive relationships were found between tree vigour and tree size and between tree vigour and tree growth. The growth of seriously declining trees dropped to almost one-half of that of healthy ones. Growth reduction of living trees at the stand level amounted to 5.4%, whereas growth reduction of all trees, including those that died during the observation period, amounted to 19.9% of the potential growth. Tree size and growth were greater on better sites. A strong relationship was also found between tree vigour and site type, but sessile oak was more susceptible to decline at better sites.     

辽东地区落叶松人工林连作对立地质量的影响

采用解析木导向曲线法编制了辽东地区日本落叶松地位指数表。在此基础上，对落叶松地拉指数与立地因子及落叶松栽植代数的关系进行了分析，认为不同栽植代数对落叶松人工森地位指数影响差异显，落叶松连作造成立地质量下降。     

Biometric relationships for non-destructive above ground biomass estimations in young plantations of Acacia salicina Lindl. and Eucalyptus occidentalis Endl.

Above ground oven dried biomass (BM) of individual trees in young stands of Acacia salicina Lindl. and Eucalyptus occidentalis Endl. were correlated linearly and logarithmically to the square of the basal diameter at 0.2 m (DB) and to the latter multiplied by the height of the tree. Number of main stems at basal height per tree were included as well. DB measurements in young Eucalypt stands provided better BM estimates than the commonly used diameter at breast height (1.3 m) (DBH).The following biometric relationships, after cross-validation against an independent data set, showed the best fit: BM=0.1282* (DB²) and BM=0.1700* (DB²) for A. salicina and E. occidentalis, respectively, with (DB²) ranging from 0–400 cm² and BM in kg tree^–1. For acceptable relative errors in biomass estimations (DB²) should be larger than 100 cm².Foliage to wood ratios at (DB²)<100 cm² for both tree species generally exceeded 1, but rapidly leveled off at 0.81±0.28 and 0.92±0.19 for the Acacia and Eucalypt spp., respectively, at higher (DB²) values.     

Tree,stand and site characteristics affecting the occurrence of lammas growth and multiple tops in field-grown Norway spruce

New Forests - In the Nordic-Baltic region, there has been a growing concern about an increasing occurrence of multiple tops in young stands of Norway spruce. There is however a lack of...     

Water use by fast-growing Eucalyptus urophylla plantations in southern China

Tree growth, water use, climate and soil water conditions were monitored over 12 months in two 3-4-year-old Eucalyptus urophylla S.T. Blake plantations on the Leizhou Peninsula of southern China. The Hetou plantation was established on a sandy soil of sedimentary origin with low water storage capacity, and the Jijia plantation was established on a clay soil formed on basalt. Sapwood area was approximately 50% higher at Jijia than at Hetou because of differences in plant spacing (1994 versus 1356 stems ha(-1)). Annual water use, assessed by heat pulse measurements, was 542 mm at Hetou and 559 mm at Jijia, with mean sap flux densities of 2772 and 1839 l m(-2) day(-1), respectively. Limitations to water use, imposed by climatic and soil factors, were quantified by analysis of daily canopy conductance in relation to daytime vapor pressure deficit (VPD) and soil water content. Similar annual water use at the two sites was a result of higher VPD and soil water availability at Hetou compensating for the greater sapwood area at Jijia. Potential annual water use in the absence of soil water limitation was estimated at 916 mm at Jijia and 815 mm at Hetou. Higher water availability during the dry season and early wet season at Hetou than at Jijia was the result of deep root systems. The results imply that water use by plantations on soils with high water availability and in areas of high VPD may be reduced by establishment at wider spacing. The environmental cost of water use by plantations must be weighed against their economic and environmental values to determine an appropriate mix of forestry, agriculture and other land uses in regions where water resources are limited.