Influence of tree crown characteristics on the local PM10 distribution inside an urban street canyon in Antwerp (Belgium): A model and experimental approach

Apart from influencing the amount of leaf-deposited particles, tree crown morphology will influence the local distribution of atmospheric particles. Nevertheless, tree crowns are often represented very rudimentary in three-dimensional air quality models. Therefore, the influence of tree crown representation on the local ambient PM₁₀ concentration and resulting leaf-deposited PM₁₀ mass was evaluated, using the three-dimensional computational fluid dynamics (CFD) model ENVI-met^® and ground-based LiDAR imaging. The modelled leaf-deposited PM₁₀ mass was compared to gravimetric results within three different particle size fractions (0.2–3, 3–10 and >10 μm), obtained at 20 locations within the tree crown. Modelling of the LiDAR-derived tree crown resulted in altered atmospheric PM₁₀ concentrations in the vicinity of the tree crown. Although this model study was limited to a single tree and model configuration, our results demonstrate that improving tree crown characteristics (shape, dimensions and LAD) affects the resulting local PM₁₀ distribution in ENVI-met. An accurate tree crown representation seems, therefore, of great importance when aiming at modelling the local PM distribution.     

桃树树体改造及长枝修剪关键技术

着重介绍桃树树体结构改造、枝组调整和处理以及长枝修剪的优点、要领,总结出桃树树体改造和长枝修剪应注意的问题等。     

Application of Grey System Theory to tree growth prediction

IntroductionDahurian larch plantations were planted affer the1950's in Heilongjiang Province. Some of them areless than 40 years old. There lack permanent plots oflong-term. Sometimes, statistical models for predicting tree growth are not always desirable. The GreySystem is a new branch of mathematics founded byProf. Deng Julong in 1982 (Deng 1985). In contrast tostatistic models, which need a lot of measured data,the Grey System only need a f6w data for setting upmodels. In recent years…     

基于树形视图多层动态列表项的农副产品销售系统

通过分析农副产品销售系统中树形视图各列表项的构成层次,提出了一种调用insertitemlast（）函数实现列表项动态构建的新方法,并给出了基于此方法的农副产品销售系统实例。     

Urban tree growth and their dependency on infiltration rates in structural soil and structural cells

Expanding tree canopies can be difficult to achieve in built environments because urban land is costly and urban soil inhospitable to vegetation so engineered planting systems offer a potentially valuable tool for achieving sustainable urban forests. Tree water uptake, performance and root distribution were assessed in systems of structural soil and structural cell. Structural soil relies on stone and soil, it is highly porous and designed to support tree root growth and possess pavement strength. The structural cell is made up of rigid structural units with 90% void space which is to be filled with soil. To evaluate tree performance under the conditions of fill and drain regimes in structural soil and structural cell, these two systems were subjected to three simulated infiltration rates. This study was conducted in April 2015 to April 2016 in the tropical equatorial environment of South East Asia. Infiltration rate affected both biomass accumulation and rooting depth. Species and substrate effect was significant for biomass and rooting characteristics but less prominent for transpiration. Biomass was greater for trees in structural cells, and Pouteria obovata was particularly sensitive to prolonged inundation. Rooting depth was always higher in the rapid infiltration indicating the negative effects inundation had on this parameter. Root system in the structural cell was deeper while those in the structural soil were wider. Samanea saman had better adapted to the drain and fill regimes, and this was despite Pouteria obovata being a coastal species and was expected to be flood tolerant. Species and substrate effect was weak (R² ranging from 0.20 to 0.28) but moderate drainage consistently led to higher transpiration. We conclude that structural soil and structural cell are potential solutions and provide a tool to overcome suboptimal urban growing conditions. The application of these solutions will allow for seamless integration of greenery with urban infrastructure.     

黑果腺肋花楸不同树形与主枝数对产量的影响

该文通过抽样调查和统计分析,充分论证了黑果腺肋花楸采用丛状树形明显优于疏散分层形和扇形,当主枝数达19～22条时单位面积产量最高。     

日本设施果树的树形结构与光能利用研究进展

通过留学期间对日本设施果树树形结构与光能利用特性的调查分析与研究 ,结果表明 :日本设施果树的树形结构研究始终是围绕高光效、高质量、易管理这三个中心 ,生产上重点在推广单层薄叶幕结构的平棚树形 ,X形、H形、Y形和三主肋骨形及其改良形等高效优产树形已在不同果树上广泛应用。其中Y形非常适合乔木果树的集约化矮密植栽培 ,符合优质、高产、高效农业的发展方向 ,有广泛普及价值 ,未来可能成为除葡萄外多种果树的的通用树形。此类树形结构的突出特点是 :枝叶单层水平分布 ,叶幕薄 ,离地高 ,生态环境优越 ,通风透光好 ,病虫害少。结果均匀整齐 ,下垂果多。果实形正、色佳、味甜、质量好 ,商品档次高。树冠覆盖率和有效生产区高达10 0 %。枝叶生长缓和 ,树势容易控制 ,枝梢夏季管理省工。各器官生长发育状态与节奏好 ,长停交替按次有序 ,营养分配协调合理。而且作业空间大 ,机械行走方便。建议我国因地制宜研究选用     

Microbial biomass and activity in soil and litter underPinus sylvestris, Picea abies andBetula pendula at originally similar field afforestation sites

Microbial biomass C and N, and activities related to C and N cycles, were compared in needle and leaf litter, and in the uppermost 10 cm of soil under the litter layer in Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies L.) and silver birch (Betula pendula L.) stands, planted on originally similar field afforestation sites 23–24 years ago. The ground vegetation was differentiated under different tree species, consisting of grasses and herbs under birch and pine, and mosses or no vegetation with a thick layer of needles under spruce. The C:N ratio of the soils was 13–21 and the soil pH_{CaCl 2} 3.8–5.2. Both showed little variation under different tree species. Microbial biomass C and N, C mineralization, net ammonification, reduction) did not differ significantly in soil under different tree species either. Birch leaf litter had a higher pH_{CaCl 2} (5.9) than spruce and pine needle litter (pH 5.0 and 4.8, respectively). The C:N ratio of spruce needles was 30, and was considerably higher in pine needles (69) and birch leaves (54). Birch leaves tended to have the highest microbial biomass C and C mineralization. Spruce needles appeared to have the highest microbial biomass N and net formation of mineral N, whereas formation of mineral N in pine needles and birch leaves was negligible. Microbial biomass C and N were of the same order of magnitude in the soil and litter samples but C mineralization was tenfold higher in the litter samples.     

Pinus pinaster Ait. tree mortality following wildfire in Spain

Maritime pine (Pinus pinaster Ait.) is the tree species most affected by wildfire in the Iberian Peninsula. Prediction of the probability of fire-injured tree mortality is critical for management of burned areas, evaluation of the ecological and economic impact of wildfire and prescribed fire planning and application. Pine bark beetles (Scolytidae) frequently attack burned maritime pine stands and cause extensive post-fire mortality throughout the Iberian Peninsula. In the present study, maritime pine trees were monitored for three years following 14 wildfires in four ecotypes in Spain (11 fires in Galicia (Galician ecotype - NW Spain), one fire in Portillo (Meseta-Castellana ecotype - Central Spain), one fire in Rodenal (Rodenal ecotype - Central Spain), and one fire in Genalguacil (Sierra Bermeja ecotype - SW Spain)). Data on tree attributes, crown and bole injury, ground fire severity, Ips sp. presence and tree survival were obtained by examining 3085 trees. Logistic regression models for predicting the probability of delayed maritime pine mortality were developed by use of generalized estimated equations (GEE). An ample range of response to fire damage in mortality was evident among the four ecotypes and different models were fitted for each. The most important variables for predicting tree mortality were total crown volume damaged, presence of Ips sp. attack and cambium kill rating. The results highlight the extensive presence of Ips sp. in burned maritime pine forests and its importance in tree mortality process, the ample range of response of P. pinaster, in terms of post-fire mortality, as well as the need to develop site specific mortality models for the different ecotypes of this species following fire.     

Conservation value of dispersed tree cover threatened by pasture management

Trees dispersed in pastures are a prominent feature of many Central American landscapes, particularly in cattle producing regions where farmers retain trees to serve as shade, fodder, timber and firewood. The presence of dispersed trees in pastures is often considered as important for the conservation of biodiversity by providing habitat and enhancing landscape connectivity. However, despite their critical productive and environmental roles, little is known about tree distribution within pastures or how farmers’ management decisions influence the trees themselves and their impact on farm productivity and biodiversity conservation. Here, we present a synthesis of (a) the abundance, composition, and size of dispersed trees in four important cattle producing regions of Costa Rica (Caňas and Río Frío) and Nicaragua (Rivas and Matiguás), based on inventory of 18,669 trees on 1492 ha of pasture, (b) the local knowledge, management and use of trees by cattle farmers, and (c) opportunities for ensuring sustainable management of dispersed trees in pasture-dominated landscapes. Dispersed trees were common in all four landscapes, with mean frequency ranging from 8.0 trees ha⁻¹ in Caňas to 33.4 trees ha⁻¹ in Matiguás. A total of 255 tree species were found in pastures across the four landscapes. The total number of tree species per landscape varied from 72 in Rivas to 101 in Caňas and Rio Frio, with mean species richness per farm ranging from 22.9 in Rio Frio to 45.9 in Matiguás. In all four landscapes, a handful of tree species dominated the pastures, with the ten most abundant species in each landscape accounting for >70% of all trees recorded. Most of these common tree species provide fruits or foliage eaten by cattle, or are important timber or firewood species, and are deliberately retained by farmers for these uses. In all four landscapes, farmers had a detailed knowledge of tree attributes affecting pasture and animal productivity, and influenced tree cover through pasture management activities and occasional tree cutting. Current farm management practices are gradually decreasing the diversity of trees in pastures, and in some cases also tree density, reducing their contribution to farm productivity and biodiversity conservation. To reverse this trend, incentives are required to encourage cattle farmers to retain and enhance tree cover in pastures, through the adoption of pasture management practices that favor the regeneration and persistence of a diverse range of tree species.