Unhealthy Trees Research Articles

A macroscopic soil-water transport model to simulate root water uptake in the presence of water and disease stress

Macroscopic modeling approaches based on the solution of the Richards equation with root water uptake (RWU) as a sink term can help in understanding soil-water-plant interactions within the rhizosphere. However, these models currently cannot capture the differences in RWU attributed to variations in plant health. Errors in simulating RWU from unhealthy plants are significant when disease-causing fungus inhibits water uptake rather than other usually considered plant stresses. We developed RWU reduction functions to simulate plant transpiration under combined water and disease stress conditions using linear and non-linear response models. The developed functions were implemented in the numerical model HYDRUS (2D/3D) to simulate water uptake from a root system in a radially symmetrical flow domain. Field experiments were conducted in the Vidarbha region of central India for one crop cycle on four citrus trees with varying disease intensities (healthy to severely diseased). The proposed model was rigorously tested by comparing its results with measured soil water contents and plant transpiration fluxes under various water and disease limiting conditions. Error in simulating RWU fluxes from unhealthy trees by ignoring the disease stress factor was found to be significant (15% for slightly diseased to 26% for the severely diseased tree). Parameters of the spatial root distribution and the disease stress response functions were optimized for each scenario using a genetic algorithm approach. Our results indicate that calibration targets to validate uptake reduction functions should be chosen cautiously based on the dominant stress experienced by the plant root system.

Assessing the Use of Sentinel-2 Time Series Data for Monitoring Cork Oak Decline in Portugal

In Portugal, cork oak (Quercus suber L.) stands cover 737 Mha, being the most predominant species of the montado agroforestry system, contributing to the economic, social and environmental development of the country. Cork oak decline is a known problem since the late years of the 19th century that has recently worsened. The causes of oak decline seem to be a result of slow and cumulative processes, although the role of each environmental factor is not yet established. The availability of Sentinel-2 high spatial and temporal resolution dense time series enables monitoring of gradual processes. These processes can be monitored using spectral vegetation indices (VI) as their temporal dynamics are expected to be related with green biomass and photosynthetic efficiency. The Normalized Difference Vegetation Index (NDVI) is sensitive to structural canopy changes, however it tends to saturate at moderate-to-dense canopies. Modified VI have been proposed to incorporate the reflectance in the red-edge spectral region, which is highly sensitive to chlorophyll content while largely unaffected by structural properties. In this research, in situ data on the location and vitality status of cork oak trees are used to assess the correlation between chlorophyll indices (CI) and NDVI time series trends and cork oak vitality at the tree level. Preliminary results seem to be promising since differences between healthy and unhealthy (diseased/dead) trees were observed.

Analysis of Changes in Oil Palm Canopy Architecture From Basal Stem Rot Using Terrestrial Laser Scanner.

Basal stem rot (BSR), caused by the Ganoderma fungus, is an infectious disease that affects oil palm (Elaeis guineensis) plantations. BSR leads to a significant economic loss and reductions in yields of up to Malaysian Ringgit (RM) 1.5 billion (US$400 million) yearly. By 2020, the disease may affect ∼1.7 million tonnes of fresh fruit bunches. The plants appear symptomless in the early stages of infection, although most plants die after they are infected. Thus, early, accurate, and nondestructive disease detection is crucial to control the impact of the disease on yields. Terrestrial laser scanning (TLS) is an active remote-sensing, noncontact, cost-effective, precise, and user-friendly method. Through high-resolution scanning of a tree's dimension and morphology, TLS offers an accurate indicator for health and development. This study proposes an efficient image processing technique using point clouds obtained from TLS ground input data. A total of 40 samples (10 samples for each severity level) of oil palm trees were collected from 9-year-old trees using a ground-based laser scanner. Each tree was scanned four times at a distance of 1.5 m. The recorded laser scans were synched and merged to create a cluster of point clouds. An overhead two-dimensional image of the oil palm tree canopy was used to analyze three canopy architectures in terms of the number of pixels inside the crown (crown pixel), the degree of angle between fronds (frond angle), and the number of fronds (frond number). The results show that the crown pixel, frond angle, and frond number are significantly related and that the BSR severity levels are highly correlated (R2 = 0.76, P < 0.0001; R2 = 0.96, P < 0.0001; and R2 = 0.97, P < 0.0001, respectively). Analysis of variance followed post hoc tests by Student-Newman-Keuls (Newman-Keuls) and Dunnett for frond number presented the best results and showed that all levels were significantly different at a 5% significance level. Therefore, the earliest stage that a Ganoderma infection could be detected was mildly infected (T1). For frond angle, all post hoc tests showed consistent results, and all levels were significantly separated except for T0 and T1. By using the crown pixel parameter, healthy trees (T0) were separated from unhealthy trees (moderate infection [T2] and severe infection [T3]), although there was still some overlap with T1. Thus, Ganoderma infection could be detected as early as the T2 level by using the crown pixel and the frond angle parameters. It is hard to differentiate between T0 and T1, because during mild infection, the symptoms are highly similar. Meanwhile, T2 and T3 were placed in the same group, because they showed the same trend. This study demonstrates that the TLS is useful for detecting low-level infection as early as T1 (mild severity). TLS proved beneficial in managing oil palm plantation disease.

Source and Sink Relations Mediate Depletion of Intrinsic Cycad Seed Carbohydrates by Aulacaspis yasumatsui Infestation

Ubiquitous Aulacaspsis yasumatsui Takagi infestations of Guam’s Cycas micronesica K.D. Hill trees cause direct herbivory of most exposed organ surfaces, including developing naked ovules and seeds. The nonstructural carbohydrates of infested vs. noninfested seeds were quantified to understand more fully the influences on seed quality for propagation purposes. Two studies compared seeds from healthy trees with those of unhealthy trees suffering from whole-tree A. yasumatsui infestations. The sugars fructose, glucose, maltose, and sucrose were in greater concentrations and herbivory reduced these free sugars by a greater percentage in sarcotesta tissue than in sclerotesta and gametophyte tissues. Starch concentration was greatest in gametophyte tissue, but herbivory reduced starch by a greater percentage in sarcotesta tissue. A third study was used to manipulate seeds of unhealthy infested trees such that some seeds were uninfested and some seeds were infested and revealed the nonstructural carbohydrates of the uninfested seeds were greater than those of the infested seeds in patterns that were similar to those when the entire tree was protected from herbivory. The combined results indicated that both source and sink relations were involved in the reductions of seed carbohydrates by A. yasumatsui herbivory. The reduction in seed resource pool by the herbivore feeding may be one of the mechanisms that results in reduced germination percentage and increased seedling mortality.

Detection of necrotic foliage in a young Eucalyptus pellita plantation using unmanned aerial vehicle RGB photography – a demonstration of concept

ABSTRACT Recent advances and commercialisation of unmanned aerial vehicle/red blue green (RGB) camera systems and digital photogrammetric techniques now provide a cheap and flexible alternative to higher-cost airborne platforms for routine monitoring of canopy health in timber plantations. Structure-from-Motion photogrammetry produces very dense three-dimensional (3D) point clouds which can be used to derive metrics for inventory estimation. Unmanned aerial vehicle RGB photography also captures data that can relate to tree health. In contrast to the more common use of orthorectified RGB photography to extract this spectral information, we used the software package Agisoft Photoscan to assign a simple Vegetation Index value directly to each point in the 3D point cloud. Using data acquired by a DJI Phantom 4 Pro, we present a simple processing and photogrammetric workflow solution for detecting dead and dying trees in a young Eucalyptus pellita plantation located in the provenance of Riau, Sumatra. Trees affected by the bacterial wilt Ralstonia sp. present symptoms of necrotic foliage on individual branches or the whole crown. Assigning the Visible Atmospheric Resistant Index Vegetation Index colour-coded values to individual points in the 3D point cloud significantly enhanced visualisation of necrotic foliage on individual trees in both the point cloud and the associated orthophoto compared to the RGB equivalent images. This approach could easily be operationally deployed for the rapid detection and mapping of unhealthy trees with symptoms of necrotic foliage.

北京市居住区林木健康评价

PDF HTML阅读 XML下载 导出引用 引用提醒 北京市居住区林木健康评价 DOI: 10.5846/stxb201811122447 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家科技支撑计划-环境友好型城镇景观林构建技术研究与示范（2015BAD07B06） Health Assessment of trees in residential areas of Beijing Author: Affiliation: Fund Project: the National Science-technology Support Plan Projects—Research and demonstration on the construction technology of environment-friendly urban landscape forest（2015BAD07B06） 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为了揭示北京市居住区林木健康变化特征及影响因素，提供北京市居住区林木健康经营对策。对北京市85个居住区林木进行健康特征调查，在建立林木健康评价模型评价林木健康状况的基础上，采用方差分析法和多重比较法分析不同类型居住区林木健康差异。结果表明：不同类型居住区林木健康指标差异显著（P<0.05），各指标变化规律不完全一致；不同类型居住区地表覆盖情况、光污染程度、树干倾斜度、栽植截干、树势、冠形、干形等方面普遍较差。北京市居住区林木健康指数在0.60-0.80之间，健康等级呈现右偏正态分布特点，健康林木比例为3.65%，亚健康林木（56.07%）最多，其次是中等健康林木（36.68%），不健康林木有3.50%，濒死林木仅占0.10%。居住区林木健康指数在不同区域和不同来源间差异不显著（P>0.05），在不同时期间差异显著（P<0.05），健康指数大小分别为：三-四环=四-五环 > 五-六环 > 二环内=二-三环；福利房 > 商品房 > 保障房；2009-2013年 > 2003-2008年=1998-2002年=1991-1997年 > 1956-1990年。北京市居住区林木生长处于亚健康状态，潜在影响因子如地表覆盖情况、光污染程度、树干倾斜度等指标是限制北京市居住区林木生长的重要因子。适当减小夜间照明影响、增加有机地表覆盖、避免过度的修枝截干和加强林木养护管理是当前北京市居住区林木健康生长的保障。 Abstract:In this study, we aimed to identify the variations and factors determining tree health in residential areas of Beijing, and provide recommendations to tree health managements, by investigating 85 residential areas in Beijing. Tree health was evaluated using a tree health assessment model, and on the basis of this, differences in tree health among different types of residential areas were assessed using one-way ANOVA and the Duncan test. The results were as follows:tree health indicators were significantly different in different types of residential areas (P < 0.05), and the variation ranks of each indicator were not completely consistent. Some tree health indicators in some types of residential area were generally poor, and factors determining this were surface coverage, light pollution, trunk lean, cutting off crown and planting, tree vigor, crown profile and stem form. Trees health indices in all residential areas of Beijing tested were 0.60-0.80, and tree health was characteristic of a right normal distribution. Healthy trees accounted for 3.65%, sub-healthy trees accounted for 56.07%, medium-healthy trees accounted for 36.68%, unhealthy trees accounted for 3.50%, and dying trees accounted for 0.10%. Tree health indices were not significantly different (P > 0.05) between residential areas in different districts and origins, while differences between different assessment periods were significant (P < 0.05). Ranks of trees health indices in difference types of residential area are presented:3rd-4th ring road=4th-5th ring road > 5th-6th ring road > within 2nd ring road=2nd-3rd ring road; welfare housing > commodity apartment > social security housing; 2009-2013 > 2003-2008=1998-2002=1991-1997 > 1956-1990. The majority of trees in residential areas of Beijing are in a sub-healthy state, and potential factors such as surface coverage, light pollution, and trunk lean are important factors restricting tree growth. Reducing the influence of night lighting, increasing the coverage of organic ground surfaces, avoiding excessive pruning of branches, and improving maintenance and management of trees will ensure healthy growth of trees in the residential areas of Beijing. 参考文献 相似文献 引证文献

Classifying the severity of basal stem rot disease in oil palm plantations using WorldView-3 imagery and machine learning algorithms

ABSTRACTBasal stem rot (BSR) disease caused by Ganoderma boninense is a major disease in oil palm plantations and there is no effective fungicide to control this disease. Several researchers have applied remote sensing for BSR studies, but, until now, WorldView-3 imagery has not been used to classify the severity of BSR disease symptoms. The objectives of this study were to predict disease severity with WorldView-3 imagery using supervised learning algorithms, and to describe the characteristic symptoms of BSR disease in oil palm at different disease severity levels that can be identified by WorldView-3 imagery. Field observation data were collected for 1923 oil palm trees with various levels of infection, namely healthy trees, and unhealthy trees with three levels of symptoms from mild to severe. Decision tree, random forest, and support vector machine learning algorithms were applied. The overall accuracy was low, but the accuracy was improved by about 1%–5% after outliers were removed from the data. Outliers were removed based on box plots of the distribution of reflectance value of band 4. Band 4 was selected by Jeffries-Matusita distance analysis and ‘stepclass’ algorithm. The separation of four levels of BSR disease described in this study was affected by the criteria used to describe the BSR disease symptoms in the field observation step. A redefined method and new criteria for BSR disease symptoms that can be identify using WorldView-3 imagery are described.

Estimating Changes in Leaf Area, Leaf Area Density, and Vertical Leaf Area Profile for Mango, Avocado, and Macadamia Tree Crowns Using Terrestrial Laser Scanning

Vegetation metrics, such as leaf area (LA), leaf area density (LAD), and vertical leaf area profile, are essential measures of tree-scale biophysical processes associated with photosynthetic capacity, and canopy geometry. However, there are limited published investigations of their use for horticultural tree crops. This study evaluated the ability of light detection and ranging (LiDAR) for measuring LA, LAD, and vertical leaf area profile across two mango, macadamia and avocado trees using discrete return data from a RIEGL VZ-400 Terrestrial Laser Scanning (TLS) system. These data were collected multiple times for individual trees to align with key growth stages, essential management practices, and following a severe storm. The first return of each laser pulse was extracted for each individual tree and classified as foliage or wood based on TLS point cloud geometry. LAD at a side length of 25 cm voxels, LA at the canopy level and vertical leaf area profile were calculated to analyse tree crown changes. These changes included: (1) pre-pruning vs. post-pruning for mango trees; (2) pre-pruning vs. post-pruning for macadamia trees; (3) pre-storm vs. post-storm for macadamia trees; and (4) tree leaf growth over a year for two young avocado trees. Decreases of 34.13 m2 and 8.34 m2 in LA of mango tree crowns occurred due to pruning. Pruning for the high vigour mango tree was mostly identified between 1.25 m and 3 m. Decreases of 38.03 m2 and 16.91 m2 in LA of a healthy and unhealthy macadamia tree occurred due to pruning. After flowering and spring flush of the same macadamia trees, storm effects caused a 9.65 m2 decrease in LA for the unhealthy tree, while an increase of 34.19 m2 occurred for the healthy tree. The tree height increased from 11.13 m to 11.66 m, and leaf loss was mainly observed between 1.5 m and 4.5 m for the unhealthy macadamia tree. Annual increases in LA of 82.59 m2 and 59.97 m2 were observed for two three-year-old avocado trees. Our results show that TLS is a useful tool to quantify changes in the LA, LAD, and vertical leaf area profiles of horticultural trees over time, which can be used as a general indicator of tree health, as well as assist growers with improved pruning, irrigation, and fertilisation application decisions.

Effect of Soil Layer and Plant–Soil Interaction on Soil Microbial Diversity and Function after Canopy Gap Disturbance

Gaps by thinning can have different microclimatic environments compared to surrounding areas, depending on the size of the gap. In addition, gaps can play important roles in biological dynamics, nutrient cycling, and seedling regeneration. The impacts of gap size on soil microbial communities and enzyme activities in different soil layers in Chinese pine plantations are not well understood. Here, we created gaps of 45 m2 (small, G1), 100 m2 (medium, G2), and 190 m2 (large, G3) by thinning unhealthy trees in an aged (i.e., 50 years old) monoculture Chinese pine plantation in 2010. Soil samples were collected in 2015. The total, bacterial, Gram-positive (G+), and Gram-negative (G−) phospholipid fatty acid (PLFA) profiles were highest in medium gaps in both the organic and mineral layers. These indicesdecreased sharply as gap size increased to 190 m2, and each of the detected enzyme activities demonstrated the same trend. Under all the gap size managements, abundances of microbial PLFAs and enzyme activities in the organic layers were higher than in the mineral layers. The soil layer was found to have a stronger influence on soil microbial communities than gap size. Redundancy analysis (RDA) based on the three systems with different gap sizes showed that undergrowth coverage, diversity, soil total nitrogen (TN), total organic carbon (TOC), and available phosphorus (AT) significantly affected soil microbial communities. Our findings highlighted that the effect of gap size on soil microenvironment is valuable information for assessing soil fertility. Medium gaps (i.e., 100 m2) have higher microbial PLFAs, enzyme activity, and soil nutrient availability. These medium gaps are considered favorable for soil microbial communities and fertility studied in a Chinese pine plantation managed on the Loess Plateau.

Stem Carbohydrates and Adventitious Root Formation of Cycas micronesica following Aulacaspis yasumatsui Infestation

Large stem cuttings were removed from Cycas micronesica K.D. Hill trees and used for asexual propagation to more fully understand resource factors that influence adventitious root formation success. Healthy source trees had received insecticide protection from ubiquitous Aulacaspsis yasumatsui Takagi infestations and unhealthy source trees had suffered from chronic A. yasumatsui infestations. Nonstructural carbohydrates were quantified from stem tissues at the base of each 1-m cutting, and induction of adventitious roots was attempted using field soil as the medium. Carbohydrate concentrations were increased in healthy, protected tree cuttings above those in unhealthy, infested tree cuttings. The relative increase was greatest in the hexoses, intermediate in sucrose, and least in starch. The total nonstructural carbohydrate concentration in cuttings of infested trees was 54% of that of protected trees, and the sugar/starch quotient of infested trees exceeded that of protected trees. Asexual propagation success was 30% for the unhealthy tree cuttings and 100% for the healthy tree cuttings. These manipulative experiments confirm that chronic A. yasumatsui herbivory of C. micronesica trees reduces stem carbohydrates and decreases asexual propagation success. The results indicate that the use of large cuttings from unhealthy C. micronesica trees to rescue tree populations from construction sites is not a wise conservation decision in habitats where A. yasumatsui herbivory has been uncontrolled. Protocols for future rescue operations designed to transplant C. micronesica trees from construction sites may be improved by this new knowledge.

Urban tree health assessment using airborne hyperspectral and LiDAR imagery

Urban trees provide valuable ecosystem services but are at the same time under continuous pressure due to unfavorable site conditions. In order to better protect and manage our natural capital, urban green managers require frequent and detailed information on tree health at the city wide scale. In this paper we developed a workflow to monitor tree defoliation and discoloration of broadleaved trees in Brussels, Belgium, through the combined use of airborne hyperspectral and LiDAR data. Individual trees were delineated using an object-based tree detection and segmentation algorithm primarily based on LiDAR data with an average accuracy of 91%. We constructed Partial Least Squares Regression (PLSR) models to derive tree chlorophyll content (RMSE = 2.8 μg/cm²; R² = 0.77) and Leaf Area Index (LAI; RMSE = 0.5; R² = 0.66) from the average canopy spectrum. Existing spectral indices were found to perform significantly worse (RMSE > 7 μg/cm² and >1.5 respectively), mainly due to contamination of tree spectra by neighboring background materials. In the absence of local calibration data, the applicability of PLSR to other areas, sensors and tree species might be limited. Therefore, we identified the best performing/least sensitive spectral indices and proposed a simple pixel selection procedure to reduce disturbing background effects. For LAI, laser penetration metrics derived from LiDAR data attained comparable accuracies as PLSR and were suggested instead. Detection of healthy and unhealthy trees based on remotely sensed tree properties matched reasonably well with a more traditional visual tree assessment (93% and 71% respectively). If combined with early tree stress detection methods, the proposed methodology would constitute a solid basis for future urban tree health monitoring programs.

Roadside Tree Management in Urban Area for Public Safety and Properties

Roadside planting is a row of trees along the road which provides shades for people in urban areas. Proper management practices among the local authorities will improve the quality of life and human well-being. Unhealthy trees may cause problems to the road users that result from the lack of monitoring by local governing bodies. 200 respondents from the public from Selayang Municipal Council and Shah Alam City Council have participated in this study. The data analysis showed that fallen trees were the main reason for the public to lodge complaints, followed by brittle branches, thick branches and leaning tree trunk.

山西忻州地区1900-2012年典型森林的健康历史

PDF HTML阅读 XML下载 导出引用 引用提醒 山西忻州地区1900-2012年典型森林的健康历史 DOI: 10.5846/stxb201612222650 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31330015） History of forest health from 1900 to 2012 in Xinzhou Prefecture, Shanxi Province, China Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:健康的森林对维持其区域生态系统服务起着至关重要的作用，了解树木的生长历史对评估气候变化背景下森林的健康状况具有促进作用。选择山西高原中北部忻州地区保存较好的4个森林为研究对象，利用树木年轮学方法分析其生长变化特征，获得了该地区森林健康的时间和空间特征。结果表明：该地区森林在过去1个世纪中，存在3次不健康事件（1910-1940、1970-1987和1990-2012年）且在空间上表现出明显的同步性，不同时期的不健康事件持续时间和强度不尽相同，1930s的不健康事件持续时间最长也最为显着。树木径向生长与气象观测资料的相关分析显示，该地区森林生长主要与当年5-6月份温度呈负相关，与7月份降水和5-9月PDSI指数显着正相关。生长季持续的高温或降水减少造成的极端干旱事件是不健康事件空间一致性的主要驱动力，各采样点树种以及林分组成差异是影响时间特征不一致的可能原因。研究结果提供的森林健康历史数据对评估极端气候条件对森林健康生长的影响及制定合理的森林保护措施具有积极的现实意义。 Abstract:Forest health is a serious problem worldwide. Knowledge of the intensity and causes of rapidly declining forests is important for managing various forest types under the scenario of climate change. In the present study, we report on the health conditions of four young conifer forests by applying dendrochronological techniques to measure unexpected growth decline in Xinzhou District, northern Shanxi Plateau. A total of 86 samples in the form of increment cores were obtained from the study sites. The widths of tree-rings from all the samples were measured and cross-dated, then each individual tree series was standardized to identify health conditions using spatial characteristics of temporal growth. We defined unhealthy tree growth intervals as being a decrease in the growth of the individual (tree-ring index < 0.9) for at least five years when the mean tree-ring index was less than 0.7 and at least one year of tree-ring index values reached a minimum of 0.5. We calculated the percentage of trees that were unhealthy in each year, and defined an unhealthy event for the site if greater than 30% of the trees were in decline. We found three major unexpected decline growth events in the majority of individual trees in the four forests, these being 1910-1940, 1970-1987, and 1990-2012. However, the growth declines in each forest showed deviations in intensity and duration such as declines were more vigorous in the KeLan forest during the 1930s than in the other forests. To better understand the causes of the unhealthy events, a correlation analysis was performed for the three tree ring width chronologies and the meteorological records. The correlation coefficients showed that forest growth was negatively associated with May-June temperatures. However, precipitation revealed positive correlation in July and the Palmer Drought Severity Index showed positive correlation over the growing season of May-September. To validate these results, we compared our study with historical records and local paleoclimate studies. The drought events recorded in the historical documents and other paleoclimate reconstructions reasonably matched our results. These results suggest that extreme drought events caused by persistent high temperature or reduction of precipitation in the growing season are the main driving factors for radial growth decreases in trees, which was the main reason for the spatial coherence of unhealthy events. The differentiation of local stand characteristics or tree species might play a role in the inconsistency of the time characteristics. Therefore, the present study provides useful information for forest health, which has positive and realistic significance for assessing the impact of extreme climatic conditions on the healthy growth of forests and for developing reasonable forest protection measures. 参考文献 相似文献 引证文献

Physiological mechanisms of drought-induced tree die-off in relation to carbon, hydraulic and respiratory stress in a drought-tolerant woody plant

Drought-induced tree die-off related to climate change is occurring worldwide and affects the carbon stocks and biodiversity in forest ecosystems. Hydraulic failure and carbon starvation are two commonly proposed mechanisms for drought-induced tree die-off. Here, we show that inhibited branchlet respiration and soil-to-leaf hydraulic conductance, likely caused by cell damage, occur prior to hydraulic failure (xylem embolism) and carbon starvation (exhaustion of stored carbon in sapwood) in a drought-tolerant woody species, Rhaphiolepis wrightiana Maxim. The ratio of the total leaf area to the twig sap area was used as a health indicator after drought damage. Six adult trees with different levels of tree health and one dead adult tree were selected. Two individuals having the worst and second worst health among the six live trees died three months after our study was conducted. Soil-to-leaf hydraulic conductance and leaf gas exchange rates decreased linearly as tree health declined, whereas xylem cavitation and total non-structural carbon remained unchanged in the branchlets except in the dead and most unhealthy trees. Respiration rates and the number of living cells in the sapwood decreased linearly as tree health declined. This study is the first report on the importance of dehydration tolerance and respiration maintenance in living cells.

Learning from the Past: Considering the Ethics of Appropriation

Learning from the Past: Considering the Ethics of Appropriation

Roadside Tree Management in Selected Local Authorities for Public Safety

Abstract Roadside planting is a row of trees along the road which provides shades for people in urban areas. Proper management practices among the local authorities will improve the quality of life and human well-being. Unhealthy trees may cause problems to the road users that result from the lack of monitoring by local governing bodies. 200 respondents from the public from Selayang Municipal Council and Shah Alam City Council have participated in this study. The data analysis showed that fallen trees were the main reason for the public to lodge complaints, followed by brittle branches, thick branches and leaning tree trunk.

Characterization of Fungal Pathogens Associated with White Pine Needle Damage (WPND) in Northeastern North America

Eastern white pine is a crucial ecological and economic component of forests in the northern USA and eastern Canada, and is now facing an emerging problem in white pine needle damage (WPND). It is still unclear whether WPND results from one, or the combination of several fungal pathogens. Therefore, the first objective of this study was to characterize the fungi associated with WPND in the northeastern United States and document the damage being done to mature eastern white pine as a result of repeated defoliation. To date, 22 species of fungi, either cultured from diseased pine needles or formed fruiting bodies on pine needles were identified based on morphology and sequence data. Lecanosticta acicola and a putative new species of Septorioides were the species most frequently recovered from diseased needles, in addition to needle cast fungi Lophophacidium dooksii and Bifusella linearis, two obligate fungal pathogens that were frequently observed on pine needles in the northeast, but have not been known to cause excessive defoliation of eastern white pine. A second objective was to monitor yearly the health of 63 pairs of healthy and unhealthy trees in eight affected locations throughout New England. Since 2012, affected trees are increasingly and repeatedly chlorotic and defoliated every year. Trees that were initially healthy are now exhibiting symptoms. While L. acicola appears to be the primary pathogen causing WPND, several other common needle pathogens are being more frequently observed and the role of climate change may be important in the disease ecology of WPND. These defoliation events, while once a sporadic occurrence, have now become more frequent as observed in continued crown deterioration of eastern white pine in long-term monitoring plots followed during the course of this three-year study.

Biotic mortality factors affecting emerald ash borer (Agrilus planipennis) are highly dependent on life stage and host tree crown condition.

Emerald ash borer (EAB), Agrilus planipennis, is a serious invasive forest pest in North America responsible for killing tens to hundreds of millions of ash trees since it was accidentally introduced in the 1990 s. Although host-plant resistance and natural enemies are known to be important sources of mortality for EAB in Asia, less is known about the importance of different sources of mortality at recently colonized sites in the invaded range of EAB, and how these relate to host tree crown condition. To further our understanding of EAB population dynamics, we used a large-scale field experiment and life-table analyses to quantify the fates of EAB larvae and the relative importance of different biotic mortality factors at 12 recently colonized sites in Maryland. We found that the fates of larvae were highly dependent on EAB life stage and host tree crown condition. In relatively healthy trees (i.e., with a low EAB infestation) and for early instars, host tree resistance was the most important mortality factor. Conversely, in more unhealthy trees (i.e., with a moderate to high EAB infestation) and for later instars, parasitism and predation were the major sources of mortality. Life-table analyses also indicated how the lack of sufficient levels of host tree resistance and natural enemies contribute to rapid population growth of EAB at recently colonized sites. Our findings provide further evidence of the mechanisms by which EAB has been able to successfully establish and spread in North America.

Effect of selection logging on Yellow-bellied Sapsucker sap-feeding habits in Algonquin Provincial Park, Ontario

The sap-feeding behaviour of a keystone woodpecker species, the Yellow-bellied Sapsucker (Sphyrapicus varius (Linnaeus, 1766)), was compared between high-quality uncut stands and stands harvested with various forms of selection logging in the hardwood forests of Algonquin Provincial Park, Ontario. We examined (i) the average distances that sapsuckers travelled from their nest tree to sapwell trees, (ii) the characteristics of active sapwell trees compared with overall stand characteristics, and (iii) the reuse of sapwell trees after 1 or 2 years. We found that sapsuckers travelled approximately the same average distance from their nests to sapwell trees, regardless of logging treatment. The characteristics of sapwell trees were overall unaffected by logging: unhealthy trees, sugar maple (Acer saccharum Marshall), and yellow birch (Betula alleghaniensis Britton) were used at similar proportions to their stand-level availability in reference and harvested stands. Trees with old sapwells and large-diameter trees were used significantly more than their stand-level availability; thus the retention of these trees during tree-marking procedures may preserve sap foraging habitat. The reuse of sapwell trees did not vary between treatments, and on average, over half of the sapwell trees showed evidence of reuse the following year.

Coptoborus ochromactonus, n. sp. (Coleoptera: Curculionidae: Scolytinae), an emerging pest of cultivated balsa (Malvales: Malvaceae) in Ecuador.

A new species of xyleborine ambrosia beetle has been found to attack balsa, Ochroma pyramidale (Cavanilles ex Lamarck) Urban, in Ecuador. Coptoborus ochromactonus Smith & Cognato is described and its biology is reported. Large-scale surveys were conducted between 2006 and 2009, and observational studies were carried out between 2010 and 2013 in Ecuadorian commercial plantations to determine life history and host preference characteristics. C. ochromactonus attacked balsa between 1.5 and 3 yr in age. Successful attacks were more prevalent in smaller diameter trees and unhealthy trees. In general, attacks and beetle-caused mortality were more prevalent during the dry summer months when trees were under more moisture and light stress. Fungal mycelia were consistently observed coating beetle galleries and are likely the true damaging agent to balsa trees.