Search

Urban trees and forests provide many benefits to the urban environment and are important for climate change adaptation. Yet, they are increasingly threatened by insect pests and diseases, hereafter tree pests/diseases. There is little evidence of the risk awareness and knowledge of different urban stakeholders of this growing threat, how they are affected by tree pests/diseases, and how they might respond to it. To fill this gap, we undertook an online survey of different key stakeholder groups associated with urban trees and forests in Germany. A majority of 75.8 % of the 186 respondents consider urban tree pests/diseases a severe problem and 51.1 % reported high knowledge of tree pests/diseases. There was a lack of knowledge of certain reportable quarantine pests/diseases (e.g., canker stain of plane, emerald ash borer, Xylella) and pest/disease management options (e.g., manual treatment methods and tree diversification). Respondents were most affected by the horse chestnut leafminer (61.3 %), ash dieback (58.1 %) and oak processionary moth (50.0 %). The most widely used pest remedial measures were improvements of tree living conditions (60.8 %) and purchases of plants from certified or trusted local sources (59.7 %). Multiple correspondence analysis showed a significant association between levels of knowledge of tree pests/diseases and pest management responses (11.7 %). Our results suggest that future efforts to improve urban tree health should be enhanced and tailored to the different requirements of various stakeholder groups. The findings of this first comprehensive study with a purely urban focus will inform the development of future activities that prevent or reduce the spread of tree pests/diseases in urban areas. The survey respondents did not give permission for the full data to be accessed or used by third parties. • Risk awareness and knowledge of tree pests/diseases and their management is vital for urban tree health. • Most stakeholders associated with urban trees consider tree pests/diseases a serious problem. • Only half reported a high level of knowledge of tree pests/diseases, including their spread. • Stakeholders also displayed limited knowledge of quarantine pests/diseases and management options. • Future efforts to improve urban tree health must be tailored to different stakeholder needs. [ABSTRACT FROM AUTHOR]

Citizen science has become a powerful tool for gathering data, and the validity of these data should be tested. The accuracy of a citizen science database used to monitor the polyphagous shothole borer (PSHB) (Euwallacea fornicatus) (Coleoptera: Curculionidae: Scolytinae) infestation in a suburb of the city of Johannesburg was assessed. Out of 785 trees surveyed by the citizen scientists, 157 trees (20%) were selected as a validation data set to confirm the tree identity, tree health status and level of PSHB infestation. A chi-square (χ 2) test was performed to examine whether there was a significant agreement between the citizen scientists' and researcher's data used for the classification of the tree infestation, tree health status and PSHB infestation holes. A Cohen's kappa coefficient was calculated to determine the level of agreement between the two different sources of data, for the infested parts (trunk, main branches, and canopy branches) of the trees surveyed and PSHB infestation signs. The two surveys showed no significance difference for classifying tree health status and PSHB infestation holes. There was a high level of agreement between citizen scientists and the researcher ratings for measures of PSHB infestation (kappa values ranging between 0.71 and 0.89) and the level of agreement was significant. In conclusion, citizen science allowed us to obtain a large quantity of data at a low cost that correlated with the researchers' validation dataset. Citizen science is a useful method for monitoring PSHB in a diverse urban forest in trees that show obvious signs of infestation. [ABSTRACT FROM AUTHOR]

Increasing threats from pests and diseases fundamentally question what forest management is and must do in the 21st century. The sociological concept of 'care' offers new understandings of forest management as intimate and emotional relationships between people and trees. In this paper, we examine the empirical realities of conservation forest management at a UK publicly owned site to reveal the social, economic, and institutional contexts of care and caring relations and their role in management decisions. This in-depth qualitative case study uses walking interviews with staff from all levels of the organisation and participatory data testing to show how care underpins the work of forest management, that forests are made and sustained through caring practices, and that management decisions are influenced by caring relations. Through the care framework we highlight the complexities of real-life decision-making and offer implications for forestry policy and practice. Applying the well-established components of care in a new setting, wherein the caring relations involve nonhumans, we extend care theory and demonstrate the potential of the single case study for deeply contextual forest and conservation research. • Care as feelings and activity is integral to the work of forest management. • Forests are sustained through caring practices involving relations between people and trees. • Context is integral to understanding forest management decisions. • Human-nonhuman relations of care may hold the key to more sustainable forest management. [ABSTRACT FROM AUTHOR]

Constructed soils are soils that are created with a mixture of various materials. An innovative soil exchange program - the Clean Soil Bank (CSB) in New York City allows recycling of clean glacial outwash sediments excavated from depth at construction sites. One previous study showed that soils constructed from CSB sediment and compost can effectively support crop growth in community gardens, but no research has been conducted on its potential usage as a medium for tree growth. Moreover, biochar has been used to improve soil quality, but its efficacy for street trees incorporated into constructed soils has largely not been quantified in the field. The objective of this project was to evaluate the feasibility of using soils constructed from the CSB and compost for tree planting and to investigate the impact of biochar on tree performance. Thirty-six trees of two species (Maackia amurensis and Zelkova serrata) were planted in 2019, on the sidewalks of a residential-business neighborhood in Bronx, New York. Each tree pit contains one of three soil types: type A - existing and purchased topsoil mixed with 33% compost and biochar, type B - CSB sediment mixed with 33% compost, and type C - CSB sediment mixed with 33% compost and biochar. Soil samples were collected in 2019 (before planting) and in 2021. Tree health assessments were conducted in September 2020 and July 2021 using a protocol developed by the USDA Forest Service. Other tree health parameters collected include diameter at breast height (DBH), crown diameter, tree height, photosynthetic capacity, and foliar chemistry. Significant differences in bulk density, water holding capacity, and K, Fe, and Zn concentrations were found among the three soil types. However, comparison of tree performance and foliar chemistry showed no systematic differences among the three soil types. The results indicate that CSB sediment mixed with compost can be an effective replacement for purchased topsoil for tree growth. No evidence was found that biochar provides additional benefits to street tree performance. Considering the abundant availability of glacial outwash sediment at low cost to the city, as well as access to locally produced compost, constructed soils can be a reliable source of material for urban forestry programs. • Cities are experiencing increased demand for new clean soil but soil transportation from rural areas is not sustainable. • This project aimed to study the feasibility of using constructed soil from NYC's Clean Soil Bank (CSB) for tree planting. • Thirty-six trees of two species were planted in existing and purchased topsoil or constructed soil in 2019. • Soil properties and tree health were measured in 2020 and/or 2021 and compared. • The results shows that CSB sediment mixed with compost can be an effective replacement for purchased topsoil for tree growth. [ABSTRACT FROM AUTHOR]

Despite being well adapted to the long seasonal droughts of the Mediterranean Basin, the holm oak (Quercus ilex L. subsp. ballota (Desf.) Samp.) has undergone a gradual decline during the last decades. The reasons of this decline are not fully understood, but evidence suggests that the quality and quantity of the interactions of holm oaks with the soil microbiota are playing a central role in the resilience of this species. With the aim to test the previous statement as our hypothesis, 9 oak savannah sites (called dehesas from here on) were sampled, in which asymptomatic (healthy) and symptomatic (early stage of decline) trees were interspersed. Using high throughput amplicon sequencing, soil bacterial and fungal biota (called soil microbiota from here on) were sequenced. Our results showed that soil fungal community composition differed between healthy and declining trees whereas bacterial communities did not show significant differences. Specifically, the degree of holm-oak defoliation was negatively correlated to the relative abundance of ectomycorrhizal (ECM) fungi and fungal endophytes, suggesting a relation between trees' health and soil fungal symbionts. Although our observational study cannot give a final answer to the directionality of the relationships observed, our results support the idea that small changes in symbiont abundance might be causing holm oaks to lose their ability to withstand the strong environmental pressures. • Microbial soil diversity correlates with tree health status. • Fungal diversity is more related to tree health than bacterial diversity. • The abundance of ectomycorrhiza (ECM) and fungal endophytes is related to tree resilience. • Small spatial variability in plant-fungal symbiotic relations influences tree health. [ABSTRACT FROM AUTHOR]

We describe experiences between 2018 and 2021 co-designing tree health policy options linked with the UK's evolving land use policy post EU-Exit within the Future Farming and Countryside Programme. Policy makers, researchers and more than 250 land managers took part in a series of co-design engagements in a three-phase iterative co-design process that culminated in a new Tree Health Pilot. After defining the components of co-design, we describe how relationships between policy makers, researchers and land managers were built, the methods researchers introduced into the process to build capability and support participation, and the outcomes in terms of the key opportunities and challenges for policy co-design. We conclude that it is possible to move policy design beyond user focused research and into co-design. However, this relies on adequate time and resources required to build trust and fully engage all parties in a meaningful way, including the development of tools and techniques that include experimentation, different knowledge types, and moving from research and evidence collection into design. Having policy makers with participatory mindsets in the same space as land managers was important to facilitating active learning between all of those involved in the collective. Researchers played a critical role in the co-design, balancing the views and understandings of the policy community with those of the land manager community, facilitating learning, and selecting tools and techniques to make design options explicit. We conclude that policy co-design in the land-based and environmental sector is a real opportunity at an early stage of realisation, but the effectiveness and range of positive and negative outcomes and impacts will need to be evaluated in the future. • Co-design approaches have potential to develop land use policies that better reflect land manager perspectives and realities. • Policy co-design objectives are likely to be constrained by the political and financial realities of the policy context. • Significant time and resources are required to build trust and engage policy makers and land managers in meaningful process. • Methods involved in co-design are important to who is engaged and how easily they can share detailed perspectives. • Researchers play an important role mediating and facilitating trust and learning between policy makers and land managers. [ABSTRACT FROM AUTHOR]

Monitoring of forest condition and tree performance is a long-term activity to provide data, substantiated cause-effects relationships and conclusions for environmental policies and forest management. Within this context the concept of tree and forest health, selection of response and predictor variables and challenges during statistical analyses are addressed. The terms tree and forest health are often used to characterise the performance of trees or the condition of forest ecosystems, however, the actual meanings may differ considerably. For the sake of a more coherent perception of the term health in scientific contexts and taking into account the meaning of disease(s) a more adjusted use of 'health' is recommended. Apart from the role of a working hypothesis, the selection process of meaningful response and predicting parameters is treated. On the response site the focus is on tree-related parameters like radial stem increment, crown condition, and foliar element concentrations. Each parameter reveals problems with specific implications for statistical model building. As drivers chemical properties of deposition, soil solution and soil solid phase, further foliar element concentrations, meteorological and air quality parameters are adduced. Additionally modelled plot-related values derived from external networks can be considered. Multiple regression as one of the core methods calls for unstructured residuals. To find optimal solutions especially in more intensive monitoring programmes with limited numbers of plots and many parameters is a challenge. Longitudinal and time series analyses may offer alternatives and widen the scope. While classical geostatistics may help to control spatial autocorrelation, possibilities to enlarge ecological and climatic gradients due to the inclusion of plots from similar programmes in suitable regions have to be considered as well. Unlabelled Image • System hierarchy level and causality precision may specify tree and forest health. • Success in statistical modelling needs meaningful response and predictor variables. • Hypothesis-driven regression models still essential in evaluating monitoring data. • Structure of residuals is an important quality indicator within regression modelling. • Geographic space is relevant in cause-effect relationships regarding forests. [ABSTRACT FROM AUTHOR]

• Suspended pavement practices can increase opportunities to manage urban stormwater. • Performance of two bioretention suspended pavement systems studied over 27 months. • Exfiltration, evapotranspiration were major hydrologic pathways from both systems. • Limited surface ponding, drainage-treatment area ratio led to high volume reduction. • Bioretention suspended pavement systems effectively reduced influent runoff volumes. Trees supply numerous ecosystem services to the urban environment, including mitigating the urban heat island, improving air quality, and providing habitat for wildlife. However, due to the structural stability requirements of infrastructure such as sidewalks, roadways, and parking areas, urban soils are commonly characterized by high compaction levels, low porosity, and nutrient deficiency, often to the detriment of urban tree health. By transmitting surface loads to a compacted subbase, suspended pavement systems create a matrix of uncompacted soil that promotes tree health through increased root access to oxygen, water, and nutrients. Recently, interest has grown in making suspended pavement systems multi-functional by designing them to act as subsurface bioretention practices in ultra-urban areas where space may be limited due to concentrated development and high land costs. Despite this interest, only one study has tested suspended pavement systems in this application. Further, the study utilized lined installations to allow a controlled water quality assessment; however, this negated the ability to fully quantify runoff reduction. Two unlined suspended pavement systems designed to function as subsurface bioretention practices were installed in Knoxville, Tennessee, USA, in 2015 and monitored over 27-months. During that period, over 99% of runoff volumes were reduced by the free-drained north system, which completely captured runoff from 79% of storms. The underdrained south system reduced influent runoff by over 88% and captured all runoff from 83% of events during the study. Influent TSS concentrations were significantly reduced by the south suspended pavement system, though no other significant differences between influent and effluent pollutant concentrations were observed, presumably due to low influent concentrations. This study demonstrates the viability of field-scale suspended pavement systems in a stormwater management application and illustrates the hydrologic and pollutant removal capabilities of these systems to manage urban stormwater runoff. [ABSTRACT FROM AUTHOR]

Along the Upper Gulf of Thailand, coastal fences and breakwaters have been constructed using bamboo since 2005. Despite their potential benefits, bamboo structures disintegrate within seven years releasing floating debris which severely damages mangrove tree stems. The aim of the study was to investigate whether such stem damage resulted in the decline of Avicennia spp. stands along the Upper Gulf of Thailand. Tree health assessments were conducted to assess the probability of crown dieback in damaged and undamaged trees. Satellite-derived time-series of vegetation indices were used to detect long-term forest decline. In contrast to the unaffected landward mangroves, seaward mangroves were unable to recover from insect-induced defoliation events after the collapse of a nearby fence. Furthermore, there was a significantly higher probability that damaged trees showed signs of moderate-to-severe crown dieback. It is recommended that bamboo fences be secured by replacing individual stems before they become detached. • Debris from deteriorating coastal bamboo fences damage stems of mangrove trees. • Damaged trees are more likely show signs of crown dieback. • Seaward mangrove forests are declining. [ABSTRACT FROM AUTHOR]

Declines are a distinctive category of tree disease, complex to define and quantify and challenging to mitigate due to their multiple causes and heterogeneous tree response patterns. In many parts of Europe oak decline syndromes are severely impacting tree health and having a measurable economic impact on forestry. In the UK the impact of periodic oak declines is expanding against a backdrop of multiple environmental pressures, to levels capable of threatening the UK's native oak woodland. Here we explore the growth histories of oak trees at a site symptomatic of Chronic Oak Decline (COD), in the South of England; Speculation Cannop in the Forest of Dean, Gloucestershire. The dendrochronological picture at the site reveals that trees with current external COD symptoms have shown suppressed growth, in relation to the regional average, from early on in their lives. Moreover, there is an amplified reduction in minimum ring width in Symptomatic trees as compared to a healthy subsample of Control trees, likely to be heavily dominated by reduced latewood width in affected trees, as decline sets in. Broadly, the site reveals the initial appearance of decline, roughly 40 years after planting, in 1860. There is considerable variability in the later decline history pattern in Symptomatic trees but there are clusters of decline episodes in the 1920s, 1960s, 1980s and 1990s at this site. The Control trees are not always unaffected but rather show growth releases after each historical decline phase. The trees that currently show external decline symptoms do not have a history of these growth releases. We conclude that investigating the tree ring growth histories at sites impacted by COD could provide an important management tool, and ring width histories of trees at affected sites should be used in the identification of the decline predisposing factors, that a management strategy requires. [ABSTRACT FROM AUTHOR]

(A) Hyophorbe lagenicaulis demonstrating high quality and normal (modal) live frond ratio for the specimens assessed (a recently-transplanted population); (B) Livistonia chinensis demonstrating high quality and 40–60% live frond ratio; (C) Sabal palmetto demonstrating 0–20% quality (chlorosis of living fronds) and 0–20% live frond ratio (with reference tool superimposed over canopy for demonstration); (D) Reference tool with brief guidelines for assessing palm live frond ratio. Palms (family Arecaceae) can make up a significant portion of the urban forest in the climates where they are viable. Despite this, they are rarely included in the urban forest growth and longevity literature. One difficulty associated with including palms in research is an absence of a standard means for characterizing tree health or condition. Whether used as a measured response of its own or incorporated as a predictor of future mortality, standardized and meaningful health ratings are needed to advance the care and management of palms in urban areas. In this short communication, we investigate some of the rating systems used in past palm research. We then propose an adaptation of existing tree health rating processes based on insights from these past attempts and our own experience in qualifying palm health. [ABSTRACT FROM AUTHOR]

Environmental and land use policy literature asserts the need for more holistic, participatory and co-designed forms of governance for the sustainable management of natural resources. Co-design is also increasingly recognised by government as a useful approach but is often applied with varying degrees of success. The purpose of this paper is to assess recent examples of policy co-design across three UK case studies focused on tree/woodland management and fisheries. The first set out to co-design criteria for 'low impact' fishing with fisheries stakeholders to inform new fisheries policy and management strategies. The second co-designed new policy options with tree/woodland stakeholders to replace existing tree health grants, as part of the UK government's broader Environment Land Management scheme. The third aimed to scope, with stakeholders, the potential for a new social survey of fishers. Despite the different contexts, all projects sought to apply principles of co-design by engaging with stakeholders during the early stages of policy development. A comparative assessment between the three case studies allows us to identify challenges for co-design and to provide recommendations for successfully applying co-design principles through stakeholder-researcher-policy maker partnerships. Challenges include building trust between stakeholders and policymakers, overcoming traditional modes of evidence-based policy making, accessing hard-to-reach groups, getting discussions to move beyond the general to the specific, and recognising that co-design takes time and is resource-intensive. A new co-design framework is presented, setting out five stages for incorporating the principles of co-design in natural resource policy making: scoping, co-design, testing, implementing and evaluation. • Co-design is growing in prominence as an approach for land use policy making. • Co-design is time & resource intensive, requiring commitment of policy makers. • Building trust between policy makers & stakeholders is vital for effective co-design. • The co-design framework involves 5 stages & aims for more equitable policy outcomes. [ABSTRACT FROM AUTHOR]

Hurricane Sandy was the second costliest hurricane in United States (U.S.) history. The category 2 storm hit New York City (NYC) on the evening of October 29, 2012, causing major flooding, wind damage, and loss of life. The New York City Department of Parks & Recreation (NYC Parks) documented over 20,000 fallen street trees due to the physical impact of wind and debris. However, salt water flooding may have caused additional stress to approximately 48,000 street trees located in the storm’s inundation zone. Early in the first growing season following Hurricane Sandy (June 2013), NYC Parks staff examined these street trees and found that 6,864 of the flooded trees had a significant proportion of their crown fail to leaf out. Thirty percent of those trees did not leaf out at all. The most commonly affected trees were London plane ( Platanus  ×  acerifolia ) and maple species ( Acer spp.). Here we show that red maple ( Acer rubrum ) is negatively impacted by salt water flooding but can recover over time. London plane trees, on the other hand, experience high mortality and show no signs of recovery 3 years post Sandy. We demonstrate that by 2080 a similar storm could impact almost 100,000 of NYC’s street trees. These findings have global implications for coastal urban forests as we face sea level rise and an increasing frequency and magnitude of coastal storms. [ABSTRACT FROM AUTHOR]

Urban street trees are part of the bundle of environmental amenities that support healthy social, economic, and environmental functions. In this study, we systematically evaluate the quality of 196,825 street trees at the US. Census tract level in Washington D.C., as well as related impacts from socioeconomic, landscape patterns and environmental factors using Ordinary least-squares (OLS) regression, geographically weighted regression (GWR) and structural equation modeling (SEM). Our results reveal that environmental and socioeconomic factors can explain most of the spatial variation of street tree quality in Washington, D.C. There is a substantial statistical negative relationship between median household income and the percent of street trees under stress, which provided the evidence of the inequities of street tree quality in Washington D.C. Higher-income neighborhoods exhibited a lower proportion of street trees under stress. In addition, the extreme summer temperature is positively associated with the proportion of street trees under stress. The quality of street trees is directly impacted by environmental and landscape pattern factors. There is also an indirect impact from socioeconomic factor toward quality of street trees. Our findings suggest that multiple variables, related to income, age, education, landscape pattern, and environment contribute to the quality of street trees in D.C. Based upon our findings, we identify strategies and insights for urban street tree management in DC to not only address environmental inequity and injustice, but also promote a more inclusive and resilient urban greenery system. [ABSTRACT FROM AUTHOR]

The Social Amplification of Risk Framework (SARF) is often used as a conceptual tool for studying diverse risk perceptions associated with environmental hazards. While widely applied, it has been criticised for implying that it is possible to define a benchmark ‘real’ risk that is determined by experts and around which public risk perceptions can subsequently become amplified. It has been argued that this objectification of risk is particularly problematic when there are high levels of scientific uncertainty and a lack of expert consensus about the nature of a risk and its impacts. In order to explore this further, this paper examines how ‘experts’ – defined in this case as scientists, policy makers, outbreak managers and key stakeholders – construct and assemble their understanding of the risks associated with two invasive tree pest and disease outbreaks in the UK, ash dieback and oak processionary moth. Through semi-structured interviews with experts in each of the case study outbreaks, the paper aims to better understand the nature of information sources drawn on to construct perceptions of tree health risks, especially when uncertainty is prevalent. A key conclusion is that risk assessment is a socially-mediated, relational and incremental process with experts drawing on a range of official, anecdotal and experiential sources of information, as well as reference to past events in order to assemble the risk case. Aligned with this, experts make attributions about public concern, especially when the evidence base is incomplete and there is a need to justify policy and management actions and safeguard reputation. [ABSTRACT FROM AUTHOR]

Research into remote sensing tools for monitoring physiological stress caused by biotic and abiotic factors is critical for maintaining healthy and highly-productive plantation forests. Significant research has focussed on assessing forest health using remotely sensed data from satellites and manned aircraft. Unmanned aerial vehicles (UAVs) may provide new tools for improved forest health monitoring by providing data with very high temporal and spatial resolutions. These platforms also pose unique challenges and methods for health assessments must be validated before use. In this research, we simulated a disease outbreak in mature Pinus radiata D. Don trees using targeted application of herbicide. The objective was to acquire a time-series simulated disease expression dataset to develop methods for monitoring physiological stress from a UAV platform. Time-series multi-spectral imagery was acquired using a UAV flown over a trial at regular intervals. Traditional field-based health assessments of crown health (density) and needle health (discolouration) were carried out simultaneously by experienced forest health experts. Our results showed that multi-spectral imagery collected from a UAV is useful for identifying physiological stress in mature plantation trees even during the early stages of tree stress. We found that physiological stress could be detected earliest in data from the red edge and near infra-red bands. In contrast to previous findings, red edge data did not offer earlier detection of physiological stress than the near infra-red data. A non-parametric approach was used to model physiological stress based on spectral indices and was found to provide good classification accuracy (weighted kappa = 0.694). This model can be used to map physiological stress based on high-resolution multi-spectral data. [ABSTRACT FROM AUTHOR]

Invasive alien species, including pests and diseases of plants and animals, are a major cause of biodiversity change and may impact upon human well-being and the economy. If new, potentially invasive, taxa arrive then it is most cost-effective to respond as early in their establishment as possible. Information to support this can be gained from volunteers, i.e. via citizen science. However, it is vital to develop ways of quantifying volunteer recorder effort to assess its contribution to the detection of rare events, such as the arrival of invasive alien species. We considered the potential to detect adult oak processionary moths ( Thaumetopoea processionea ) by amateur naturalists recording moths at light traps. We calculated detection rates from the Netherlands, where T. processionea is widely established and poses a risk to tree health and human health, and applied these to the spatial pattern of moth recording effort in the UK. The probability of recording T. processionea in the Netherlands varied across provinces from 0.05–2.4% per species of macro-moth recorded on a list of species (so equalling 1–52% for a list of 30 species). Applying these rates to the pattern of moth recording in the UK: T. processionea could be detected (detection > 0%), if it were present, in 69% and 4.7% of 10 km and 1 km squares, respectively. However, in most squares detection probability is low (< 1% of 1 km squares have annual detection probability of > 10%). Our study provides a means to objectively assess the use of citizen science as a monitoring tool in the detection of rare events, e.g. the arrival of invasive alien species, occurrence of rare species and natural colonisation. [ABSTRACT FROM AUTHOR]

Declining forest health can affect crucial ecosystem functions, such as carbon storage in biomass and soils, the regulation of water regimes, the modulation of regional climate and conservation of biodiversity. Airborne laser scanning (ALS) and imaging spectroscopy (IS) are two potentially complementary remote sensing technologies capable of characterizing and monitoring regional forest health. However, the combined use of ALS and IS data to classify the health of individual trees has not yet been assessed. In this study we propose a new approach utilizing ALS and IS combined to characterize the health of individual trees. Firstly, we applied a recently developed bottom-up individual tree delineation algorithm across a structurally complex floodplain eucalypt forest that has experienced episodes of severe dieback over the past six decades. We further calculated ALS and IS indices for delineated tree crowns and used them as predictor variables in machine learning models. We trained and evaluated an object-oriented random forest classifier against field-measured tree crown dieback and transparency ratios, as indicators of eucalypt tree health and crown density, respectively. Our results showed that dieback levels of individual trees can be classified using ALS and IS with an overall accuracy of 81% and a kappa score of 0.66, while the classification of tree crown transparency levels had an overall accuracy of 70% and a kappa score of 0.5. Returned pulse width, intensity and density related ALS indices were the most important predictors in the tree health classification, as they accounted for > 40% of the variance in the data. At the forest level in terms of dieback, 81.5% of correctly delineated trees were classified as healthy, 12.3% as declining and 6.2% as dying or dead. Dieback occurred primarily in areas that were flooded < 5% of the time, as quantified by Landsat derived flooding frequency (1986–2011). Our results provide a novel application of ALS and IS to accurately classify the health of individual trees in a structurally complex eucalypt forest, enabling us to prioritize areas for forest health promotion and conservation of biodiversity. [ABSTRACT FROM AUTHOR]

An analysis of tree health in urban greeneries exposed to winter road salt contamination was carried out in the cities of Alytus and Kaunas, Lithuania, during spring and summer 2009–2014. Trees were assessed for crown dieback, crown defoliation and foliage discolouration. In addition, the prevalence of saprotrophic pathogenic fungi that cause sooty mold disease was assessed in street and recreational plantings. Tilia cordata Mill. (small-leaved lime) was found to be the most common tree species among urban deciduous trees. Summarising the tree foliage results, saprotrophic fungi were detected on 16 species plants belonging to 13 genera. Three species of fungal pathogens belonging to two genera, two families, two classes, and two divisions, and 12 species of anamorphic fungi from nine genera were isolated and identified from Tilia cordata leaves. The most frequent sooty mold disease agents were Aspergillus brasiliensis and Cladosporium herbarum . Nonetheless, a weak correlation between salt contamination and lime tree damage by sooty mold was found. [ABSTRACT FROM AUTHOR]

Assumptions about public stakeholder attitudes to pest and disease management can influence the decisions of forest managers and NGOs involved in responding to pests and diseases; however, they are rarely assessed directly. Evidence on the social acceptability of tree health management methods is required to inform government led policy and management. A nationally representative survey of 2000 members of the UK public was used to address two research questions: (1) How acceptable are tree health management methods to the public? (2) How do opinions about woodland functions, concern and awareness of tree pests and diseases, and demographics influence acceptance of management methods? We found that public stakeholders are highly supportive of tree health management; however, knowledge about tree pests, diseases, and management options is low. Methods seen as more targeted and ‘natural’ were preferred, e.g. felling and burning only affected trees and using biological control rather than chemical control. There were demographic differences in attitudes: men and older people are more likely to support management interventions and stronger management methods than females and younger people. Acceptance of management can also differ according to location and local context (e.g. management is less supported when it may impact on wildlife) and values (e.g. those with economic values are more supportive of management). These findings provide evidence to support current government initiatives on tree health and should improve confidence amongst managers tasked with carrying out tree pest and disease management. However, there is a need for in-depth qualitative studies to explain the beliefs which influence demographic variations in acceptance and the influence of concepts such as ‘nativeness’ and ‘naturalness’. [ABSTRACT FROM AUTHOR]

Understanding how soil nutrients affect sap sweetness of sugar maples ( Acer saccharum Marsh.) is important for producing maple syrup, an economically important non-timber forest product in the northeastern USA and southeastern Canada. Sugar maples were sampled for sap sweetness in 21 plots distributed across five stands in the White Mountains of New Hampshire. Sugar concentrations in maple sap were higher in plots with greater native soil nitrogen availability, indicated by N mineralization in laboratory incubations ( p = 0.01). To test whether nutrient additions can improve sap sweetness, treatment plots were fertilized with N, P, N and P, or Ca. Addition of 30 kg N ha −1 yr −1 increased sap sweetness two years after initial treatment. Foliar P had a negative correlation with sap sweetness ( p = 0.02) while trees with higher foliar N:P had sweeter sap ( p < 0.001). By selecting sites with higher soil nitrogen or fertilizing N-limited sites with N, maple sugar producers may be able to collect sweeter maple sap. [ABSTRACT FROM AUTHOR]

Abstract: In the Eden area in NSW, Australia, low fertility granitic surface soils were sampled from 156 sites and analysed for pH, organic C, total N, total P, available P, exchangeable bases and exchangeable Al. Fifty eight of these sites were also sampled to a depth of 40cm. Time since fire ranged from 1 to 39 years and was used in the analysis as a surrogate for fire frequency. No information was available on fire intensity. No significant relationships were found between time since fire and P or base cations. However, the quantities of organic matter and total N (kgha−1), and the C/N ratio were significantly related to both time since fire alone and to the combination of time since fire and soil total P. Based on these relationships, it was estimated that there were average net increases of between 11 and 21kgNha−1 year−1 in surface soil, the actual quantity depending on the level of soil total P. There was little change in N in the initial 10 years after fire and there was a peak in N accumulation about 24 years after fire. The C/N ratio and surface soil pH decreased with time since fire. Accumulation of N and reductions in pH and C/N ratio were studied further in a small scale paired plot analysis. The repeatedly burnt plots had lower levels of both litter and understorey and the overstorey trees generally had healthier crowns than in the unburnt plots. The differences between the repeatedly burnt and the unburnt plots matched the models developed from the general survey. There were no significant changes in the C/N ratio, but the unburnt sites had higher levels of extractable mineral N and the relationships between the mineral N and the C/N ratio for burnt and unburnt sites were statistically significant. The quantities of extractable mineral N in the unburnt soils (2.3kgNha−1) were about twice the levels in the burnt soils (1.2kgNha−1). The pH of the surface soil (4.4 in 1:1 water) in the regularly burnt area was higher than in the unburnt area (pH 4.1) and the exchangeable aluminium also differed (0.62cmol−1 in the burnt area and 1.3cmol−1 in the unburnt). The combined data indicate that changes occur in forest soils when there is a long period of exclusion of fire. It is suggested that these changes generally lead to secondary changes, such as in pH and availability of other elements such as aluminium. The study highlights a number of issues including the rates of inputs of N to the system and the question of N saturation and its long term interaction with plant species. It is hypothesised that reduced burning leads to increased N availability and other soil changes which negatively impact on tree health. [Copyright &y& Elsevier]

Abstract: In many respects, the ecology of members of the Botryosphaeriaceae compare to general patterns observed for the collective of endophytes of woody plants. These include high levels of diversity, horizontal transmission a spatial structure and a continuum of levels of host affinity from specific to very broad. Some members of the Botryosphaeriaceae are, however, among the most aggressive pathogens in the assemblages of common endophytic fungi, often killing large parts of their host, following physical damage or general stress on the host (and over large areas). Their wide occurrence, the latent phase which can be overlooked by quarantine, and their ability to rapidly cause disease when their hosts are under stress, make these fungi a significant threat to agricultural, plantation and native forest ecosystems alike. This is especially relevant under emerging conditions of dramatic climate change that increases stress on plant communities. It is, therefore, important to maximize our understanding of the ecology and pathology of the Botryosphaeriaceae, particularly as it relates to their endophytic nature, species richness, host switching ability and the host-fungus-environment interaction. [Copyright &y& Elsevier]

Since environmental conditions and cultural practices vary from one area to another, yield, fruit quality, and tree health measurements were conducted over 9 years to evaluate the long-term adaptability and performance to local conditions of ‘Allen Eureka’ lemon (Citrus limon Burm.f.) budded on seven rootstocks in the Najran area of Saudi Arabia. Trees on Citrus macrophylla (CM), Volkamer lemon (VL), and Cleopatra mandarin (Cleo) were the most productive, while trees on Amblycarpa (Amb), rough lemon (RL), Citrus taiwanica (CT), and sour orange (Citrus aurantium L.) (SO) had the lowest yield. Fruit from trees on CM and VL were also the largest in size and had the thickest rind, but were among those that had the lowest juice content and lowest total soluble solids. None of the trees on Cleo, VL, or RL died until the 14th year. However, there was a high mortality rate and severe tree decline on SO, CT, and Amb. [Copyright &y& Elsevier]

• Study found a relationship between structural root depth and landscape tree health. • Stem encirclement by tree roots increases with depth from soil surface to structural roots. • Planting depth and stem girdling roots were predictors of tree condition. • Greater boulevard width for street trees was associated with greater tree condition. • Results reinforce a recommendation to detect and correct root depth prior to tree planting. The relationships of structural root depth, stem girdling roots, stem diameter, and boulevard width were studied on the condition of four tree species (Acer saccharum L., Celtis occidentalis L., Fraxinus pennsylvanica Marsh, and Tilia cordata Mill.) grown as street trees. The relationship between depth from the soil surface to the structural roots and development of stem encircling roots and stem girdling roots was also determined. Stem girdling roots, boulevard width, and root depth were significant predictors of tree condition. Tree condition was greater as boulevard width increased, but stem girdling roots and structural root depth had a negative relationship on tree condition. Depth to structural roots was positively related to the percentage of the tree stem circumference with stem encircling roots and also for stem girdling roots. For every cm the structural roots were below the soil surface, 3.3 % of the stem was encircled. Thus, a 10 cm root depth translates to approximately 1/3 of the stem with encircling roots. With stem girdling roots, an approximate 1 % of the stem was girdled for each cm that structural roots were below the surface. Results from the measurement of 398 trees that were approximately 10–20 years post planting provide additional justification for maintaining structural roots at the soil surface. Results also demonstrate the importance for planning tree planting locations with adequate boulevard widths to foster tree health. Findings have implications with nursery production, tree planting, and arboricultural treatments to remove soil away from tree stems and expose structural roots at planting and subsequently with established trees. [ABSTRACT FROM AUTHOR]

During the past decades, extreme events have become more prevalent and last longer, and as a result drought-induced plant mortality has increased globally. Timely information on plant water dynamics is essential for understanding and anticipating drought-induced plant mortality. Leaf water potential (Ψ L), which is usually measured destructively, is the most common metric that has been used for decades for measuring water stress. Remote sensing methods have been developed to obtain information on water dynamics from trees and forested landscapes. However, the spatial and temporal resolutions of the existing methods have limited our understanding of the water dynamics and diurnal variation of Ψ L within single trees. Thus, we investigated the capability of terrestrial laser scanning (TLS) intensity in observing diurnal variation in Ψ L during a 50-h monitoring period. We aimed to improve the understanding on how large a part of the diurnal variation in Ψ L can be captured using TLS intensity observations. We found that TLS intensity at the 905 nm wavelength measured from a static position was able to explain 77% of the variation in Ψ L for three trees of two tree species with a root mean square error of 0.141 MPa. Based on our experiment with three trees, a time series of TLS intensity measurements can be used in detecting changes in Ψ L , and thus it is worthwhile to expand the investigations to cover a wider range of tree species and forests and further increase our understanding of plant water dynamics at wider spatial and temporal scales. • Laser intensity metrics explained 56–77% of the variation in leaf water potential. • The 905 nm wavelength showed better performance compared to the 1550 nm wavelength. • Best-performing intensity metrics differed between species. [ABSTRACT FROM AUTHOR]

• Quantitative data on development rates of tree microhabitats (TM) are scarce. • Published rates of development of five common TM reviewed. • TM supply formed by initiating events, tree response, and environmental modifiers. • Tree age and growth rate interact in TM dynamics. • Long-term strategy for TM conservation outlined. Many tree-dwelling species inhabit microhabitats that develop slowly in diseased or injured trees. Conservation planning would benefit from explicit knowledge of these processes, notably for resolving conflicts with timber production, arboricultural or public safety goals. We reviewed published rates of development of five selected common tree microhabitats and the factors affecting those rates in living trees. Most of the 71 relevant studies found globally focused on tree-cavities and exposed wood, while the development of witches' broom, bark pocket and dendrotelm microhabitats remains poorly described. Three time parameters emerge as central: minimum tree age; rate of formation; and persistence time of the microhabitat. Among the studied microhabitats, large side cavities are formed in the oldest trees, seldom hosting large vertebrates in trees <100 years old. In contrast, the development of exposed wood, bark pockets and dendrotelms can be compatible with some approaches of even-aged production forestry. The evidence indicates that tree growth rate is a key effect modifier of microhabitat development, which supports short-term wound occlusion but can also expose the tree to chronic disease and decay. For example, side cavities usually develop more rapidly in fast-growing trees, but persist longer in slow-growing trees. Environmental exposure regulates microhabitat development by affecting these growth and degradation responses and pathogen performance, but typical ranges of natural variation in microhabitat development rates can also be distinguished. To mitigate conservation conflicts with production forestry and the management of human environments, microhabitat prone trees should be considered across multiple management cycles, notably to sustain large side-cavities and witches' brooms. We outline retention forestry approaches, reduction of salvage logging, and veteran tree management in the countryside and urban environments as the key arenas of action. Given the high variation in tree microhabitat development, a successful strategy would combine fine-scale retention of existing microhabitats and landscape-scale prediction and planning for future microhabitat formation. [ABSTRACT FROM AUTHOR]

• Tree status and leaf traits were measured on individuals of three broadleaved species. • Defoliation and damage symptoms were related in all the three species examined. • Defoliated European beech trees had reduced leaf area and photosynthetic efficiency. • Leaf traits can favour a physiological interpretation of defoliation and damage. Tree crown defoliation is the most widespread indicator of forest health and vitality in Europe. It is part of the ICP Forests Pan-European survey and it is adopted for reporting under Forest Europe. It is readily understandable and can count on fairly harmonized, long-term, large-scale data series across Europe. On the other hand, it is unspecific with respect to possible causes of damage, and its relation with tree functioning remains unclear. This study focused on European beech (Fagus sylvatica L.), Turkey oak (Quercus cerris L.), and holm oak (Quercus ilex L.), three important broadleaved forest species in southern Europe. We investigated whether and to what extent morpho-physiological (functional) leaf traits and other indicators of foliar, branch and stem health condition are associated with tree defoliation. We tested the relationship between defoliation and leaf-, branch- and stem attributes, and whether indicators of damage and functional leaf traits significantly differ (Mann-Whitney U Test) between defoliated (defoliation > 25%) and undefoliated trees (defoliation ≤ 25%). For each species, we considered one site (three to five plots each) and n = 11–19 randomly selected trees. For each tree, the following indicators were measured: crown condition (defoliation; leaf-, branch- and stem damage, in terms of extent and intensity of damage), leaf morphology (leaf thickness, leaf area, lamina length, fluctuating asymmetry, specific leaf area, damaged leaf surface), leaf physiology and chemistry (chlorophyll a fluorescence, chlorophyll content, carbon and nitrogen stable isotopes composition δ13C, δ15N, carbon/nitrogen ratio). Results show that, for the selected trees of all the three species, defoliation was positively related to the extent of damage on branches. While increasing defoliation in European beech was also accompanied by several significant differences at leaf level (i.e., leaf damage, leaf volume, dry weight, carbon/nitrogen ratio and photosynthetic efficiency), for Turkey oak and holm oak the significant differences between defoliated and undefoliated trees were limited to damage on branches (both species). [ABSTRACT FROM AUTHOR]

Hedgerows structure agricultural landscape worldwide but little is known on their soil communities. In the intensively managed agricultural landscapes of Ireland and the UK, hedgerows protect soil from degradation and are thought to provide a reservoir of soil biodiversity for the farmed fields. But hedgerows are currently threatened by emergent tree diseases spread with rising volumes of trade in plants. This study analysed the effect of the most dominant hedgerow tree species on the composition and diversity of soil communities, which we estimated with oribatid mites in the context of an imminent ash dieback outbreak in Northern Ireland. We hypothesised that the environmental heterogeneity created by different tree species and good tree health are beneficial to the abundance and diversity of these soil communities. We found that communities differ, both in terms of species composition and relative abundances, between different trees in the trimmed hedgerows, and between untrimmed and trimmed hedgerows. The presence of trees was associated with more variable species composition. The analysis of phospholipid fatty acids (PLFA) showed that pasture and adjacent hedgerows were dominated by bacteria but there was no clear relationship between bacterial biomass and oribatid abundance or richness. However, changes in bacterial PLFAs were correlated positively with changes in oribatid community composition. Soil under ash trees which were diseased supported a higher species richness and greater abundance of oribatids than healthy trees. We conclude that the presence of different tree species in hedgerows adds to the overall diversity of soil hedgerow communities and hypothesise that the structural heterogeneity created by tree canopy drives increased diversity. Ill health in ash trees is currently positively affecting oribatid communities, possibly due to the temporarily increase in organic matter in soil. The epidemic of ash dieback, however, is expected to kill and remove trees in the medium term and so reduce soil community diversity in the long term. • Hedgerows host significant soil oribatid mite biodiversity. • Trimmed hedgerows and tree standards have distinct species composition. • The presence of trees in trimmed hedgerows increases biodiversity. • The positive short term effects of diseased tree may reverse in the long term. [ABSTRACT FROM AUTHOR]

Climate change is causing novel forest stress around the world due to changes in environmental conditions. Forest pest insects, such as Ips typographus (L.), are spreading toward the northern latitudes and are now able to produce more generations in their current range; this has increased forest disturbances. Timely information on tree decline is critical in allowing forest managers to plan effective countermeasures and to forecast potential infestation areas. Field-based infestation surveys of bark beetles have traditionally involved visual estimates of entrance holes, resin flow, and maternal-gallery densities; such estimates are prone to error and bias. Thus, objective and automated methods for estimating tree infestation status are required. In this study, we investigated the feasibility of dual-wavelength terrestrial lidar in the estimation and detection of I. typographus infestation symptoms. In addition, we examined the relationship between leaf water content (measured as gravimetric water content and equivalent water thickness) and infestation severity. Using two terrestrial lidar systems (operating at 905 nm and 1550 nm), we measured 29 mature Norway spruce (Picea abies [L.] Karst.) trees that exhibited low or moderate infestation symptoms. We calculated single and dual-wavelength lidar intensity metrics from stem and crown points to test these metrics' ability to discriminate I. typographus infestation levels using regressions and linear discriminant analyses. Across the various I. typographus infestation levels, we found significant differences (p < 0.05) in gravimetric water content, but not in equivalent water thickness due to the latter statistic's high correlation with leaf density. The results show correlations between the lidar intensity metrics and several infestation symptoms: defoliation, discoloration and resin flow. The intensity metrics explain 50% of the variation in the infestation severity (as determined in the field based on canopy and stem symptoms). The overall accuracy with three infestation classes (no , low , or moderate) was 66%, but the overall accuracy with two infestation classes (not infested , or infested) was 90%. The classifiers combine lidar intensity metrics from the stem and the canopy to allow for the detection of bark-beetle infestations in the early, so called green-attack stage. The intensity metrics explain part of the variations in tree-level gravimetric water content and equivalent water thickness, with adjusted R2 values of 0.48 and 0.68, respectively. Terrestrial dual-wavelength lidar shows potential for providing objective tree-decline measurements at tree level: this method can be further used to enhance forest inventories and automate tree-vigor data collection, which has traditionally required expert knowledge. Unlabelled Image • Dual-wavelength lidar shows potential in early detection of bark beetle infestation. • Infested trees were classified with 90% overall accuracy. • Lidar intensity of 905 nm was sensitive to bark-beetle-induced resin flow. • Leaf water content metrics showed varying responses to bark-beetle colonization. [ABSTRACT FROM AUTHOR]

Urban tree planting initiatives can experience high levels of mortality during establishment years. Mortality tied to the stresses of transplanting can be partially negated or exacerbated depending on the species selected, nursery materials used, site conditions present, and management practices employed. Past research has quantified post-planting survival, health, and growth. However, varying climates, species, land use types, and management practices warrant additional region-specific research. The purpose of this study is to assess the success of plantings along Florida highways and identify species, site, and management factors related to tree and palm health and establishment. Results show high establishment survival (98.5%) across 21 planting projects ranging from 9 to 58 months after installation (n = 2711). For transplanted palms, the presence of on-site irrigation significantly improved establishment from 96.2% to 99.4%. No establishment differences were detected with regard to irrigation treatment for small-stature trees, shade trees, and conifers. Additionally, there were significant differences in tree health response among tree groups given species, management, and site factors. [ABSTRACT FROM AUTHOR]