Preston, United Kingdom
Preston, United Kingdom

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Shields S.,Myerscough College | Slater D.,Myerscough College
Arboricultural Journal | Year: 2017

A significant body of recent research has identified that trees in the urban environment provide considerable benefits to society, both providing desirable places to live and helping to reduce the impact of the urban population on the wider environment. If we are to continue to benefit from the urban forest in the future, a knowledge of the existing resource, its condition and future viability is a fundamental requirement. The design and creation of newly built development present one of the biggest threats to and greatest opportunities for urban forests but have not been analysed in depth. An assessment using i-tree ECO recorded the extent, nature and quality of the urban forest resource in residential areas of the town of Shrewsbury. Comparisons were then made between three separate study areas within the town based upon the period in which they were primarily constructed. The pre-1950 residential housing areas had significantly greater canopy cover (17.8%) when compared with 1951–1985 housing (13.1%) and post-1985 housing areas (9.9%). Analysis of tree age, size and ownership distributions identified that larger growing garden trees in the earlier housing schemes were the major contributor to this difference in canopy cover between areas. For this case study, we can conclude there is a negative trend in urban canopy cover that relates to the size of garden space allocated to more modern residential properties, which is not sufficiently compensated for by tree planting in adjacent public areas. © 2017 Informa UK Limited, trading as Taylor & Francis Group and Arboricultural Association

Slater D.,Myerscough College | Ennos A.R.,University of Manchester
Trees - Structure and Function | Year: 2013

The ability to accurately predict the load-bearing capacity of tree forks would improve tree surveying and tree surgery techniques and assist with the biomechanical modelling of a tree's structure. In this study, the bending strength of forks of hazel (Corylus avellana L.) was investigated by assessing the mechanical contributions from three component parts of each fork. Intact forks and ones in which either central or peripheral xylem lying under the branch bark ridge at the apex of the forks had been removed were subjected to tensile tests. The bending strength of these forks was compared with that of the arising branches by carrying out a three-point bending test on the smaller arising branches of the intact specimens. All forks failed in tension, splitting between the arising branches. By removing the centrally placed xylem, constituting approximately a fifth of the width of the fracture surface, the forks' bending strength was reduced by around 32 %, while removing the outer four-fifths reduced the forks' bending strength by 49 %. Intact forks had around 74 % of the maximum bending strength of the smaller arising branch. It is concluded that the tensile strength of the centrally placed xylem at the apex of a tree fork is a critical strengthening component. This helps to explain the weakness of forks with included bark, which lack this component. This study concludes that tree forks should not by default be considered flaws in a tree's structure. © 2013 Springer-Verlag Berlin Heidelberg.

Sjoman J.D.,Swedish University of Agricultural Sciences | Hirons A.,Myerscough College | Sjoman H.,Swedish University of Agricultural Sciences
Journal of Environmental Quality | Year: 2016

The chief aim of this study was to investigate how different species of solitary trees in temperate urban areas vary in their branch structure during winter by assessing branch area indices (BAIs). The BAI data showed significant differences (P < 0.0001) between species and genotypes. The lowest mean BAI in the dataset was for Gingko biloba L., which had a BAI of 0.27. Pinus strobus L. 'Fastigiata' represented the largest mean BAI of 2.09. The results from the BAI analysis further indicate that within the same species group differences occur between genotypes. For example, the five genotypes of Acer platanoides L. range from a mean BAI of 1.77 for A. platanoides 'Globosum' to a mean BAI of 0.50 for A. platanoides 'Fassen Black'. A further aim was to apply the compiled BAI data in the computational modeling program of ENVI-met 3.1, which simulates the surface-air interaction and microclimates in complex urban settings. The simulations focused on mean radiant temperature and wind speed. Results illustrate how wind speed on the leeward side of the trees gradually decrease with an increasing BAI. With an increasing BAI, the Tmrt decreases to the leeward of the row of trees. The results are further discussed in the perspective of sustainable urban development (i.e., where, why, and how the species studied could be integrated in the urban fabric). This is of particular interest for the design of urban green space in densely built-up urban environments where space may be restricted. © American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. 5585 Guilford Rd., Madison, WI 53711 USA.

Lawrence A.,Japan Forestry and Forest Products Research Institute | De Vreese R.,Vrije Universiteit Brussel | Johnston M.,Myerscough College | Konijnendijk van den Bosch C.C.,Copenhagen University | Sanesi G.,University of Bari
Urban Forestry and Urban Greening | Year: 2013

Research on urban forest governance is scarce, despite the current high level of interest in urban forestry. This paper addresses one of the main reasons for this scarcity - poor understanding of what governance is, and how it can be described. We propose a systematic approach to researching urban forest governance, based on a case study framework which provides a way to describe examples clearly, and to compare them robustly. The paper briefly reviews definitions and debates around governance, before using a descriptive definition as the basis for developing a framework. It then uses five examples from across Europe, to illustrate the use of the framework for describing urban forest governance. The analysis reflects on the experience of writing and sharing case studies, to distill out the framework as a research tool, and discusses issues arising from the application of the framework and the challenges of standardisation. The paper concludes with reflections on the role of this framework in stimulating comparisons while maintaining the flexibility to contribute to individual research needs and traditions. © 2013.

Johnston M.,Myerscough College
Arboricultural Journal | Year: 2010

In February 2008, the Department for Communities and Local Government published its long awaited report on urban trees in England entitled Trees in Towns II. The report assesses the urban tree population in England as well as identifying the policies and practice of urban tree management by English local authorities. This paper highlights the significance of this government report for the arboricultural industry. It also stresses the report's relevance to the growing debate about the importance of green infrastructure, sustainable cities and urban climate adaptation. Lastly, it explores the potential contribution of the arboricultural industry to achieving the aims of Trees in Towns II and the promotion of green infrastructure and sustainable cities. © AB Academic Publishers 2010.

Slater D.,Myerscough College
Arboricultural Journal | Year: 2010

The branch attachment model set out by Alex Shigo in the Canadian Journal of Botany is 25 years old this year. Despite the model's wide use in arboricultural literature, it can be shown by simple logical argument to be erroneous. Ongoing investigations into the nature and strength of branch attachments at Myerscough College and the University of Manchester have highlighted the need for a new anatomical model for these attachments to inform research. Arguments against Shigo's model are given and a new model is offered that considers the mechanical and conducting functions of xylem and its ontogenesis. © AB Academic Publishers 2010.

Slater D.,Myerscough College | Ennos R.,Myerscough College
Arboricultural Journal | Year: 2016

Accelerometers are potentially a valuable tool in analysing the movement behaviour of trees and their component parts. Most previous research using similar tools has assessed the stability of tree stems and roots under wind loading, but accelerometers can assess a wider range of component parts of trees, associated defects and growth forms. In this study, the movement of sixteen bifurcations in semi-mature hazel trees (Corylus avellana L.) was assessed using triaxial accelerometers during seven differing wind loading events. Seven of the bifurcations were normally formed, with the other nine bifurcations containing bark inclusions, of which a subset of five were restricted by being in direct contact with neighbouring branches. Analysis of the acceleration data from the three windiest days showed that synchronised movement of the pairs of branches arising from the normally formed bifurcations reduced the potential acceleration of one branch away from the other by an average of 57.72%, whereas this reduction was found to be only 40.38% for the bark-included bifurcations. The data collected from this study indicate that normally formed bifurcations are not necessarily structural flaws in trees as the synchronised movement of the two branches of a bifurcation means they typically avoid damaging stresses occurring at the join under dynamic wind loading: the presence of rubbing or touching branches may, however, give rise to abnormal movement behaviour and heightened stresses. © 2016 Informa UK Limited, trading as Taylor & Francis Group and Arboricultural Association

Slater D.,Myerscough College | Ennos R.,University of Hull
Arboricultural Journal | Year: 2015

Xylem found in the stems of woody plants has contrasting strength in different planes due to its anisotropy. At the apex of the junctions of woody plant branches, sufficient wood strength is needed to prevent the arising branches splitting apart. The main aim of this research was to address an issue so far overlooked, which is the contribution of wood grain orientation and patterns at this location (the apex of such junctions) to supplying the required strength. In this study, the wood grain patterns of xylem produced at the apex of junctions of hazel (Corylus avellana L.) were investigated. The mechanical properties were determined using compression and tensile tests of excised wood samples with an Instron® Universal Testing Machine. Sample strength was contrasted with the strength of xylem produced at the side of the junctions and in the adjacent lower stems. Wood formed at the top of junctions in the hazel exhibited more tortuous wood grain patterns and had twice the radial and tangential tensile strength when compared with adjacent wood formed in the stem. It also had significantly higher radial and tangential compression strength. Density of xylem at the apex of hazel junctions was 13.4% greater than in the adjacent stem. The authors conclude that tortuous wood grain patterns supply additional strength to junctions in hazel trees. This mechanical arrangement should inform anatomical studies of junctions and may inform the design of manufactured Y-shaped components made from fibrous composite materials. © 2015 Taylor & Francis and Arboricultural Association.

Slater D.,Myerscough College
Arboricultural Journal | Year: 2016

The axiom of uniform stress is based on the theory that trees carry out their secondary growth in such a way that bending stresses are averaged out over the outer surfaces of the tree and the tree’s resulting aerial form avoids stress concentrations and repairs “notch stresses”. However, this can be shown, by combining a series of logical propositions, to be an errant or incomplete concept of how tree form develops, even in the limited scope of local stress levels that component parts of trees experience due to gravitational or dynamic wind loading. This paper presents an argument against the veracity of this axiom and highlights the extent of contradictory scientific work on the adaptive responses of trees to strain, their dynamic movement in the wind and the habit of some species to fail in a graduated way. It is concluded that a better model of the biomechanical behaviour of trees can be achieved through a synthesis of existing scientific models. © 2016 Taylor & Francis and Arboricultural Association

Puertolas J.,Lancaster University | Ballester C.,Instituto Valenciano Of Investigaciones Agrarias | Elphinstone E.D.,Myerscough College | Dodd I.C.,Lancaster University
Functional Plant Biology | Year: 2014

To test the hypothesis that root growth at depth is a key trait explaining some genotypic differences in drought tolerance in potato (Solanum tuberosum L.), two varieties (Horizon and Maris Piper) differing in drought tolerance were subjected to different irrigation regimes in pots in a glasshouse and in the field under a polytunnel. In the glasshouse, both cultivars showed similar gas exchange, leaf water potential, leaf xylem ABA concentration and shoot biomass independently of whether plants were grown under well watered or water deficit conditions. Under well watered conditions, root growth was three-fold higher in Horizon compared with Maris Piper, 3 weeks after emergence. Water deficit reduced this difference. In the polytunnel, applying 60% or less irrigation volume compared with full irrigation significantly decreased tuber yield in Maris Piper but not in Horizon. This was coincident with the higher root density of Horizon in deep soil layers (>40cm), where water content was stable. The results suggest that early vigorous root proliferation may be a useful selection trait for maintaining yield of potato under restricted irrigation or rainfall, because it rapidly secures access to water stored in deep soil layers. Although selecting for vigorous root growth may assist phenotyping screening for drought tolerance, these varieties may require particular environmental or cultural conditions to express root vigour, such as sufficiently deep soils or sufficient water shortly after emergence. © CSIRO 2014.

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