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Abstract

Tree roots often come in conflict with elements of the built environment, particularly when planted in limited soil locations. For street trees located between roadways and sidewalks, minimum planting width requirements can be calculated to prevent large supporting roots from lifting or growing over paved surfaces. In this study, we used diameter at breast height (DBH) to predict trunk flare diameter for common shade tree species from four different communities in the United States (Milwaukee, Minneapolis, Saint Paul, and Tampa). These predictive models were then used to calculate minimum width requirements to reduce infrastructure damage given the maximum expected DBH measurements for each species based on existing urban forest inventory data in the communities studied. For all ten taxa tested, DBH was a significant predictor of trunk flare diameter (minimum R2 = 0.81), indicating that this commonly used urban forestry measurement can be used to design minimum growing space based on selected species to potentially prevent root and infrastructure conflicts. The methods employed in this paper can be easily replicated by other researchers in order to create guidelines for species and environments not captured in our data set. Alternatively, broader functions for estimating trunk flare based on DBH are provided for species based on natural habitat type (i.e., upland, wetland, variable).

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... Root and hardscape conflicts can be similarly damaging to the trees involved. The replacement or repair of paved surfaces near trees can sever or injure roots -reducing tree health (Benson et al., 2019;Hauer et al, 2020;Koeser et al., 2013) and undermining overall stability in the face of storm events (Johnson et al., 2019). To reduce root and hardscape conflicts, researchers have investigated how planting widths relate to sidewalk damage (Francis et al., 1996;Randrup et al., 2003) and created allometric models to predict trunk flare (i.e., the enlarged area at the base of the tree where the trunk connects to the main structural roots) diameter based on tree species and stem diameter (Hilbert et al., 2020;North et al., 2015). ...
... The replacement or repair of paved surfaces near trees can sever or injure roots -reducing tree health (Benson et al., 2019;Hauer et al, 2020;Koeser et al., 2013) and undermining overall stability in the face of storm events (Johnson et al., 2019). To reduce root and hardscape conflicts, researchers have investigated how planting widths relate to sidewalk damage (Francis et al., 1996;Randrup et al., 2003) and created allometric models to predict trunk flare (i.e., the enlarged area at the base of the tree where the trunk connects to the main structural roots) diameter based on tree species and stem diameter (Hilbert et al., 2020;North et al., 2015). ...
... In this extension of past research by North et al. (2015) and Hilbert et al (2020), we developed allometric models linking stem diameter to trunk flare diameter in small-stature urban trees. While the large stature shade trees assessed by the two research teams cited above are important contributors of ecosystem services, modern compact development patterns leave less space for the sustained growth of large trees (Daniel et al. 2016). ...
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Research Highlights: • Allometric equations explain minimum planting widths for small stature trees. • Trunk flare diameter is related to species, stem diameter, and measurement height • Cost savings for increased planting widths were created for sidewalk replacement. • Minimum planting width provided for planners, urban foresters, and engineers. Abstract As urban development increases in density, the space to grow urban trees becomes more constrained. In heavily developed areas, small stature trees can be planted to reduce both above-and below-ground conflicts with infrastructure elements. However, even these species have their limits when placed in extremely confining conditions. In this study, we build on past work to determine the minimum planting widths of small stature urban trees. We found that species, stem diameter, and the height at which stem diameter measurements occurred were all strong predictors of trunk flare diameter (adjusted R 2 of 0.843). Additionally, we modelled the relationship between planting space and the presence or absence of hardscape conflicts-using the predictions derived from this effort to project the potential cost savings in two United States cities. Study results provide a guideline to create sufficient space for urban trees and minimize infrastructure damage and associated cost savings.
... Some attributes have recently been incorporated into urban soil quality indexes (Schindelbeck et al. 2008;Scharenbroch et al. 2017). The critical issues on tree growth include soil structure, aggregate stability, compaction, bulk density, porosity, soil-volume restriction, soil sealing, and limited rooting volume with collateral restrictions of low nutrient and water availability (Trowbridge and Bassuk 2004;Hilbert et al. 2020). However, they have remained neglected in urban soil management (Jim 2019). ...
... Poor-quality soil at difficult sites is compounded by restrictive soil volume and surface sealing by impermeable paving materials (Koeser et al. 2013;North et al. 2015;Hilbert et al. 2020;Ugolini et al. 2020). The frequent occurrence of tree roots damaging the infrastructure highlights the shortage of rootable soil volume (Day 1991;Randrup et al. 2001;Day et al. 2010a). ...
... Type 2 Contiguous strip expansion envisages the original tree-planting strip's (Type 2a) elongation, widening, or enlargement (2b, 2c, and 2d, respectively). The planting-site width has an essential bearing on tree performance (North et al. 2017;Hilbert et al. 2020), and the tree strip is regarded as the best roadside tree planting site if wider than 1 m (Duinker et al. 2017). For both pits and strips, the proposed soil volume can be increased by two to nine times. ...
Article
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Aims Cramped and sealed sites common in compact city areas limit tree growth due to multiple physical restrictions and physiological stresses. Fast urbanization and densification have intensified the pressure on urban trees, demanding innovative methods and solutions. The subaerial tree-growth space attracts more attention, but the more intractable subterranean rootability constraints are often overlooked. They are expressed as external (macro-scale) soil-body volume and internal (micro-scale) soil-pore volume limitations. The double jeopardy of urban soil insularity acutely restricts root growth, root spread, tree health, and stability. Methods Some novel solutions can be distilled from a comprehensive review of recent research findings to bring effective relief. Results Pedestrians and vehicles can co-use the expanded soil area in dense urban areas. Various creative soil expansion techniques can allow tree roots to break out from conventional confined tree pits or tree strips. Subsurface connections can link a planting site to an adjacent one or a nearby green patch. The soil union could be realized by subsurface soil conduits (large-diameter buried pipes) or subsurface soil corridors covered by pier-supported paving. In the spirit of landscape altruism, soil sharing by neighbor trees optimizes using the scarce rootable soil resource. Internal soil volume expansion can be accompanied by high-quality soil mix and compaction-prevention measures to resolve porosity and rootability deficit. Conclusions Urban tree managers can adopt out-of-the-box thinking in managing critical physical soil deficiencies. New research findings can more promptly inform policymakers and practitioners. Close interactions between science and practice can be proactively cultivated.
... It helps to overcome the harmful ideas about trees and avoid problems due to tree growth on inadequate sites in cities. In the planning process regarding different types of urban green infrastructures that compose the urban forest, the management of the space available to trees on sidewalks and the interaction with urban infrastructures is one of the main challenges faced by public managers [8,12,13]. ...
... The space occupied by a tree at the ground level depends on the size of its trunk flare diameter (TFD), the region where the topmost roots connect to the trunk right in the above-ground portion [13]. As trees grow, the TFD becomes larger due to mechanical responses to the static load (tree structure weight) and dynamic load (wind drag forces) that influence trees growing in isolation [8,14,15]. ...
... Problems regarding sidewalk breakage and conflicts with accessibility have been reported by some studies on urban trees [2,12,13,16] and in most cases, it is due to the natural trunk flare growth in an inadequate space to the tree on the sidewalk. In some places, pavement removal around the trunk flare can be a solution, but the best thing is to promote a qualified planning process, giving trees appropriate space for their growth over the years after planting [8,13]. ...
Article
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The rule of thumb “the right tree in the right place” is a common idea in different countries to avoid damages caused by trees on sidewalks. Although many new planting techniques can be used, the estimation of the trunk flare diameter (TFD) could help the planning process to give tree roots more space to grow over the years. As such, we compared the applicability of point clouds based on iPad Pro 2020 image processing and a precise terrestrial laser scanner (TLS FARO) for the modeling of the TFD using different modeling procedures. For both scanning methods, 100 open-grown and mature trees of 10 different species were scanned in an urban park in Cracow, Poland. To generate models, we used the PBH (perimeter at breast height) and TFD variables and simple linear regression procedures. We also tested machine learning algorithms. In general, the TFD value corresponded to two times the size of a given DBH (diameter at breast height) for both methods of point cloud acquisition. Linearized models showed similar statistics to machine learning techniques. The random forest algorithm showed the best fit for the TFD estimation, R2 = 0.8780 (iPad Pro), 0.8961 (TLS FARO), RMSE (m) = 0.0872 (iPad Pro), 0.0702 (TLS FARO). Point clouds generated from iPad Pro imageries (matching approach) promoted similar results as TLS FARO for the TFD estimations
... Flares stemming from a trunk tapering near the ground can be quantified by trunk flare diameter (TFD), which is predictable by diameter at breast height (DBH). In order to avoid pavement damage, minimal open soil surface area could be determined according to predicted TFD values (North et al. 2015;Hilbert et al. 2020). Hilbert et al. (2020) also regressed the occurrence of pavement damage on dendrometric and habitat variables. ...
... In order to avoid pavement damage, minimal open soil surface area could be determined according to predicted TFD values (North et al. 2015;Hilbert et al. 2020). Hilbert et al. (2020) also regressed the occurrence of pavement damage on dendrometric and habitat variables. However, in their model, the classification of possible damages was lacking. ...
... DBH, H, and lean angle functioned as dendrometric factors, whereas pavement width, open soil area, setback, and pavement material were classified as habitat factors. Following Hilbert et al. (2020), the unit of measure used for DBH was centimetres, so that odds ratio values could be more easily interpreted. Model statistics (Χ 2 ), pseudo R 2 , and prediction accuracy values (Yes% and No%) were presented, followed by the effect of each factor on the odds ratio of the 3 scenarios. ...
Article
Background: Tree pits are urban green infrastructures in paved areas. But tree roots and flares, especially of larger trees, may come into conflict with pavement, resulting in tree health decline and repair costs. This study aimed to (1) establish allometric relationships between diameter at breast height (DBH) and trunk flare diameter (TFD) of common urban tree species, and (2) identify factors affecting the presence and magnitude of protruding roots and flares. Methods: The terms “protruding roots” and “protruding flares” were strictly defined as roots and flares reaching or exceeding the border between the open soil and the adjacent paving material. The study surveyed 1,100 trees of 14 species planted in tree pits in Chai Wan, Hong Kong. Results: DBH was a significant predictor of TFD but was less significant when trees with protruding roots or flares were considered separately. In most logistic models, DBH was significantly and positively related to the odds ratio of the occurrence of protruding roots and flares. Overall, a centimetre increase in DBH brought 1.049 to 1.114 times higher likelihood of protruding roots and flares. Multiple regression suggested that for every square-metre increase in the open soil area in tree pits, the maximum length of protruding roots and flares increased by 0.154 to 0.172 m. This relationship could be attributed to the underlying association between DBH and open soil area. Species-specific regression results were tabulated to allow more accurate estimation of protruding roots and flares. Conclusion: For urban planners and pavement engineers, the approach recommended in this study could be adopted to optimise urban greening and pavement design.
... The replacement or repair of paved surfaces near trees can sever or injure roots, reducing tree health [11][12][13] and undermining overall stability in the face of storm events [14]. To reduce root and pavement conflicts, researchers have investigated how planting widths relate to sidewalk damage [9,15] and created allometric models to predict trunk flare diameter (TFD; i.e., the diameter of the enlarged area at the base of the tree where the trunk connects to the main structural roots) based on tree species and stem diameter [16,17]. From these efforts, minimum planting width requirements can be estimated given species and growth potential to limit root and sidewalk or curb conflicts ( Figure 1). ...
... In this extension of past research by North et al. [17] and Hilbert et al. [16], we developed allometric models linking stem diameter to TFD in small-stature urban trees. While the large stature shade trees assessed by the two research teams cited above are important contributors of ecosystem services, modern compact development patterns leave less space for the sustained growth of large trees [18]. ...
... We worked with local urban foresters to locate and measure small stature urban trees in Lakeland (28.0395 Trunk flare circumference was determined using the method of Hilbert et al. [16]. In brief, marking flags delineated points at the base of the tree where the root-stem transition zone transitioned to root tissue. ...
Article
Full-text available
As urban development increases in density, the space to grow urban trees becomes more constrained. In heavily developed areas, small stature trees can be planted to reduce both above- and below-ground conflicts with infrastructure elements. However, even these species can interfere with pavement when placed in extremely confining conditions. In this study, we build on past work to determine the minimum planting space widths of small stature urban trees. Species, stem diameter, and the height at which stem diameter measurements occurred were all strong predictors of trunk flare (i.e., the interface region between large structural roots and the trunk) diameter (adjusted R2 of 0.843). Additionally, we modelled the relationship between planting space and the presence or absence of pavement conflicts using the predictions derived from this effort to project the potential cost savings in two United States cities. Study results provide a guideline to create sufficient space for urban trees and minimize infrastructure damage and associated cost savings.
... Mature trees with well-developed root systems (North et al., 2015) within constrained planting areas (Watson et al., 2014;Hilbert et al., 2020b) are therefore more likely to lead to surface displacement. ...
... Whilst recent studies have modelled the more complex interactions between roots and footpaths using computational software (Giuliani et al., 2017;Grabosky and Gucunski, 2019), field investigations to date have examined these interactions using qualitative observational outputs (e.g., whether damage to the footpath has occurred), in an attempt to identify causal factors in infrastructure damage. Planting space (Wong et al., 1988;Hilbert et al., 2020a) and trunk diameter (Francis et al., 1996;Hilbert et al., 2020b) are the most common factors which are positively implicated in the damage, but soil characteristics (McPherson, 2000) and species (Wager and Barker, 1983;Wong et al., 1988;Day, 1991) have also been shown to influence footpath displacement. ...
... The statistical analyses revealed that D 30 was significant in all models (Table 1), which supports recent findings by other researchers, where in larger trees are more likely to cause damage to hard surfaces (Hilbert et al., 2020b). Furthermore, the distance between the tree and the footpath / scan, either directly or in terms of D 30 , was significant in varying combinations for each of the POS, NEG or TOT displacement models (Table 1). ...
Article
It is well-accepted that urban trees provide many benefits to society, but there are costs associated with their establishment and maintenance. Some indirect costs of juxtaposing trees with urban infrastructure are linked to the way in which tree roots interact with hard surfaces such as footpaths (sidewalks), which can result in expensive repairs and in some instances, tree removal. There is a need to understand the complex interactions between tree roots and infrastructure, to inform strategic planting and balance the needs of all stakeholders. In this short communication, we introduce a simple, cost-effective method for quantifying footpath displacement using Arduino robotics and provide the schematics and coding as an open-source tool. Using an ultrasonic sensor, the robot generates a 2.1 m long, two-dimensional profile of a given surface. The accuracy of the robot is validated with objects of known size and was subsequently field tested using 15 Liquidambar styraciflua growing in a suburban street. The robot allowed us to quantify the maximum (highest vertical point) and total (the area under the curve) displacements in the footpath surface. Trunk diameter and proximity to the footpath were significant predictors of displacement at P < 0.05, supporting the findings of other researchers. A larger dataset is required for more generalisable results, but the robot produced reliable data in this proof-of-concept field test.
... A arborização promove serviços sociais e ambientais para o bem-estar humano, como melhorias estéticas, sombreamento, direcionamento de vento, redução de poluições atmosférica, sonora e visual, estímulo a atividades recreativas, alimento e abrigo para a fauna, conectividade entre paisagens e atenuação de ilhas de calor [2,3]. Todavia, a arborização de cidades é uma prática que requer eficiente planejamento e gerenciamento para se evitar prejuízos advindos do crescimento não monitorado de árvores, como danos em calçadas, tubulações subterrâneas, edifícios e redes elétricas [4]. A escolha de espécies deve considerar caraterísticas de crescimento, paisagísticas e inerentes ao local de plantio, como a disponibilidade de espaço. ...
... O avanço de recursos computacionais tem propiciado o uso de modelos de regressão não lineares e inteligência computacional. A modelagem permite a compreensão indireta de como interações e processos ecológicos complexos atuam no crescimento de árvores isoladas ou arvoredos, estabelecendo relações funcionais entre aspectos morfométricos e preditores de fácil e rápida medição, como a circunferência ou diâmetro de fustes [4]. Curvas sigmoidais (forma em S) subsidiam o estabelecimento de prescrições silviculturais e a avaliação de capacidade produtiva, que pode ser expressa em termos de altura, área de projeção da copa, diâmetro da copa e/ou volume [12,13,14]. ...
Article
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IInvestigações científicas sobre a morfometria de árvores subsidiam o planejamento e gerenciamento racionais da arborização urbana, importante para a sustentabilidade ambiental de cidades. O objetivo foi avaliar a eficiência da modelagem de relações morfométricas interdimensionais da copa de L. tomentosa empregando regressão logística e Máquinas Vetor de Suporte (MVS), identificando potenciais usos no planejamento da arborização urbana. O inventário foi conduzido nos municípios de São João Evangelista e Peçanha em Minas Gerais. Foram amostradas 116 árvores em 21 vias públicas. Calcularam-se o formal de copa, índice de saliência, índice de abrangência, grau de esbeltez, proporção de copa e área de projeção de copa. Foram testados dois métodos de modelagem para a estimativa de altura total, altura de inserção da copa e índices morfométricos de copa (r, p ≤ 0,01) em função exclusivamente do DAP, uma por regressão não linear (modelo logístico) e outra por MVS. A altura total, altura de inserção da copa, formal de copa, índice de abrangência e área de projeção de copa aumentaram à medida que fustes se tornaram mais grossos. O decrescimento com o aumento do DAP foi observado somente para o grau de esbeltez. Relações morfométricas podem ser estimadas com precisão por modelos de regressão e MVS. Informações da média assintótica do estoque de crescimento de L. tomentosa em altura total, altura de inserção da copa, área de projeção da copa e raio de copa são úteis para a definição do local de seu plantio em áreas urbanas, indicado para praças, canteiros e/ou calçadões.
... Consistent with other reviews in urban forestry [48,61], the greatest amount of street tree studies over time has taken place in North America (total n = 197) ( Figure 2)-particularly the United States (total n = 166). Research from other continents has been rising in recent years, with a notable increase in Europe and Asia after 2010. ...
... Survival and Mortality. In contrast to urban street tree establishment and growth, urban tree survival is defined as the cumulative factors that contribute to the health and longevity of urban trees [72], whereas urban tree mortality factors are those contributing to the death and premature removal of a tree [61]. Of the biophysical factors, taxa, age, and site conditions were most commonly researched [73]. ...
Article
Full-text available
Street trees are components of the urban forest that receive considerable attention across academic and professional disciplines. They are also one of the most common types of urban tree that people routinely encounter. A systematic review methodology was used to examine contemporary urban street tree research across natural and social science disciplines. The records collected (n = 429) were published between January 1997 and the mid-2020s and were coded for descriptive information (e.g., publishing journal and geography of study areas) as well as emergent focal research areas (e.g., ecosystem services, economic valuation, and inventory methods). From this sample, there has been considerable growth in street tree literature over time and across research themes, especially following major turning points in the field of urban forestry. Regulating ecosystem functions/services of street trees, especially cooling, has had the greatest attention in the literature, but other robust areas of research also exist, including the utility of pruning waste as construction materials, the benefits and disservices to human health and safety, and indicators of environmental (in)justice. Opportunities for future research and implications for research and practice are also discussed.
... For this, we recommend long-term monitoring of tree performance and growth using standardised metrics (McPherson et al., 2016;van Doorn et al., 2020). These data should be linked to local climatic conditions by incorporating climate information (e.g. annual precipitation, mean annual temperature, maximum temperature) into the database Limited growing space for established trees Inappropriate site conditions for current and future shoot and root growth increases the probability of tree failure (Hauer, Hanou, & Sivyer, 2020;Hauer, Koeser, et al., 2020;Hilbert et al., 2020;Jahani, 2017;Jahani, 2019) Observe standard planting distances from urban structures and create proper soil rooting volume based on species' requirements before planting trees can help prevent tree failure. Develop and follow planting protocols considering species growth requirements Assess tree growth through (1) visual inspection to detect issues, symptoms and evaluate vitality; (2) when an issue is detected, further examination is required to confirm its nature; and (3) when the defect is confirmed and may represent a risk, it should be measured, recorded and recommendations made for corresponding actions, which may include tree removal Pests and diseases Pest and diseases may reduce tree growth and increase mortality. ...
... Poor site conditions Poor site conditions, such as soil compaction, limited rooting volume and low nutrient availability can affect performance and reduce survival (Hilbert et al., 2020;Trowbridge & Bassuk, 2004) Prior to planting, assess soil characteristics by determining pH, compaction, texture, water availability and nutrient status, among others, based on regional planting protocols. Sites with suboptimal conditions can be improved to meet standard planting conditions by identifying appropriate substrates, applying fertilisers and other amendments to enhance establishment and survival (Pauleit et al., 2002) ...
Article
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The management of urban forests is a key element of resilience planning in cities across the globe. Urban forests provide ecosystem services as well as other nature based solutions to 4.2 billion people living in cities. However, to continue to do so effectively, urban forests need to be able to thrive in an increasingly changing climate. Trees in cities are vulnerable to extreme heat and drought events, which are predicted to increase in frequency and severity under climate change. Knowledge of species' vulnerability to climate change, therefore, is crucial to ensure provision of desired ecosystem benefits, improve species selection, maintain tree growth and reduce tree mortality, dieback and stress in urban forests. Yet, systematic assessments of causes of tree dieback and mortality in urban environments are rare. We reviewed the state of knowledge of tree mortality in urban forests globally, finding very few frameworks that enable detection of climate change impacts on urban forests and no long-term studies assessing climate change as a direct driver of urban tree dieback and mortality. The effects of climate change on urban forests remain poorly understood and quantified, constraining the ability of governments to incorporate climate change resilience into urban forestry planning.
... Determining the optimal one among such an array of data is a rather serious and difficult task. which can be solved only with the use of computers, and modern mathematical methods, taking into account many factors [7][8][9][10]. ...
Article
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Stem wood, obtained from the cuttings of care in low-forest areas is of low quality. Such wood has a number of vices, one of which is simple curvature, which has impact on the voluminous and commercial output of round timber. Reducing this influence can be achieved through high-quality bucking. Therefore, the purpose of the work presented is to increase the volume and commercial output of round timber harvested in low-forest areas. The developed technique using computers allows to solve the tasks of modeling the shape of wood whips and logs using multi-critical optimization and bucking whips having curvature. The use of the proposed technique allows for results adequate to the real production conditions, as evidenced by the methods of decision-making used. Scientific research and theoretical developments, taking into account the formed database, allowed to search for the optimal scheme of cutting when bucking round timber, performed according to the algorithm based on the busting of acceptable variants using modern theory of graphs and matrixes. As a result, the developed program will reduce the time for data formation, guarantee the accuracy of the results, the program easily adapts to natural and production conditions and will expand the possibilities for Computer-aided design.
... and subsequent work by Wagar and Barker [123], Francis et al. [124], McManus and Brown [125], Randrup, McPherson and Costello [120], O'Malley and Cameron[121], Lucke and Beecham[126], Johnson et al.[127] and Hilbert et al.[128] are summarized here: ...
Article
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Kerb is an integral part of road infrastructure and performs several important functions, including providing stability to the edges of the road and providing effective drainage. Their performance can significantly influence the behaviour and service life of a road. The design conditions, construction materials and their sustainability can be important to assess from an asset management and sustainable construction point of view even though this area has been paid limited research attention in the past. This paper reviews the available literature on the design and construction considerations for kerbs and critically analyses them with a special focus on sustainable construction practice. The different materials commonly used around the world for the construction of kerb in terms of their properties, failure and available design guidelines have been discussed along with their management practice. Special situations, such as expansive soil movement and tree root-related problems, have also been considered, and the current guidelines for designing in such situations have also been discussed. A carbon footprint and sustainability analysis has been conducted on the current practice of using natural aggregate concrete and compared against several potential alternatives. The review of the design process indicated that the current practice relies on over-simplified design procedures and identified scopes for improvement, especially with the incorporation of mechanical behaviour of the material being used in construction. The carbon footprint and sustainability analysis indicated that the use of alternative materials could result in significant savings in the kerb construction industry’s carbon footprint.
... Large stature trees provide the greatest level of benefit and can have an outsized impact on a municipality's canopy coverage. However, they also require more above-and below-ground space if they are to grow anywhere near their genetic potential for a given site (Hilbert et al., 2020). As such, zoning which allows for higher density housing development can significantly limit the potential for urban tree canopy in new neighborhoods. ...
Article
Many cities actively manage their urban trees in an effort to increase canopy coverage, manipulate species and size distributions, and maximize associated environmental and social benefits. As development is one of the most significant factors limiting tree abundance and health, many local governments have enacted policies or ordinances which attempt to reduce tree loss during construction activities through preservation or replacement requirements. Recently, the state of Florida passed a state statute which significantly limits local government oversight of trees on private residential properties-a land use type which can often account for the majority of a municipality's urban forest. In this study, we accessed ordinance databases to assess the potential impact of this law on urban forest governance in Florida's 300 largest cities (by population). We also surveyed urban tree managers in the largest 150 cities to assess the range of strategies being developed to function under this new political normal. Ordinances that regulate the removal of urban trees were the most likely to be impacted by the new state legislature and were in place in 46% of the communities assessed. Despite this, very few responding cities had changed their ordinances to comply with the new statute-though several indicated such changes were in progress. Other changes in policies and ordinances ranged from maintaining business as usual to actually investing more into urban forest management through increased inventory and management plan activities.
... While a useful measure in its own regard, tree diameter can also be used to predict other indicators such as tree growth, canopy spread, trunk flare, and tree height (McPherson et al., 2016b;Hilbert et al., 2020). Tree species, condition, insect/disease conditions, and maintenance requirements are also regularly collected (Hauer and Peterson, 2017). ...
Article
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While efforts to standardize urban forest inventory data have occurred, the information collected from community to community remains quite variable. In this study, we conducted a global review of peer-reviewed and published research that collected tree inventory data to assess what information is being collected. In addition to this review, we also present results from national surveys conducted in the United States and Sweden that specifically asked urban forest managers about how their inventories informed their urban forest management efforts. In the literature review, tree species and stem diameter were the most collected structural parameters and planning and estimation of ecological services were the most common research objectives. The surveys conducted in Sweden and the USA found communities commonly collected records about tree species, diameter, and condition and that inventories were more common as community size increased. Street and park tree inventories were the most common inventories. Inventories of public trees on greenbelts and woodlots were less common and private tree inventories were relatively uncommon. Additionally, professional staff and consultants were more likely to collect inventory data than interns and volunteers in both countries. Despite these similarities, significant differences exist between the USA and Sweden, with several parameters (i.e., adoption a management plan, presence of an inventory, collection of inventory data digitally, collection of tree planting/removal records) being more common in the USA-possibly reflecting a longer history of urban tree management in the latter country. In modelling the survey results from Sweden and the USA, we found that having a strategic plan, a governance mechanism (tree board), financial resources (per capita budget), and the adoption of greater systematic care of trees were significant predictors the presence of an inventory. Study results also suggest that having a tree inventory reflects the advancement of an urban forestry program along a continuum of initial program adoption to more fully developed and sustained urban forestry program.
... This finding is consistent with Tate (1980Tate ( , 1981b who also found no relationship between tree lawn width and girdling root development. Regardless, space to grow street trees is important and a predictor for tree health Hilbert et al., 2020). ...
Article
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 to 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.
... Then we plugged those DBH values into a series of equations from our abovementioned research to calculate these species' TFDs. To determine recommended planting space, we added 4 feet of buffer to either side of the trunk flare to account for large supportive roots that (while hidden below the soil surface) could still lift or crack sidewalks (Hauer et al. 2020;Johnson & North 2016;Perry 1992). The figures below help explain this. ...
Article
Trees provide urban landscapes with shade, beauty, and habitat. They can also help lessen the effects of flooding and urban heat buildup while storing carbon dioxide, a major greenhouse gas. When planted in the wrong place, however, trees can damage urban infrastructure. To maximize the benefits provided by urban trees, we need better-informed tree selection and larger planting spaces with the capacity to support big-canopy trees. This new 8-page fact sheet is intended to help arborists, urban foresters, landscape designers, landscapers, and anyone else responsible for the planting of trees in developed areas make informed decisions regarding the planting width requirements of the trees they select. Written by Deborah R. Hilbert, Andrew K. Koeser, Brooke L. Moffis, JuWanda G. Rowell, and Drew C. McLean, and published by the UF/IFAS Environmental Horticulture Department.https://edis.ifas.ufl.edu/ep592
... Then we plugged those DBH values into a series of equations from our abovementioned research to calculate these species' TFDs. To determine recommended planting space, we added 4 feet of buffer to either side of the trunk flare to account for large supportive roots that (while hidden below the soil surface) could still lift or crack sidewalks (Hauer et al. 2020;Johnson & North 2016;Perry 1992). The figures below help explain this. ...
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Describes a method for determining planting width requirements for urban trees to prevent damage to nearby infrastructure like curbs and sidewalks. Includes tables with values for species common to Florida as well as general equations that can be used for a wider range of species in North America and beyond.
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Logarithmic regression equations were developed to predict leaf area and leaf biomass for open-grown deciduous urban trees based on stem diameter and crown parameters. Equations based on crown parameters produced more reliable estimates. The equations can be used to help quantify forest structure and functions, particularly in urbanizing and urban/suburban areas. For. Sci. 42(4):504-507.
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Literature relevant to tree root and urban infrastructure conflicts is reviewed. Although tree roots can conflict with many infrastructure elements, sidewalk and curb conflicts are the focus of this review. Construction protocols, urban soils, root growth, and causal factors (soil conditions, limited planting space, tree size, variation in root architecture, management practices, and construction materials) are discussed. Because costs related to sidewalk and curb damage are substantial, a review of research addressing repair, mitigation, prevention, and litigation costs is included. Finally, future research needs are discussed. Potential for conflicts between trees and sidewalks/curbs is high when one or more of these factors are present: tree species that are large at maturity, fast growing trees, trees planted in restricted soil volumes, shallow top soil (hard-pan underneath top-soil), shallow foundations underneath the sidewalk (limited or no base materials), shallow irrigation, distances between the tree and sidewalk of less than 2.0–3.0 m., trees greater than 15 to 20 years old. The results of this survey indicate that cities are spending substantial sums of money to address conflicts between street tree roots and infrastructure. It can be inferred that most of these expenditures are spent dealing with problems that already exist. However, this raises the question: How much is being spent now to ensure that conflicts are minimized in the future? Future research should concentrate on plant factors, site design, and construction of sidewalks and curbs. Also, more knowledge is needed about interactions between root growth and management techniques, such as pruning and irrigation. Finally, there is need for studies that will assist policy-makers to efficiently allocate funds among repair, mitigation, prevention, and legal remedies.
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Results of the 3-year Chicago Urban Forest Climate Project indicate that there are an estimated 50.8 million trees in the Chicago area of Cook and DuPage Counties; 66 percent of these trees rated in good or excellent condition. During 1991, trees in the Chicago area removed an estimated 6,145 tons of air pollutants, providing air cleansing valued at $9.2 million dollars, These trees also sequester approximately 155,000 tons of carbon per year, and provide residential heating and cooling energy savings that, in turn, reduce carbon emissions from power plants by about 12,600 tons annually. Shade, lower summer air temperatures, and a reduction in windspeed associated with increasing tree cover by 10 percent can lower total heating and cooling energy use by 5 to 10 percent annually ($50 to $90 per dwelling unit). The projected net present value of investment in planting and care of 95,000 trees in Chicago is $38 million ($402 per planted tree), indicating that the long-term benefits of trees are more than twice their costs. Policy and program opportunities to strengthen the connection between city residents and city trees are presented.
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Urban ecosystems are often characterized as hostile environments for tree growth due to high level of human interference. For this study, 320 established healthy open-crown trees were sampled according to community population gradients (approximately 0, 500, 5,000, and 50,000 people) and by land uses (city parks, residential, and commercial sites) in 5 Midwestern states. The first objective was to examine variation in age, height, diameter, growth rates, and condition rating. The second objective was to examine variation in number of competitors within 20 m and 9 m, and assess their relationship to growth according to community populations and land uses. The third objective was to evaluate the relationship of biotic and abiotic factors to tree growth. Tree growth rate was defined as the mean annual ring width averaged over the last 10 years (mm year⁻¹). Number of competitors within 20 m and the location of anthropogenic features were noted for each sample tree. Six biotic factors and seven abiotic factors were recorded for all sampled trees; for the Iowa-2 samples four additional abiotic variables were included. According to community population gradient, rural parks had higher mean age, and lower mean growth rates compared to all communities. According to land use, both mean age and mean growth rates were higher for city parks compared to commercial sites; residential sites had intermediate age, size, and growth rate characteristics. According to community population gradient, mean number of competitors (20 m) was higher in rural parks, associated with lower growth rates. According to land use, city parks and residential sites had more competitors, with no relationship to growth rates. Trees that had no competitors within 9 m had higher mean growth rates compared to those with more than one competitor. Combined biotic factors were related to tree growth rates for all species and silver maple in all studied areas, while abiotic factors were related to growth in the Iowa-2 samples. In conclusion, both community population gradient and land use were related to tree characteristics. Number of competitors and number of biotic and abiotic factors were also related to tree growth. Typescript (photocopy). Thesis (M.S.)--Iowa State University, 2001. Includes bibliographical references.
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Root-pavement conflicts are a common challenge in urban forest management. Given the expense of pavement installation and the time needed to develop large trees, there is a preference for modelling design solutions to integrate trees and pavement with shared soil volumes. While Finite Element (FE) models are used in pavement analysis and design, and have been used to describe root growth in soils, there are few examples exploring of integration of the two applications with respect to designing urban root zones under pavements. Four series of FE models were developed to test the influence of an asphaltic concrete wearing surface layer thickness and base layer thickness (the top two layers in a pavement design) in surface crack formation from a growing tree root simulation in positions within the top zone of the base layer and below the base layer. The expected pavement damage was defined at places where horizontal tensile stresses exceeded 862 kPa. The testing series were developed from a common group of 18 FE pavement layer configurations using 3 asphalt concrete (AC) thicknesses and 3 granular base thicknesses with a growing root element at 2 root elevations. In the first series, an AC layer of a thickness of 7.6 cm did not exceed the horizontal stresses needed to develop a crack when a simulated root element increased from 3.6 to 5.1 cm when the root element was below the base layer at least 10.16 cm below the bottom of the AC layer. A second series of 77 model runs with a refined root simulation verified the impact of a changed root simulation (shift of element shape with a material modeling change that accounted for soil hardening during deformation). For the second series, a 2.54 cm diameter circular root was expanded to a final size ranging from 3.8 to 10.16 cm. Results of the second series confirmed and added detail to the first, but required a significant increase in computational time to accommodate the added model and data output details. The third series developed root simulations from an initial 0.508 cm diameter (the smallest diameter available in the PLAXIS FEM modeling platform) to a maximum 5.08 cm diameter in a series of 55 tests. The third set allowed a method to observe and compare the colonization step to a series of radial growth steps, which caused minimal influence to the stress state of the AC as a consequence of soil displacements from the root growth. Finally, in the fourth testing series of 58 simulations, we tested a cluster of three root elements at a 10.16 cm spacing 0.635 cm below the AC or the base layer, growing from an initial 2.54 cm to 6.35 cm diameter. Modeling three root elements at the 10.16 cm spacing generated tensile stress-induced cracks in all AC-base-root depth configurations. Displacements in those models exceeded the imposed upward displacement limit of 1.27 cm after doubling in size from an initial 2.54 cm diameter.
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Urban impervious surfaces convert precipitation to stormwater runoff, which causes water quality and quantity problems. While traditional stormwater management has relied on gray infrastructure such as piped conveyances to collect and convey stormwater to wastewater treatment facilities or into surface waters, cities are exploring green infrastructure to manage stormwater at its source. Decentralized green infrastructure leverages the capabilities of soil and vegetation to infiltrate, redistribute, and otherwise store stormwater volume, with the potential to realize ancillary environmental, social, and economic benefits. To date, green infrastructure science and practice have largely focused on infiltration-based technologies that include rain gardens, bioswales, and permeable pavements. However, a narrow focus on infiltration overlooks other losses from the hydrologic cycle, and we propose that arboriculture – the cultivation of trees and other woody plants – deserves additional consideration as a stormwater control measure. Trees interact with the urban hydrologic cycle by intercepting incoming precipitation, removing water from the soil via transpiration, enhancing infiltration, and bolstering the performance of other green infrastructure technologies. However, many of these interactions are inadequately understood, particularly at spatial and temporal scales relevant to stormwater management. As such, the reliable use of trees for stormwater control depends on improved understanding of how and to what extent trees interact with stormwater, and the context-specific consideration of optimal arboricultural practices and institutional frameworks to maximize the stormwater benefits trees can provide.
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Urban forest research and management requires improved methods for quantifying ecosystem structure and function. Regional equations for urban tree crown width and height can accordingly improve predictions of urban tree structure. Using a large regional dataset with 12 locations in the southeastern US, we developed diameter-based equations for 97 urban tree species. Whereas previously published urban equations have almost exclusively been developed with one location on public or commercial land, our data included both public and private land uses. For 5 widespread, common urban tree species (Acer rubrum, Cornus florida, Pinus taeda, Quercus nigra and Lagerstroemia spp.), we also assessed the inclusion of additional variables such as crown light exposure, land cover, basal area, and location. Overall, height and crown width models were improved when including additional predictors, although competition and location effects varied by species. Study city was a significant predictor of tree height in all species except C. florida, and a significant predictor of crown width for all species except C. florida and Q. nigra. This indicates that anthropogenically-influenced variation among cities can lead to significant differences in both tree form and structure and that future model development should utilize data encompassing multiple cities. Our predictive equations for urban tree crown characteristics provide an improved method for planning, management, and estimating the provision of ecosystem services to improve quality of life in cities.
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Many environmental challenges are exacerbated within the urban landscape, such as stormwater runoff and flood risk, chemical and particulate pollution of urban air, soil and water, the urban heat island, and summer heat waves. Urban trees, and the urban forest as a whole, can be managed to have an impact on the urban water, heat, carbon and pollution cycles. However, there is an increasing need for empirical evidence as to the magnitude of the impacts, both beneficial and adverse, that urban trees can provide and the role that climatic region and built landscape circumstance play in modifying those impacts. This special section presents new research that advances our knowledge of the ecological and environmental services provided by the urban forest. The 14 studies included provide a global perspective on the role of trees in towns and cities from five continents. Some studies provide evidence for the cooling benefit of the local microclimate in urban green space with and without trees. Other studies focus solely on the cooling benefit of urban tree transpiration at a mesoscale or on cooling from canopy shade at a street and pedestrian scale. Other studies are concerned with tree species differences in canopy interception of rainfall, water uptake from biofilter systems, and water quality improvements through nutrient uptake from stormwater runoff. Research reported here also considers both the positive and the negative impacts of trees on air quality, through the role of trees in removing air pollutants such as ozone as well as in releasing potentially harmful volatile organic compounds and allergenic particulates. A transdisciplinary framework to support future urban forest research is proposed to better understand and communicate the role of urban trees in urban biogeochemical cycles that are highly disturbed, highly managed, and of paramount importance to human health and well-being.
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Locations of defective sidewalk blocks in Cincinnati, Ohio, were compared to various soil complexes in the city. Soils with a percentage of repair record greater than the percentage of soil coverage were identified. The Urban-Stonelick soil complex had a low frequency of repair history. The Switzerland-Urban soil complex had a moderate record, while the Rossmoyne-Urban soil complex and the Urban-Martinsville soil complex had high frequencies of repair when compared to the records of other soil series and complexes in the city. Soil surveys categorized the Switzerland-Urban soil complex with moderate limitations for road construction and the remaining soil complexes with severe limitations. The 4 soil series were selected, and associated sidewalks were randomly surveyed to determine sidewalk failure rates. Sidewalks did not fail at higher rates where trees were present. Sidewalks greater than 20 years old failed at a higher overall percentage rate. Sidewalks less than 20 years old on the Switzerland-Urban soil complex and the Urban-Martinsville soil complex appeared more stable and less prone to failure than the Rossmoyne-Urban and Urban-Stonelick soil complexes. Sidewalks less than 5 years old were not affected by trees in any soil. A variety of problems were identified as being involved in the failure of sidewalks. It appears that trees play a minor role in sidewalk service life. Extending service life of sidewalks will require the cooperation of urban foresters, landscape architects, and engineers.
Article
Tree root growth is opportunistic and occurs wherever the environment is favorable. A balance exists between the root system and the remainder of the plant, so that if part of the root system dies, part of the crown will also die. Both parts are connected by a well-developed conduction system. Approximately 99 percent of the roots occur within the surface meter of soil and extend outward over an area one to two or more times the height of the tree. Large woody roots form the framework and are typical in pattern for each species. The fine feeder roots occur in the leaf and litter layer, if present, and the surface mineral soil. Keen root competition occurs at the surface if a turf exists under the tree. Also, herbicides, etc. used on lawns may have detrimental effects on the trees through these fine absorbing roots. In the urban environment roots may follow cracks and crevices in pavements, pipelines, sewers and cables. At the same time the installation of these utilities may cut across established tree root systems with unfortunate consequences.
Article
Of 2232 street trees surveyed during 1986 in Manchester (13 per cent of the total), 30 per cent were causing damage to pavements and 13 per cent damage to kerbs. Trees planted into pavements caused significantly more damage than trees planted in planting strips. Trees in planting strips > 3 m wide caused significantly less damage than those in strips < 3 m wide. The most severe pavement damage usually occurred within a 2 m radius from the base of the trunk. Significantly more damage occurred to pavements sealed with tarmacadam (asphalt) than to those paved with slabs. However, displaced slabs more commonly pose a safety hazard to pedestrians.Of the 8 commonest species and species groups of trees in the survey (lime (Tilia sp.), ash (Fraxinus excelsior L.), whitebeam/rowan (Sorbus spp.), sycamore/maple (Acer spp.), cherry (Prunus sp.), oak (Querus spp.), birch (Betula spp.), horse chestnut (Aesculus hippocastanum L.)), lime and ash caused the most pavement and kerb damage, whitebeam/rowan and cherry the least pavement damage and cherry and oak the least kerb problems. Most trees started to cause damage when they were 11—20 cm dbh but oaks and horse chestnut not generally until >20 em dbh. The distance apart at which trees were planted had no significant effect on pavement or kerb damage.To minimise pavement problems it is recommended that trees are planted in planting strips, which should be as wide as possible. If planted into pavements an unsealed area, ideally at least 2 × 2 m, around the tree base will reduce the severity of damage. Kerb problems can be reduced by planting in such a position that the trunk will be at least I m distant from the kerb when the tree is mature. When replacing large trees such as lime and ash along narrow and restricted streets it is advisable to plant inherently smaller species such as whitebeams or cherries. Where space is not so limited oak, sycamore or Norway maple are likely to cause less damage then lime, ash or horse chestnut.
Article
For 75 trees each of 12 species growing along streets in San Juan, Puerto Rico and Mérida, Mexico, diameter at breast height and distance to sidewalk or curb was measured and damage (cracking or raising) was evaluated. Logistic analysis was used to construct a model to predict probability of damage to sidewalk or curb. Distance to the pavement, diameter of the tree, and species were all found to contribute significantly to the probability of damage. Predictive models are presented for each species and numerical trials are used to illustrate the relationship of the independent variables to probability of damage.
Article
A survey of 18 California cities indicated that approximately $70.7 million (se $11.1 million) was spent annually statewide due to conflicts between street tree root growth and sidewalks, curbs and gutters, and street pave- ment. The largest single expenditure was for sidewalk re- pair ($23 million, se $9.5 million), followed by curb and gutter repair ($11.8 million, se $2.6 million), and trip and fall payments and legal staff time ($10.1 million, se $2.2 million). Property owners paid 39% and 17% of tree-re- lated sidewalk and curb and gutter repair costs, respec- tively. Substantial funds were invested to remove and replace trees in conflict with hardscape ($6.8 million, se $3.6 million), and for inspection and repair administration programs ($5.9 million, se $1.3 million). Root pruning ($2.5 million, se $2.0 million) and root barriers ($676,854, se $175,655) were the most important mitigation and pre- vention measures. Restricted planting space and the type of tree species selected were reported as the most important factors responsible for hardscape damage.
Article
Several environmental factors influence tree growth at any site. The objective of this study was to examine the relationship between biotic and abiotic factors and tree growth rate (mean ring width averaged over the last 10 years) in settings ranging from urban to rural. Six “clusters”, each with five communities and two rural parks, were sampled in Illinois, Iowa, Minnesota, Missouri, and Wisconsin, for a total sample of 320 trees. Within each community, trees in parks, and along residential and commercial streets were sampled. Five species were sampled: silver maple (Acer saccharinum L.), honeylocust, (Gleditisia triacanthos L.), hackberry (Celtis occidentalis L.), black maple (Acer nigrum Michx F.), and basswood (Tilia americana L.). Factors were investigated for three scenarios: (i) all trees sampled in all clusters, (ii) a single species, all clusters, and (iii) all species, a single cluster. Baseline variables (cluster, place population, site, species, and age) accounted for 49–71% of observed variation in growth rate. Combined biotic factors accounted for 5 to 6% of observed variation. For all species in a single cluster, combined abiotic factors accounted for 11% of observed variation. Biotic factors related to growth rate detected using multivariate analyses included number of other trees within 9 m, presence of disease and insects, and human-induced mechanical injury. Abiotic factors that were related to tree growth included presence of pavement and core bulk density. For trees in rural parks, number of other trees within 20 m, and for trees in both rural and community parks, number of other trees within 9 m of sample trees were associated with decreased growth rate.
Article
The accuracy of direct (based on increment cores) and indirect (based on age-size relationships) methods of tree age estimation in Fagus sylvatica and Quercus robur was tested. This was done through increment cores and stem discs taken in an old-growth forest of Northern Spain. It was found that cross-dating was more precise than ring counting by up to 7 years per tree. Furthermore, cross-dating permitted the estimation of the age of trees with floating ring-width series, which were 7% of cored F. sylvatica and 40% of Q. robur ones. In partial cores with the arcs of the inner rings, the length of the missing radius was estimated with both a geometric method, based on the curvature of the arcs, and a new graphical method, based on the convergence of xylem rays at the pith. The graphical method was more accurate when the radial growth was eccentric, as happens in Q. robur, while both methods showed a similar accuracy for F. sylvatica, whose growth is relatively concentric. Empirical models of initial radial growth (IRG), built to estimate the number of missing rings, reduced the errors associated with other methods that assume constant growth rates. Age estimates obtained from the graphical method combined with the IRG models were within 4% of the actual age. This combination ensured age estimates with a mean accuracy of 8 years for 98% of the F. sylvatica trees, and 4 years for 89% of the Q. robur. In partial cores without the arcs of the inner rings, the length of the missing radius was estimated as the distance to the geometric centre of the tree. In that case, age estimates obtained by extrapolating the mean growth rate of the 20 innermost rings in the cores were from 10 to 20% of actual age, which coincided with results obtained in other tree species with this method. Finally, the age-diameter equations of the different cohorts produced better age estimates (from 8 to 14% of actual age) than equations of the population as a whole (from 20 to 40% of actual age). These results proved that the errors derived from doubtful assumptions, such as concentric radial growth, constant growth and recruitment rates, or the absence of anomalous rings, could be reduced by applying more realistic methods of tree age estimation.
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