Structural response of black locust (Robinia pseudoacacia L.) and small-leaved lime (Tilia cordata Mill.) to varying urban environments analyzed by terrestrial laser scanning: Implications for ecological functions and services

Quantitative measurements of structure and morphology of urban trees are hardly exhausted so far, especially in regard to variations caused by altering urban environments. However, structure and functions of trees are heavily interwoven. In fact, knowledge about structural attributes is essential for a better understanding of urban ecosystem functions and services. In order to scrutinize spatially explicit and detailed structural attributes under varying urban environments, we acquired terrestrial laser scans and applied the according methodological approaches to the common urban tree species black locust (Robinia pseudoacacia L.) and small-leaved lime (Tilia cordata Mill.). We analyzed 52 small-leaved limes and 41 black locust trees within the city of Munich (Germany). Species as well as growing location had a significant effect on the height-diameter relation. We also found greater crown volumes for small-leaved lime. Black locust however, displayed more crown projection area and likely more shade efficient crown shapes at similar volumes. Stem inclination of black locust was found to be higher in parks than in street canyons with town squares lying in between. Furthermore, black locust displayed strong crown asymmetry in park areas, likely caused by competition with neighbors. The angles of main branches did not differ significantly between both species nor between the growing location. Branch angles, branch bending, the length of the branches as well as species and growing location had a significant effect on vertical crown center position, i.e. general crown shape. Surface complexity of lime is lower than of black locust, with its lowest manifestation in parks. Fractal-like crown surface structures, increasing surface roughness and complexity, were found to be more pronounced for black locust than for small-leaved lime. Thereby, black locust featured the highest crown surface complexity in parks, the lowest in street canyons. The results suggest that studies on spatially explicit tree structures may contribute to more target oriented tree plantings and thus, more effective exploitation of ecosystem services and benefits.     

Diversity of street tree populations in larger Danish municipalities

Healthy and sustainable tree populations require a high diversity of genera and species. This study examined the occurrence and contents of tree inventories in Denmark's 30 largest municipalities. 59% of the municipalities had a tree inventory for street trees, but only about half of these were complete and updated. Only one municipality had a registration for trees other than street trees. Based on data from the tree inventories, the diversity of road side trees was analyzed at genus level and species level. A total of 82,072 street trees are part of the study. 11 different genera account for 92% of the total street tree stock, and 2–6 genera account for 40–80% of the street tree stock in the individual municipalities. Tilia was the most dominating genera (26%). 12 species account for 73% of the total street tree stock. The 6 most common species account for almost 50% of the total tree population. The species representing the largest numbers were Tilia × europaea (12%), Acer platanoides (10.9%), Platanus × acerifolia (7.2%), Tilia cordata (7.2%), Fraxinus excelsior (6.2%) and Sorbus intermedia (5.9%). The four most urbanized municipalities had a surplus of non-native species, but all municipalities apart from one had most street trees belonging to native species. The concluding recommendation of this study is that tree managers need to start working more strategic with their tree stock, in order to reduce the vulnerability, due to potential attacks from pests or diseases and climate change effects. A risk spreading system for the urban tree population is proposed, suggesting that no genera should account for more than 10% and no species for more than 5% of the tree population.     

Diversity and distribution of the urban tree population in ten major Nordic cities

In order to have a healthy and sustainable urban tree population, a high diversity of species and genera is needed. This study examined (1) the diversity and distribution of genera and species of urban trees in the Nordic region; (2) the diversity in different sites of the city, distinguishing between street and park environments; and (3) the presence of native versus non-native tree species in urban environments in the Nordic region. The analysis of tree diversity was based on urban tree databases comprising a total of 190 682 trees in 10 Nordic cities – Aarhus and Copenhagen in Denmark; Espoo, Helsinki, Tampere and Turku in Finland; Gothenburg, Malmo and Stockholm in Sweden; and Oslo in Norway. The tree databases for Copenhagen, Espoo, Helsinki, Stockholm and Tampere only record street trees, while the remaining databases also include park trees. Tilia was the most dominant genus in Arhus, Copenhagen, Espoo, Gothenburg, Helsinki, Oslo and Stockholm, while Sorbus was the most dominant in Malmo and Betula in Tampere and Turku. Tilia × europaea was the most common species, comprising 16.0% of the total number of tree species. There was a higher proportion of species in parks than in street environments. The number of non-native species was higher than the number of native species in both street and park environments. However, the number of individuals belonging to native species was higher than the number of non-native individuals in all cities and environments except park environments in Arhus. The concluding recommendation from this study regarding greater diversity of genera and species is to exploit local experiences of rare species from local urban tree databases. After appropriate evaluation, urban tree planners can evaluate these rare species in larger numbers for e.g. street environments, where the need is greatest.     

Shade factors for 149 taxa of in-leaf urban trees in the USA

Shade factors, defined as the percentage of sky covered by foliage and branches within the perimeter of individual tree crowns, have been used to model the effects of trees on air pollutant uptake, building energy use and rainfall interception. For the past 30 years the primary source of shade factors was a database containing values from 47 species. In most cases, values were obtained from measurements on a single tree in one location. To expand this database 11,024 shade factors were obtained for 149 urban tree species through a photometric process applied to the predominant species in 17 U.S. cities. Two digital images were taken of each tree, crowns were isolated, silhouette area defined and shade factors calculated as the ratio of shaded (i.e., foliage and woody material) pixels to total pixels within the crown silhouette area. The highly nonlinear relationship between both age and diameter at breast height (DBH), and shade factor was captured using generalized additive mixed models.We found that shade factors increased with age until trees reached about 20 years or 30 cm DBH. Using a single shade factor from a mature tree for a young tree can overestimate actual crown density. Also, in many cases, shade factors were found to vary considerably for the same species growing in different climate zones. We provide a set of tables that contain the necessary values to compute shade factors from DBH or age with species and climate effects accounted for. This new information expands the scope of urban species with measured shade factors and allows researchers and urban foresters to more accurately predict their values across time and space.     

FlorTree: A unifying modelling framework for estimating the species-specific pollution removal by individual trees and shrubs

Atmospheric pollution is a threatening problem around the world, with tropospheric ozone (O₃), nitrogen dioxide (NO₂) and particulate matter (PM₁₀) among the most harmful pollutants for citizens’ health. Nature-based solutions such as urban trees can cut down air concentrations of these pollutants thanks to stomatal uptake and dry deposition on their canopies and, in addition, uptake carbon dioxide (CO₂) and store carbon in their tissues. Unfortunately, some species emit biogenic Volatile Organic Compounds (bVOCs) that are O₃-precursors leading to air quality deterioration. As a proper selection of species is essential for urban greening, we developed an innovative single-tree model (FlorTree) to estimate the maximum flux of air pollutants. FlorTree considered species-specific parameters, such as tree morphology (height and crown leaf area), leaf/shoot structure, leaf habit (deciduous/evergreen) and eco-physiological responses to environmental factors, for 221 urban tree and shrub species. We applied the FlorTree model to examine i) which are the best species for air pollution removal in the case study of Florence (Italy) and ii) whether the species-specific removal performance is affected by different climate and air pollution conditions in other cities, namely Bucharest (Romania) and Tokyo (Japan). Results suggested that 24 tall trees (mainly broadleaves belonging to Tilia, Acer and Fraxinus genus) may be recommended for Florence due to their large crowns at maturity (50 years old), relatively high stomatal conductance and no bVOCs release. These general characteristics, however, were affected by climatic and pollutant conditions, suggesting that FlorTree must be applied to the local conditions. Therefore, our results demonstrated that FlorTree can be applied in any city for maximizing the air quality improvement by urban trees.     

Spatial patterns of a subtropical,coastal urban forest: Implications for land tenure,hurricanes, and invasives

Spatial patterns of tree structure and composition were studied to assess the effects of land tenure, management regimes, and the environment on a coastal, subtropical urban forest. A total of 229 plots in remnant natural areas, private residential, public non-residential, and private non-residential land tenures were analyzed in a 1273 km² study area encompassing the urbanized portion of Miami-Dade County, USA. Statistical mixed models of structure, composition, location, and land tenure data were used to analyze spatial patterns across the study area. A total of 1200 trees were measured of which 593 trees (49%) were located in residential areas, 67 (6%) in public non-residential areas, 135 trees (11%) in private non-residential areas, and 405 (34%) in remnant, natural areas. A total of 107 different tree species belonging to 90 genera were sampled. Basal area in residential land tenures increased towards the coast while private residential land tenures and natural areas had higher species diversity than non-residential areas. Tree height, crown light exposure, and crown area might indicate the effects of past hurricane impacts on urban forest structure. Land tenure, soil types, and urban morphology influenced composition and structure. Broadleaf evergreen trees are the most common growth form, followed by broadleaf deciduous, palms, and conifers. Exotic tree species originated mainly from Asia and 15% of all trees measured were considered exotic-highly invasive species. We discuss the use of these results as an ecological basis for management and resilience towards hurricane damage and identifying occurrence of invasive, exotic trees.     

Allometric equations for urban ash trees (Fraxinus spp.) in Oakville,Southern Ontario,Canada

Tree growth equations are an important and common tool used to effectively assess the yield and determine management practices in forest plantations. Increasingly, they are being developed for urban forests, providing tools to assist urban forest managers with species selection, placement, and estimation of management costs and ecosystem services. This study describes the development of allometric equations for Fraxinus americana and F. pennsylvanica growing in Oakville, Canada. With data collected from 103 ash trees, five allometric models were tested to develop equations estimating diameter-at-breast-height (dbh), tree height, crown width and crown height, using age and dbh as explanatory variables. Mean annual growth rates are presented to demonstrate species growth performance and were not significantly different over the first 40 years of growth for the two species. Of all the tested random coefficient models for both species, the cubic with weight 1/x provided the best fit for estimating dbh from age. The best models for other parameters were the loglog for crown height from dbh, the quadratic for crown diameter from dbh, and the linear for tree height from dbh for F. americana. Model types showed more consistency for F. pennsylvanica with linear providing the best fit for crown diameter, crown height and tree height from dbh. The number of model types suggests the difficulty of fitting any single model to the vast array of conditions affecting plant growth in urban areas where management practices and environment can significantly influence tree size and growth. These models may be used to estimate the growth of ash tree populations in Oakville and communities with similar climate, soil, planting, and management environments.     

缙云山食(药)用大型真菌资源调查研究

对缙云山自然保护区内食用与药用大型真菌资源进行调查研究。结果显示,保护区内拥有食用与药用菌共32科60属92种,其中食用菌26科46属72种,药用菌24科36属55种;食药双重价值类真菌18科24属35种;腐生真菌70种,菌根菌25种;该区食用与药用真菌十分丰富,具有较大的潜在利用价值。     

Effect of native habitat on the cooling ability of six nursery-grown tree species and cultivars for future roadside plantings

Vegetation in urban areas provides benefits to people, which are increasingly assessed and valued as ecosystem services (ESS). The regulation of the urban microclimate is one of these services, since trees have the potential to reduce urban heat loads by evapotranspiration and shading. Simultaneously, it has been suggested that trees from dry habitats should be used to cope with the increasing risks of drought under climate change in Central Europe. The underlying properties that enable those trees to reduce dependence on the environment, however, are assumed to come at the expense of biomass production and water loss. In the potentially conflicted area between drought tolerance and ESS we compared water consumption, water-use efficiency (WUE), crown structure and growth of six roadside species/cultivars, which are assumed to vary in drought tolerance, due to differing resource supplies in their native habitats. Acer platanoides, Carpinus betulus ‘Fastigiata’, and Tilia cordata ‘Greenspire’ were compared with Acer campestre, Ostrya carpinifolia, and Tilia tomentosa ‘Brabant’, the latter presumably being less water-demanding. Measurements took place in the municipal nursery of Munich during summer 2016.Surprisingly, the less water-demanding species/cultivars exhibited on average 1.24 times higher values of maximum daily sap flux density and up to seven times higher growth rates, both contributing to higher WUE. Scaled to leaf level, however, their mean daily transpiration rates were on average lower (0.21 and 0.31 kg H₂O m⁻² d⁻¹, respectively). They also showed higher flexibility in response to changing weather with increased growth and transpiration under favorable conditions in early summer, but a more conservative water use in dry late summer. The results suggest that these species/cultivars tend to regulate their water use stronger under increasing dryness, whereas canopy size and leaf amount are still the main important determinants of species and cultivar differences in water use.     

Toxic impact of the de-icing material to street greenery in Riga, Latvia

There is little information on the ecological composition of snow on roads as well as the toxic effect of de-icing salt on the ecological status of the street trees (Tilia x vulgaris H.) in Latvia. Tilia x vulgaris is one of the most widespread tree species of street greenery in the boreo-nemoral zone – in Central, Northern and Eastern Europe. This investigation was done to find out the accumulation of de-icing salt (main elements – sodium and chlorine) in the snow–soil–plant system of street greenery in the central part of Riga (2004–2005), in order to reveal the toxic effect on the ecological status of the street trees (Tilia x vulgaris). Snow, soil and leaf samples were collected from 27 study sites (eight objects) in the central part of Riga with intense traffic and from three control sites (one object) located in a park area. In a majority of cases, the status of street trees could be characterized as damaged. There was a high heterogeneity in the Na and Cl concentrations even along one street. Significantly, increased levels of Na and Cl in urban snow, soil and leaf samples were found in comparison with the background values. There was close correlation between the Na, Cl concentration in the leaves and the extent of leaf necrosis. Principal new information on the critical level for observation visual Tilia x vulgaris leaf necrosis was stated based on our results: 0.14% Na and 0.66% Cl concentrations in the leaves.     

Poisonous and allergenic plant species in preschool’s and primary school’s yards in the city of Novi Sad

Presence of the poisonous and allergenic plant species was observed in 8 primary schools and 6 preschools in Novi Sad, Serbia. The aim of this research was to determine the extent to which pre-school and school-age children are exposed to harmful plant species and also to gain insight does the present landscaping take into account the appropriateness in the use of certain ornamental species in arranging preschool's and school's greenery. In the analyzed locations 22 poisonous plant species were noticed, mainly belonging to genera Thuja, Symphoricarpos, Cotoneaster, Juniperus, Berberis and Taxus, represented with 367 specimens. Along with poisonous, 21 allergenic plant species mainly belonging to genera Acer, Tilia, Betula, Populus, Platanus, Celtis, Aesculus, Thuja, Ulmus, Robinia and Quercus, represented with 675 specimens, were determined. The calculated allergenic index grouped most of the investigated species into strongly allergenic (calculated A.I. = 7) due to their prolonged phenantesic period, high abundance and possible cross-reactivity with other species noticed in the greenery. Establishment and enhancement of the collaboration between schools and experts from relevant institutions would result in the removal of the very most allergenic and poisonous landscape plants and ultimately toxic-free and allergy-friendly school yards. Gradual removal might temper the public reluctance to this measurement, but finally only joint efforts and complete abandonment of pointed species can convert unhealthy school yards into ones that are safe and allergy-friendly.     

武陵山脉七曜山区大型真菌资源调查

报道了武陵山脉七曜山区大型真菌资源126种,其中食、药用菌105种、毒菌7种,隶属于2亚门9目30科61属.调查发现,该地区大型真菌种类分布于阔叶林中有74种, 针阔混交林中有39种,针叶林中有35种,灌木林中有17种.已调查的大型真菌资源中有外生菌根菌69种,木生菌32种.-     

Tree composition and diversity in relation to urban park history in Hong Kong,China

In densely populated cities that are dominated by concrete buildings, urban parks serve as major green infrastructures for ecological and environmental functions. Trees are one of the important components that support these green infrastructures. Despite plenty of urban parks established in Hong Kong in the last 20 years, knowledge of tree composition and diversity is outdated. There were also no studies that investigated the differences in tree diversity in relation to park history. Therefore, this study aims to identify the temporary changes in tree composition and diversity in Hong Kong, by conducting a plot-based tree survey in 32 urban parks of different ages. Overall, 2801 trees belonging to 181 species were recorded in 319 plots across all the parks. A ridit analysis was conducted and it indicated the mature size of trees were not significantly larger in old parks. However, the linear mixed-effects models and the post-hoc tests suggested that DBH, tree height and the proportion of crown dieback for each class of tree size were greater in the old parks. Moreover, the composition of top-ranking dominant tree species varied substantially, where more ornamental and exotic trees were adopted in new parks. For species richness, the sample-based species accumulation curves of different park age overlapped when the horizontal axis of the curve was scaled by the average number of combined individual trees. When the horizontal axis was scaled by the number of plots, the curve for the old parks was above the curve for the new parks. The differences derived from these two accumulation methods indicated a higher tree density in old parks. For species evenness, both the rank-abundance curves and Rényi diversity curves depicted a similar low species evenness in old and new parks. These results suggested that species diversity remained largely unchanged from old parks to new parks though the dominant tree species varied. Greater attention should be paid to increase the species evenness in all urban parks, increase tree density in new parks and improve tree maintenance in old parks.     

Can canopy temperature acquired from an airborne level be a tree health indicator in an urban environment?

Nowadays, gathering information about tree health conditions in cities is necessary. Trees are essential in regulating urban microclimate and mitigating the urban heat island effect. Therefore, their health status should be crucial in urban vegetation monitoring. The growing number of new cameras, sensors and research methods allows for a broader application of thermal data in remote sensing vegetation studies. This research aimed to evaluate whether it is possible to use thermal infrared data to assess the health condition of selected species of deciduous trees in an urban environment. More specifically, the data must have a 3.6–4.9 µm spectral range, obtained during the day and the night. For this purpose, research was carried out in the city center of Warsaw (Poland) in 2020. During the airborne data acquisition, thermal data, laser scanning and RGB images were collected. Synchronously with airborne data, 617 ground references were obtained in different health condition classes (healthy, slightly poor condition, poor condition and dying) for five tree species: Acer platanoides, Acer pseudoplatanus, Aesculus hippocastanum, Tilia cordata and Tilia × euchlora. The results were as follows: (i) healthy trees were cooler than trees in poor condition and dying both during the daytime and nighttime; (ii) the difference in the canopy temperatures between healthy and dying trees was 1.06 °C of mean value on the nighttime data and 3.28 °C of mean value on the daytime data; (iii) all condition classes significantly differ from each other on daytime thermal data. The aerial thermal data can be considered a new alternative to hyperspectral data. Thermal sensing represents another method of assessing the health condition of trees in an urban environment – especially data obtained during the day, which can differentiate condition classes better than data obtained at night. The method based on thermal infrared and laser scanning data fusion could be a quick and efficient solution for identifying trees in poor health.     

The feasibility of remotely sensed data to estimate urban tree dimensions and biomass

Accurately measuring the biophysical dimensions of urban trees, such as crown diameter, stem diameter, height, and biomass, is essential for quantifying their collective benefits as an urban forest. However, the cost of directly measuring thousands or millions of individual trees through field surveys can be prohibitive. Supplementing field surveys with remotely sensed data can reduce costs if measurements derived from remotely sensed data are accurate. This study identifies and measures the errors incurred in estimating key tree dimensions from two types of remotely sensed data: high-resolution aerial imagery and LiDAR (Light Detection and Ranging). Using Sacramento, CA, as the study site, we obtained field-measured dimensions of 20 predominant species of street trees, including 30–60 randomly selected trees of each species. For each of the 802 trees crown diameter was estimated from the aerial photo and compared with the field-measured crown diameter. Three curve-fitting equations were tested using field measurements to derive diameter at breast height (DBH) (r² = 0.883, RMSE = 10.32 cm) from the crown diameter. The accuracy of tree height extracted from the LiDAR-based surface model was compared with the field-measured height (RMSE = 1.64 m). We found that the DBH and tree height extracted from the remotely sensed data were lower than their respective field-measured values without adjustment. The magnitude of differences in these measures tended to be larger for smaller-stature trees than for larger stature species. Using DBH and tree height calculated from remotely sensed data, aboveground biomass (r² = 0.881, RMSE = 799.2 kg) was calculated for individual tree and compared with results from field-measured DBH and height. We present guidelines for identifying potential errors in each step of data processing. These findings inform the development of procedures for monitoring tree growth with remote sensing and for calculating single tree level carbon storage using DBH from crown diameter and tree height in the urban forest.     

井冈山自然保护区野生食(药)用菌资源调查初报

2015年~2017年间,首次对井冈山自然保护区野生食(药)用菌资源进行了调查统计,记录了野生食药用菌46属共58种,其中食用菌39种、药用菌9种、食(药)用菌10种;优势种类14种,珍贵种类9种,并提出了持续利用建议。     

Mistletoe infection in an urban forest in Mexico City

Urban forests are important lungs for urbanized environments; therefore, their study and conservation are needed. Compared with trees in natural areas, urban trees develop in more stressful conditions, which may make them more susceptible to infections by parasites such as mistletoes. Bosque de Tlalpan (BT) is an urban forest embedded in one of the largest cities of the world, Mexico City. The aim of this study was to assess which mistletoe species were present in BT, determine the intensity of the infestation, and distinguish which host species are more susceptible to mistletoe parasitism based on 20 randomly selected plots. We found that Cladocolea loniceroides was extensively distributed on the cultivated area of BT (17 plots), whereas a second species, Phoradendron brachystachyum, was found only on four plots. Seven tree species were susceptible to infection by C. loniceroides, whereas only one was susceptible to infection by P. brachystachyum. Fraxinus uhdei, the most abundant host, was the one with higher severities and larger sizes (tree height and crown length); the latter variables positively influence the severity of infection. Reforestation of the cultivated area with low diversity and exotic species appears to be a reason for the increased infestation. Therefore, we support the reforestation of urban areas with native species to provide benefits such as a lower incidence of parasitic infection and tree mortality.     

Long-term impact of road salt (NaCl) on soil and urban trees in Edmonton,Canada

The application of de-icing salts for winter road maintenance is recognized as a major contributor to the decline of urban trees. We conducted a long-term monitoring program across several locations in the City of Edmonton (Alberta, Canada) to evaluate the impact of roadway salt application on tree species widely planted in boulevards and right-of-ways: Ulmus americana, Fraxinus pennsylvanica, Pinus contorta, and Picea glauca. Soil and leaf samples were collected from a total of 16 sites over six years. There were four sites selected for each tree species: three mid- to high- traffic roadside sites that received regular winter maintenance and one non-serviced site (control). Sampling was performed three times per year from late spring to late summer. Airborne salinity was assessed in four locations at different distances from the road. In 50% of the roadside sites, soil electrical conductivity (EC) values exceeded 2 dS m⁻¹. Soil pH in all of the roadside sites was also significantly higher than in the control sites, with values ranging from 7.6 to 8.5. In all four species, trees growing in sites with high soil EC had increased leaf Na concentrations and reduced leaf chlorophyll concentrations. Among the airborne monitoring sites, Na deposition in high traffic locations was over four-fold higher than those measured in the control location. Furthermore, Na levels remained relatively high at 20–50 m from the main road. Our data suggest that while soil salinity is among the main stressors affecting roadside trees in Edmonton, salt spray deposition may also have a significant impact on trees located close to high vehicle traffic areas and dense road networks. Our study highlights the importance of collecting data over several years and from multiple locations to account for the spatial and temporal heterogeneity of the urban environments in order to better evaluate the impact of road salt application on urban trees.     

How good are containerized trees for urban cooling?

The capacity of urban trees in mitigating urban heat is well-known. As space is often limited, one feasible option for increasing the urban green would be containerized plants. Nevertheless, for optimizing the vitality and benefits, detailed knowledge on tree growth reactions in different types of containers is missing. We designed an experiment with two commonly planted but ecologically contrasting urban tree species Tilia cordata and Platanus x hispanica planted into the ground and in containers according to four different planting types, with or without drought stress. Along with the meteorological variables, continuous soil moisture and temperature at 25 cm depth, sap flow, as well as measurements of leaf physiological responses i.e. stomatal conductance, mid-day leaf water potential and chlorophyll content were measured three times on sunny and warm summer days during 2020 and 2021. P. hispanica showed more than double diameter increment at breast height in the ground than in containers; however, the growth trend was relatively better for T. cordata in containers. While comparing different container types and species reactions, it was clear that soil temperature within the plastic containers were significantly higher, whereas insulation is not enough to reduce either the temperature or slowing down the soil drying out. Where both the species showed lower stomatal control over atmospheric demand, P. hispanica showed leaf transpiration energy loss of around 300 W m⁻² when planted in the ground and T. cordata trees around 260 W m⁻² when planted in non-insulated containers, which are comparable to the energy loss from the street trees. Therefore, a strategy of mixed planting with faster growing species such as P. hispanica that provide stronger cooling at the initial stage in the containers to be complemented and eventually replaced with medium growing species T. cordata for relatively longer time period could be suggested.     

Carbohydrate dynamics in roots,stems, and branches after maintenance pruning in two common urban tree species of North America

The ability of plants to tolerate stress is determined in part by the carbon allocated to their reserves. We studied two common urban tree species in northeastern North America, Acer saccharinum (Silver maple, native) and Acer platanoides (Norway maple, exotic), to assess the dynamics of non-structural carbohydrate (NSC) concentrations immediately following a maintenance pruning of 30% of the tree crown. NSC concentrations were measured by high-performance liquid chromatography in branches, main stems, and root tissues for both pruned and un-pruned trees at three intervals during the growing season. NSC concentrations in tree organs of A. platanoides were 75% higher than in A. saccharinum. Maintenance pruning did not have any significant depletion effect on carbohydrate concentrations in the tissues of either species. Yet, there was a significant increase in the NSC concentrations in un-pruned branches of pruned trees of A. platanoides at the end of the growing season, but no effect was observed in A. saccharinum. Higher levels of carbohydrates after pruning in woody plant tissues suggested that A. platanoides may have compensatory mechanisms that allow this species to respond better to maintenance pruning than A. saccharinum.