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A tree diversity inventory was carried out in urban green spaces (UGSs) of Chennai metropolitan city, India. This inventory aims to study the diversity, density and richness of trees in UGSs of Chennai. A total of one hundred 10 m × 10 m (total 1 ha) plots were laid to reveal tree diversity and richness of UGSs. Trees with ≥10 cm girths at breast height (gbh) were inventoried. We recorded 45 species in 42 genera and 21 families. Caesalpiniaceae and Fabaceae each with 6 species dominated the study area followed by Arecaceae (3). Density and stand basal area of the present study were 500 stems ha?1 and 64.16 m2, respectively. Most of the inventoried trees were native (31 species) and deciduous (28 species). Fabaceae and Caesalpiniaceae dominated the present study area in terms of stand basal area and density. The Shannon diversity index and evenness of study area were 2.79 and 0.73, respectively. The most important species and families based on species important value index (IVI) and family important value index were Albizia saman, Polyalthia longifolia and Azadirachta indica; Fabaceae, Caesalpiniaceae and Annonaceae respectively. We find Chennai's urban forest is relatively superior to many urban forests of the world in terms of stand basal area and species richness. Results emphasize the importance of enhancement of urban green spaces in Chennai metropolitan city.  相似文献   

3.
Field data from randomly located plots in 12 cities in the United States and Canada were used to estimate the proportion of the existing tree population that was planted or occurred via natural regeneration. In addition, two cities (Baltimore and Syracuse) were recently re-sampled to estimate the proportion of newly established trees that were planted. Results for the existing tree populations reveal that, on average, about 1 in 3 trees are planted in cities. Land uses and tree species with the highest proportion of trees planted were residential (74.8 percent of trees planted) and commercial/industrial (61.2 percent) lands, and Gleditsia triacanthos (95.1 percent) and Pinus nigra (91.8 percent). The percentage of the tree population planted is greater in cities developed in grassland areas as compared to cities developed in forests and tends to increase with increased population density and percent impervious cover in cities. New tree influx rates ranged from 4.0 trees/ha/yr in Baltimore to 8.6 trees/ha/yr in Syracuse. About 1 in 20 trees (Baltimore) and 1 in 12 trees (Syracuse) were planted in newly established tree populations. In Syracuse, the recent tree influx has been dominated by Rhamnus cathartica, an exotic invasive species. Without tree planting and management, the urban forest composition in some cities will likely shift to more pioneer or invasive tree species in the near term. As these species typically are smaller and have shorter life-spans, the ability of city systems to sustain more large, long-lived tree species may require human intervention through tree planting and maintenance. Data on tree regeneration and planting proportions and rates can be used to help determine tree planting rates necessary to attain desired tree cover and species composition goals.  相似文献   

4.
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.  相似文献   

5.
Determining adequate sample size (ASS) and minimum plot size (MPS) are two fundamental issues in urban vegetation investigations. To estimate the ASS and MPS of urban plants, we introduced sampling completeness to the MPS calculation based on 54 samples in the urban area of Chongqing, China. Then, we examined the performance of the species-area curve method and CVJack1 (coefficient of variation (CV) for the first-order jackknife estimator (Jack1)) curve extrapolation method. We also tested the effectiveness and error distribution of extrapolating the ASS from CVJack1 curves using 180 samples from the urban area of Chongqing, China, and 222 samples from the urban area of Xiamen, China. The results of the urban plant analyses showed that (1) the constructed species-area accumulation curves fit a logistic function (R2 > 0.990); (2) the MPS increased with sampling completeness, whereas unrecorded species exhibited the opposite trend; (3) the CVJack1 curves fit the allometric1 function (R2 > 0.960) but might fail to reach a CV value of 0.05 for the calculation of ASS if the sample size was too small; and (4) the relative error values were below 5% when the error curves of extrapolation (by CVJack1 curve) approached a horizontal asymptote. The species-area accumulation curve with sampling completeness and the CVJack1 curve extrapolation method were promising approaches for determining the MPS and ASS of urban plants. The results and methods in this study provide a reference for determining the appropriate plot size and sample size for urban plant species richness investigations.  相似文献   

6.
Urban green spaces provide critical social and ecological support for cities, but we know little about their diversity and composition in cities of the Global South. This is especially true of lesser known urban spaces such as sacred sites, which are of important cultural and biodiversity significance. We examine tree diversity and composition in sacred sites in Bengaluru, one of India’s fastest growing cities. We recorded 5504 trees from 93 species across 62 temples, churches, and Hindu, Christian and Muslim cemeteries in central areas of Bengaluru. Over half (52%) of the tree species were of native origin, a much higher proportion when compared to other green spaces in the city such as parks. Tree density in sacred sites was much higher than that in parks and informal settlements in Bengaluru. Temples and Hindu cemeteries contained the highest proportion of native species, with large numbers of Ficus benghalensis, a keystone sacred species. Trees in sacred spaces provide an important buffer against urban environmental stress in Indian cities, and serve as refuges for urban wildlife and biodiversity. We need greater information on these lesser known, but culturally significant alternate spaces. They play an important, though ignored role in the environmental sustainability of rapidly growing cities in the Global South.  相似文献   

7.
Natural parks are comprised of preserved forested natural areas that are undergoing natural ecological processes. These areas can offer a refuge for local biodiversity and contribute substantially to ecosystem services in both rural areas with relatively low population densities, as well as high-density urban areas. Forested natural parks located in urban areas should experience more stressful environmental conditions than nearby rural areas, yet we know relatively little about how urbanization impacts tree communities within these important natural habitats. To better understand the impact of urbanization on forests, we investigated the species composition, abundance, and diversity of midstory and canopy trees as well as tree seedlings in urban and rural natural parks in and around Cleveland, Ohio. We found that both urban and rural natural parks have similar tree abundance, but midstory and canopy trees as well as tree seedling communities in the urban natural parks included higher abundances of stress-tolerant species compared to rural parks. In addition, this pattern was driven by changes in native tree species, as we observed low abundance of invasive species. More stress-resistant native species in urban areas include Quercus rubra and Prunus serotina, in contrast to rural natural parks which are dominated by Acer spp. and Fagus grandifolia. Lastly, we show that urban and rural natural parks have similar species diversity within plots, but we found higher variation in community composition among urban natural parks compared to among rural parks. Furthermore, Q. rubra and P. serotina were significantly larger in rural natural parks, indicating that both environmental stress and successional stage could drive compositional differences. Thus, we show that urbanization can have unexpected effects on plant community composition and diversity. Our study refutes the idea that these are degraded habitats, highlights the need to conserve them, and suggests that characterization of local variation in self-assembled urban tree communities will provide the most accurate picture of their management needs and potential ecosystem services.  相似文献   

8.
The knowledge of the rate at which trees grow in urban areas is an important aspect to consider as it can influence our quantification and valuation of the ecosystem services provided by an urban forest. This study investigates growth variations in diameter and height for four common urban tree species (Acer pseudoplatanus, Betula pendula, Fraxinus excelsior and Quercus robur) across five cities in Great Britain (GB) and how the typical radial growth of two of those species (F. excelsior and Q. robur) changes with climate. Dendrochronology was used to identify tree age and changes in ring width and diameter at breast height (DBH) and tree height were measured in-situ at the time of coring. Results indicate a substantial variation in the mean annual growth rates and the relationships between DBH and age or height and age of each species across different cities. However, the multiple factors affecting tree growth seem to influence different species in different ways, with for example A. pseudoplatanus trees showing overall the fastest growth in Peterborough but B. pendula ones showing the slowest. Precipitation and temperature had an effect on radial growth of F. excelsior and Q. robur trees in GB, but the strength and direction of influence varied with time of year, species and city. In particular, low precipitation at the start or during the growing season was found to be a significant factor limiting radial growth. A trend towards a reduction in ring width increment was therefore identified in hot and dry years, primarily in south-eastern cities but in other cities too. This highlights the risk that a changing climate may have on the growth and, consequently, on the ecosystem service provision of healthy urban trees.  相似文献   

9.
Urban street canyon morphology plays an important role in outdoor air quality and should be considered in tree planting schemes. However, the air pollutant reduction rate by street trees in different types of street canyon has rarely been analyzed for real urban environments. Therefore, this study conducted field investigation of 15 street canyons in residential areas to assess the reduction rate of particulate matter (PM) by trees in canyons with varying aspect ratio (AR) and orientation. The species of trees planted in these streets were Sophora japonica, Populus alba 'Berolinensis' L., Salix babylonica, Fraxinus chinensis, Pinus tabulaeformis, and Ulmus pumila. In the presence of trees, the mass concentration of fine PM (PM1) decreased most in narrow canyons (AR = 1.37–3.02), while the concentration of coarse PM (PM10) decreased most in wide canyons (AR = 0.45–0.69). The PM concentration increased most with tree planting in medium canyons (AR = 0.79–1.08). Additionally, street trees reduced fine PM concentration more in canyons with a 45° angle to the prevailing wind than in canyons aligned parallel to the prevailing wind. But they reduced coarse PM more in canyons aligned parallel to the prevailing wind than in canyons with a 45° angle to the prevailing wind. In comparison with tree-free cases, tree planting weakened the correlation between AR and coarse PM concentration, whereas no difference in correlation was found between AR and fine PM concentration. Overall, street canyon morphology should be considered seriously in developing tree planting guidelines for built-up environments.  相似文献   

10.
According to the national policy, overall forest and agroforestry cover in Rwanda is to increase up to 30% land cover by 2020. On the other hand, demographic data reveal that Rwanda's urban areas are among the fastest-growing on the continent. Unfortunately, there is only little information of the effects of such a rapid urbanization on tree cover and green space structure, knowing that data on urban plant assemblages in the country are rather rare. The paper discusses developments in Kigali's green spaces with regard to its rapid rate of expansion. An integrated approach of research, combining results from interview sessions, desk-based investigations, walk-over and vegetation surveys, and photogrammetric analyses of remotely acquired imagery was applied. The findings suggest that the city green space network consists of plant assemblages largely dominated by alien species (75%). Tree cover fraction averaged at around 10–35%. No significant difference was observed between field-drawn and photogrammetric-based fraction of tree cover estimates; making the later a quick but cheap tool for rapid tree cover evaluation. Cultivated forests, urban woodlots and domestic garden tree stands are far the most dominant types of green spaces in terms of coverage of city surface area. Street tree communities and institutional gardens appear to be the most intensively designed green space layouts. Both distribution and species composition in domestic gardens were socioeconomic-driven. For instance, palm trees were characteristic of fortunate quarters while fruitbearing ornamental such as Psidium guajava and Persea americana were common within scattered and informal settlements. Markhamia lutea, Erythina abyssinica, Euphorbia candelabrum, Phoenix reclinata and Acacia sieberiana are among native taxa that thrive to keep a place in the city. Euphorbia tirucalli, a native tree that is widespread in home compound fences within informal settlements, is significantly declining as modern housing expands and concrete-based fences replace live enclosures.  相似文献   

11.
This paper presents a method that allows sorting of tree and shrub species according to their suitability for planting in urban areas of Madrid (Spain). Suitability was determined from a weighted index for each species according to the severity of damage (biotic, abiotic, and anthropogenic; stem wounds are the main problem in trees, while dead plants are the most important problem in shrubs, seasonal flowers, and vines) and to risk, which was obtained from a new measure, observed Species per Green Area per Year (SAYs). The greater the number of damaged SAYs, the less suitable a species was considered for outdoor planting. For this purpose, 49 green areas corresponding to 141 ha were sampled during 2005–2008. The tree species least recommended for planting include Robinia pseudoacacia, Ulmus sp., Acer negundo, Platanus × hybrid, Populus Boolleana. The shrubs least recommended for planting are Nerium oleander, Cotoneaster sp., Euonymus europaeus, Pyracantha coccinea, and Pittosporum tobira. Statistical analysis reveals that native species have a lower percentage of damaged SAYs than non-native species.  相似文献   

12.
Air moisture is one of the main factors causing the greenhouse effect, but humidity has not been thoroughly studied at the ecosystem level. In 2006 a free-air humidity manipulation (FAHM) facility was established in Estonia to investigate the effect of humidity on the performance of two tree species—silver birch (Betula pendula Roth.) and hybrid aspen (Populus tremula L. × P. tremuloides Michx.). The trial is located on an Endogleyic Planosol of former arable land and offers the opportunity to change relative air humidity through controlled artificial misting and drying. We measured the CO2, CH4 and N2O emission from the FAHM system using closed chamber and gas-chromatograph techniques from July 2009 to October 2010. Measurements were carried out once a month in three humidification (h) plots and in three control (c) plots. The vegetation period was rainy in 2009, but the next summer was relatively dry. The dry summer interacted better with the humidification. The CO2 flux decreased when the air moisture was higher than in the control plots. The soil acted as a sink for methane. Less CH4 was oxidized in the soil with increased humidity. Emission of N2O did not correlate with air humidity, although one could observe a clear tendency that there was a smaller N2O flux during the period with increased humidity. Expectedly, CO2 emission and CH4 consumption demonstrated strong positive correlations with soil temperature.  相似文献   

13.
Anthropogenic ground-level ozone (O3) pollution can alter the phosphorus (P), carbon (C), and nitrogen (N) of terrestrial plants’ ecological stoichiometry, which in turn affects forest productivity, nutrient utilization, and carbon sink capacity. However, there is still quite a lot of uncertainty regarding the impact of high O3 levels on C-N-P stoichiometry in organs with a rapid turnover (i.e., fine roots and leaves) across varied functional types. This study investigated the effects of O3 on the stoichiometry of C-N-P nutrient allocation of stocks to various plant organs, with a special focus on tree species frequently employed for urban greening. The impact of O3 on C-N-P stoichiometry among different functional tree types was subsequently evaluated by reviewing the published literature. Under a pooling of all species, elevated O3 decreased and leaf C and P concentrations increased, thereby decreasing the leaf C: P ratio. Elevated O3 increased the N concentration in fine roots, thereby decreasing the C: N ratio, although no significant impact was observed in leaves. Elevated O3 significantly reduced the leaf stocks of C (CSleaf) and N (NSleaf), however, there was no observed variation in these stocks in fine roots. The content of P, C, and N in fine roots and leaves in evergreen broadleaf species exceeded those in deciduous species. Elevated O3 significantly reduced CSleaf, NSleaf, and PSleaf in deciduous broadleaf species, whereas there was a significant reduction for the same in evergreen species. The literature analysis further demonstrated a larger O3-induced increment in leaf P concentration in deciduous species as compared to evergreen species. Elevated O3 significantly increased the difference in C and N stocks between fine roots and leaves in deciduous broadleaf species, whereas this difference was observed to decrease in evergreen species. The results of this study can facilitate an improved understanding of ecological stoichiometric responses of urban greening tree species under O3 stress and the resulting nutrient use strategies.  相似文献   

14.
Environmental changes associated with urbanisation can affect the functioning of ecosystem processes. In cities, forests are among the most frequent types of green areas and provide a wide range of ecosystem services including air cleaning, decomposition of leaf litter and recreation. The European beech (Fagus sylvatica) is a frequent and widespread deciduous tree in temperate forests in Central Europe. In this study, we examined the effects of urbanisation on decomposition processes of F. sylvatica leaves in different-sized forests in the urban region of Basel, Switzerland. We used standardised litterbags (mesh size: 2 mm) with F. sylvatica leaves to assess the impact of degree of urbanisation (indicated by the percentage cover of sealed area in the surroundings) and forest size on the early stage of leaf litter decomposition and seasonal microbial activity. We found combined effects of degree of urbanisation and forest size on the decomposition rate of leaf litter (klitter). Large forests showed the highest klitter in areas with sparse settlements and the lowest klitter in densely settled areas, whereas the opposite pattern was recorded for small and medium-sized forests. This indicates that abiotic and biotic forest characteristics of forests of similar size differently influenced klitter depending on the degree of urbanisation. Moisture content of litter was the best predictor of microbial activity, followed by forest size. We assume that factors acting at the landscape scale such as the degree of urbanisation might be too coarse to detect any differences in microbial activity. Our results revealed that even small urban forests contribute to this important ecosystem function. As decomposers are at the bottom of the food chain, management actions that support the biological activity in soil might be also beneficial for species at higher trophic ranks.  相似文献   

15.
Although there is a common trend towards increasing green space in modern cities, urban green spaces provide not only ecosystem services but also disservices for urban dwellers. However, the relationship between urban greenness and ecosystem disservices has been poorly examined. We aimed to understand the effect of greenness level on the abundance and species composition of hornets – critical pests in Japan and to identify the best spatial scale for estimating their abundance with reference to greenness levels. We used a dataset that contained eight years of abundance data for four hornet species at 11 sites in Nagoya city. The levels of greenness around the hornet sampling points were measured using averages from the Normalized Difference Vegetation Index (NDVI) with radiuses of 0.1–10.0 km. We analysed the relationship between abundance and species composition of hornets and NDVI at different spatial scales using generalized linear mixed models. Higher NDVI values positively affected the abundance of all the hornet species except Vespa analis. The abundances were estimated most effectively using the NDVI average with a 1–2 km radius for all species. The species composition of hornets drastically changed along the gradient of NDVI values; V. mandarinia was dominant in greener areas (over 0.2–0.3 NDVI average with a 2 km radius) and V. analis in less green areas (below 0.2–0.3 NDVI average). Our study showed that the abundance and species composition of hornets were both strongly associated with the level of urban greenness. This suggests that increases in the greenness of urban areas can increase hornet abundance and alter the species composition of hornets; a more aggressive species, V. mandarinia, may also increase in urban areas, although V. analis is currently the most critical species according to regional consultants. Balancing ecosystem services and disservices has become crucial for the planning and management of green spaces, particularly when urban green space increases. We also demonstrate how human tolerance towards wildlife may have to be improved in order to live in greener environment where wildlife can be expected.  相似文献   

16.
A good knowledge of species diversity is essential for urban forest planning and management. In this study, we analyzed species diversity of urban forests in China using data synthesized through a systematic review. Our analysis showed that 3740 taxa of woody plants at species level and below have been reported in urban forests in 257 cities. Merging to the species level, there were 2640 species, including 1671 trees, 743 shrubs, and 226 lianas. Salix babylonica L. was the most widely distributed urban tree species in China. Overall, native species accounted for 76.02% of the observed species while the rest were exotic species. Inside cities, parks contained more species than other types of land use. Among cities, composition similarity of urban forests decreased as spatial distances among them increased. Besides, there was a latitudinal pattern in compositional similarity of urban forests in China. The relatively low ratio of the number of woody plant species in urban forests to these naturally distributed in China indicates that there is plenty of room for increasing species diversity of urban forests in China. However, cautions must be taken to avoid increasing compositional similarity of urban forests in China at the same time.  相似文献   

17.
The urban forest of three arctic and near-arctic cities (Murmansk in Russia, Nuuk in Greenland, and Reykjavik in Iceland) were surveyed to determine tree species composition and structure. Interviews with local authorities were conducted to learn about the history of urban tree planting. The urban forests of all three cities were composed of a limited number of trees and tree species due to abiotic constraints of the arctic and near-arctic environment. These limitations include: low temperature, short growing season, high wind velocity and permafrost. A total of 28 species were observed in the three cities. Only three of these (Alnus incana (L.) Moench, Picea abies (L.) Karst., Betula pubescens Ehrh., and Salix glauca L.) were observed in all three of the cities. Planting designs that created windbreaks for pedestrians were common along streets in Murmansk and Reykjavik. Street trees have not yet been introduced in Nuuk, but trees were found in cemeteries, parks, and on private property. Older portions of cemeteries in all three cities were characterized by trees planted directly on graves. These grave trees were the first trees to be introduced in these cities. Subsequently, ‘trial and error’ was used by local residents to plant trees. Much of these plantings failed. In recent times arboreta were established near all three cities to identify species suited for planting under arctic and near-arctic conditions. Trees identified in these test gardens are now being planted in Murmansk and Reykjavik.  相似文献   

18.
An analysis of tree health in urban greeneries exposed to winter road salt contamination was carried out in the cities of Alytus and Kaunas, Lithuania, during spring and summer 2009–2014. Trees were assessed for crown dieback, crown defoliation and foliage discolouration. In addition, the prevalence of saprotrophic pathogenic fungi that cause sooty mold disease was assessed in street and recreational plantings. Tilia cordata Mill. (small-leaved lime) was found to be the most common tree species among urban deciduous trees. Summarising the tree foliage results, saprotrophic fungi were detected on 16 species plants belonging to 13 genera. Three species of fungal pathogens belonging to two genera, two families, two classes, and two divisions, and 12 species of anamorphic fungi from nine genera were isolated and identified from Tilia cordata leaves. The most frequent sooty mold disease agents were Aspergillus brasiliensis and Cladosporium herbarum. Nonetheless, a weak correlation between salt contamination and lime tree damage by sooty mold was found.  相似文献   

19.
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.  相似文献   

20.
The Neotropical region is undergoing high levels of urban expansion and harbors the greatest diversity of vascular epiphytes globally. In cities, it could be expected that the density of woody vegetation positively predicts epiphyte communities by providing substrate, resources for pollinators, and buffering microclimatic conditions. However, there is a dearth of knowledge regarding how urbanization intensity affects the diversity of vascular epiphytes. In this study, we assessed the relationship between a woody cover gradient and bromeliad species richness and community composition across a streetscape of the Neotropical city of Xalapa (Mexico). We recorded bromeliads in nine street segments and one peri-urban green space. These sites represent a gradient of woody cover ranging from 10.5% to ∼87% in a 100 m buffer, and 100% in the peri-urban green space. We recorded 824 individuals of 14 species (all from the Tillandsioideae subfamily). The most abundant species was Tillandsia recurvata and the most frequent ones were T. juncea and T. schiedeana. Results show that bromeliad species richness was positively related to the woody cover, as expected. Interestingly, community composition did not associate with the percentage of woody cover. These results suggest that additional factors such as microclimatic conditions and seed availability and/or dispersal may be key modulators on the establishment of bromeliad species. Nevertheless, wooded streets do show potential for harboring diverse bromeliad communities.  相似文献   

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