Urban Trees

The effect of automobile pollution was determined on chlorophyll content of four different tree species viz. Azadirachta indica L., Conocarpus erectus L., Guiacum officinale L.and Eucalyptus sp. growing along the roads of the city.  Significant changes in the level of chlorophyll “a”, chlorophyll “b” and total chlorophyll “a+b” were found in the leaves of four tree species (A. indica, C. erectus, G.officinale and Eucalyptus sp.) collected from polluted sites (Airport, Malir Halt, Quaidabad) as compared to control site (Karachi University Campus). Lowest concentration of chlorophyll “a”, chlorophyll “b” and chlorophyll “a+b” was recorded in the leaf samples of all tree species collected from Quaidabad site when compared with the leaf samples collected from control site. The highest levels of chlorophyll pigment were recorded in all tree species leave samples collected from Karachi University Campus.  Similarly, better levels of chlorophyll “a”, chlorophyll “b” and total chlorophyll “a+b” was observed in all tree species growing at Airport site as compared to plants growing at Malir Halt and Quaidabad sites.  This study clearly indicated that the vehicular activities induced air pollution problem and affected on the level of chlorophyll pigments in trees which were exposed to road side pollution.

Urban trees can potentially mitigate environmental degradation accompanying rapid urbanisation via a range of tree benefits and services. But uncertainty exists about the extent of tree benefits and services because urban trees also impose costs (e.g. asthma) and may create hazards (e.g. windthrow). Few researchers have systematically assessed how urban tree benefits and costs vary across different cities, geographic scales and climates. This paper provides a quantitative review of 115 original urban tree studies, examining: (i) research locations, (ii) research methods, and (iii) assessment techniques for tree services and disservices. Researchers published findings in 33 journals from diverse disciplines including: forestry, land use planning, ecology, and economics. Research has been geographically concentrated (64% of studies were conducted in North America). Nearly all studies (91.3%) used quantitative research, and most studies (60%) employed natural science methods. Demonstrated tree benefits include: economic, social, health, visual and aesthetic benefits; identified ecosystem services include: carbon sequestration, air quality improvement, storm water attenuation, and energy conservation. Disservices include: maintenance costs, light attenuation, infrastructure damage and health problems, among others. Additional research is required to better inform public policy, including comparative assessment of tree services and disservices, and assessment of urban residents and land managers’ understanding of tree benefits and costs.

Javor negundovac (Acer negundo L.) je listopadno drvo iz Sjeverne Amerike, a u Hrvatsku je uvezen početkom 20. stoljeća. Cijenjen je u pčelarstvu, šumarstvu, krajobraznom uređenju te je vrlo invazivna vrsta. Od ukrasnih karakteristika vrste mogu se izdvojiti deblo, kora, habitus, grane, listovi, cvjetovi i plodovi. Zbog svoje velike prilagodljivosti podnosi vrlo siromašna tla te položaje koji su izloženi suncu, suši, hladnoći i sjeni. Najrasprostranjeniji je u kontinentalnom i submediteranskom dijelu Hrvatske. A. negundo se s vremenom dosta raširio tako da je na području Hrvatske svrstan u invazivnu alohtonu vrstu. Prema literaturnim izvorima navedena vrsta za sada ne pričinjava ozbiljnije štete autohtonoj vegetaciji. Negundovac (Acer negundo L.) slabo je zastupljena dendrološka vrsta na gradskim krajobraznimpovršinama Knina, kao soliter, u drvoredu ili u skupinama. Metodom promatranja je također uočeno da u pogledu održavanja i njege stabala A. negundo na krajobraznim površinama nužno posvetiti više pažnje u formiranju krošnje. Nisu uočena njegova stabla van gradskih krajobraznih površina. Anketno istraživanje je provedeno tijekom druge polovice 2017. godine na uzorku od 50 ispitanika s područja grada Knina i okolice. Temeljem anketnog istraživanja ispitanici su dodijelili vrlo dobre ocijene ukrasnim karakteristikama i ugodnosti prisustva A. negundo na krajobraznim površinama Knina. Ponešto su lošije ocijenili ulogu navede vrste u pčelarstvu, šumskim melioracijama i urbanom šumarstvu. Veći broj ispitanika ne zna da je A. negundo vrlo invazivna vrsta. Ash-leaf maple or boxelder (Acer negundo L.) is a deciduous tree that originates from North America. It was imported into Croatia at the beginning of the 20th century. It is highly valued in bee-keeping, forestry and landscape architecture and it is a highly invasive species. Amongst the ornamental characteristics it is important to highlight its tree trunk, tree bark, habitus, branches, leaves, flowers and fruits. Due to its high adaptability it tolerates very poor soils and positions exposed to the sunlight, drought, cold and shade. It is the most widespread in the continental and sub-Mediterranean parts of Croatia. In time A. negundo became considerably widespread and hence, it was considered as an invasive alien species in Croatia. According to the references provided from professional literature, the previously mentioned tree species does not currently do any serious damage to the autochthonous vegetation. Ash-leaf maple (Acer negundo L.) is a sparsely distributed woody species in urban landscape surfaces of Knin, as a solitary tree, in tree lines or in groups of trees. Moreover, using the observation method concerning maintenance and care of A. negundo on landscape surfaces, it was noted that more attention needs to be paid to the formation of the tree top. These trees have not been found outside the urban landscapes. The survey research was conducted in the second half of 2017 on a sample comprising of 50 respondents originating from the city of Knin and its outskirts. Based on the findings of the survey research the respondents gave very good grades to ornamental characteristics and the comfort of the presence of A. negundo on the landscape surfaces of Knin. The role of the previously mentioned tree species received slightly lower grades in bee-keeping, forest meliorations and urban forestry. A considerable number of those surveyed was unaware of the fact that A. negundo is a highly invasive tree species.

Monitoring and mapping of urban trees are essential to provide urban forestry authorities with timely and consistent information. Modern techniques increasingly facilitate these tasks, but require the development of semi-automatic tree detection and classification methods. In this article, we propose an approach to delineate and map the crown of 15 tree species in the city of Duhok, Kurdistan Region of Iraq using WorldView-2 (WV-2) imagery. A tree crown object is identified first and is subsequently delineated as an image object (IO) using vegetation indices and texture measurements. Next, three classification methods: Maximum Likelihood, Neural Network, and Support Vector Machine were used to classify IOs using selected IO features. The best results are obtained with Support Vector Machine classification that gives the best map of urban tree species in Duhok. The overall accuracy was between 60.93% to 88.92% and κ-coefficient was between 0.57 to 0.75. We conclude that fifteen tree species were identified and mapped at a satisfactory accuracy in urban areas of this study.

The Norway maple, Acer platanoldes, was in- troduced into the United States about 1756 after being cultivated in England since 1683. This species remained in relative obscurity in the U.S. until the mid- to late-1800's, but is now one of the most popular urban trees. In certain regions of the United States, Norway maples dominate street tree populations and commonly escape to compete with native species. The extensive use of this species in North America has led to various problems across its new range. Some of these problems may be overcome by future introductions from its native range in Eurasia. L'erable de Norvege, Acer platanoides, etait introduit aux Etats-Unis vers 1756 apres avoir ete cultive en Angleterre depuis 1683. Cette espece restait dans une relative obscurite aux Etats-Unis jusque vers la mi a la fin du 18" siecle, mais est maintenant une des plus populaires parmi les arbres urbains. Dans certaines regions des Etats-Unis, les erables de Norvege dominen...

Municipal administrations devote large budgets in order to preserve the integrity of their urban forests. However, urban ecological conditions are extreme for tree growth and survival. Strict management is therefore mandatory but critical information is missing on procedures that would provide for successful planting and growth. The empirically acquired knowledge of practitioners must be captured into computerised models to improve