J. Appl. Sci. Environ. Manage. June. 2016 Vol. 20 (2) 453 – 461
It is well known that urban trees produce various types of benefits and costs (Soares et al., 2011) and most of the environmental benefits associated with urban trees (Semenzato et al., 2011). The importance of tree in urban environment can not be ignored. Street trees are important in the attractiveness of residential streets (Schroeder and Cannon, 1983). Trees help in maintaining the ecological balance. There are numerous other advantages that trees hold water runoff reductions, pollution reduction and climate amelioration (Akbari, 2002; Akbari et al., 2001; Nowak et al., 2002). For every ton of new wood that grows, about 1.5 tons of CO2 are removed from the air and 1.07 tons of life giving oxygen is produced (Whitaker, 2010). Trees also assist in lessening air pollution levels by absorbing pollutants, intercepting particulate matter, and releasing oxygen (Escobedo et al., 2006; Nowak and Crane, 2002). Trees found in the urban environment prevent solar radiation from heating buildings, cool the area through their evapotranspiration, reduce wind speed and reduce the need to use air-conditioning systems (Dimoudi and Nikolopoulou, 2003). Urban conditions are known to affect tree growth. As the ecology of urban systems has been increasing studied, many physical, mechanical, chemical, and human stresses upon urban street trees have been enumerated (Qigley, 2004). Trees typically increase in size by three to four orders of magnitude from the seedling to adult stage (Meinzer et al., 2005). Tree size distributions are changing in many natural forests around the world, and it is important to understand the underlying processes that are causing these changes (Coomes and Allen, 2007).
Measurement of tree size, diameter, circumferences, frequencies, health assessment phenology, age, thickness and growth performances observed by researchers (Alméras et al., 2005; Baker, 1997; Bertram, 1989; Cannell et al., 1988; Cao et al., 2010; Iqbal et al., 1994; Lie et al., 2009; Shafiq and Iqbal, 1999, 2003; Shafiq et al., 2009; William et al., 2007). Comparisons of current and historical tree species composition and size structure along natural productivity gradients are useful for inferring effects of disturbance regimes and productivity on patterns of succession (Surrette et al., 2008). Proper selection of tree size is essential to maximize the efficiency of canopy restoration efforts. Municipal and landscape ordinances often specify the use of large caliper trees, 7.6 cm (2.5 in) or larger, to provide a more substantial impact (Paul, 2008). From tree survey all the valuable information like age, size and kind of trees can be determined. There is important information that must be included in tree survey. This includes reference number of tree, name of the tree either common or specific, height of trees, stem of diameter, age of the trees, structural condition of the trees, management recommendation for the trees, safe useful life expectance of the trees, color coding and categorizing of the trees by letter, removal of trees and also retention of the trees on the base of above data (Jackston, 2010).
Trees commonly suffer under a chronically stressful regime in terms of harsh microclimate and soil conditions and improper care (Jim, 2005). Trees in urban settings play an important role in improving urban life by reducing runoff, air pollution and energy use, and improving human health and emotional well being (Wu et al., 2008). Furthermore, city trees increase the attractiveness of communities, reduce noise, and improve wildlife habitat, while the spaces in which they grow provide many recreational opportunities (Chen and Jim, 2008). Today the many benefits of vegetation within cities are beginning to receive attention in public (Grimm et al., 2008; Manning, 2008). Tree diameters are normally measured at DBH (diameter at breast height), which is 4.5 feet (1.37 m) above the ground. The measurement of tree size as dbh is a very precise measure. Measurement of tree dbh helps in selection of trees having better growth form. The diameter growth of trees may vary depending on the tree size, species and other tree related factors (Nabeshima et al., 2010). Tree diameter at breast height (dbh) has traditionally been the "sweet spot" on a tree where measurements are taken and a multitude of calculations are made to determine things like growth, volume, yield and forest potential. Tree dbh is outside bark diameter at breast height. Breast height is defined as 4.5 feet (1.37 m) above the forest floor on the uphill side of the tree and is the most frequent measurement made by a forester using either a diameter tape or tree caliper (Nix, 2011).
Karachi is the largest industrial city of Pakistan. Trees in cities have an important positive effect on people’s lives. One such positive effect is the amelioration of microclimate (Georgi and Zafiriadis, 2006). In addition to tolerance classifications, tree size (typically reported using diameter at breast height or basal area as a proxy measurement) is commonly used to predict tree growth. The expected growth rate of a tree changes with age and size (Wyckoff and Clark, 2005). The role of the street tree has transitioned from one of beautification and ornamentation to one of environmental service provision over the course of the last 30 years (Seamans, 2013). The urban ecosystem is under increasing scrutiny as society strives to manage the environment in a sustainable way. Urban trees play a critical role in the urban environment on many levels. As we increase our understanding of the complex processes at play in the rhizosphere, we will not only be able to better manage landscape trees, but also more fully benefit from their role in urban ecosystem processes (Day et al., 2010). Height and diameter measurements were taken for silver, sugar and Norway Maple Street trees in Rochester and Syracuse, New York (Nowak, 1990). From the farthest reach of the woody roots to the tips of the twigs, trees expand in girth. This annual growth increment allows trees to respond to changing environmental conditions (Coder, 1996). Tree size is often a necessary piece of information in studies of forest management. It is not only related to age, fire susceptibility, harvest potential, and silvicultural treatment of tree stands, but also to biodiversity and ecological health of the forest environment. It can often be related to specific ecological environments and the biological maturity of those environments (Haynes et al., 2011). The importance of sustainable land use is increasingly emphasized (Gotmark et al., 2009). Human beings are almost fully dependent on flora of the region for their social, economic, ecological and environmental needs.
A comparison of tree sizes with in other studies confirmed the need to extend the knowledge to the behavior of more species and more site specific conditions. The size of trees at maturity and their growth rate have also a considerable importance in guiding planning and design decisions during management practices and helpful for working on the applications to the protection and plantation of tree at these sites. Tree size is an important measure for productivity as well as growth performance of plants in any environment. The determination of tree size with the help of dbh is a common way to get information about tree size. These values often show variation and can be useful for long term studies. There is no information available regarding tree size growing at different sites of Karachi city. Therefore a detailed survey was conducted to study the size of some important street trees (Alstonia scholaris, Azadirachta indica, Bombax ceiba, Cassia fistula, Eucalyptus sp., Ficus benghalensis, Ficus religiosa and Guaiacum officinale) growing in urban site of Karachi city.
Study sites: Karachi is the largest industrial city of Pakistan and is spread over 3,530 km2 (1,360 sq mi) in area. It is situated on the coast of the Arabian sea with a geographic coordinates 24°51′ N 67°02′ E. Chaudhry (1961) has characterized the climate of Karachi as subtropical maritime desert. Average wind velocity is 12 meter sec-1 during June and July and 3.5 meter sec-1 from January to March. During southwest monsoon season wind blows from the sea towards the coast, whereas during the northeast monsoon their direction is reversed. The hot and humid rainy season, which is variable, lasts from June to September. The winter season is short lasting from middle of November to middle of February. The rest of the months constitute the summer, autumn and spring seasons. Temperature is mild with no frost. Dew formation is quite common, the relative humidity is high and the differences in day and night temperatures are great. The study area included main road net work of the city and covered an area of 25 x 25 sq km. Four different sites were selected for the present study in which climatic conditions are not much variable. The sites A, B, C and D included all main traffic networks as M. A. Jinnah Road, University Road (near Hassan Square), North Nazimabad and Karachi University Campus, respectively.
Fig. 1. Alstonia scholaris Fig.2. Azadirachta indica
Fig. 5. Ficus bengalensis Fig. 6. Ficus religiosa
Species description: Alstonia scholaris (Linn.) R. Br. (family Apocyanaceae) is a tall evergreen tree up to 20 m or more (Figure 1). The inner bark is of medicinal value and is used as a source of anti-malarial drug. It is cultivated in Pakistan as an ornamental. Azadirachta indica Adr. Juss. (family Meliacaea), vern Neem is a tree, up to 15 m tall (Figure 2). The tree is cultivated in the warmer parts of the country. It yields good timber. All parts of the plant are medicinal. A native of India and China, it is cultivated and naturalized through-out India, Malaysia and Pakistan. Bombax ceiba Linn., (family Malvaceae), vern. Simbal, Simal, is commonly cultivated as a roadside and garden tree in Pakistan (Figure 3). Cassia fistula Linn. (family Fabaceae), vern. Amaltas tree is up to 20 m tall (Figure 4). The bark in young tree is smooth and ash colored becoming rough and dark brown in old. This species is commonly planted in gardens. An ornamental tree, the bark is used as tanning material and wood ash is used as mordant in dyeing. Various parts of the plant are also reputed to have medicinal properties. Eucalyptus sp. (family Myrtaceae) (Figure 5) and Ficus benghalensis Linn, (family Moraceae) vern. Bargad or Bohar are large, evergreen to deciduous trees and up to 20 m tall (Figure 6). Ficus religiosa Linn. vern. Pipal, Pipli, Doguri is a large or medium sized, evergreen or deciduous tree, 6-15 m tall (Figure 7). It is planted as an avenue or roadside tree and is held sacred by Hindus and commonly planted near Hindu temples in India. The fruits are commonly eaten by birds and in times of famine by human beings. The leaves and twigs are lopped for cattle and goats. The wood is used for packing cases and in sacrificial fires by Hindus. Leaves and tender shoots are used as purgative and in skin diseases. The fruit is laxative, alterative and also has cooling effect (Efloras, 2013). Guiacum officinale L. (family Zygophyllacea) and is a beautiful, small to medium sized tree (Figure 8) of dry tropical forests (Francis, 1993).
Results and disscussion
The variation in dbh was found in all tree species growing at different sites of Karachi city (Table 1). The mean dbh value for A. scholaris, A. indica, B. ceiba, C. fistula, Eucalyptus sp., F. benghalensis, F. religiosa and G. officinale at Karachi University Campus site was recorded as 42.19, 42.17, 33.15, 25.73, 28.91, 28.15, 31.94 and 33.86 cm, respectively. The mean dbh value of A. scholaris, A. indica, B. ceba, Eucalyptus sp. F. benghalensis, F. religiosa and G. officinale at North Nazimabad site was recorded as 24.79, 49.90, 29.45, 65.50 and 41.40 cm, respectively. A. scholaris, B. ceiba, C. fistula, Eucalyptus sp., F. benghalensis, F. religiosa, Eucalyptus sp. and G. officinale registered dbh value in the following order at University Road (near Hassan Square) 24.87, 35.06, 27.00, 21.91, 38.81, 37.69 and 25.90 cm, respectively. A. scholaris, A. indica, B. ceiba, C. fistula, F. benghalensis, F. religiosa, Eucalyptus sp. and G. officinale showed similar trend in dbh values 32.72, 34.55, 20.90, 17.12, 44.10 and 34.16 cm at M. A. Jiunnah Road site, respectively. lowest dbh values at M. A. Jinnah Road as compared to University Road (near Hassan Square), North Nazimabad and Karachi University Campus, respectively. The dbh of G. officinale (34.16 cm) and F. religiosa (44.10 cm) was recorded highest at M. A. Jinnah Road as compared to University Road (near Hassan Square) and Karachi University Campus site. Whereas, Eucalyptus sp. and F. benghalensis recorded highest dbh at North Nazimabad site as compared to M. A. Jinnah Road, University Road (near Hassan Square) Essa Nagri and Karachi University campus, respectively. Eucalyptus sp. and A. scholaris also recorded highest dbh values at Karachi University Campus as compared to all studied sites.
From this study, average tree size of A. scholaris ranged between 24.79 and 42.19 cm, and A. indica ranged between 32.72 and 49.90 cm. Tree size measurements were taken for eight street trees in Karachi city. Eucalyptus sp. proved to be having highest dbh value. Individual tree heights can vary due to differences in climatic, edaphic, and biotic factors such as genetics, age and competition (Kozlowski, 1971). Population viability is determined by vital demographic factors, such as birth, growth and death processes (Schemske et al., 1994). The demographic patterns are important in determining the most crucial stages in the life cycle of a tree species (Ng et al., 2009). An increment in tree size dbh represents more biomass in larger than in small trees, and because large trees generally grew more biomass in absolute terms, average dbh increment is often similar for a large range of tree sizes (Prior et al., 2004; Nouvellon et al., 2010). In urban areas, tree height is an important consideration in deciding what species to plant and/or where to plant them. Considering that many urban tree inventories measure tree diameter (Nowak, 1990). Eucalyptus sp., F. bengalensis, F. religiosa and B. ceiba trees are rated as the most common trees in the urban site of the city. This is preliminary data, which can be used to monitor tree size changes with changing patterns of human disturbance to develop effective management plans for the plantation of tree species in future. The present findings may be helpful for the construction of tree inventory data base. The characteristics and variability of tree diameter distributions were studied in natural and managed old Pinus sylvestris L. dominated forests in the middle boreal vegetation zone of eastern Fennoscandia located in Hame in Southwestern, Finland and the natural stands were located in the Vienansalo wilderness area in northwestern Russia (Rouvinena and Kuuluvainenb, 2005). In natural stands, the mean tree density (tree height > 1.3 m) was found significantly higher compared to managed stands. High variability of tree sizes and stand structures considered as an important diversity feature of naturally dynamic Pinus dominated forests in Fennoscandia (Rouvinena and Kuuluvainenb, 2005), Individuals of plant populations typically vary in size, thus exhibiting various size hierarchies (Weiner, 1985). The next research step in this area should be to carry out periodical measurement of tree size. The publication of tree size data and inventory can be helpful at the time of plantation of such species in the selected area. The data and the ultimate expected dbh of each tree species can be used to create a list of suitable trees. It is important to understand that the species have high dbh value are proving suitable for plantation in other site of the city due to better adaptation to available environmental conditions prevailing in the area. For example, both species of Ficus found ideal conditions for growth at all studied sites. Such studies can be very useful in helping to identify characteristics that can be used to select tree species that are better suited for the plantation on other site of the city. The importance of trees in urban environment is now widely recognized that they too cleanse the particulate air pollution and help to make cities and towns more agreeable places to dwell upon. In urban areas, plantation is ensured in parks, residential localities, street and road avenues and industrial sites as shelter-belts plantation. (Chakre, 2006). A variation in trees size growing in natural populations observed. Understanding this variation in growth is central to forest ecology because of its significance to forest structure and biomass (Coomes and Allen, 2007). The Metropolitan Municipality City of Karachi and other civic agencies are working on a strategy to plant more trees for cleaner and healthier environment. However, only little is known about the relative importance of tree size. In our present findings the variation in tree size of A. scholaris, A. indica, B. ceiba, C. fistula, Eucalyptus sp., F. benghalensis, F. religiosa, and G. officinale was observed. Such variation is an interesting while estimating the tree size of different tree species from different sites of the city. The variation in tree size of all tree species recorded from different sites might be due to underlying edaphic factors. The tree size of A. indica, Eucalyptus sp. and F. benghalensis was markedly less at M. A. Jinnah Road site. The tree size of A. scholaris and G. officinale was recorded less at University Road (near Hassan Square). Similarly, the tree size of B. ceiba was found less at North Nazimabad Road. The tree size of F. religosa and C. fistula was also less at Karachi University Campus. Tree height and trunk diameter are both characteristic dimensions of individual tree size. Tree height is related to ability to intercept light in crowded stands, whereas tree trunk is related to the supporting and absorbing capacity of an individual tree, and is easily measured on site (Kohyama et al., 1990). Literature on the comparison of tree size growing at roadside for Karachi is scanty. The largest and smallest trees size in terms of dbh with in all species and sites were recorded. Tree size thickness can be varying considerably with changes in stem diameter. The size of tree gets thicker as the tree grows. Tree stems generally increase in girth as the plants get older, and diameters are therefore the most appropriate measure for grouping plants into size classes. A. indica, Eucalyptus sp. and F. benghalensis at North Nazimabad site showed large tree size. B. ceiba and C. fistula recorded large dbh at University Road (near Hassan Square). F. religiosa and G. officinale showed large tree size at M. A. Jinnah Road. A. scholaris attained the highest tree size at Karachi University Campus. The performance of urban trees depends upon the ability of their root systems to acquire resources and provide anchorage. However, conditions prevalent in the built environment, such as compacted soils, underground infrastructure, chemical contamination, and excessive heat, create a unique and often unaccommodating environment that may impair root growth and development (Day et al., 2010). Tree height, crown height, crown diameter and stem diameter for 282 trees of the indigenous species Combretum erythrophyllum, Searsia lancea and S. pendulina were measured in the urban forest of the City of Tshwane, South Africa and suggested that the obtained results can be used in forecasting the physical dimensions of these species as a function of time, air pollution uptake, rainfall interception, carbon sequestration and microclimate modification of urban forests (Stoffberg et al., 2009).
Conclusion
The present paper recommends for the complete documentation of tree species growing in city. The findings can be helpful for arboriculturists, environmental scientists, and town planners when working on plantation in the selected area. Much more research on these trees is needed for healthy environment of city. It is, therefore, important not only to record the variations in size of tree within cities, but also need to be carried out periodical studies on the variation in the phonological characteristics of trees of the area. An inventory of all trees growing in the city and especially along the roadside is also suggested.
References
Akbari, H.,
2002. Shade trees reduce building energy use and CO2 emissions from power plants. Environ.
Poll., 116:118-126.
Akbari, H.,
P. Pomerantz and H. Taha, 2001. Cool surfaces
and shade trees to reduce
energy use and improve air quality in urban areas.
Solar Energy, 70: 295-310.
Alméras, T., A. Thibaut and J. Gril., 2005. Effect of circumferential heterogeneity of wood maturation strain, modulus of elasticity and radial growth on the regulation of stem orientation in trees. Trees- Struct. Funct., 19:457-467.
Baker, C., 1997. Measurements of the natural frequencies of trees. J. Exp. Bot., 48:1125-1132.
Bertram, J., 1989. Size dependent differential scaling in branches: the mechanical design of trees revisited. Trees-Struct. Funct., 3:241-253.
Cannell, M.,
J. Morgan and M. Murray., 1988. Diameters and dry weights of tree shoots:
effects of Young's modulus, taper, deflection and angle. Tree Physiol.,
4:219-231.
Cao, S., C.
Xu, H. Ye, Y. Zhan and C. Gong., 2010. The use of air bricks for planting
roadside vegetation: A new technique to improve landscaping of steep roadsides
in China's Hubei Province. Ecol. Engineer., 36 (5):697-702.
Chakre,
O.J., 2006. Choice of eco-friendly trees in urban environment to mitigate
airborne particulate pollution. J. Hum. Ecol., 20(2):135- 138.
Chaudhry, I.I., 1961. The vegetation of Karachi.
Vegetatio, 10:229-246.
Chen, W.Y. and
C.Y. Jim., 2008. Assessment and valuation of the ecosystem services provided by
urban forest, in: Carreiro, M.M., Song Y.C. and Wu, J. (Eds.), Ecology, Planning
and Management of Urban Forests International, Perspective, Springer, New York.
Coder, K.D., 1996.
Tree growth rate: Area increase table. University of Georgia Cooperative
Extension Service, Forest
Resources Unit. The United States Departments of Agriculture and counties of the State Cooperating.
University of Georgia School of Forest Resources. Athens, GA. www.urbanforestrysouth.org/resources/library/tr ee-growth-rate-area-increase -table visited on 10/11/2010.
Coomes, D.A. and R.B. Allen., 2007. Effects of size, competition and altitude on tree growth. J. Ecol., 95:1084-1097.
Day, S.D.,
P.E. Wiseman, S.B. Dickinson and J.R. Harris., 2010. Tree root ecology in the
urban environment and implications for a sustainable rhizosphere. Arboricult.
Urban Forest., 36(5):193-205.
Dimoudi, A., and M. Nikolopoulou., 2003. Vegetation in urban environment: microclimatic analysis and benefits. Energy and Buildings, 35:69-76.
Efloras, 2013. Flora of Pakistan. http://www.efloras.org/ florataxon.aspx? flora_id=5& taxon _id = 220001427 visited on 17th February, 2013.
Escobedo, FJ, D.J. Nowak,
J.E. Wagner, C.L. La Maz,
D.E. Rodriguez
and J. Hernandez., 2006. The socio-economics
and management of Santiago de Chile’s public urban forests.
Urban Forest. Urban Greening, 4:105-114.
Francis, J.K., 1993. Guaiacum officinale L. Lingumvitae. Guayacan. Zygophyllacea.
Caltrop Family. USDA Forest Service, International Institute of Tropical
Forestry, 4p. http://www.treesearch.fs.fed.us/pubs/30349
Georgi, N.J. and K. Zafiriadis., 2006. The impact of park trees on microclimate in urban areas. Urban Ecosyst., 9:195-209.
Gotmark, F, J. Fridman and G. Kempe, 2009. Education and advice contribute to increased density of broadleaved conservation trees, but not saplings, in young forest in Sweden. J. Environ. Manage., 90 (2):1081-1088.
Grimm, N.B.,
S.H. Faeth, C.L. Golubiewski, J. Redman, J. Wu, X. Bai and J.M. Briggs., 2008.
Global change and the ecology
of cities. Science, 319: 756-760.
Haynes, S, B. Schwind and R. Warbington., 2011. Estimation of dominant tree size in coniferous stands using LANDSAT TM Data. http://webcache. googleusercontent. Com / search?q=cache:ovqRFhsrgTUJ:www.fs.fed.us/r 5/rsl/publications/rsmapping/est-tree-sze -with- tm.pdf+tree+diameter+increase&cd=5&hl=en&c t=clnk&source= www.google. com. Visited on 05-02-2011.
Iqbal, M.Z and M. Shafiq., 1999. Impact of auto vehicular exhaust on some roadside trees during different seasons. Proc. Pak. Acad. Sci., 36(2):135-141.
Iqbal, M.Z.,
M. Shafiq and S.F. Ali., 1994. Effect of automobile pollution on seed weight
and branch length of some plants. Turk. J. Bot., 18(6):475- 479.
Jackston, P., 2010. Importance of tree survey. http://www.articlesbase.com/agriculture- articles/importance-of-tree-survey-3843697.html retrieved
on 13-02-2011.
Jim, C.Y.,
2005. Monitoring the performance and decline of heritage trees in urban Hong
Kong. J. Environ. Manage., 74:161-172.
Kohyama, T., T. Hara and Y. Tadaki., 1990. Patterns of trunk diameter, tree height and crown depth in crowded Abies stands. Anna. Bot., 65:567-574.
Kozlowski,
T.T., 1971. Growth and Development of Trees. Vol. 1. Academic Press, New York,
NY. 443 pp.
Lie, M.H., U. Arup, J. Grytnes
and M. Ohlson., 2009. The
importance of host tree age, size and growth rate as determinants of epiphytic
lichen diversity in boreal spruce forests. Biodiv. Conser. 18 (13):3579-3596.
Manning, W.J., 2008. Plants in urban ecosystems: essential role of urban forests in urban metabolism and succession toward sustainability. Int. J. Sustain. Develop. World Ecol., 15:362-370.
Meinzer, F.C., B.J. Bond, J.M. Warren and D.R. Woodruff.,
2005. Does water transport scale universally with tree size? Funct. Ecol.,
19:558- 565.
Nabeshima, E., T. Kubo and T. Hiura., 2010. Variation in tree diameter growth in response to the weather conditions and tree size in deciduous broad- leaved trees. Forest Ecol. Manage., 259 (6):1055- 1066.
Ng, K.K.S., S.L. Lee and S. Ueno., 2009. Impact of selective logging on genetic diversity of two tropical tree species with contrasting breeding systems using direct comparison and simulation methods. Forest Ecol. Manage., 257(1):107-116
Nix, S., 2011. D.B.H. (Diameter Breast Height). http://forestry.about.com/cs/ glossary/ g/dbh.htm retrieved on 10-04-2011.
Nouvellon,
Y., J. Laclau, D. Epron, A. Kinana, A. Mabiala, O. Roupsard, J. Bonnefond, G. LeMaire,
C. Marsden, J.
Bontemps and L. Saint-Andre., 2010. Within-stand and seasonal variations of
specific leaf area in a clonal Eucalyptus plantation in the Republic of Congo.
Forest Ecol. Manage., 259(9):1796-1807.
Nowak, D.J., 1990. Height diameter relations of maple street. J. Arboricult., 16(9):231.235.
Nowak, D.J.
and D.R. Crane., 2002. Carbon storage and sequestration by urban trees in the
USA. Environ. Poll., 116:381-389.
Nowak, D.J., D.E. Crane, J.C. Stevens and M. Ibarra., 2002. Brooklyn’s Urban Forest General Technical Report NE-290. USDA-Forest Service, Delaware, OH.
Paul, R.M.,
2008. The influence of initial tree size on growth, canopy development, and
physiology in the urban environment. MS thesis, Michigan
State University, pp. 122.
Prior, L.D., D.M.J.S. Bowman and D. Eamus., 2004. Seasonal differences in leaf attributes in Australian tropical tree species: family and habitat comparisons. Funct. Ecol., 18:707-718.
Quigley, M.F., 2004. Street trees and rural conspecifics: Will long-lived trees reach full size in urban conditions? Urban Ecosystems, 7:29-39.
Rouvinena, S. and T. Kuuluvainenb, 2005. Tree diameter distributions in natural and managed old Pinus sylvestris dominated forests. Forest Ecol. Manage., 208:45-61.
Schemske, DW, B.C. Husband, M.H. Ruckelshaus, C. Goodwillie, I.M. Parker and J.G. Bishop., 1994. Evaluating approaches to the conservation of rare and endangered plants. Ecology, 75:584-606.
Schroeder, H.W. and W.N. Cannon
Jr., 1983. The esthetic contribution of trees to residential streets in Ohio town. J. Arboricult.,
9(9):237-243.
Seamans, G.S., (2013) Mainstreaming the environmental benefits of street trees. Urban Forest. Urban Greening, 12 (1):2-11.
Semenzato,
P., D. Cattaneo and M. Dainese., 2011. Growth prediction for five tree species
in an Italian urban forest. Urban Forest. Urban Greening, 10:169-176.
Shafiq, M.
and M.Z. Iqbal., 1999. Effects of auto- vehicular exhaust on pods and seeds of
some roadside trees. Ecoprint, 6(1):35-40.
Shafiq, M.
and M.Z. Iqbal, 2003. Effects of automobile pollution on the phenology and
periodicity of some roadside plants. Pak. J. Bot., 35(5):931-938.
Shafiq, M., M.Z. Iqbal, M. Athar and M. Qayyum., 2009. Effects of autoexhaust emission on the phenology of Cassia siamea and Peltophorum pterocarprum growing in different areas of Karachi city. Afr. J. Biotechnol., 8 (11):2469- 2475.
Soares, A.L., F.C. Rego, E.G. McPherson, J.R. Simpson, P.J. Peper and Q. Xiao., 2011. Benefits and costs of street trees, in Lisbon, Portugal. Urban Forest. Urban Greening, 10(2):69-78.
Stoffberg, G.H., M.W. Rooyen,
M.J. van Linde and
H.T. Groeneveld., 2009.
Modeling dimensional growth of three street tree species in the urban forest of
the City of Tshwane, South Africa. Southern Forest: J. Forest Sci., 71(4):
273-277.
Surrette, S.B., S.M. Aquilani and J.S. Brewer., 2008. Current and historical composition and size structure of upland forests across a soil gradient in North Mississippi. Southeastern Naturalist, 7(1):27-48.
Weiner, J., 1985. Size hierarchies in experimental populations of annual plants. Ecology, 66:743- 752.
Whitaker, S.,
2010. Urban trees in Bangalore city: Literature review and pilot study on the
role of trees in mitigating air pollution and the heat Island
effect 2006 - 2007. http://www.secon.in
Williams, V.L., E.T.F. Witkowski and K. Balkwill., 2007. Relationship between bark thickness and diameter at breast height for six tree species used medicinally in South Africa. S. Afr. J. Bot., 73(3):449-465.
Wu, C., Q. Xia and E.G. McPherson., 2008. A method for locating potential tree-planting sites in urban areas: A case study of Los Angeles, USA. Urban Forest. Urban Greening, 7:65-76.
Wyckoff, P.H. and J.S. Clark., 2005. Tree growth prediction using size and exposed crown area. Can. J. Forest Res., 35:13-20.