Arboriculture & Urban Forestry 46(3): May 2020 and grass species will most accurately elucidate the effectiveness of cooling through shade and vegetation. CONCLUSIONS These results support the importance of turf in cool- ing urban areas and mitigating the UHI. Furthermore, they confirmed that many small green plots will be more effective than the implementation of larger green spaces. However, it is noteworthy that grasses tend to be highly susceptible to drought and unhealthy turf- grasses will not be able to contribute to the cooling effect (Bohnenstengel et al. 2011). Conversely, trees have deeper root systems and are expected to be more resistant to drought (Engelbrecht and Kursar 2003). Therefore, trees will be an ideal replacement for turf in urban conditions where foot traffic is high or when vehicular loading requirements must be met. From a city perspective, trees would be considered more effective than turf at providing cooling simply on the basis that the area of shading especially for large, mature specimens will be far larger than the actual footprint of the tree (Bohnenstengel et al. 2011). The presence of tree canopies and green roofs in urban cities is important as it impacts on human thermal comfort and can help mitigate the effects of UHI (Middel et al. 2015). For example, studies in Singapore have shown that in highly built-up areas, the temperature was on average 7 °C warmer than rural areas. This warmer temperature is generally brought about by the heat emitted from vehicles and air conditioning units. Apart from trees and grasses, research has shown that plants cladded to the façade of buildings and reflective roofs can improve outdoor thermal comfort (within a 4-m radius)(Cheng et al. 2010). By contrast, other reports have shown that trees may not be the most ideal option in improving outdoor thermal comfort. This is because they tended to reduce wind speeds and increase humidity (Mochida and Lun 2008). The reality, however, is that as ambient temperatures rise beyond 28 °C (in the tropics), people will seek shade to reduce the dis- comfort brought about by heat (Wong and Yu 2005). Our findings here have showed that shading can reduce globe temperatures by 5 °C and surface tem- peratures by 5 to 12 °C. This is good evidence to sup- port the role shade from trees will have in improving outdoor thermal comfort. Additionally, the combined effects of turf and shade will yield the most ideal out- come for mitigating the UHI effect. 241 Lastly, similar studies should be conducted in tem- perate regions for comparative analysis. It is also important to consider the tree species used to maxi- mise the potential for shade (e.g., wide-spreading and dense canopies over those that produce small and sparse foliage). In addition, future work may wish to consider the requirement for fast-growing species (Wang et al. 2016). We noted that there had been little research focused on the shadow cast by various trees as well as those from buildings in urban areas. These are important, as they can have an impact on localised cooling, and work in these areas should be considered in future studies. LITERATURE CITED Abreu-Harbich LV, Labaki LC, Matzarakis A. 2015. Effect of tree planting design and tree species on human thermal comfort in the tropics. Landscape and Urban Planning. 138:99-109. Armson D, Stringer P, Ennos AR. 2012. The effect of tree shade and grass on surface and globe temperatures in an urban area. Urban Forestry & Urban Greening. 11(3):245-255. Arnfield AJ. 2003. Two decades of urban climate research: a review of turbulence, exchanges of energy and water, and the urban heat island. International Journal of Climatology. 23(1):1-26. Bastiaanssen WGM. 2000. SEBAL-based sensible and latent heat fluxes in the irrigated Gediz Basin, Turkey. Journal of Hydrology. 229(1-2):87-100. Bohnenstengel SI, Evans S, Clark PA, Belcher SE. 2011. Simula- tions of the London urban heat island. Quarterly Journal of the Royal Meteorological Society. 137(659):1625-1640. Bowler DE, Buyung-Ali L, Knight TM, Pullin AS. 2010. Urban greening to cool towns and cities: a systematic review of the empirical evidence. Landscape & Urban Planning. 97(3): 147-155. Chang CR, Li MH, Chang SD. 2007. A preliminary study on the local cool-island intensity of Taipei city parks. Landscape & Urban Planning. 80(4):386-395. Cheng CY, Cheung KKS, Chu LM. 2010. Thermal performance of a vegetated cladding system on façade walls. Building and Environment. 45(8):1779-1787. Chow TLW, Akbar SAA, Heng SL, Roth M. 2016. Assessment of measured and perceived microclimates within a tropical urban forest. Urban Forestry & Urban Greening. 16:62-75. Denia S. 2015. National action plan on climate change adapta- tion. National Development Planning Agency, ACCCRN Regional network Asia, Indonesia. www.acccrn.net/ resources/national-action-plan-climate-change-adaptation Elmes A, Rogan J, Williams C, Ratick S, Nowak D, Martin D. 2017. Effects of urban tree canopy loss on land surface tem- perature magnitude and timing. ISPRS Journal of Photogram- metry and Remote Sensing. 128:338-353. Engelbrecht BM, Kursar TA. 2003. Comparative drought-resistance of seedlings of 28 species of co-occurring tropical woody plants. Oecologia. 136(3):383-393. ©2020 International Society of Arboriculture
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