Meshing Urban Tree Species Selection with the Tropical Urban Environment Roger Kjelgren Dept. Plants, Soils, Climate Utah State University Two Stories • Singapore’s • Singapore’s changing climate green • More intense infrastructure rainfall but • Enrich urban greater dry biodiversity periods A new • Optimize urban • Mitigation, story? adaptation greenspace Köppen-Geiger climate classification map Aw –tropical savanna Am –tropical monsoon Kangar-Pattani line Af –tropical rainforest Altered Urban Environments Surface heating Long wave radiation Understory Shade Urban Climate Already Changed • Singapore’s climate changed a long time ago: urban heat island • Global change accelerates heating….. • …rainfall intensity/dry periods; worsens soil problems Urban Soils/Climate change • Urban soils typically shallow, impeding layers • More variable, intense rainfall – More runoff/less soil recharge/drier…… – …or more saturated Utah ….. Tropical SE Asia 2005-2006 Fulbright Fellow Thailand Kasetsart University • KU Dept. Silviculture – Advise on urban forestry program, conduct research, assisted street tree inventory – Learned tropical forests Monsoonal Forest Types • Dry forest - deciduous during monsoonal dry season • Dry forest – evergreen year round Other Tropical Forests Shoreline/ ocean distributed • Wet evergreen • Mangrove Studied three Bangkok street trees species -Monsoonal dry forest deciduous –Lagerstroemia loudonii (star of India) -Shoreline /ocean distributed- Pterocarpus indicus (angsana) -Monsoonal dry forest evergreen Swietenia macroplylla (mahogany) Three different water strategies Strategies • Star of India (Lagerstroemia) – high water use, but avoids internal water stress • Angsana (Pterocarpus) – low water use and low internal water stress; defoliates when dry • Mahogany (Swiet- enia) low, constant water use, but allows high internal water tress Forest Type Differences • Street tree inventory – Mostly deciduous from SE Asia, S. America – Several sea-shore species • Specimen tree inventory – Found mostly in Buddhist temples – Largely evergreen from SE Asia, including a few Dipterocarpaceae • No wet (equatorial) evergreen, cloud forest, mangrove species Tree Selection for Urban Climates • Urban climates, soils – already selected for most tolerant, adaptable species – Tolerate nursery production • Monsoonal dry forest, seashore species tolerate extreme wet and dry: generalists • What about projected climate change? Projected Climate Change SE Asia • Projected A2 scenarios in Northern Thailand – (Trisurat, Y., R. Alkemade, and E. Arets. 2009. Projecting forest tree distributions and adaptation to climate change In northern Thailand. J. Ecol. Nat. Environ. 1:55-63) • Evergreen species driven to higher, cooler locations • Deciduous species expand lowland habitat – Tropical deciduous species can avoid high temperatures Bangkok Recommended Singapore Leaf Native Street Tree in: Large Urban Tree Species Family Habit Distribution Bangkok Bangalore Tree Albizzia saman Fabaceae D Trop. America - X X Calophyllum inophyllum Guttiferae E Asia X - - Cassia fistula Fabaceae D SE Asia X - - Couruopita guianensis Lecythidaceae D Trop. America - - X Delonix regia Fabaceae D Africa X X - Eucalyptus species Myrtaceae E Australia - X - Hopea odorata Dipterocarpaceae E Asia - - X Jacaranda mimosifolia Fabaceae D Trop. America - X - Lagerstroemia species Lythraceae D Asia X X - Mimusops elengi Sapotaceae E SE Asia X - X Peltophorum pterocarpum Fabaceae D SE Asia X X - Polyalthia longifolia Annonaceae E S Asia X X - Pongamia pinnata Fabaceae D S Asia - X - Pterocarpus indicus Fabaceae D SE Asia X - X Swietenia macrophylla Meliaceae E Trop. America X X - Tabebuia rosea Bignoniaceae D Trop. America X - - Tamarindus indica Fabaceae E Africa X - X Tee, W.S., and L.M. Wee. 2001. Trees of our garden city: A guide to the common trees of Singapore. National Parks Board, Singapore Singapore Trees • “Trees of Our Garden City” – Over 1/3 from monsoonal dry deciduous forests, several more seashore species – Few Dipterocarps – but dominant species in wet evergreen (equatorial) forests – Dipterocarps doing poorly in “fragile” forests, Gardens by the Bay Singapore’s Story City in a Garden with a Changing Climate • What story do you want to tell? – Gardens by the Bay – change climate to suit species; $$$$ – What about gardens not by the bay? Jigsaw puzzle to mesh species adaptation/acclimation with hotter urban climate • Understand urban climate/soils, evaluate forest types • Tell a new story of how species mesh with a changing climate Thank You Questions?.