Impacts of flowering trees on climate change in metropolitan areas

The warming of our metropolitan areas is influenced by the urban heat island effect caused by removal of trees and replacing these with roads, parking lots, buildings and other aspects of a human-dominated landscape (Primack and Higuchi, 2008). Therefore there is a rising interest in understanding how plants, communities and ecosystems respond to global climate change and urban climate modifications (Neil, et. al., 2010). One of the most practical solutions is to plant flowering trees and trees in general which are important for aesthetic functions, reduction of solar radiation and regulation of air temperature, wind and humidity. The high demand for planting materials of flowering trees is beset by the unavailability of easy and fast methods of vegetative propagation for mass production. Eight flowering trees suitable for urban landscapes were tested: African tulip (Spathodea campanulata P. Beauv.), Dwarf Banaba (Lagerstroemia floribunda Linn.), Golden shower (Cassia fistula Linn.), Native Banaba (Lagerstroemia speciosa (L.) Pers.), Palawan cherry (Cassia x 'Palawan Cherry'), Palosanto (Triplaris cumingiana), and Yellow Antsoan. Seven pre-sowing treatments were tested: Control (Tsub1), soaked in distilled water, 24hr (Tsub2), soaked in hot water, 40 deg C, 1hr (Tsub3), refrigerated, 15 deg C without water, 1 wk. (Tsub4),refrigerate, 15 deg C with water (Tsub5); soaked in acid, 1 min. (Tsub6); soaked in water, 24hr. + 24hr. air drying (Tsub7);hard coated seeds,scarified/clipped (Tsub8); hard coated seeds, scarified/clipped + GAsub3, 30min. (Tsub9); and GAsub3,24 hr. (Tsub10). Palawan cherry and Palosanto had high percentage germination in all treatments. Germination was high for yellow Antsoan and Palawan cherry when seeds were scarified/ clipped. Germination was good for golden shower seeds in Tsub8, Tsub9, Tsub6 and Tsub7. Poor germination was observed in African tulip, Native Banaba and Dwarf-Banaba in all pre-sowing treatments. The best seedling growth in terms of root and shoot growth was obtained in two growing media namely, garden soil and equal parts of garden soil and sand. African tulip showed good rooting response and growth performance in both mature cuttings and young shoot tip treated with indole butyric acid (IBA) and napthalene acetic acid (NAA) and grown in sterilized garden soil +coconut coir dust (1:1) and floral foam. Yellow Anstoan and Palosanto showed slight positive response to IBA and NAA but with low rooting percentage. The study revealed that propagation of flowering trees is highly dependent on pod maturity, seed moisture content and dormancy, pre-sowing treatments, post-harvest handling of seeds and type of sowing medium. For vegetative method of propagation, sources of planting material, age and size of cuttings, planting position, growing media and use of growth regulators for rooting of cuttings, are important considerations. Furthermore, seed germination and rooting of cuttings differed among the species of flowering trees. Finally, nursery management of the flowering trees is an important aspect that should be thoroughly studied.