The effect of plants on garden microclimates

摘要

IT IS WELL ESTABLISHED that, in principle, well-vegetated areas remain cooler than urbanized and sparsely planted environments. There are two main reasons why vegetation is efficient at cooling its nearby surroundings. Firstiy, plants transpire (i.e.lose water through leaf pores called stomata) and thus actively cool the air, and secondly, plants impose shade, thus causing a cooling effect. By wisely combining and exploiting these two mechanisms, gardeners can enhance the cooling potential of theiroutdoor spaces. As always, however, 'the devil is in the detail'. Plant species differ in their innate ability to transpire (and therefore cool) and also they respond differendy to situations that limit transpiration (such as drought). Some continue to lose water under mild drought (e.g. Choisya ternatd) and others act to decrease then-water loss (e.g. Cotinus coggygrid) (Cameron etal. 2006).