Review on the roles and effects of growing media on plant performance in green roofs in world climates

Abstract

Growing media (substrate) is a fundamental part of a green roof, providing water, nutrients and support<br><br>to plants. However, little research has reviewed how it affects plant performances in different climatic<br><br>regions. This study aims to analyse published research on green roof growing medium across world’s<br><br>climate zones. Findings are structured according to Köppen–Geiger climate classification, aiming to investigate the prevalence of research conducted in different climate zones. Results from full-scale studies<br><br>and laboratory or greenhouse experiments were reviewed. The later were included as they provide systematic<br><br>knowledge on the effect of individual factors on system performances although cannot provide<br><br>climate specific information. Studies discussed effects of major substrate components and depths on<br><br>plant survival and establishment using standard test procedures. Results showed that most research in<br><br>the subject were in temperate (group C climate classification), continental (group D) and dry climates<br><br>(group B), respectively. Considerable number of investigations was conducted in controlled laboratory or<br><br>greenhouse environments. Based on the results, future green roof research and guidelines should consider<br><br>climate specifications of the region in designing growing medium, depths and attribute of green roof substrates in order to ensure enhanced plant performance. Especially, for more fragile but less investigated<br><br>dry climate, considerations should be made to tackle heat fluctuations and drought stress by enhancing<br><br>water holding capacity and thermal isolation of the substrate. To move forward, sustainable building<br><br>solutions as a part of future urban forms, climate-adaptive green roof systems should be included into<br><br>future research, practice and guidelines.