Transpiration and plant water relations of evergreen woody vegetation on a recently constructed artificial ecosystem under seasonally dry conditions in Western Australia

摘要

Understanding transpiration and plant physiological responses to environmental conditions is crucial for the design andnmanagement of vegetated engineered covers. Engineered covers rely on sustained transpiration to reduce the risk of deepndrainage into potentially hazardous wastes, thereby minimizing contamination of water resources. This study quantified temporalntrends of plant water potential (cp), stomatal conductance (gs), and transpiration in a 4-year-old evergreen woody vegetationngrowing on an artificial sandy substrate at a mine waste disposal facility. Transpiration averaged 0.7mmdayu00011 in winter, whennrainfall was frequent, but declined to 0.2mmdayu00011 in the dry summer, when the plants were quite stressed. In winter, thenmean cp was u00010.6 MPa at predawn and u00011.5 MPa at midday, which were much higher than the corresponding summernvalues of u00012.0 MPa and u00014.8 MPa, respectively. The gs was also higher in winter (72.1–95.0 mmolmu00012 su00011) than in summern(<30 mmolmu00012 su00011), and negatively correlated with cp (p<0.05, r2 = 0.71–0.75), indicating strong stomatal control ofntranspiration in response to moisture stress. Total annual transpiration (147.2 mm) accounted for only 22% of the annual rainfalln(673 mm), compared with 77% to 99% for woody vegetation in Western Australia. The low annual transpiration was attributednto the collective effects of a sparse and young vegetation, low moisture retention of the sandy substrate, and a superficial rootnsystem constrained by high subsoil pH. Amending the substrate with fine-textured materials should improve water storage ofnthe substrate and enhance canopy growth and deep rooting, while further reducing the risk of deep drainage during the earlynstages of vegetation establishment and in the long term. Overall, this study highlights the need to understand substrate properties,nvegetation characteristics, and rainfall patterns when designing artificial ecosystems to achieve specific hydrological functions.nCopyright © 2011 John Wiley & Sons, Ltd