SEMINAR: Soil&Water Seminar, 11am April5:

The Soil&Water Seminar at 11am on Tues, April 5th, will be given by Willis Gwenzi, from the Soil Physics group at SEE and Plant Biology.All welcome!

------ TITLE: “Vegetation and soil controls on water redistribution on vegetated engineered cover systems associated with mine waste disposal”

----- ABSTRACT: Hazardous wastes from mining operations and mineral processing pose substantial environmental and public health risks. A key strategy to minimize the risks associated with hazardous wastes is the use of vegetated engineered covers based on the ‘store-release’ concept or water balance principles. Covers are artificially constructed ecosystems designed to minimize deep drainage into buried hazardous wastes by enhancing soil moisture storage in the top layers, and subsequent water loss through evapotranspiration. On such systems, vegetation water use directly contributes to cover hydrology, and conversely, cover hydrology influences vegetation water use and growth, forming a feedback loop. Material hydraulic properties, rainfall patterns and vegetation characteristics particularly root distribution and leaf area index are fundamental factors influencing vegetation water use and the hydrology of cover systems. Yet until now, a systems understanding of the ecohydrology of covers based on empirical data has been lacking. To this end, we quantified the magnitude and spatial variability of hydraulic properties, root distribution, leaf area index, rainfall patterns and vegetation water use on a sandy cover system in a Mediterranean climate.

The objective of this presentation is to summarize the key findings of this study. First, I will show how material handling and construction procedures influence the magnitude and spatial structure of hydraulic properties, and the distribution of fine roots on cover systems. Second, I will demonstrate how material hydraulic properties, vegetation characteristics (root distribution, leaf area index) and atmospheric drivers collectively impact on daily, seasonal and annual trends of vegetation water use. On an annual basis, the contribution of vegetation water use to the water balance was quite low (22% of annual rainfall), raising doubts about the capacity of such a cover system to achieve its design objective of minimizing the risk of deep drainage. The talk closes with an overview of a dynamical systems analysis, highlighting how vegetation-soil feedbacks and their interaction with climatic fluctuations influence early ecosystem development and vegetation temporal patterns in water-limited ecosystems.

Overall, the insights gained from this study emphasize the need for a quantitative understanding of material properties, vegetation characteristics, rainfall patterns and vegetation water use when designing artificial ecosystems to achieve specific hydrological functions. The findings of this study will be of relevance to a broad audience, including plant ecophysiologists, restoration ecologists, government regulators and environmental practitioners interested in the disposal and management of potentially hazardous wastes.