Lamoureux, SC, Veneklaas, EJ, Poot, P & O’Kane, M 2016, 'The effect of cover system depth on native plant water relations in semi-arid Western Australia', in AB Fourie & M Tibbett (eds), Mine Closure 2016: Proceedings of the 11th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 567-578, https://doi.org/10.36487/ACG_rep/1608_42_Lamoureux
(https://papers.acg.uwa.edu.au/p/1608_42_Lamoureux/)
Abstract: Cover systems utilising the store and release concept, i.e. evapotranspiration (ET) covers, are reliant on plant transpiration and evaporation to preclude percolation (deep drainage) into waste rock, thus minimising the risk of releasing potentially contaminated seepage. However, attaining persistent plant communities on ET covers is especially challenging in water limited environments. Soil texture permitting, greater water storage may be achieved through increased cover thickness. This study quantified cover material water dynamics, growth, and water use of native Australian plants over one year to determine if differences in plant performance were associated with species, plant available water, and cover thickness on a 1.5 year old irrigated ET cover in a semi-arid region. Plant height growth varied between species but not with cover thickness. Average transpiration per unit leaf area and stomatal conductance (gs) were 1.2 and 2.3 times higher in winter than in summer, respectively, and tended to be higher on thicker covers for both seasons. Overall, transpiration rates were positively correlated with soil volumetric water content (VWC, average from 0.0–0.3 m), but differed between species. Transpiration tended to increase with VWC, gs, and cover thickness (0.7 > 0.5 > 0.3 m), indicating plant (stomatal) control of transpiration in response to drought stress associated with cover thickness. The analysis suggests that plants on thicker covers transpired at greater rates due to access to stored water at greater depths, resulting in higher overall transpiration. This work demonstrates the importance of quantifying water use differences between species, seasons, and cover thicknesses during cover system modelling and design phases. It also highlights the potential for greater plant available water by increasing cover thickness, aiding the establishment of self-sustaining plant communities on ET covers.
Keywords: transpiration, water-relations, revegetation, cover systems, cover depth