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Enhancing Tree Health in Water Sensitive Urban Design: Role of Mycorrhizae

2018 | Brandon Kyle Winfrey, PhD, Monash University, Australia

In cities, paved roads and buildings prevent the course that rainfall would naturally take, infiltrating into soil and replenishing groundwater. Instead, rainfall becomes “urban runoff,” causing beach closures, stream erosion, algal blooms and impaired water quality in urban streams. Water sensitive urban design (WSUD) systems capture and treat urban runoff that would otherwise impact ecosystem and human health. Stormwater biofilters are one type of WSUD that rapidly infiltrate runoff to the underlying water table. Biofilters rely on healthy vegetation to properly function. Due to the rapid infiltration of runoff, plants in these systems can be more susceptible to drought and often die during extended dry periods. Trees are particularly susceptible during the establishment phase before roots have grown deep enough access the water table. A type of fungus, mycorrhizae, forms a symbiotic relationship with plants in biofilters and can improve the ability of plants to reach otherwise inaccessible water in the soil.

Our study will evaluate the ability of mycorrhizae to improve plant health in stormwater biofilters during extended dry periods. Among a few herbaceous species, we will inoculate two tree species with mycorrhizae: Melalueca ericofolia (swamp paperbark) and Leptospermum continentale (prickly tea-tree), which are native Australian tree species and common in Melbourne biofilters. We will then evaluate the growth of these plants and growth of non-inoculated plants by measuring the photosynthesis on a regular basis. Based on this test, we will select the most appropriate species for a follow evaluation on the effect of mycorrhizae on improving the ability of immature trees to survive and improve water quality following extended dry periods. We expect that our results will help inform management of trees in biofilters during the establishment phase in areas prone to drought or seasonal dry periods, particularly in Australian cities.


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