A constructed treatment wetland provides key urban ecosystem services even in a hot, dry climate
Results/Conclusions: Summer plant biomass typically exceeds 3 kg dw m-2 for the six dominant species (2 species of Typha and 4 species of Schoenoplectus); Typha biomass makes up 80-90% of this. Transpiration rates are highest during the hot summer months, with daytime high temperatures over 45°C and humidity as low as 2%. Summer transpiration rates of 4 – 6 cm water depth day-1 are responsible for nearly 90% of the water deficit for the entire treatment wetland. Chloride content increased an average of 15% along the marsh transects, suggesting that evapoconcentration of solutes driven by plant transpiration is occurring. We estimate that transpiration-driven water losses account for >50% of the total water volume overlying the marsh during hot, dry summer days. Thus, plant transpiration is driving a lateral “tide” that replaces the water overlying the vegetated marsh roughly every two days. This “hydraulic pump” is also drawing nutrients into the marsh, making the Tres Rios treatment wetland more effective at nutrient removal. The hot, arid climate that we hypothesized would present evapoconcentration challenges to nutrient uptake is actually enhancing this ecosystem service.