Spontaneous dynamics and wild design in green roofs

Green roofs and other constructed environments represent novel ecosystems, yet have potential to contribute to biodiversity conservation goals. Constructed ecosystems are intentionally managed to produce specific services, and thus could be viewed as highly artificial or controlled. Yet all constructed ecosystems exhibit spontaneous dynamics, as community structure changes due to internal or external ecological processes. While all green roofs have some element of design and human control over ecological trajectories, the level of ongoing management can vary greatly. I discuss “wildness” as a characteristic of green roofs in response to their spontaneous dynamics after initial setup, and their potential to provide ecosystem services related to human psychological well-being, aesthetics and habitat for biodiversity. This approach suggests new design possibilities in interaction with spontaneous ecosystem dynamics and highlights a need for greater ecological understanding of green roof systems.

Multi-species plant systems for wastewater quality improvements and habitat enhancement

The use of macrophytic plants for the treatment of municipal wastewater is growing rapidly. The Constructed Ecosystems Research Facility (CERF) is a joint project of the Pima County Wastewater Management Department and The University of Arizona's Office of Arid Lands Studies. The facility consists of five 30-mil-hyperlon-lined raceways measuring 61 m long, 8.2 m wide, and 1.4 m deep and one slightly larger raceway. Research has been and is being conducted with aquatic plants such as water hyacinth (Eichhornia crassipes), duckweed (Lemna spp.), giant reed (Arundo donax), bulrush (Scirpus olneyi), black willow (Salix nigra), and cottonwood (Populus fremontii). Composite water samplers are used to collect refrigerated samples from incoming secondary wastewater from Pima County's Sewage Treatment Facility and from the effluent leaving each raceway. Water samples have been analyzed for parameters such as pH, BOD5, and total nitrogen. Microbiological studies have concentrated on the removal of indicator coliform bacteria, as well as Giardia, Cryptosporidium and viruses from the wastewater. Data from the water quality studies indicate that these constructed ecosystems reduce BOD5 consistently to below the 10 mg/L BOD5 tertiary standard, remove nitrogen as well as decrease the concentration of pathogens significantly.