Biodiversity and ecosystem function in constructed ecosystems.
2008
Ranalli, M. | Lundholm, J.
Constructed ecosystems are engineered to perform functions, such as bioremediation of contaminants, and are increasingly viewed as green alternatives to conventional technologies. Augmenting biodiversity of managed systems such as agroecosystems has been shown to improve yields and other functions such as nutrient uptake, but manipulation of organismal diversity linked to the functioning of constructed ecosystems is an emerging field that has not been reviewed. Here, we summarize current understandings of the relationships between biodiversity and the functions (services) of constructed ecosystems such as green roofs, sewage treatment wetlands and bioreactors, by reviewing theoretical expectations and experimental results. There are several ways in which increased plant species diversity is expected to improve functioning on green roofs. A positive effect of functional composition on water runoff retention has been demonstrated in one system. In wastewater treatment wetland systems, there are a handful of studies showing positive relationships between species diversity and nutrient uptake, but many showing no effect of species diversity. Studies on bioreactors and biofilms suggest that functional redundancy in microbial communities is a consequence of high biodiversity and can promote temporal stability in system performance. The inevitability of variable environmental conditions suggests that the insurance derived from biodiversity is likely important in most constructed ecosystems, but more experimental manipulations of biodiversity are necessary to test whether ecosystem functions can be optimized or stabilized in any system.
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