The ecological function of constructed sites like roadsides, parklands, utility right-of-ways, storm-water features and lawns is often compromised by plant palettes constrained by horticultural availability, plant familiarity, or a simple design aesthetic. Furthermore, constructed landscapes designed with poorly- adapted species and low plant diversity may be more prone to undesirable plant invasion, may take longer to establish, and require higher more resources for maintenance. The Sustainable Sites Initiative, a collaborative effort of several national organizations, is developing a rating system to help recognize practices which maximize ecosystem services and improve sustainability of constructed landscapes. For example, the 50 million acres of turf grasses in both commercial and residential applications represent the primary irrigated crop in the United States absorbing up between 30% and 60% of potable urban water. Lawns alone annually consume 67 million pounds of pesticides, 70 million tons fertilizer, as well as 300 million gallons of gasoline producing 5% air pollutants in the United States. This industrialization of lawns over the last 40 years has developed due to aesthetic expectation, availability of resources, and frequent use of inappropriate plant species. As an alternative, we hypothesized that using multiple-species assemblages comprising regionally native species could still reach design expectations of turf grasses, while also complying with sustainable practice guidelines. We tested establishment rates, leaf density, compaction disturbance, and weed infestation of high performance standard (southern US) non-native turf grass (bermudagrass: Cynodon dactylon) against low, medium and high diversity regionally native mixes.
Results/Conclusions
Establishment of native mixes exceeded non-native species by 100% at 60 day (F=22.06; p<0.001) and 90 day (F=14.08; p<0.001) day post-sowing. By the end of the first growing season, the low native diversity plots had similar coverage to non-native, but the high diversity mix exceeded these by 20% (F=6.50; p<0.001). Furthermore, leaf area indices, a surrogate for many ecosystem processes, of the native mixes were between 40-60% higher than non-native (F=13.70; p<0.001) and required lower mowing rates to maintain it. We suggest that these performance outcomes are a consequence of the underlying ecological stability of high diversity native plant assemblages as well as the individual physiology and ecological niche space of individual species. The performance attributes, direct environmental and economic savings, and inferred improvement of ecosystem, justify the investigation and application of xeric, mesic and hydric native plant assemblages systems for lawns and other turfgrass applications for all climatic zones.
