PARENT SESSION
Poster Session 35: Restoration Ecology.

Thursday, August 5 Presentations from 5:00 PM to 6:30 PM, Exhibit Hall A 1.

Using native vegetation for water extraction on landfill covers.

Forman, Amy^*,1, ¹ S.M. Stoller Corporation, Idaho Falls, ID, USA

ABSTRACT- In semiarid regions, where potential evapotranspiration greatly exceeds precipitation, it is theoretically possible to preclude water from reaching interred wastes by providing a sufficient soil cap to store precipitation that falls while plants are dormant and, by establishing sufficient plant cover to deplete soil moisture during the growing season. The Protective Cap/Biobarrier Experiment was established in 1993 to test the efficacy of four evapotranspiration landfill cover designs, planted in two vegetation types, under three precipitation regimes. One objective of the study was to compare water extraction patterns between a crested wheatgrass (Agropyron cristatum) monoculture and a mix of native species. Crested wheatgrasses are native to Europe and Asia and were naturalized in much of the western United States because they establish quickly and are drought tolerant. Consequently, they have been used widely for rangeland reclamation, including stabilization of landfill covers. Because many ecologists have found that diverse plant communities have greater stability and resilience than monocultures, we postulated that a mix of native species will extract soil moisture more thoroughly than a crested wheatgrass monoculture and enhance the functional integrity of a landfill cover. Seven years after establishment, native vegetation plots consistently maintained higher total plant cover than crested wheatgrass plots, and plant cover on native vegetation plots responded to augmented precipitation with greater sensitivity. As a result, end of season soil moisture content was significantly (p<0.05) lower on native vegetation plots than on crested wheatgrass plots in most years of the study, and differences between native vegetation and crested wheatgrass plots in end of season soil moisture were greatest in plots with augmented precipitation. Thus, although plant cover fluctuated more on native plots through time and across precipitation treatment, more thorough water extraction on native vegetation plots enhanced the performance of landfill covers in terms of evapotranspiration.

Key words: landfill cover , Agropyron cristatum , evapotranspiration, semiarid