Natural colonization of a 30-year-old landfill located in the Mojave Desert provided data for designing evapotranspirative landfill covers. Abundance, diversity and distribution of all perennial plants were estimated on two naturally recruited Mojave Desert shrub communities on adjacent undisturbed and 30-year-old disturbed landfill sites. Estimates for density (plants m-2), diversity (species m-2), canopy heights, (cm) areas (m2) and volumes (m3) by species and by site were based on measurements from > 900 plants located in 9 (60 × 5 m) transects. Estimates for above and below ground biomass (g plant-1 and g m-2) were based on harvesting 32 whole plants. The best-fit (greatest r2) allometric linear or non-linear equation using height, area, or volume as the independent variable was chosen to predict biomass. A general linear model was used to test hypotheses about differences in measures of community structure related to three levels of disturbance within the landfill. Plant density on the native site (0.51 ± 0.05 plants m2) was significantly greater than on the landfill site (0.28 ± 0.03 plants m2) and within the landfill were was no significant difference among disturbances levels. Percent mortality and species diversity on the native site (13.0% and 0.08 species m-2, respectively) were not significantly different than on the overall landfill (23.0% and 0.07 species m-2). Percent canopy cover and biomass on the native site (12.7% and 304.5 g m-2, respectively) were significantly greater than on the landfill site (9.0% and 214.0 g m-2, respectively). Among the three dominant shrub species, Hymenochlea salsosla had a significantly lower shoot/root ratio (2.09) than Atriplex polycarpa (2.75) and Chrysothamnus nauseosus (3.84) and soil compaction on the landfill reduced rooting depths and increased shoot/root ratios. Changes in community structure will have impacts on the potential for landfill designs incorporating native communities to meet compliance standards.
