干旱区生态环境知识资源中心

Germinable seed in the soil seed bank and vegetation were characterized at a former uranium mill site in the Great Basin desert, Arizona, 10 years after a remediation program was conducted to remove surface contamination and revegetate the site. The objective of the study was to evaluate the effectiveness of reseeding as routinely practiced to revegetate such sites. Three different conditions at the sire were evaluated: (1) an area that had been blades to remove topsoil then reseeded with exotic and native species and fenced to exclude livestock (ungrazed-bladed-reseeded) (2) a control area inside the fence that had not been bladed or reseeded (ungrazed), and (3)for further comparison, an area outside the fence that was undisturbed by the milling and remediation efforts but has received normal grazing pressure (grazed). Each condition was represented by three plots,from which soil samples and transect data were collected. The diversity of species and total number of viable seeds in the seed bank (top 5 cm of soil) were lowest in the ungrazed-bladed-reseeded plots (P < 0.05). These plots also had lower plant cover (15%) than the ungrazed plots (24%) (P < 0.05), comparable to the cover on, grazed plots (11%), even after 10 years of grazing exclusion. We conclude that at this site the results of topsoil removal and replacement were not effectively remediated by reseeding. Although these methods may be effective in moister climates, more intensive efforts to reintroduce vegetation may be required in desert sites such as this.