Soil,Vegetation, and Seed Bank of a Sonoran Desert Ecosystem Along an Exotic Plant (Pennisetum ciliare) Treatment Gradient
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Ecological conditions following removal of exotic plants are a key part of comprehensive environmental management strategies to combat exotic plant invasions. We examined ecological conditions following removal of the management-priority buffelgrass (Pennisetum ciliare) in Saguaro National Park of the North American Sonoran Desert. We assessed soil, vegetation, and soil seed banks on seven buffelgrass site types: five different frequencies of buffelgrass herbicide plus hand removal treatments (ranging from 5 years of annual treatment to a single year of treatment), untreated sites, and non-invaded sites, with three replicates for each of the seven site types. The 22 measured soil properties (e.g., pH) differed little among sites. Regarding vegetation, buffelgrass cover was low (≤1 % median cover), or absent, across all treated sites but was high (10–70 %) in untreated sites. Native vegetation cover, diversity, and composition were indistinguishable across site types. Species composition was dominated by native species (>93 % relative cover) across all sites except untreated buffelgrass sites. Most (38 species, 93 %) of the 41 species detected in soil seed banks were native, and native seed density did not differ significantly across sites. Results suggest that: (1) buffelgrass cover was minimal across treated sites; (2) aside from high buffelgrass cover in untreated sites, ecological conditions were largely indistinguishable across sites; (3) soil seed banks harbored ≥12 species that were frequent in the aboveground vegetation; and (4) native species dominated post-treatment vegetation composition, and removing buffelgrass did not result in replacement by other exotic species.
KeywordsBuffelgrass Ecological condition Native species Recovery Saguaro National Park Treatment effectiveness
This study was funded by the Natural Resource Preservation Program of the National Park Service through a cooperative agreement between the National Park Service (Saguaro National Park [SNP]) and the University of Nevada Las Vegas (UNLV). We thank Joslyn Curtis (UNLV) for collecting plant community data; Sharon Altman (UNLV) for preparing the figures; and Perry Grissom (SNP), Peter Budde, three anonymous reviewers, and the editorial board for providing helpful comments on the manuscript. Any use of trade names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
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