|Anderson, Jennifer - OREGON STATE UNIVERSITY|
Submitted to: Ecological Monographs
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 14, 2006
Publication Date: June 20, 2006
Citation: Sheley, R.L., Mangold, J.M., Anderson, J.J. Potential for succesional theory to guide restoration of invasive plant dominated rangeland. Ecological Monographs. 2006. 76(3):365-379. Interpretive Summary: Invasive plants dominate and continue to spread throughout millions of hectares of rangeland in the western U.S.A. They alter the structure and function of ecosystems and threaten biological diversity. During the 1990s, invasive weeds cost more than $20 billion in control and lost production in the U. S. Enduring invasive plant management requires restoring diverse plant communities that function in maintaining ecological processes. We tested strategies for restoring weed-infested rangeland within the context of successional management, a process-based framework for describing plant community dynamics. We hypothesized that increasingly modifying ecological processes associated with disturbance, colonization, and species performance would favor the establishment of native grasses. In the fall of 2001, we tested two seeding methods to influence disturbance; three seeding rates of bluebunch wheatgrass, Idaho fescue, and rough fescue to influence colonization; and three herbicide rates and a covercrop to influence species performance on weed-infested rangeland in northwestern Montana. The highest seeding rate combined with no-till drilling produced the highest bluebunch wheatgrass and Idaho fescue density in 2002. These effects persisted into 2004 for bluebunch wheatgrass, but not for Idaho fescue. No-till drill seeding at the lowest rate favored Idaho fescue density, while no-till drilling at the medium rate favored its biomass. Idaho fescue established well after no-till drill seeding with a cover crop and applying 2,4-D. Picloram combined with no-till drill seeding produced the highest density of bluebunch wheatgrass. Herbicides reduced native forbs, increased exotic grasses, but did not affect native grasses. We accomplished our goal of using successional management to direct a weed-infested plant community toward native, desired species, but we did not improve overall species richness. Restoration using successional management may be best implemented iteratively where system community components are systematically repaired or replaced over time.
Technical Abstract: We tested restoration strategies in invasive weed-dominated rangeland within the context of a process-based framework for community dynamics. Our hypothesis was that increasingly modifying the processes influencing disturbance, colonization, and species performance would favor the establishment of native grasses. We quantified the response of species growing in association with Centaurea maculosa and Potentilla recta following successionally-based restoration. We hypothesized that minimal disturbance associated with the seeding methods would not influence on associated species, and treatments that maximized native grass establishment would have the lowest density and biomass of associated species. We also hypothesized that herbicides would increase existing associated native grass density but reduce forb density and species richness. The site lay within a Festuca campestris/ Pseudoroegneria spicata habitat among pothole wetlands dominated by C. maculosa and P. recta. Treatments included three herbicides (none, 2,4-D, picloram) to influence plant performance, two seeding methods (imprinting plus broadcasting, no-till drilling) to influence disturbance, three seeding rates (977, 1,322, 1,557 seeds/m2) to influence colonization, and with and without a covercrop of Triticum aestivum to influence soil N. Treatments were factorially arranged and replicated four times in a randomized-complete-block design in 2001. The highest seeding rate combined with no-till drilling produced the highest grass density in 2002. These effects persisted into 2004 for P. spicata, but not for F. campestris or F. idahoensis. Drill seeding at 977 seeds/m2 favored F. idahoensis density, while no-till drilling at 1,322 seeds/m2 favored its biomass in 2004. Festuca idahoensis established well after drill seeding with a cover crop and applying 2,4-D. Picloram interacted with no-till drill seeding to produce the highest density of P. spicata. Herbicides reduced native forb density and/or biomass, with early season forbs being more sensitive to picloram and summer forbs being more sensitive to 2,4-D. Herbicides increased exotic grasses but had no effect on native grasses. We accomplished our goal of using successional management to direct plant communities toward native desired species, but the treatments used did not improve species richness. Restoration using successional management may be best implemented iteratively where system community components are systematically repaired or replaced over time.