Revegetation of reed canarygrass infested riparian areas: Performance of pre-vegetated coir after 3 to 6 years

Abstract

Reed Canarygrass (RCG) is an exceptionally aggressive invader of wetlands and streambanks throughout much of North America and a serious challenge in many riparian restoration projects. RCG generally degrades habitat quality, can outcompete most native grasses and forbs, and can sometimes invade stream channels. Over the last six years, we have used pre-vegetated coir mats for rapid bank stabilization and native plant establishment and to thwart reinvasion by RCG. In this paper, we use field experiments, case studies, and literature to evaluate whether aggressive revegetation can defeat RCG. Our results demonstrate that: (1) successful revegetation of infested sites is possible; (2) although RCG can be excluded for several years, even sites with very successful revegetation are not immune to reinvasion and may require periodic management; and (3) major hurdles include incomplete initial RCG control and poorly understood or challenging hydrology. Factors that favor RCG over native herbaceous plants include rapid spread by seed and rhizomes, high competitive ability, strong response to nutrients and disturbance, broad hydrologic tolerances, resistance to herbicides and other control practices, presence of non-native genotypes, and historical or continuing use as a forage or for bank stabilization. Complete control and replacement of RCG is unrealistic. Decisions about goals and effort for RCG control will depend on RCG abundance in the landscape, project purpose, project sponsors' values, regulatory context, and mandated performance criteria. Depending on the location and agency, RCG may be treated as a regulated noxious weed, an undesirable invasive plant with low value in rating biological integrity, not a concern, or a plant suitable for pastures and other uses. Where minimizing RCG is required, time and resources should be allocated to pre-project RCG control, analysis of site hydrology, intensive revegetation practices, large woody plant material, follow-up RCG control, and monitoring for at least 3 years.