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New Innovations in Native Forest Restoration for High-Elevation Rangelands

CIG Projects in PIA | Pacific Islands Area NRCS
 CIG Projects in the Pacific Islands Area:

New Innovations in Native Forest Restoration for High-Elevation Rangelands Infested with the Noxious Weed Kikuyu Grass (Pennisetum Clandestinum)

Grantee: University of Hawaii

Ranching is the largest land-use industry in Hawaii with close to 1 million acres of rangeland dedicated to cattle grazing. Much of these areas were once koa and ohia forests, but were cleared over 100 years ago to expand grazing areas. Kikuyu grass is native to the highlands of Kenya and was introduced into Hawaii around 1924 as a forage species, which has become very successful in adapting to these high-elevation rangelands, thus making it the most dominant vegetation in many of these grazing systems. Since then, kikuyu grass has become listed as a federal noxious weed due to its aggressive habit in occupying landscapes and displacing other beneficial vegetation. In recent times, large portions of Hawaiian rangelands have been deactivated from grazing operations and designated for native forest restoration. Within two years of cattle removal, kikuyu grass can maintain over 20 tons of biomass per acre, making it difficult for the forest species to compete and survive. Current strategies for koa restoration rely on out-planting young seedlings or germinating the soil seed bank through soil scarification. In either case there are no established protocols for post-plant management for controlling kikuyu grass competition and maximizing koa growth.

Collaborative research between CTAHR and USFS that is being conducted on Mauna Kea has recently determined that a post-plant strategy, which utilizes selective herbicide and fertilizer applications, is a viable strategy in maximizing koa productivity. Grass control had the biggest affect on koa growth. Treatment plots receiving post-plant applications of the grass selective herbicide Fusilade DX produced koa saplings that were over 3 ft. in height, only 8 months after transplant, and were twice as large as koa saplings established in untreated control plots. This early growth productivity exceeds productivity in most conventional operations. Based on these results, this technology could readily be adopted by land managers for reestablishing native forests. We propose to demonstrate the utility of this post-plant strategy under three scenarios:

  1. A native forest restoration area demonstrated on a 10-acre open parcel with koa out-planted by the Hawaii State Department of Hawaiian Home Lands (DHHL).
  2. A silvopasture demonstrated in a 10-acre fenced parcel by integrating prescribed grazing, soil scarification and koa seed bank germination on a private ranch (Umikoa Ranch).
  3. A diversified wildlife habitat demonstrated in a 10-acre fenced parcel by out-planting ohia understory within a koa canopy corridor on the Hakalau Forest National Wildlife Refuge.

These demonstrations will promote innovative conservation technologies that provide: invasive weed management; practices that integrate trees-forage-livestock systems; and increase native plant diversity. Land managers will be encouraged to adopt this technology based on resource availability, cost-savings and ease of implementation.