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Individual Highlight

Repeatedly Air-Root-Pruned Container Stock Out-performs Bare-root Planting Stock after 10 Years

Photo of Fourteen-year-old oaks planted as repeatedly air-root-pruned container stock on mounds on a frequently flooded site high in clay with poor internal drainage. Jerry Van Sambeek, U.S. Department of Agriculture Forest Service.Fourteen-year-old oaks planted as repeatedly air-root-pruned container stock on mounds on a frequently flooded site high in clay with poor internal drainage. Jerry Van Sambeek, U.S. Department of Agriculture Forest Service.Snapshot : Repeated exposure of tree roots to air, known as air-root-pruning, provides swamp white oak seedlings that continues to out-perform nursery bare-root planting stock after 10 years.

Principal Investigators(s) :
Van Sambeek, J.W."Jerry" 
Research Location : Plowboy Bend, Calif., Cuivre Island, Calif., and Horticulture and Agroforestry Research Center
Research Station : Northern Research Station (NRS)
Year : 2016
Highlight ID : 947

Summary

Repeatedly air-root pruning container-grown stock (periodically transplanting from small open-bottom containers to progressively larger open-bottom containers during the growing season) has the potential to produce seedlings that within one growing season grow taller and larger in basal diameter and have root system than seedlings produced as bare-root planting stock in forest nurseries. Earlier research identified an initial growth advantage from air-root pruning; new Forest Service research evaluated tree height, diameter, and green weight of swamp white oak after 10 years at three sites where both stock types were planted. On two sites that were less than ideal for oak, tree green weights from repeated air-root-pruned stock had 2.8 to 4.1 times greater green weight than trees from bare-root stock. On an upland site with deep loess soils, there was a trend for swamp white oak trees from container stock to be slightly larger than trees from bare-root stock although differences were still found for black and white oak. Repeated air-root-pruning produces lateral roots immediately below the root collar (often lacking on bare-root planting stock ) that contribute to faster seedling stem growth and the fibrous root ball necessary to be competitive on harsh or less than ideal oak sites.

Forest Service Partners

External Partners

 
  • University of Missouri Center for Agroforestry