Oak woodland restoration: understory response to removal of encroaching conifers

Thin trees within forests: effects on understory plants

A replicated, controlled study in 2001-2005 in temperate mixed forest in Washington State, USA (Devin, Harrington & Peter 2007) found that conifer cutting increased cover of non-native, but not of native plants under Oregon white oak Quercus garryana canopies. Under oak canopies cover of non-native forbs (conifer cut: 10%; uncut: 7%), grasses (conifer cut: 24%; uncut: 12%) and woody plants (conifer cut: 20%; uncut: 9%) was higher under conifer cut oaks. There was no difference between treatments for cover of native forbs (conifer cut: 30%; uncut: 35%), grasses (conifer cut: 7%; uncut: 5%) and woody plants (conifer cut: 127%; uncut: 128%), or total plant cover under Oregon white oak canopies (99% under both conifer cut and uncut oak trees). Data were collected in 2005 under six conifer cut (all conifer covering the oaks cut in 2001) and six control Oregon white oak trees (average height: 16 m, average crown diameter 7.5 m) at each of four forest sites.