Uneven-aged silviculture in cedar-hemlock-grand fir ecosystems of the northern Rocky Mountains

Abstract

Uneven-aged silviculture is used infrequently in the Northern Rocky Mountains. Because of wildlife, watershed, or scenic issues it is often preferred for managing many stands. While it has been applied in the ponderosa pine (Pinus ponderosa) forests it has had limited application in the grand fir (Abies grandis)-westem redcedar (Thuja plicate)-westem hemlock (Tsuga heterophylla) forests. To supply information for making more informed decisions on using UI).even-aged silviculture in forests dominated by shade-tolerant species, a study was initiated in 1984 in northern Idaho. Twenty-seven stands were treated using classic uneven-aged diameter distributions defined by q-value (1.1, 1.3, 1.5), residual basal area (23, 26, and 35 m2 · ha· 1 ) and target tree size (50 em). This replicated study was evaluated in 1989 and 1996. Grand fir and western hemlock regenerated profusely and suppressed the faster growing western white pine (Pinus monticola) and western larch (Larix occidentalis) that were planted. Even with the dense overstories created with the prescriptions, some natural regeneration of larch and white pine occurred. Both q-value and basal area had significant relationships with the height of white pine and larch. Because of grand fir regeneration, species composition changed little with the uneven-aged prescriptions. The stand structures and composition created by the prescriptions will perpetuate stands containing shade tolerant and disease prone species. Heart and root diseases are common in the stands making them prone to damage by wind, snow, and ice events. Also, because of disease and multiple canopies, the stands created are at high risk for stand replacing wildfires. Even with these concerns the structures created by the uneven-aged prescriptions likely fulfill many societal needs and desires.

Citation

Graham, Russell T.; Jain, Theresa B.; Tonn, Jonalea R. 1999. Uneven-aged silviculture in cedar-hemlock-grand fir ecosystems of the northern Rocky Mountains. In: Emmingham, William H., comp. Proceedings of the IUFRO Interdisciplinary Uneven-aged Management Symposium; 1997 September 15-26; Corvallis, OR. Corvalis, OR: Oregon State University. p. 70-87.