Title

Age Distributions of Spruce and Fir in Beetle-Killed Forests on the White River Plateau, Colorado

Document Type

Article

Journal/Book Title/Conference

American Midland Naturalist

Publication Date

1970

Issue

1

Volume

83

First Page

206

Last Page

212

Abstract

In the 1940's an epidemic of the Engelmann spruce beetle (Dendroctonus engelmannii Hopk.) killed almost all the spruce (Picea engelmannii (Parry) Engelm.) and most of the fir (Abies lasio- carpa (Hook.) Nutt.) larger than 10 cm in diameter breast height, on the White River Plateau, in northwest Colorado. Reconstruction of the age distributions of spruce and fir at the time of the beetle attack were made by counting all the dead trees, stumps and live trees in two stands and estimating the ages of these trees at the time of the beetle attack. The resulting age distributions indicate a reduction in spruce reproduction in the late 1700's, while fir reproduction was relatively unchanged. An epidemic of Engelmann spruce beetles in the early 1700's is suggested to explain these age distributions. Fire, climatic change, or grazing and trampling by cattle are less likely hypotheses.