A Field-Based Model of the Effects of Landcover Changes on Daytime Summer Temperatures in the North Cascades

Abstract

Removal or reduction of forest landcover has been shown to increase daily high temperatures during the summer in clearcut and young, regrowth forests relative to mature or old-growth forests. Although these temperature differences are easily observed in individual stands, extrapolating the net temperature effect to an actively logged terrain is made difficult by the heterogeneous mixture of stand heights and densities. To study the effect of temperature produced by changes in forest landcover on a regional scale, 13 temperature sensors were placed in structurally different stands in a 15 x 24 km area of the Gifford Pinchot National Forest on the northwest side of Mount Adams, Washington. These sensors operated for 60 days, from July 20, 2008, through September 17, 2008, in snow-free conditions across a range of elevations. Using field data and a previously developed proxy dataset for stand height and density, near-surface daytime air temperature models were developed for the modern and pre-anthropogenic landscapes. Our model results indicate that a 0.7° C average daytime summer temperature difference between the pre-anthropogenic and modern landscapes may be attributed to 20th century reductions in forest cover.

Keywords:

• landcover change
• Cascades
• climate
• glaciers
• surface temperature