Landscape-scale spatial patterns of winter injury to red spruce foliage in a year of heavy region-wide injury

Abstract

Red spruce (Picea rubens Sarg.) winter injury is caused by freezing damage that results in the abscission of the most recent foliar age-class. Injury was widespread and severe in the northeastern United States in 2003 and was assessed at multiple elevations at 23 sites in Vermont and adjacent states. This paper presents a spatial analysis of these injury assessments. Relationships between winter injury on dominant and codominant spruce trees and elevation, latitude, longitude, slope, and aspect were investigated with least squares regression and geographically weighted regression. Results of these analyses indicate that injury increased (1) with elevation; (2) from east to west; (3) with the degree to which plots faced west, except at the highest elevations, where injury was uniformly severe; (4) with increases in slope steepness at higher elevations, or with decreases in slope steepness at lower elevations; and (5) with the degree to which plots faced south, except at the highest elevations in northern locations, where injury was uniformly severe. Because injury was greater in areas that have historically received higher levels of acid and nitrogen deposition — western portions of the study region, west-facing slopes, and higher elevations — observed patterns of injury support the hypothesis that acidic and (or) nitrogen deposition act on a landscape scale to exacerbate winter injury. Greater injury on south-facing slopes suggests that sun exposure exacerbates injury or its expression.