Effect of Vegetation Management and Site Conditions on Volume, Biomass and Leaf Area Allometry of Four Coniferous Species in the Pacific Northwest United States

Carlos Gonzalez-Benecke,Maxwell Wightman,Herman Flamenco

doi:10.3390/f9090581

Abstract

Allometric equations are useful tools for calculating tree and stand-level attributes, such as above-ground biomass or stem volume, using simple measurements that can be obtained from stand inventory data. These equations tend to be species-specific and can be affected by site conditions and silvicultural treatments. Forest vegetation management treatments (VM) are an important component of reforestation programs in the Pacific Northwest of the United States; however, no study has investigated the impact of these treatments on crop tree allometry. In this study we assessed the long-term effects of two contrasting VM treatments on the allometry of sixteen-year-old Douglas-fir, western hemlock, western redcedar, and grand fir trees growing in Oregon’s central Coast Range (CR) and fifteen-year-old Douglas-fir and western redcedar trees growing in Oregon’s Cascade foothills (CF). The VM treatments included a control which received only a pre-planting herbicide application and a VM treatment consisting of five consecutive years of vegetation control after planting. The equations developed in this study were species-specific and were not affected by VM with the exception of western redcedar foliage biomass. For western redcedar, tress of similar diameter had more foliage biomass when growing on plots without VM after planting. The allometry of Douglas-fir and western redcedar was also found to be affected by site, such that trees of similar diameter and height had larger stem volume when growing at the CR site than the CF site. This difference in stem volume was found to be the result of differences in stem tapering. There was a strong relationship between stand basal area and leaf area index that was the same for all species tested and was unaffected by site. The equations presented in this study are useful for calculating stem volume, leaf area and individual tree and component biomass for stands of the studied species that are of similar age.

Highlights

Allometric equations are useful tools in forestry research that allow scientists to estimate a wide variety of variables from stand inventory data
VIB) allometry for 15–16 year old Douglas-fir, western redcedar, western hemlock, and grand fir trees growing under contrasting treatments of vegetation management on sites located in the central Coast
Western redcedar (WRC) and grand fir (GF) trees growing on sites located in the central Coast Range (p > 0.09), data was pooled across vegetation management treatments (VM) treatments

Summary

Introduction

Allometric equations are useful tools in forestry research that allow scientists to estimate a wide variety of variables from stand inventory data. Accurate estimates of forest above-ground biomass are of interest to researchers, forest managers and policy makers as this measure is necessary for determining site productivity and assessing stand and tree growth and yield [1,2]. Allometric relationships exists among tree parts due to physical or physiological interrelations among stem dimensions, crown dimensions, foliage area, and biomass amounts [4]. Understanding these interactions, especially the relationship between tree dimeter and leaf area, is an important component of many mechanistic models of forest growth [5,6]. Brix (1984) [7] demonstrated that fertilizer application altered the relationship between foliage biomass and sapwood basal area for Douglas-fir trees growing in southern Vancouver Island, British Columbia

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Conclusion