Developmental Trends of Black Spruce Fibre Attributes in Maturing Plantations

Peter F Newton

doi:10.1155/2016/7895289

Abstract

This study assessed the temporal developmental patterns of commercially relevant fibre attributes (tracheid length and diameters, wall thickness, specific surface area, wood density, microfibril angle, fibre coarseness, and modulus of elasticity) and their interrelationships within maturing black spruce (Picea mariana(Mill.) B.S.P.) plantations. A size-based stratified random sample procedure within 5 semimature plantations located in the Canadian Boreal Forest Region was used to select 50 trees from which radial cross-sectional xylem sequences at breast-height (1.3 m) were cut and analyzed. Statistically, the graphical and linear correlation analyses indicated that the attributes exhibited significant (p≤0.05) relationships among themselves and with morphological tree characteristics. Relative variation of each annually measured attribute declined with increasing size class (basal area quintile). The transitional shifts in temporal correlation patterns occurring at the time of approximate crown closure where suggestive of intrinsic differences in juvenile and mature wood formation processes. The temporal cumulative development patterns of all 8 of the annually measured attributes varied systematically with tree size and exhibited the most rapid rates of change before the trees reached a cambial age of 20 years. At approximately 50 years after establishment, plantation mean attribute values were not dissimilar from those reported for more mature natural-origin stands.

Highlights

Black spruce (Picea mariana (Mill.) B.S.P.) is a preferred reforestation species used in the establishment of plantations throughout the Canadian Boreal Forest Region [1]
Summary statistics based on 285 permanent growth and yield sample plots established in upland black spruce plantations across boreal Ontario revealed a relatively high level of density-stress within maturing plantations
Strong correlations (r ≥ 0.70) were observed among (1) wood density and the modulus of elasticity which are both related to solid wood products and lumber grades and (2) fibre dimensional attributes associated with pulp yields and paper end-products

Summary

Introduction

Black spruce (Picea mariana (Mill.) B.S.P.) is a preferred reforestation species used in the establishment of plantations throughout the Canadian Boreal Forest Region [1]. Black spruce plantations are an important component of the current and future industrial wood supply and are expected to provide a broad array of ecosystem services over their rotations (sensu [3]). When plantations become overstocked and experience the resultant consequences of lower growth and increased mortality, treatments such as commercial thinning (CT) are expected to be carried out. A number of underlying factors that include the establishment of narrowly spaced plantations and high levels of natural ingress have resulted in an increased occurrence of overstocked plantations across the boreal landscape. Given that a relative density index of 0.5 is the approximate threshold value at which imminent competition mortality or self-thinning is likely to occur [6], many plantations are likely to experience the adverse effects of increased competition which could include the loss of merchantable-sized trees. Forest managers are actively revising their initial crop plans in terms of adding density control treatments, such

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