Development of Northern White-Cedar (Thuja occidentalis L.) Plantations within and outside Deer Yards

Olivier Villemaire-Côté,Luc Sirois,Jean-Claude Ruel

doi:10.3390/f8090326

Olivier Villemaire-Côté, Luc Sirois + Show 1 more

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https://doi.org/10.3390/f8090326

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Abstract

Regional surveys done over the last decades show a clear decline in abundance of Northern white-cedar (Thuja occidentalis L.) throughout its range. A lack of seed trees, difficulties in the establishment of natural regeneration and high browsing pressure caused by increasing deer populations have been identified as plausible causes. Current silvicultural strategies for cedar restoration recommend partial cutting to promote and release natural regeneration, but there is also a need to restore the species in areas where it became absent. Yet, little attention has been given to cedar plantations. This study provides a first characterisation of the effects of competition, silvicultural treatments and deer, moose and hare browsing on planted cedar growth, survival, and stem form. Pure and mixed cedar plantations aged 5–27 years located in Eastern Québec were sampled. Both inside and outside deer yards, planted cedars showed high survival rates and were generally subject to low browsing pressure, but 45% were forked. Cedars showed high growth rates and strong reaction to stand opening. Results suggest that at reduced competition levels, a 9-year browser exclusion could be sufficient to establish safe-from-browsing cedar stands of >3 m in height.

Highlights

Northern white-cedar (Thuja occidentalis L., hereafter cedar) is of considerable ecologic value, in part due to its high longevity and shade tolerance [1]
While the recruitment of natural regeneration to height classes above browsing levels can be problematic in the presence of high deer or hare populations, this study shows that cedar plantations established after clearcutting can reach considerable growth rates in the absence of high browsing pressure and competition, and remain vulnerable to browsing for as little as 9 years
Scientific knowledge of cedar is still limited, and more research is needed on the longer term productivity of cedar plantations, as well as on the quality of planted cedar products

Summary

Introduction

Northern white-cedar (Thuja occidentalis L., hereafter cedar) is of considerable ecologic value, in part due to its high longevity and shade tolerance [1]. As it offers palatable winter food, cedar is an important source of winter browse for herbivores such as deer (Odocoileus virginianus Zimmerman; hereafter deer), snowshoe hare (Lepus americanus Erxleben; hereafter hare) and moose Cedar provides browse and protective cover during winter, when snow hampers deer movement, and is as such an important element of deer wintering areas (hereafter deer yards), which are essential to maintain deer populations at the northern limit of their range [3,4]. Its naturally rot-resistant wood is used for value added products such as shingles and outdoor furniture [6]

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