Brian D. Harvey

Basing silviculture on natural ecosystem dynamics: an approach applied to the southern boreal mixedwood forest of Quebec

Abstract We present a method in which fundamental knowledge of natural ecosystem dynamics of the southern boreal forest may be used as a basis for a new silvicultural approach aimed at maintaining biodiversity and long-term ecosystem productivity under management. The natural disturbance regime of the southern boreal forest of Quebec is characterized by intense crown fires. Natural forest dynamics following fire on mesic sites involve a gradual replacement of stands of broadleaf species by mixedwood then softwood stands. This succession is accompanied by a decrease in soil fertility and in ecosystem productivity. In the absence of fire, spruce budworm outbreaks contribute in regenerating mature, fir-dominated forests and in reintroducing a hardwood component into stands. Current silvicultural practices promote successive rotations of similarly composed stands. Attaining softwood regeneration following harvest of softwood stands often necessitates site preparation, planting and control of competitive species, including economically and ecologically valuable hardwoods. At the landscape level this strategy may contribute to decreasing stand diversity by favouring replacement of mixedwood stands by hardwood or softwood stands. Natural dynamics indicate that a silvicultural approach favouring species replacement while, at the landscape level preserving a representative proportion of hardwood, mixedwood and softwood stands would be more appropriate. The advantages of such an approach are discussed in comparison with current practices.

Stand-landscape integration in natural disturbance-based management of the southern boreal forest

Forest ecosystem management, based partly on a greater understanding of natural disturbance regimes, has many variations but is generally considered the most promising approach to accommodating biodiversity concerns in managed forested regions. Using the Lake Duparquet Forest in the southeastern Canadian boreal forest as an example, we demonstrate an approach that attempts to integrate forest and stand-level scales in biodiversity maintenance. The concept of cohorts is used to integrate stand age, composition and structure into broad successional or stand development phases. Mean forest age (MFA), because it partly incorporates historic variability of the regional fire cycle, is used as a target fire cycle. At the landscape level, forest composition and cohort objectives are derived from regional natural disturbance history, ecosystem classification, stand dynamics and a negative exponential age distribution based on a 140 year fire cycle. The resulting multi-cohort structure provides a framework for maintaining the landscape in a semi-natural age structure and composition. At the stand level, the approach relies on diversifying interventions, using both even-aged and uneven-aged silviculture to reflect natural stand dynamics, control the passage (‘‘fluxes’’) between forest types of different cohorts and maintain forest-level objectives. Partial and selective harvesting is intended to create the structural and compositional characteristics of mid- to late-successional forest types and, as such, offers an alternative to increasing rotation lengths to maintain ecosystem diversity associated with overmature and old-growth forests. The approach does not however supplant the necessity for complementary strategies for maintaining biodiversity such as the creation of reserves to protect rare, old or simply natural ecosystems. The emphasis on maintaining the cohort structure and forest type diversity contrasts significantly with current even-aged management in the Canadian boreal forest and has implications for stand-level interventions, notably in necessitating a greater diversification of silvicultural practices including more uneven-aged harvesting regimes. The approach also presents a number of operational challenges and potentially higher risks associated with multiply stand entries, partial cutting and longer intervals between final harvests. There is a need for translating the conceptual model into a more quantitative silvicultural framework. Silvicultural Forest Ecology and Management 155 (2002) 369‐385

Silvicultural alternatives to conventional even-aged forest management - what limits global adoption?

BackgroundThe development of forestry as a scientific and management discipline over the last two centuries has mainly emphasized intensive management operations focused on increased commodity production, mostly wood. This “conventional” forest management approach has typically favored production of even-aged, single-species stands. While alternative management regimes have generally received less attention, this has been changing over the last three decades, especially in countries with developed economies. Reasons for this change include a combination of new information and concerns about the ecological consequences of intensive forestry practices and a willingness on the part of many forest owners and society to embrace a wider set of management objectives. Alternative silvicultural approaches are characterized by a set of fundamental principles, including avoidance of clearcutting, an emphasis on structural diversity and small-scale variability, deployment of mixed species with natural regeneration, and avoidance of intensive site-preparation methods.MethodsOur compilation of the authors’ experiences and perspectives from various parts of the world aims to initiate a larger discussion concerning the constraints to and the potential of adopting alternative silvicultural practices.ResultsThe results suggest that a wider adoption of alternative silvicultural practices is currently hindered by a suite of ecological, economic, logistical, informational, cultural, and historical constraints. Individual contexts display their own unique combinations and relative significance of these constraints, and accordingly, targeted efforts, such as regulations and incentives, may help to overcome specific challenges.ConclusionsIn a broader context, we propose that less emphases on strict applications of principles and on stand structures might provide additional flexibility and facilitate the adoption of alternative silvicultural regimes in a broader set of circumstances. At the same time, the acceptance of alternative silvicultural systems as the “preferred or default mode of management” will necessitate and benefit from the continued development of the scientific basis and valuation of a variety of ecosystem goods and services. This publication is aimed to further the discussion in this context.

Augmentation du couvert en peuplier faux-tremble dans les pessières noires du nord-ouest du Québec après coupe totale

Abstract: In the eastern Canadian boreal forest, the term hardwood expansion or encroachment (enfeuillement in French) generally refers to the phenomenon of increasing cover of intolerant hardwoods, notably aspen (Populus tremuloides), following clearcutting. Such expansion is perceived as a local (stand-level) process that is reflected at a larger, regional scale. The objective of this study was to characterize the increase in aspen cover following clearcutting in the clay belt of Abitibi, in northwestern Quebec. Regional data from 3 province-wide forest inventories (1970, 1980, and 1990) conducted by the Quebec Ministry of Natural Resources and Wildlife were analyzed for 2 ecological regions, the Abitibi Plain (western balsam fir-white birch bioclimatic subdomain) and the Matagami Lake Plain (western black spruce-feathermoss bioclimatic subdomain). An assessment was done of forest cover transformations following clearcutting over 3 decades based on time since harvesting, surface deposit/drainage, and ecological region. Results show that mesic clay sites are particularly susceptible to aspen encroachment and that the overall rate of encroachment from the 1970s to the 1990s in the black spruce and balsam fir regions has been about 30%. Moreover, despite the greater abundance of poorly drained and organic sites, less favourable to hardwood establishment, in the more northerly black spruce region, the 2 regions appear to present the same sensitivity (or propensity) to intolerant hardwood expansion. On sensitive sites, management of black spruce forests should include adaptive practices to limit increases of the hardwood component. Nomenclature: Marie-Victorin, 1995.

Quebec's ecological framework for forest management: a case study in the boreal forest of Abitibi

Abstract The Quebec Ministry of Forests has developed an approach to ecological cartography designed to complement its traditional forest inventory and delimit homogeneous land units for forest management. The methodology consists of field work, map analysis and photointerpretation. Within the hierarchical classification, ecological regions reflecting regional climate are mapped at the 1:1 250 000 scale. Major physiographic ensembles and ecological districts, mapped at 1:250 000, express patterns of physiography, geology and geomorphology and ecological types (1:20 000) characterize surface deposits, drainage class, slope and potential climax forest. Using information drawn from ecological classification work in northwestern Quebec and applying the Ministrys standards, an ecological framework for two townships was developed. In addition to maps of each classification level, the framework includes interpretative documents such as schematic cross-sections of ecosystems and descriptive texts. Examples of management interpretations (natural regeneration potential and site preparation effect on competition) are presented. The classification approach and its future are evaluated.

An alternative management regime of selection cutting for sustaining stand structure of mixed forests of northern Japan: a simulation study

In uneven-aged conifer–broadleaved mixed forests in Hokkaido, northern Japan, single-tree selection cutting has been a common management practice since the early twentieth century. This practice is expected to produce timber without major changes in stand structure or tree species composition. The demographic response of forests to this practice has often been unexpected, and degradation of stand properties has been widely observed. We propose here a sustainable management regime of selection cutting, based on an individual-based forest dynamics simulation model, SORTIE-ND. Our simulations, based on demographic data from 15 long-term monitoring stands, suggest that selection cutting using a lower cutting intensity together with a longer rotation period and reduced removal of small trees and conifer species is more appropriate than traditional systems in terms of maintaining stand structure and tree species composition, as well as being profitable financially. Supplemental regeneration practices, which can counter accidental mortality incurred during harvesting operations, would also be necessary to ensure tree recruitment.

A forest ecosystem guide for the Amos Lowlands Ecological Region, northwestern Quebec: A forest management approach

In Quebec, forest stations are defined as forest units that are reasonably homogeneous in terms of forest composition and site characteristics - as expressed by surficial deposit and moisture regime - and within which similar operational constraints for silvicultural potential and productivity levels may be expected. In the course of developing a field guide to the forest stations of the Amos Lowlands Ecological Region in northwestern Quebec, classifications of 12 site types and 72 forest stations (38 forest cover types or 16 general cover types) were developed. The classifications were based on a hybrid approach involving cluster analysis of forest ecological units inventoried in subregional studies, classical classification and ordination analyses performed on a regional biophysical inventory database, and empirically associating forest cover types to site types. The guide, while similar to other published forest ecosystem classification guides, emphasizes forest dynamics by presenting forest stations common to a given site type according to their successional stage. Field keys and general interpretations of forest potential and operational constraints are included in the guide. A summary description of the guide and accompanying documents is provided. A first draft has been distributed recently for feedback from industrial and government foresters and researchers in the region. Analyses of inventory data is continuing and modifications will be incorporated into a second draft before publication in 1995.

Development of a practical forest ecosystem classification from existing biophysical studies: An approach used in northwestern Quebec.

While forest ecosystem classification work in Quebec has traditionally concentrated on inventory and mapping, more effort is now being placed on developing field guides similar to those produced in other Canadian provinces. As part of a project to produce a practical forest ecosystem field guide for the Amos Lowlands Ecological Region in northwestern Quebec, existing sub-regional ecological studies were exploited in order to develop a regional classification of forest ecosystems, or forest stations. Review of four fundamental studies provided a list of 107 ecological phases, each representing a particular combination of forest composition, surface deposit type and moisture regime. A series of silvicultural and environmental interpretations were developed and values for each were attributed to the ecological phases. Cluster analysis was then performed to classify phases into 29 broader units. A large, regional biophysical database which became available later in the project provided a means of validating and effectively modifying the classification. The justifications for using the original approach are discussed.

Key factors in the maintenance of biodiversity in the boreal forest

In boreal forests, several bird species use snags for feeding or nesting and depend on them for their survival. Some studies have shown that the availability of snags is greatly influenced by the age of the forest and the type of perturbations (natural vs anthropogenic). Accordingly, cavity nesting birds seem largely affected by these changes in availability of snags. Nevertheless, the dynamics of dead wood and the distribution patterns of birds associated with this habitat feature has never been documented for black spruce forests. The first objective of this study was to document and explain the distribution patterns of birds associated with dead wood in natural forest landscapes that were disturbed by different fire events (< 2 years, 20 years, 95 years and > 200 years). The second objective was to evaluate the impact of forest management on this avian guild by comparing bird patterns and dead wood availability between natural and managed forests landscapes of equivalent ages (20 years, 80-95 years). Point count method was use for bird survey and 348 point counts were distributed in the 6 different forest landscapes. Vegetation plots centered on each point count were used to sample standing dead trees and coarse woody debris. Mature forest mosaic showed a greater species richness and abundance of cavity nesting birds than the other forest mosaics. Results also showed that recently burned forests are especially important for woodpeckers given the greater availability of dead trees in that forest stage compared to other forest stages. Single species models showed species-specific responses to abundance and quality of snags. Black-backed woodpecker was the species that responded the most to the availability of dead wood ; it was mainly restricted to the recently burned forest mosaic. Management implications of these findings for this avian guild are also discussed.