Driving factors of conifer regeneration dynamics in eastern Canadian boreal old-growth forests

AbstractOld-growth forests play a major role in conserving biodiversity, protecting water resources, sequestrating carbon, and these forests are indispensable resources for indigenous societies. To preserve the ecosystem services provided by these boreal ecosystems, it becomes necessary to develop novel silvicultural practices capable of emulating the natural dynamics and structural attributes of old-growth forests. The success of these forest management strategies depends on developing an accurate understanding of natural regeneration dynamics. Our goal was therefore to identify the main patterns and the drivers involved in the regeneration dynamics of old-growth forests, placing our focus on boreal stands dominated by black spruce (Picea mariana (L.) Mill.) and balsam fir (Balsam fir (L.) Mill.) in eastern Canada. We sampled 71 stands in a 2200 km2 study area located within Quebec’s boreal region. For each stand, we noted tree regeneration (seedlings and saplings), structural attributes (diameter distribution, deadwood volume, etc.), and abiotic (topography and soil) factors. We observed that secondary disturbance regimes and topographic constraints were the main drivers of balsam fir and black spruce regeneration. Furthermore, the regeneration dynamics of black spruce appeared more complex than those of balsam fir. We observed distinct phases of seedling production first developing within the understory, then seedling growth when gaps opened in the canopy, followed by progressive canopy closure. Seedling density, rather than the sapling density, had a major role in explaining the ability of black spruce to fill the canopy following a secondary disturbance. The density of balsam fir seedlings and saplings was also linked to the abundance of balsam fir trees at the stand level. This research helps explain the complexity of old-growth forest dynamics where many ecological factors interact at multiple temporal and spatial scales. This study also improves our understanding of ecological processes within native old-growth forests and identifies the key factors to consider when ensuring the sustainable management of old-growth boreal stands.

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Bryophyte Conservation in Managed Boreal Landscapes: Fourteen-Year Impacts of Partial Cuts on Epixylic Bryophytes

Frontiers in Forests and Global Change ◽

10.3389/ffgc.2021.674887 ◽

2021 ◽

Vol 4 ◽

Author(s):

Jeffrey Opoku-Nyame ◽

Alain Leduc ◽

Nicole J. Fenton

Keyword(s):

Species Composition ◽

Coarse Woody Debris ◽

Black Spruce ◽

Woody Debris ◽

Permanent Plots ◽

Old Growth ◽

Clear Cut ◽

Old Growth Forest ◽

Old Growth Forests ◽

Over Time

Clear cut harvest simplifies and eliminates old growth forest structure, negatively impacting biodiversity. Partial cut harvest has been hypothesized (1) to have less impact on biodiversity than clear cut harvest, and (2) to encourage old growth forest structures. Long-term studies are required to test this hypothesis as most studies are conducted soon after harvest. Using epixylic bryophytes as indicators, this study addresses this knowledge gap. Fourteen years after harvest, we examined changes in epixylic bryophyte community composition richness and traits, and their microhabitats (coarse woody debris characteristics and microclimate) along an unharvested, partial cuts and clear cuts harvest treatment in 30 permanent plots established in the boreal black spruce (Picea mariana) forests of northwestern Quebec, Canada. Our results were compared to those of an initial post-harvest study (year 5) and to a chronosequence of old growth forests to examine species changes over time and the similarity of bryophyte communities in partial cut and old growth forests. Coarse woody debris (CWD) volume by decay class varied among harvest treatments with partial cuts and clear cuts recording lower volumes of early decay CWD. The epixylic community was richer in partial cuts than in mature unharvested forests and clear cuts. In addition, species richness and overall abundance doubled in partial and clear cuts between years 5 and 14. Species composition also differed among treatments between years 5 and 14. Furthermore, conditions in partial cut stands supported small, drought sensitive, and old growth confined species that are threatened by conditions in clear cut stands. Lastly, over time, species composition in partial cuts became more similar to old growth forests. Partial cuts reduced harvest impacts by continuing to provide favorable microhabitat conditions that support epixylic bryophytes. Also, partial cut harvest has the potential to encourage old growth species assemblages, which has been a major concern for biodiversity conservation in managed forest landscapes. Our findings support the promotion of partial cut harvest as an effective strategy to achieve species and habitat conservation goals.

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The eastern boreal old-growth balsam fir forest: a distinct ecosystem

Canadian Journal of Botany ◽

10.1139/b04-063 ◽

2004 ◽

Vol 82 (6) ◽

pp. 830-849 ◽

Cited By ~ 31

Author(s):

Mireille Desponts ◽

Geneviève Brunet ◽

Louis Bélanger ◽

Mathieu Bouchard

Keyword(s):

Plant Species ◽

Balsam Fir ◽

Old Growth ◽

Saprophytic Fungi ◽

Old Growth Forest ◽

Second Growth ◽

Old Growth Forests ◽

Gaspe Peninsula ◽

Pristine Forest ◽

Gaspé Peninsula

The objective of this project was to assess the importance of pristine forests in maintaining the botanical biodiversity of the humid boreal balsam fir forest of eastern Canada. The study was based on a comparative analysis of silviculturally mature second-growth stands and pristine forest stands at two stages of development (senescent and old growth) in the Gaspé Peninsula. The structure and composition of the stands was described, and the abundance of structural attributes evaluated. The communities of nonvascular plant species (mosses, liverworts), lichens, and saprophytic fungi were compared. The study demonstrated that the pristine forest landscape studied was composed largely of old-growth and senescent stands. Old-growth forests are differentiated by their irregular structure. The results regarding nonvascular plant species, lichens, and saprophytic fungi show higher species diversity in old-growth forests, corresponding to higher habitat diversity. Species assemblages were comparable between the pristine forests, but different from those of second-growth stands. Rare species are found more frequently in the old-growth forests. The results indicate that the old-growth balsam fir stands of the Gaspé Peninsula constitute critical habitats for maintaining a large number of species threatened by the gradual disappearance of primeval stands.Key words: forest management, biodiversity, old-growth forest, humid boreal fir forest, nonvascular plants.

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Structure, composition, and diversity of old-growth black spruce boreal forest of the Clay Belt region in Quebec and Ontario

Environmental Reviews ◽

10.1139/a03-013 ◽

2003 ◽

Vol 11 (S1) ◽

pp. S79-S98 ◽

Cited By ~ 77

Author(s):

Karen Harper ◽

Catherine Boudreault ◽

Louis DeGrandpré ◽

Pierre Drapeau ◽

Sylvie Gauthier ◽

...

Keyword(s):

Boreal Forest ◽

Picea Mariana ◽

Black Spruce ◽

Small Scale ◽

Structural Development ◽

Spruce Forest ◽

Forest Stands ◽

Old Growth ◽

Old Growth Forest ◽

Old Growth Forests

Old-growth black spruce (Picea mariana) boreal forest in the Clay Belt region of Ontario and Quebec is an open forest with a low canopy, quite different from what many consider to be "old growth". Here, we provide an overview of the characteristics of old-growth black spruce forest for three different site types on organic, clay, and coarse deposits. Our objectives were (1) to identify the extent of older forests; (2) to describe the structure, composition, and diversity in different age classes; and (3) to identify key processes in old-growth black spruce forest. We sampled canopy composition, deadwood abundance, understorey composition, and nonvascular plant species in 91 forest stands along a chronosequence that extended from 20 to more than 250 years after fire. We used a peak in tree basal area, which occurred at 100 years on clay and coarse sites and at 200 years on organic sites, as a process-based means of defining the start of old-growth forest. Old-growth forests are extensive in the Clay Belt, covering 3050% of the forested landscape. Black spruce was dominant on all organic sites, and in all older stands. Although there were fewer understorey species and none exclusive to old-growth, these forests were structurally diverse and had greater abundance of Sphagnum, epiphytic lichens, and ericaceous species. Paludification, a process characteristic of old-growth forest stands on clay deposits in this region, causes decreases in tree and deadwood abundance. Old-growth black spruce forests, therefore, lack the large trees and snags that are characteristic of other old-growth forests. Small-scale disturbances such as spruce budworm and windthrow are common, creating numerous gaps. Landscape and stand level management strategies could minimize structural changes caused by harvesting, but unmanaged forest in all stages of development must be preserved in order to conserve all the attributes of old-growth black spruce forest. Key words: boreal forest, old growth, paludification, Picea mariana, structural development, succession.

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Unveiling the Diversity of Tree Growth Patterns in Boreal Old-Growth Forests Reveals the Richness of Their Dynamics

Forests ◽

10.3390/f11030252 ◽

2020 ◽

Vol 11 (3) ◽

pp. 252 ◽

Cited By ~ 4

Author(s):

Maxence Martin ◽

Cornélia Krause ◽

Nicole J. Fenton ◽

Hubert Morin

Keyword(s):

Radial Growth ◽

Growth Patterns ◽

Radial Increment ◽

Forest Types ◽

Eastern Canada ◽

Old Growth ◽

Growth Trends ◽

Silvicultural Treatments ◽

Old Growth Forest ◽

Old Growth Forests

Research Highlights: Radial growth patterns of trees growing in old-growth boreal forests in eastern Canada can be grouped into a small number of simple patterns that are specific to different old-growth forest types or successional stages. Background and Objectives: Identifying the main radial growth trends in old-growth forests could help to develop silvicultural treatments that mimic the complex dynamics of old-growth forests. Therefore, this study aimed to identify the main radial growth patterns and determine how their frequencies change during forest succession in old-growth forests, focusing on boreal landscapes in eastern Canada. Materials and Methods: We used dendrochronological data sampled from 21 old-growth stands in the province of Quebec, Canada. Tree-ring chronologies were simplified into chronologies of equal length to retain only primary growth trends. We used k-means clustering to identify individual growth patterns and the difference in growth-pattern frequency within the studied stands. We then used non-parametric analyses of variance to compare tree or stand characteristics among the clusters. Results: We identified six different growth patterns corresponding to four old-growth forest types, from stands at the canopy breakup stage to true old-growth stands (i.e., when all the pioneer cohort had disappeared). Secondary disturbances of low or moderate severity drove these growth patterns. Overall, the growth patterns were relatively simple and could be generally separated into two main phases (e.g., a phase of limited radial increment size due to juvenile suppression and a phase of increased radial increment size following a growth release). Conclusions: The complexity of old-growth forest dynamics was observed mainly at the stand level, not at the tree level. The growth patterns observed in true old-growth forests were similar to those observed following partial or stem-selection cuts in boreal stands; thus, these silvicultural treatments may be effective in mimicking old-growth dynamics.

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Epiphytic bryophytes on European aspen Populus tremula in old-growth forests in northeastern Finland and in adjacent sites in Russia

Canadian Journal of Botany ◽

10.1139/b00-023 ◽

2000 ◽

Vol 78 (4) ◽

pp. 529-536 ◽

Cited By ~ 10

Author(s):

E Ojala ◽

M Mönkkönen ◽

J Inkeröinen.

Keyword(s):

Landscape Structure ◽

Spatial Scales ◽

Regional Scale ◽

Tree Density ◽

Populus Tremula ◽

Old Growth ◽

Lobaria Pulmonaria ◽

Old Growth Forest ◽

European Aspen ◽

Old Growth Forests

We studied the occurrence and cover of epiphytic bryophytes and one lichen species (Lobaria pulmonaria (L.) Hoffm.) growing on Populus tremula L. trunks. Our aim was to explore the spatial scales where epiphyte species respond to their environment. At the landscape scale, fragmented Finnish old-growth forests close to the Russian border and farther west in a heavily fragmented landscape were compared with Russian sites with more continuous old-growth forest landscapes to assess the effect of landscape structure on epiphyte assemblages. We studied factors affecting populations at the level of individual sites and local habitat patches within the forests. Twelve sites were surveyed for epiphytes. We estimated epiphyte occurrence from 353 Populus tremula trunks. There seemed to be only minor differences in the structure of epiphyte assemblages between the three landscapes surveyed. Species richness varied also independently of the landscape structure but was positively related to regional Populus tremula abundance (alpha diversity) and the size of the substrate trunk (point diversity). At the regional scale, the most important factor affecting the occurrence of epiphytes was the abundance of Populus tremula. At the local scale, the size of the Populus tremula surveyed and tree density around the trunk surveyed correlated positively with the occurrence of some species. The size and abundance of Populus tremula as well as tree density are the most important factors for maintaining viable populations of the studied species.Key words: biodiversity, boreal forest, Bryophyte, forest management, landscape structure, Lobaria pulmonaria.

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Overview of old-growth forests in Canada from a science perspective

Environmental Reviews ◽

10.1139/a03-018 ◽

2003 ◽

Vol 11 (S1) ◽

pp. S1-S7 ◽

Cited By ~ 24

Author(s):

A Mosseler ◽

I Thompson ◽

B A Pendrel

Keyword(s):

Genetic Diversity ◽

Growth Index ◽

Reproductive Fitness ◽

General Interest ◽

Forest Types ◽

Eastern Canada ◽

Old Growth ◽

Old Growth Forest ◽

Old Growth Forests ◽

Forest Regions

In response to a broad public concern about the rapidly diminishing area of old-growth forests and their intrinsic biological value, the Canadian Forest Service organized a national symposium in 2001 to discuss the old-growth issue from a science perspective. The objectives were: (i) to bring together Canadian expertise on old-growth forests, (ii) to define old growth within the main forest regions of Canada, (iii) to understand its biological complexities and ecological roles, and (iv) to discuss management and restoration experiences and options. Some forest regions of Canada still contain significant old-growth forest (e.g., some boreal forest regions), although other regions contain very little primary, relatively undisturbed, older forest (e.g., eastern temperate-zone forest regions). One of the difficulties in managing and conserving old-growth forests is defining them in a scientifically meaningful, yet operational and policy-relevant manner. This difficulty may be overcome by developing an index of "old-growthness" (Spies and Franklin 1988) related to specific forest regions or forest types. Such an old-growth index would allow for the inclusion of specific attributes, composition, functions, and processes seen as relevant to different ecological regions or specific forest types and could serve as a basis for prioritizing local or regional conservation and management activities. Thus, such an index approach has worldwide applicability. Traditionally, old-growth forests have been valued primarily as habitat for forest-dependent, specifically old-growth-dependent, wildlife. Recent results from research on old-growth forests in eastern Canada suggest that as tree populations age they tend to increase in genetic diversity and reproductive fitness, suggesting that old-growth forests may serve as natural reservoirs of genetic diversity and reproductive fitness for the constituent tree species. This has important implications for the dispersal and adaptation of trees across increasingly fragmented forest landscapes subject to the anticipated rapid climatic changes and the introduction of new pest and disease problems. Old-growth conservation goes well beyond the more traditional areas of watershed (including water quality) and habitat protection and includes emerging issues such as the conservation of genetic resources and carbon sequestration. It is very much a cross-sectoral issue with many interdisciplinary linkages. Therefore, conservation and protection of old-growth forests should be of wide general interest to the forest sector. Key words: biodiversity conservation, Canada's forests, genetic diversity, late-successional temperate forests, old-growth index, reproductive fitness.

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Compared to Wildfire, Management Practices Reduced Old-Growth Forest Diversity and Functionality in Primary Boreal Landscapes of Eastern Canada

Frontiers in Forests and Global Change ◽

10.3389/ffgc.2021.639397 ◽

2021 ◽

Vol 4 ◽

Author(s):

Maxence Martin ◽

Pierre Grondin ◽

Marie-Claude Lambert ◽

Yves Bergeron ◽

Hubert Morin

Keyword(s):

Boreal Forests ◽

Economic Value ◽

Industrial Scale ◽

Old Growth ◽

Ecosystem Based Management ◽

Old Growth Forest ◽

Old Growth Forests ◽

Boreal Landscapes ◽

The Impact ◽

Primary Forests

Large primary forest residuals can still be found in boreal landscapes. Their areas are however shrinking rapidly due to anthropogenic activities, in particular industrial-scale forestry. The impacts of logging activities on primary boreal forests may also strongly differ from those of wildfires, the dominant stand-replacing natural disturbance in these forests. Since industrial-scale forestry is driven by economic motives, there is a risk that stands of higher economic value will be primarily harvested, thus threatening habitats, and functions related to these forests. Hence, the objective of this study was to identify the main attributes differentiating burned and logged stands prior to disturbance in boreal forests. The study territory lies in the coniferous and closed-canopy boreal forest in Québec, Canada, where industrial-scale logging and wildfire are the two main stand-replacing disturbances. Based on Québec government inventories of primary forests, we identified 427 transects containing about 5.5 circular field plots/transect that were burned or logged shortly after being surveyed, between 1985 and 2016. Comparative analysis of the main structural and environmental attributes of these transects highlighted the strong divergence in the impact of fire and harvesting on primary boreal forests. Overall, logging activities mainly harvested forests with the highest economic value, while most burned stands were low to moderately productive or recently disturbed. These results raise concerns about the resistance and resilience of remnant primary forests within managed areas, particularly in a context of disturbance amplification due to climate change. Moreover, the majority of the stands studied were old-growth forests, characterized by a high ecological value but also highly threatened by anthropogenic disturbances. A loss in the diversity and functionality of primary forests, and particularly the old-growth forests, therefore adds to the current issues related to these ecosystems. Since 2013, the study area is under ecosystem-based management, which implies that there have been marked changes in forestry practices. Complementary research will be necessary to assess the capacity of ecosystem-based management to address the challenges identified in our study.

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Boreal old-growth forest structural diversity challenges aerial photographic survey accuracy

Canadian Journal of Forest Research ◽

10.1139/cjfr-2019-0177 ◽

2020 ◽

Vol 50 (2) ◽

pp. 155-169 ◽

Cited By ~ 4

Author(s):

Maxence Martin ◽

Nicole J. Fenton ◽

Hubert Morin

Keyword(s):

Sustainable Forest Management ◽

Forest Succession ◽

Structural Diversity ◽

Aerial Survey ◽

Old Growth ◽

Tree Species Composition ◽

Forest Inventories ◽

Old Growth Forest ◽

Aerial Surveys ◽

Old Growth Forests

The erosion of old-growth forests in boreal managed landscapes is a major issue currently faced by forest managers; however, resolving this problem requires accurate surveys. The intention of our study was to determine if historic operational aerial forest surveys accurately identified boreal old-growth forests in Quebec, Canada. We first compared stand successional stages (even-aged vs. old-growth) in two aerial surveys performed in 1968 (preindustrial aerial survey) and 2007 (modern aerial survey) on the same 2200 km2 territory. Second, we evaluated the accuracy of the modern aerial survey by comparing its results with those of 74 field plots sampled in the study territory between 2014 and 2016. The two aerial surveys differed significantly; 80.8% of the undisturbed stands that were identified as “old-growth” in the preindustrial survey were classified as “even-aged” in the modern survey, and 60% of the stands identified as “old-growth” by field sampling were also erroneously identified as “even-aged” by the modern aerial survey. The scarcity of obvious old-growth attributes in boreal old-growth forests, as well as poorly adapted modern aerial survey criteria (i.e., criteria requiring high vertical stratification and significant changes in tree species composition along forest succession), were the main factors explaining these errors. It is therefore likely that most of Quebec’s boreal old-growth forests are currently not recognized as such in forest inventories, challenging the efficacy of sustainable forest management policies.

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Variability in Mixed Conifer Spatial Structure Changes Understory Light Environments

Forests ◽

10.3390/f10111015 ◽

2019 ◽

Vol 10 (11) ◽

pp. 1015 ◽

Cited By ~ 2

Author(s):

Jeffery B. Cannon ◽

Wade T. Tinkham ◽

Ryan K. DeAngelis ◽

Edward M. Hill ◽

Mike A. Battaglia

Keyword(s):

Spatial Patterns ◽

Ponderosa Pine ◽

Spatial Scales ◽

Light Availability ◽

Structural Complexity ◽

Tree Regeneration ◽

Conifer Forests ◽

Mixed Conifer ◽

Regeneration Dynamics ◽

Wide Range

In fire-adapted conifer forests of the Western U.S., changing land use has led to increased forest densities and fuel conditions partly responsible for increasing the extent of high-severity wildfires in the region. In response, land managers often use mechanical thinning treatments to reduce fuels and increase overstory structural complexity, which can help improve stand resilience and restore complex spatial patterns that once characterized these stands. The outcomes of these treatments can vary greatly, resulting in a large gradient in aggregation of residual overstory trees. However, there is limited information on how a range of spatial outcomes from restoration treatments can influence structural complexity and tree regeneration dynamics in mixed conifer stands. In this study, we model understory light levels across a range of forest density in a stem-mapped dry mixed conifer forest and apply this model to simulated stem maps that are similar in residual basal area yet vary in degree of spatial complexity. We found that light availability was best modeled by residual stand density index and that consideration of forest structure at multiple spatial scales is important for predicting light availability. Second, we found that restoration treatments differing in spatial pattern may differ markedly in their achievement of objectives such as density reduction, maintenance of horizontal and tree size complexity, and creation of microsite conditions favorable to shade-intolerant species, with several notable tradeoffs. These conditions in turn have cascading effects on regeneration dynamics, treatment longevity, fire behavior, and resilience to disturbances. In our study, treatments with high aggregation of residual trees best balanced multiple objectives typically used in ponderosa pine and dry mixed conifer forests. Simulation studies that consider a wide range of possible spatial patterns can complement field studies and provide predictions of the impacts of mechanical treatments on a large range of potential ecological effects.

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