R.A. Fleming. (1996). A mechanistic perspective of possible influences of climate change on defoliating insects in North America's boreal forests. Silva Fennica vol. 30 no. 2–3 article id 5595. https://doi.org/10.14214/sf.a9240

Keywords: climate change; disturbance regimes; boreal forest dynamics; Abies balsamea; natural selection; North America; Choristoneura fumiferana; insect outbreaks; phenological relationships; plant quality; extreme weather; thresholds

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There is no doubt that tree survival, growth, and reproduction in North America's boreal forests would be directly influenced by the projected changes in climate if they occur. The indirect effects of climate change may be of even greater importance, however, because of their potential for altering the intensity, frequency, and perhaps even the very nature of the disturbance regimes which drive boreal forest dynamics. Insect defoliator populations are one of the dominating disturbance factors in North America's boreal forests and during outbreaks trees are often killed over vast forest areas. If the predicted shifts in climate occur, the damage patterns caused by insects may be considerably changed, particularly those of insects whose temporal and spatial distributions are singularly dependent on climatic factors. The ensuing uncertainties directly affect depletion forecasts, pest hazard rating procedures, and long-term planning for pest control requirements. Because the potential for wildfire often increases in stands after insect attack, uncertainties in future insect damage patterns also lead to uncertainties in fire regimes. In addition, because the rates of processes key to biogeochemical and nutrient recycling are influenced by insect damage, potential changes in damage patterns can indirectly affect ecosystem resilience and the sustainability of the multiple uses of the forest resource.

In this paper, a mechanistic perspective is developed based on available information describing how defoliating forest insects might respond to climate warming. Because of its prevalence and long history of study, the spruce budworm, Choristoneura fumiferana Clem. (Lepidoptera: Tortricidae), is used for illustrative purposes in developing this perspective. The scenarios that follow outline the potential importance of threshold behaviour, historical conditions, phenological relationships, infrequent but extreme weather, complex feedbacks, and natural selection. The urgency of such considerations is emphasized by reference to research suggesting that climate warming may already be influencing some insect lifecycles.

Fleming, E-mail: rf@mm.unknown

Category : Research article

article id 90, category Research article

Per Angelstam, Kjell Andersson, Robert Axelsson, Marine Elbakidze, Bengt Gunnar Jonsson, Jean-Michel Roberge. (2011). Protecting forest areas for biodiversity in Sweden 1991–2010: the policy implementation process and outcomes on the ground. Silva Fennica vol. 45 no. 5 article id 90. https://doi.org/10.14214/sf.90

Keywords: forest policy; forest protection; restoration ecology; connectivity; green infrastructure; umbrella species; forest disturbance regimes; participation and collaboration

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Swedish forest and environmental policies imply that forests should be managed so that all naturally occurring species are maintained in viable populations. This requires maintenance of functional networks of representative natural forest and cultural woodland habitats. We first review the policy implementation process regarding protected areas in Sweden 1991–2010, how ecological knowledge was used to formulate interim short-term and strategic long-term biodiversity conservation goals, and the development of a hierarchical spatial planning approach. Second, we present data about the amount of formally protected and voluntarily set aside forest stands, and evaluate how much remains in terms of additional forest protection, conservation management and habitat restoration to achieve forest and environmental policy objectives in the long-term. Third, a case study in central Sweden was made to estimate the functionality of old Scots pine, Norway spruce and deciduous forest habitats, as well as cultural woodland, in different forest regions. Finally, we assess operational biodiversity conservation planning processes. We conclude that Swedish policy pronouncements capture the contemporary knowledge about biodiversity and conservation planning well. However, the existing area of protected and set-aside forests is presently too small and with too poor connectivity. To bridge this gap, spatial planning, management and restoration of habitat, as well as collaboration among forest and conservation planners need to be improved.

Angelstam, School for Forest Management, Faculty of Forest Sciences, Swedish University of Agricultural Sciences, Skinnskatteberg, Sweden E-mail: per.angelstam@slu.se
Andersson, School for Forest Management, Faculty of Forest Sciences, Swedish University of Agricultural Sciences, Skinnskatteberg, Sweden E-mail: ka@nn.se
Axelsson, School for Forest Management, Faculty of Forest Sciences, Swedish University of Agricultural Sciences, Skinnskatteberg, Sweden E-mail: ra@nn.se
Elbakidze, School for Forest Management, Faculty of Forest Sciences, Swedish University of Agricultural Sciences, Skinnskatteberg, Sweden E-mail: me@nn.se
Jonsson, Dept of Natural Science, Engineering and Mathematics, Mid Sweden University, Sundsvall, Sweden E-mail: bgj@nn.se
Roberge, Dept of Wildlife, Fish and Environmental Studies, Faculty of Forest Sciences, Swedish University of Agricultural Sciences, Umeå, Sweden E-mail: jmr@nn.se

Category : Review article

article id 72, category Review article

Ekaterina Shorohova, Daniel Kneeshaw, Timo Kuuluvainen, Sylvie Gauthier. (2011). Variability and dynamics of old-growth forests in the circumboreal zone: implications for conservation, restoration and management. Silva Fennica vol. 45 no. 5 article id 72. https://doi.org/10.14214/sf.72

Keywords: late-successional forest; disturbance regimes; stand dynamic types; cohort dynamics

Abstract | View details | Full text in PDF | Author Info

Due to the unprecedented loss of old-growth forests to harvesting throughout circumboreal regions an understanding of similarities and differences in old-growth dynamics is needed to design effective restoration, management and conservation efforts. This paper reviews concepts, prevalence and variability of old-growth forests across landscapes, and evaluates different stand scale dynamics at the old-growth stage across the circumboreal zone. Old-growth historically dominated many boreal forest landscapes in both Eurasia and North America. Throughout much of North America, and to some extent in western Siberia, the natural prevalence and development of old-growth forests are regulated by the occurrence of stand-replacing fires. In eastern North America and Siberia, insect outbreaks may, however, be more important. Insect outbreaks as well as recurrent non-stand replacing surface fires and windthrows, when occurring at the old-growth stage, often form stands characterized by several tree age-class cohorts. This multi age-class forest development type is common in Europe and eastern Siberia but its prevalence and importance in boreal North-America is not well documented. Similarities in successional dynamics across the circumboreal region are found in the development of mono-dominant even-aged stands, the replacement of shade intolerant tree species by shade tolerant species, as well as in all-aged stands driven by small-scale gap dynamics. The message to land managers is that the focus should not only be on setting aside remaining old-growth forests or in restoring static old-growth attributes, but also in emulating natural disturbances and successional dynamics at landscape and regional scales to maintain natural variability in old-growth attributes through time.

Shorohova, Saint-Petersburg State Forest University, Saint-Petersburg, Russia & Finnish Forest Research Institute, Vantaa Research Unit, Vantaa, Finland (ekaterina.shorohova@metla.fi) E-mail: shorohova@ES13334.spb.edu
Kneeshaw, Université du Québec à Montréal, Centre d’étude de la forêt, Montreal, Canada E-mail: dk@nn.ca
Kuuluvainen, University of Helsinki, Department of Forest Sciences, Helsinki, Finland E-mail: tk@nn.fi
Gauthier, Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, Québec, Canada E-mail: sg@nn.fi

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