Intensive biomass removals and site productivity in Canada: A review of relevant issues

Abstract

A renewed interest in the intensive harvesting of forest biomass as a source of bioenergy in North America raises concerns about the impacts that this practice may have on the maintenance of forest soil productivity. In Canada, such concerns were first voiced in the 1970s, and studies were launched to investigate and predict the impact of intensive forest biomass removal on site productivity. Most of these studies focused on static nutrient budgets. In Canada and around the world, more detailed process models were also developed to study carbon, nitrogen and base cation cycles under different forest harvesting intensities. However, the validity of modelling results is still constrained by our lack of knowledge on the capacity of ecosystems to supply nutrients. A few sets of field trials have been established in Canada to gather empirical data on the impact of biomass removal on soil nutrient reserves as well as on tree nutrition and growth. Although still fairly recent, these field trials, along with the older ones established in other countries with similar site conditions and climates, provide opportunities to refine our understanding of the resilience of ecosystem processes and of the impacts of intensive biomass removal on ecosystem functions. Although numerous knowledge gaps and questions remain, some jurisdictions around the world have nevertheless issued policy directives and developed guidelines for biomass harvesting. As described by the concept of adaptive forest management, ecological monitoring of harvesting operations, scientific field testing and modelling can all interact to produce better knowledge that could then help improve policy directives. Key words: bioenergy, biomass, intensive harvesting, environmental sustainability

The potential of forest biomass as an energy supply for Canada

“…87, n o 1 -Th e f or esTr y Ch r on iCl e Forest harvesting residue inventories must therefore take ecological factors into consideration. Sites can be excluded from tree or residue harvesting because of environmental concerns such as soils with excessive drainage, low organic matter content or low nutrient supply, or where there are biodiversity or conservation issues (Hesselink 2010, Thiffault et al 2010. These factors can be incorporated into guidelines and regulations governing harvesting residues recovery and hence some jurisdictions define a proportion of harvesting residue that should be retained (e.g., 20% in Sweden [Skogsstyrelsen 2008] and 30% in Finland [Koistinen and Äijälä 2005]) and also sensitive sites where residues should not be removed (e.g., New Brunswick; Government of New Brunswick 2008).…”

Opportunities and challenges for Ontario's forest bioeconomy

“…Thiffault et al (2010) ask: "When do we know that the observed results of intensive biomass removal reflect 'complete' impact and that no further impacts will be observed in the future?" The rhetorical answer they provided was that despite numerous studies addressing this question, "we can never know until a full rotation is complete. "…”

“…Adaptive management (AM) is a commonly advocated approach for both engaging stakeholders and dealing with uncertainties related to forest management (Baker 2000, Duinker andTrevisan 2003) and has now been adopted by MNR as a method to address uncertainties related to biomass harvesting (Hesselink 2010, Lattimore et al 2010, Thiffault et al 2010. A cyclical approach to learning is the core of AM whereby uncertainties in institutional policies and management direction are recognized and changed in light of new knowledge gained from assessment of the effectiveness of current policy and management directions in a continuous process of learning and adapting (Lee 1993, Fig.…”

Legal Harvesting, Sustainable Sourcing and Cascaded Use of Wood for Bioenergy: Their Coverage through Existing Certification Frameworks for Sustainable Forest Management

“…Slash (branches and tops), small trees, and roots are commonly left in the forest as they are unsuitable for industrial processing [8]. On the one hand, with intensive biomass harvesting, sensitive forest soils can suffer from nutrient loss, which may result in lower forest re-growth than with conventional harvesting [11,[15][16][17][18][19]. On the other hand, more intensive harvesting may be beneficial for natural regeneration under certain circumstances.…”

“…With rising demands for bioenergy from woody biomass, more intensive harvesting is practiced or under research in some areas, for example in Scandinavia, the United Kingdom, Canada and the United States [8,[11][12][13][14][15][16][17][18]. Removal of additional forest biomass is expected to have greater impact on soil, water, and habitats than conventional forest practices in general.…”