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A review of natural disturbances to inform implementation of ecological forestry in Nova Scotia, Canada
AR Taylor et al., 2020. In Environmental Reviews “…To date, no comprehensive synthesis of existing data has been undertaken to document the natural disturbance regime of NS forests, limiting the application of natural disturbance emulation. Using over 300 years of documents and available data, we identified the main natural disturbance agents that affect NS forests and characterized their regimes. Overall, fire, wind (predominantly hurricanes), and outbreaks of spruce budworm (Choristoneura fumiferana (Clemens)) are the most important disturbance agents, causing substantial areas of low- (<30% mortality), moderate- (30%–60%), and high- (>60%) severity disturbance. While characterization of natural historic fire is challenging, due to past human ignitions and suppression, we estimated that the mean annual disturbance rate of moderate- to high-severity fire ranged between 0.17% and 0.4%·year−1 (return interval of 250–600 years), depending on ecosystem type. Hurricanes make landfall in NS, on average, every 7 years, resulting in wide-scale (>500 ha) forest damage. While hurricane track and damage severity vary widely among storms, the return interval of low- to high-severity damage is 700–1250 years (0.14%–0.08%·year−1). Conversely, the return interval of host-specific spruce budworm outbreaks is much shorter (<50 years) but more periodic, causing wide-scale, low- to high-severity damage to spruce–fir forests every 30–40 years. Further disturbance agents such as other insects (e.g., spruce beetle), diseases, ice storms, drought, and mammals can be locally important and (or) detrimental to individual tree species but contribute little to overall disturbance in NS. Climate change is expected to significantly alter the disturbance regime of NS, affecting current disturbances (e.g., increased fire) and driving the introduction of novel agents (e.g., hemlock wooly adelgid), and continued monitoring is needed to understand these changes.”
Natural disturbance regimes for implementation of ecological forestry: a review and case study from Nova Scotia, Canada
David A. MacLean et al., 2021 in Environmental Reviews “Ecological forestry is based on the idea that forest patterns and processes are more likely to persist if harvest strategies produce stand structures, return intervals, and severities similar to those from natural disturbances. Taylor et al. (2020) reviewed forest natural disturbance regimes in Nova Scotia, Canada, to support implementation of ecological forestry. In this follow-up paper, we (i) review the use of natural disturbance regimes to determine target harvest rotations, age structures, and residual stand structures; and (ii) describe a novel approach for use of natural disturbance regimes in ecological forestry developed for Nova Scotia. Most examples of ecological forestry consider only the local, dominant disturbance agent, such as fire in boreal regions. Our approach included: (i) using current ecological land classification to map potential natural vegetation (PNV) community types; (ii) determining cumulative natural disturbance effects of all major disturbances, in our case fire, hurricanes, windstorm, and insect outbreaks for each PNV; and (iii) using natural disturbance regime parameters to derive guidelines for ecological forestry for each PNV. We analyzed disturbance occurrence and return intervals based on low, moderate, and high severity classes (<30, 30–60, and >60% of biomass of living trees killed, respectively), which were used to determine mean annual disturbance rates by severity class. Return intervals were used to infer target stand age-class distributions for high, moderate, and low severity disturbances for each PNV. The range of variation in rates of high severity disturbances among PNVs was from 0.28%·year–1 in Tolerant Hardwood to 2.1%·year–1 in the Highland Fir PNV, equating to return intervals of 357 years in Tolerant Hardwood to 48 years in Highland Fir PNVs. As an example, this return interval for the Tolerant Hardwood PNV resulted in target rotation lengths of 200 years for 35% of the PNV area, 500 years for 40%, and 1000 years for 25%. The proposed approach of determining natural disturbance regimes for PNV communities and calculating target disturbance rates and corresponding harvest rotation lengths or entry times appears to be a feasible method to guide ecological forestry in any region with a strong ecological land classification system and multiple disturbance agents.”
Natural disturbance regimes in northeastern North America—evaluating silvicultural systems using natural scales and frequencies
Robert S. Seymour et al., 2002.Forest Ecology and Management 155 (2002) 357–367 “Many scientists and foresters have begun to embrace an ecological, natural disturbance paradigm for management, but lack specific guidance on how to design systems in ways that are in harmony with natural patterns. To provide such guidance, we conducted a comprehensive literature survey of northeastern disturbances, emphasizing papers that studied late-successional, undisturbed, or presettlement forests. Evidence demonstrates convincingly that such forests were dominated by relatively frequent, partial disturbances that produced a finely patterned, diverse mosaic dominated by late-successional species and structures. In contrast, large-scale, catastrophic stand-replacing disturbances were rare, returning at intervals of at least one order of magnitude longer than gap-producing events. Graphing the contiguous areas disturbed against their corresponding return intervals shows that these important disturbance parameters are positively related; area disturbed increases exponentially as the return interval lengthens. This graph provides a convenient metric, termed the natural disturbance comparability index, against which to evaluate both single and multi-cohort silvicultural systems based on their rotations or cutting-cycles and stand or gap sizes. We review implications of these findings for silvicultural practice in the region, and offer recommendations for emulating natural disturbance regimes.
Natural disturbance in an old-growth landscape of northern Maine, USA
Shawn Fraver*†, Alan S. White and Robert S. Seymour Journal of Ecology 2009, 97, 289–298 From the abstract: ….2. We investigated the frequency and severity of natural disturbance in a 2000-ha old-growth landscape (Big Reed Forest Reserve) in northern Maine, USA. Given its size, the Reserve provides an ideal opportunity to study, at multiple scales, natural forest processes in a region that has otherwise been dramatically altered by human activities. Using dendrochronological methods, we reconstructed disturbance histories for 37 randomly located plots stratified by five forest types (hardwood forests, mixed woods forests, red spruce forests, northern white-cedar seepage forests and northern white-cedar swamps). 3. We found no evidence of stand replacing disturbance on any plot during the last 120280 years (depending on plot). The overall mean disturbance rate was 9.6% canopy loss per decade (median 6.5%, maximum 55%, plots pooled), yet the distribution was strongly skewed toward the lower rates. 4. We found little differences in disturbance rates between forest types, save a slightly lower rate in the northern white-cedar swamps. However, if we ignore forest-type classifications, we see that disturbance rates are clearly influenced by gradients in the relative abundance of component tree species, owing to species’ relative susceptibilities to particular disturbance agents. 5. Synthesis. Relatively low rates of canopy disturbance allow the accrual of shade-tolerant saplings. The abundance of this advance regeneration…
The Presettlement Forest and Natural Disturbance Cycle of Northeastern Maine
Craig G. Lorimer Ecology Volume58, Issue1 January 1977 Pages 139-148 “Land survey records of 1793—1827 containing forest data for 1.65 x 106 ha of northern Maine were analyzed for species composition, successional status, and frequency of large—scale disturbance…If the amount of disturbed forest at this time was typical of the natural disturbance regime, then the average recurrence interval of fire and large—scale windthrow for a given site would be 800 and 1,150 years, respectively. Data on the structure of remnant virgin stands in the region likewise suggest that the time interval between severe disturbances was much longer than that needed to attain a climax, all—aged structure.
The Changing Disturbance Regime in Eastern Canadian Mixed Forests During the 20th Century
Tasneem Elzein1*, Dominique Arseneault1, Luc Sirois1 and Yan Boucher Front. Ecol. Evol., 09 June 2020
Stand-landscape integration in natural disturbance-based management of the southern boreal forest
Brian D.Harvey et al. 2002 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.
Disturbance effects on timberland returns
Kärenlampi, P.R. 2024 In PLOS Sustain Transform “Probability theory is applied to the effect of severe disturbances on the return rate on capital within multiannual stands growing crops. Two management regimes are discussed, rotations of even-aged plants on the one hand, and uneven-aged semi-stationary state on the other. The effect of any disturbance appears two-fold, contributing to both earnings and capitalization. Results are illustrated using data from a recently published study, regarding spruce (Picea abies) forests in Austria. The economic results differ from those of the paper where the data is presented, here indicating continuous-cover forestry is financially inferior to rotation forestry.
Comment:A difficult paper to understand paper, but some interesting lit, topics reviewed. The paper referenced for data: Thomas Knoke et al.,2022. Assessing the Economic Resilience of Different Management Systems to Severe Forest Disturbance in Environmental and Resource Economics. “Given the drastic changes in the environment, resilience is a key focus of ecosystem management. Yet, the quantification of the different dimensions of resilience remains challenging, particularly for long-lived systems such as forests. Here we present an analytical framework to study the economic resilience of different forest management systems, focusing on the rate of economic recovery after severe disturbance… We conclude that continuous cover systems can help to address the economic impacts of increasing disturbances in forest management.”