Natural disturbance regimes for implementation of ecological forestry: a review and case study from Nova Scotia, Canada

Abstract

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 1) review use of natural disturbance regimes to determine target harvest rotations, age structures, and residual stand structures; and 2) 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: 1) using current ecological land classification to map potential natural vegetation (PNV) community types; 2) determining cumulative natural disturbance effects of all major disturbances, in our case fire, hurricanes, windstorm, and insect outbreaks for each PNV; and 3) 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), 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% yr-1 in Tolerant Hardwood to 2.1% yr-1 in the Highland Fir PNV, equating to return intervals of 357 years in Tolerant Hardwood to 48 yrs 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.

Leaf phenology as an indicator of ecological integrity

“…We also explored the timing of leaf phenology itself as an ecological integrity indicator, though found that variation due to other factors was of a similar magnitude or in some cases greater than variation due to disturbance or stress, and that this approach neglects the role of developed frost hardiness, which may not vary consistently with phenology between species (see Zohner et al, 2020). Extreme weather like Hurricane Dorian (>10,000 ha of forest damage), which led to widespread forest damage on the order of >500 ha, may affect Nova Scotia, the province in which 22 of the 33 Acadian Phenocam Network cameras are managed, as frequently as once every seven years (MacLean et al, 2022; Taylor et al, 2020). Insect outbreaks such as that of Choristoneura fumiferana , the spruce budworm, which lead to widespread damage of predominant native tree species, may also occur in Nova Scotia once every 30–40 years (Smith et al, 2010).…”

“…Understanding which species are robust, resilient, or susceptible to global change through the monitoring protocol we proposed here will provide insight for effective conservation and management activities (Chamberlain et al, 2019). This would allow for informed decisions regarding ecological forestry practices in the context of global change, which species to plant for remediation following disturbance events, and which species may require additional focus for protection from disturbance agents (MacLean et al, 2022; Price et al, 2013; Taylor et al, 2020).…”

A systematic map of knowledge exchange across the science‐policy interface for forest science: How can we improve consistency and effectiveness?

“…Scientific knowledge is used to guide tangible outcomes in forest management such as designing silvicultural prescriptions (which determine the approach to harvesting and regeneration of trees; e.g. Achim et al, 2022; MacLean et al, 2021) and conserving forest biodiversity (e.g. Scullion et al, 2019), among others.…”

Climate‐driven shifts in leaf senescence are greater for boreal species than temperate species in the Acadian Forest region in contrast to leaf emergence shifts

“…Understandings and predictions of future leaf phenology patterns in the eastern Acadian Forest Region are limited due to a lack of observational data, compounded by a highly variable climatic regime (Garbary & Hill, 2021 ; MacLean et al, 2022 ; Pearson & D'Orangeville, 2022 ; Steenberg et al, 2013 ; Taylor et al, 2020 ). A study comparing climate normals across Nova Scotia from 1961 to 1990 and 1991 to 2020 found that warming in the autumn has been more pronounced relative to spring, with a larger relative increase in the number of frost‐free days in autumn (Garbary & Hill, 2021 ).…”