Oil Sands Terrestrial Habitat and Risk Modelling for Disturbance and Reclamation – Phase II Report

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  • The overall objective of this project is to develop a framework that integrates risk management and strategic decision-making to evaluate the impact of disturbance (natural and industrial) on ecosystem products and services, and on habitat availability for terrestrial species in Alberta’s Lower Athabasca planning region. This includes an evaluation of the impact of disturbance, conservation, and reclamation activities associated with oil sands development both at the lease and regional levels. The principal objective in Phase II is an evaluation of the impact of climate and climate change on reclamation success, as compared to the basecase analysis (no climate-related impacts) conducted in Phase I. Chapter 2, describes the calibration and testing of a tree ring model for the three major tree species represented in the Alberta Oil Sands region, white spruce (Picea glauca), trembling aspen (Populus tremuloides) and jack pine (Pinus banksiana). The model simulates the relationship between annual sapwood production (expressed as a ring width index), mean daily temperature and available soil moisture. Simulated ring width increments were regressed against the measured annual ring width index to evaluate the performance of the model. The tree ring model was able to successfully predict patterns in ring chronologies for white spruce and jack pine. Indeed, the explanatory capability of the model exceeded that which is typical from studies linking ring width to simple climate variables. In the case of aspen, results were less definitive. This study thus provides evidence for the applicability of this approach and it also highlights the utility of incorporating a few basic ecophysiological principles into models of tree growth. Chapter 3 describes the characteristics of five Global Circulation Models and the Alberta Climate Model that are used to simulate climate change in the rest of the report. In Chapter 4, the Tree and Climate Assessment (TACA) model is used to assess the regeneration potential of three boreal tree species (white spruce Picea glauca, trembling aspen Populus tremuloides and jack pine Pinus banksiana) on different soil types in northern Alberta. Model results indicate that under most scenarios, regeneration by all species is generally favoured by the warmer temperatures and higher annual precipitation predicted under climate change. One striking exception is the most severe emission scenario, where very warm conditions are a significant driver of moisture limitations and a low to non-existent regeneration potential. In the case of aspen, its ability to reproduce vegetatively improves the adaptive capacity of this species; clones can regenerate and persist by re-sprouting while maintaining their colonizing ability and potentially enhancing their distribution through seed-based regeneration. As a model that incorporates many of the biophysical variables important to tree regeneration, TACA is a suitable tool for making realistic projections of the impact of climate and climate change on the regeneration potential of the boreal tree species in northern Alberta. Chapter 5 evaluates future ecosystem development in jack pine, aspen and white spruce with the FORECAST Climate model after incorporating the five climate change scenarios developed in Chapter 3. Stands initiated under current climatic conditions (in year 2011) are predicted to experience enhanced long-term productivity (to year 2111) under a changing climate regime, as compared with the growth that would have occurred if historical climatic conditions been maintained over the next 100 years. Although there was a substantial range among GCM scenarios in their projections of stemwood growth, the minimum projection was always greater than that derived from the historical climate data. In general, forest productivity in northern latitudes is temperature-limited. Model output suggests that tree productivity in the region may be enhanced through much of the 21st century as a result of improvement in the thermal regime (longer growing seasons, warmer soil, increased decomposition) and potentially an overall increase in available moisture, that more than compensates for any negative impact associated with growing season moisture limitations. In general, understory plant communities were negatively affected by the projected increase in overstory productivity under climate change. Model projections indicated that habitat suitability under climate change would be improved overall, relative to values derived using the historical climate regime. The greatest improvement was for the d1 (aspen) ecosite and the least in the d3 (white spruce) ecosite. Taken together, the model results suggest a number of management responses within the context of oil sands reclamation that can reduce risk, and help mitigate carbon emissions and retain habitat features, at least for some species. These are: 1. Minimize the forest cover removed as part of mine operations. Retention of forest cover improves the carbon balance and, depending on its areal extent and spatial configuration, can also serve as refugia for wildlife on the mine footprint. 2. Return forest cover as soon as is practicable. Forest productivity under climate change is enhanced, which will translate into higher carbon sequestration and improved habitat suitability as compared to the reference case (the historical climate regime). Returning forest cover quickly thus serves to leverage the benefits from improved productivity. 3. Expand forest carbon sinks to promote carbon storage and development of habitat attributes. Adding fertilizer annually for 5 to 10 years after planting, particularly on poor sites, will promote both tree and understory productivity, and thus carbon storage and development of habitat attributes. Retaining and adding slash and other dead organic matter after land clearing will also increase carbon stores (at least temporarily) but more importantly create valuable habitat. 4. Encourage species mixtures over monoculture plantations. Conifer monocultures and extensive tracts of aspen-dominated forests are vulnerable to outbreaks of insect defoliation and bark beetles. Planting tree species in mixtures or at the very least, reducing the areal extent of monocultures may help mitigate risk, enhance forest resilience, and/or prevent large-scale pathogen outbreaks. 5. Increase protection measures. Mine operators should develop and implement regular monitoring programs on their reclaimed areas to identify potential threats to stand health before they become unmanageable. 6. Enhance fire suppression capability. An increased risk of forest fires (both in frequency and severity) is predicted to occur with climate change. This could result in significantly greater releases of carbon as material is consumed, but can also generate rapid and pronounced shifts in community composition.

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    Attribution 3.0 International