Moving beyond bioclimatic envelope models: integrating upland forest and peatland processes to predict ecosystem transitions under climate change in the western Canadian boreal plain

Abstract

By the end of this century, much of the climate space of western Canada's boreal forest is expected to shift northwards and be replaced by climates that are currently associated with aspen forest, parkland and grassland ecosystems. In this study, we review the various processes that will mediate ecological responses to these projected changes in climate. We conclude that ecological transitions are unlikely to involve a gradual wave-like shift in ecotonal boundaries. Instead, we predict that ecological changes will lag substantially behind changes in climate and that individual ecosystem components will respond at different rates. In particular, if precipitation inputs are maintained as expected, then peatlands should exhibit considerable resilience to climate change and remain a dominant feature on the landscape in 2100. Because peatlands retain large amounts of water on the landscape their continued presence may in turn slow the rate of forest loss, especially the aspen component. Thus, ecological response to climate change in the western boreal region may involve a transition to a novel ecosystem that includes peatlands and aspen as dominant features -unlike anything that exists today. Moreover, this interim stage may remain in place well into the next century, potentially providing additional time for forest-dependent species to adapt.

Hydrologic impact of aspen harvesting within the subhumid Boreal Plains of Alberta

“…Thus, post‐harvest aspen regeneration may be impeded, with the potential for greater hydrologic impact than predicted here, particularly if changing climate also includes an increase in the frequency or intensity of large storms (Sillmann, Kharin, Zwiers, Zhang, & Bronaugh, ). However, widespread aspen decline may lag changes in climate (Schneider, Devito, Kettridge, & Bayne, ) and could be mitigated through silvicultural practices (e.g., periodic thinning and removal of diseased trees; Cerezke, ). Effective forest management in the future may increasingly require the use of combined monitoring–modelling studies that integrate the overall hydrologic interactions occurring among ecosystem components and permit evaluation of system responses over a wider range of atmospheric conditions than would be possible strictly through observational approaches.…”

Potential impacts of climate change on the habitat of boreal woodland caribou

“…Our conclusions depend on the assumption that key caribou habitat (forested peatlands) persists into the 2100s, given their resilience to warming and drying trends , Schneider et al 2016, McLaughlin et al 2017. Low-lying coniferous forests, in particular treed fens and bogs, are crucial for caribou as a source of winter forage and as refugia from wolves (Rettie andMessier 1998, Shepherd 2006).…”

“…Climate change in the boreal region will also lead to earlier snowmelt, moderate increases in summer precipitation, and greater drought frequency (especially in western regions; Lemke et al 2007, Price et al 2013. Wang et al (2017) have projected increases between 50% and 100% in the incidence of days with fire-conducive weather in the western boreal forest, and up to 150% elsewhere in Canada. The response of boreal forest ecosystems to climate change will be complex and likely lead to the emergence of novel ecosystems (Schneider et al 2016). Wang et al (2017) have projected increases between 50% and 100% in the incidence of days with fire-conducive weather in the western boreal forest, and up to 150% elsewhere in Canada. The response of boreal forest ecosystems to climate change will be complex and likely lead to the emergence of novel ecosystems (Schneider et al 2016).…”

“…Wang et al (2017) have projected increases between 50% and 100% in the incidence of days with fire-conducive weather in the western boreal forest, and up to 150% elsewhere in Canada. The response of boreal forest ecosystems to climate change will be complex and likely lead to the emergence of novel ecosystems (Schneider et al 2016). Therefore, vegetation change will occur primarily where disturbance events, including wildfire and insect outbreaks, cause widespread tree mortality (Johnstone et al 2016, Schneider et al 2016, Hogg et al 2017). The boreal forest in Alberta, Canada, is comprised two dominant terrain types: uplands characterized by a mixture of aspen (Populus tremuloides), white spruce (Picea glauca), and jack pine (Pinus banksiana), and lowlands characterized by extensive peatlands, tamarack larch (Larix laricina), and black spruce (Picea mariana).…”

“…The water table feedbacks inhibit vegetation change, which may allow peatlands to act as hydrologic refugia in spite of significant climatic warming (Price et al 2013, Schneider et al 2016. Negative feedbacks with peat decomposition, moss productivity, and moss surface resistance moderate water table decline in these systems .…”