Large Soil Carbon Storage in Terrestrial Ecosystems of Canada

Abstract

Terrestrial ecosystems of Canada store a large amount of organic carbon (C) in soils, peats and plant materials, yet little is known about the C stock size and distributions, both spatially and in various C pools. As temperature rises, C is becoming available for disturbance, decomposition and eventual release into the atmosphere, which makes the quantification of C stocks in terrestrial ecosystems of Canada of high interest for the assessment of climate change impacts and conservation efforts. We used a large number of field measurements, multisource satellite, climate and topographic data and a machine learning algorithm to produce the first wall‐to‐wall estimates of C stocks and uncertainties in plants and soils of Canada at 250 m spatial resolution. Our findings show that above and belowground live biomass and detritus store a total of 21.1 Pg of carbon (Pg C). Whereas the Canadian soils store 306 (±147, 90% confidence interval) Pg organic C in the top 1 m, 98 Pg C of which are stored in peatlands, confirming that the soil organic C dominates terrestrial carbon stocks in Canada. We also find previously under‐reported large soil organic C stocks in forested peatlands on the boreal shields of Canada. Given that Canada is warming twice the global average rate and Canadian soils store approximately 20.4% of world soil C stocks in top 1 m, initiatives to understand their vulnerabilities to climate change and disturbance are indispensable not only for Canada but also for the global C cycle.

Multi-objective optimization can balance trade-offs among boreal caribou, biodiversity, and climate change objectives when conservation hotspots do not overlap

“…For example, avoiding peatland disturbance—including peatlands found in the boreal region—is estimated to provide the second largest opportunity for nature-based climate mitigation in Canada out of the 24 possible approaches assessed by Drever et al 12 . Protection of existing soil carbon stores in Canada is of particular importance, both at home and globally, with soil carbon stores making up an estimated 96% of Canada’s organic carbon stocks and 20% of the world’s soil carbon stores 37 .…”

Self-potential time series reveal emergent behavior in soil organic matter dynamics

“…This discharge contributed to extensive deposition of medium- to fine-grained glaciofluvial channel sands along the slopes of the river valley. As water levels fell in response to incremental icesheet recession and changes in drainage routes of the pro-glacial lakes, subaerial exposure of the channel sand deposits contributed to the development of humo-ferrric podzol soils (Canadian soil classification scheme), which dominate over much of the upper Ottawa Valley region, including the Meilleurs Bay locality 4 , 17 . At the Meilleurs Bay, a series of terraces between 129 and 141 masl document brief fluctuations in river height during the recession of the Laurentide Ice Sheet 36 .…”

“…The vast quantity of carbon stored as organic matter in the top 3 m of soils is greater than amounts that exist in the atmosphere and terrestrial vegetation combined 1 – 4 . Because of this, even a small change in the biogeochemical processes that contribute to the conversion of soil organic matter (SOM) into greenhouse gases such as carbon dioxide or methane could further exacerbate global climate change even as mean temperatures rise and extreme variations in rainfall become more frequent 5 .…”

“…Because of this, even a small change in the biogeochemical processes that contribute to the conversion of soil organic matter (SOM) into greenhouse gases such as carbon dioxide or methane could further exacerbate global climate change even as mean temperatures rise and extreme variations in rainfall become more frequent 5 . Higher turnover rates of SOM in surface soils and emission of greenhouse gases also threaten the vertical transport and long-term sequestration potential of organic carbon in deeper soil horizons where radiocarbon ages are commonly as old as one thousand to more than ten thousand years 1 , 4 , 6 . Investigation of these interconnected vulnerabilities in SOM dynamics has exposed significant challenges to researchers not only in terms of how to integrate traditional physical, chemical, and biological measurements in a quantitative manner, but also how to reduce the tremendous amount of time spent on sampling for multiple analyses.…”

Effective conservation decisions require models designed for purpose: a case study for boreal caribou in Ontario’s Ring of Fire

“…The Hudson Plains of Northern Ontario, Canada, is one of the largest intact wetlands and peatland carbon stores on the planet (Ibisch et al, 2016;Poley et al, 2022;Sothe et al, 2022;Tootchi et al, 2019). This region is rich in valuable minerals and is a target for resource extraction and economic development (Carlson and Chetkiewicz, 2013;Far North Science Advisory Panel (Ont.)…”