Peat carbon stocks in the southern Mackenzie River Basin: uncertainties revealed in a high‐resolution case study

• Published in: Global Change Biology
• Main Authors: BEILMAN, DAVID W., VITT, DALE H., BHATTI, JAGTAR S., FOREST, SILVIE
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2008
• Subjects: Canada; Mackenzie River; Mackenzie Basin; Mackenzie river
• Online Access: http://dx.doi.org/10.1111/j.1365-2486.2008.01565.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1365-2486.2008.01565.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2486.2008.01565.x

Abstract The organic carbon (C) stocks contained in peat were estimated for a wetland‐rich boreal region of the Mackenzie River Basin, Canada, using high‐resolution wetland map data, available peat C characteristic and peat depth datasets, and geostatistics. Peatlands cover 32% of the 25 119 km 2 study area, and consist mainly of surface‐ and/or groundwater‐fed treed peatlands. The thickness of peat deposits measured at 203 sites was 2.5 m on average but as deep as 6 m, and highly variable between sites. Peat depths showed little relationship with terrain data within 1 and 5 km, but were spatially autocorrelated, and were generalized using ordinary kriging. Polygon‐scale calculations and Monte Carlo simulations yielded a total peat C stock of 982–1025 × 10 12 g C that varied in C mass per unit area between 53 and 165 kg m −2 . This geostatistical approach showed as much as 10% more peat C than calculations using mean depths. We compared this estimate with an overlapping 7868 km 2 portion of an independent peat C stock estimate for western Canada, which revealed similar values for total peatland area, total C stock, and total peat C mass per unit area. However, agreement was poor within ∼875 km 2 grids owing to inconsistencies in peatland cover and little relationship in peat depth between estimates. The greatest disagreement in mean peat C mass per unit area occurred in grids with the largest peatland cover, owing to the spatial coincidence of large cover and deep peat in our high‐resolution assessment. We conclude that total peat C stock estimates in the southern Mackenzie Basin and perhaps in boreal western Canada are likely of reasonable accuracy. However, owing to uncertainties particularly in peat depth, the quality of information regarding the location of these large stocks at scales as wide as several hundreds of square kilometers is presently much more limited.