Native aspen carbon cache: quantifying carbon differences under copses in the black soil zone of the Canadian Prairies

Understanding the carbon footprint of Canadian agriculture is imperative for the developing carbon market. Agroforestry systems are seen as nature-based carbon sequestration solutions to achieve net-zero agriculture, yet very little research has been done into native woody vegetation. Native woody vegetation, often growing in and around trembling aspen (Populus tremuloides) copses, are diverse vegetative communities of tree, shrub, grass, and forb species. This study aims to be the first to quantify the carbon density under native copses of the Canadian Prairies. The decomposing litter layer and the top 60 cm of mineral soil were collected in 72 different sampling locations across six Black soil zone copses of Saskatchewan. Samples were collected along the grassy edges and under living aspen and shrubs within the copses. Soil samples were divided by visible horizon, and total, organic, and inorganic carbon were quantified from each layer. There was no significant difference in carbon density within the copses, and as such, carbon budgeting can assume a carbon density value of 29.90 kg TC m⁻². This carbon density allows an estimated total of 396 Tg TC to be calculated as stored under native copses in the Black soil zone of Saskatchewan (13,233 km²). The carbon at the edge of the copses was significantly less dense, at 21.56 kg TC m⁻², but merits inclusion in carbon budgets as levels are significantly higher than surrounding agricultural fields. This study highlights the importance of including native copses in Canada’s carbon budget.