Carbon sequestration in the Boreal Plain ecozone through the conversion from agriculture to agroforestry
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Agroforestry systems have been considered in helping to mitigate climate change. Through this study, we estimated the potential carbon sequestration of wood fiber plantations in Saskatchewan Gray Luvisolic and Dark Gray Chemozemic/Luvisolic soils and also identified research needs to improve future estimations. Estimations were done for all future scenarios of approximately 500 years. Scenarios differed in species composition, agroforestry adoption rate, carbon pools considered, and different approaches to account for forest products stocks. The time-step used in all accountings was the rotation length. The first set of scenarios consisted of single species wood fiber plantations, with all available farms converting 10 ha each to wood fiber plantations at one time. For these scenarios, carbon stocks were accounted in 2 pools (aboveground and belowground). Such scenarios resulted in hybrid poplar wood fiber plantations with highest carbon sequestration potential (91.3 Mt C), followed by trembling aspen (19.1 Mt C) and white spruce (17.8 Mt C). For similar scenarios, but accounting for carbon stocks in 3 pools (aboveground, belowground, and forest products), trembling aspen and white spruce had similar carbon sequestration (0.4 Mt C), followed hybrid poplar ( -9 Mt C). This scenario for hybrid poplar was reproduced and the production approach was used to account for the forest products pool; and this resulted in -2.3 Mt C sequestered. Scenarios that considered a single species in wood fiber plantations at an average adoption rate 0.33% farms per year (10 ha per farm), and included carbon stocks in 2 pools (aboveground and belowground), hybrid poplar had the highest carbon sequestration potential (65.5 Mt C), followed trembling aspen (15 Mt C) and white spruce (13.9 Mt C). For a similar scenario, but for half the farms adopting trembling aspen and other half adopting white spruce wood fiber plantations, the potential carbon sequestration was 15 Mt C. One scenario considered half the area planted to trembling aspen and half to white spruce, all at once (10 ha per farm), and accounted for carbon stocks in 2 pools (aboveground and belowground). This resulted in 18.5 Mt C sequestered. The most important research needs include growth curves, conversion and expansion factors, and soil organic carbon measurements. These data are needed for each species, agroforestry design, and growth conditions (such as spacing, site quality, and stand management).