Impact of planting trees on abandoned farmlands on diversity and carbon sequestration

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The establishment of plantations on abandoned farmland offers good opportunities to sequester carbon into plant biomass and soils. Plantations established on abandoned farmlands can be beneficial to biodiversity compared to cultivated lands, by accelerating the invasion and installation of native plants where ecological barriers to plant succession can halt or slow down colonisation. The potential for plantations to fulfill ecological services typically found in the ecosystems they are replacing (fallow lands, cultivated lands or forests) is however largely unknown. This study aims to determine the effects of establishing hybrid poplar and white spruce plantations on vascular and non-vascular plant functional diversity and species composition, soil microbiome and carbon content, in relation to the previous use of the sites and in comparison with surrounding forests and unplanted abandoned farmlands. We also aim to compare biodiversity along a chronosequence of planted (white spruce) and comparable unplanted fallow lands. Finally, this study aims to identify functional root traits that increase carbon sequestration in deep soil layers and in stable forms, and how the soil microbiome interacts with these traits.Already established white spruce and hybrid poplar plantations will be samples according to their previous land use (poplar) and age (spruce), in order to characterize their plant composition and soil microbiome, in comparison with unplanted abandoned farmland and surrounding forest. Soil carbon will be measured in the hybrid poplar plantations along with root functional traits of several clones that have slow to rapid growth rates, in order to link these traits with long term carbon sequestration. In the end, this project will contribute to make informed decisions and silviculture investments into plantations, according to ecological criteria and optimize outcomes better targeted to Canada's objectives of using trees to compensate CO2 emissions and manage diversity over the landscape.