Boreal forest shows important tree density variability and a consequently fluctuating forest carbon stock. In Quebec, the continuous boreal forest has been subjected to scattered regeneration failures following locally high frequency disturbances, converting dense stands into stable lichen woodlands (LW) that shows reduced carbon stocks. In the last two decades, simulations and field studies demonstrated an interesting potential for afforestation of LWs, and a consequent carbon sequestration enhancement. However, some aspects of the carbon budget of an afforested LW are not yet quantified. Notably, scarification prior to planting, which is necessary for good seedlings survival and growth, is expected to cause important carbon loss in the forest floor. But this phenomenon is poorly quantified in these ecosystems, as reflected by the fact that it is not accounted for in the carbon budget model of the Canadian forest sector (CBM-CFS3). Therefore, the objective of this study is to quantify the forest floor carbon dynamics following scarification in the context of LW afforestation. A chronosequence of 11 LWs having 3 to 18 years since afforestation was sampled using volumetric hammer soil corer to assess the whole forest floor profile of four different microsites: furrows, ridges, undisturbed spacings and contiguous controls.
Results/Conclusions
Results shows no difference in the carbon density between undisturbed spacings and controls, but in the short term, there is an important increase in the ridges and an important decrease in the furrows, both mitigating with time. No significant difference in the total forest floor carbon was found between scarified LW and control, irrespective of time. As a time trend was nonetheless noticeable, a sigmoidal model was fit to the percentage of carbon recovery with time. This model indicates that 10 % of the total forest floor carbon is lost in the first three years after scarification, but all of it is recovered within 10 years. These unexpected result strengthens the previously performed afforested LW carbon simulations as these neglected the effect of scarification, and supports LW afforestation as a carbon sink provider. Given that up to 1.6 million hectares of open woodlands are theoretically available to be afforested, it could likely constitutes a new climate change mitigation tool.