Can nutrients put the breaks on forest carbon capture?

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Increasing forest cover is widely promoted as a global solution to help mitigate climate change as forests are net sinks of carbon. In Canada, the Federal Government's objective is to plant two billion trees within the next 10 years to help meet greenhouse gas emission reduction targets. Forest growth and forest soil carbon sequestration, however, are highly dependent on the biogeochemical cycling of other nutrients, like nitrogen and calcium, which have been perturbed by centuries of anthropogenic activities. Furthermore, climate change will likely impact the health and composition of forests with further implications for net carbon storage. This research program will connect changes in nitrogen and calcium biogeochemistry with forest growth and health, focusing on southern Ontario, which has experienced widespread soil degradation because of acidic deposition and this region also receives the highest levels of nitrogen deposition in Canada. As the keystone species in southern Ontario, sugar maple health and growth will be targeted, but studies will include a range of other common hardwood tree species in Ontario. This research will encompass four complimentary projects that will enhance our understanding of the role of nitrogen and calcium in forest growth and what impact climate change may have on forest health. The research program will ask: 1. How are tree growth and forest health affected by atmospheric nitrogen deposition and soil base cation status?; 2. How is tree health affected by climate change?; 3. What are the short-term biogeochemical responses of forests growing on base-poor soil to calcium and/or nitrogen additions?, and 4. How will soil calcium levels change under harvest vs. no harvest scenarios? This research will utilize an existing database of more than 10,000 trees that are annually monitored at more than 100 long term forest monitoring plots and utilize innovative techniques like stable isotopes to disentangle potential biogeochemical mechanisms at play. It will combine extensive field sampling and experimental field studies with state-of-the-art biogeochemical models to assess the current forest condition and forecast future changes in forest growth and health under different climatic and management scenarios. The work will be conducted by a diverse and inclusive HQP team consisting of 3 PhD students, 2 MSc students, 4 undergraduate honors students and a research technician, all of whom will work with stakeholders to ensure that findings from these studies will be directly communicated and used to inform policy decisions. This work will enable a more accurate estimation of the future health and growth of hardwood forests, which is a vital component of government policy to combat climate change. It will also identify potential mitigation measures that will aid forest management decisions that may include the need for amendments, adjusted harvesting practices and/or changes in tree species composition.