We know that as the planet warms, forests will be affected in different ways. Some bad and some good, depending on the region. But what if the forest industry decided to help make forests adaptable to this changing climate by planting different species of trees? Would this make forest ecosystems more resilient? Would we be able to store more carbon in the forests? Would we even be able to boost harvests at the same time?
It has been hypothesized for some time that planting trees more likely to flourish in the new conditions would do all of these things, but according to new research this had never been tested for temperate or boreal coniferous forests (the sort that we get a lot of in Canada and the north of the US).
Forest researchers with the British Columbia Department of Forests, Lands and Natural Resource Operations, and the University of Wisconsin, Anouschka Hof, Caren Dymond and David Mladenoff, investigated what would happen if foresters switched up traditional tree planting strategies. They modelled a large, forested mountain valley called Copper-Pine Creek, near the town of Smithers in northwestern BC. Copper-Pine Creek was picked because it represents different forest ecosystems, tree species composition, forestry activities, and rates of natural disturbance by forest fires and pests.
They found that some species do indeed flourish in the new conditions, but best of all is not adding one single new species, but diversifying. It is a diversification of species in these new environments that most consistently boosts carbon stocks and enhances ecosystem resilience.
Modern simulations can take into account a remarkable set of interactions between different phenomena: tree species, biomass accumulation and decomposition, carbon sequestration, climate change, harvesting, disturbances and even seed dispersal. It’s like growing a forest in your computer, replicating many of the complexities of a forest in the real world.
They ran their simulations for a century-long period of 2015 to 2115 and at a one-hectare scale. They did this for three different climate forecasts under plausible greenhouse gas scenarios that have been predicted for BC. They found that the ability of our forests to sequester carbon is more dependent on precipitation changes than temperature changes. As well, if we stick to current planting practices, this will lead to low levels of carbon sequestration, tree species diversity and productivity of the ecosystem—the forests will be less resilient in the face of climate change.
Of all the novel species tested, the tree that gave the biggest boost to resilience was the lodgepole pine because it generally increased diversity, aboveground biomass, and growth. It also boosted harvest rates, likely due to the fact that this tree is ready to be logged at age 50, while the other tested species cannot be harvested until they are 80. Still, researchers are hesitant to cheer the lodgepole pine as increasing the amount of any type of pine is playing a sort of Russian roulette with beetle infestations. The mountain pine beetle suggests with its name the reason why. Researchers acknowledged even though the modelling did account for some level of damage caused by mountain pine beetle outbreaks, the levels produced might be underestimated.
The next step is to see whether the modelling work can be replicated with actual planting trials, and see whether the impact of pests matches that seen in the simulations. Given the rate of climate change we are already experiencing, the researchers believe it is possible now to move from the computer to the real world.
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