This summer there have been a record number of forest fires in British Columbia, Canada. High temperatures and low rainfall have led to very dry conditions in the forest making them more susceptible to intense fires. Experts say that climate change is partly to blame for the increased drought and longer fire seasons and that this is becoming the new normal.
How are forest ecosystems affected by the changing climate conditions? Increased disturbances such as wildfires, insect attacks and diseases are imposing a variety of stresses on tree species and may ultimately lead to shifts in their distribution. Tracking changes to species distributions allows us to better understand how forests are responding to climate shifts and can help build their resilience to these and other disturbances in the future.
I moved to Vancouver, British Columbia five years ago for an MSc degree in Soil Science at the University of British Columbia. Since living here I have enjoyed spending time in forests and have wanted to learn more about their ecosystem processes and functions. The old growth forests found in the Marine West Coast Forest ecoregion are the most productive in western North America. They have a high leaf area index allowing the trees to take up lots of carbon from the atmosphere while also releasing water from the soil through their stomata.
My interest in the forest led me to pursue a PhD in the Faculty of Forestry at UBC. My research involves mapping tree species distributions and their resilience to extreme events such as drought and frequency of frost. To accomplish this I am using the process-based forest growth model 3-PG to determine how the forests are responding to changing climate conditions. The model uses climate data as well as knowledge of species growth requirements to determine what environmental constraints are most limiting on forest growth.
Combining these constraints with the recorded occurrences of tree species in a decision tree analysis allows us to map their distribution across the region. I compare where tree species are located in the past with where we predict their occurrence in a current and future climate. The model predictions show us in what areas species are exposed to increased stress leading to a decline in their range and where they are likely to expand with more favourable climate conditions.
Soil properties are also important in influencing tree species growth and distributions. I use maps of soil water availability and soil fertility to model the distribution of 20 common tree species of western North America. The soil information was derived by combining remotely sensed leaf area index values with knowledge of tree physiology to produce maps at a sufficient scale to make meaningful predictions on forest responses to environmental change.
With greater extremes such as drought and forest fires, we expect changes in forest ecosystems to occur in western North America. Outcomes of this study can contribute to the development of sustainable forest management practices by informing policy makers where increased disturbances will likely occur and identify those tree species that are most resilient in a future climate.
Blogpost submitted by Amanda Mathys (Canada) – amathys(at)alumni.ubc.ca
Picture courtesy Chris Gat
The content, structure and grammar is at the discretion of the author only.
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