A Comparison of Wildfire Adaptive Traits in Juvenile Conifers of the Northern Rockies

Wildfire is an importance disturbance that continues to shape the ecosystems of the Northern Rockies and Interior Northwest through varying patterns of frequency and severity. Due to historical fire suppression and the hotter and drier conditions brought upon by anthropogenic climate change, wildfire frequency and severity is increasing. These increases will alter vegetation structure and composition, but the degree to which is unknown. Understanding how individual plant traits that reduce fire-related mortality differ between species and change with tree age can offer insight into how these vegetation communities will shift. Two traits associated with increased wildfire survival are thicker bark and quicker juvenile height growth. The purpose of this study is to quantify how bark width and tree height vary among juveniles of three conifer species and identify if there are tradeoffs between bark width and height growth. To determine which species use which strategies, I will measure bark width and tree height for 300 juvenile western larch (Larix occidentalis), Douglas-fir (Pseudotsuga menziesii), and ponderosa pine (Pinus ponderosa) that established following wildfires. These seedlings were destructively sampled across field sites in the Northern Rockies and Interior Northwest including Montana, Idaho, Washington, and Oregon from areas that burned 5-20 years ago. Using the computer program ImageJ, I will measure bark width from images of cross sections at the root-shoot boundary. Then I will compare bark width and height data collected in the field to tree ages. This study will help to identify which species has the highest likelihood of surviving wildfire at the juvenile stage and thus may be more successful in a future with more frequent fire. Furthermore, it can help inform choices land management agencies make about which species to replant following a fire