Background: How Does the Forest Affect Snow Storage in the PNW?

By utilizing field observations collected by volunteer citizen scientists and students in central Idaho and a network of collaborating snow study sites, we are assessing forest effects on snow storage across the Pacific Northwest.

Trees intercept snow, which leads to less snow accumulation in forests (this is one of the reasons for tree wells, which backcountry skiers know well). Once the snow is on the ground, trees also provide shading from the sun and the wind (which reduces melt), but the trees are also warmer than the sky, which can increase melt (this is another reason for tree wells). Thus, the net effect of the forest on snowpack duration varies with climate, topography, and forest density.

Predicting Snow Duration

Previous investigations of snow duration in forests indicate that average winter temperature is a key predictor of whether the presence of forest cover will accelerate or delay snow disappearance. However, local effects such as topographic position (e.g., north-facing vs. south-facing slopes), weather patterns (e.g., high winds), and forest characteristics (e.g., canopy density) also have an important influence on how the presence of or type of forest affects snow duration.

The Northwest Climate Science Center is supporting our work to develop a conceptual model for considering all of these local-scale influences in order to help guide forest management decisions now and under different climate warming scenarios. Understanding and predicting the effect of forest cover (and density) on snow duration is critical for land and water management decisions such as where to thin forests to minimize fire risk, where to suppress fires, and how to respond to insect outbreaks.

To test and refine this model, we need observations of where snow lasts longer in the forest versus the open from many sites in different regions that capture a range of climates and terrain types (together, having such a variety of observations is referred to as “spatially-distributed”). We have snow data from several field sites around the region thanks to collaborators at Oregon State University, University of Idaho, and Utah State University. However, we needed observations in more locations, so we ran a 4-year campaign to utilize citizen scientists.

Data

The observational data compiled for this project are publicly available via the USGS ScienceBase archive.

Learn More

Read more about the conceptual model or check out our related publications. You can also read about our experiences with citizen scientists.

Watch a webinar presented in 2016 by Susan that describes a conceptual model framework based on our results in the PNW.

Watch a talk about the inception of this project that Susan presented at the 2013 PNW Climate Science Conference.

Material contained here and within the embedded links is based upon work supported by the Northwest Climate Science Center. Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the funding agency.