Orographic Field Trip

Orographic Field Trip, Lauren and Megan

At 8am on Friday, October 30th, the UM’s 40th Wilderness and Civilization class set off on a journey for a firsthand experience of the phenomenal orographic effect. We all knew we were in for a treat as our Fearless Leader and conservation ecology professor Natalie Dawson took charge for the day.

         Our first stop of the 60 mile day put us out of our warm cars and into pouring rain at the Lolo ranger station to learn about the orographic effect. The orographic effect explains the drastic change in rainfall, weather, soil and species composition across the windward and leeward sides of large mountain ranges. On the windward side of a range, precipitation condenses. This creates heavy rainfall as the clouds are pushed into the windward slopes. Clouds lose much of their water as they travel into and over the peak of mountains. Thus, the leeward side receives extremely low amounts of precipitation.

Jackson refreshes his topographic map reading skills while pondering the orographic effect

 Once we had the basic concept of the effect down, everyone piled back into the vehicles and drove West to DeVoto Cedar Grove, where we began our lab. We scratched down notes as quickly as possible as the rain beat down on us.

Silas observing large woody debris on the windward side of the range in the Devoto Cedar Grove forest

Here we saw a luscious green temperate rainforest comprised of species such as old growth cedars, Douglas firs, liverworts, a variety of mushrooms, and many other species. My lab group was stoked about the mushrooms we’d found, and shared our excitement with Natalie. “So usually if the bottom is spongy like this, you can eat it,” Natalie explained. Andrew replied, “Wait Natalie, you’re saying that usually it would be okay for me to eat this right now but this may be like, a life or death thing here.” All in good humor, but a solid point still. Once we took down all crucial information-- latitude and longitude, species makeup, canopy structure, coarse woody debris, and evidence of disturbance-- we moved to our next site.

Natalie goofing off with Tessa, Andrew, and Cory in the Lolo Pass temperate rainforest

Transect number two was the peak of Lolo Pass, which also receives heavy rainfall and thus had similar species composition as DeVoto. When our work here was finished we headed down the leeward side of the range, finally escaping the rain. At Fort Fizzle we found entirely new species and forest structures—a forest that is drier and fire-dependent. The tree population consisted largely of Ponderosa, Aspen, Cottonwood, and Doug fir, and few woody debris were present. This type of environment intensified as we headed East to our last location, Blue Mountain. When we arrived, the orographic effect became extremely clear to me. In a short amount of time we had reached a dry open valley that received only 14 inches of rain each year; DeVoto receives 1,083 inches. Here, the only tree species we saw was Ponderosa. The understory was made almost entirely of cheatgrass.

The group heading out to explore the dry lands of Blue Mountain

         The rain, friends, learning and fun made for another fascinating field day for Widlerness and Civ.

Natalie teaching about riparian species along side of Lolo Creek at the Fort Fizzle site