August 25, 2019
Ecology Blog 2: Fallen with the wind
Here comes the second blog by the ecology group！ We have had a good time walking in the Hoh Temperate Rain Forest in the Olympic National Park, with Joseph Murray from JMurray Forestry and Precision Forestry Cooperative (PFC) Board Member. He told us about the impact of the 1921 Great Olympic Blowdown in this area.
Photo from Washington Forest Protection Association
From Joseph’s story and some readings, we knew that on 29 January 1921 a windstorm along the northern Oregon and Washington coastlines caused a huge loss of timber on the Olympic Peninsula, which was called “Great Olympic Blowdown”. An official report at the North Head Lighthouse, on the north side of the mouth of the Columbia River, indicated a sustained wind of 98 kt, with estimated gusts of 130 kt before the anemometer was blown away. In this windstorm, over 40% of the trees were blown down over the southwest flanks of the Olympic Mountains with at least a 20% loss along the entire Olympic coastline (Clifford Mass and Bridget Dotson, 2010).
Figure from Clifford Mass and Bridget Dotson, 2010
We learned that some of the blown-down trees will continue to serve the whole forest system as nurse logs, which we had seen a lot in the rainforest. Then, after a long time, those trees will decomposed and turned into soils. Most of the blown-down trees in 1921 have now become a thick layer of organic matters.
These interesting phenomenon remind us of a famous Chinese poem about the deadwood : “Though turned to mud, they would still protect other blossoms the next spring”. Therefore, we think that wind may be an important ecological factor in the forest system. In long-term scale, the big wind and the recovery of forest must have reached a balance. However, with climate change (maybe more extreme storms) and human activities (human many remove those blown-down trees), this balance may be broken. We want to learn what conditions the Pacific Northwest area are in. What are the functions of winds ? Do the winds here become bigger ?
Generally, we thought about two kinds of winds. The chronic winds seem to have impacts on the distribution and the long-term growing patterns of the trees. The catastrophic wind will blow down some of the trees and cause damage or death. We will focus on the effect of the blowing down of the trees, because we have seen some of them in the rainforest.
It is not only winds will put down a tree, but in some way the fallen trees will have the same effects below. Especially, when there were no logging and artificial removal of the fallen trees, winds seem to be important causes for them.
Forest gap photo by Yuancong Gou
First of all, as Joseph mentioned, the heavy wind blew down a big tree and then created a window called forest gap which played an important role in the cyclic succession of forest.
Gaps usually mean more open space. A lot of vegetation beneath the blown-down tree before could absorb more sunlight and grow better. Then, the seed spread by wind will naturally face smaller spread resistance which will be beneficial to protect the biodiversity. However, our group think that it may be a double-edged sword. For example, wildlife that prefer a dark and humid environment will definitely get into some trouble.
Photo by Wenjing Zhu
Apart from the forest gaps, the blown-down tree itself can provide a stage for new life. Hemlock and spruce seedlings will be able to live on the tangled forest floor, absorbing nutrients, moisture and warmth from the decaying trunk. After their roots reaching the soils, new trees often seem to stand up as the nurse log moldering away.
It seems that winds do have a great impact on the forest ecosystem, which means the change of the wind will also change the forest. The elevation and the topography will definitely influence this kind of effect. We want to know whether that is happening in this area.
We searched some information about the wind in Pacific Northwest (PNW). According to a research (Bradford Griffin,2010) ,which the data of winds were collected from 186 monitoring station in PNW and wind speed distribution generated from 50 years of observation data for Portland International Airport is representative of wind speeds in PNW. The conclusion is that the wind speed trend of coast locations in the PNW follows a cyclic pattern with an approximate period of nine years, while mainland sites have a downward wind speed trend.
Figure from Bradford Griffin, 2010
With the changing climate, we do not know what kind of impact will be put on the forest through the changes of winds. But it is known for sure that studying on the pattern of winds will play an important role in maintaining forests ecological balance. We are looking forward to more efforts by researchers from different fields.
References
- Mass, Clifford , and B. Dotson . “Major Extratropical Cyclones of the Northwest United States: Historical Review, Climatology, and Synoptic Environment.” Monthly Weather Review 138.7(2010):2499-2527.
- “The Great Blowdown” strikes Washington coast on January 29, 1921.
- Edwin Van Syckle, They Tried To Cut It All: Grays Harbor — Turbulent Years of Greed and Greatness (Seattle: Pacific Search Press, 1980), 192-195;
- Wind speed variability and adaptation strategies in coastal areas of the Pacific Northwest, Bradford Griffin, 2010
