Temperature and Canopy Cover in Micro Climates

 

Background: Forests and parks are all made up of their own unique ecosystem. There are many different moving parts that create what you and I see and feel when we are hiking on paths, or having a picnic in a park. What is one of the major “topics” or factors that make up this ecosystem? Microclimate; Microclimate is the combination of climatic conditions measured in localized areas near the earth’s surface (Geiger 1965). Some of the variable that make up microclimate that are measured to see what the microclimate is are temperature, light, wind speed, moisture (dew point, humidity) and vegetation and canopy cover. These variables are all important in understanding why and how an ecosystem is the way it is, and which factors affect and change the different variables. In our study, Sofia Linden and I (Marissa Weileder) decided to measure and look at the correlation between canopy cover and temperature of the air in the Riverview Natural Area (RVNA), which spans about 150 acres from roughly 50’ elevation near the Willamette River to roughly 550’ elevation as it approaches Palatine Hill Road. Sofia and I were very close to the top of RVNA, at about 500’ feet elevation.  

 

Research Question: Our research question, in it’s basic format, is “How Does Canopy Cover Affect Air Temperature?”

 

Procedure: To collect our data, we were given an iPad mini and a Kestrel Drop D3 portable weather data logger. The Kestrel devices measure temperature, humidity, and dew point and the purpose of the iPad was so that we could note, on a GPS map app (Fulcrum) that allows you to create a “survey” for a given area and collect data at different points within that area, the temperature, dewpoint and humidity, canopy cover, ground cover, sunlight, human interference, and amount/frequency of English Ivy. We walked along path 4 of RVNA (shown on area map) collecting this data at different points, trying to get a variety of areas.  Canopy cover was rated by observation on a scale of one to four.  A rating of one meant the canopy cover was 0-25%, 2 meant 25-50%, 3 meant 50-75% and 4 meant 75-100% canopy cover.  To understand the data collected, we downloaded the data from the Lewis and Clark ENVS log in of the Kestrel website and plugged this data into a spreadsheet on google documents.  We created two bar graphs, one with all the temperatures, and one with the average of the temperatures for each rating of canopy cover.  This way we could visually picture any significant changes in temperature among canopy covers in a broader and more specific light.

 

Results: Looking at the chart “Relationship Between Canopy Cover & Air Temperature,” you can see that overall the amount of canopy cover does affect the air temperature. Generally, for the areas with 0-25% canopy cover, the temperature was much higher than the areas with 75-100% canopy cover. There are a few outliers in the 50-75% canopy cover range where the air temperature is still pretty high even though the canopy cover was pretty dense, and compared to the other 50-75% markers, they’re pretty different. If you take a look at the graph “Average Temperature for Percent Range Forest Cover,” you can see that based on the averages that the average temperature for the 0-25% forest cover range is slightly higher than the average temperature for the 25-50% forest cover range, and so on. The 50-75% forest cover range average temperature is slightly higher than the 25-50% and 75-100% forest cover ranges, but not higher than the 0-25% forest cover range average temperature.

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Discussion: Some discussion questions after the results of this lab could be what specific factors and/or variable are creating the higher average temperature for the 50-75% forest cover range? It could be wind speed, ground vegetation cover, human interference or other, but how would we measure those in relation to canopy cover and air temperature? Furthermore, we had to collect data on canopy cover purely on observation and in broad categories with a large range of percentages.  This could lead to subjective results. However, using this information about the correlation between canopy cover and air temperature could lead to further investigations about how this correlation impacts different aspects of forest ecosystems.

 

Sources:

 

Chen, Jiquan, Sari C. Saunders, Thomas R. Crow, Robert J. Naiman, Kimberley D. Brosofske, Glenn D. Mroz, Brian L. Brookshire, and Jerry F. Franklin. 1999. “Microclimate in Forest Ecosystem and Landscape Ecology Variations in Local Climate Can Be Used to Monitor and Compare the Effects of Different Management Regimes.” BioScience 49 (4): 288–97. http://doi.org/10.2307/1313612.

Corell, Robert W. 2006. “Challenges of Climate Change: An Arctic Perspective.” Ambio 35 (4): 148–52.