Taking the Temperature of Forest Canopies
Christopher Still's lab is working to understand the temperature of forest canopies in Oregon using thermal imaging technology similar to that found in night-vision goggles. The project, supported by the Macrosystems Biology program at the National Science Foundation, is being led by Still and postdoc Youngil Kim, who arrived at OSU in early August after receiving his Ph.D from Canada's McGill University.
Temperature is a primary environmental control on biological systems and processes at a range of spatial and temporal scales. Its influence is fundamental, ranging from controls on enzymatic reactions to ecosystem biogeochemistry to large-scale species distributions. Temperature is also a fundamental characteristic of climate. Indeed, much of the concern about the impact of climate warming on the biosphere is motivated by the pervasive influence of temperature on organisms. Although scientists often focus on air temperature, the radiative or skin temperature of an organism such as a plant is actually more relevant in many cases. However, until now direct measurements of organismal temperature from thermal imaging have been challenging due to sensor and computational limitations. We have recently acquired a thermal camera and deployed it at the Metolius intermediate ponderosa pine flux tower site near Sisters, OR (operated by Bev Law’s group and supported by the Department of Energy)
Work on this project will directly inform a variety of ecological questions, such as the link between leaf temperatures and carbon assimilation in various ecosystems. This project will also support numerous applied research questions, and has wide implications for the biological response of ecosystems in a warming world. Particular focus will be on diagnosing the thermal responses of ecosystems to drought heat waves, freezing, and wind chill.
he images below, taken on October 25, 2013, show initial results from our deployment. We have paired an image from a digital camera with the complementary image taken by our thermal camera. You can see a number of interesting patterns in the thermal image, such as the hotter pine trunks and branches and the cooler leaves (the temperature scale is in degrees Celsius). These patterns change rapidly, and the trunks and woody parts can also be colder than the foliage. We have just begun to analyze the first few weeks of thermal imagery and hope to eventually collect an entire year’s worth of thermal imagery at 5 minute resolution – to our knowledge such data collection is unprecedented. It will provide fundamental knowledge about the thermal regime experienced by this canopy, and help us better understand connections between organismal temperature and biological processes like flowering, photosynthesis, respiration, and transpiration.
Fig.1 (below). View of digital camera image (taken on 10/25/2013 at 11:26 a.m.) at the Metolius pondersa pine flux tower site. The red square outlines the area captured by the thermal camera.
Fig. 2 (below). Comparison of the same region of interest between the digital camera image (10/25/2013 at 11:26 a.m.) vs. thermal image (10/25/2013 at 11:25 a.m.) at the Metolius flux tower site.