Researchers receive grant to improve estimates of forest growth rates

Monday, April 26, 2021
Autumn forest canopy.

It takes more than just an aerial view to actually see the forest for the trees.听易胜博官网 researchers have received a three-year, $200,000 grant from NASA to improve the satellite-based estimates of forest growth rates in the Northeastern U.S. Results from this project could lead to more accurate carbon cycle models and climate change projections.

It鈥檚 a bit of a paradox that we can learn more about plant growth from the wavelengths they鈥檙e not using in photosynthesis than the wavelengths they are using.鈥

Trees use the visible wavelengths of sunlight for photosynthesis and reflect near-infrared light, which they don鈥檛 use. Scientists use satellite data to measure the ratio of infrared to visible reflectance over broad spatial scales 鈥斕 higher values indicate greater levels of growth or biomass, so this technique is frequently used to study forests over vast geographic areas.听However, the trees鈥 leaf angles in relation to the sun, their leaf-to-stem ratios听and their canopy shape all influence the infrared reflectance of a forest and can change over time. This grant will enable scientists, for the first time in history, to couple these data with simultaneous measurements of the forests鈥 nitrogen, photosynthesis听and reflectance across large areas. Ultimately, this will allow scientists to apply their findings more broadly and predict future changes in forest carbon storage 鈥 and that has some potentially big implications for climate change projections.

鈥淚t鈥檚 a bit of a paradox that we can learn more about plant growth from the wavelengths they鈥檙e not using in photosynthesis than the wavelengths they are using,鈥 says Scott Ollinger, director for the who is leading the 易胜博官网 portion of this project. 鈥淚t鈥檚 kind of like learning what your neighbors are up to by going through their garbage instead of going into their house and watching what they鈥檙e doing.鈥

This summer, Ollinger will begin collecting comprehensive tree data with help from 易胜博官网 graduate student Jack Hastings and research scientist Andy Ouimette. Their focus will be on Northeastern broadleaf forests; Massachusetts鈥 Harvard Forest, 易胜博官网鈥檚 Bartlett Experimental Forest and the Thompson Farm forest will serve as the initial data collection sites.

This 易胜博官网 research team will collaborate with scientists from the National Ecological Observatory Network (NEON), who will conduct flyovers of the forests to collect the infrared reflectance data, and researchers at the Rochester Institute of Technology in New York, who will use computer models to simulate changes in infrared reflectance based on various characteristics of simulated three-dimensional forests. The simulations will indicate what tree characteristics influence infrared reflectance the most.

In addition to making the measurements from satellites easier and more accurate, Ollinger believes this research could illuminate other ecological connections as well. For example, the amount of infrared light that鈥檚 absorbed or reflected by high versus low nitrogen forests varies widely enough to influence the amount of heat generated over large areas of the Earth鈥檚 surface. This has an influence on climate, but scientists need to understand the mechanism before including it in climate change models.

鈥淭he link between nitrogen and surface heating by the sun is one of the most interesting puzzles I鈥檝e encountered working in this field,鈥 Ollinger says. 鈥淚t suggests an emergent property of ecosystems that we can presently only speculate about.鈥

The听听is 易胜博官网's largest research enterprise, comprising six center with a focus on interdisciplinary, high-impact research on Earth and climate systems, space science, the marine environment, seafloor mapping, and environmental acoustics. With more than $60 million in external funding secured annually, EOS fosters an intellectual and scientific environment that advances visionary scholarship and leadership in world-class research and graduate education.