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4. Fall Leaf Colors: What They Tell Us about Tree Health

Fall Leaf Colors: What They Tell Us about Tree Health

Research Issue

Colorful fall foliage holds tremendous public and media interest, with tourism adding billions of dollars to the U.S. economy every year. But in addition to their aesthetic and economic values, fall tree colors may provide insights into how some trees survive environmental stresses. These stresses can include ultraviolet-B radiation, drought, low temperatures, nutrient deficiency, wounding, pathogen infection, and ozone exposure. This knowledge is particularly important as invasive pests, climate change and sustained air pollution threaten the health of many tree species.
Although the biological roles of green leaf pigments (chlorophylls) are well understood, much less is known about the red, blue or purple pigments called anthocyanins. They may serve as a “light screen” that helps leaves to continue photosynthesis during autumn. They may also protect leaves from stresses such as cold and drought.

Our Research

By studying trees such as the sugar maple, Northern Research Station scientists are identifying factors that stimulate anthocyanin production during autumn and in response to environmental stress. We are also evaluating the possible ecological benefits of anthocyanin production in senescing (withering) leaves. Past Northern Research Station research has evaluated factors such as mineral nutrition, carbohydrate concentration, and water content that influence leaf color development. Other studies have used experimental manipulations such as refrigerating specific branches and removing strips of bark around an entire branch or trunk, creating stresses that are similar to wounding and insect or fungal damage.

Expected Outcomes

Northern Research Station scientists hope to better understand the connections between environmental stress exposures and anthocyanin production. In turn, this may provide better insights into the role that anthocyanin plays in trees’ responses to stress.

Research Results

Schaberg, Paul G.; Murakami, Paula F.; Butnor, John R.; Hawley, Gary J. 2017. Experimental branch cooling increases foliar sugar and anthocyanin concentrations in sugar maple at the end of the growing season. Canadian Journal of Forest Research. 47(5): 696-701.

Neufeld, Howard S.; Poindexter, Derick B; Murakami, Paula F.; Schaberg, Paul G. 2011. Observations on the relationship between above- and below-ground anthocyanin production in Galax urceolata (Poir.) Brummitt growing in sun-exposed and shaded locations. Castanea. 76: 84-98.

Archetti M., T. Döring, S. Hagen, N. Hughes, S. Leather, D. Lee, S. Lev-Yadun, Y. Manetas, H. Ougham, P. Schaberg, H.  Thomas. 2009. Response to Sinkkonen: Ultraviolet reflectance in autumn leaves and the un-naming of colours. Trends in Ecology and Evolution 24:237-238173. https://doi.org/10.1016/j.tree.2009.01.007.  

Murakami, P.F.; Schaberg, P.G.; Shane, J.B. 2008. Stem girdling manipulates leaf sugar concentrations and anthocyanin expression in sugar maples trees during autumn. Tree Physiology. 28: 1467-1473.

Schaberg, P.G.; Murakami, P.F.; Turner, M.R.; Heitz, H.K.; Hawley, G.J. 2008. Association of red coloration with senescence of sugar maple leaves in autumn. Trees. 22: 573-578.

Murakami, Paula F.; Turner, Michelle R.; van den Berg, Abby K.; Schaberg, Paul G. 2005. An instructional guide for leaf color analysis using digital imaging software. Gen. Tech. Rep. NE-327. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northeastern Research Station. 33 p.

Schaberg, P.G.; Van Den Berg, A.K.; Murakami, P.F.; Shane, J.B.; Donnelly, J.R. 2003. Factors influencing red expression in autumn foliage of sugar maple trees. Tree Physiology. 23: 325-333.

Research Participants

Principal Investigator

• Paul Schaberg, US Forest Service – Northern Research Station, Research Plant Physiologist

Research Partners

• Paula Murakami, US Forest Service – Northern Research Station, Biological Sciences Technician
• John Butnor, US Forest Service – Southern Research Station, Research Plant Physiologist
• Gary Hawley, The University of Vermont, Senior Researcher