Graeme Berlyn

Graeme P. Berlyn

E. H. Harriman Professor of Forest Management and Physiology of Trees


Berlyn’s dissertation involved the ecophysiology and morphology of trees growing on sites of varying stress levels. It examined how site quality affected the ability of the trees to form reaction wood in response to the mechanical stress of lean.  It analyzed the nature and properties of the xylem formed under these different conditions.  This work also resulted in one of the first papers to use allometric equations to examine the relationship between tree crowns and stems.  Since that time Berlyn and his students have studied factors affecting tree growth, xylem structure, and leaf functional traits in many countries (US, Costa Rica, Panama, Sri Lanka, Puerto Rico, Venezuela, Jamaica, Central African Republic, Korea, Japan, India, Mexico) and along many types of environmental gradients including mountain ranges from the Andes to the Brooks Range in Alaska and to the Himalayas.  These ecophysiological and anatomical studies also covered changes along latitudinal gradients along the east coast of the U.S. and in Alaska.  Combined these elevational and latitudinal gradients represent natural experiments in climate change for species and ecosystems.  Professor Berlyn also pioneered in the development of non-hormonal plant biostimulants.  These improve the growth, yield, and stress resistance of plants while reducing the need for inorganic fertilizers that readily contaminate the ground water.  In addition, Berlyn is part of an international group led by Dr. Anitra Thorhaug that studies carbon sequestration by sea grasses and mangroves. 

Our main goal is to deepen knowledge of the ways in which plants respond to the environment in terms of different traits (genetic, physiological, anatomical, and morphological). We examine these traits at different levels of biological organization, viz., molecular, cellular, organ, organismal and at the forest level. We look at different modes of response such as phenotypic plasticity, the capacity of an organism to change in morphology and physiology in response to environmental signals, and genetic mechanisms as revealed in common garden experiments and DNA analysis. The techniques we have used are cellular (cytophotometry, DNA microsatellites & microarrays, and image analysis of cellular and tissue level changes), light and carbon processing (photosynthesis, spectral reflectance, chlorophyll fluorescence, stable isotopes, etc), water relations, and growth analysis. One of the ways we investigate these responses is to use natural gradients of environmental stress such as along elevational gradients in mountains. High elevation sites are indicator ecosystems for a variety of stressors such as acid rain, global warming, grazing by domestic animals and wildlife, recreational use, commercial development, and pollution by toxic chemicals. We also study changes along microtopographic transects such as ridge tops, midslope and bottomland sites. Even these finer environmental differences are recorded in the structure, optical properties, and function of leaves, enabling determinations on such problems as what species are optimally adapted to each of these types of habitats under various conditions. Within the crowns of trees and in cross sections of the forest canopy there are environmental gradients, which are reflected in the way these aggregate structures process light. In turn structural changes mirror these gradients and can be studied using invasive and non-invasive techniques. We, along with colleagues and students, have conducted studies in New England, Canada, Sri Lanka, Panama, Peru, Mexico, Costa Rica, Puerto Rico, Africa, and India. In addition to the field components we also conduct controlled experiments in the Greenhouse and controlled growth rooms in order to more precisely isolate effects of environmental factors such as light quantity and quality, nutrition, competition, and water relations. Additional interests are plant embryology, biotechnology, genetic stability, interaction of environment and nuclear genome, biostimulants and mineral nutrition, cytochemistry, quantitative microscopy and microtechnique.

My current research includes anatomical, physiological, and optical properties of leaves in relation to: (a) light intensity and quality, (b) distribution in tree crowns, (c) nutrient status, and (d) ecology and silviculture. The second current project concerns the development and use of organic biostimulants to maintain optimum plant growth while reducing fertilizer requirements and increasing natural stress resistance with respect to water, disease, insects, and toxic substances. I was one of the originators of the biostimulant concept for amplifying plant growth and stress resistance. Current work involves adding beneficial microbes (or their byproducts) to the biostimulant such as mycorrhizas and organisms that inhibit pathogenesis and increase the natural resistance of the plant using chemical signaling to stimulate the production of protective compounds and protective tissues.

I teach a four course sequence (anatomy of trees and forests; physiology of trees and forests; seminar in alpine, arctic, and boreal ecosystems; and research methods in anatomy and physiology of trees). These courses integrate plant morphology, anatomy, seed formation, seedling germination and establishment, root structure and function, wood and bark structure and formation, mineral nutrition, symbioses including nitrogen fixation and mycorrhizae, photosynthesis, respiration, water relations, physiological ecology, biometerology, silvics, fire ecology, carbon sequestration, and research methods such as microtechnique and cytochemistry, photosynthesis measurements, spectral reflectance analysis of leaves to determine levels of stress and plant health, chlorophyll fluorescence, water potential methods. The individual species and their adaptations to the environment will be a primary focus.

Who Should Take These Courses Many of the topics covered in this course can be found in Gifford Pinchot's Primer of Forestry Part I. The Forest. 1899. For over a hundred years foresters have required this information as part of their basic knowledge. The importance of this information for intelligent forest management, urban forestry/arboriculture, and any land management is undiminished. As Aldo Leopold noted in Sand County Almanac (1949), there are two kinds of foresters: type A is quite content to grow trees like cabbages with no ecological conscience while Group B prefers natural reproduction, seeks knowledge of all aspects of the forest, and understands that a healthy forest is one that can reproduce itself. If you had a heart problem and were referred to a heart specialist who told you that he really didn't know where your heart was located, how it functioned, or its structure, your confidence in his or her ability to operate on your heart would be nil. Similarly, if you wish to solve problems about the sustainable management, silviculture, growth and health of forests it is useful to know how the trees of the forest are put together and how they function, grow, reproduce, and respond to stresses like global warming, insects, disease, and drought. In 1913 our founding Director/Dean (1900-1911, 1923-1939), Henry Solon Graves, wrote “…the School consistently maintained its high technical requirements, because it was training men to develop forestry and not merely to fill certain positions that might be available”. He also said, “…in building up the science of forestry and getting its principles in actual practice, Yale has a great opportunity and a great responsibility to serve the country. …The graduates of the School have become leaders because they have had a point of view and knowledge beyond that needed for every-day work which they first find to do.” He envisioned that the dedicated students and faculty of the School would form an “irresistible educational force” to save and sustainably manage the Nation’s forests for fuel, lumber, watersheds, wildlife, and other forest products and services. Our mission has expanded somewhat to include the air, water, climate, urban environments, and society, but the required dedication remains the same. We hope you will embark on these studies with the consistent spirit, loyalty, and devotion that have characterized your predecessors at the Yale Forest School.


B.S., Ph.D., Iowa State University

This professor is accepting doctoral students