Forest Disease Biology and Ecology
(Project 4505) 
Declining Sugar Maple Stand
(Decline could be due to drought,
defoliation, nutrient deficient soils,
or combination of these stresses and Armillaria Root disease.)
Mission: To determine how interactions of stressors, pathogens, and hosts disturb forests and how such disturbances change forest and ecosystem structure, function and sustainability.
Nowhere are the complicated dynamics of forest health and forest ecological processes more evident than in the research underway on the disturbance to forests caused by stress agents and their interactions with pathogens. Diseases can occur when trees weakened by such environmental stresses as insect defoliation, extremes of temperature and moisture, air pollutants, and attacks by sucking insects are unable to defend themselves and are invaded and often killed or rendered defective by opportunistic organisms. Researchers in this group, located at Hamden, Connecticut and Durham, New Hampshire, have expertise in plant pathology, plant ecology, plant physiology, biochemistry, and soil science. They investigate the causes, patterns of development, and characteristics of these stress-triggered tree diseases, the ecology of the organisms involved in tree damage and mortality, and the influence of these disturbances on ecosystem attributes, processes, and their relationship to forest health. Over the years, their research focus has included ash dieback (drought triggered), beech bark disease (initiated by a scale insect), decline and mortality of oak and sugar maple decline (initiated by insect and frost defoliation and drought), sapstreak disease of sugar maple (physical disturbance related), and red spruce decline (hypothesized to be related to atmospheric deposition and other environmental stresses). Researchers have identified the organisms involved in decline diseases, elucidated the effects of stress on host tree physiology and chemistry, and determined the host-organism interactions resulting in decline. Related work has focused on how trees defend themselves and wall off invading organisms, how to measure tree vitality both physically and biochemically, and how to measure stress in mature trees.
This research team seeks to understand how the spatial distribution of stress-triggered diseases is related to plant species associations and how gaps created by these diseases spread within the forest. A major research focus will determine the mechanisms by which atmospheric deposition affects tree and forest health. Understanding these relationships will enable scientists to determine what forests or portions of forests are susceptible and vulnerable to disease, and develop methods and procedures to measure, predict, and mitigate disease before or when it occurs. Research will determine why some trees under stress are susceptible to opportunist pathogens and vulnerable to their effects, while other similarly stressed trees are not, and if these resistant traits can be perpetuated both spatially and temporally in the current and developing forest. They seek to understand the role of opportunistic pathogens that operate as ecosystem "roguers," ridding ecosystems of under-productive trees and allowing new, vigorous trees to replace them and to determine if these organisms can be used as indicators and predictors of changes in forest health. Other studies will determine the distribution and role of opportunistic fungi in the forest and landscape and evaluate how competitive fungi affect their ecology and distribution. The role of decay fungi in woody debris decomposition on the forest floor and nutrient conservation and cycling in forest stands will also be investigated.
In cooperation with other Forest Service and university scientists, the unit seeks to identify the stressors and opportunistic organisms that will cause disturbance to the forests, to measure and characterize forest habitats where these interactions will cause problems, and to develop ecologically sound guidelines for managing the diseases they cause. Another major focus of this cooperative research is the clarification of the effects of environmental stresses and stand management practices on the vitality of fine roots and the relationship of root vitality to the health of trees, stands, and forests.
The group's research encompasses both field studies to observe and identify the ecological relationships of stress, tree, and interacting organisms, and laboratory studies under controlled conditions to clarify the genetic, physiological, pathological, and biochemical bases for the observed relationships. Molecular genetics and other biotechnological methods and techniques are among the laboratory research methods used.
Major goals of the group's research, closely tied to ecosystem management, are to develop an understanding of the interplay between ecological processes and the onset and development of stress-induced diseases, clarify the relationship of disturbance caused by these diseases to forest health and ecosystem integrity and sustainability of the production of a variety of goods, services, and amenities from these forested ecosystems, and create guidelines for managing these diseases. Research results have been published in several peer-reviewed journals.