Beech Bark Disease

Written by D. Kennard, D.J. Moorehead, C. Evans, and G.K. Douce for Forest Encyclopedia Network
Figure 1. Cankered stem of a beech tree following an attack by beech scale and infection by Nectria coccinea (beech bark disease complex) in Ontario. Photo by Linda Haugen, courtesy of

Beech bark disease (Fig. 1) is caused by a complex of two agents, the beech scale insect, Cryptococcus fagisuga (Fig. 2), and a fungus, Nectria coccinea faginata. Infestation is easily identified by …

Emerald Ash Borer

Written by: G.K. Douce, C. Evans, and D.J. Moorhead for Forest Encyclopedia Network
Figure 1. A map showing the spread of emerald ash borer within the northeastern United States and southeastern Canada.

Emerald ash borer, Agrilus planipennis, is a newly introduced species (found in 2002) from Asia. Populations have been found in Michigan, Ohio, Illinois, Indiana, Iowa, Maryland, Minnesota, Missouri, New York, Pennsylvania, Virginia, Wisconsin, Ontario, and Quebec (USDA 2011). Larvae feed on phloem and sapwood of ash …

Asian Longhorned Beetle

Written by D.J. Moorhead and G.K. Douce for Forest Encyclopedia Network

Asian longhorned beetle, Anoplophora glabripennis, is a recently introduced pest from China. It is believed to have entered the United States inside solid wood packing material from China (USDA – Forest Service 2002). It was first discovered in the United States in 1996 in New York. In 1998, an infestation was found in Chicago. In 2002, Asian longhorned beetle was found in New Jersey and has since spread …

Basic Soil Components

Written by Tom DeGomez, University of Arizona, Peter Kolb, Montana State University, and Sabrina Kleinman, University of Arizona

A soil is simply a porous medium consisting of minerals, water, gases, organic matter, and microorganisms. The traditional definition is: Soil is a dynamic natural body having properties derived from the combined effects of climate and biotic activities, as modified by topography, acting on parent materials over time.

There are five basic components of soil that, when present in …

Tree Growth

Written by Peter Kolb, University of Montana

Tree growth is determined by a tree species’ ability to obtain sunlight, water, nutrients, and air in a specific climate. Each tree species has evolved over time to have a particular growth and reproductive advantage for a specific range of variability of climatic and soil conditions. Tropical trees, for example, do not expend energy for becoming cold hardy and thus outcompete any tree that puts aside energy for that purpose. Alternatively, a tropical …

Understanding Soils in Forests

Written by Sabrina Kleinman

Soil is an important component of forest and woodland ecosystems as it helps regulate important ecosystem processes, such as nutrient uptake, decomposition, and water availability. Soil also represents one of the largest carbon pools on the planet whose alteration can impact carbon storage and carbon emissions. Soil carbon helps soils retain water, increases soil’s capacity for holding on to important nutrients such as nitrogen and phosphorous, and serves as a source of energy for belowground organisms …

Biodiversity in Forests

Written by Amy Grotta

Biodiversity refers to the range of life forms and species that exist within a given ecosystem. Different forest types have varying degrees of biodiversity. Tropical rain forests are some of the most biologically diverse ecosystems on the planet. However, even temperate forests consisting of only a few overstory tree species may contain surprising levels of biodiversity when all other life forms found within them are considered (e.g., herbaceous plants, mammals, birds, invertebrates, fungi, etc.).

Species exist …

What Makes a Tree Unique?

Written by Peter Kolb, University of Montana

A tree is a plant with a tall structure comprised of a stem and branches to support leaves and a root system than anchors the stem as well as procures and stores essential growth elements, such as water and nutrients. Trees are unique from other plants because they can and usually do live for decades and even up to several millennia (the oldest known single-stem tree is a baobab in South Africa measured …

History of Southern Pine Beetle

Written by J.D. Ward and P. Mistretta for Forest Encyclopedia Network

The southern pine beetle (Dendroctonus frontalis Zimmermann) is a serious pest of pines in the southern United States, Mexico, and Central America. The southern pine beetle (SPB) kills pines by boring under the bark and destroying the cambium layer of the tree. Trees are often mass attacked by thousands of individual southern pine beetles. Because populations can build rapidly to outbreak levels, large numbers of trees can be …

Southern Pine Beetle

Written by G. K. Douce, C. Evans, and D. J. Moorhead for Forest Encyclopedia Network
Figure 1. Adult southern pine beetles. Photo by David T. Almquist, courtesy of

The adult southern pine beetle (SPB) is 2 to 4 millimeters in length, has a rounded abdomen, and is brownish-black in color (Figure 1). Males have a frontal groove on top of the head, while the females possess a broad elevated ridge called a mycangium on the anterior pronotum. Both males …