Seasonal Greening in U.S. Forests, Fields, and Urban Areas

Using the assessment tool ForWarn, land managers can monitor the growth and development of vegetation that signals winter’s end and the awakening of a new growing season. Researchers have devised a way to more precisely characterize the beginning of seasonal greening, or “greenup,” and compare its timing with that of the 14 previous years. Such information helps land managers anticipate and plan for the impacts of disturbances such as weather events and insect pests.

Three maps detailing greenup in …

Mimosa – Albizia julibrissin

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

A mimosa infestation favors disturbed sites, where they can grow quickly and prevent native plant establishment.

Figure 1.  Mimosa flowers are very showy and fragrant. The leaves are delicate-looking and bipinnately compound.  Photo by Ted Bodner, Southern Weed Science Society. Figure 2.  Mimosa can quickly invade forest edges and old fields. The showy flowers make infestation very conspicuous.  Photo by James H. Miller, USDA Forest Service. Image credits:

Mimosa, also known as silk tree, is a small deciduous tree that is 10 to 50 feet in height, often having multiple trunks. It has delicate looking bi-pinnately compound leaves that resemble ferns (Miller 2003). The bark is smooth and light tan to greenish in color. Mimosa has very showy, …

Can urban tree waste be used as a renewable energy source?

With concerns about scarcity and environmental impacts of fossil fuels, markets and technologies are emerging to use tree waste as an energy source. Although timber harvesting residues currently account for the majority of energy production from tree waste, efforts are underway to also utilize urban tree waste. Energy production typically entails combustion of wood waste in a steam boiler that generates electricity. These power plants are often co-fired with coal, but plants dedicated solely to wood combustion are currently coming …

Bill Hubbard

William Hubbard has served as the Regional Forester for the Extension Service-Southern Region since 1993.  This is a liaison to thirteen 1862 University Land Grant University and the Southern Region of the U.S. Forest Service. His work involves using new and traditional technologies in regional educational programming and enhanced communication and coordination of information and activities across states and agencies in the areas of forestry and natural resource management. He previously held several teaching, research and Extension positions at the …

How do trees and other vegetation affect urban mesoclimates and microclimates?

Vegetation affects urban mesoclimate and microclimate by intercepting solar radiation, directing air movement, and affecting air temperature.  Microclimate, mesoclimate and macroclimate can be used to describe the climate of a given location. Macroclimate covers hundreds of square miles and parameters such as precipitation levels, temperatures and winds. Mesoclimate covers areas of tens of square miles and describes how conditions vary from the prevailing macroclimate due to the effects of water bodies, topographic features (terrain), and other landscape influences. A microclimate …

Uses of Urban Vegetation to Moderate Climate

Climatology is the study of weather and its changes over long periods of time. The climate within a given location can be described from three aspects: macroclimate, mesoclimate, and microclimate. Macroclimate, mesoclimate and microclimate can be used to describe the climate of a given location. Macroclimate in general covers large geographical areas (e.g. continent). Mesoclimate covers the climate of areas many square miles and describes variations from the macroclimate due to the effects of water bodies, topographic features …

Sarah Workman

Sarah Workman

Sarah works with Southern Regional Extension Forestry as a faculty member of the Warnell School and the College of Agricultural and Environmental Sciences at the University of Georgia. She helps provide and edit materials for various eXtension Communities of Practice, notably the Urban Forestry and Energy Conservation community, the Forest Farming community and the Extension Disaster Education Network.

Sarah is engaged in strategic development of partnerships through collaborative work with faculty peers, in grant preparation and programming, and

Time for Trees to Provide Energy Conservation Benefits?

It is possible to plant a tree that within a few years will provide energy conservation benefits. The length of time between planting and energy conservation savings is a function of the following factors:

  • Tree species (fast- or slow-growing)
  • Site (soil qualities such as fertility, moisture, compaction)
  • Desired energy conservation function (windbreak or shade)
  • Size and position of the structure for which energy conservation is desired

Some fast-growing tree species, under ideal growing conditions, may begin providing energy benefits …

Urban Forests and Pollution

Written by Melanie Lenart, University of Arizona
Urban trees play multiple roles when it comes to local air pollution. While trees in general help reduce air pollution, including absorbing the greenhouse gas carbon dioxide, some species contribute to local smog by emitting volatile organic carbons (VOCs). Planting locations of individual trees and species selection make a difference in the overall pollution balance.

Many urban trees help clear the air of pollution, although some are better at it than others (Table …

Urban Forests and Heat Waves

Written by Melanie Lenart

Recent research suggests the extra heating measured in cities operates, at least to some degree, at the scale of neighborhoods. In hot desert cities, such as Phoenix, Arizona, an urban forest can help keep neighborhood temperatures from reaching dangerous highs during hot summer days, particularly during heat waves.

The extra heating load that comes from replacing natural vegetation with the buildings, streets, and sidewalks that comprise cities has been recognized for many decades. Cities often average …