A free email agroforestry journal for practitioners, extension agents, researchers, professionals, students, and enthusiasts. One edition is sent each month focusing on a concept related to designing, developing, and learning more about trees and agroforestry systems. Focuses on trees and their roles in agriculture, natural ecosystems, human culture and economy.

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Overstory #87 - Urban Forestry

Urban Forestry

Although trees have been an important part of human settlements throughout history, only recently has their full value to urban dwellers been recognized. Trees and green spaces play an important role in improving city living conditions. In the past, urban forestry in developed countries was considered almost exclusively on the basis of its aesthetic merits. Now, a closer look is being given to the environmental services and quantifiable economic benefits they provide. This article discusses the role of trees in and around densely populated areas.


Urban forestry has as its objective the cultivation and management of trees for their present and potential contribution to the environmental, social, and economic well-being of urban society. Urban forestry is a merging of arboriculture, ornamental horticulture and forest management. It is closely related to landscape architecture and park management. In its broadest sense, urban forestry embraces a multifaceted managerial system that includes municipal watersheds, wildlife habitats, outdoor recreation opportunities, landscape design, recycling of municipal wastes, tree care and the production of wood as a raw material.

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Overstory #86 - The Role of Mushrooms in Nature

Fungi have vital roles in ecosystem health. There are numerous fungi that produce fleshy fruiting bodies known as mushrooms, many of which are prized for their edible and medicinal uses. In this edition of The Overstory, special guest author Paul Stamets explores the role of mushroom-producing fungi (commonly referred to as mushrooms) in the health of forests and other landscapes.

The article covers three basic ecological groups of mushrooms: those that form a symbiosis with host plants called mycorrhizal mushrooms; those that act on living plants called parasitic mushrooms; and those that recycle dead plant material, the saprophytic mushrooms.

The Mycorrhizal Gourmet Mushrooms

Mycorrhizal mushrooms form a mutually dependent, beneficial relationship with the roots of host plants, ranging from trees to grasses. "Myco" means mushrooms, while "rhizal" means roots. The collection of filament of cells that grow into the mushroom body is called the mycelium. The mycelia of these mycorrhizal mushrooms can form an exterior sheath covering the roots of plants and are called ectomycorrhizal. When they invade the interior root cells of host plants they are called endomycorrhizal. In either case, both organisms benefit from this association. Plant growth is accelerated. The resident mushroom mycelium increases the plant's absorption of nutrients, nitrogenous compounds, and essential elements (phosphorus, copper, and zinc). By growing beyond the immediate root zone, the mycelium channels and concentrates nutrients from afar. Plants with mycorrhizal fungal partners can also resist diseases far better than those without.

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Overstory #85 - Animal Shelter

Animal Shelter

Windbreaks are groups of trees or shrubs in any arrangement that will afford protection from wind to crops and/or animals. Previous editions of The Overstory (#32 and #73) showed how windbreaks can be used to protect crops from the damaging effects of wind. In this edition, special guest author Steven Burke shows how windbreaks also are very valuable for protecting animals from the elements.

Extremes in climatic conditions can have enormous effects on the productivity of farm animals. Numerous studies indicate that the provision of shelter improves livestock performance through moderation of some of these effects.

Windbreaks can improve pasture production, which in turn provides benefits to livestock. More available feed means that animals will be heavier and healthier, or that higher stocking rates can be maintained. In addition to providing more feed, windbreaks can offer other important benefits to animals including increasing weight gain and health, and moderating the harmful and potentially lethal effects of wind, rain, sun, and cold.

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Overstory #84 - Patchiness: Living in the Real World

Patchiness: Living in the Real World

Agroforestry systems are characteristically diverse, containing a mosaic plants and animals within a broad range of natural land features, climates, and soils. Editions #72 and #74 of The Overstory by Robert Chambers explored how observing and exploiting microclimates (small-scale environments) can be extremely useful in developing sustainable land use systems.

In this edition, special guest author Peter Huxley discusses how spatial differences, or patches, are an important aspect of understanding and designing agroforestry systems.

What Is 'Patchiness'?

We all live in a very 'patchy' environment, some more than others, and tropical agroforesters more than most! Patchiness is a form of variability in space. The term expresses diversity, a difference in the nature of something in degree or quality. Spatial differences can be gradual (a 'cline'), or they can be more abrupt as in patchiness, where some area is distinguishable in some way from those around it. Patchiness often refers to the unlike nature of many adjacent small areas. Sometimes patchiness is used in a wider context to refer to any kind of dimensional variability, for example, changes throughout a three-dimensional soil profile. Change can occur over time, too, so that any particular pattern of patchiness can evolve into another.

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Overstory #83 - Niche Markets

Niche Markets

Growing fruits, vegetables, and other farm products—particularly specialty items preferred by ethnic populations, unusual minor crops grown on a limited scale, or certified organic produce—offers profitable niche markets for small farmers.

Many unique crops do not easily adapt to large-scale production—so corporate farm enterprises, which control so much of the world's food business, do not produce them. Small farmers can capitalize on growing this specialty produce.

Today's customers want high-quality, interesting, attractive, tasty, nutritious, and convenient foods. Many want to know who grows their food and under what cultivation practices.

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Overstory #82 - Introduction to Indigenous Knowledge

What is Indigenous Knowledge?

Indigenous knowledge (IK) is, broadly speaking, the knowledge used by local people to make a living in a particular environment (Warren, 1991). Terms used in the field of sustainable development to designate this concept include indigenous technical knowledge, traditional environmental knowledge, rural knowledge, local knowledge and farmer's or pastoralist's knowledge. Indigenous knowledge can be defined as "A body of knowledge built up by a group of people through generations of living in close contact with nature" (Johnson, 1992). Generally speaking, such knowledge evolves in the local environment, so that it is specifically adapted to the requirements of local people and conditions. It is also creative and experimental, constantly incorporating outside influences and inside innovations to meet new conditions. It is usually a mistake to think of indigenous knowledge as 'old-fashioned,' 'backwards,' 'static' or 'unchanging.'

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