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.

Concise, informative • Subscribers in over 180 countries 
Easy to subscribe/unsubscribe

Overstory #93 - Trees, Forests and Sacred Groves

Forests and sacred groves

Every culture has narratives or beliefs which answer in different ways the fundamental questions about how we came to be, and articulate how and where people originated, collective transformations undergone by the community, and how people should behave towards one another and their environment (Elder and Wong 1994). Forests are the subject of a great deal of myth, legend and lore. Societies most closely entwined with forests tend to regard them with a healthy respect, an awe at their splendour and majesty, sometimes dread and fear of the powerful spirits that lurk within them. Ancestors often find their resting places in forests, many wandering in various states of unease and spitefulness.

In European culture, the word 'savage' was derived from silva meaning a wood, and the progress of mankind was considered to be from the forest to the field. Schama (1995) describes how from Ireland to Bohemia, penitents fled from the temptations of the world into forests, where in 'solitude they would deliver themselves to mystic transports or prevail over the ordeals that might come their way from the demonic powers lurking in the darkness'. The 'indeterminate, boundless forest', then, was a place where the faith of the true believer was put to a severe test. The forests in European culture were also considered to be a more positive site of miracles, the source of great spiritual awakenings; and the forest itself was held to be a form of primitive church or temple. The first temples in Europe were forest groves, and although progressively replaced with temples made of wood, and subsequently by churches made of stone, places of worship – particularly those of Gothic architecture – continue to evoke the forest with their design and proportions (Rival in Posey 1999; Schama 1995; Burch in Posey 1999).

Continue Reading

Overstory #92 - Trees and Their Energy Transactions


This article deals with the complex interactions between trees and the incoming energies of radiation, precipitation, and the winds or gaseous envelope of earth. The energy transactions between trees and their physical environment defy precise measurement as they vary from hour to hour, and according to the composition and age of forests, but we can study the broad effects.

The planting of trees can assuredly increase local precipitation, and can help reverse the effects of dryland soil salting. There is evidence everywhere, in literature and in the field, that the great body of the forest is in very active energy transaction with the whole environment. To even begin to understand, we must deal with themes within themes, and try to follow a single rainstorm or airstream through its interaction with the forest.

A young forest or tree doesn't behave like the same entity in age; it may be more or less frost-hardy, wind-fast, salt-tolerant, drought-resistant or shade tolerant at different ages and seasons. But let us at least try to see just how the forest works, by taking one theme at a time. While this segmented approach leads to further understanding, we must keep in mind that everything is connected, and any one factor affects all other parts of the system. I can never see the forest as an assembly of plant and animal species, but rather as a single body with differing cells, organs, and functions. Can the orchid exist without the tree that supports it, or the wasp that fertilises it? Can the forest extend its borders and occupy grasslands without the pigeon that carries its berries away to germinate elsewhere?

Continue Reading

Overstory #91 - Fodder Tree Establishment

Livestock play an important role in small-scale farming systems throughout the world.

Most often livestock graze fallow fields, pastures and woodlands deriving most of their sustenance from crop residue, grasses and other herbaceous plants. A smaller but important component of livestock diets comes from tree fodder. Farmers harvest tree fodder from natural forests, savanna and woodlots. Additionally, they often deliberately propagate trees on their farms to expand fodder resources. Many of the most important fodder trees are nitrogen fixing species. This article covers the propagation, establishment, and maintenance of this important group of nitrogen fixing trees used for fodder.

Continue Reading

Overstory #90 - Biodiversity and Protected Areas

This edition covers protection of ecosystems for the purpose of maintaining biological diversity. Protected areas on both small and large scales can conserve biodiversity, as well as protect other essential ecosystem functions such as watershed, carbon storage, and erosion control. Although this edition does not directly cover farm systems, many farms have wild areas such as gulches, forests, and areas that have long been unused and are returning to forests. Protected areas are important on both large and small scales.

Establishment of protected areas

The world's first two national parks were established in the 1870s. Growth the number and size of protected areas was slow at first. It accelerated during the 1920s and 1930s, halted during World War II, and regained momentum by the early 1950s. The number doubled during the 1970s. Before 1970, most protected areas were located in industrial countries. In more recent years, the Developing World has led in both numbers added and rates of establishment.

Acquisition and designation

Most protected areas are established by official acts designating that uses of particular sites will be restricted to those compatible with natural ecological conditions. At the Federal level in the United States, designating a land area or water body for conservation involves making a formal declaration of intent to assign a certain category of protection and then providing an opportunity for extensive public comment on the proposed action. Other governments use similar processes, although the extent of public participation varies.

Continue Reading

Overstory #89 - Invasive Woody Plants

Invasive Woody Plants

Biological invasions are considered to be one of the major threats to the earth's biodiversity. Non-native woody species, introduced by humans, can spread into native forests, pastures, or cultivated areas. Such species are termed, "invasive." Many animals and plants are highly invasive and some species dramatically affect the structure and function of ecosystems.


Nearly all introductions of woody plants which have become invasive, have been introduced intentionally by horticulturalists, botanists, foresters or gardeners. The bibliographical data showed that as early as last century a number of authors realised the regeneration potential and sometimes the invasive potential of introduced woody plants. Since these problems have been known for quite some time, it is important to investigate how aware practitioners of introductions were of the potential problems associated with species introductions.

Continue Reading

Overstory #88 - Revegetation Planning for Farm Forestry

Revegetation Planning for Farm Forestry

Revegetation is defined here as, "the planting of trees and shrubs, the encouragement of natural regeneration and the use of deep rooted and/or perennial crops and pastures" (Oates 1987).


Whole farm planning provides a framework within which revegetation can be integrated with farming. Whole farm planning considers the natural resource base, the physical improvements of the farm, land management practices, and the financial basis of the farm.

Landholders interested in revegetation tend to be planners by nature and are often recognised in a district as "good farmers." This reinforces the thesis that planning is fundamental to sustainable land use. The next step for these farmers is to become more conscious of the planning process to develop more integrated farm plans.

Continue Reading