Prepared by Emily Haynes
(1998 class)

Temperate Region Agroforestry

CONTENTS:

• Overview
• Agroforestry Practices/Important Terms
• The Benefits of Agroforestry
• The Costs of Agroforestry
• Useful Literature
• Useful Links
• Cited Literature and Links

Back to Agroecosystems Home Page

Overview

Agroforestry is an alternative land use system which combines trees and/or shrubs with agriculture, forestry, horticulture, and/or animal husbandry practices (Jordan, 1995). There are a variety of important ecological and economic interactions between the trees and other components of the agroecosystem (Booth, 1994).

A variety of agroforestry practices are of importance in temperate regions. They are riparian buffer strips, windbreaks, alley cropping, silvapastoral management, forest farming (Garrett and Buck, 1997), a nd tree plantations. Each of the practices serves a specific purpose while providing a variety of other services.

Integrating trees into agricultural systems can be very beneficial. Agroforestry practices are heterogeneous systems which are more ecologically sustainable and economically sustainable than annual monocultures. Agroforestry production is distributed more evenly over a longer period of time, which provides a more stable income to those who practice it (Jordan, 1995). The integration of trees into agricultural systems increases crop production, provides a greater variety of products, often improves the quality of the soil, decreases soil erosion, and decreases air and water pollution. Agroforestry also increases both species and landscape diversity.

Though there are many benefits to agroforestry it also has it's costs. Such things as competition for sunlight, water, and nutrients between trees and crops (Schroth et al., 1995), reduction in area that can be cultivated in crops, and a loss of nutrients when trees are harvested (Jordan, 1995) are all adverse effects of agroforestry. Other possible disadvantages include high labor costs, transition costs to establish, and long-term investment (Jordan, 1995).

Despite the costs there is an urgent need for the world to make the transition from unsustainable land use practices, such as large scale monoculture of crops, to sustainable ones, such as agroforestry. Unsustainable practices are degrading the natural environment upon which all living things depend for food and shelter.

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Agroforestry Practices/Important Terms

• Riparian Buffer Strips
• Windbreaks
• Alley Cropping
• Silvapastoral Management
• Forest Farming
• Tree Plantations

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Riparian Buffer Strips

Riparian buffer strips are zones of trees or shrubs that are allowed to persist or are planted de nova on or near banks of rivers and streams. Riparian trees are water-loving trees that soak up excess water and nutrients. They reduce flooding and erosion, trap nutrients, store water, and provide a habitat for wildlife (*THE TEMPERATE AGROFORESTRY HOMEPAGE). One or two rows of trees and shrubs can provide substantial protection; commonly a 10-50 m zone is recommended. A riparian buffer strip can remove up to 80% of nitrogen and phosphorus from surface water (*THE TEMPERATE AGROFORESTRY HOMEPAGE), thus riparian forests can play an important role in reducing pollution of our waterways.

Agroforestry Practices/Important Terms

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Windbreaks

Field windbreaks are one or more rows of trees that are planted adjacent to a cultivated field and are oriented perpendicular to the hot drying summer wind and to the harsh winter wind (*THE TEMPERATE AGROFORESTRY HOMEPAGE). Since the direction of the summer and winter wind may be different more than one side a field may need a windbreak. It's best to plant tall, fast growing trees. Shrubs planted between the rows provides even more protection. The main purpose of field windbreaks is to provide crops with protection from drying and erosive effects of wind. Fine soil, which contains mostly humus and is nutrient rich, is moved readily by wind (*WINDBREAKS IN SUSTAINABLE AGRICULTURE). Windbreaks can provide benefits to a distance of 10-20 times the height of the trees within a windbreak (Garrett and Buck, 1997). Thus an 8 meter high windbreak could provide protection for a distance of 80-160m.

Field windbreaks also trap and distribute snow over fields in the winter which increases overall soil moisture (*WINDBREAKS IN SUSTAINABLE AGRICULTURE). They also intercept sunlight thereby further decreasing the risk of moisture deficit (Girouard, 1992). By reducing loss of nutrients and increasing moisture, field windbreaks can increase crop yields.

Livestock windbreaks are trees that are planted to shelter livestock from cold wind, and blowing soil and snow. Protecting livestock from harsh elements reduces the stress on the animals. This in turn increases their health, reduces mortality, decreases feed requirements, and provides an overall increase in profit (WINDBREAKS IN SUSTAINABLE AGRICULTURE).

Windbreak trees can also bring a profit to farmers if fruit or nut-bearing trees are planted. And, when thinning windbreaks, the trees can be harvested for timber, fuelwood, or Christmas trees.

Agroforestry Practices/Important Terms

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Alley Cropping

Alley cropping refers to widely spaced rows of trees or shrubs that create alleyways in which crops are grown (Garrett & Buck, 1997). It reduces soil erosion due to wind and water, improves crop production, creates wildlife habitat, and provides corridors for wildlife to pass through (*THE TEMPERATE AGROFORESTRY HOMEPAGE). To reduce the risk of diseases and pests, it's best to plant more than one tree species in alley cropping systems.

Agroforestry Practices/Important Terms

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Silvapastoral Management

This is a tree-animal system in which forages are grown with trees under intensive management for livestock grazing (Garrett & Buck, 1997). It is becoming increasingly popular and is already the most common agrforestry practice in the state of Washington, USA.

Agroforestry Practices/Important Terms

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Forest Farming

Forest Farming is an agroforestry practice which involves growing shade tolerant specialty crops, in natural forest stands, which are sold for ornamental, culinary or medicinal purposes (Garrett and Buck, 1997). Examples of specialty crops in temperate regions, particularly in North America, include wild mushrooms, sugar maple, and ginseng.

Agroforestry Practices/Important Terms

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Tree Plantations

Tree Plantations are usually odd shaped plots of land where trees are planted for future harvest. There are a variety of types. In timber plantations, trees are harvested for building or for pulp and paper. They can take as long as 60 years and as short as 25 years to be ready for harvesting (*THE TEMPERATE AGROFORESTRY HOMEPAGE).

Fuelwood plantations, where trees are grown for fuel, can be harvested in as few as 5 years (*THE TEMPERATE AGROFORESTRY HOMEPAGE). Therefore, fuelwood can be harvested when thinning a timber plantation.

Agroforestry Practices/Important Terms

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The Benefits of Agroforestry

• Improves Soil Quality

  Degraded soil occupies a significant area of temperate biomes. Agroforestry improves soil quality by protecting it from erosion due to wind and water, and by adding a lot of organic matter. Wind carries away a lot of nutrient rich soil, but windbreaks can greatly decrease this effect.

• Increases Crop Production

  By improving the quality of the soil and protecting crops from the damaging effects of the wind, agroforestry can increase crop production.

• Provides a Greater Variety of Products

  Agroforestry by definition is the integration of trees or shrubs with agriculture, horticulture, and animal husbandry practices (Jordan, 1995). Combining trees or shrubs with one or more of these other land use systems provides a greater variety of products. For example, an agroforestry system could produce fruits, vegetables, beef, dairy products, cash crops and timber.

• Provides Stable Income

  Since agroforestry increases the variety of products over forestry or farming alone. it can provide a more stable income. Agroforestry production is also more evenly distributed over time (Jordan, 1995). For example, in the summer the fruit and vegetables will be ready for harvest and income from this will continue into the fall. Then, in the winter, if the famer is in need of more income some trees could be harvested for timber or Christmas trees. The trees will also continue to provide profit in the future as they are replanted and harvested again and again.

• Decreases Air and Water Pollution

  After fossil fuel burning, the clearing of forests for agriculture is second in importance as a net source of atmospheric carbon dioxide, one of the most significant greenhouse gases (Booth, 1994). The forests of the world sequester and conserve more carbon than all other terrestrial ecosystems and account for 90% of the annual carbon flux between the Earth's surface and the atmosphere (Winjum et. al., 1993). The implementation of agroforestry practices replenishes many of the lost trees, thus contributing to the lowering of atmospheric carbon dioxide.

  Riparian buffer strips, as discussed in Agroforestry Practices/Important Terms, take up 80% of nitrogen and phosphorous from surface water runoff (*THE TEMPERATE AGROFORESTRY HOMEPAGE). This reduces the amount nitrogen and phosphorous entering our waterways, thus helping reduce eutrophication.

• Decreases Soil Erosion

  Establishment of trees in windbreaks reduces soil erosion due to wind, while creation of treed riparian buffer strips reduces soil erosion due to runoff and flooding.

• Increases Species and Landscape Diversity

  Incorporating trees into agricultural systems increases species diversity on its own and by providing habitat for wildlife.

  Agroforestry increases landscape diversity when it incorporates both terrestrial and aquatic environments (Jordan, 1995), e.g. when riparian buffer strips are established.

• Is an Ecologically Sustainable Practice

  Agroforestry contributes to ecological sustainability by conserving soil and nutrients, providing an on-farm fuel source and by increasing species and landscape diversity.

• Is an Economically Sustainable Practice

  Agroforestry contributes to economic sustainability by providing year round distribution of income, employment, and products.

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The Costs of Agroforestry

• Competition

  In agroforestry systems there may be root competition between trees and crops for water and nutrients, as well as shoot competition for light (Strophe et al., 1995). Root competition seems to pose the most severe problem, especially with fast growing trees. Root competition may be alleviated by digging trenches between the trees and the crops, or by using intensive soil tillage to destroy tree roots in the topsoil before planting the crops (Schroth et al., 1995).

• Reduction in Crop Area

  By planting trees, the area of land available for crops is reduced. Therefore, there may be a loss of immediate income which one gets from crops.

• Loss of nutrients when trees are harvested.

  When trees are harvested from a system nutrients are lost in the product and by leaching (Jordan, 1995). However, if trees are replanted, losses can be reduced.

• High Labor Costs

  Planting and harvesting trees requires a lot of labor. In areas where labor costs are high agroforestry can be expensive. In some cases, the use of machinery can alleviate this problem.

• Transition Costs

  Changing a current agricultural practice to one that integrates trees can be very costly (Jordan, 1995). It involves giving up current cropland for the planting of trees. Therefore, money is lost initially due to the reduction of food products and is also lost in the purchase of trees.

• Long-term Investment

  The economical benefits of agroforestry are not immediately apparent. It may be 20 years before trees can be harvested. Therefore, one has to be prepared to wait before seeing financial profit from implementing agroforestry practices. If fruit or nut-bearing trees are planted, products will be seen much sooner.

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Useful literature

• Dixon, R.K., et. al. 1994. Integrated land-use systems: assessment of promising Agroforestry and alternative land-use practices to enhance carbon conservation and sequestration. Climatic Change 27: 71-92.

• Douglas, J.S. and de J Hart, R.A. 1993. Forest farming. Intermediate Technology Publications, London, pp. 136-149. Dal. Lib. SB 170 S56 1993 SCI.

• Garrett, H.E.G.. and Buck, L. 1997. Agroforestry practice and policy in the United States of America. Forest Ecology and Management 91: 5-15. Dal. Lib. QH 541.5 F6 F6.

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Useful links

• THE ASSOCIATION FOR TEMPERATE AGROFORESTRY
  (http://www.missouri.edu/~afta/) Association for Temperate Agrooforestry, Spons. (Viewed 6 Feb. 2001)
  This site provides thorough information on agroforestry.

• NATIONAL AGROFORESTRY CENTER
  (http://www.unl.edu/nac/index.html) U.S. Department of Agriculture National Agroforestry Centre, Spons. (2001, January 26; Viewed 6 Feb. 2001)
  This center is actively working on the development and technology of agroforestry. This is an excellent page with lots of reliable information.

• UK AGROFORESTRY RESEARCH FORUM
  (http://www.sylvan.demon.co.uk/forum2.html) U.K. Agroforestry Forum, Spons. (2001, January 29; Viewed 6 Feb. 2001)
  This forum discusses temperate agroforestry in the UK and provides a more in depth look at sylvapastoral systems.

• WINDBREAKS IN SUSTAINABLE AGRICULTURE
  (http://www.ianr.unl.edu/pubs/Forestry/ec1772.html) Vernon Quam and John Gardner, North Dakota State University
  James R Brandle and Teresa K. Boes, University of Nebraska, Auth. (Viewed 6 Feb. 2001)
  This page looks at the use of trees as windbreaks. It provides a lot of useful information on agroforestry.

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Cited Literature and Links

• Booth, T.H. 1994. Determining the climatic requirements of trees suitable for agroforestry. Climatic Change 27: 93-102. Dal. Lib. QC 980 C5.
• Garrett, H.E.G. and Buck, L. 1997. Agroforestry practice and policy in the United States of America. Forest Ecology and Management 91: 5-15. Dal. Lib. QH 541.5 F6
• Jordan, Carl F. 1995. Conservation. John Wiley & Sons Inc., New York, pp. 166-168, 175, 177, 196-201, and 214-222.
• Schroth, G., et. al. 1995. Effects of different methods of soil tillage and biomass application on crop yields and soil properties in agroforestry with high tree competition. Agriculture, Ecosystems and Environment 52: 129-140.
• WINDBREAKS IN SUSTAINABLE AGRICULTURE
  (http://www.ianr.unl.edu/pubs/Forestry/ec1772.html) Vernon Quam and John Gardner, North Dakota State University
  James R Brandle and Teresa K. Boes, University of Nebraska, Auth. (Viewed 6 Feb. 2001)
• Winjum, J.K., et al. 1993. Forest management and carbon storage: a look at 12 key forest nations. Water, Air and Soil Pollution. 70: 1-4: 239-257.

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