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Northern Research Station
11 Campus Blvd., Suite 200
Newtown Square, PA 19073
(610) 557-4017
(610) 557-4132 TTY/TDD

Sustaining Forests

Agroforestry Practices for Biodiversity Conservation

Research Issue

[photo:] Alley-cropping practice to establish future chestnut orchard with haying of the clover and timothy planted between tree rows.Agroforestry in the temperate region is the intentional integration of trees and shrubs with livestock or crops into intensive land management systems. It can include practices such as alley-cropping, silvopastural, and riparian buffers. Integrating woody vegetation with grasses and forbs provides a wider range of habitats than would typically be found in most agricultural systems and can also enhance the production of clean water. Economic benefits include a more diversified flow of products and potentially a greater total return per acre, even though production of each component may be reduced. Adoption of agroforestry practices using alternative crops is one mechanism owners of small family farms can buffer themselves from fluctuations in income when environmental conditions, especially drought, lead to the reduced productivity of traditional agricultural crops. Trees and shrubs incorporated into agroforestry practices can benefit from the fertilization and no-till farming practices applied to forage crops and pasture. Incorporating grass and trees within riparian buffers can substantially reduce discharge of soil, nitrogen, and farm chemicals into adjacent streams. Because of conflicting information as to flood tolerance of trees and shrubs for both time of year and duration, questions exist as to what species to include in bottomland and riparian plantings that will flood more frequently under the current climate change scenarios. Insect sampling in forages growing between rows of trees show a higher diversity and abundance of predatory insects than in traditional haylands. Several introduced forage grasses and legumes have increased forage production with higher forage quality when grown under partial shade. There is a real need for information as to the shade tolerance of native perennial grasses and legumes which support a wider array of fauna for inclusion in various conservation practices. The same need exists for identifying methods to increase seed production of trees and shrubs, including vegetative propagation of precocious annual bearing hard mast trees, when established with native grasses and legumes.

Our Research

In cooperation with the University of Missouri Center for Agroforestry, we have conducted multiple screening trials on more than 45 different native and forage grasses and legumes under conditions where light is the dominant limiting resource.  In these trials, we evaluated plant biomass production under light conditions expected for open fields, thinned silvopastures, managed agroforestry practices, and managed full-stocked hardwood stands (these provide 100, 70, 45, and 20 percent of full sunlight, respectively).   Plants exhibiting shade tolerance are being evaluated in an established alley-cropping system to confirm the shade tolerance when in competition with the trees for soil moisture and nutrients.  Recently emphasis has been placed on evaluating native perennial grasses to screen different cultivars or accessions originating from shaded environments for inclusion as forage in silvopastures or as bioenergy crops in alley cropping practices.   The goal is to identify or develop new cultivars tolerant of partial shade to replace introduced grasses with more limited value to wildlife.  Other research is evaluating native cool-season grasses and legumes for their shade tolerance to be included with native warm-season grasses to extend the grazing season in silvopastures.  Within alley-cropping practices, hardwood seedling and sapling growth has been less impacted by native cool- and warm-season grasses than by the widely introduced tall fescue.  Our research has also shown there can be substantial variation within tree and shrub species exhibiting tolerance to partial inundation by spring floods for up to 6 weeks.  Within species variation within a stand is frequently greater than the variation found among sites at different hydrological positions.

Expected Outcomes

We expect to identify native grasses selected for forage quantity and quality to include in future breeding programs and make recommendations as to the most appropriate of the developed cultivars for inclusion in agroforestry silvopastural, riparian buffer, and alley-cropping practices.  We also expect to identify the most appropriate tree and shrub species as well as source of seed for planting stock for inclusion in these agroforestry practices on bottomland sites subjected to frequent and prolonged flooding.

Research Results

Navarrete-Tindall, N.E.; Van Sambeek, J.W. 2010.  Evaluating poverty grass (Dianthonia spicata) for golf courses in the Midwest.  USGA Turfgrass and Enviromental Research Online 9(9); 1-8. 

Coggeshall, M.V.; Van Sambeek, J.W.; Garrett, H.E.  2008.  Grafting influences on early acorn production in swamp white oak (Quercus bicolor Willd.).  In: Jacobs, D.F.; Michler, C.H. (eds.)  16th Central Hardwood Forest Conference.  NRS-GTR-P-24.  Newtown Square, PA: USDA Forest Service, Northern Research Station: 26-37.

Van Sambeek, J.W.; Navarrete-Tindall, N.E.; Hunt, K.L.  2008.  Growth and foliar nitrogen concentrations of interplanted native woody legumes and pecan.  In: Jacobs, D.; Michler, C.H., editors. 16th Central Hardwood Forest Conference.  NRS-GTR-P-24.  Radnor, PA: USDA Forest Service, Northern Research Station: 580-588.

Walsh, M.P.; Van Sambeek, J.W.; Coggeshall, M.V.  2008.  Variation in flood tolerance of container-grown seedlings of swamp white oak, bur oak, and white oak.  In: Jacobs, D.F.; Michler, C.H. (eds.)  16th Central Hardwood Forest Conference.  NRS-GTR-P-24.  Newtown Square, PA: USDA Forest Service, Northern Research Station: 446-456.

Van Sambeek, J.W.; Navarrete-Tindall, N.E.; Garrett, H.E.; Lin, C.H.; McGraw, R.L.; Wallace, D.C.  2007. Ranking the shade tolerance of forty-five candidate ground covers for agroforestry plantings.  The Temperate Agroforester 15(4): 1-9.

Garrett, H. E.; Kerley, M. S.; Ladyman, K. P.; Walter, W. D.; Godsey, L. D.; Van Sambeek, J.W.; Brauer, D.K.  2004.  Hardwood silvopasture management in North America.  Agroforestry Systems 61: 21-33.

Navarrete-Tindall, N.E.; Van Sambeek, J.W.; Kirk, S.D.; McGraw, R.L.  2003.  Adaptation of four Amorpha shrubs to four light levels.  In: Van Sambeek, J.W.; Dawson, J.O.; Ponder, F., Jr.; Loewenstein, E.F.; Fralish, J.S. (eds.)  Proceedings: 13th Central Hardwood Forest Conference.  NC-GTR-234.  St. Paul, MN: USDA Forest Service, North Central Research Station: 203-205. 

Research Participants

Principal Investigators

  • J.W. Van Sambeek, Research Physiologist, US Forest Service, Northern Research Station

Research Partners

Last Modified: 01/24/2012