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Title: LIGHT MEASUREMENT METHODS RELATED TO FORAGE YIELD IN A GRAZED NORTHERN CONIFER SILVOPASTURE IN THE APPALACHIAN REGION OF EASTERN USA

Author
item Feldhake, Charles
item Neel, James - Jim
item Belesky, David
item Mathias, Erlend

Submitted to: Agroforestry Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/2005
Publication Date: 6/30/2005
Citation: Feldhake, C.M., Neel, J.P., Belesky, D.P., Mathias, E.L. 2005. Light measurement methods related to forage yield in a grazed northern conifer silvopasture in the Appalachian Region of eastern USA. Agroforestry Systems 65:231-239.

Interpretive Summary: Forages require adequate light for growth sufficient to supply feed for grazing animals. In silvopasture systems forages are shaded at different times and in different amounts depending on location relative to trees. Methods of characterizing this highly variable light environment are not standardized due to a poor understanding of how the changing light environment affects forage growth. We used three different methods of characterizing the light environment under and between trees and developed a relationship between light and forage growth. We found that on the average there is a linear relationship between the amount of light and the amount of forage growth. However, there was a large amount of variability. At some times, forage growth was nearly the same, with less than 40% of full sun as in full sun. However, most of the time forage growth decreased in proportion to decrease in light. Grazing animals likely had a strong influence on the changing growth pattern across the site. This work is useful because it shows the potential for forage growth under different light levels as well as what average growth can be expected over an extended area. The results of this study will benefit small Appalachian farms by providing information on the relationship between tree density and forage production so that sound economic decisions can be made depending on the production goals of individual growers. It will also help scientists with decisions on how to best characterize the light environment for silvopasture research.

Technical Abstract: The Appalachian Region is characterized by hilly topography and a humid temperate climate. In most areas agriculture is limited to pasture although the native climax vegetation is a highly species diverse forest. Developing appropriate silvopasture systems can potentially diversify and increase farm income. Information is needed on the yield response of forages to tree understories. The light environment of a conifer silvopasture was characterized by three methods, a hand-held photosynthetically active radiation (PAR) meter for quick measurements over a large area, fixed PAR meters recorded using data loggers for a large number of measurements over time, and hemispherical photography with software to calculate seasonal direct beam radiation. Plots harvested when forage reached 20-25 cm in height after which the entire area was grazed by sheep. There were limitations to all methods of quantifying radiation environment for predicting yield. There was a linear trend of decrease in yield with decrease in PAR however the data was highly variable and the correlations, while highly significant, were low. Grazed silvopastures are dynamic with shifting patterns in yield in response to the interactions between the spatially variable soil, changing seasonal environment, and spatially variable animal impacts for each grazing event.