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United States Department of Agriculture

Agricultural Research Service

Research Project: Management Strategies to Sustainably Intensify Northern Great Plains Agroecosystems

Location: Natural Resource Management Research

Title: Inhibition of forage seed germination by leaf litter extracts of overstory hardwoods used in silvopastoral systems

Author
item Halvorson, Jonathan
item Belesky, David
item West, Mark

Submitted to: Agroforestry Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/16/2016
Publication Date: 2/25/2016
Publication URL: http://handle.nal.usda.gov/10113/62487
Citation: Halvorson, J.J., Belesky, D.P., West, M.S. 2016. Inhibition of forage seed germination by leaf litter extracts of overstory hardwoods used in silvopastoral systems. Agroforestry Systems. doi:10.1007/s10457-016-9908-0.

Interpretive Summary: Interpretive Summary Silvopastures are intentional combinations of trees, forages and livestock designed to intensify agricultural productivity and promote ecosystem services. We studied the effects of tree litter extracts on forage seed germination to increase understanding about the potential interactions between pastures growing in a silvopasture under deciduous trees. Leaf litter extracts inhibited the germination of white clover seeds more than red clover with effects that increased with concentration and were greater for poplar > maple > oak leaves. Reduced germination was associated with increasing osmolality and electrical conductivity of leaf extracts. In addition, seeds treated with litter extracts germinated later than seeds treated with water, and more slowly. The litter extracts inhibited germination of all forages that were examined but resumed after the seeds were rinsed with water. Generally, recovery was not complete. Water-soluble compounds that inhibit forage germination may compromise forage establishment under some trees. Thus, management practices that account for the interactions between trees and forages are needed to ensure successful establishment and perseverance of mixed species swards in silvopastoral systems.

Technical Abstract: Silvopastoral management strategies seek to expand spatial and temporal boundaries of forage production and promote ecosystem integrity through a combination of tree thinning and understory pastures. We determined the effects of water extracts of leaf litter from yellow poplar, Liriodendron tulipifera, red maple, Acer rubrum, and white oak, Quercus alba on germination of seven forage species including legumes, cool season grasses, and a warm season grass to increase understanding about the potential interactions between pastures growing in a silvopasture and deciduous trees. Litter extracts inhibited the germination of white clover seeds more than red clover. Germination decreased as concentration of litter extract increased. Decreases were greater for poplar > maple > oak leaves. Germination decreased linearly with increasing osmolality and electrical conductivity of leaf extracts. Parameter estimates for a modified Gompertz growth curve model fit to data collected in this study further indicated treatment with litter extracts, especially poplar, resulted in delayed germination that proceeded more slowly. Similarly, cumulative germination of a variety of grasses was inhibited by 6% litter extracts with the effects of poplar > maple > oak. However, germination of all forages resumed after rinsing extract-treated seeds with water indicating inhibition of germination was due in part to osmotic effects of extracts. Final recovery of germination varied with forage species and extract type but in most instances, did not completely reach the level of the control further suggesting specific ion toxicities as well. Management practices that account for the interactions between trees and forages are needed to ensure successful establishment and perseverance of mixed species swards in silvopastoral systems.

Last Modified: 09/23/2017
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