PRODUCTION AND BOTANICAL COMPOSITION OF A GRASS-LEGUME SWARD AS A FUNCTION OF CONIFER TREE CANOPY DENSITY

摘要

Small-scale farms in the Appalachian Region are a mosaic of traditional pasture and wooded sites. Topography along with temperature and moisture extremes influences the quantity and seasonal distribution of herbage in pasture. Tree canopies modify themicroclimate and could buffer periods of weather extremes and influence the distribution and nutritive value of forage grown as an understory crop. A grass-legume mixture was grown in a light gradient created by a 35-yr old, mixed-species conifer stand.Herbage production, seasonal distribution and botanical composition of the sward were quantified as a function of light intensity. The site was limed and treated with phosphorus fertilizer. Mature wether sheep were used to control existing understory vegetation and to tread in surface broadcast seed. Accumulated herbage was grazed at three-week intervals. Herbage yield was greatest at 80% of full light at 2 tons/acre, while cumulative yields at 50 and 20% light reached 1.5 tons/acre. The presence of white clover and perennial ryegrass was greatest at 80% full light and increased over the growing season, while the proportion of bare ground, orchardgrass and other grasses declined.