Date of Award

Fall 2017

Project Type

Thesis

Program or Major

Natural Resources

Degree Name

Master of Science

First Advisor

Heidi Asbjornsen

Second Advisor

Richard Smith

Third Advisor

Adam Coble

Abstract

Growing demand for locally produced agriculture in the Northeast US could result in significant land use change from forests to open pasture and other agricultural uses. This conversion may reduce the soil hydrologic flow due to tree removal and increased soil compaction, leading to increasing surface runoff and erosion. Silvopasture—an agroforestry system that integrates trees with livestock—offers a potentially more sustainable alternative to conversion to open pasture, and has recently gained interest with local land owners and farmers in the region. The retention of trees within pastures may help maintain critical hydrologic functions of forest soils by promoting higher infiltration rates and hydraulic conductivity, and thereby avoiding degradation of forest hydrologic functions. We assessed the impacts of forest-to-pasture vs. forest-to-silvopasture conversion on soil hydraulic properties at two study sites, an unreplicated treatment site at the UNH Organic Dairy Research Farm (ODRF) in Lee, NH and a replicated treatment site at the North Branch Farm (NBF) in Saranac, NY. Specifically, we measured unsaturated hydraulic conductivity (K(h)) at the soil surface and saturated hydraulic conductivity (K(sat)) at 15 cm and 30 cm depths under three land uses: intact forest, open pasture, and silvopasture. Differences between land uses were observed in K(sat) results at both sites. At the ODRF, the K(sat) at 15cm depth was highest in intact forest, intermediate in silvopasture, and lowest in open pasture. However, at the 30 cm depth there were no distinct differences. The NBF site exhibited a different pattern, where the 15 cm K(sat) in silvopasture and open pasture were similar and both lower than the intact forest, but at the 30 cm depth, silvopasture K(sat) was higher than open pasture and comparable to the slightly higher intact forest. The reduced soil hydraulic conductivity under open pasture may have consequences for increasing surface runoff and soil erosion in response to high intensity rainfall. Soil hydraulic properties in silvopasture, although variable, have some potential to function as an intermediate between higher levels in the intact forest and lower levels in the open pasture which would partially maintain ecosystem and hydrologic services.

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