2.1 Study site
The watershed in this study, designated as Hill Forest Two (HF2), is characterized as a 38-year-old mixed pine-hardwood stand located within the Piedmont region of North Carolina (NC) (Figure 1). The catchment drains the first-order streams in the large Flat River watershed at North Carolina State University’s Hill Demonstration Forest in northern Durham County, NC. HF2 is 12 hectares in size, and dominated by loblolly pine (Pinus taeda), white oak (Quercus alba ), tulip poplar (Liriodendron tulipifera) , sweetgum (Liquidambar styraciflua), chestnut oak (Quercus prinus ), Virginia pine (Pinus virginiana ), northern red oak (Quercus rubra ), red maple (Acer rubrum) , American beech (Fagus grandifolia ), pignut hickory (Carya glabra) , and mockernut hickory (Carya tomentosa ). Upland soils are defined as well-drained with a depth to the water table higher than two meters (m). They tend to function in a similar drainage capacity in the growing season (i.e., May-October) and non-growing season (i.e., November-April). The NC Geological Survey (1988) reported that the soil substrate (Carolina Slate Belt, CSB) is comprised mostly of rocks formed through volcanic activity and deposits. The total land surface in CSB covers 9 % of NC and extends into the surrounding states of Virginia and South Carolina (Cleland et al., 2007). The soil series is mainly comprised of Tatum and Appling types. Additional soil and watershed descriptive details can be found in Boggs et al. (2013, 2016).