2.3 Vegetation survey
Sixteen 10-meter radius survey plots were established in 2015 to quantify diameter at breast height (dbh) and stem density of trees in the mid-hillslope and upland-hillslope. Four 152 m2plots were used to assess trees in the riparian buffer (Boggs et al., 2016). We did not used the 10-meter radius sampling design that was used in the mid-hillslope and upland-hillslope zones for the riparian buffer because it would have stretched beyond the boundary of the 15.2-meter wide buffer. Therefore, rectangular-shaped plots were used to characterize the overstory vegetation in the buffer (Figure 1).
Tree diversity of the watershed in this study was composed of loblolly and Virginia pines, and several native hardwoods (Table 1). The area covered by these species varied across the watershed with loblolly pine, red maple, sweetgum, and tulip poplar having higher densities in the riparian buffer than in other zones. The oak species concentrated on the upper hillslopes where chestnut oak density equaled 117 stems ha-1, and white oak density equaled 85 stems ha-1. Species sapwood area represented 86% of the basal area in the monitored trees in the buffer, 72% in the mid-hillslope, and 74% in the upland-hillslope. Sapwood area in oak species represented the smallest percentage of the basal area when compared to the other trees, averaging 47%, while loblolly pine averaged 91%.