3.3 Sap flux density
Daily growing season sap flux density (J s) varied across species, zones, and years (Table 2). In the zone vs zone comparison in 2015, the loblolly pine, sweetgum, Virginia pine, and white oak J s in the riparian buffer were significantly higher than J s in those same species in the mid-hillslope and upland-hillslope (Table 2). In contrast, the tulip poplar and red maple J s in the riparian buffer were significantly lower than tulip poplar and red maple J s in the mid-hillslope.
In the zone vs zone comparison in 2016, the loblolly pine was the only species where J s in the riparian buffer was significantly higher than J s in the mid- and upland-hillslopes (Table 2). The red maple and white oakJ s were not significantly different across zones. The tulip poplar and Virginia pine had significantly higherJ s on the mid-hillslope than did the same species in the riparian buffer. The mid-hillslope J s in sweetgum trees were significantly higher than sweetgums located in the riparian buffer and upland-hillslope.
In the year vs year comparison, the loblolly pine, tulip poplar, and white oak were the only species where J s did not change significantly. J s is all other species increased or decreased from 2015 to 2016.
Growing season means showed that white oak J strees were not significantly different across zones (Table 2). TheJ s in loblolly pine, sweetgum, and Virginia pine decreased significantly across zones (riparian buffer > mid-hillslope > upland-hillslope) and decreased with decreasing soil moisture content (Table 2). J s in tulip poplar and red maple increased significantly across zones (riparian buffer < mid-hillslope) and increased with decreasing soil moisture content.