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.