2.4 Sapwood area
An increment borer was used to extract two wood cores from 18 trees in
the riparian buffer zone, 19 trees in the mid-hillslope, and 15 trees in
the upland-hillslope. All the tree core samples were collected adjacent
to, but outside of the survey plots and sap flux stations. The amount of
sapwood from each core was measured with a ruler in the lab and linked
to the species stem density and dbh data to derive sapwood area in the
monitored trees in the sap flux stations and sapwood area in the trees
in the survey plots (Table 1). Sapwood area from the monitored trees in
the sap flux stations was used to compute tree transpiration. Sapwood
area and tree density from the trees in the survey plots were used to
scale tree-level transpiration to the watershed-level.