3.6 Watershed-level transpiration
Growing season weighted watershed-level transpiration (Tw ) was similar in 2015 (i.e., 284 mm) and 2016 (i.e., 285 mm, Table 4). In contrast, the growing season watershed-level transpiration (by zone, T z) in the riparian buffer ranged from 334 to 363 mm while growing seasonT z in the mid-hillslope ranged from 306 to 313 mm. The growing season T z on the upland-hillslope produced the lowest transpiration, 245 mm in 2015, and 246 mm in 2016. The daily growing season T z in 2015 and 2016, respectively, averaged 1.7 (0.06) mm day-1 and 1.4 (0.06) mm day-1, and reached a maximum of 2.6 mm day-1 and 2.7 mm day-1 in the riparian buffer, 1.2 (0.05) mm day-1 and 1.0 (0.05) mm day-1, and a maximum of 2.4 mm day-1and 2.5 mm day-1 on the mid-hillslope, and 1.0 (0.03) mm day-1 and 0.9 (0.03) mm day-1, and a maximum of 2.0 mm day-1 on the upland-hillslope. There was also a strong seasonal component to T win 2015 and 2016, where 80% (i.e., 284 mm) and 79% (i.e., 285 mm) of the stand transpiration occurred in the growing season. Regardless of which zone was used to derive T w, the non-growing season T w was always statistically lower than the growing season T w (Table 4).
The annual T w was 361 mm in 2015, and 370 mm in 2016. In 2015 and 2016, loblolly pine accounted for 40-50%, white oak 13-14%, tulip poplar 11-14%, sweetgum 6-7%, Virginia pine 4-8%, and red maple 4% of growing season T w and Tz.