Eastern North Carolina chronosequence stands:
The ~85-year-old (NC_E 85yo), ~35-year-old (NC_E 35yo), and ~15-year old (NC_E 15yo) eastern NC chronosequence stands were located in the Blackwood Division of Duke Forest (35° 58’ 24.89”, -79° 6’ 1.55”). Mean annual precipitation (1945–2015) for the area is 1144 ± 162 mm, with 619 ± 116 mm falling between April and September. Annual mean temperature is 14.36 °C. NC_E 85yo was a naturally established stand comprised of mixed hardwood species Q. alba , Quercus michauxii Nutt., L. tulipifera , Liquidambar styracifluaL, and hickory species Carya tomentosa Sarg. and Carya glabra Miller with a mean canopy height of 27.5 m (Oishi et al.,2010). NC_E 35yo was located less than 4 km from NC_E 85yo and was part of the former Duke FACE project ambient plots. This site was clear-cut in 1982 to remove a 50-year-old mixed pine forest and was replanted in 1983. The stand was dominated by Pinus taeda L. butQ. alba , L. tulipifera, Acer rubrum L, L. styraciflua, Cornus florida L. and Prunus serotina occurred in the understory and stand gaps. Mean height of the mid-canopy Q. alba and L. tulipifera trees in the NC_E 35yo stand was 15.1 m. Soils were gravelly loam of the Iredell series with majority of the rooting zone occurring at 45–65 cm depth (Domec et al., 2012).
A. saccharum trees were sampled in the NC_E chronosequence from an additional lowland hardwood stand located 15 km from the ones described above. Fagus grandifolia Ehrh. was the dominant canopy tree species of this lowland hardwood site, but Q. alba , Q. rubra , L. styraciflua , and A. saccharum occurred frequently in the understory. This site was also part of the Duke Forest but was characterized by a deep and well-drained soil with minimal disturbance. The mean height of ~15 and ~35 years old A. saccharum trees were 9.2 and 19.5 m, respectively.