Western North Carolina chronosequence stands:
The ~85-year-old (NC_W 85yo) (35° 3’ 33.12”, -83° 25’ 39”) and ~35-year-old (NC_W 35yo) (35° 3’ 55.22”, -83° 26’ 17.54”) stands in the western NC chronosequence were located in the Coweeta Basin, at the USDA Forest Service Coweeta Hydrologic Laboratory. Soils were fine-loamy with a variable depth of approximately 35 to >90 cm. The NC_W 85yo was a mature, secondary forest dominated by L. tulipifera, Q. alba, Acer rubrum L., Betula lenta L., and dense Rhododendron maximum L. understory (Oishiet al. , 2018). The NC_W 35yo stand had similar species composition, but was clearcut in 1976−1977 (Swank & Webster, 2014). The ~15-year-old NC stand (NC 15yo) (35° 10’ 47.71”, -83° 29’ 44.98”) was a selectively harvested stand located nearby (<20 km) in the Nantahala National Forest with similar species composition.
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”). NC_E 85yo was a naturally established stand comprised of mixed hardwood species Q. alba , Quercus michauxii Nutt., L. tulipifera , Liquidambar styraciflua L, and hickory speciesCarya tomentosa Sarg. and Carya glabra Miller (Oishiet 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. but Q. alba , L. tulipifera, A. rubrum , L. styraciflua, Cornus florida L. and Prunus serotina Ehrh. occurred in the understory and stand gaps. 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.