5. Materials and Methods
5.1 Study sites
We selected ten forest stands across four regions in the eastern US that
spanned a hydroclimatological gradient (Fig. 1). Four of the stands were
~85-year-old temperate deciduous forest AmeriFlux
network sites (US-MMS, US-CWT, US-Dk2, and US-MOz) in the states of
Indiana (IN), North Carolina (NC), and Missouri (MO). The gradient
approach allowed us to understand how key plant hydraulic traits varied
as a function of climate. Additionally, The ~85-year-old
stands in IN and NC were each end-members of a chronosequence (including
~15- and ~35-year-old stands co-located
within 20 km of the ~85-year-old stand). The
chronosequences in NC and IN allowed us to investigate how the
relationship between ΨL regulation and vulnerability to
hydraulic failure varied with stand age in regions experiencing a
similar climate.