Site Selection
Two geographically distinct groups of redcedar woodlands were sampled to
answer differing sets of questions: one set of sample sites aimed to
capture the spatial structure of redcedar-dominated stands across a
range of size classes and the second evaluated the interactions between
redcedar and codominant deciduous species. The locations of the first
set of 15 surveys, which we term the ‘Midwest’ dataset, center in the
Ohio River valley and include samples from Ohio, Pennsylvania, and
Kentucky (Figure 1). Survey sites in the Midwestern dataset were
selected by examining aerial imagery of wooded lands and grasslands to
determine if redcedar were present. Redcedar is an evergreen conifer
that is easily identifiable in aerial images (e.g. Wang et al., 2017).
The second set of sample plots, termed the ‘Oklahoma’ dataset were
located in the Cross Timbers region of central Oklahoma, near Stillwater
(Figure 1). The Cross Timbers represent the transition zone between the
eastern deciduous forest and the Great Plains (Francaviglia 2000;
Stambaugh et al. 2009). To evaluate the interaction between
encroaching redcedar and other trees in the Cross Timbers, point-pattern
data were recorded at 13 neighboring woodlands with varying proportions
of codominant redcedar and Quercus species, and other deciduous
trees.
Sampling
Design
From a random starting point, meter tapes were laid out in a 10 m x 20 m
(x, y) grid aligned along the dominant environmental gradient (i.e.,
slope) (Wiegand et al. 2013). All trees within the sample plot
had the following attributes recorded: coordinates (to nearest 0.1 m),
species name, alive or dead, and diameter at breast height (DBH) (trees
> 1.3 m). Plots were extended in 10 m increments along the
x-axis until a minimum of ~50 trees were recorded
(average sample > 88 trees). All samples were collected
from March 2020-December 2021.