Study area
NEON operates at 47 terrestrial field sites located across 20
climatically and ecologically variable domains in the United States, and
each domain has a core site and two satellite sites (Barnett et al.,
2019). Forests occupy 24 terrestrial NEON sites across 12 domains and
represent the major forest ecosystems throughout North America, north of
Mexico (Figure 1; Table S1). NEON sites capture the wide variety of
climatic conditions, disturbance regimes, habitat structures, and
biodiversity of North America forests. These sites cover a large
gradient of mean annual temperature (-7.8 – 27.0 ºC) and precipitation
(0 – 2,492 mm/yr) and cover a wide range of forest biomes, including
boreal forests, temperate rainforests, temperate seasonal forests, and
woodland/shrublands (Figure 2).
We utilized data from NEON’s bird and vegetation surveys, flux towers,
and Airborne Observation Platform (AOP) (Table S2) to assess 12
variables of forest structure and productivity, 3 variables of
topography, and 2 climate variables (Table S3). We use data from 2018
and 2019 as these data products were collected consistently across
nearly all the selected sites at least once during this period. The area
around each bird survey point within an 80m radius was used to average
scale-dependent habitat heterogeneity and productivity measurements.
This scale was selected based on the highest performing models, measured
as the maximum mean Area Under the Receiver Operating Characteristic
Curve (AUC), that predicted occupancy for a community of avian species
within this study area (Cooper et al., 2020b).