Study design and field Sampling
The field sampling took place during the growing season, from August
2016 to July 2018. Presence or absence of all vascular plants was
recorded within each of the 100 x 100 m plots (plot level). To obtain
cover estimates of plant species, and to be able to quantify resource
heterogeneity within plots, we additionally established six 5 x 5 m
subplots located within each plot (subplot level). The cover was
visually recorded as one of three categories (1): 1 – 5 % cover or
less than 15 individuals, (2): 6 – 25 % cover or more than 15
individuals, or (3): 26 – 100 % cover. For calculations, cover
estimates were transformed to 2.5 %, 15 % and 35 %, respectively. To
more precisely resolve the uneven cover distribution, these cover
categories were subdivided on a quasi-logarithmic scale. We separated
the cover into two height strata. The herb and shrub layer comprised all
vascular plants and all shrubs or woody species smaller than 5 m in
height, subsequently called understory vegetation. The tree layer
comprised all species taller than 5 m. Species names follow the
nomenclature of Rothmaler (2017).
Additionally, at each plot centre a single terrestrial laser scan (TLS)
was conducted between September 2017 and May 2018. Each scan was carried
out with a Faro Focus 3D 120 (Faro Technologies Inc., Lake Mary, USA)
laser scanner set to 0.044° angular resolution. A full 360° horizontal
and 150° vertical angular range was covered, resulting in a maximum of
29 million points per scan. The scanner was placed on a tripod at 1.3 m
from the ground.