Sampling
We sampled all plant life forms in eight plots of 20-m x 50-m (1,000
m2) subdivided into subplots of 10-m x10-m (Figures
S1, and S2). Four plots were allocated in different situations of
Caatinga near road at distances from 30-m to 170-m from BR-235, and four
plots in Caatinga far from roads at distances from 4,500-m to 8,500-m
from BR-235, thus totaling eight plots and 0.8 ha (Figure S3). The
distances were Log10 transformed for statistical
analysis that used distances as continuous variable. We divided species
into two components: woody (arboreal-shrubby) and non-woody
(herbaceous-subshrub). All woody individuals with a circumference at
ground level ≥ 10 cm and height ≥ 1 m, including woody lianas, were
considered as the woody component of vegetation. The survey of non-woody
species was carried out in two 10-m x 10-m subplots within each 20-m x
50-m plot (Figure S2), these being the first and last sampled subplots
of the woody component (Figure S1). The cover of all non-woody species
was estimated using the Braun-Blanquet method. The first five values (5
- 75 to 100% coverage, 4 -50 to 75%, 3 - 25 to 50%, 2 - 5 to 25% and
1 - 1 to 5%) of the Braun-Blanquet method refer to coverage while the
last two value scales (+ - species with many individuals and low
coverage, and r - rare species with low coverage) are primarily
estimated by abundance (Munhoz & Araújo, 2011). From the Braun-Blanquet
scale, we calculated coverage area (CA) and relative coverage (RC) using
averaged values for each category (Kent, 2012).
We classified all species according to their life form using Raunkiaer’s
life form system (Martins & Batalha, 2011). Species were also
classified according to functional characteristics related to
resilience/resistance to disturbances including resprouting ability,
urticancy/toxicity and spinescent succulents, and according to
functional characteristics affected by goat herbivory, including
endozoochory, because of the fleshy fruits, and nitrogen fixation,
because of the low C/N (Carrión et al. , 2017; Leal et al. ,
2003; Severson & DeBano, 1991). Because of its dubious life form, the
hemiepiphyte Hylocereus setaceus (Salm-Dyck) Ralf Bauer was
considered in both, the woody and the non-woody community.
All of the species found with regrowth after a loss of aerial parts were
considered resprouters, while all species with succulent and spiny
structures were considered succulent spinescent (Carrión et al. ,
2017). Urticancy/toxicity was considered if species exhibited some
vegetative organ with urticancy or that produce some toxic compound that
affects goats, sheep and cattle (Bezerra et al. , 2012). We
considered nitrogen fixers as those species and genera that have a
record of positive nodulation by nitrogen-fixing bacteria in the
literature (Sprent, 2009). Species were considered endozoochoric through
records in the literature or morphological observation (Pijl, 1982). In
this study, secondary dispersion records were not considered.
In addition, we used maximum diameter and maximum height per species for
the species of the woody component as quantitative functional traits.
For this we calculated the mean for the three highest individuals and
the three largest diameters of each species. We also used relative
coverage (RC, in m2), calculated from Braun-Blanquet
categories, of each non-woody species as a functional trait.
Species were recorded and later identified by expert consultation,
herbaria comparison and/or specialized literature. The taxonomic system
adopted was APG IV (The Angiosperm Phylogeny Group, 2016). We used
information available on the Tropicos platform (Missouri Botanical
Garden, 2018) and Taxonomic Name Resolution Service tool version 4.0
(Boyle et al. , 2013) for appropriate species nomenclature and
respective abbreviations of the authors.