2.5. Data analysis
2.5.1. Tree species richness, density and composition
All data analysis was performed in the statistical computing
program R (R Core Team, 2013). To observe the accumulation of
species richness within each landscape element we conducted
rarefaction analyses using the function ‘specaccum’ in R package
‘vegan’ (Oksanen et al., 2013). Accumulation curves were calculated
based on both (i) survey sites (using the ‘exact’ method)
and (ii) individuals sampled (using the ‘rarefaction’ method).
We modelled species density (sensu Gotelli and Colwell, 2001)
for each element using generalised linear mixed models (GLMMs)
in the ‘lme4’ package (Bates et al., 2013). Our response variable
was the total number of species recorded at each site, and was
modelled as a Poisson distribution. Each transect was specified as
a random effect to account for non-independent error structures
associated with potential clustering of study sites (Zuur et al.,
2011), and the landscape element that sites were located within
(i.e. young plantation, mature plantation, etc.) was specified as a
fixed effect. Landscape elements were considered an important
influence on species richness where 95% confidence intervals (CI)
for parameter estimates did not overlap zero when compared to
the reference element (unlogged forest).