| dc.description | Question: What is the relative importance of forest successional age,
environmental heterogeneity, landscape structure and spatial structure of
sampling sites on b-diversity of tropical dry forests (TDF)? How do the
magnitude of b-diversity and the relative influence of factors, processes and
mechanisms driving b-diversity differ at different spatial grains? What are the
effects of stand age on b-diversity?
Location: Yucata´n Peninsula, Me´xico.
Methods: Floristic composition was obtained from a hierarchical survey
performed in 276 sites distributed across 23 sampling landscapes (SL) (12 sites
per SL). Land-cover classes were derived from the classification of multi-spectral
SPOT 5 satellite imagery. We calculated landscape metrics of patch type
for each SL, and characterized local soil conditions for each sampling site. A
principal coordinates of neighbour matrices (PCNM) analysis was performed
to estimate spatial variables, and partial redundancy analysis was used
to decompose variation into spatial, stand age and landscape structure
components.
Results: The magnitude of b-diversity varied with spatial scale (grain size), and
was larger at the local than at the landscape grain. The magnitude of b-diversity
also decreased slightly but significantly with successional age. There were significant
differences in species composition among vegetation classes. Environmental
factors (local soil conditions, as well as landscape structure) and spatial
structure both contributed to woody plant b-diversity in our TDF landscape, but
their relative importance was scale-dependent. At the local grain size, both the
environment (mainly soil conditions) and the spatial structure strongly affected
b-diversity, while at the landscape grain, environmental factors (variation in soil
conditions, as well as landscape configuration) played a more prominent role.
Conclusions: The magnitude of b-diversity decreased with increasing spatial
grain and successional age, while the relative importance of mechanisms
influencing b-diversity was scale-dependent: both niche partitioning and dispersal
limitation affect b-diversity at the local grain size, while niche partitioning
prevails at the landscape grain. | |
