Data from: Effects of topography on tropical forest structure depend on climate context

1. Topography affects abiotic conditions which can influence the
structure, function, and dynamics of ecological communities. An increasing
number of studies have demonstrated biological consequences of fine-scale
topographic heterogeneity but we have a limited understanding of how these
effects depend on the climate context. 2. We merged high-resolution (1 m2)
data on topography and canopy height derived from airborne lidar with
ground-based data from 15 forest plots in Puerto Rico distributed along a
precipitation gradient spanning ca. 800 to 3,500 mm yr-1. Ground-based
data included species composition, estimated above-ground biomass (AGB),
and two key functional traits (wood density and leaf mass per area, LMA)
that reflect resource-use strategies and a trade-off between hydraulic
safety and hydraulic efficiency. We used hierarchical Bayesian models to
evaluate how the interaction between topography × climate is related to
metrics of forest structure (i.e., canopy height and AGB), as well as
taxonomic and functional alpha- and beta-diversity. 3. Fine-scale
topography (characterized with the topographic wetness index, TWI)
significantly affected forest structure and the strength (and in some
cases direction) of these effects varied across the precipitation
gradient. In all plots, canopy height increased with topographic wetness
but the effect was much stronger in dry compared to wet forest plots. In
dry forest plots, topographically wetter microsites also had higher levels
of AGB but in wet forest plots, topographically drier microsites had
higher AGB. 4. Fine-scale topography influenced functional composition but
had only weak or non-significant effects on taxonomic and functional
alpha- and beta-diversity. For instance, community-weighted wood density
followed a similar pattern to AGB across plots. We also found a marginally
significant association between variation of wood density and topographic
heterogeneity that depended on climate context. Synthesis: The effects of
fine-scale topographic heterogeneity on tropical forest structure and
composition depend on the climate context. Our study demonstrates how a
stronger integration of topographic heterogeneity across precipitation
gradients could improve estimates of forest structure and biomass, and may
provide insight to the ways that topography might mediate species
responses to drought and climate change.