Data from: Disentangling competitive versus climatic drivers of tropical forest mortality

1. Tropical forest mortality is controlled by biotic and abiotic
processes, but how these processes interact to determine forest structure
is not well understood. Using long-term demography data from permanent
forest plots at the Paracou Tropical Forest Research Station in French
Guiana, we analyzed the relative influence of competition and climate on
tree mortality. We found that self-thinning is evident at the stand level,
and is associated with clumped mortality at smaller scales (< 2 m)
and regular spacing of living trees at intermediate (2.5-7.5 m) scales. A
competition index based on spatial clustering of dead trees was used to
build predictive mortality models, which also accounted for climate
interactions. 2. The model that most closely fitted observations included
both the competition index and climatic variables, with climate-only and
competition-only models performing worse than the full model. There was
strong evidence for size-specific mortality, with highest mortality for
small and very large trees, as well as sensitivity of trees to drought,
especially when temperatures were high, and when soils were water
saturated. The effect of the competition index was more complex than
expected a priori: a higher CI index was associated with lower mortality
odds, which we hypothesize is caused by gap-phase dynamics, but there was
also evidence for competition-induced mortality at very high index values.
3. The strong signature of competition as a control over mortality at the
stand and individual scales confirms that it plays a very important role
in determining tropical forest structure. The complexity of the
competition-mortality relationship and its interaction with climate
indicates that a thorough consideration of the scale of analysis is needed
when inferring the role of competition in tropical forests, but
demonstrates that climate-only mortality models can be significantly
improved by including competition effects, even when ignoring
species-specific effects. 4. Synthesis Empirical models such as the one
developed here can help constrain and improve process-based vegetation
models, serving both as a benchmark and as a means to disentangle
mortality processes. Tropical ecosystem dynamic models would benefit
greatly from explicitly considering the role of competition in stand
development and self-thinning while modeling demography, as well as its
interaction with climate.