The trait-mediated trade-off between growth and survival depends on tree sizes and environmental conditions

Interspecific relationships between growth and survival are critical
determinants of tree species diversity maintenance in forests. The
trade-offs between growth and survival in co-occurring tree species are
believed to arise along a continuum of life-history strategies. For
example, co-occurring species range from those that grow slowly and
survive well in resource-poor environments to those that grow quickly but
have low survival rates in resource-rich environments. However,
uncertainties remain regarding how growth-survival trade-offs are related
to species traits, tree sizes, or environmental conditions. We examined
how the relationships between species traits and growth–survival
relationships shift in response to changes in stem sizes and across census
periods with different climate conditions (frequency of strong winds,
drought intensity) across 45 co-occurring tree species based on 23 years
of growth and survival records in a warm temperate rain forest on
Yakushima Island, Japan. We developed hierarchical Bayesian models of
relative growth and survival rates, including leaf traits, wood density,
and 95-percentile maximum stem diameter as explanatory variables. We
tested the relationships between estimated trait-mediated growth–survival
relationships and the intensities of climate events during five census
periods. Each trait’s effects on growth–survival relationships differed
across the five census periods in response to climate conditions.
Interspecific growth–survival relationships affected by a single trait
axis for leaves or wood tended to be negative. In contrast, those affected
by the maximum stem diameter tended to be positive. Such
trends increased with more frequent strong winds or more intense
droughts. The single-trait effects on growth–survival relationships were
stronger for smaller sizes than for larger sizes. For all traits combined,
we found a significant growth–survival trade-off only for small-sized
stems in three of five census periods. Synthesis: Our results indicate
that the effect of species traits on the growth–survival relationships
depended on tree sizes, the census periods, or both in response to the
frequency or intensity of climate events. We argue the importance of
incorporating spatial and temporal variations in environmental conditions
into long-term data from tree census to predict forest dynamics.