DOI: 10.5061/dryad.66v1c
title: Data from: Nonrandom, diversifying processes are disproportionately strong in the smallest size classes of a tropical forest

description: A variety of ecological processes influence diversity and species
 composition in natural communities. Most of these processes, whether
 abiotic or biotic, differentially filter individuals from birth to death,
 thereby altering species’ relative abundances. Nonrandom outcomes could
 accrue throughout ontogeny, or the processes that generate them could be
 particularly influential at certain stages. One long-standing paradigm in
 tropical forest ecology holds that patterns of relative abundance among
 mature trees are largely set by processes operating at the earliest life
 cycle stages. Several studies confirm filtering processes at some stages,
 but the longevity of large trees makes a rigorous comparison across size
 classes impossible without long-term demographic data. Here, we use one of
 the world’s longest-running, plot-based forest dynamics projects to
 compare nonrandom outcomes across stage classes. We considered a cohort of
 7,977 individuals in 186 species that were alive in 1971 and monitored in
 13 mortality censuses over 42 y to 2013. Nonrandom mortality with respect
 to species identity occurred more often in the smaller rather than the
 larger size classes. Furthermore, observed nonrandom mortality in the
 smaller size classes had a diversifying influence; species richness of the
 survivors was up to 30% greater than expected in the two smallest size
 classes, but not greater than expected in the larger size classes. These
 results highlight the importance of early life cycle stages in tropical
 forest community dynamics. More generally, they add to an accumulating
 body of evidence for the importance of early-stage nonrandom outcomes to
 community structure in marine and terrestrial environments.
description: Survivorship of 7977
 trees in six size classes over 42 yearsThese data were
 collected from a permanent forest dynamics plot in rain forest at Davies
 Creek, 25 km southwest of Cairns in Queensland, Australia. Large trees are
 mapped and tagged over the entire plot, smaller trees, saplings and
 seedlings are mapped and tagged along nested transects through the plot.
 The dataset describes the fate of 7977 individuals that were alive on the
 plot in 1971, and whose fates were recorded through 13 mortality censuses
 to 2013. Each row is data for a single stem. Column 1 'SPEC'
 gives the species code for the stem (Latin binomials available from the
 authors upon request). Column 2 'MAP' indicates the year in
 which the stem was first mapped. The earliest map dates are 1963. Column 3
 'DEAD' indicates the survey year in which the stem was recorded
 dead. A '0' indicates the stem was still alive at the last
 survey in 2013. Column 4 'SCLASS' indicates the size class (1-6)
 to which the stem was assigned for the purposes of the randomization
 analyses described in the text. Column 5 'HG' indicates whether
 stems in that size class were measured for height or girth on the map
 date. Column 'Ht1' indicates height (decimal feet) at the map
 date. Column 'Gr1' indicates girth (decimal inches) on the map
 date.Green_etal_2015_PNAS.xlsx