DOI: 10.5061/dryad.n5tb2rbvr
title: Closing the life cycle of forest trees: The difficult dynamics of seedling-to-sapling transitions in a subtropical rain forest

description: 1. Experimental and observational studies on seedling dynamics posit
 mechanisms that can influence forest diversity, structure, and function.
 However, high mortality and slow growth of seedlings make it difficult to
 evaluate the importance of this life-history filter to total tree life
 history. Quantifying the duration and transition of the seedling phase
 would help us understand this ‘black box’ in tree population biology. 2.
 We used a 16-year dataset of comprehensive seedling-to-sapling demography
 from a subtropical rain forest to construct population models that capture
 temporal demographic fluctuations for eight major tree species. We used
 data-driven demographic models and simulations to estimate the transition
 ratios from newly recruited seedlings to saplings of 2 m height and the
 time taken to attain 2 m height for a newly recruited seedling conditional
 on its survival. 3. Projections among species estimated that as few as 57
 to more than 40,000 seedlings (with a median of 2,087) were required to
 make a single 2 m high sapling. Furthermore, it would take 22 to 200 years
 (with a median of 47) for a newly recruited seedling to become a 2 m high
 sapling. We found that temporal variation in demographic rates could
 greatly reduce the number of seedlings per established sapling, but not
 passage times. We also identified the importance of consistently fast
 growth rates for seedlings to escape the high mortality of early stages.
 4. Synthesis. Our findings demonstrate that high mortality in the very
 early seedling stage severely limits the probability that a newly
 recruited seedling will transition to the sapling stage. Although the
 passage times vary, we found this to be true across species with a range
 of life-history strategies. Only seedlings with consistently fast growth
 rates are expected to pass through this life-history filter. Findings from
 seedling studies should consider how short term studies of seedling
 demography might capture the rare exceptional individuals and exceptional
 conditions that might define the dynamics of this seedling bottleneck.
description: This dataset contains a 16-yr seedling demographic data and a
 5-yr sapling survival data of eight major tree species in the Fushan
 Forest Dynamics Plot (FDP), Taiwan. The seedling data span from February
 2003 to February 2019, while the sapling data span from 2004 to 2009. In
 November 2002, 318 1-m<sup>2</sup> seedling plots were
 established along four 400 m trails within the Fushan FDP. All seedlings
 of the eight study species &lt;1 cm dbh within the seedling plots were
 tagged with a unique number, measured for height to the apical bud, and
 identified to species. In subsequent censuses, surviving seedlings were
 measured and new recruits were tagged, measured and identified to species.
 We monitored the seedling dynamics every three months from February 2003
 to May 2010, and every six months thereafter until February 2019. We
 annualized the data for use in the demographic process model, which we ran
 on an annual time step.
description: <strong>Seedling survival data</strong> (file name:
 fs_seedling_surv_data.txt) This file contains the
 annual seedling survival data of the eight major tree species in the
 Fushan Forest Dynamics Plot from February 2003 to February 2019. There are
 ten columns in this file: 
 'census' for the seedling census number
 'year' for census year
 'date' for census date
 'tag' for the tag number of each seedling
 'sp' for species code
 'ht' for seedling height
 'status' for seedling survival status in the current
 census 'surv' for seedling survival in the
 following census (1: alive, 0: dead)
 'growth' for seedling growth increment in the
 following census (in cm) 'interval' for
 time interval between seedling censuses (in years) 
   <strong>Seedling growth
 data</strong> (file name: fs_seedling_growth_data.txt)
 This file contains the seedling growth data of the eight major
 tree species in the Fushan Forest Dynamics Plot from February 2003 to
 February 2019. There are 11 columns in this file: 
 'census' for the seedling census number
 'year' for census year
 'date' for census date
 'tag' for the tag number of each seedling
 'sp' for species code
 'sprout' for sprout identifier
 'ht' for seedling height
 'status' for seedling survival status in the current
 census 'surv' for seedling survival in the
 following census (1: alive, 0: dead)
 'growth' for seedling growth increment in the
 following census (in cm) 'interval' for
 time interval between seedling censuses (in years) 
 <strong>Sapling survival data</strong> (file name:
 fs_sapling_surv_data.txt) This file contains the
 sapling survival data of the eight major tree species in the Fushan Forest
 Dynamics Plot from 2004 to 2009. There are 8 columns in this
 file: 'tag' for the tag number of
 each sapling 'sp' for species
 code 'date1' for date of the first
 census 'status1' for sapling survival
 status in the first census 'size1' for dbh
 in the first census (in mm) date2' for date of
 the second census 'status2' for sapling
 survival status in the second census
 'time1' for census interval between the first and
 second census (in years)