DOI: 10.5061/dryad.xwdbrv1cn
title: Data from: Demographic traits improve predictions of spatiotemporal changes in community resilience to drought

description: Communities are increasingly threatened by extreme weather events. The
 cumulative effects of such events are typically investigated by assessing
 community resilience, i.e., the extent to which affected communities can
 achieve pre-event states. However, a mechanistic understanding of the
 processes underlying resilience is frequently lacking and requires linking
 various measures of resilience to demographic responses within natural
 communities. Using 13 years of data from a shrub community that
 experienced a severe drought in 2005, we use generalized additive models
 to investigate temporal changes in three measures of resilience. We assess
 whether community-weighted, species-specific demographic traits such as
 longevity and reproductive output can predict changes in resilience and
 how the performance of these traits compares to more commonly used plant
 functional traits such as leaf area or root dry-matter content. We find
 significant spatiotemporal variation in community dynamics after the
 drought. Overall, demographic traits are better at predicting absolute and
 relative resilience in total plant cover, but functional traits outperform
 demographic traits when resilience in community composition is assessed.
 All resilience measures show non-linear and context-specific responses to
 demographic and functional traits; and these responses depend strongly on
 the severity of initial drought impact. Synthesis: Our work demonstrates
 that a full picture of the mechanisms underlying community responses to
 drought requires the assessment of numerous species-specific
 characteristics (including demographic and functional traits) and how
 these characteristics differentially affect complementary measures of
 community changes through time.  
description: <i>Quantifying community composition</i>
 In order to assess community composition before, during, and
 after a severe drought event in Doñana National Park, 18 permanent plots
 of 25 m<sup>2</sup> (5 × 5 m) were established in November
 2007 (two years after the drought) on a gradient of drought impact. The
 plots were located at three sites (with six plots per site): Raposo (N
 37º0′2″, W 6º30′20″; at 18 m a.s.l.), Marqués (N 37º0′45″, W 6º31′50″; 21
 m a.s.l), and Ojillo (N 36º59′40″, W 6º30′50″; 30 m a.s.l.). To avoid
 spatial autocorrelation, all plots were separated by at least 50 m from
 each other. Species plant cover was estimated from contacts with branches
 along transects within plots; these contacts were divided into two
 categories corresponding to living or dead canopy. Dry organs with signs
 of old decay (stumps, decomposed stems, branches without thin tips) were
 excluded. Thus, canopy prior to the episode was considered as the sum of
 living and dead (i.e., dry) plant canopy in 2007. Relative abundance of
 each species per plot in years after the extreme drought was calculated as
 the proportion of their contacts of living canopy relative to the sum of
 the contacts of living canopy of all species. Similarly, the total vegetation
 cover per plot was calculated as the summed contacts of
 living canopy of all
 species. Relative abundances previous to the drought were
 calculated as the sum of the living and dead canopy of 2007 of each
 species relative to the sum of the living and dead canopy of 2007 for all
 species. <i>Demographic
 traits</i> We obtained four demographic traits
 for each plant species encountered in the sampling plots: age at first
 reproduction (Age<sub>FR</sub>), maximum longevity (L),
 minimum size at first reproduction (Size<sub>FR</sub>), and
 ratio of adults to recruits (R/A). To calculate the first three traits for
 each species, 50 plants growing near the plots were randomly selected in
 June, 2019, in vegetation patches without signs of drought-induced
 impact. We estimated plant age from yearly growth scars in the main
 shoots. We calculated age at first reproduction from inverse prediction
 (Probability of not flowering = 0.9) obtained from the logistic nominal
 regression between reproduction stage and plant age following the standard
 procedure. We obtained minimum size at first reproduction using receiver
 operating characteristic (ROC) curves. Lastly, we approximated maximum
 longevity as the 90<sup>th</sup> percentile of estimated age
 from yearly growth scales in the 50 plants growing near the plots in
 patches not impacted by drought; since scars disappear in older plants, 5
 to 10 years age intervals - depending on species’ growth form and size -
 were added to the older scars in larger plants. We calculated ratios of
 recruits to adults (R/A) from data collected in the years 2007, 2008, 2013
 and 2019. Data included the total number of juvenile non-reproductive
 plants (recruits) and the total number of adults of each species found in
 plots with low drought impact (6 plots).
 <i>Functional traits</i> We
 calculated community-weighted means of eight above- and two below-ground
 traits, which are among the most commonly used to describe plant
 functional types and have previously been obtained in the study plots in
 late spring 2013. Above-ground functional traits included plant height
 (Phg), leaf area per unit of leaf dry mass (SLA), leaf dry matter content
 (LDMC), stem dry matter content (SDMC), leaf nitrogen concentration (LNC),
 leaf chlorophyll concentration (LChl), isotopic carbon fraction
 (δ<sup>13</sup>C), and seed mass
 (S<sub>mass</sub>). Below-ground traits included specific root
 area (SRA) and root dry matter content (RDMC).
description: The dataset contains all data and R code to replicate the
 analyses in Paniw et al. 2021. Demographic traits improve predictions of
 spatiotemporal changes in community resilience to drought.
 <em>Journal of Ecology</em>