DOI: 10.5061/dryad.sbcc2frh4
title: Warming-induced changes in seasonal priority effects drive shifts in community composition

description: Shifting community assembly dynamics are an underappreciated mechanism by
 which warming will alter plant community composition. Germination timing
 (which can determine the order in which seedlings emerge within a
 community) will likely shift unevenly across species in response to
 warming. In seasonal environments where communities reassemble at the
 beginning of each growing season, changes in germination timing could lead
 to changes in seasonal priority effects, and ultimately community
 composition. We test this expectation by assembling mesocosms of fifteen
 species in one of two orders – “ambient” assembly order or “warmed”
 assembly order – based on the order in which the constituent species
 germinated under ambient and warmed conditions. Community composition
 differed significantly between mesocosms assembled in ambient versus
 warmed orders. The impact of assembly order on species mean biomass was
 largely explained by how much earlier (or later) a species arrived in the
 warmed-order treatment relative to the ambient-order treatment. Species
 whose germination phenology advanced more under warmed conditions relative
 to ambient conditions showed greater relative increases in biomass under
 the warmed assembly treatment. These findings demonstrate that warming can
 drive community assembly and shape community composition by reordering the
 relative timing of germination among species. These findings enhance our
 ability to predict which species are likely to benefit from warming and
 which may decline based on how warming may shift assembly order,
 ultimately informing how warming may alter plant communities.
description: # Warming-induced changes in seasonal priority effects drive shifts in
 community composition
 [https://doi.org/10.5061/dryad.sbcc2frh4](https://doi.org/10.5061/dryad.sbcc2frh4) ## Description of the data and file structure This dataset is from a mesocosm experiment exploring how changes in the timing of plant species' germination with warming impacts plant community composition. The assembly (order of germination) treatments were derived from a growth chamber experiment where all the species in the experiment germinated under ambient or +3 C warmed spring conditions and germination time was assessed.  ### Files and variables #### File: Dawson-Glass\_ECY24-0464\_assembly\_data.csv **Description:** The primary dataset associated with this manuscript, containing mesocosm-level treatment information and final biomass values for each individual plant growth in the experiment. ##### Variables * Pot: Mesocosm ID number. * Species: Plant species latin name. * init_height: Initial height (in centimeters) of the individual plant, taken prior to its planting into the experiment. * Sp_code: Abbreviated code of the species name using the first three letters of the species and genus. * Treatment: Treamtmet ID. Here, Ambient Order refers to the "ambient assembly" treatment order as determined in the growth chamber trial using average spring conditions. Warm Order refers to the "warm assembly" treatment order as determined in the germination trial using +3 degrees C spring conditions. * Biomass: Biomass of the individual plant (in grams), collected at the end of the experiment. #### File: Dawson-Glass\_ECY24-0464\_germination\_trial\_treatments.csv **Description:** Treatment information for the growth chamber germination trial data. ##### Variables * Species: Species latin name. * tray: Tray ID number. * treatment: Treatment in germination trials, either ambient (growth chamber settings set to average spring conditions) or warm (growth chanmber set to +3 C average spring conditions). #### File: old\_field\_species\_tree\_101023 **Description:** Phylogenetic tree of the species included in the study (code used to generate this tree available in Dawson-Glass ECY24-0464 code.R) #### File: Dawson-Glass\_ECY24-0464\_species\_info.csv **Description:** Information on each species in the experiment, including functional type, native status, and day the species was introduced in the experiment. ##### Variables * Sp_code: Abbreviated code of the species name using the first three letters of the species and genus. * Species_latin: Species latin name. * Arrival_date_amb: Day that this species was introduced into the assembly experiment in the ambient arrival treatment. * Arrival_date_warm: Day that this species was introduced into the assembly experiment in the ambient warm treatment. * Status: Species' native status (in the state of Ohio, USA). * Functional: Species' functional growth form. #### File: Dawson-Glass\_ECY24-0464\_germination\_trial\_data.csv **Description:** Data from the growth chamber germination trials used to determine order of introduction in the mesocosm experiment. ##### Variables * date: Date that a germintion tray was assessed. * tray: Tray ID number (NA indicates no germination that day). * number germinated: Number of seedlings found in the tray on a given day (NA indicates no germination that day). ## Code/software All code used for transformation, analysis, and visualization of the accompanying data is available in "Dawson-Glass ECY24-0464 code.R." Analyses were conducted in R version 4.3.1.