DOI: 10.5061/dryad.k3j9kd5ph
title: Data from: Combined heat and drought events reduce first-year survival of tree seedlings, especially at southern range margins

description: These are the data associated with a project testing how experimental
 drought and heat treatments impact survival and growth of first-year tree
 seedlings common to the northeastern United States. The datasets include
 seedling-level metrics of survival and growth (height and total biomass),
 approximate substrate moisture throughout the experimental period, and
 data on traits including leaf mass per area, minimum epidermal
 conductance, turgor loss point, and root-to-shoot biomass ratio.
description: # Data from: Combined heat and drought events reduce first-year survival
 of tree seedlings, especially at southern range margins Dataset DOI:
 [10.5061/dryad.k3j9kd5ph](https://doi.org/10.5061/dryad.k3j9kd5ph) ##
 Description of the data and file structure Project: Combined heat and
 drought events reduce first-year survival of tree seedlings, especially at
 southern range margins Authors: Emily G. MacDonald, Melissa D. Cullina,
 Bryan J. Peterson, Jay W. Wason Date compiled: December 2025 Data compiled
 by Emily MacDonald ### Files and variables Note: NA= Not applicable, or
 absent information #### File: final_biomass_RS.csv **Description:** These
 data contain the total biomass and root-to-shoot biomass ratio of a subset
 of seedlings from this experiment, sampled at the end of the growing
 season. ##### Variables * ID: unique seedling identifier *
 chamber: treatment chamber (representing on experimental unit and a single
 application of a heat and drought treatment). There are 27 total chambers,
 3 per unique combination of heat and drought. * species: abbreviation for
 species names, including the first two letters of genus and the first two
 letters of species. ABBA = *Abies balsamea*, ACRU = *Acer rubrum*, ACSA =
 *Acer saccharum*, FRNI = *Fraxinus nigra*, PIRU = *Picea rubens*, PIST =
 *Pinus strobus*, QURU = *Quercus rubra*, THOC = *Thuja occidentalis* *
 treatment: combination of heat treatment (first letter) and drought
 treatment (second letter) * drought: drought treatment. I = irrigated, R =
 repeated, E = extended * heat: heat treatment. A = ambient temperature, M
 = moderate warming, E = extreme warming * r.s: the root-to-shoot biomass
 ratio, where root = below-ground biomass and shoot = all above-ground
 biomass * total: the total biomass (in g), including root, stem, and leaf
 biomass * total.log: the log of the total column (used in total biomass
 models) * r.s.log: the log of the r.s column (used in root-to-shoot
 models) #### File: final_height.csv **Description:** These data contain
 the height of all individuals used in height analyses at the start of
 treatments and at the end of the growing season. ##### Variables *
 ID: unique seedling identifier * chamber: treatment chamber (representing
 on experimental unit and a single application of a heat and drought
 treatment). There are 27 total chambers, 3 per unique combination of heat
 and drought. * species: abbreviation for species names, including the
 first two letters of genus and the first two letters of species. ABBA =
 *Abies balsamea*, ACRU = *Acer rubrum*, ACSA = *Acer saccharum*, FRNI =
 *Fraxinus nigra*, PIRU = *Picea rubens*, PIST = *Pinus strobus*, QURU =
 *Quercus rubra*, THOC = *Thuja occidentalis* * treatment: combination of
 heat treatment (first letter) and drought treatment (second letter) *
 drought: drought treatment. I = irrigated, R = repeated, E = extended *
 heat: heat treatment. A = ambient temperature, M = moderate warming, E =
 extreme warming * SOT: height (in cm) at the start of treatments.
 Measurements were conducted June 26 2024 through July 3 2024. *
 EOS: height (in cm) at the end of the growing season. Measurements were
 conducted September 18 2024 through September 20 2024. * EOS.log: the log
 of the EOS column (used in height models) #### File: final_survival.csv
 **Description:** These data contain the final survival of all tree
 seedlings. ##### Variables * ID: unique seedling identifier * date: date
 of final survival data collection, format yyyy-mm-dd * chamber: treatment
 chamber (representing on experimental unit and a single application of a
 heat and drought treatment). There are 27 total chambers, 3 per unique
 combination of heat and drought. * species: abbreviation for species
 names, including the first two letters of genus and the first two letters
 of species. ABBA = *Abies balsamea*, ACRU = *Acer rubrum*, ACSA = *Acer
 saccharum*, FRNI = *Fraxinus nigra*, PIRU = *Picea rubens*, PIST = *Pinus
 strobus*, QURU = *Quercus rubra*, THOC = *Thuja occidentalis* *
 treatment: combination of heat treatment (first letter) and drought
 treatment (second letter) * drought: drought treatment. I = irrigated, R =
 repeated, E = extended * heat: heat treatment. A = ambient temperature, M
 = moderate warming, E = extreme warming * survival.binom: binomial
 survival data. 0 = dead, 1 = alive * survival: descriptions of
 survival.binom #### File: gmin_lma.csv **Description:** These data contain
 the minimum epidermal conductance (g~min~) and leaf-mass-per-area (LMA)
 for all sampled individuals on August 26 2024. ##### Variables *
 ID: unique seedling identifier * species: abbreviation for species names,
 including the first two letters of genus and the first two letters of
 species. ABBA = *Abies balsamea*, ACRU = *Acer rubrum*, ACSA = *Acer
 saccharum*, FRNI = *Fraxinus nigra*, PIRU = *Picea rubens*, PIST = *Pinus
 strobus*, QURU = *Quercus rubra*, THOC = *Thuja occidentalis* *
 chamber: treatment chamber (representing on experimental unit and a single
 application of a heat and drought treatment). There are 27 total chambers,
 3 per unique combination of heat and drought. * treatment: combination of
 heat treatment (first letter) and drought treatment (second letter) *
 drought: drought treatment. I = irrigated, R = repeated, E = extended *
 heat: heat treatment. A = ambient temperature, M = moderate warming, E =
 extreme warming * gmin: minimum epidermal conductance (mmol m ^-2^ s ^-1^)
 * LMA.m2: leaf-mass-per-area (g m ^-2^) #### File: tlp.csv
 **Description:** These data contain the turgor loss point (TLP) of all
 individuals sampled on August 24 2024. ##### Variables * time: denotes
 whether the measurement was collected in the morning (AM) or evening (PM)
 * ID: unique seedling identifier * species: abbreviation for species
 names, including the first two letters of genus and the first two letters
 of species. ABBA = *Abies balsamea*, ACRU = *Acer rubrum*, ACSA = *Acer
 saccharum*, FRNI = *Fraxinus nigra*, PIRU = *Picea rubens*, PIST = *Pinus
 strobus*, QURU = *Quercus rubra*, THOC = *Thuja occidentalis* * chamber:
 treatment chamber (representing on experimental unit and a single
 application of a heat and drought treatment). There are 27 total chambers,
 3 per unique combination of heat and drought. * treatment: combination of
 heat treatment (first letter) and drought treatment (second letter) *
 drought: drought treatment. I = irrigated, R = repeated, E = extended *
 heat: heat treatment. A = ambient temperature, M = moderate warming, E =
 extreme warming * TLP: turgor loss point (MPa) #### File:
 water_potential.csv **Description:** These data contain the mid-day leaf
 water potential of all individuals sampled at multiple timepoints. #####
 Variables * date: date of data collection, format yyyy-mm-dd * ID: unique
 seedling identifier * species: abbreviation for species names, including
 the first two letters of genus and the first two letters of species. ABBA
 = *Abies balsamea*, ACRU = *Acer rubrum*, ACSA = *Acer saccharum*, FRNI =
 *Fraxinus nigra*, PIRU = *Picea rubens*, PIST = *Pinus strobus*, QURU =
 *Quercus rubra*, THOC = *Thuja occidentalis* * chamber: treatment chamber
 (representing on experimental unit and a single application of a heat and
 drought treatment). There are 27 total chambers, 3 per unique combination
 of heat and drought. * treatment: combination of heat treatment (first
 letter) and drought treatment (second letter) * drought: drought
 treatment. I = irrigated, R = repeated, E = extended * heat: heat
 treatment. A = ambient temperature, M = moderate warming, E = extreme
 warming * WP.c: water potential (MPa) #### File: mean_sm.csv
 **Description:** These data contain the average approximate substrate
 moisture for each treatment combination each day that substrate moisture
 measurements took place and were used to create a Figure 2 of the
 manuscript. Variables * date: date of data collection, format yyyy-mm-dd *
 treatment: combination of heat treatment (first letter) and drought
 treatment (second letter) * drought: drought treatment. I = irrigated, R =
 repeated, E = extended * heat: heat treatment. A = ambient temperature, M
 = moderate warming, E = extreme warming * meanSM: the average approximate
 substrate moisture of all seedlings for which data was collected for a
 given treatment. This was first averaged at the chamber level (9 chambers
 per treatment) and then at the treatment level. * seSM: one standard error
 from the mean, calculate when averaging from chamber to treatment ####
 File: min_sm.csv **Description:** These data contain the minimum
 approximate substrate moisture achieved by each containerized seedling
 throughout the drought treatment period and were used in models of
 substrate moisture. ##### Variables * date: date of data collection,
 format yyyy-mm-dd * ID: unique seedling identifier * species: abbreviation
 for species names, including the first two letters of genus and the first
 two letters of species. ABBA = *Abies balsamea*, ACRU = *Acer rubrum*,
 ACSA = *Acer saccharum*, FRNI = *Fraxinus nigra*, PIRU = *Picea rubens*,
 PIST = *Pinus strobus*, QURU = *Quercus rubra*, THOC = *Thuja
 occidentalis* * chamber: treatment chamber (representing on experimental
 unit and a single application of a heat and drought treatment). There are
 27 total chambers, 3 per unique combination of heat and drought. *
 treatment: combination of heat treatment (first letter) and drought
 treatment (second letter) * drought: drought treatment. I = irrigated, R =
 repeated, E = extended * heat: heat treatment. A = ambient temperature, M
 = moderate warming, E = extreme warming * sm.per: the approximate
 substrate moisture as a percent for a given ID on a given date