Dataset DOI: 10.5061/dryad.0vt4b8hc1

Description of the data and file structure

This repository contains physiological (leaf δ¹³C, nitrogen), phenological, and growth data from three temperate decidouos tree saplings grown in mesocosms under drought, warmer winters, or combined treatments. Saplings were cultivated in monocultures or two-species mixtures. Measurements span two growing seasons (2022–2023), including spring and autumn phenology, summer physiology (June/August), and growth assessments during winter.

Files and variables

File: Autumn_Phenology.txt

Description: This file contains individual-level autumn phenology data for tree saplings grown in an experimental mesocosm setup. Each row represents a single sapling observed in a given year (2022–2023), with variables describing the experimental design (block, plot, compartment), species identity, competition and species composition, drought and warming treatments, and senescence timing. Phenological responses include the day of year (DOY) at 50% and 80% senescence, indicators of premature senescence, and the fraction of premature leaf discoloration. 

Empty cells were replaced with ‘n/a’. Plant losses occurred only rarely due to mortality. Most frequently, the onset of senescence was not recorded because premature discoloration occurred before phenological observations started in September. As a result, 50% senescence could not be assessed in these cases.

Variables

• Block: Experimental mesocosm block (1-3)
• Plot: Plot within block (1-6)
• Compartment: Compartment within Plot (1-4)
• Species: Investigated tree species
• Number: Position of the sapling within the compartment
• ID: Combination of Block, Plot, and Compartment
• ID2: Combination of Block, Plot, Compartment, and Number
• Competition: the competitor species of the compartment
• Composition: the species composition of the compartment
• Drought: drought treatment (yes, no)
• Warming: warming treatment (yes, no)
• Passive warming: passive warming treatment (yes, no)
• Warming2: warming treatment (yes (neighbour=no), no (neighbour=yes), control (individuum and neighbour=no). 
• Senescence50: DOY of 50% senescence
• Senescence_80: DOY of 80% senescence
• Year: Year (2022, 2023)
• ID3: Combination of Block, Plot, Compartment, Number and Year
• Premature Senescence: Premature senescence (yes=1, no=0)
• Type: cultivation method before starting the experiment
• Premature leaf discoloration: Fraction of premature leaf discoloration

File: Meteo.txt

Description: This file contains daily meteorological data recorded during the study period. Each row represents one calendar date and includes atmospheric temperature and vapor pressure deficit (VPD) measured 2 m above ground. Variables include daily mean, minimum, and maximum air temperature (°C) and VPD (kPa), along with corresponding date, month, and year information.

Variables

• Date: Date
• Year: Year
• Month: Month
• mean_AT: mean atmospheric temperature in °C, 2m above ground at a given date
• min_AT: minimum atmospheric temperature in °C, 2m above ground at a given date
• max_AT: maximum atmospheric temperature in °C, 2m above ground at a given date
• mean_VPD: mean VPD in kPa, 2m above ground at a given date
• min_VPD: minimum VPD in kPa,  2m above ground at a given date
• max_VPD: minimum VPD in kPa, 2m above ground at a given date

File: Sapling_Growth.txt

Description: The dataset tracks the growth and experimental treatments of individual saplings across multiple years (2020–2024) in a controlled mesocosm setup. It combines information on sapling identity, experimental conditions, growth measurements, and biomass allocation.

Empty cells were replaced with ‘n/a’. Plant losses occurred only rarely due to mortality. Two saplings were lost after excavation. 

Variables

• Number: Serial number
• Block: Experimental mesocosm block (1-3)
• Plot: Plot within block (1-6)
• Compartment: Compartment within Plot (1-4)
• Species: Investigated tree species
• Number: Position of the sapling within the compartment
• Type: cultivation method before starting the experiment
• ID: Combination of Block, Plot, and Compartment
• ID2: Combination of Block, Plot, Compartment, and Number
• Composition: the species composition of the compartment
• Competition: the competitor species of the compartment
• Drought: drought treatment (yes, no)
• Warming: warming treatment (yes, no)
• ID2: Combination of Block, Plot, Compartment, and Number
• ID3: Combination of species, treatments and number
• Passive warming: passive warming treatment (yes, no)
• Warming2: warming treatment (yes (neighbour=no), no (neighbour=yes), control (individuum and neighbour=no).
• H Winter 20/21: sapling height in winter 20/21(cm)
• D Winter 20/21: sapling diameter in winter 20/21 (mm)
• H Winter 21/22: sapling height in winter 21/22 (cm)
• D Winter 21/22: sapling diameter in winter 21/22 (mm)
• H Winter 22/23: sapling height in winter 22/23 (cm)
• D Winter 22/23: sapling diameter in winter 22/23 (mm)
• H Winter 23/24: sapling height in winter 23/24 (cm)
• D Winter 23/24: sapling diameter in winter 23/24 (mm)
• DI21: diameter increment 2021 (mm)
• DI22: diameter increment 2022 (mm)
• DI23: diameter increment 2023 (mm)
• HI21: height increment 2021 (cm)
• HI22: height increment 2022 (cm)
• HI23: height increment 2023 (cm)
• Total weight: total biomass (g)
• Above-ground weight: biomass of the shoot (g)
• Belowground weight: biomass of the root (g)
• Root/Shoot: root/shoot ratio (-)

File: Spring_Phenology.txt

Description: This file contains individual-level spring phenology data for tree saplings grown in an experimental mesocosm setup. Each row represents a single sapling observed in a given year and includes variables describing the experimental design (block, plot, compartment), species identity, species composition and competition, drought and warming treatments, and cultivation method prior to the experiment. Phenological development is recorded as dates of four spring phenological stages, along with the number of days required to progress from stage 2 to stage 4.

Empty cells were replaced with ‘n/a’. Plant losses occurred only rarely due to mortality. In the phenological assessments, individual stages were occasionally missed. Phenological stages are reported as "Day of the year (DOY)"

Phenological assessments were conducted following the protocol described in Vitasse, Y. (2013) Ontogenic changes rather than difference in temperature cause understory trees to leaf out earlier. New Phytologist, 198(1), 149-155. https://doi.org/10.1111/nph.12130.

Variables

• Block: Experimental mesocosm block (1-3)
• Plot: Plot within block (1-6)
• Compartment: Compartment within Plot (1-4)
• Species: Investigated tree species
• Number: Position of the sapling within the compartment
• ID: Combination of Block, Plot, and Compartment
• ID2: Combination of Block, Plot, Compartment, and Number
• Composition: the species composition of the compartment
• Competition: the competitor species of the compartment
• Drought: drought treatment (yes, no)
• Warming: warming treatment (yes, no)
• Passive warming: passive warming treatment (yes, no)
• Warming2: warming treatment (yes (neighbour=no), no (neighbour=yes), control (individuum and neighbour=no).
• Comments: Comments
• Stage 1: Phenological stage 1 (DOY)
• Stage 2: Phenological stage 2 (DOY)
• Stage 3: Phenological stage 3 (DOY)
• Stage 4: Phenological stage 4 (DOY)
• S2-S4: Days required from spring phenological stage 2 to 4. 
• Year: Year
• Type: cultivation method before starting the experiment

File: Sapling_Physiology.txt

Description: This file contains physiological and stable isotope measurements of tree saplings grown in an experimental mesocosm setup. Each row represents a single sapling sampled during the growing season (June or August) in 2022 or 2023. Variables describe species identity, experimental design and treatments (competition, species composition, drought, warming, and passive warming), cultivation method prior to the experiment, and leaf physiological traits, including carbon and nitrogen stable isotope ratios, elemental concentrations, and C/N ratio.

Variables

• Block: Experimental mesocosm block (1-3)
• ID:  Combination of Block, Plot, Compartment, and Number
• ID2:  Combination of Block, Plot, Compartment, and Number
• Species: Investigated tree species
• Competition: the competitor species of the compartment
• Composition: the species composition of the compartment
• Warming: warming treatment (yes, no)
• Passive.warming: passive warming treatment (yes, no)
• Drought: drought treatment (yes, no)
• Sampling: Season of the sampling (June, August)
• Year: Year (2022, 2023)
• d13C: δ¹³C of the bulk leaf
• % C: Carbon percentage of the bulk leaf
• d15N: δ¹⁵N of the bulk leaf
• % N: Nitrogen percentage of the bulk leaf
• C/N: C/N-ratio of the bulk leaf
• Plot: description how the tree saplings are growing (monoculture, mixture)
• Type: cultivation method before starting the experiment

Code/software

A data editor is sufficient to view the data.