What we measure matters: Trait choice shapes inferences about grassland functional diversity under altered precipitation
Data files
Sep 30, 2026 version files 415.80 KB
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Above_Ground.csv
18.29 KB
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All_9.csv
28.41 KB
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Below_Ground.csv
18.15 KB
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Cover.csv
279.98 KB
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Economic_Spectrum.csv
17.94 KB
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Mechanistic.csv
18.04 KB
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Popular.csv
18.07 KB
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README.md
9.68 KB
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Species_Trait_Values.csv
7.24 KB
Abstract
This dataset contains community composition and functional trait data from a four-year rainfall manipulation experiment (extreme drought, irrigation, ambient conditions) in a semi-arid grassland near Boulder, Colorado, USA. It includes nine leaf, root, and whole-plant traits grouped into six trait subsets, community-weighted means, four functional diversity indices (richness, evenness, divergence, dispersion), species abundance data, and temporal biomass stability across treatments. Data are provided as CSV files with metadata describing variables, units, and experimental design.
Reuse potential includes reanalysis of how trait and metric selection influence ecological inference, comparison with other global change experiments, and meta-analyses of functional diversity. Data are released under a CC0 waiver with no restrictions on reuse; no personally identifiable information is included, and no ethical or permitting restrictions apply. Users are asked to cite the associated publication and dataset DOI in derived work.
Description of the data and file structure
Data were collected from a four-year rainfall manipulation experiment established in a semi-arid grassland near Boulder, Colorado, USA. The experiment applied three precipitation treatments - extreme drought, irrigation, and ambient conditions - across replicated plots to quantify community responses to altered water availability. We measured nine leaf, root, and whole-plant traits for all species present, grouped into six trait subsets based on trait-based literature. Using community-weighted means and four functional diversity indices (richness, evenness, divergence, dispersion), we assessed drought and irrigation effects on community composition and temporal biomass stability, aiming to evaluate how methodological decisions in trait selection influence ecological inference.
Sampling was conducted from 2018 to 2022. Each trait-subset file (All_9, Above_Ground, Below_Ground, Economic_Spectrum, Mechanistic, Popular) contains one row per plot per year, with community-weighted mean (CWM) trait values and functional diversity indices calculated for that plot-year observation.
Files and variables
File: Above_Ground.csv
Description: Community-weighted means and functional diversity indices for the above-ground trait subset (leaf traits plus height). One row per plot per year.
Variables:
FRic: Functional richness index (unitless)FEve: Functional evenness index (unitless)FDiv: Functional divergence index (unitless)FDis: Functional dispersion index (unitless)CWM.SLA: Community-weighted mean specific leaf area (m² kg⁻¹)CWM.LDMC: Community-weighted mean leaf dry matter content (mg g⁻¹)CWM.H: Community-weighted mean plant height (cm)CWM.RGR: Community-weighted mean relative growth rate (g g⁻¹ day⁻¹)block: Integer. Experimental block identifierplot: Integer. Unique plot identifier within the experimentyear: Integer. Calendar year of sampling (2018–2022)rain_trt: Categorical. Precipitation treatment: "C" = ambient, "D" = drought, "W" = irrigation
File: Cover.csv
Description: Per-species cover/area measurements used to calculate community-weighted means. One row per species per plot per year.
Variables:
Species Code: Categorical. Species codes used during data collectionspecies: Categorical. Speciesgenus: Categorical. genusblock: Integer. Experimental block identifierplot: Integer. Unique plot identifier within the experimentyear: Integer. Calendar year of sampling (2018–2022)Rain Treatment: Categorical. Precipitation treatment: ambient, drought, irrigationTotal Cover: Numeric. Cover area of the species in the plot (m²)
File: All_9.csv
Description: Community-weighted means and functional diversity indices for all nine traits combined. One row per plot per year.
Variables:
FRic: Functional richness index (unitless)FEve: Functional evenness index (unitless)FDiv: Functional divergence index (unitless)FDis: Functional dispersion index (unitless)CWM.SLA: Community-weighted mean specific leaf area (m² kg⁻¹)CWM.LDMC: Community-weighted mean leaf dry matter content (mg g⁻¹)CWM.RDMC: Community-weighted mean root dry matter content (mg g⁻¹)CWM.SRL: Community-weighted mean specific root length (m g⁻¹)CWM.RD: Community-weighted mean root diameter (mm)CWM.RMR: Community-weighted mean root mass ratio (unitless proportion)CWM.H: Community-weighted mean plant height (cm)CWM.RGR: Community-weighted mean relative growth rate (g g⁻¹ day⁻¹)CWM.RL: Community-weighted mean root length (cm)block: Integer. Experimental block identifierplot: Integer. Unique plot identifier within the experimentyear: Integer. Calendar year of sampling (2018–2022)rain_trt: Categorical. Precipitation treatment: "C" = ambient, "D" = drought, "W" = irrigation
File: Below_Ground.csv
Description: Community-weighted means and functional diversity indices for the below-ground trait subset (root traits). One row per plot per year.
Variables:
FRic: Functional richness index (unitless)FEve: Functional evenness index (unitless)FDiv: Functional divergence index (unitless)FDis: Functional dispersion index (unitless)CWM.RDMC: Community-weighted mean root dry matter content (mg g⁻¹)CWM.SRL: Community-weighted mean specific root length (m g⁻¹)CWM.RD: Community-weighted mean root diameter (mm)CWM.RMR: Community-weighted mean root mass ratio (unitless proportion)CWM.RL: Community-weighted mean root length (cm)block: Integer. Experimental block identifierplot: Integer. Unique plot identifier within the experimentyear: Integer. Calendar year of sampling (2018–2022)rain_trt: Categorical. Precipitation treatment: "C" = ambient, "D" = drought, "W" = irrigation
File: Economic_Spectrum.csv
Description: Community-weighted means and functional diversity indices for the economic spectrum trait subset (leaf and root economics traits). One row per plot per year.
Variables:
FRic: Functional richness index (unitless)FEve: Functional evenness index (unitless)FDiv: Functional divergence index (unitless)FDis: Functional dispersion index (unitless)CWM.SLA: Community-weighted mean specific leaf area (m² kg⁻¹)CWM.LDMC: Community-weighted mean leaf dry matter content (mg g⁻¹)CWM.RDMC: Community-weighted mean root dry matter content (mg g⁻¹)CWM.SRL: Community-weighted mean specific root length (m g⁻¹)block: Integer. Experimental block identifierplot: Integer. Unique plot identifier within the experimentyear: Integer. Calendar year of sampling (2018–2022)rain_trt: Categorical. Precipitation treatment: "C" = ambient, "D" = drought, "W" = irrigation
File: Mechanistic.csv
Description: Community-weighted means and functional diversity indices for the mechanistic trait subset. One row per plot per year.
Variables:
FRic: Functional richness index (unitless)FEve: Functional evenness index (unitless)FDiv: Functional divergence index (unitless)FDis: Functional dispersion index (unitless)CWM.SLA: Community-weighted mean specific leaf area (m² kg⁻¹)CWM.LDMC: Community-weighted mean leaf dry matter content (mg g⁻¹)CWM.SRL: Community-weighted mean specific root length (m g⁻¹)CWM.RD: Community-weighted mean root diameter (mm)block: Integer. Experimental block identifierplot: Integer. Unique plot identifier within the experimentyear: Integer. Calendar year of sampling (2018–2022)rain_trt: Categorical. Precipitation treatment: "C" = ambient, "D" = drought, "W" = irrigation
File: Popular.csv
Description: Community-weighted means and functional diversity indices for the popular trait subset. One row per plot per year.
Variables:
FRic: Functional richness index (unitless)FEve: Functional evenness index (unitless)FDiv: Functional divergence index (unitless)FDis: Functional dispersion index (unitless)CWM.SLA: Community-weighted mean specific leaf area (m² kg⁻¹)CWM.LDMC: Community-weighted mean leaf dry matter content (mg g⁻¹)CWM.RDMC: Community-weighted mean root dry matter content (mg g⁻¹)CWM.H: Community-weighted mean plant height (cm)block: Integer. Experimental block identifierplot: Integer. Unique plot identifier within the experimentyear: Integer. Calendar year of sampling (2018–2022)rain_trt: Categorical. Precipitation treatment: "C" = ambient, "D" = drought, "W" = irrigation
File: Species_Trait_Values.csv
Description: Species-level trait values used to calculate community-weighted means and functional diversity indices. One row per species. Trait values represent the species-level values used in the analyses.
Variables:
species: Categorical. Species code/nameSLA: Specific leaf area (m² kg⁻¹)LDMC: Leaf dry matter content (mg g⁻¹)RDMC: Root dry matter content (mg g⁻¹)SRL: Specific root length (m g⁻¹)RD: Root diameter (mm)RMR: Root mass ratio (unitless proportion)H: Plant height (cm)RGR: Relative growth rate (g g⁻¹ day⁻¹)RL: Root length (cm)
Trait definitions
- SLA — Specific leaf area: The ratio of leaf area to leaf dry mass (Li et al., 2005).
- LDMC — Leaf dry matter content: The ratio of leaf dry mass to fresh mass (Vaieretti et al., 2007).
- RDMC — Root dry matter content: Dry weight divided by fresh weight (De Vries et al., 2016).
- SRL — Specific root length: Root length divided by root dry mass (Kramer-Walter et al., 2016).
- RD — Root diameter: Average diameter across the length of subsampled fine roots (Larson, 2021).
- RMR — Relative investment of resources belowground: Ratio of total root dry mass to whole plant dry mass (Martin & Hine, 2008; Larson, 2021).
- H — Height: Vertical distance from the soil base to the tallest photosynthetic tissue, standardized by the number of growing days to account for slight differences in final plant age (Larson, 2021).
- RGR — Relative growth rate: Relative rate of biomass accumulation over time (g g⁻¹ day⁻¹).
- RL — Root length: Root length measured for the sampled plant (cm).
Code/software
R (version 2024.04.2+764)