Plant functional traits and species mixtures drive extensive green roof community performance at the establishment stage
Data files
Jun 03, 2026 version files 102.88 KB
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Data_(Green_roof_data).xlsx
97.84 KB
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README.md
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Abstract
Green roofs, an important nature-based solutions approach, enhance urban infrastructure by providing habitat for diverse plant species, which are known to improve climate resilience through temperature regulation and carbon assimilation. However, the mechanisms by which plant interactions affect ecosystem service delivery of green roof environments have not been widely explored.
In this study, we evaluated the performance of six native plant species grown in monoculture, all combined in mixture, and combined in mixture with the addition of a seventh species, Sedum spurium, a commonly used succulent on extensive green roofs (EGRs). EGRs are characterised by shallow, inorganic substrates and are more widely installed due to their lightweight design and lower cost. We quantify plant height, leaf area (LA), specific leaf area (SLA), and leaf dry matter content (LDMC), along with plant cover, and evaluate how these traits affect EGR temperature and carbon assimilation.
Our findings indicate trait responses to mixture conditions through phenotypic plasticity in resource acquisition and allocation, with SLA and plant height increasing and LDMC decreasing in mixtures compared to monocultures. Mixed-species communities outperformed single-species ones in terms of plant cover and temperature reduction. Increased plant cover was driven largely by a dominant species, Achillea millefolium, consistent with a selection effect. In contrast, lower substrate temperatures, likely arising from trait differences among species, point to a complementarity effect. Mixtures with Sedum resulted in lower plant cover and higher substrate temperatures compared to mixtures without it, likely driven by Sedum's conservative functional strategy, which limited canopy development and evapotranspiration under irrigated establishment conditions.
Practical implication. This study contributes to the growing body of evidence suggesting that mixed-species assemblages can outperform monocultures in EGRs, with implications for functionally diverse green roof design.
Dataset DOI: 10.5061/dryad.v15dv42c0
Description of the data and file structure
This dataset accompanies the manuscript examining how species composition and functional traits drive plant community performance on extensive green roofs (EGRs). The Excel workbook contains 8 sheets covering leaf functional traits, microclimate temperatures, plant cover, height, carbon assimilation, and three indices of species interaction (RNE, lnRR, RII). The experiment was structured in 6 replicate blocks, with species grown in monoculture, mixture with Sedum, or mixture without Sedum.
Files and variables
File: Data_(Green_roof_data).xlsx
Description: Plants were grown under three treatment conditions across 6 replicate blocks (Plot IDs 1–6). Each species × block combination is assigned a unique Full ID. Three interaction indices (Sheets 6–8) quantify the response of each species relative to its monoculture performance; positive and negative values reflect facilitation and competition, respectively. Full calculation formulas are provided in the Methods section of the manuscript.
Excel file: Sheet description
1. Functional Traits
Leaf-level functional traits measured from sampled individuals:
- Species: Species name.
- Treatment: Growing condition — Monoculture, Mixture with Sedum, or Mixture without Sedum.
- Site ID: Block (replicate) number (1–6).
- Full ID: Unique identifier for each species × block combination.
- Fresh weight: Fresh mass of a sampled leaf (g).
- Dry weight: Dry mass of the leaf after drying at 60°C for 72 hours (g).
- LA: Leaf area measured with ImageJ from scans taken with an Epson Perfection V39 scanner (cm²).
- LDMC: Leaf dry matter content, calculated as (dry weight × 1000) / fresh weight (mg/g).
- SLA: Specific leaf area, calculated as LA / dry weight (cm²/g).
2. Temperature
Plot-level temperature recorded by iButton dataloggers at 15-minute intervals.
- Species: Species composition in the plot.
- Plot ID: Block (replicate) number (1–6).
- Temperature_avg: Mean temperature throughout the day (°C).
- SD_avg: Standard deviation of temperature across the day (°C).
- Max_temperature: Maximum daily temperature recorded (°C).
3. Plant Cover
Spatial cover of each species measured at the plot level.
- Species: Species name.
- Treatment: Growing condition — Monoculture, Mixture with Sedum, or Mixture without Sedum.
- Site ID: Block (replicate) number (1–6).
- Full ID: Unique identifier for each species × block combination.
- Plant_cover: Occupied area of the plant at the plot level (cm²).
- Percentage cover: Plant cover as a percentage of total plot area (%).
4. Plant Height
Height of selected individuals within each plot.
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Species: Species name.
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Treatment: Growing condition — Monoculture, Mixture with Sedum, or Mixture without Sedum.
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Site ID: Block (replicate) number (1–6).
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Full ID: Unique identifier for each species × block combination.
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Height: Height of the selected individual (cm).
5. Carbon Assimilation
Photosynthetic carbon assimilation measured with a LI-COR 6400 gas exchange system.
- Species: Species name.
- Treatment: Growing condition — Monoculture, Mixture with Sedum, or Mixture without Sedum.
- Site ID: Block (replicate) number (1–6).
- Full ID: Unique identifier for each species × block combination.
- Assimilation_rate: Net carbon assimilation rate (µmol CO₂ m⁻² s⁻¹).
6. RNE — Relative Neighbor Effect
Species-level index quantifying the effect of neighbors on individual performance relative to monoculture. Positive values indicate facilitation; negative values indicate competition. See Methods for full formula.
7. lnRR — Log Response Ratio
Natural log of the ratio of species performance in mixture versus monoculture. Values above zero indicate a positive mixture effect; values below zero indicate a negative effect. See Methods for full formula.
8. RII — Relative Interaction Intensity
Bounded index measuring the direction and magnitude of species interactions relative to monoculture performance. See Methods for full formula.
Notes
- All interaction indices (Sheets 6–8) are reported at the species level, representing responses relative to monoculture performance within the same block.
- Full calculation formulas and interpretation guidance for Sheets 6–8 are provided in the Methods section of the manuscript.
Access information
Other publicly accessible locations of the data:
- N/A
Data was derived from the following sources:
- Data were derived from the original field and experimental data collected by the authors.