Data from: Volcanic soils alleviate the allelopathic capacity of Empetrum nigrum in degraded tundra ecosystems
Data files
Jul 08, 2025 version files 15.09 KB
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README.md
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Ryde_et_al_2025.zip
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Abstract
Land degradation due to unsustainable land use is of major concern worldwide, and recovery is often slow. A potential mechanism behind slow recovery of degraded ecosystems is the retarding impacts of allelopathic plant species on the establishment of species that might facilitate the recovery process. However, the strength of the retarding impact may depend on soil type. In this study, we investigated the potential role of an abundant, evergreen, and allelopathic dwarf shrub, Empetrum nigrum, in trapping tundra ecosystems in a degraded state in Iceland after centuries of unsustainable land use. We first run a series of bioassays to assess the potential allelopathic legacy effects of the Empetrum-associated volcanic soils (Andosol and Vitrisol) on seed germination and root elongation of the common grass species Festuca richardsonii in comparison with Empetrum-associated non-volcanic Histosol and Podzol soil types. Then we assessed the Empetrum leaf-soil interactions for all soil types using leaves from a degraded site in Iceland. We found no potential allelopathic legacy effects of Empetrum associated with volcanic soils, whereas the non-volcanic soils negatively impacted Festuca root elongation. Empetrum leaves alone affected both seed germination and root elongation. These effects were strongly alleviated by the volcanic soils, but not by the non-volcanic soils. We conclude that abundant allelopathic plant species may significantly contribute to trapping tundra ecosystems in a degraded state, but the strength of this trapping mechanism depends on the soil environment.
Dataset DOI: 10.5061/dryad.tx95x6b8b
Description of the data and file structure
The data files contain recordings of germination and root elongation of the grass species Festuca richardsonii seeds and seedlings, incubated with and without the addition of leaves from the allelopathic dwarf shrub Empetrum nigrum, and different types and particle sizes of Empetrum-associated soil.
Files and variables
Inside the folder Ryde_et_al_2025.zip, there are six data files (.csv) accompanied by six code files (.R) used for statistical analyses. The file names, indicate which research question the data is related to (i.e. Q1 or Q2), which response variable was recorded (i.e. seed germination or seedling root elongation), and which soil particle size the seed or seedlings were incubated with (small or large soil particles). Code files are named similar to the data files they were analyzing.
Meaning of column names and abbreviations within data files:
Block: Designates the experimental block that seeds and seedlings were located in during incubation and is used as random factor for statistical analyses.
Dish: Designates the Petri dish that seedlings were incubated in. Included as random factor when assessing the response variable root elongation.
Soil type: Indicates the different types of Empetrum-associated soil that seeds and seedlings were incubated with. Included as explanatory variable with the levels: A1, A2, H, V, P, and No soil. "No soil" refers to petri dishes to which no soil was added. In datasets where both "Soil type" and "Soil particles" occur, "No soil" is a confounding factor level of these two explanatory variables. Abbreviations: A1, Andosol 1; A2, Andosol 2; H, Histosol; V, Vitrisol; P, Podzol.
Soil particles: Indicates two different fractions of the soils, i.e. small (< 1 mm) and large (> 1 mm, < 2 mm) soil particles. "No soil" refers to petri dishes to which no soil was added. Included as explanatory variable with the levels: Small, Large, and No soil, which is a confounding factor level with the explanatory variable "Soil type".
Leaf addition: Indicates the amount of Empetrum leaves in mg that were added to the petri dishes, which could be either no leaf addition (i.e. 0 mg) or leaf addition (> 0 mg, i.e. 20 mg when assessing seedling root elongation and 130 mg when assessing seed germination). Included as explanatory variable with the levels: no leaf addition and leaf addition.
Germination rate: Recorded seed germination. Used as response variable.
Root length: Recorded seedling root length. Used as response variable.
Description of files:
Ryde_et_al_2025_Q1_Root elongation.csv - Recorded root elongation of seedlings incubated with small and large soil particles from each soil type and no leaf addition.
Ryde_et_al_2025_Q1_Root elongation.R - R code used for statistical analysis of the recorded seedling root elongation, incubated with small and large soil particles from each soil type and no leaf addition.
Ryde_et_al_2025_Q1_Seed germination.csv - Recorded germination of seeds incubated with small and large soil particles from each soil type and no leaf addition.
Ryde_et_al_2025_Q1_Seed germination.R - R code used for statistical analysis of the recorded seed germination, incubated with small and large soil particles from each soil type and no leaf addition.
Ryde_et_al_2025_Q2_Root elongation_Large soil particles.csv - Recorded root elongation of seedlings incubated with large soil particles from each soil type and with and without leaf-addition.
Ryde_et_al_2025_Q2_Root elongation_Large soil particles.R - R code used for statistical analysis of the recorded seedling root elongation, incubated with large soil particles from each soil type and with and without leaf-addition.
Ryde_et_al_2025_Q2_Root elongation_Small soil particles.csv - Recorded root elongation of seedlings incubated with small soil particles from each soil type and with and without leaf-addition.
Ryde_et_al_2025_Q2_Root elongation_Small soil particles.R - R code used for statistical analysis of the recorded seedling root elongation, incubated with small soil particles from each soil type and with and without leaf-addition.
Ryde_et_al_2025_Q2_Seed germination_Large soil particles.csv - Recorded germination of seeds incubated with large soil particles from each soil type and with and without leaf-addition.
Ryde_et_al_2025_Q2_Seed germination_Large soil particles.R - R code used for statistical analysis of the recorded seed germination, incubated with large soil particles from each soil type and with and without leaf-addition.
Ryde_et_al_2025_Q2_Seed germination_Small soil particles.csv - Recorded germination of seeds incubated with small soil particles from each soil type and with and without leaf-addition.
*Ryde_et_al_2025_Q2_Seed germination_Small soil particles.R *- R code used for statistical analysis of the recorded seed germination, incubated with small soil particles from each soil type and with and without leaf-addition.
Code/software
R version 4.3.3 was used for coding. In the R software, the lme4 package was used to establish mixed-effects models, the MASS package was used to do model validation, and the emmeans package was used to do pairwise comparisons.