DOI: 10.5061/dryad.9cnp5hqx5
title: Plant co-occurrence and functional trait data from drylands, along with soil, grazing pressure, and climate data

description: Plant functional traits can influence interaction outcomes between nurse
 and target plants through a “functional trait match”, which occurs when
 the traits of nurse plants ameliorate their environment, and target plants
 possess traits that allow them to benefit from this ameliorated
 environment. We investigated how the traits of putative nurse species
 affect interaction outcomes across global drylands and determined the
 functional match that promotes facilitation. We also investigated how
 grazing pressure and global climatic and edaphic gradients affected this
 trait match. We used a collaborative survey conducted across 29 sites from
 five continents, where we gathered in situ co-occurrences of dominant
 species (‘nurses’) and other vascular plant species, as well as their
 functional traits [plant height and leaf dry matter content (LDMC)].
 Climate, edaphic variables, and grazing pressure were measured in situ or
 extracted from databases. We used a model-building approach to determine
 the effect of dominant plant traits on interaction outcomes, and how the
 functional trait match between nurse and target species is affected by
 environmental variables. Tall dominant plants with conservative leaves
 generally had a greater positive effect on species richness and cover
 beneath their canopies, but these effects were strongly modulated by
 grazing pressure and soil pH. Target plants that were significantly
 associated with dominant plants tended to be shorter and have more
 acquisitive leaves than dominant plants, regardless of environmental
 conditions. However, the difference in height and LDMC between dominant
 plants and negatively associated target plants was strongly affected by
 environmental conditions. Functional traits play a significant role in
 determining interaction outcomes between dryland plants. Facilitation in
 drylands is driven by a conservative-acquisitive trait match, a pattern
 observed regardless of grazing pressure, climate, and soil conditions.
description: # Plant co-occurrence and functional trait data from drylands, along with
 soil and climate data Dataset DOI:
 [10.5061/dryad.9cnp5hqx5](10.5061/dryad.9cnp5hqx5) ## Description of the
 data and file structure This data is linked to the research article titled
 "Plant trait matching occurs in facilitative interactions across
 global drylands". This paper investigates the role of functional
 traits and environmental gradients in determining plant-plant interactions
 in global drylands. Specifically, the paper investigates whether the
 traits of dominant plants (putative nurse plants), along with soil,
 climate, and grazing factors, affect interaction outcomes. Furthermore,
 the paper investigates the trait difference between facilitative pairs of
 dominant and target species (the trait match) and whether the trait match
 changes along environmental gradients.  This data was collected as part of
 the BIODESERT project. Refer to Maestre et al. (2022) for details of the
 sampling design used to collect this data. Maestre, F. T., Eldridge, D.
 J., Gross, N., Le Bagousse-Pinguet, Y., Saiz, H., Gozalo, B., Ochoa, V.,
 & Gaitan, J. J. (2022). The BIODESERT survey: assessing the impacts of
 grazing on the structure and functioning of global drylands. *Web Ecology,
 22*(2), 75-96. doi:10.5194/we-22-75-2022 ### Files and variables **File:
 alltraits.xlsx** **Description:** Trait data of species collected in
 plots. Trait values represent the mean trait value for each specific
 species in each plot, except for height and lateral spread which
 represents the maximum value for each species in each plot. Data has been
 gapfilled with trait data collected from other plots with the same grazing
 pressure. | **Attribute** | **Meaning** | | :------------ |
 :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | ID | Unique ID of the plot. | | site\_ID | Unique ID of the site. | | taxon | Species name | | trait | Trait that was measured. MeanLL = mean leaf length (cm), MeanSLA = mean specific leaf area (cm^2^ /g). MeanLDMC = mean leaf dry matter content (%), MeanLA = mean leaf area (cm^2^), MaxH = maximum plant height (cm), MaxLS = maximum lateral spread (cm^2^). PercentN = elemental concentration of Nitrogen in the leaf (%), PercentC = elemental concentration of Carbon in the leaf (%). | | value | The value of the trait. | **File: Chisq_results_6Feb2024_for_submission.csv** **Description:** Results from χ2 analyses to determine whether species are associated with bare or dominant microsites. | **Attribute** | **Meaning** | | :------------ | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | site\_ID | Unique ID of the site. | | ID | Unique ID of the plot. | | species | Name of target species. | | association | Association of the target species. nurse = associated with dominant microsite; bare = associated with bare microsite; neutral = no significant association to either microsite; too\_rare = occurrence is too low to perform χ2 test. |  **File: nint_nurse_trait_env_data.xlsx** **Description:** Used in the first model building procedure to determine the effect of dominant plant traits and environmental variables on interaction outcomes. Contains the Nint value and dominant species associated with each replicate, as well as the functional traits of the dominant species. Additionally, contains the climate and soil variables associated with each plot. | **Attribute** | **Meaning** | | :--------------------- | :------------------------------------------------------------------------------------------------- | | ID | Unique ID of the plot. | | site\_ID | Unique ID of the site. | | replicate\_no | Number of the replicate. | | nurse\_sp | Name of the dominant species. | | NIntc\_richness | Value of NIntC for the replicate calculated with species richness. | | NIntc\_cover | Value of NIntC for the replicate calculated with vascular cover. | | NIntc\_richness\_binom | NIntC richness transformed to range between 0 and 1 | | NIntc\_cover\_binom | NIntC cover transformed to range between 0 and 1 | | Aridity | Aridity of the plot | | graz | Grazing pressure of the plot. 0 = ungrazed; 1 = low grazing; 2 = medium grazing; 3 = high grazing. | | RASE | Coefficient of variation of precipitation. | | pH | Soil pH measured in bare patches without vegetation. | | AMT | Annual mean temperature, ℃. | | SAC | % mass of soil that consists of sand, collected in bare patches without vegetation. | | nurse\_mean\_H | Mean Height of the dominant species, cm. | | nurse\_meanLDMC | Mean Leaf dry matter content of the dominant species, as a percentage. | | log\_nurse\_meanH | nurse\_mean\_H, log transformed | | log\_nurse\_meanLDMC | nurse\_mean\_LDMC, log transformed | | sin\_lat | The sine of the latitude of the plot | | sin\_long | The sine of the longitude of the plot | **File: trait_difference_data.xlsx** **Description:** Used in the second model building exercise to investigate whether trait matching shapes interaction outcomes and whether this changes along environmental gradients. | **Attribute** | **Meaning** | | :---------------- | :----------------------------------------------------------------------------------------------------------------------- | | site\_ID | Unique ID of the site. | | ID | Unique ID of the plot. | | replicate\_no | Number of the replicate. | | trait | Trait considered. | | trait\_difference | Difference in the trait value between the dominant and target species. (trait value of dominant – trait value of target) | | nurse\_sp | Name of dominant species. | | target | Name of target species. | | association | Association of the target species. nurse = associated with dominant microsite; bare = associated with bare microsite | | Aridity | Aridity of the plot | | graz | Grazing pressure of the plot. 0 = ungrazed; 1 = low grazing; 2 = medium grazing; 3 = high grazing. | | RASE | Coefficient of variation of precipitation. | | pH | Soil pH measured in bare patches without vegetation. | | AMT | Annual mean temperature, ℃. | | SAC | % mass of soil that consists of sand, collected in bare patches without vegetation. | | sin\_lat | The sine of the latitude of the plot | | sin\_long | The sine of the longitude of the plot | #### Code/software **File: 1._PCA.R** Description: Script to perform principal component analysis of the trait data in order to reveal the two main axes of trait variation. The dataset associated with this script is alltraits.xlsx **File: 2._model_selection_nint_nurse_traits.R** Description: Script to perform model selection to determine the drivers of interaction outcomes. The data associated with this script is nint_nurse_trait_env_data.xlsx This model selection procedure uses multithreading and takes 96 hours to run. **File: 3._Trait_difference_analysis.R** **Description:** Script to perform model selection to determine the drivers of the difference in traits between dominant and target species. The data associated with this script is trait_difference_data.xlsx This model selection procedure takes 15 minutes to run. **File: 4._Graphs_and_figures.R** Description: Script wherein the graphs and figures shown in the main text were created. All scripts were created in R4.4.2. R and R studio are required to run these scripts. All required libraries are loaded at the start of each script.  ## Access information Other publicly accessible locations of the data: * none Data was derived from the following sources: * This data represents a processed subset of the BIODESERT dataset