DOI: 10.5061/dryad.9zw3r22q5
title: Data and code from: Species interactions amplify functional group responses to elevated CO2 and N enrichment in a 24-year grassland experiment

description: Plant functional groups differ in their response to global changes,
 although species within those groups also vary in such responses. Both
 species and functional group responses to global change are likely
 influenced by species interactions such as inter-specific competition and
 facilitation, which are prevalent in species mixtures but not
 monocultures. As most studies focus on responses of plants growing in
 either monocultures or mixtures, but rarely both, it remains unclear how
 interspecific interactions in diverse ecological communities, especially
 among species in different functional groups, modify functional group
 responses to global changes. To address these issues, we leveraged data
 from a 16-species, 24-year perennial grassland experiment to examine plant
 functional group biomass responses to atmospheric CO2, and N inputs at
 different planted diversity. Functional groups differed in their responses
 to N and CO2 treatments in monocultures. Such differences were amplified
 in mixtures, where N enrichment strongly increased C3 grass success at
 ambient CO2 and C4 grass success at elevated CO2. Legumes declined with N
 enrichment in mixtures at both CO2 levels and increased with elevated CO2
 in the initial years of the experiment. Our results suggest that previous
 studies that considered responses to global changes in monocultures may
 underestimate biomass changes in diverse communities where interspecific
 interactions can amplify responses. Such effects of interspecific
 interactions on responses of functional groups to global change may impact
 community composition over time and consequently influence ecosystem
 functions.
description: From the manuscript: Experiment design: The
 BioCON experiment, which manipulates Biodiversity, N and
 CO<sub>2</sub>, was started in 1997 at Cedar Creek Ecosystem
 Science Reserve (East Bethel, MN, USA, 45°40′N, 93°18′W), a Long-Term
 Ecological Research site. The compositionally neutral full-factorial
 experiment comprised 296 plots that varied in their initial planted
 diversity (1,4, 9 or 16 species), N (ambient or + 4 g m<sup>-2
 </sup>year<sup>-1</sup>) and CO<sub>2</sub>
 (ambient or +180ppm) treatments applied in a split-plot design for the
 CO<sub>2</sub> treatment (Reich, Knops, et al., 2001). The
 diversity gradient was created by experimentally assembling plant
 communities with 1 species, random selection of 4 or 9 species and/or all
 16 species. As 36 of the 9 species plots have since been used for a
 sub-experiment involving temperature and drought treatments, we excluded
 those plots from our analyses leaving 260 plots. The species were chosen
 to represent common or naturalized prairie species in the region and
 spanned four functional groups: C<sub>3</sub> grasses
 (<em>Bromus inermis</em>, <em>Elymus repens
 [</em>formerly <em>Agropyron
 repens</em>], <em>Koeleria macrantha [</em>formerly
 <em>Koeleria cristata</em>], and <em>Poa
 pratensis</em>), C<sub>4</sub> grasses
 (<em>Andropogon gerardii</em>, <em>Bouteloua
 gracilis</em>, <em>Schizachyrium
 scoparium,</em> and <em>Sorghastrum nutans</em>),
 legumes (<em>Amorpha canescens</em>, <em>Lespedeza
 capitata</em>, <em>Lupinus perennis</em>,
 and <em>Petalostemum villosum</em>), and non-legume forbs
 (<em>Achillea millefolium</em>, <em>Anemone
 cylindrica</em>, <em>Asclepias tuberosa</em>,
 and <em>Solidago rigida</em>). Since the species composition
 was randomly chosen for the 4 and 9 species plots, each replicate for
 these two diversity levels differs in species and FG composition. Species
 found in a plot other than those originally planted there were weeded
 annually. Additionally, to maintain the study site in a grassland state,
 the plots were burnt in spring for half of the years between 2000 to 2012
 (Adair et al., 2009) and every fall since 2013. Plant
 biomass Late in each growing season in August in the
 majority of plots in almost all years, aboveground biomass in a pre-marked
 10 x 100 cm strip was clipped and sorted to the species level. The part of
 the plot from which biomass data were collected shifted annually to reduce
 potential influence of clipping on a single part of the plot.
 Species-specific cover data from a constant predetermined and never
 clipped 50 x 100 cm region of the plot were also recorded for every plot
 each year (except for a subset of 4 species plots during 2020 as all
 efforts were scaled down due to the pandemic). Using cover and biomass
 data we then generated species-specific correlations between the two to
 estimate biomass data for all years based on cover data. This step allowed
 us to a) impute biomass values when only cover data were available; and b)
 obtain a more representative estimate of biomass for the plot as cover
 data spanned a larger area of the plot compared to clip-strip biomass
 data.
description: # Data and code from: Species interactions amplify functional group
 responses to elevated CO2 and N enrichment in a 24-year grassland
 experiment
 [https://doi.org/10.5061/dryad.9zw3r22q5](https://doi.org/10.5061/dryad.9zw3r22q5) ## Description of the data and file structure ### Data and code for "Species interactions amplify functional group responses to elevated CO2 and N enrichment in a 24-year grassland experiment" This contains data on species-specific biomass and cover from a long-term biodiversity global change experiment situated at Cedar Creek Ecosyste Science Reserve, Minnesota, USA. The three main treatments are Biodiversity gradient (1, 4, 9 and 16 species), nitrogen treatment (ambient vs +4 g/m2/yr) and CO2 treatment (ambient vs +180 ppm). The experiment was planted in 1997 and data are available from 1997-2021. Data on other aspects of the experiment may be available as part of other papers. More details about the experiment can be found at [https://cedarcreek.umn.edu/research/experiments/e141](https://cedarcreek.umn.edu/research/experiments/e141) ### Files and variables #### File: GCB\_species\_interactions\_FG\_response\_envtdata.csv **Description:** Provides information on environmental data for 24 years of the experiment ##### Variables * year: Calendar year from 1998-2021; i.e., for the 24 years of the experiment * ring: the CO2 treatment is applied at the block level rather than for each plot. There are 6 rings (1-6), 3 with ambient CO2 (rings 2,4 and 6) and 3 with elevated CO2 (rings 1,3 and 5). "ring" identifies the "block" structure * plot: Plot ID that runs from 1 to 371 but not all plots are part of the main biodiversity experiment * ambrain_mayjul: total precipitation in the growing season from May to July (in inches) at the site level. Missing values are noted as NA. * jun_temp: Mean temperature in June (in Fahrenheit) at the site level. Missing values are noted as NA. * mean_temp: Mean temperature in the growing season from May to July (in Fahrenheit) at the site level. Missing values are noted as NA. * init_no3: Initial NO3- at the beginning of the season in mg/kg for each plot x year combination. Missing values are noted as NA. * init_nh4: Initial NH4+ at the beginning of the season in mg/kg for each plot x year combination. Missing values are noted as NA. * net_nmin: Net N mineralization in mg/kg/day for each plot x year combination. Missing values are noted as NA. * pH: measure of soil pH for each plot x year combination. Missing values are noted as NA. #### File: GCB\_species\_interactions\_FG\_response\_plantdata.csv **Description:** Provides information on species-specific biomass, cover and whether a species was planted or not for each plot x year combination. ##### Variables * year: Calendar year from 1998-2021; i.e., for the 24 years of the experiment * ring: the CO2 treatment is applied at the block level rather than for each plot. There are 6 rings (1-6), 3 with ambient CO2 (rings 2,4 and 6) and 3 with elevated CO2 (rings 1,3 and 5). "ring" identifies the "block" structure * plot: Plot ID that runs from 1 to 371 but not all plots are part of the main biodiversity experiment * ctrt: CO2 treatment; Camb= ambient CO2 and Cenrich=elevated CO2 (+180ppm) * ntrt: N treatment; Namb= ambient N and Nenrich= enriched N (+4 g/m2/yr) * sprich: Planted species richness (1,4,9,16 species) * watertrt: Part of an add-on experiment with drought treatment started in 2008; H20amb= ambient water and H2Oneg= 40% reduction in precipitation * temptrt: Part of an add-on experiment with temperature treatment started in 2012; HTamb= ambient temperature and HTelev= elevated temperature (+3 C) * use_for_main: whether to use the plot as a part of the main BioCON experiment; Y= Yes and N= No. Additional subplots were included to test specific hypotheses and not all of those plots are part of the main BioCON experiment because of the randomized nature of the planted species * biomAchmil: biomass of Achillea millefolium as recorded from the moving 10 x 100 cm clipstrip in g/m2. 0 indicates that species was planted but was not recorded in the clipstrip and NA indicates that the species was not planted. * biomAgrrep: biomass of Agropyron repens (now Elymus repens) as recorded from the moving 10 x 100 cm clipstrip in g/m2. 0 indicates that species was planted but was not recorded in the clipstrip and NA indicates that the species was not planted. * biomAmocan: biomass of Amorpha canescens as recorded from the moving 10 x 100 cm clipstrip in g/m2. 0 indicates that species was planted but was not recorded in the clipstrip and NA indicates that the species was not planted. * biomAndger: biomass of Andropogon gerardii as recorded from the moving 10 x 100 cm clipstrip in g/m2. 0 indicates that species was planted but was not recorded in the clipstrip and NA indicates that the species was not planted. * biomAnecyl: biomass of Anemone cylindrica as recorded from the moving 10 x 100 cm clipstrip in g/m2. 0 indicates that species was planted but was not recorded in the clipstrip and NA indicates that the species was not planted. * biomAsctub: biomass of Asclepias tuberosa as recorded from the moving 10 x 100 cm clipstrip in g/m2. 0 indicates that species was planted but was not recorded in the clipstrip and NA indicates that the species was not planted. * biomBougra: biomass of Bouteloua gracilis as recorded from the moving 10 x 100 cm clipstrip in g/m2. 0 indicates that species was planted but was not recorded in the clipstrip and NA indicates that the species was not planted. * biomBroine: biomass of Bromus inermis as recorded from the moving 10 x 100 cm clipstrip in g/m2. 0 indicates that species was planted but was not recorded in the clipstrip and NA indicates that the species was not planted. * biomKoecri: biomass of Koeleria cristata as recorded from the moving 10 x 100 cm clipstrip in g/m2. 0 indicates that species was planted but was not recorded in the clipstrip and NA indicates that the species was not planted. * biomLescap: biomass of Lespedeza capitata as recorded from the moving 10 x 100 cm clipstrip in g/m2. 0 indicates that species was planted but was not recorded in the clipstrip and NA indicates that the species was not planted. * biomLupper: biomass of Lupinus perennis as recorded from the moving 10 x 100 cm clipstrip in g/m2. 0 indicates that species was planted but was not recorded in the clipstrip and NA indicates that the species was not planted. * biomPetvil: biomass of Petalostemum villosum as recorded from the moving 10 x 100 cm clipstrip in g/m2. 0 indicates that species was planted but was not recorded in the clipstrip and NA indicates that the species was not planted. * biomPoapra: biomass of Poa pratensis as recorded from the moving 10 x 100 cm clipstrip in g/m2. 0 indicates that species was planted but was not recorded in the clipstrip and NA indicates that the species was not planted. * biomSchsco: biomass of Schizachyrium scoparium as recorded from the moving 10 x 100 cm clipstrip in g/m2. 0 indicates that species was planted but was not recorded in the clipstrip and NA indicates that the species was not planted. * biomSolrig: biomass of Solidago rigida as recorded from the moving 10 x 100 cm clipstrip in g/m2. 0 indicates that species was planted but was not recorded in the clipstrip and NA indicates that the species was not planted. * biomSornut: biomass of Sorghastrum nutans as recorded from the moving 10 x 100 cm clipstrip in g/m2. 0 indicates that species was planted but was not recorded in the clipstrip and NA indicates that the species was not planted. * biom_totag: Total aboveground biomass in g/m2 measured from the clipstrip (excludes non-planted species that are weeded out multiple times during the growing season) * covAchmil: cover of Achillea millefolium as recorded in a constant 50 x 100 cm area of the plot in %. 0 indicates that species was planted but was not recorded in the cover area and NA indicates that the species was not planted. * covAgrrep: cover of Agropyron repens (now Elymus repens) as recorded in a constant 50 x 100 cm area of the plot in %. 0 indicates that species was planted but was not recorded in the cover area and NA indicates that the species was not planted. * covAmocan: cover of Amorpha canescens as recorded in a constant 50 x 100 cm area of the plot in %. 0 indicates that species was planted but was not recorded in the cover area and NA indicates that the species was not planted. * covAndger: cover of Andropogon gerardii as recorded in a constant 50 x 100 cm area of the plot in %. 0 indicates that species was planted but was not recorded in the cover area and NA indicates that the species was not planted. * covAnecyl: cover of Anemone cylindrica as recorded in a constant 50 x 100 cm area of the plot in %. 0 indicates that species was planted but was not recorded in the cover area and NA indicates that the species was not planted. * covAsctub: cover of Asclepias tuberosa as recorded in a constant 50 x 100 cm area of the plot in %. 0 indicates that species was planted but was not recorded in the cover area and NA indicates that the species was not planted. * covBougra: cover of Bouteloua gracilis as recorded in a constant 50 x 100 cm area of the plot in %. 0 indicates that species was planted but was not recorded in the cover area and NA indicates that the species was not planted. * covBroine: cover of Bromus inermis as recorded in a constant 50 x 100 cm area of the plot in %. 0 indicates that species was planted but was not recorded in the cover area and NA indicates that the species was not planted. * covKoecri: cover of Koeleria cristata as recorded in a constant 50 x 100 cm area of the plot in %. 0 indicates that species was planted but was not recorded in the cover area and NA indicates that the species was not planted. * covLescap: cover of Lespedeza capitata as recorded in a constant 50 x 100 cm area of the plot in %. 0 indicates that species was planted but was not recorded in the cover area and NA indicates that the species was not planted. * covLupper: cover of Lupinus perennis as recorded in a constant 50 x 100 cm area of the plot in %. 0 indicates that species was planted but was not recorded in the cover area and NA indicates that the species was not planted. * covPetvil: cover of Petalostemum villosum as recorded in a constant 50 x 100 cm area of the plot in %. 0 indicates that species was planted but was not recorded in the cover area and NA indicates that the species was not planted. * covPoapra: cover of Poa pratensis as recorded in a constant 50 x 100 cm area of the plot in %. 0 indicates that species was planted but was not recorded in the cover area and NA indicates that the species was not planted. * covSchsco: cover of Schizachyrium scoparium as recorded in a constant 50 x 100 cm area of the plot in %. 0 indicates that species was planted but was not recorded in the cover area and NA indicates that the species was not planted. * covSolrig: cover of Solidago rigida as recorded in a constant 50 x 100 cm area of the plot in %. 0 indicates that species was planted but was not recorded in the cover area and NA indicates that the species was not planted. * covSornut: cover of Sorghastrum nutans as recorded in a constant 50 x 100 cm area of the plot in %. 0 indicates that species was planted but was not recorded in the cover area and NA indicates that the species was not planted. * cov_tot: Total cover of the plot recorded in the 50 x 100 cm area as % * Achmil_planted: Identifies whether Achillea millefolium was planted in the plot or not. 1 indicates planted; NA indicates not planted. * Agrrep_planted: Identifies whether Agropyron repens (now Elymus repens) was planted in the plot or not. 1 indicates planted; NA indicates not planted. * Amocan_planted: Identifies whether Amorpha canescens was planted in the plot or not. 1 indicates planted; NA indicates not planted. * Andger_planted: Identifies whether Andropogon gerardii was planted in the plot or not. 1 indicates planted; NA indicates not planted. * Anecyl_planted: Identifies whether Anemone cylindrica was planted in the plot or not. 1 indicates planted; NA indicates not planted. * Asctub_planted: Identifies whether Asclepias tuberosa was planted in the plot or not. 1 indicates planted; NA indicates not planted. * Bougra_planted: Identifies whether Bouteloua gracilis was planted in the plot or not. 1 indicates planted; NA indicates not planted. * Broine_planted: Identifies whether Bromus inermis was planted in the plot or not. 1 indicates planted; NA indicates not planted. * Koecri_planted: Identifies whether Koeleria cristata was planted in the plot or not. 1 indicates planted; NA indicates not planted. * Lescap_planted: Identifies whether Lespedeza capitata was planted in the plot or not. 1 indicates planted; NA indicates not planted. * Lupper_planted: Identifies whether Lupinus perennis was planted in the plot or not. 1 indicates planted; NA indicates not planted. * Petvil_planted: Identifies whether Petalostemum villosum was planted in the plot or not. 1 indicates planted; NA indicates not planted. * Poapra_planted: Identifies whether Poa pratensis was planted in the plot or not. 1 indicates planted; NA indicates not planted. * Schsco_planted: Identifies whether Schizachyrium scoparium was planted in the plot or not. 1 indicates planted; NA indicates not planted. * Solrig_planted: Identifies whether Solidago rigida was planted in the plot or not. 1 indicates planted; NA indicates not planted. * Sornut_planted: Identifies whether Sorghastrum nutans was planted in the plot or not. 1 indicates planted; NA indicates not planted. ## Code/software GCB_species_interactions_final_code.R provides details on estimating biomass from cover and includes scripts to reproduce all the statistical analyses and figures included in the manuscript. R version 4.3.0 (2023-04-21 ucrt) ## Access information Other publicly accessible locations of the data: * [https://doi.org/10.6073/pasta/c153c4eb2414bb1ec2ab8b07adc17ef2](https://doi.org/10.6073/pasta/c153c4eb2414bb1ec2ab8b07adc17ef2) * [https://doi.org/10.6073/pasta/16126cfed23818206abe3c83bced1ea5](https://doi.org/10.6073/pasta/16126cfed23818206abe3c83bced1ea5) Data was derived from the following sources: * [https://cedarcreek.umn.edu/research/experiments/e141](https://cedarcreek.umn.edu/research/experiments/e141)