Anna C Knight Sean L Hoy-Skubik David L Hoover Alix A Pfennigwerth Michael C Duniway 20260416 tabular data Flagstaff, AZ U.S. Geological Survey ORCIDs: Knight, Anna C, 0000-0002-9455-2855 Hoy-Skubik, Sean L, 0000-0002-9157-0126 Hoover, David L, 0000-0002-9326-9791 Pfennigwerth, Alix A, 0000-0001-5102-7324 Duniway, Michael C, 0000-0002-9643-2785 https://doi.org/10.5066/P97GVNBG Sean L. Hoy-Skubik David L. Hoover Alix A. Pfennigwerth Anna C. Knight Michael C. Duniway 2026 journal manuscript Springer Nature Oecologia These data were compiled to investigate competitive interactions between Pleurphis jamesii and other herbaceous plants in a semiarid grassland community. The objectives of our study were to determine whether selective mortality of either C3 or C4 herbaceous plants led to changes in (1) soil moisture during the growing season, (2) water use by Pleuraphis jamesii during the growing season, and (3) Pleuraphis jamesii biomass at the end of the growing season. These data represent the soil moisture; Pleuraphis jamesii physiology, phenology, and growth; and plant community composition before and after selective mortality treatments were implemented. These data were collected in 2019 in the Indian Creek Special Recreation Management Area of Bears Ears National Monument, Utah, USA. The data were measured as part of an experiment examining whether selective mortality of either C3 or C4 herbaceous plants leads to competitive release of Pleuraphis jamesii, a dominant C4 perennial grass species on the Colorado Plateau. We selected 18 focal Pleuraphis jamesii individuals and assigned them to one of three treatments: C3 grass and forb removal with herbicide, C4 grass removal with herbicide, or control (no plant removal). We measured a suite of variables intended to characterize plant water availability, plant water stress, and plant growth in response to the three treatments. Weather data for the experimental site during the time of this study were reported by Grote et al. (2023, EDGUT_Wx station). These data were collected from 1 May 2019 to 6 November 2019 by U.S. Geological Survey scientists and technicians from the Southwest Biological Science Center - Moab, UT, Research Station. These data can be used to understand the effects of plant community changes on individuals in semiarid grasslands, particularly in the context of regional aridification. The purpose of these data are to investigate competitive release mechanisms, especially those related to competition for water, affecting Pleuraphis jamesii, a dominant C4 perennial grass species. Pleuraphis jamesii has been observed to increase growth concurrent with drought-induced selective mortality of dominant C3 perennial grasses (Hoover et al. 2021). These data were created to measure the responses of Pleuraphis jamesii individuals to selective mortality of nearby plant functional types and elucidate the mechanisms behind those responses. Future researchers can use these data to explore ecosystem and vegetation dynamics in semiarid grasslands through mechanisms such as competitive release. These data characterize the results of a plant competition experiment in a semiarid grassland on the Colorado Plateau, UT, USA, in which plants were selectively removed from the area around a focal dominant C4 perennial grass individual based on growth habit and photosynthetic pathway. The data characterized the soil moisture, plant ecophysiology, phenology, biomass, and plant community within the experimental plots. These data may be used for investigating competitive release mechanisms, particularly those related to water use, on individual plants. The estimated biomass data are based on morphological measurements and allometric equations. Due to these methods, they likely have greater error than the final biomass that was measured directly after destructive harvesting. These data represent results during a single growing season in a region with high interannual variability in precipitation. They do not capture the full range of growing conditions that this ecological community may experience across multiple years. Although shrubs are present in this grassland system, we deliberately selected plot locations to avoid shrubs to keep the focus of this study on herbaceous plant functional types. We chose a plot size of 1-meter radius around the focal individual based on the rooting characteristics of Pleuraphis jamesii. However, because we did not trench around the plots, the data may reflect some effects of roots crossing the plot boundaries. Data users should read the entire metadata record, to have a complete understanding of how these data were created. The data are specific to the uses identified above, and any other use of these data would be inappropriate. See 'Distribution liability' statements for more information. 20190501 20191106 ground condition Complete None planned -109.721159 -109.718343 38.176681 38.173330 ISO 19115 Topic Category biota USGS Thesaurus biology carbon carbon cycling community ecology ecological competition droughts field experiments field inventory and monitoring field sampling grassland ecosystems nitrogen phenology plants (organisms) soil resources terrestrial ecosystems USGS Metadata Identifier USGS:642aff8dd34ee8d4add03c91 USGS information products data release None aridification biomass C3 herbaceous plants C4 herbaceous plants carbon 13 carbon isotopes competitive release delta 13C dryland ecosystems experimental design experimental site greenness ground cover herbicide treatment leaf water potential measurement nitrogen isotopes plant growth plant water availability plant water stress Pleuraphis jamesii selective mortality soil volumetric water content treatments Vienna Pee Dee Belemnite Geographic Names Information System (GNIS) Colorado Plateau San Juan County Utah None Bears Ears National Monument Canyonlands National Park Indian Creek Special Recreation Management Area Needles District southeastern Utah none None. Users are advised to read the dataset's metadata thoroughly to understand appropriate use and data limitations. It is requested that the suggested citation for this USGS data release be included in any publications that reference or utilize these data. Michael C Duniway U.S. Geological Survey, Southwest Region Research Ecologist mailing address

2290 S West Resource Blvd

Moab UT 84532 US (435) 210-2831 mduniway@usgs.gov This work was supported by the U.S. Geological Survey Ecosystems Mission Area. We are grateful to Emily Brook, Jessica Mikenas, Ed Grote, and Kelli Quinn for assistance and expertise in implementing this project. Ed Grote Michael C Duniway Sasha C Reed David L Hoover Erika L Geiger Jayne Belnap 2023 tabular digital data Flagstaff, AZ U.S. Geological Survey https://doi.org/10.5066/P9B4SUIY David L. Hoover Alix A. Pfennigwerth Michael C. Duniway 2021 publication British Ecological Society (online) Journal of Ecology https://doi.org/10.1111/1365-2745.13681 No formal attribute accuracy tests were conducted No formal logical accuracy tests were conducted Data set is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details. No formal positional accuracy tests were conducted No formal positional accuracy tests were conducted General Processing Step: Volumetric water content data were recorded using Campbell Scientific data loggers, and data were transmitted via telecommunications to storage servers at the U.S. Geological Survey Southwest Biological Science Center office in Moab, UT. Plant tissue samples for carbon isotope and final biomass measurements were stored in paper envelopes or bags labeled by sampling date, plot, treatment, block, plant species, and field staff names. All other data were recorded on paper data sheets at each experimental plot. USGS staff entered the data on paper data sheets and sample bags/envelopes into Excel spreadsheets on office computers at the U.S. Geological Survey Southwest Biological Science Center office in Moab, UT. Each plant tissue sample was assigned unique identification codes for sample tracking. Samples were stored at the U.S. Geological Survey Southwest Biological Science Center office in Moab, UT, until after manuscript publication was complete. 2022 Development of the Biomass_Estimated_Data table: The data in this table were measured by U.S. Geological Survey field staff and calculated using geometric and allometric equations. The first step was measuring morphological characteristics of the focal Pleuraphis jamesii individual. These measurements were taken by clump (a clump was defined as a bunch of culms separated from other Pleuraphis jamesii culms by at least 3 centimeters (cm) that was at least 50% rooted within the plot area). For each clump, the following measurements were taken: (1) average height of vegetative (not reproductive) tissue to the nearest 0.5 cm; (2) length to the nearest 0.5 cm; (3) width to the nearest 0.5 cm; (4) number of culms; (5) number of green leaves; (6) number of green inflorescences; and (7) basal circumference. Clump volume was calculated using the following set of equations: (a) basal area = (basal circumference^2)/4*pi, (b) top area = pi*length*width, and (c) clump volume = (height/3)*(basal area + top area - sqrt(basal area*top area)). Volume (Vol_cm3_sum) was calculated as the sum of the volume of all the clumps. Number of culms (N_culms_sum), number of inflorescences (N_inflor_sum), and number of leaves (N_leaves_sum) were calculated as the sum of the culm, inflorescence, and leaf counts respectively for all clumps in a plot. Estimated biomass (Biomass_g_est) was calculated from volume, number of leaves, and number of inflorescences using allometric linear equations for spring and fall Pleuraphis jamesii biomass from Hoover et al. (2021). Data were recorded on data sheets and input into an EXCEL workbook on an office computer at the Southwest Biological Science Center - Moab, UT, Research Station. Data processing was completed in 2019. 2019 Development of the Biomass_Weighed_Data table: Data were collected from focal Pleuraphis jamesii individuals by U.S. Geological Survey field staff using destructive harvesting techniques. All green above-ground biomass for each individual was harvested, dried for 48 hours at 60 degrees C, and weighed to the nearest 0.01 g. Weights of tissue samples collected earlier for isotope analysis were added to obtain the final biomass weight. Data were recorded on data sheets and input into an EXCEL workbook on an office computer at the Southwest Biological Science Center - Moab, UT, Research Station. 2019 Development of the Carbon_Isotopes_Data table: Tissue samples were collected from focal Pleuraphis jamesii individuals by U.S. Geological Survey field staff on 8/23/2019 and dried for 48 hours at 60 degrees C, then weighed to the nearest 0.01 g. Dried samples were sent to the Cornell Isotope Laboratory for isotope analysis, where they were assessed using a Thermo Delta V isotope ratio mass spectrometer interfaced to a NC2500 elemental analyzer in September 2019. Data were recorded on data sheets and input into an EXCEL workbook on an office computer at the Southwest Biological Science Center - Moab, UT, Research Station. 2019 Development of the Leaf_Water_Potential_Data table: Data were collected by U.S. Geological Survey field staff before dawn over a period of six days by measuring one cut leaf from each focal Pleuraphis jamesii individual in a pressure chamber with a digital pressure gauge (Model 600D, PMS Instruments Co., Albany, NY, USA; accuracy 0.001 MPa). Data were recorded on data sheets and input into an EXCEL workbook on an office computer at the Southwest Biological Science Center - Moab, UT, Research Station. 2019 Development of the Phenology_Data table: Data were collected on focal Pleuraphis jamesii individuals by U.S. Geological Survey field staff every two weeks using visual estimates. Data were recorded on data sheets and input into an EXCEL workbook on an office computer at the Southwest Biological Science Center - Moab, UT, Research Station. 2019 Development of the Plant_Ground_Cover_Data table: Cover values in this table were measured by U.S. Geological Survey field staff via ocular estimates of cover in each of four quarters (50 cm2) of the plot. The cover values for all four quarters were averaged to obtain the total plot cover, reported here in the Cover attribute. Data were recorded on data sheets and input into an EXCEL workbook on an office computer at the Southwest Biological Science Center - Moab, UT, Research Station. 2019 Development of the Plot_Data table: This data table was created based on the experimental design for the project. Three different experimental treatments: C3 grass and forb removal (C3_forb_removal), C4 grass removal (C4_removal), and control (no removal) during the growing season of 2019 (3 treatments x 6 blocks, N = 18 plots). 2019 Development of the Volumetric_Water_Content_Data table: Data were collected using soil moisture and temperature sensors (30 cm, CS650, Campbell Scientific, Logan, UT, USA) inserted at a 45 degree angle in the center of each plot from 5 to 25 cm depth. Data were recorded at hourly intervals and then summarized to a mean daily value. Data were recorded on data sheets and input into an EXCEL workbook on an office computer at the Southwest Biological Science Center - Moab, UT, Research Station. 2022 Data Quality Assessment and Quality Control (QAQC): Plots were selected within a fenced study area in the Indian Creek Special Recreation Management Area of Bears Ears National Monument, UT, USA (38.19’ N, 109.75’ W; 1505 m elevation). The plant community is a native perennial grassland with scattered shrubs and forbs. The site has deep loamy fine sand soils and was lightly winter grazed by cattle prior to 2015. The site has a semiarid climate with mean annual precipitation of 221 mm, mean winter low temperature of -6.5 C, and mean summer high temperature of 32.7 C. Monthly mean precipitation values are relatively equal throughout the year, except for June, which receives little to no precipitation most years. Plots were defined as the area within a one-meter radius of each of 18 focal Pleuraphis jamesii individuals. Focal individuals were selected based on lack of shrubs within the plots, relatively similar biomass to one another, and relatively similar surrounding plant community cover and composition within the plots. An individual was defined as all Pleuraphis jamesii biomass within a 20 cm radius of the plot center. Six blocks were randomly assigned based on location, with three focal individuals per block. Individuals were randomly assigned to one of the three treatments (C3 grass and forb removal with herbicide, C4 grass removal with herbicide, or control/no plant removal) such that each treatment was applied to one individual in each block. Plot selection was completed in the fall of 2018 and herbicide treatments were applied on 5/29/2019. Data processing was completed in 2019. Quality assurance (QA): Data were collected in the field following pre-established protocols. Measurements were taken by experienced field technicians who were trained on the specific protocols prior to site visits. Data recorded in the field were transcribed on paper data sheets designed for the specific project and protocols. Data sheets were reviewed for completeness at the end of each sampling visit. QA was completed after the last field visit in 2019. Quality Control: Volumetric water content data on the USGS servers were checked weekly by USGS scientists to assess sensor and data transmission functionality. USGS staff entered data from paper data sheets and sample bags and envelopes into Excel spreadsheets and reviewed completed spreadsheets for consistency and accuracy. All figures and results tables produced for publication from these data were reviewed by all coauthors. QC was completed in 2020. 2020 Finalize Data for Dissemination: Data sent to the Southwest Biological Science Center Data Steward for dissemination and preservation per USGS Data Management Policies SM 502.6, SM 502.7, SM 502.8 and SM 502.9 (1 October 2016). 2026 Biomass_Estimated_Data.csv This data table represents estimated plant growth responses to selective mortality treatments in the surrounding plant community. The purpose of this data table is to characterize the biomass of each focal Pleuraphis jamesii individual. Data were collected using nondestructive sampling techniques, by measuring morphological characteristics and applying allometric equations to estimate biomass from morphology. Data were collected twice, at the beginning and end of the growing season. Producer defined Plot This attribute in the data table represents a unique plot identifier Producer defined 911 963 integer number Date This attribute in the data table represents the date of morphology measurements Producer defined 5/22/2019 9/11/2019 date: mm/dd/yyyy Season This attribute in the data table represents the season that the biomass measurement for the focal Pleuraphis jamesii individual was made. Producer defined All focal individuals were sampled once in the spring and once in the fall. Vol_cm3_sum This attribute in the data table represents the volume of focal Pleuraphis jamesii individual, calculated from length, width, and height measurements. Producer defined 71.4371986333776 2452.14900500911 cubic centimeters N_culms_sum This attribute in the data table represents the total number of culms for the focal Pleuraphis jamesii individual. Producer defined 3 49 count N_inflor_sum This attribute in the data table represents the total number of inflorescences for the focal Pleuraphis jamesii individual. Producer defined 0 17 count N_leaves_sum This attribute in the data table represents the total number of leaves for the focal Pleuraphis jamesii individual. Producer defined 14 147 count Biomass_g_est This attribute in the data table represents the estimated biomass of the focal Pleuraphis jamesii individual based on morphological measurements and allometric equations. Producer defined 0.273631974931708 3.52421731141755 grams Biomass_Weighed_Data.csv This data table represents plant growth at the end of the growing season following selective mortality treatments in the surrounding plant community. The purpose of this data table is to characterize the biomass of each focal Pleuraphis jamesii individual at the end of the experiment. Producer defined Plot This attribute in the data table represents a unique plot identifier. Producer defined 911 963 integer number Date This attribute in the data table represents the date of biomass collection. Producer defined 11/6/2019 11/6/2019 date: mm/dd/yyyy Weight This attribute in the data table represents the biomass of the focal Pleuraphis jamesii individual. Producer defined 0.71 5.55 grams Carbon_Isotope_Data.csv This data table represents plant physiological responses to selective mortality treatments in the surrounding plant community, integrated over the growing season. The purpose of this data table is to characterize the carbon and nitrogen isotopes present in each focal Pleuraphis jamesii individual, with the carbon isotope ratio as an integrated proxy for water stress. Producer defined Plot This attribute in the data table represents a unique plot identifier. Producer defined 911 963 integer number Date_Collected This attribute in the data table represents the date of leaf tissue collection. Producer defined 8/23/2022 8/23/2022 date: mm/dd/yyyy Weight_mg This attribute in the data table represents the dry weight of leaf tissue sample from the focal Pleuraphis jamesii individual for the plot. Producer defined 2.95 3.461 milligram N2_Amp_mV This attribute in the data table represents nitrogen amplitude. Amplitude of the sample peak of N2 gas from the focal Pleuraphis jamesii tissue sample for the plot. Producer defined 2316 4860 molecular velocity (mV) N_pct This attribute in the data table represents nitrogen percent. Elemental percentage of nitrogen by weight from the focal Pleuraphis jamesii tissue sample for the plot. Producer defined 1.09 2.33 percent delta15N_vs_At_Air_ppm This attribute in the data table represents delta 15N versus atmospheric air. The corrected isotope delta value for nitrogen 15 measured against the primary reference scale, atmospheric air, from the focal Pleuraphis jamesii tissue sample for the plot. Producer defined 1.36 4 parts per million CO2_Amp_mV This attribute in the data table represents carbon dioxide amplitude. Amplitude of the sample peak of CO2 gas from the focal Pleuraphis jamesii tissue sample for the plot. Producer defined 11322 13361 molecular velocity (mV) C_pct This attribute in the data table represents carbon percent. Elemental percentage of carbon by weight from the focal Pleuraphis jamesii tissue sample for the plot. Producer defined 42.41 48.09 percent delta13C_vs_VPDB_ppm This attribute in the data table represents delta 13C versus Vienna Pee Dee Belemnite (VPDB). The corrected isotope delta value for carbon 13 measured against the primary reference scale, Vienna Pee Dee Belemnite, from the focal Pleuraphis jamesii tissue sample for the plot. Producer defined -16.26 -15.41 parts per million Leaf_Water_Potential_Data.csv This data table represents plant physiological responses to selective mortality treatments in the surrounding plant community at the time of sampling. The purpose of this data table is to characterize the leaf water potential of each focal Pleuraphis jamesii individual during the drying period following a series of monsoon rainstorms. Producer defined Plot This attribute in the data table represents a unique plot identifier. Producer defined 911 963 integer number Date This attribute in the data table represents the date of measurement. Producer defined 7/29/2019 9/12/2019 date: mm/dd/yyyy Time This attribute in the data table represents the time of measurement. All times are in the morning. Producer defined 4:16 6:47 time: hh:mm Leaf_water_potential_Mpa This attribute in the data table represents the leaf water potential of the focal Pleuraphis jamesii individual for the plot. Producer defined -6.626 -0.121 megapascal Phenology_Data.csv This data table represents plant growth and reproduction responses to selective mortality treatments in the surrounding plant community. The purpose of this data table is to characterize the phenological stage and percent greenness of each focal Pleuraphis jamesii individual over the course of the growing season. Producer defined Plot This attribute in the data table represents a unique plot identifier. Producer defined 911 963 integer number Date This attribute in the data table represents the date of phenology measurement. Producer defined 5/22/2019 11/6/2019 date: mm/dd/yyyy Phenological_Stage This attribute in the data table represents Producer defined 0 Dormant/senesced (no green leaves, no emerging leaves) Producer defined 1 Growth initiation (tip of green shoot(s) emerging but no shoot has a green leaf branching off of it) Producer defined 2 Vegetative (full green leaves, no green inflorescences) Producer defined 3 Boot (green inflorescence stalk(s) present but no inflorescences are fully open yet) Producer defined 4 Flowers open (Open inflorescence(s) with some green on the flower stalk) Producer defined Percent_Greenness This attribute in the data table represents greenness. Percent of biomass that is green out of total standing biomass based on ocular estimates for the focal Pleuraphis jamesii individual for the plot. Producer defined 0 90 percent Plant_Ground_Cover_Data.csv This data table represents plant community composition before and after selective mortality treatments. The purpose of this data table is to characterize the cover of all plant species and ground cover types present in each treatment plot. Data were collected using visual estimates of percent cover before herbicide treatments and at the end of the experiment. Producer defined Plot This attribute in the data table represents a unique plot identifier. Producer defined 911 963 integer number Date This attribute in the data table represents the date of plant and ground cover measurements. Producer defined 5/28/2019 9/12/2019 date: mm/dd/yyyy Season This attribute in the data table represents the season of cover sampling. Producer defined All cover was sampled once in the spring and once in the fall. Species This attribute in the data table represents the scientific name of the plant species. Producer defined Plant species or species and genus names follow USDA PLANTS Database Codeset Source: https://plants.usda.gov Non-species cover values and definitions in this field are: Standing dead biomass: Plant material that is senesced or dead but still rooted. Ground litter: Detached (not rooted) plant material Rock > 5mm diameter: Rocks greater than 5mm in diameter Lichens/Moss/Dark Cyano: Biological soil crust cover, including cover of lichens, mosses, or cyanobacteria that visibly darken the soil surface Bare Soil/Light Cyano: Cover of the soil surface that is bare soil, physical crusts, or light cyanobacteria crusts Plant_Functional_Type This attribute in the data table represents the plant functional type. Plant functional type based on growth habit (all) and photosynthetic pathway (grasses only). Producer defined NA Not applicable Producer defined C3Grass Grass species that uses the C3 photosynthetic pathway Producer defined C4Grass Grass species that uses the C4 photosynthetic pathway Producer defined Forb Forb species Producer defined Shrub Shrub species Producer defined Duration This attribute in the data table represents Producer defined NA Not applicable Producer defined A Annual or biennial species Producer defined P Perennial species Producer defined Cover This attribute in the data table represents the percent cover of the plant species or ground cover type as a percent of the total plot area based on ocular estimates. Producer defined 0 92.7 integer number Plot_Data.csv This data table represents the treatments applied to each plant community in each plot. The purpose of this data table is to describe where each plot fits in the experimental design. Each plot was assigned to a unique combination of block and treatment. Producer defined Plot This attribute in the data table represents a unique plot identifier. Producer defined 911 963 integer number Block This attribute in the data table represents the experimental block number. Plots within each block were spatially close to each other. Three plots (one for each treatment) per block. Producer defined 1 6 integer number Treatment This attribute in the data table represents the type of treatment applied to the plot. Producer defined C3_forb_removal C3 grasses and all forbs removed with herbicide Producer defined C4_removal C4 grasses removed with herbicide Producer defined control No plants removed Producer defined Volumetric_Water_Content_Data.csv This data table represents soil moisture responses to selective mortality treatments in the surrounding plant community. The purpose of this data table is to characterize the soil volumetric water content at soil depths of 5 to 25 centimeters in each plot. Producer defined Plot This attribute in the data table represents a unique plot identifier. Producer defined 911 963 integer number Date This attribute in the data table represents the date of the measurement. Producer defined 5/1/2019 11/6/2019 date: mm/dd/yyyy Mean_Daily_VWC This attribute in the data table represents the mean daily soil volumetric water content. Mean daily value was calculated from all hourly values recorded for each day. Values represent soil depths 5 to 25 cm, measured by a sensor at the center of each plot. Producer defined 0.58 11.65 percent GS ScienceBase U.S. Geological Survey mailing and physical

Denver Federal Center, Building 810, Mail Stop 302

Denver CO 80225 United States 1-888-275-8747 sciencebase@usgs.gov The author(s) of these data request that data users contact them regarding intended use and to assist with understanding limitations and interpretation. Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty. Digital Data https://doi.org/10.5066/P97GVNBG None These files contain data available in comma-separated values (csv) format. The user must have software capable of displaying the tabular data. 20260416 Michael C Duniway U.S. Geological Survey, Southwest Region Research Ecologist mailing address

Southwest Biological Science Center

2290 S West Resource Blvd

Moab UT 84532 US (435) 210-2831 mduniway@usgs.gov Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998