DOI: 10.5061/dryad.wdbrv15z5
title: Proportion of annual bromes in cattle diet, with annual brome phenology, forage quality, and forage availability, measured at two mixedgrass prairie study sites, USA

description: Phenological differences between native and invasive plants can facilitate
 invasion, but can also be targeted by management. In the western Great
 Plains of North America, the invasive annual grasses Bromus tectorum L.
 (cheatgrass) and B. arvensis (field brome) begin and end growth earlier
 than native competitors, providing an opportunity for targeted grazing.
 However, managers need to know when grazers preferentially consume or
 avoid annual bromes. We implemented spring targeted grazing for four years
 and quantified temporal cattle consumption patterns at two mixedgrass
 prairie sites in Wyoming and Nebraska, USA. We used fecal DNA
 metabarcoding to measure consumption of annual bromes and coexisting
 native species twice per week. Concurrently, we measured plant phenology,
 forage quality, and biomass. Within years, brome consumption was predicted
 effectively using two phenological metrics—plant height and days after
 seed maturation. Targeted grazing windows, defined as periods with ≥ 75%
 of maximum cattle consumption within a year, started when bromes were 9.3
 cm (± 3.6 SD) tall, ended one day (± 4 SD) after seed maturation, and
 lasted 38 days (± 11 SD). Cattle diet quality remained high throughout
 these grazing windows. Across years, brome consumption ranged from 19% to
 55% of total graminoid consumption, and was consistently higher in years
 when annual bromes grew taller before flowering. Although cattle typically
 selected for native perennials over annual bromes, spring targeted grazing
 reduced brome seed production by 30-77% relative to adjacent pastures
 where grazing began later. These results indicate that simple phenological
 metrics can predict cattle consumption of bromes during spring, both
 within and among years. Carefully timing grazing to align with consumption
 should help managers to control annual bromes and restore native
 mixedgrass prairie plant communities. More broadly, combining temporal
 analyses of livestock diets and plant phenology can be useful for
 precisely targeting grazing of invasive species.
description: # Proportion of annual bromes in cattle diet, with annual brome phenology,
 forage quality, and forage availability, measured at two mixedgrass
 prairie study sites, USA
 [https://doi.org/10.5061/dryad.wdbrv15z5](https://doi.org/10.5061/dryad.wdbrv15z5) ## Description of the data and file structure These datasets and data dictionary are available in comma-delimited format. They are supplement to: Kray et al. 2024. Using targeted grazing to close the phenological niche exploited by invasive annual bromes. Rangeland Ecology & Management. Sampling took place at two mixedgrass prairie study sites: 1\. NE (Scottsbluff, Nebraska, USA): Latitude 42.0270604, Longitude -103.7368762, 1270 m elevation 2\. WY (Cheyenne, Wyoming, USA): Latitude 41.212533, Longitude -104.853681, 1920 m elevation Please see below for a general description of methods used to generate these data. Detailed information on measurements and statistical analyses can be found in the manuscript. NOTE 1: "Brome" or "bromes" is used whenever we were unable to separate two species (*Bromus tectorum* and *Bromus japonicus*) that co-occur at the WY site; otherwise, "BRTE" is used. NOTE 2: "na" indicates missing/unavailable data ### Files and variables #### File: ReadMe.pdf **Description:** ReadMe document. #### File: Data\_dictionary.csv **Description:** Name and definition of each variable in all associated data files. #### File: Cattle\_diet\_composition.csv **Description:** We sequenced plant chloroplast DNA extracted from two fecal samples per week to estimate cattle consumption of dominant plant species, and determine when cattle selected annual bromes in higher or lower proportion relative to all other graminoids in study pastures. ##### Variables * Site: Location (NE or WY) * Year: Sampling year (2017, 2018, 2019, 2020) * Date_diet: Calendar date of diet sampling (mm/dd/yyyy) * DOY_diet: Day of year of diet sampling * Species_code: Plant species, listed as Brome (primarily, *Bromus tectorum*, but also including *Bromus japonicus*, where present); or species code as first two letters of genus and species names (BRTE=*Bromus tectorum*, PASM=*Pascopyrum smithii*, HECO=*Hesperostipa comata*); or other (all other graminoids) * Prop_of_diet: Proportion, of individual graminoid species (or graminoid species groups), in cattle diet, relative to all graminoids measured via fecal DNA metabarcoding #### File: Plant\_phenology.csv **Description:** Phenology was recorded twice per week at each study pasture for 10 marked individuals of *Bromus tectorum*. On each observation date, we measured plant height, and assessed flowering stage and seed maturity. We summarized the phenology of flowering and seed maturation by identifying the days on which ≥ 50% of the 10 marked plants had open, mature flowers or firm seeds, respectively, for each site and year. From these dates, we calculated the continuous metrics “Days after flowering” and “Days after seed maturation,” which included both negative (before 50% flowering or firm seeds observation dates) and positive values (after 50% flowering or firm seeds observation dates). For the NE site in 2019-2020, flowering and seed maturation phenology were observed at the level of individual plants, however, permanent records were made only at the population level. Cells marked "na" indicate where data for the 10 marked plants are unavailable. ##### Variables * Site: Location (NE or WY) * Year: Sampling year (2017, 2018, 2019, 2020) * Date_phen: Calendar date of phenology sampling (mm/dd/yyyy) * DOY_phen: Day of year of phenology observation * Brome_plant_ht (cm): Plant height (cm), mean height of ten marked plants * Flowers_forming_prop: Proportion of ten marked plants that had reached or advanced beyond the flowers forming ("in the boot") phenophase on sampling date * Flowering_prop: Proportion of ten marked plants that had reached or advanced beyond the flowering phenophase on sampling date * Seeds_maturing_prop: Proportion of ten marked plants that had reached or advanced beyond the seed maturation phenophase on sampling date * Days_after_flowersforming: Days after flowers forming, where zero is the date ≥50% of observed plants had flowers forming * Days_after_flowering: Days after flowering, where zero is the date ≥50% of observed plants had open, mature flowers * Days_after_seedmaturation: Days after seed maturation, where zero is the date ≥50% of observed plants had firm seeds * Notes: Qualitative field or sample processing notes relevant to data interpretation and analysis #### File: Forage\_quality.csv **Description:** We sampled plant tissue of *B. tectorum*, *Hesperostipa comata*, and *Pascopyrum smithii* throughout each study pasture once per week.  Samples included a range in phenological stages for each species on each collection date, to represent what was available to cattle. Previous years’ tissue was removed. Tissue was oven-dried at 55 °C, ground, and analyzed by species using near-infrared reflectance spectroscopy (NIRS). ##### Variables * Site: Location (NE or WY) * Year: Sampling year (2017, 2018, 2019, 2020) * Date_fq: Calendar date of forage quality sampling (mm/dd/yyyy) * DOY_fq: Day of year of forage quality sampling * Species_code: Plant species, listed as Brome (primarily, *Bromus tectorum*, but also including *Bromus japonicus*, where present); or species code as first two letters of genus and species names (BRTE=*Bromus tectorum*, PASM=*Pascopyrum smithii*, HECO=*Hesperostipa comata*); or other (all other graminoids) * Crude_protein (% dry basis): Percent crude protein in plant tissue, measured on a composite sample from multiple locations within study pasture * TDN (% dry basis): Percent total digestible nutrients in plant tissue, measured on a composite sample from multiple locations within study pasture #### File: Brome\_seed\_mass.csv **Description:** We harvested annual brome seed each year when it was maturing (prior to its detachment) in 15 paired plots. Each pair included one plot inside (spring grazed) and one plot outside (summer grazed) the study pasture, 1-2 m from the fence. Plots were co-located within mapped brome-dominated vegetation patches, and spatially distributed around the entire pasture perimeter. Harvest dates ranged from 13 June to 8 July (DOY 164-190) at the NE site, and 11 June to 1 July (DOY 164-182) at the WY site. ##### Variables * Site: Location (NE or WY) * Year: Sampling year (2017, 2018, 2019, 2020) * Grazing_season: Timing of grazing (spring grazed=inside study pastures, or summer grazed=outside study pastures) * Brome_seed_mass (g/m2): Current-year biomass (g/m2) of brome seed #### File: Forage\_availability.csv **Description:** We harvested aboveground biomass at 30 (NE) or 60 (WY) fixed sampling locations distributed throughout each pasture once per two week period. Sampling locations were stratified across annual brome-dominated and native mixed-grass communities to reflect the overall proportion of each pasture covered by that community. Biomass was separated into (1) annual bromes, (2) dominant cool-season perennial grass species *H. comata* and *P. smithii*, (3) all other graminoid species, and (4) forbs/shrubs, and oven-dried at 60 °C to constant weight prior to weighing. Previous years’ tissue was removed. For the NE site in 2017, non-brome species were only sorted to functional group (perennial graminoids, forb/shrub). For the WY site, on DOY 165 in 2017, non-brome species could only be sorted to functional group due to loss of original samples. ##### Variables * Site: Location (NE or WY) * Year: Sampling year (2017, 2018, 2019, 2020) * Date_harvest: Calendar date of forage availability sampling (mm/dd/yyyy) * DOY_harvest: Day of year of forage availability sampling * Brome_mass (g/m2): Current-year biomass (g/m2) of brome * PASM_mass (g/m2): Current-year biomass (g/m2) of *Pascopyrum smithii* (PASM) * HECO_mass (g/m2): Current-year biomass (g/m2) of *Hesperostipa comata* (HECO) * Perennial_graminoids_mass (g/m2): Current-year biomass (g/m2) of mixed-species perennial graminoids, including all species * Other_graminoids_mass (g/m2): Current-year biomass (g/m2) of mixed-species graminoids excluding brome, PASM, HECO * Total_graminoids_mass (g/m2): Current-year biomass (g/m2) of all graminoids * Forb/shrub_mass (g/m2): Current-year biomass (g/m2) of mixed-species forbs and shrubs