DOI: 10.5061/dryad.547d7wmfp
title: Cross-scale analysis reveals interacting predictors of annual and perennial cover in Northern Great Basin rangelands

description: Exotic annual grass invasion is a widespread threat to the integrity of
 sagebrush ecosystems in Western North America. Although many predictors of
 annual grass prevalence and native perennial vegetation have been
 identified, there remains substantial uncertainty about how regional-scale
 and local-scale predictors interact to determine vegetation heterogeneity,
 and how associations between vegetation and cattle grazing vary with
 environmental context. Here, we conducted a regionally extensive,
 one-season field survey across burned and unburned, grazed, public lands
 in Oregon and Idaho, with plots stratified by aspect and distance to water
 within pastures to capture variation in environmental context and grazing
 intensity. We analyzed regional and local-scale patterns of annual grass,
 perennial grass, and shrub cover, and examined to what extent plot-level
 variation was contingent on pasture-level predictions of site
 favorability. Annual grasses were widespread at burned and unburned sites
 alike, contrary to assumptions of annual grasses depending on fire, and
 more common at lower elevations and higher temperatures regionally, as
 well as on warmer slopes locally. Pasture-level grazing pressure
 interacted with temperature such that annual grass cover was associated
 positively with grazing pressure at higher temperatures but associated
 negatively with grazing pressure at lower temperatures. This suggests that
 pasture-level temperature and grazing relationships with annual grass
 abundance are complex and context-dependent, though the causality of this
 relationship deserves further examination. At the plot-level within
 pastures, annual grass cover did not vary with grazing metrics, but
 perennial cover did; perennial grasses, for example, had lower cover
 closer to water sources, but higher cover at higher dung counts within a
 pasture, suggesting contrasting interpretations of these two grazing
 proxies. Importantly for predictions of ecosystem response to temperature
 change, we found that pasture-level and plot-level favorability
 interacted: perennial grasses had higher plot-level cover on cooler
 slopes, and this difference across topography was starkest in pastures
 that were less favorable for perennial grasses regionally. Understanding
 the mechanisms behind cross-scale interactions and contingent responses of
 vegetation to grazing in these increasingly invaded ecosystems will be
 critical to land management in a changing world.
description: # Cross-scale analysis reveals interacting predictors of annual and
 perennial cover in Northern Great Basin rangelands
 This dataset accompanies
 the Ecological Applications manuscript "Cross-scale analysis reveals
 interacting predictors of annual and perennial cover in Northern Great
 Basin rangelands." Data collection was led by Madelon Case and Lauren
 Hallett at the University of Oregon in 2021, funded by a cooperative
 agreement with USDA-ARS. Data were primarily collected via field surveys,
 with some annotated data from publicly available spatial datasets (as
 noted below). Contact  or
 with any questions. ## Description of the data
 and file structure unctionalcover_plotdata.csv This file contains
 fractional cover data summarized by functional group from each field plot
 surveyed. Column meanings: PlotID - unique plot identifier for each field
 plot FuncGroup - functional group code (AG = annual grass, F = forb, PG =
 perennial grass, S = shrub, T = tree) cover - fractional vegetation cover
 of that functional group in that plot, determined from
 line-point-intercept transects Pasture - code name for BLM pasture in
 which the plot was situated WaterDist - distance (in meters) from focal
 livestock water source in pasture Asp - aspect (N = north, S = south, flat
 = zero slope so no obvious aspect) FireHistory - fire history category
 (Unburned = not burned for at least 25 years, Burned = burned in the last
 4-25 years before survey) fullwater - binary variable indicating whether
 focal water source contained water (1) or was dry (0) at time of sampling
 Slope - slope of plot (in degrees) Sand - soil sand content, from 4
 homogenized cores taken in plot, analyzed at Oregon State University soil
 health lab (%) Silt - soil silt content (%) Clay - soil clay content (%) C
 - total soil carbon content (%) N - total soil nitrogen content (%) ppt -
 mean annual precipitation (mm), from PRISM tmean - mean annual temperature
 (degrees C), from PRISM elev_ned - elevation above sea level (meters),
 from National Elevation Database hli - heat load index derived from
 topographic data (scaled from 0 to 1, where a higher number means
 relatively more solar irradiation due to topographic position) lastfire -
 year of most recent fire (year for Burned sites, 0 for Unburned sites)
 Crested - binary logical variable for whether crested wheatgrass,
 Agropyron cristatum, was present in the plot (TRUE) or not (FALSE)
 CattleDung - average number of cattle dung piles counted in a 2 x 25 m
 transect logcattledung - log-transformed cattle dung count (log(CattleDung
 + 1)) functionalcover_shrubcategories_plotdata.csv This file contains
 fractional cover data for shrubs only, split by whether shrubs were
 categorized as resprouting or non-resprouting after fire disturbance.
 Column meanings are identical to those given above, except that there is
 no FuncGroup column (this file pertains only to the shrub group, S) and
 there is a Resprout column where 1 = resprouting and 0 = non-resprouting.
 ## Sharing/Access information Data were primarily field-collected by the
 research team. Please cite this dataset and the original published paper
 if the data are reused or shared in any way. Climate data are derived from
 PRISM: PRISM Climate Group at Oregon State University Elevation data are
 derived from NED: National Elevation Dataset (NED) (usda.gov)