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Spatial and ecological variation in dryland ecohydrological responses to climate change: Implications for management

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Ecohydrological responses to climate change will exhibit spatial variability and understanding the spatial pattern of ecological impacts is critical from a land management perspective. To quantify climate change impacts on spatial patterns of ecohydrology across shrub steppe ecosystems in North America, we asked the following question: How will climate change impacts on ecohydrology differ in magnitude and variability across climatic gradients, among three big sagebrush ecosystems (SB-Shrubland, SB-Steppe, SB-Montane), and among Sage-grouse Management Zones? We explored these potential changes for mid-century for RCP8.5 using a process-based water balance model (SOILWAT) for 898 big sagebrush sites using site-and scenario-specific inputs. We summarize changes in available soil water (ASW) and dry days, as these ecohydrological variables may be helpful in guiding land management decisions about where to geographically concentrate climate change mitigation and adaptation resources. Our results suggest that during spring, soils will be wetter in the future across the western United States, while soils will be drier in the summer. The magnitude of those predictions differed depending on geographic position and the ecosystem in question: Larger increases in mean daily spring ASW were expected for high-elevation SB-Montane sites and the eastern and central portions of our study area. The largest decreases in mean daily summer ASW were projected for warm, dry, mid-elevation SB-Montane sites in the central and west-central portions of our study area (decreases of up to 50%). Consistent with declining summer ASW, the number of dry days was projected to increase rangewide, but particularly for SB-Mon-tane and SB-Steppe sites in the eastern and northern regions. Collectively, these results suggest that most sites will be drier in the future during the summer, but changes were especially large for mid-to high-elevation sites in the northern half of our study area. Drier summer conditions in high-elevation, SB-Montane sites may result in increased habitat suitability for big sagebrush, while those same changes will likely reduce habitat suitability for drier ecosystems. Our work has important implications for where land managers should prioritize resources for the conservation of North American shrub steppe plant communities and the species that depend on them.
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Spatial and ecological variation in dryland ecohydrological
responses to climate change: implications for management
KYLE A. PALMQUIST,
1,
DANIEL R. SCHLAEPFER,
1,2
JOHN B. BRADFORD,
3
AND WILLIAM K. LAUENROTH
1
1
Department of Botany, University of Wyoming, 1000 East University Avenue, Laramie, Wyoming 82071 USA
2
Section of Conservation Biology, Department of Environmental Sciences, University of Basel, St. Johanns-Vorstadt 10,
4056 Basel, Switzerland
3
Southwest Biological Science Center, U.S. Geological Survey, 2255 North Gemini Drive, Flagstaff, Arizona 86001 USA
Citation: Palmquist, K. A., D. R. Schlaepfer, J. B. Bradford, and W. K. Lauenroth. 2016. Spatial and ecological variation in
dryland ecohydrological responses to climate change: implications for management. Ecosphere 7(11):e01590. 10.1002/
ecs2.1590
Abstract. Ecohydrological responses to climate change will exhibit spatial variability and understanding
the spatial pattern of ecological impacts is critical from a land management perspective. To quantify
climate change impacts on spatial patterns of ecohydrology across shrub steppe ecosystems in North
America, we asked the following question: How will climate change impacts on ecohydrology differ in
magnitude and variability across climatic gradients, among three big sagebrush ecosystems (SB-Shrubland,
SB-Steppe, SB-Montane), and among Sage-grouse Management Zones? We explored these potential
changes for mid-century for RCP8.5 using a process-based water balance model (SOILWAT) for 898 big
sagebrush sites using site- and scenario-specic inputs. We summarize changes in available soil water
(ASW) and dry days, as these ecohydrological variables may be helpful in guiding land management deci-
sions about where to geographically concentrate climate change mitigation and adaptation resources. Our
results suggest that during spring, soils will be wetter in the future across the western United States, while
soils will be drier in the summer. The magnitude of those predictions differed depending on geographic
position and the ecosystem in question: Larger increases in mean daily spring ASW were expected for
high-elevation SB-Montane sites and the eastern and central portions of our study area. The largest
decreases in mean daily summer ASW were projected for warm, dry, mid-elevation SB-Montane sites in
the central and west-central portions of our study area (decreases of up to 50%). Consistent with declining
summer ASW, the number of dry days was projected to increase rangewide, but particularly for SB-Mon-
tane and SB-Steppe sites in the eastern and northern regions. Collectively, these results suggest that most
sites will be drier in the future during the summer, but changes were especially large for mid- to high-ele-
vation sites in the northern half of our study area. Drier summer conditions in high-elevation, SB-Montane
sites may result in increased habitat suitability for big sagebrush, while those same changes will likely
reduce habitat suitability for drier ecosystems. Our work has important implications for where land man-
agers should prioritize resources for the conservation of North American shrub steppe plant communities
and the species that depend on them.
Key words: Artemisia tridentata; climate impacts; drought; dryland; ecohydrology; sagebrush; Sage-grouse
Management Zone; shrub steppe; soil water availability; water balance.
Received 8 September 2016; accepted 23 September 2016. Corresponding Editor: Debra P. C. Peters.
Copyright: ©2016 Palmquist et al. This is an open access article under the terms of the Creative Commons Attribution
License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
E-mail: kpalmqu1@uwyo.edu
www.esajournals.org 1November 2016 Volume 7(11) Article e01590
INTRODUCTION
Drylands, which cover ~40% of global terres-
trial surface area, are dened by low and highly
variable precipitation regimes of generally small
event sizes and are particularly vulnerable to cli-
mate change (Lauenroth and Bradford 2009,
Wang et al. 2012). The consequences of climate
change for dryland ecosystems is determined by
temperature and precipitation, which interact
with vegetation structure and soil texture and
depth to determine the availability of water,
which is often the primary limiting resource (Sala
et al. 1992, Loik et al. 2004). Here, we focus on
big sagebrush ecosystems, important mid-lati-
tude drylands that cover a large portion of the
United States, which are characterized by soil
water recharge in winter and early spring, fol-
lowed by a dry soil period during the growing
season (Schlaepfer et al. 2012a). In this region,
temperature is projected to increase on average
by 5.5°C by the end of the 21st century under
representative concentration pathway RCP8.5,
while predictions for precipitation are more
uncertain, with potential increases or decreases
of 10% possible (IPCC 2013, Anderegg and Diff-
enbaugh 2015). Palmquist et al. (2016) explored
climate change impacts on water balance for big
sagebrush ecosystems using a process-based soil
water simulation model and found that on aver-
age soils may be wetter in the future during the
late fall to early spring due to projected increases
in cold-season precipitation, but will likely dry
out more rapidly and remain drier for a longer
portion of the growing season, due to shifts in
transpiration, evaporation, and groundwater
recharge to earlier in the year. These results
reect region-wide expectations for big sage-
brush ecosystems, but do not capture the impor-
tant spatial variability in ecohydrological
responses to climate change that may emerge in
response to gradients of precipitation, tempera-
ture, elevation, topography, and soil properties
across the western United States (Miller et al.
2011, Chambers et al. 2014a).
Anticipated future changes in precipitation
and temperature are expected to vary across the
western United States. Some of the variability in
future precipitation projections are related to lati-
tude, as multi-model means and ensemble pre-
dictions suggest increases in winter precipitation
for the northern half of the western United
States, but decreases in southern latitudes (Abat-
zoglou and Kolden 2011, IPCC 2013, Anderegg
and Diffenbaugh 2015). Future temperature
regimes may also exhibit a spatial pattern across
latitude, with potentially larger increases in tem-
perature in the northern portion of the western
United States (Abatzoglou and Kolden 2011). In
addition, future climatic regimes will likely be
contingent on elevation, with anticipated
increases in precipitation at higher elevations
and decreases at lower elevations (IPCC 2013).
The ratio of precipitation falling as snow and the
duration of snowpack is predicted to decrease
across much of the western United States, but
particularly for lower elevations in the south-
western United States (Brown and Mote 2009,
Klos et al. 2014, Palmquist et al. 2016). Collec-
tively, these changes may result in considerably
drier conditions in the southwest United States
(Diffenbaugh et al. 2008, Abatzoglou and Kolden
2011, Anderegg and Diffenbaugh 2015), which
are already being realized (Seager et al. 2007)
and potentially wetter conditions in the north-
eastern portion of the western United States
(Maloney et al. 2014, Melillo et al. 2014).
In addition to spatial variability of future cli-
matic impacts, we expect that big sagebrush
ecosystems may differ in their response to climate
change due to differences in their ecology. There
are three primary big sagebrush ecosystems
found in the western United States: Intermountain
Basins Big Sagebrush Shrubland (SB-Shrubland),
Intermountain Basins Big Sagebrush Steppe
(SB-Steppe), and Intermountain Basins Montane
Sagebrush Steppe (SB-Montane; USGS 2011,
Schlaepfer et al. 2012a). These ecosystems are
characterized by shifts in the dominant big sage-
brush sub-species and are differentiated by their
climatic niches, soil properties, and geography
(Miller et al. 2011). SB-Montane ecosystems, dom-
inated by Artemisia tridentata ssp. vaseyana,may
have greater resilience and resistance to environ-
mental stress and disturbance because of greater
resource availability and more suitable conditions
for plant growth and survival, while warm, dry
big sagebrush communities dominated by Artemi-
sia tridentata ssp. wyomingensis and ssp. tridentata
(SB-Steppe, SB-Shrubland) may have lower resili-
ence and resistance to disturbance and invasion
(Chambers et al. 2007, 2014a,b, Miller et al. 2011,
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PALMQUIST ET AL.
Davies et al. 2012). As such, we expect that these
three ecosystems will have different responses
and capacities to withstand perturbations in the
face of changing precipitation and temperature
regimes, with the consequence that ecohydrologi-
cal responses, management implications, and the
resulting management actions will vary across
them (Davies et al. 2006, Davies and Bates 2010).
Understanding the spatial pattern of future cli-
mate predictions and their ecological impacts is
critical from a land management perspective
(Diffenbaugh et al. 2008). Land managers have
limited resources and need guidance on where to
spatially concentrate those resources for climate
change mitigation and adaptation. An additional
concern of land managers who are making deci-
sions in the face of climate change is whether
high-qualitysites will continue to be of high
quality in the future. Decisions on where to con-
centrate resources now in anticipation of future
changes may be informed by spatial changes in
habitat suitability and identication of areas that
are most vulnerable to climate change (Manier
et al. 2013). In the big sagebrush region, much of
the ongoing conservation and management
efforts are focused on greater sage-grouse (Cen-
trocercus urophasianus). Big sagebrush is the most
important sagebrush species for greater sage-
grouse habitat (Miller et al. 2011); however, big
sagebrush plant communities currently differ in
their capacity to provide suitable habitat (Davies
et al. 2006, Davies and Bates 2010). As such, a
key need of land managers is to understand
whether current habitat will continue to be suit-
able in the future and what implications the
future spatial pattern of habitat will have for
greater sage-grouse conservation and manage-
ment (Homer et al. 2015).
We used two approaches to quantify the
impacts of altered climate on variability in future
ecohydrology. First, we explore the variability of
future ecohydrological responses across the three
big sagebrush ecosystems found in the western
United States. Second, we quantied the spatial
variability in future ecohydrological responses
across the seven Sage-grouse Management Zones
(MZs) in the western United States. Specically,
we asked the following questions: (1) How are
changes in future big sagebrush ecohydrology
related to climatic gradients? (2) How will cli-
mate change impacts on ecohydrology differ in
magnitude and variability across sites for big
sagebrush ecosystems? and (3) What is the spa-
tial pattern of climate change impacts on big
sagebrush ecohydrology and what are the antici-
pated impacts within Sage-grouse Management
Zones? We explored these potential changes for
mid-century (20302060) for RCP8.5 (IPCC 2013)
using a process-based water balance model for
898 big sagebrush sites across the western United
States using site-specic climate information,
vegetation parameters, and soil properties for
multiple soil layers. We focused on analyzing
changes in soil water availability and ecological
drought from current conditions to mid-century,
as we believe these ecohydrological variables are
most relevant in big sagebrush ecosystems and
may inform land management decisions about
where to geographically concentrate climate
change mitigation and adaptation resources in
the coming decades. We believe the rst step in
designing climate change mitigation is to under-
stand the spatial and seasonal variability in
future soil water availability, which is often the
key driver of aboveground plant community
structure in big sagebrush ecosystems, on which
greater sage-grouse depend, in addition to mini-
mum winter temperature and snow cover (Sch-
laepfer et al. 2012c, 2015). As such, our work has
the ability to inform conservation and manage-
ment action at broad spatial scales in a large por-
tion of the United States. In addition, we use an
unique approach to summarize sub-continental
changes in ecohydrology in response to changing
climatic conditions at regional scales at which
management decisions and management actions
are made. We believe this approach will be of
interest to applied scientists and practitioners
working in other ecosystems that span large
spatial extents, by providing a framework to
implement local and regional conservation and
management action.
METHODS
Study area and site selection
We used 898 sites described in Schlaepfer et al.
(2012a) and Palmquist et al. (2016), which are
located within a 3.1 910
6
km
2
region of the
western United States (Fig. 1). We chose these
sites randomly from land cover data from regio-
nal gap analysis programs (GAP, grid cells of
www.esajournals.org 3November 2016 Volume 7(11) Article e01590
PALMQUIST ET AL.
30 930 m
2
), which were classied as big sage-
brush ecosystems (USGS 2011). Our 898 sites
span the three big sagebrush ecosystems found
in the western United States: SB-Shrubland
(n=357), SB-Steppe (n=348), and SB-Montane
(n=193; Fig. 1).
SB-Shrubland ecosystems are located primar-
ily in the southern portion of the big sagebrush
ecosystem range (Fig. 1) and occur in wide, at
basins on deep fertile soils (Schultz 2006, Miller
et al. 2011). SB-Steppe ecosystems occupy the
northern latitudes of the western United States
(Fig. 1), occur on warm, dry valley and foothills
sites, and are thought to be the driest of the
big sagebrush ecosystems (Schultz 2006, Miller
et al. 2011). SB-Montane ecosystems occupy
upland sites, which tend to be at higher
elevation and are often cooler and wetter than
either SB-Shrubland or SB-Steppe (Schultz 2006,
Miller et al. 2011), although there is considerable
elevational overlap between all three (Chambers
et al. 2014b; Appendix S1). SB-Montane ecosys-
tems are often more species rich with greater
plant biomass (Davies and Bates 2010). SB-
Shrubland is dominated primarily by A. triden-
tata ssp. tridentata with lesser amounts of A. tri-
dentata ssp. wyomingensis, SB-Steppe is co-
dominated by A. tridentata ssp. tridentata and
A. tridentata ssp. wyomingensis, while A. triden-
tata ssp. vaseyana is the dominant in SB-Montane
sites. MAT of the SB-Shrubland sites is 7.6°C
(range =1.816°C), 7.2°C (range =1.211.7°C)
for SB-Steppe, and 4.0°C (range =1.7°to
8.7°C) for SB-Montane. Mean annual precipita-
tion (MAP) increases with elevation, with
greater amounts of precipitation in SB-Montane
(479 mm) relative to SB-Shrubland (295 mm)
and SB-Steppe (324 mm).
Seven Sage-grouse Management Zones have
been designated in the western United States by
the Western Association of Fish and Wildlife
Agencies to encompass populations of greater
sage-grouse in regions with similarities in cli-
mate, elevation, topography, geology, soils, and
oristics (West 1983, Miller and Eddleman 2001,
Manier et al. 2013). We use them to explore both
the spatial pattern of future ecohydrological
changes and the implications of those changes
for plant community structure, habitat quality
for greater sage-grouse, and management action.
A total of 858 of our 898 sites fall within one of
the seven Sage-grouse Management Zones: MZ
1: Great Plains (n=152), MZ 2: Wyoming Basins
(n=158), MZ 3: Southern Great Basin (n=145),
MZ 4: Snake River Plain (n=249), MZ 5: North-
ern Great Basin (n=99), MZ 6: Columbia Basin
(n=30), and MZ 7: Colorado Plateau (n=25;
Fig. 1). Thus, our results summarizing future
ecohydrology for the three ecosystems use all
898 sites, while our results for Management
Zones utilize 858 sites. For each MZ, we summa-
rize the proportion of sites that are SB-Shrub-
land, SB-Steppe, and SB-Montane (Fig. 1).
SOILWAT simulation modeling
We quantied changes in ecohydrology at each
of our 898 sites using SOILWAT, a process-based
soil water balance model (Parton 1978, Sala et al.
1992, Lauenroth and Bradford 2006), which
has been modied and validated for big sage-
brush ecosystems, by incorporating modules for
Fig. 1. Map of the 898 big sagebrush sites and the
Sage-grouse Management Zones (MZ 1: Great Plains,
MZ 2: Wyoming Basins, MZ 3: Southern Great Basin,
MZ 4: Snake River Plain, MZ 5: Northern Great Basin,
MZ 6: Columbia Basin, and MZ 7: Colorado Plateau).
The pie charts show the proportion of sites within each
management zone that are SB-Steppe, SB-Montane,
and SB-Shrubland.
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PALMQUIST ET AL.
hydraulic redistribution, snow, multiple vegeta-
tion types, and phenology and biomass as a func-
tion of climate (Schlaepfer et al. 2012a,b,
Bradford et al. 2014a). SOILWAT uses site-speci-
c daily precipitation and temperature data, site-
specic monthly climate conditions (relative
humidity, wind speed, cloud cover), site-specic
monthly vegetation parameters for multiple
plant functional types (total aboveground bio-
mass, litter, living aboveground biomass, active
root depth prole), and site-specic soil proper-
ties from multiple layers to model all compo-
nents of daily water balance. This includes
interception by vegetation and litter, evaporation
of intercepted water, bare-soil evaporation, inl-
tration, groundwater recharge, transpiration
from each soil layer, and available soil water for
plants to use. Our modeling approach allows for
changes in vegetation based on climate, such that
vegetation parameters under current conditions
(19802010) and future conditions (20302060)
varied due to differences in climate between
those time periods. Although vegetation parame-
ters varied across sites and time periods,
monthly parameters were held constant for each
site during a simulation run for a given time
period.
We extracted site-specic current and future
weather data for all 898 sites to run SOILWAT
simulations for 19802010 and 20302060. Cur-
rent temperature and precipitation data was
extracted from 1/8-degree gridded, daily weather
data for 19802010 (Maurer et al. 2002). Monthly
estimates of relative humidity, wind speed, and
cloud cover were obtained from the Climate
Maps of the United States (http://cdo.ncdc.noaa.
gov/cgi-bin/climaps/climaps.pl). To obtain future
daily weather data for each site, we extracted
temperature and precipitation data for each
GCM from the Downscaled CMIP3 and CMIP5
Climate and Hydrology Projectsarchive at
http://gdo-dcp.ucllnl.org/downscaled_cmip_pro
jections/ (Maurer et al. 2007) and then applied
the hybrid-delta downscaling method, which
uses historic daily weather data with monthly
future predictions to obtain future daily forcing
(Hamlet et al. 2010, Dickerson-Lange and
Mitchell 2014). In addition, we extracted site-
specic soil data for each soil layer (sand %, clay
%, volume of gravel, bulk density, soil depth) for
all 898 sites from the NRCS STATSGO database
(1-km
2
grids; Miller and White 1998). To obtain
site-specic parameters for the relative composi-
tion of C3 and C4 grasses and shrubs as well as
monthly aboveground biomass, monthly live
biomass, monthly litter, and monthly root depth
distributions, we used the methods provided in
Bradford et al. (2014b) and applied by Palmquist
et al. (2016), which relate climate conditions to
vegetation and seasonal biomass. Specically, the
composition of plant functional types (shrubs, C
3
grasses, C
4
grasses) was calculated for each of
the 898 sites based on current climate and re-cal-
culated for future climate (Paruelo and Lauen-
roth 1996). Mean monthly aboveground total
biomass, monthly live biomass, and monthly lit-
ter were calculated based on site-specic precipi-
tation and temperature, which collectively
inuence biomass and growing season length.
Transpiration coefcients were calculated sepa-
rately for each plant functional type based on the
amount of root biomass within each soil layer
(Schenk and Jackson 2003).
We simulated ecosystem water balance using
current conditions (19802010) and future cli-
matic conditions (20302060) from 10 GCMs for
RCP8.5 (see Palmquist et al. 2016, Table S1 for
list of GCMs). We selected GCMs which per-
formed well in the western United States (Rupp
et al. 2013) and which were representative of
the families of GCMs in existence (Knutti et al.
2013). Although we ran SOILWAT simulations
for 10 GCMs, we focus on summarizing predic-
tions for the median GCM, which was identi-
ed individually for each of the 898 sites. To
identify the median GCM prediction for each
site, we sorted the 30-year mean annual values
for the 10 GCMs and then averaged values 5
and 6 after sorting. We identied and calculated
the median GCM prediction for each climatic
and ecohydrological variable separately for
19802010 and 20302060. To characterize the
uncertainty for each ecohydrological variable,
we indicate how many of the GCMs agree on
the direction of the change predicted by the
median.
Statistical analysis
We rst summarized the key climatic variables
that have previously been identied as important
in inuencing big sagebrush ecohydrology
(Lauenroth and Bradford 2012, Schlaepfer et al.
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PALMQUIST ET AL.
2012a). This included current and predicted
future mean annual precipitation (mm) and tem-
perature (°C), which were derived from GCM
output. We also characterized climatic variables
that reect the type, timing, and size of current
and future precipitation events: current cold-sea-
son precipitation (CSP; OctoberMarch), change
in CSP, current annual snow/precipitation ratio,
change in snow/precipitation ratio, current CSP/
total precipitation ratio (CSP ratio), change in
CSP ratio, current number of precipitation
events, change in number of precipitation events,
current fraction of precipitation events in the 0
5 mm size class, and change in the fraction of 0-
to 5-mm precipitation events.
To examine the impact of altered climate on
soil water dynamics, we quantied several key
ecohydrological variables in big sagebrush
ecosystems (Schlaepfer et al. 2012a). This
included: annual total transpiration (T, mm),
annual total evaporation (E, mm), annual total
evapotranspiration (AET, mm), annual T/AET
ratio, annual groundwater recharge (GR, mm),
and mean available soil water (ASW, mm,
greater than 3.9 MPa) in spring and summer
for top and bottom soil layers. Lastly, we summa-
rized several variables that characterize changes
in the length and timing of dry periods in the
future, which we believe will inform land
management decisions: aridity index (annual
precipitation/annual potential evapotranspira-
tion; UNEP 1992, Maestre et al. 2012) and the
number of dry days (less than 3.9 MPa) for
both top and bottom soil layers on an annual
basis and separately for spring (March, April,
May) and summer (June, July, August). We used
3.9 MPa as a cutoff for both ASW and dry days,
as big sagebrush can extract some soil water up
to this point; thereafter, the risk of cavitation
increases leading to reduced hydraulic conduc-
tivity (Kolb and Sperry 1999).
To address how climate change will impact big
sagebrush ecohydrology (question 1), we explore
which geospatial (latitude, longitude, elevation)
and climatic variables inuence future changes
in each ecohydrological variable across all 898
sites in the western United States. We conducted
principal components analysis (PCA) to deter-
mine the main axes of variation in our geospatial
and climatic data set and to reduce the dimen-
sionality of that data set. PCA was implemented
using the prcomp function after centering and
scaling the data to have unit variance. The rst
three PCs explain 70% of the variance
(PC1 =34%, PC2 =22%, PC3 =14%). PC1 rep-
resents a gradient of precipitation, capturing
amount, type, event size, and timing (Table 1;
Appendix S2), while PC2 largely represents a
temperature gradient, but also captures aspects
of precipitation. PC3 is harder to interpret, with
Table 1. Loadings of climatic and geospatial variables for PC1PC3 from principal components analysis.
Climatic or geospatial variable PC1 PC2 PC3
Longitude 0.18 0.39 0.11
Latitude 0.18 0.14 0.46
Elevation 0.21 0.22 0.41
MAP (mm) 0.27 0.30 0.20
Change in MAP (mm) 0.33 0.01 0.13
MAT (°C) 0.14 0.39 0.09
Change in MAT (°C) 0.05 0.36 0.24
Cold-season precipitation (mm) 0.38 0.03 0.13
Change in cold-season precipitation (mm) 0.31 0.01 0.35
Cold-season precipitation/total precipitation ratio 0.29 0.32 0.00
Change in cold-season precipitation/total precipitation ratio 0.11 0.00 0.49
Snow/precipitation ratio 0.33 0.17 0.07
Change in snow/precipitation ratio 0.33 0.14 0.16
Number of precipitation events 0.09 0.28 0.24
Change in number of precipitation events 0.02 0.27 0.11
Fraction of precipitation events, 05 mm 0.27 0.17 0.08
Change in fraction of precipitation events, 05 mm 0.24 0.27 0.06
Note: The rst three PCs explain 70% of the variation in the climatic and geospatial data set.
www.esajournals.org 6November 2016 Volume 7(11) Article e01590
PALMQUIST ET AL.
latitude, change in CSP, change in CSP ratio, and
the number of precipitation events loading nega-
tively on PC3 and elevation and change in MAT
loading positively (Table 1; Appendix S2). To
determine which climatic axes were related to
future ecohydrology, we extracted the axis scores
for the rst three PCs axes and calculated Pear-
son correlation coefcients (r) between them and
the ecohydrological variables of interest: absolute
change in ASW in top and bottom layers for both
spring and summer, and absolute change in
mean number of dry days in top and bottom lay-
ers in spring and summer.
To understand how future ecohydrology may
vary across the three big sagebrush ecosystems
(question 2), we summarize median absolute and
percent changes in all climatic and ecohydrologi-
cal variables described above for each ecosystem.
To quantify the spatial variability in future water
balance changes across the 898 sites in the west-
ern United States (question 3), we summarize
median absolute and percent changes in climate
and ecohydrology for all variables described
above for each of the seven Sage-grouse Manage-
ment Zones. We present percent changes to indi-
cate how the absolute change values we report
relate to current magnitudes. All statistical analy-
ses were performed in R v.3.2.2 (R Development
Core Team 2015).
RESULTS
Climate change impacts on ecohydrology for all
sites
PC1 represents a precipitation gradient with
high PC1 values corresponding to low-elevation
sites in the northeastern portion of our study area
(MZ 1) that currently have a precipitation regime
characterized by a large fraction of small events,
falling mostly in the warm season. These sites are
expected to have decreases to small increases in
precipitation in the future (Appendix S2). In con-
trast, high-elevation sites (low PC1 values),
which are already dened by dominantly CSP of
large event sizes, will continue to increase in pre-
cipitation in the future, but with a smaller frac-
tion falling as snow. Sites with high PC2 axis
scores tend to be at low elevation with relatively
dry, hot climates that are dened by few cold-
season precipitation events. These sites can be
found in the west and southwest (MZs 3, 5, and
6) and are predicted to have small temperature
increases, along with decreases in the number of
precipitation events, but increases in the size of
those events (Appendix S2). Sites with high PC3
values are found at southern and southeastern
high-elevation sites (MZs 2 and 7) where the
future will be much warmer with fewer precipi-
tation events and less cold-season precipitation.
Our simulations indicate the amount and tim-
ing of available soil water (ASW) will likely
change by mid-century. ASW in both top and
bottom soil layers was predicted to increase in
the spring months, but decrease in summer for
most sites. Absolute changes in ASW in spring
were negatively correlated with PC1 (top layers:
r=0.23, bottom layers: r=0.48) and PC2
(top layers: r=0.61, bottom layers: r=0.38),
suggesting ASW is likely to increase the most in
high-elevation sites that currently have and are
predicted to have greater amounts of cold-season
precipitation in the future (Fig. 2A, B). In con-
trast, absolute changes in summer ASW for top
layers were positively correlated with PC1
(r=0.5), PC2 (r=0.41), and PC3 (r=0.13), sug-
gesting the largest decreases in summer ASW are
expected in mid-elevation sites located in the
central and west-central regions, which are cur-
rently warm and dry and are predicted to have
relatively small increases in future precipitation
(Fig. 2C; Appendix S3). For bottom layers, abso-
lute changes in summer ASW were correlated
with PC1 (r=0.5) and PC2 (r=0.3), again sug-
gesting that sites with the greatest reduction in
summer soil water will be warm, dry sites
(Fig. 2D; Appendix S2).
For most sites, absolute changes in the number
of future spring dry days were predicted to be
small (median predictions ~0), especially for
bottom soil layers. For those sites that will
change, the greatest increases in spring dry days
are predicted for dry, hot sites at low elevation in
the southwest United States (PC2 r=0.43, PC1
r=0.27). In contrast, most sites may have
increases in the number of summer dry days in
the future. Absolute changes in summer dry days
for top layers were weakly negatively correlated
with PC2 (r=0.26) and PC3 (r=0.21), sug-
gesting greater increases for sites that will
become considerably warmer in the future; these
sites tend to be at higher latitudes and elevations
and further east (Appendices S2 and S4).
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PALMQUIST ET AL.
Predictions were similar for bottom soil layers,
with absolute change in summer dry days
weakly negatively correlated with PC1
(r=0.13), PC3 (r=0.11), and PC2 (r=0.09;
Appendix S4).
Absolute changes in AET were negatively
correlated with PC1 (r=0.41) and weakly posi-
tively correlated with PC2 (r=0.09), suggesting
sites further west with greater water inputs and
warmer temperatures in the future will have
greater water loss through AET. Changes in GR
were strongly negatively correlated with PC1
(r=0.76) and negatively correlated with PC3
(r=0.3): Increases in GR are expected for sites
with predicted future increases in precipitation
(Table 1; Appendix S2).
Fig. 2. Absolute changes in mean daily spring and summer ASW for all 898 sites for top and bottom soil lay-
ers. All values presented are for the median GCM and were calculated from 19802010 to 20302060. Each panel
is plotted according to the two most important PC explaining variation in that ecohydrological variable across all
898 sites in the western United States.
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PALMQUIST ET AL.
Climate change impacts on ecosystem
ecohydrology
All results reported here reect the median
GCM of the 10 GCMs examined for RCP8.5,
unless otherwise specied. Future changes in
median MAP were relatively consistent across
ecosystems, with increases predicted for SB-
Shrubland (9%), SB-Montane (7%), and SB-
Steppe (5%; Fig. 3A; Appendix S5). More
precipitation will be falling in the cold season,
with no differences in the magnitude of these
changes across ecosystems (Appendix S6). The
number of precipitation events is predicted to
decrease, particularly for SB-Shrubland, with
fewer events in the 05 mm size class for all
ecosystems. Despite increased precipitation in
the future, less precipitation will be falling as
snow: Reductions in snow/precipitation ratio
were slightly greater for SB-Shrubland (39%),
compared with SB-Steppe (28%) and SB-Mon-
tane (27%; Appendix S6). Absolute changes in
MAT by mid-century were large, but especially
so for SB-Steppe and SB-Montane (Fig. 3B).
Differences in the magnitude of percent
changes in ASW emerged across ecosystems: Top
soil layers will likely be slightly wetter in
SB-Steppe (15%) and SB-Montane (15%) during
the spring, relative to SB-Shrubland (3%), while
the greatest increase in spring ASW in bottom
layers was for SB-Montane (22%), compared
Fig. 3. Changes in MAP (A), MAT (B), GR (C), and AET (D) from 19802010 to 20302060 for each big
sagebrush ecosystem. Values shown are the median (black horizontal line), rst and third quartiles (ends of the
box), range (ends of the whiskers), and outliers (points) across all sites for each ecosystem for the median GCM.
The number of GCMs that agree on the direction of the median change across sites is shown just above the
x-axis.
www.esajournals.org 9November 2016 Volume 7(11) Article e01590
PALMQUIST ET AL.
with SB-Steppe (16%) and SB-Shrubland (13%;
Fig. 4A, B). During the summer, SB-Shrubland
had slightly larger predicted decreases in ASW
for top layers (39%, relative to the other
ecosystems), although all had predicted
decreases of 3139% (Fig. 4C). For bottom layers,
SB-Shrubland and SB-Montane had slightly lar-
ger decreases in summer ASW, than SB-Steppe
(Fig. 4D). There was considerable variation
within each ecosystem in the magnitude of
changes in ASW, particularly for SB-Shrubland
(Fig. 4). In contrast to percent changes in ASW,
SB-Montane ecosystems consistently had greater
absolute increases in spring ASW and greater
decreases in summer ASW than the other ecosys-
tems (Appendix S7).
The median prediction for the number of
spring dry days suggests little change in top
layers (SB-Shrubland: 0.5 d, SB-Steppe and
SB-Montane: 0) and no change in bottom layers
(0 for all ecosystems; Fig. 5A, B; Appendix S8).
However, increases and decreases were projected
for some sites for each ecosystem, particularly
for SB-Shrubland. Absolute and percent changes
in the number of summer dry days were consis-
tently larger for both top and bottom soil layers
Fig. 4. Percent change in ASW from 19802010 to 20302060 for each big sagebrush ecosystem in spring for
top and bottom soil layers (A, B) and summer for top and bottom soil layers (C, D). Values shown are the median
(black horizontal line), rst and third quartiles (ends of the box), and range (ends of the whiskers) across all sites
for each ecosystem for the median GCM. Outliers are not shown here. The number of GCMs that agree on the
direction of the change in the median value reported is shown just above the x-axis.
www.esajournals.org 10 November 2016 Volume 7(11) Article e01590
PALMQUIST ET AL.
for SB-Montane (16% and 24% increase for top
and bottom, respectively), relative to SB-Steppe
(9% and 13% increase) and SB-Shrubland (3%
and 6% increase; Fig. 5C, D; Appendix S8). On
average, all GCMs agree that summer dry days
will increase for SB-Montane in the future. How-
ever, there were decreases predicted for some
sites in each ecosystem: SB-Shrubland (top lay-
ers: 20%, bottom layers: 14%), SB-Steppe (top
layers: 5%, bottom layers: 6%), and SB-Montane
(top layers: 5%, bottom layers: 2%). Consistent
with our ndings for the number of summer dry
days, the aridity index for SB-Montane and SB-
Steppe was projected to decrease slightly in the
future, suggesting drier conditions, while the
aridity index for SB-Shrubland was projected to
increase slightly (Appendix S6).
Actual evapotranspiration (AET) will likely
increase in the future for all ecosystems (47%),
although slightly less for SB-Steppe (Fig. 3D;
Appendix S5). Most of the increase in AET is the
result of increased transpiration (T), as evapora-
tion (E) was predicted to change only by +12mm
(Appendix S6). Changes in T were relatively
Fig. 5. Absolute change in the number of dry days from 19802010 to 20302060 for each big sagebrush
ecosystem in spring for top and bottom soil layers (A, B) and summer for top and bottom soil layers (C, D).
Values shown are the median (black horizontal line), rst and third quartiles (ends of the box), range (ends of the
whiskers), and outliers (points) across all sites for each ecosystem for the median GCM. The number of GCMs
that agree on the direction (+,, 0) of the change in the median value reported is shown just above the x-axis.
For bottom layers in spring, all GCMs agree with the median prediction of 0.
www.esajournals.org 11 November 2016 Volume 7(11) Article e01590
PALMQUIST ET AL.
consistent across ecosystems, as were changes in E
and T/AET ratio (Appendix S6). However, there
was considerable variation in the direction and
magnitude of changes in AET, T, E, and T/AET
across sites within each ecosystem (Fig. 2D;
Appendix S6). Percent changes in GR were similar
across all ecosystems (SB-Shrubland: 18%, SB-
Steppe: 15%, SB-Montane: 14%; Fig. 3C), but the
median predicted absolute change was higher
for SB-Montane (Appendix S5). Most sites, regard-
less of ecosystem, were predicted to have increa-
ses in GR (SB-Shrubland: 84%, SB-Steppe: 95%,
SB-Montane: 84%), due to predicted increases in
MAP (Fig. 3A, C; Appendix S6).
Spatial patterns of climate change impacts on
ecohydrology: management zone responses
Most GCMs agreed that MAP will increase in
each MZ, most of which will be falling in the cold
season (Fig. 6A; Appendix S9). Increases in MAP
are projected to be greatest for MZ 3: Southern
Great Basin (11%) and lowest for MZ 1: Great
Plains (3%; Fig. 6A). However, decreases in MAP
were predicted for a small percentage of sites in
Fig. 6. Changes in MAP (A), MAT (B), GR (C), and AET (D) from 19802010 to 20302060 for each Sage-grouse
Management Zone. Values shown are the median (black horizontal line), rst and third quartiles (ends of the
box), range (ends of the whiskers), and outliers (points) across all sites for each Management Zone for the median
GCM. The number of GCMs that agree on the direction of the change in the median value reported is shown just
above the x-axis.
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PALMQUIST ET AL.
each MZ except the Snake River Plain and
Columbia Basin: MZ 1 (8%), MZ 2 (1%), MZ 3
(1%), MZ 5 (7%), and MZ 7 (12%). Less precipita-
tion will be falling as snow for all sites, but those
reductions are expected to be particularly high in
the south and western portions of the range
(MZs 37; Appendix S9). Fewer precipitation
events are expected rangewide, especially for the
western half of the study area (MZs 36), which
in tandem with reductions in the fraction of 0- to
5-mm events suggest fewer, larger precipitation
events in the future (Appendix S9). Increases in
MAT are predicted to be greatest in the east (MZs
14), relative to the west (MZs 5 and 6; Fig. 6B).
In contrast to ensemble predictions, there was no
relationship between changes in MAP or MAT
and latitude across the big sagebrush region
(Appendix S10).
For top soil layers, the eastern and central
regions of the big sagebrush distribution (MZs
14) are predicted to have increases in spring
ASW, especially MZ 1 (22%) and MZ 2 (24%;
Fig. 7A; Appendix S5). In contrast, the north-
western United States (MZs 5 and 6) is expected
to experience a 1% decline in ASW (with sites
experiencing both increases and decreases in
ASW), while the median prediction for the Color-
ado Plateau suggested slightly reduced spring
ASW (2%; Fig. 7A). For bottom soil layers, the
median prediction suggested increases in spring
ASW for all MZs, but especially for MZ 1 (20%),
MZ 2 (27%), MZ 3 (18%), and MZ 4 (17%;
Fig. 7B). All MZs are expected to have somewhat
large reductions in the amount of ASW in the
summer (2750%), with the largest decreases
expected for the Northern Great Basin
(Fig. 7C, D; Appendix S5). There was consis-
tently more variability in the magnitude of
changes in spring and summer ASW for sites
within MZs 25, compared with other MZs.
The south and southwestern regions (MZs 36)
are expected to have little change in the number
of spring dry days in top layers in the future (0
1 d; Fig. 8A). In contrast, the Great Plains and
Wyoming Basins will likely have slightly fewer
spring dry days (2.5 and 0.5 d, respectively),
while spring dry days are predicted to increase
for the Colorado Plateau (+1.5 d; Fig. 8A). For all
MZs, the median prediction for change in spring
dry days for bottom layers was zero, although a
small fraction of sites in each MZ may increase or
decrease by mid-century (Fig. 8B; Appendix S8).
The number of summer dry days was projected to
increase for almost all MZs for both top and bot-
tom soil layers (Fig. 8C, D), suggesting soils will
be drier for a longer portion of the growing season
in the future across most of the big sagebrush
region. The one exception was bottom soil layers
in MZ 7 (median prediction =0). Increases in
summer dry days for top and bottom layers were
greater for the Great Plains (13% and 20%) and
Wyoming Basins (11% and 11%) and smallest for
the Southern Great Basin (2.5% and 3.5%) and the
Colorado Plateau (4% and 0%). Absolute and
percent changes in summer dry days were consis-
tently greater for bottom soil layers than for top
soil layers within each MZ (Fig. 8C, D;
Appendix S8). Change in the aridity index
suggests the central region of the big sagebrush
distribution will become slightly wetter in the
future on an annual basis, while the Great Plains,
Wyoming Basins, Northern Great Basin, and
Colorado Plateau will become slightly more arid
(Appendix S9).
Actual evapotranspiration will likely increase
more or less uniformly across all the MZs, with
the smallest increases in the Great Plains (9 mm,
3%), relative to the other MZs (1420 mm, 57%;
Fig. 6D). GR will likely increase on average
across all MZs, but particularly for the southern
and western portions of the big sagebrush distri-
bution (1631%, MZs 37), relative to the eastern
MZs (712%, Great Plains and Wyoming Basins;
Fig. 6C). The magnitude of GR increases in each
MZ largely mirrors the changes in MAP pre-
dicted for mid-century (Fig. 6A, C).
DISCUSSION
Our simulation results for changes in ASW
and dry days suggest that during spring, soils
will be wetter in the future across most sites in
the big sagebrush region. In contrast, soils in the
summer will be drier, with increases in summer
dry days and decreases in summer ASW
expected for most sites. Percent changes in
summer ASW were considerable and represent
decreases of between 27% and 50%, depending
on the region in question. The magnitude of
these changes differed across the distribution of
big sagebrush ecosystems. The largest increases
in spring ASW are expected for high-elevation
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PALMQUIST ET AL.
SB-Montane sites and the eastern and central
regions of the big sagebrush distribution (MZs 1
4; Figs. 4 and 7; Appendices S3, S7, and S11),
with no large changes in the number of spring
dry days predicted for most sites (Figs. 5 and 8;
Appendices S3, S8, and S11). The largest
decreases in summer ASW were projected for
warm, dry mid-elevation SB-Montane sites in the
central and west-central portions of our study
area (MZs 4 and 5), which are projected to have
only small increases in MAP in the future (Figs. 4
and 7; Appendices S3, S7, and S11). The number
of dry days both in the top and bottom soil layers
during the summer was projected to increase
rangewide, but particularly for SB-Montane and
SB-Steppe sites in the eastern and northern por-
tions of our study area (MZs 1, 2, and 4; Figs. 5
and 8; Appendix S11). Collectively, these results
suggest that most sites will be drier in the future
during the summer months, but especially mid-
to high-elevation sites in the northern half of our
study area.
Fig. 7. Percent changes in available soil water from 19802010 to 20302060 for each Sage-grouse Management
Zone in spring for top and bottom soil layers (A, B) and summer for top and bottom soil layers (C, D). Values
shown are the median (black horizontal line), rst and third quartiles (ends of the box), range (ends of the whis-
kers), and outliers (points) across all sites for each Management Zone for the median GCM. The number of GCMs
that agree on the direction of the change in the median value reported is shown just above the x-axis.
www.esajournals.org 14 November 2016 Volume 7(11) Article e01590
PALMQUIST ET AL.
Ecosystem responses to altered climate
SB-Montane ecosystems responded differently
to climate change than the drier ecosystems:
increases in spring soil moisture and decreases in
summer soil moisture were both greatest for
SB-Montane sites. Although these sites were
predicted to become drier during the summer,
habitat suitability for big sagebrush in SB-Mon-
tane sites may increase in the future due to war-
mer winter temperatures, which is a key factor
that limits big sagebrush regeneration at high
elevations (reviewed by Schlaepfer et al. 2014).
Fig. 8. Absolute changes in the number of dry days from 19802010 to 20302060 for each Sage-grouse Man-
agement Zone in spring for top and bottom soil layers (A, B) and summer for top and bottom soil layers (C, D).
Values shown are the median (black horizontal line), rst and third quartiles (ends of the box), range (ends of the
whiskers), and outliers (points) across all sites for each Management Zone for the median GCM. The number of
GCMs that agree on the direction (+,, 0) of the change in the median value reported is shown just above the
x-axis. For bottom layers in spring, all GCMs agree with the median prediction of 0.
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PALMQUIST ET AL.
In addition, SB-Montane sites are currently the
most mesic (Schultz 2006, Miller et al. 2011) and
the magnitude of decreases in ASW predicted by
mid-century will likely not put these sites outside
the range of suitability for big sagebrush
(Schlaepfer et al. 2012b). However, warmer tem-
peratures and wetter winter and spring condi-
tions could also result in SB-Montane sites
becoming increasingly suitable for invasive,
annual, cold-season grasses (e.g., cheatgrass,
Bromus tectorum), which are currently con-
strained by minimum winter temperatures and
limited in their distribution and abundance at
high elevations (Chambers et al. 2007, Concilio
et al. 2013, Compagnoni and Adler 2014).
SB-Steppe and SB-Shrubland responded simi-
larly and will likely continue to become drier in
the future. Although the changes predicted for
these ecosystems were smaller than for SB-
Montane, they will perhaps be more ecohydro-
logically signicant, leading to potential negative
impacts on big sagebrush regeneration and
survival. Despite smaller reductions in summer
ASW, SB-Steppe and SB-Shrubland will continue
to be the driest ecosystems in the future
(Appendix S1), which may make these portions
of the big sagebrush region more vulnerable to
drought-related mortality and increased re
frequency. Our ndings are consistent with other
studies that have suggested mesic big sagebrush
communities have greater resistance and
resilience to climate change, disturbance, and
invasion, than the drier ecosystems, due to
underlying differences in temperature, moisture,
productivity, and native plant diversity (Davies
et al. 2006, 2012, Miller et al. 2011, Chambers
et al. 2014a,b).
Sage-grouse management zone responses to
altered climate
Our simulation results suggest that the largest
increases in summer dry days and decreases in
summer ASW in the future are expected for the
northern half of the big sagebrush region (MZs 1,
2, 4, and 5), but especially for the Snake River
Plain (MZ 4) and Northern Great Basin (MZ 5).
This is concerning as these MZs contain the core
populations of greater sage-grouse, have the
highest reported bird densities, and encompass
substantial greater sage-grouse habitat (Connelly
et al. 2004, Manier et al. 2013). These regions
may become drier and potentially more
vulnerable by mid-century, despite predicted
increases in precipitation and wetter winter and
spring soil conditions. However, warmer temper-
atures, particularly in the northern portion of our
study area, may increase habitat suitability in
some cases, such as on mesic sites. In contrast,
smaller changes in soil water are expected for the
Southern Great Basin (MZ 3), the Columbia River
Basin (MZ 6), and the Colorado Plateau (MZ 7).
These areas are already the hottest and driest
portions of the big sagebrush region, with very
little stored water that could be subject to addi-
tional evaporative loss in the future and as such,
changes in ASW and dry days are expected to be
smaller. Despite smaller changes, sites in MZ 3,
MZ 6, and MZ 7 will remain among the driest
(Appendix S1), underscoring the potential for
elevated vulnerability for plant communities in
the southwestern United States (Gremer et al.
2015, Schlaepfer et al. 2015) to increased drought
intensity and frequency (Seager et al. 2007, Abat-
zoglou and Kolden 2011, Anderegg and Diffen-
baugh 2015). Throughout the range of big
sagebrush, our ndings of increases in summer
dry days and decreases in ASW are consistent
with other studies that have projected increased
aridity in the future across much of the western
United States (Seager et al. 2007, Rehfeldt et al.
2012). However, our results provide new insights
by considering spatial patterns using relevant
conservation and management units (MZs) and by
also considering differences in responses among
sites within the same region, according to their
underlying ecological conditions (Appendix S11).
Management implications
Changes in the magnitude of timing of soil
water availability forecasted here will likely
inuence disturbance regimes, invasion dynam-
ics, and their interactions in the future. Range-
wide, our simulations suggest wetter spring and
winter conditions, which could benet cheat-
grasss life history strategy (Prev
ey and Seastedt
2014, Bradley et al. 2016) and in tandem with
warming temperatures could open up new parts
of the big sagebrush range (e.g., high elevations,
higher latitudes), and result in increased re
activity (Westerling et al. 2006). Our simulations
indicate that the dry ecosystems (SB-Steppe,
SB-Shrubland) will become drier in the future,
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PALMQUIST ET AL.
perhaps making them even more re-prone and
less resistant and resilient to cheatgrass invasion
following re, with implications for restoration
success (Chambers et al. 2007, 2014a,b, Davies
et al. 2012). Currently, SB-Montane sites may be
more resistant and resilient to re and invasion,
but will likely become more vulnerable in the
future, with implications for habitat quality and
the re-return interval in higher elevation sites.
In addition, we expect that the eastern and north-
ern portions of our study area, where cheatgrass
is not currently as ubiquitous and abundant as it
is in the Great Basin (Bradley et al. 2016), will
become more susceptible to cheatgrass invasion
in the future, due to warmer and wetter winter
and spring conditions.
Our results suggest climate change adaptation
and management actions should differ according
to the ecosystem and geographic location in
question. SB-Montane ecosystems currently pro-
vide important summer and fall habitat for
greater sage-grouse (Connelly et al. 2000, Walker
et al. 2016), but could also begin to provide more
suitable winter habitat in the future, depending
on future temperature regimes and snow condi-
tions. In contrast, the drier ecosystems (SB-
Shrubland, SB-Steppe) will likely continue to
provide important winter habitat for greater
sage-grouse and other wildlife (Homer et al.
1993, Connelly et al. 2000), but may provide sub-
optimal habitat during the summer months in
the future due to drier conditions. Davies et al.
(2006) found that some SB-Steppe sites did not
currently meet the vegetation requirements in
recently developed greater sage-grouse habitat
guidelines (Connelly et al. 2004) and our results
suggest this trend may continue. Collectively,
our results and the work of others suggest new
areas of habitat suitability for big sagebrush, pri-
marily in high latitudes and high-elevation sites,
and decreased habitat suitability at low eleva-
tions in the southwest United States (Shafer et al.
2001, Schlaepfer et al. 2012c, 2015).
SB-Montane sites will potentially provide new,
suitable habitat for greater sage-grouse in the
future, while current habitat at low to mid-
elevations in the Southern Great Basin, Colorado
Plateau, and Columbia River Basin may be too
dry to support adequate regeneration, productiv-
ity, and plant diversity for greater sage-grouse in
the future. As such, management may benet
from concentrating resources in portions of the
big sagebrush region that may now be too cold
to provide year-round habitat for greater sage-
grouse and perhaps placing less priority on con-
servation of dry, low-elevation sites that will
have decreased suitability in the future for big
sagebrush. These insights may help target con-
servation and management efforts for multiple
agencies in big sagebrush ecosystems across their
spatial extent in the western United States to
enhance the abundance of big sagebrush habitat
in the context of global environmental change.
Finally, we present a spatial framework for
summarizing sub-continental climate change
impacts at the spatial scales at which manage-
ment and conservation is implemented, in our
case Sage-grouse Management Zones. We believe
this approach could be useful for managers sum-
marizing climate change impacts in a variety of
ecosystems that span broad spatial extents to
generate information to guide managers acting
at local to regional scales. In addition, we believe
our work has implications for understanding
how ecohydrology in other mid-latitude shrub
steppe ecosystems (e.g., Patagonia, Central Asia)
may respond to changing climatic conditions.
ACKNOWLEDGMENTS
The work was made possible by funding from the
University of Wyoming, the US Fish and Wildlife Ser-
vice, the North Central Climate Science Center, and
the US Department of Interior Geologic Survey. Any
use of trade, product, or rm names is for descriptive
purposes only and does not imply endorsement by the
U.S. Government. JBB was supported by the USGS
Ecosystems Mission Area.
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... In addition to integrating community dynamics, climate impact assessments should incorporate current and future spatial heterogeneity, especially in topographically complex regions. This is important as the outcome of changing precipitation and temperature regimes will not be uniform and plant communities are likely to respond differently depending on existing spatial heterogeneity and future heterogeneity in temperature and precipitation (Bradford et al., 2020;Palmquist et al., 2016b;Schlaepfer et al., 2017). For example, cold, moist locations at high elevations or latitudes may benefit from warming, due to an increase in growing season length and conditions that are more optimal for growth. ...
... In North America, temperate drylands are projected to experience increases in temperature and modest increases in cool-season precipitation on average with the largest increases in temperature and precipitation in the northernmost parts of the region (Bradford et al., 2020;Palmquist et al., 2016aPalmquist et al., , 2016b. Warming and increases in potential evapotranspiration are projected to increase the fraction of precipitation lost to evaporation during times of the year that currently have low evaporative demand (i.e., early spring and late fall), regardless of changes in precipitation. ...
... Reductions in soil moisture may make some areas unsuitable for the functional types that currently reside there by imposing additional stress for plants already near their physiological limits (Breshears et al., 2005;Renne, Schlaepfer, et al., 2019). In contrast, for temperate drylands at higher elevations and latitudes that are generally cold and moist, warmer temperatures will extend the growing season without decreasing (and potentially increasing) the suitability of conditions for plant growth, as long as adequate soil moisture is available (Palmquist et al., 2016b;Polley et al., 2013;Renwick et al., 2018;Schlaepfer et al., 2012a). Studies that have evaluated experimental warming (Perfors et al., 2003) and examined growth in response to climate variability ) support these predictions. ...
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... We caution, however, that these projections should be interpreted in the context of their underlying assumptions. We assumed 30-year averages for weather when making projections, corresponding with climatic conditions from which we fit sagebrush trend models, but these may differ from future growing conditions Palmquist et al., 2016;Renwick et al., 2017;Tredennick et al., 2016). ...
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... v www.esajournals.org 5 August 2021 v Volume 12(8) v Article e03695 Tietjen et al. 2017) and North American dry grasslands (e.g., Bradford et al. 2014b, Lauenroth et al. 2014, dry forests , and shrublands (e.g., Schlaepfer et al. 2012b, Palmquist et al. 2016b, Renne et al. 2019 including simulations under climate change projections (Schlaepfer et al. 2012a, c, 2015, Palmquist et al. 2016a). ...
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... evapotranspiration (Palmquist et al. 2016a). Drier late spring and summer conditions at mid and upper elevation in the northern distribution of sagebrush may maintain or increase suitability for big sagebrush, but those conditions may decrease suitability at lower elevations (Palmquist et al. 2016b). ...
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Chapter
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Amphibians and reptiles are vertebrates that are often overlooked in assessments of the importance of sagebrush (Artemisia spp.) ecosystems for wildlife. Given their dependence on water, few amphibians are strongly associated with sagebrush habitats, although several use these uplands for foraging, shelter, or dispersal. Of the 60 amphibian species that are predicted to occur within the sagebrush biome, the Great Basin spadefoot (Spea intermontana) is probably the only species that occupies enough of the biome and lives predominantly in terrestrial habitats (mostly in burrows) to be considered sagebrush associated. Of the 116 reptiles that are predicted to occur within the sagebrush biome, about 5 lizards and 5 snakes were identified as both strongly associated with sagebrush habitats and occupied areas likely to be managed for sage-grouse (Centrocercus spp). However, this list could be lower or higher depending on the specific location within the biome, and there remains considerable uncertainty regarding potential threats to reptiles, as well as basic information on distribution and abundance of most reptile species.
Chapter
Full-text available
Adaptive management and monitoring efforts focused on vegetation, habitat, and wildlife in the sagebrush (Artemisia spp.) biome help inform management of species and habitats, predict ecological responses to conservation practices, and adapt management to improve conservation outcomes. This chapter emphasizes the adaptive resource management framework with its four stages: (1) problem definition, (2) outcomes, (3) decision analysis, and (4) implementation and monitoring. Adaptive resource management is an evolving process involving a sequential cycle of learning (the accumulation of understanding over time) and adaptation (the adjustment of management over time). This framework operationalizes monitoring a necessary component of decision making in the sagebrush biome. Several national and regional monitoring efforts are underway across the sagebrush biome for both vegetation and wildlife. Sustaining these efforts and using the information effectively is an important step towards realizing the full potential of the adaptive management framework in sagebrush ecosystems. Furthermore, coordinating monitoring efforts and information across stakeholders (for example, Federal, State, nongovernmental organizations) will be necessary given the limited resources, diverse ownership/management, and sagebrush biome size.
Technical Report
Full-text available
USGS sage-grouse and sagebrush ecosystem research is aligned with priority needs outlined in the “Integrated Rangeland Fire Management Strategy Actionable Science Plan” (Integrated Rangeland Fire Management Strategy Actionable Science Plan Team, 2016). The list of 116 research projects is organized into five thematic areas: fire (16 projects); invasive species (7 projects); restoration (23 projects); sagebrush, sage-grouse, and other sagebrush-associated species (60 projects); and weather and climate (10 projects). Individual projects often overlap multiple themes (for example, effects of wildfire and invasive annual grasses on greater sage-grouse habitat); therefore, project descriptions are organized according to the main focal theme.
Technical Report
Full-text available
USGS sage-grouse and sagebrush ecosystem research is aligned with priority needs outlined in the “Integrated Rangeland Fire Management Strategy Actionable Science Plan” (Integrated Rangeland Fire Management Strategy Actionable Science Plan Team, 2016). The list of 116 research projects is organized into five thematic areas: fire (16 projects); invasive species (7 projects); restoration (23 projects); sagebrush, sage-grouse, and other sagebrush-associated species (60 projects); and weather and climate (10 projects). Individual projects often overlap multiple themes (for example, effects of wildfire and invasive annual grasses on greater sage-grouse habitat); therefore, project descriptions are organized according to the main focal theme.
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