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Current reclamation practices after oil and gas development do not speed up succession or plant community recovery in big sagebrush ecosystems in Wyoming

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Reclamation is an application of treatment(s) following disturbance to promote succession and accelerate the return of target conditions. Previous studies have framed reclamation in the context of succession by studying its effectiveness in reestablishing late-successional plant communities. Reestablishment of plant communities is especially important and challenging in drylands such as shrub steppe ecosystems where succession proceeds slowly. These ecosystems face threats from climate change, invasive species, altered fire regimes, and land-use change, as well as fossil-fuel extraction and associated disturbance. As such, the need for effective reclamation after this type of energy development is great. However, past research regarding this type of reclamation has focused on mining rather than oil and gas development. To better understand the effect of reclamation on rates of succession in dryland shrub steppe ecosystems, we sampled oil and gas wellpads and adjacent undisturbed big sagebrush plant communities in Wyoming, U.S.A., and quantified the extent of recovery for forbs, grasses, and shrubs on reclaimed and unreclaimed wellpads relative to undisturbed plant communities. Reclamation increased the recovery rate for early-successional types, including combined forbs and grasses and perennial grasses, but did not affect recovery rate of late-successional types, particularly big sagebrush and perennial forbs. Rather, subsequent analyses showed that recovery of late-successional types was affected by soil texture and time since wellpad abandonment. This is consistent with studies in other ecosystems where reclamation has been implemented, suggesting that reclamation may not help reestablish late-successional plant communities more quickly than they would reestablish naturally.
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RESEARCH ARTICLE
Current reclamation practices after oil and gas
development do not speed up succession or plant
community recovery in big sagebrush ecosystems in
Wyoming
Caitlin M. Rottler1,2,3,4,, Ingrid C. Burke1,2,3,, Kyle A. Palmquist3, John B. Bradford5, William K.
Lauenroth3,
Reclamation is an application of treatment(s) following disturbance to promote succession and accelerate the return of target
conditions. Previous studies have framed reclamation in the context of succession by studying its effectiveness in reestablishing
late-successional plant communities. Reestablishment of plant communities is especially important and challenging in drylands
such as shrub steppe ecosystems where succession proceeds slowly. These ecosystems face threats from climate change, invasive
species, altered re regimes, and land-use change, as well as fossil-fuel extraction and associated disturbance. As such, the
need for effective reclamation after this type of energy development is great. However, past research regarding this type
of reclamation has focused on mining rather than oil and gas development. To better understand the effect of reclamation
on rates of succession in dryland shrub steppe ecosystems, we sampled oil and gas wellpads and adjacent undisturbed big
sagebrush plant communities in Wyoming, U.S.A., and quantied the extent of recovery for forbs, grasses, and shrubs on
reclaimed and unreclaimed wellpads relative to undisturbed plant communities. Reclamation increased the recovery rate
for early-successional types, including combined forbs and grasses and perennial grasses, but did not affect recovery rate of
late-successional types, particularly big sagebrush and perennial forbs. Rather, subsequent analyses showed that recovery of
late-successional types was affected by soil texture and time since wellpad abandonment. This is consistent with studies in other
ecosystems where reclamation has been implemented, suggesting that reclamation may not help reestablish late-successional
plant communities more quickly than they would reestablish naturally.
Key words: chronosequence, energy development, reclamation, species richness, succession
Implications for Practice
Current reclamation is expensive and is an assumed
requirement for returning a site to an undisturbed,
late-successional condition.
Prior research suggests that big sagebrush plant commu-
nities and other shrub steppe communities do not recover
more quickly when they are reclaimed with current prac-
tices.
Forbs and sagebrush did not respond to modern reclama-
tion, while perennial grasses and rabbitbrush did respond.
Both reclaimed and unreclaimed sites recovered similarly,
indicating that current reclamation may not be signi-
cantly impacting recovery to promote plant communities
similar to an undisturbed state.
Introduction
Reclamation is an attempt to manipulate or replace natural,
unaided succession, to promote the restoration of disturbed
ecosystems to a target condition (Prach et al. 2007). Reclama-
tion and succession have been studied in the context of various
disturbances, including mined land in the eastern United States,
England, Scotland, and Wales (Bradshaw 1984; Brenner et al.
1984; Bradshaw 1997; Bradshaw 2000; Prach & Hobbs 2008),
highly eroded and essentially bare soils in Iceland (Gretarsdottir
et al. 2004), degraded or drained wetlands in the southeast and
central United States (Kusler & Kentula 1989), and oil and gas
Author contributions: CMR, ICB, WKL conceived and designed the research; CMR
performed the study; CMR, KAP, WKL, and JBB analyzed the data; CMR wrote the
manuscript; ICB, KAP, JBB, WKL edited the manuscript.
1Haub School of Environment and Natural Resources, University of Wyoming,
Laramie, WY 82071, U.S.A.
2Program in Ecology, University of Wyoming, Laramie, WY 82071, U.S.A.
3Department of Botany, University of Wyoming, Laramie, WY 82071, U.S.A.
4Address correspondence to C. M. Rottler, email caitlin.rottler@ars.usda.gov
5Southwest Biological Science Center, US Geological Survey, Flagstaff, AZ 86001,
U.S.A.
Present address: US Department of Agriculture, Agricultural Research Station,
Grazinglands Research Laboratory, El Reno, OK 73036, U.S.A.
Present address: YaleSchool of Forestry and Environmental Studies, Yale University,
New Haven, CT 06511, U.S.A.
© 2017 Society for Ecological Restoration
doi: 10.1111/rec.12543
Supporting information at:
http://onlinelibrary.wiley.com/doi/10.1111/rec.12543/suppinfo
Restoration Ecology 1
Reclamation and sagebrush plant community recovery
development in the western United States (Avirmed et al. 2015).
In these contexts, reclamation utilizes treatments, including soil
stockpiling and respreading, tilling, and seeding to hasten the
recovery of ecosystem structure and processes to a state similar
to that of nearby undisturbed areas. Its ability to replace or aug-
ment successional processes that occur during the natural course
of recovery from disturbances is of particular interest where nat-
ural succession is slow due to resource limitation (e.g. water
availability in drylands).
Globally, drylands cover about 40% of the land’s surface
(Schlaepfer et al. 2017). They are widespread and they provide
a number of essential ecosystem services to a growing human
population (Field et al. 2010). Shrub steppe ecosystems are a
common type of dryland ecosystem that occupy the western
United States, southeastern South America, and a large portion
of central Asia. Winter is the wet season in these shrub steppe
plant communities, which results in spring recharge of soil
water deep in the soil (Lauenroth et al. 2014; Palmquist et al.
2016a). As a result of their ability to take advantage of these
deeply stored water sources, shrubs are the dominant growth
form in these ecosystems. In the western United States, shrub
steppe ecosystems are dominated by big sagebrush (Artemisia
tridentata) with an understory of grasses, forbs, and subshrubs.
They presently provide habitat for approximately 350 plant
and animal species of conservation concern, including sage-
brush obligates such as the Greater Sage-Grouse (Centrocercus
urophasianus), a species that was recently considered for listing
on the Endangered Species Act (Davies et al. 2011).
Shrub steppe ecosystems are frequently associated with
regions rich in energy resources (oil, gas, coal, wind, solar,
geothermal; Pocewicz et al. 2011), such that up to 25% of west-
ern North American shrub steppe is projected to be affected
by energy development in the future (Pocewicz et al. 2011).
In addition to oil and gas development, big sagebrush shrub
steppe is increasingly threatened by climate change, invasion
by exotic species, altered re regimes, and other changes in
land use (Knick et al. 2003; Bradley 2010; Manier et al. 2013;
Palmquist et al. 2016a, 2016b; Schlaepfer et al. 2017). As such,
the need for reclamation and restoration of dryland plant com-
munities after oil and gas development and other disturbances
is growing and will continue into the future.
The disturbance related to oil and gas development is due to
wellpads and their associated roads and pipelines. Oil and gas
wellpads are approximately 40 m or larger in diameter where
wells have been established and maintained. To drill a well, the
area is typically cleared of all vegetation, resulting in destruc-
tion of the plant community. Furthermore, the network of roads
connecting wellpads, as well as pipelines to transport oil and
gas, can be extensive, with potential effects on biodiversity and
ecosystem processes. To mitigate some of these effects, well-
pads are reclaimed with the intent of reestablishing the native
plant community to an undisturbed state. Seed mixes containing
late-successional species are used during reclamation to encour-
age bypassing of early-successional states.
The success of reclamation in various ecosystems worldwide,
including shrub steppe, is poorly understood. Where studies on
the success of reclamation have occurred, they have primar-
ily followed re. For example, Fernández-Abascal et al. (2004)
were unable to detect any signicant effect of reclamation on
plant community structure 10 years after re in a Mediterranean
heathland. Recovery of native plant communities in a burned
northern California forest was likewise not facilitated by recla-
mation efforts (Kruse et al. 2004). Studies in burned sagebrush
steppe plant communities indicate that big sagebrush can take
from 35100 years or more to reestablish after a re, depend-
ing on the subspecies (Baker 2006), while a study on oil and
gas wellpads found that native forbs did not recover as readily
as grasses (Avirmed et al. 2015). Because forbs represent the
majority of species richness in big sagebrush shrub steppe plant
communities, their very slow recovery represents a signicant
challenge in restoring overall community structure.
To understand how reclamation can affect the rate of plant
community recovery and community composition, both above-
ground and belowground, in North American shrub steppe
ecosystems, we compared plant communities and the soil seed-
bank on reclaimed and unreclaimed wellpads in big sagebrush
ecosystems in southwestern Wyoming. We characterized differ-
ences in the number and identity of seeds in the seedbank to
document the impact of reclamation on potential future recovery
of different plant functional groups. We also explored how other
site factors, such as soil texture, precipitation post abandonment,
and time since abandonment, inuenced recovery. Approxi-
mately half of the wellpads we studied had received reclamation
treatments (hereafter referred to as “reclaimed”). The treatments
consisted of returning the topsoil, preparation of the soil surface
for planting, and broadcasting of seed mixes over the wellpad.
Our remaining wellpads were not reclaimed; after they were
abandoned, no further effort was made to replace topsoil or
encourage plant reestablishment (unreclaimed). Each wellpad
was paired with an adjacent undisturbed site, as in Avirmed et al.
(2015). We compared differences on reclaimed and unreclaimed
wellpads in relation to undisturbed communities to answer three
questions: (1) How similar are recovering plant communities
and soil seedbanks on wellpads to undisturbed plant communi-
ties? (2) Do reclamation and natural succession (no reclamation)
result in similar plant communities and seedbanks? and (3) Does
reclamation increase the rate of recovery compared to natural
succession? We predicted that reclamation and natural succes-
sion would both result in similar communities to those that were
undisturbed, but that the rate of recovery would be faster on
reclaimed than unreclaimed wellpads. We hypothesized that cli-
mate and time since reclamation were most likely to inuence
reclamation success.
Methods
Site Description and Selection
Our study area was located south of Rock Springs, Wyoming, in
the South Baxter Basin (41.28N, 109.36W). Soils in this area
are ustic haplargids, or moderately dry soils with poorly dened
horizons that are primarily argillic in nature (Munn & Arneson
1998). The mean annual temperature is approximately 6C with
2Restoration Ecology
Reclamation and sagebrush plant community recovery
a mean minimum of 0C and a mean maximum of 13C, and the
mean annual precipitation is approximately 22 cm. We selected
19 sites that were abandoned from production between 1943
and 2007. Each site consisted of a pair of plots: an abandoned
wellpad (all equipment removed), 40 m in diameter, and an
adjacent undisturbed control plot of the same size. Nine of the
wellpads were abandoned after 1983 (between 7 and 31 years
since abandonment) and represented reclaimed wellpads, while
10 were abandoned prior to 1983 (between 32 and 66 years
since abandonment) and represented unreclaimed wellpads. We
chose the cut-off date of 1983 because this was the year that
reclamation was rst mandated and enforced in Wyoming,
and therefore the earliest we could expect reclamation to have
occurred. This resulted in all reclaimed wellpads being younger
than unreclaimed wellpads.
Plant Community Sampling
At each site, we used 30 randomly located 0.5 m by 0.2 m
quadrats and two 40 m by 1.5 m belt transects to sample the
plant community. Within each quadrat, we estimated percent
canopy cover of each forb or grass species using a scale modied
from Daubenmire (1959) to increase detection of rare species
(T =<1%; 1 =1–5%, 2=6 –15%, 3 =16 –25%, 4 =2640%,
5=4160%, 6 =>60%). We established the belt transects per-
pendicular to one another through the center of the plot (Fig. 1).
Within the belt transects, we counted and identied each forb
and shrub species and measured canopy length and width of at
least 10% of the individuals of three target shrub species: big
sagebrush (Artemisia tridentata), black sagebrush (Artemisia
nova), and rabbitbrush (Chrysothamnus viscidiorus), selected
randomly approximately every 5 m along the belt transects.
Canopy measurements were used to determine canopy area of
shrubs (Cleary et al. 2008). We sampled the plant community
using the same methods for both the wellpad and the paired
undisturbed site.
Soil Seedbank Sampling
To understand if there were differences in seedbanks between
reclaimed, unreclaimed, and undisturbed sites, we collected
three sets of soil seedbank samples from each wellpad and
undisturbed plot. Each set consisted of two 6.5 cm diameter soil
cores collected to a 5 cm depth: one from the interspace between
shrubs and one from under the canopy of a shrub. Each set was
located randomly within an interval from the center: 0– 7 m,
713 m, and 13– 20 m (Fig. 1). After returning to the laboratory,
we processed samples using a modication of the method used
by Martyn et al. (2016). We sieved all samples through a 2-mm
sieve to remove rocks and plant material. We then spread a
mix of two parts sand to three parts potting soil 5 cm deep in
greenhouse trays to provide a suitably deep growth medium. The
potting soilsand mix was covered with a thin layer of polyester
fabric to maintain separation between seedbank samples and the
potting soil/sand without hindering root growth or emergence
of seedlings. Sample soils were spread to a uniform thickness
over the polyester and watered twice daily. Once a week for 25
13-20m
7-13m
0-7m
Figure 1. Plot design. Diagram of eld plots, with seedbank sampling
locations indicated with “X” and belt transects indicated with shaded
bands. Seedbank samples were collected at three different distances from
the center of the plot to ensure representation of the seedbank at various
distances from undisturbed communities. Location of the seedbank sample
was random within each distance range.
weeks, we counted and identied plants in each sample. At the
conclusion of the study, we used the gravimetric method from
Malone (1967) to separate organic matter from the soil, which
we then examined for ungerminated seeds.
Soil Texture
We sampled soils at each site to determine their texture. At
each seedbank sample location, we also collected three soil
cores for texture analysis corresponding to three locations:
interspace (B), under shrub canopies (U), and on the mound
formed by a bunchgrass (M). At B, we took samples to three
depths: 05, 510, and 1030 cm. At U and M, we took
samples to two depths: 05 and 5–10 cm. We composited
50 g of each sample by plot, depth, and location, resulting in
one sample/depth/location/plot. We then used the hydrometer
method to determine the percent sand, silt, and clay of each
sample (Gee & Bauder 1986).
Data Analysis
Similarity Analyses. All analyses were performed in R version
3.2.2 using the “vegan” package (Oksanen et al. 2015; R Core
Team 2015). We used two methods to quantify recovery on
wellpads: one for functional groups and another for shrub cover.
For functional groups (perennial or annual grasses, perennial or
annual forbs, all grasses and forbs, and shrubs), we summarized
recovery using Bray– Curtis similarity. For shrub cover, we used
Restoration Ecology 3
Reclamation and sagebrush plant community recovery
a recovery index (RI) to compare percent cover of shrub species
on wellpads and adjacent undisturbed sites.
We calculated BrayCurtis similarity (Bray & Curtis 1957)
for all wellpads and adjacent undisturbed sites separately for
annual forbs, perennial forbs, perennial grasses, and shrubs
using percent cover calculated from quadrats and shrub canopy
measurements. Similarity values reected how similar the veg-
etation on the wellpad was to its adjacent undisturbed big
sagebrush plant community. We then calculated the median
similarity of undisturbed plots to their respective wellpad
(within-pair similarity) for functional groups: annual forbs,
perennial forbs, perennial grasses, and all shrubs. The “all
shrubs” group allowed us to account for shrub species that we
were unable to include in our species-specic shrub analyses
due to their rarity of occurrence and to understand how shrub
species responded collectively to reclamation. We also calcu-
lated BrayCurtis similarity for combined forbs and grasses to
better understand the understory at the community scale. We did
not calculate similarity values for annual grasses due to their low
occurrence.
In addition to within-pair similarities, we calculated sim-
ilarity among all undisturbed sites to represent the baseline
similarity that could reasonably be expected due to natural varia-
tion in intact communities (undisturbed similarity). We used the
median undisturbed similarity to interpret the degree of recov-
ery of our wellpad plant communities. We compared the median
within-pair similarity of all wellpads to the median similarity of
all undisturbed plots to determine if grass, forb, and shrub func-
tional types had recovered across the study area. To address the
effect of reclamation on community composition and recovery,
we grouped reclaimed and unreclaimed wellpads and compared
the functional type similarities within each group to the median
undisturbed similarities.
To understand species-specic responses for shrubs, which
are the dominant functional type in these ecosystems, we used
species-specic data for big sagebrush, rabbitbrush, and black
sagebrush. While other shrub species were used in the func-
tional group similarity analyses, their rarity of occurrence on
both wellpads and undisturbed sites prevented their use in
species-specic comparisons. For each big sagebrush, rabbit-
brush, and black sagebrush, we compared percent cover on well-
pads and undisturbed plots using a RI, which was calculated
using the following formula:
Percent cover on wellpad
Percent cover on undisturbed =RI
A RI of 1 or greater indicated equal or higher cover on the
wellpad than the undisturbed plot and less than 1 indicated
greater cover on the undisturbed plot than the wellpad. To
determine the extent of recovery of shrubs across the study area
and between reclaimed and unreclaimed sites, we calculated
median RI for each and assumed that 1 or greater indicated
full recovery, while anything less than 1 indicated only partial
recovery. We did not calculate recovery indices for forb and
grass species due to low presence of individual forb and grass
species across all sites.
To analyze seedbank characteristics, we summed the total
number of emerged seedlings and divided this by the sum of
emerged seedlings and ungerminated seeds, then multiplied by
100 to determine average percent emergence on all wellpads
and undisturbed plots. In addition, we calculated percentage of
grasses, forbs, and shrubs of all seedlings that emerged within
each plot. We then compared percent emergence and percent
contribution of each functional type across all wellpads and all
undisturbed plots as well as between reclaimed and unreclaimed
wellpads.
Effect of Reclamation, Time, and Environmental Factors.
To determine which factors were most closely correlated with
extent of recovery of plant communities across the study area,
we calculated Kendall’s 𝜏-b correlations using the R stats pack-
age (R Core Team 2015). Kendall’s 𝜏-b is a nonparametric rank
correlation test used to calculate the extent to which two vari-
ables are correlated by ordering data and comparing the order
of one variable to the other (Kendall 1955). The range of the
rank correlation coefcient is between 1 and 1, where 1 indi-
cates an inverse relationship between the two variables, 0 rep-
resents no relationship, and 1 represents a positive relationship
between the two variables. We calculated correlations between
within-pair similarity or RI for each functional type or shrub
species; percent sand, silt, and clay from our soil samples; years
since abandonment; and winter precipitation totals for 1, 3,
and 5 years post-abandonment (NOAA National Climate Data
Center 2016).
To determine if reclamation treatment affected the rate of
recovery of plant communities, we calculated a rate of recov-
ery for each functional type or shrub species by dividing
each similarity or RI by the number of years since abandon-
ment of each wellpad. We compared the rates of recovery
using a MannWhitney test (Mann & Whitney 1947). The
MannWhitney test is a nonparametric two-sample test simi-
lar to a conventional ttest, but does not require an assumption
of normal distributions of the two samples. Similar to a ttest, a
signicant difference between two populations is indicated with
ap-value. For visual comparison of rates of recovery, we also
calculated a median rate of recovery for each functional type or
shrub species and graphed these against the rates of recovery.
Results
Similarity of Plant Communities on Wellpads and Undisturbed
Plots
We found a total of 78 forb, grass, and shrub species across all
sample locations; of these, 72 were forb or grass species, and 10
of these were classied as introduced or potentially introduced
to Sweetwater county according to the USDA Plants database
(see Table S1, Supporting Information, for a list of all forb and
grass species). Five of these introduced or potentially introduced
species (Achillea millefolium,Halogeton glomeratus,Hyoscya-
mus niger,Polygonum aviculare,andTaraxacum ofcinale)
occurred only on wellpads, while the other ve species occurred
on both wellpads and undisturbed plots.
4Restoration Ecology
Reclamation and sagebrush plant community recovery
0
20
40
60
80
Perennial Forbs
n=17 Annual Forbs
n=8Perennial Grass
n=19 All Forbs
and Grasses
n=19
All Shrubs
n=17
Similarity (%)
Figure 2. Similarity of functional type covers between wellpads and
paired undisturbed plots. Each species in our study was divided into one of
four functional types. For each wellpad-undisturbed pair, we calculated
similarity between functional types. Boxes encompass the 75th and 25th
percentiles, whiskers represent the 5th and 95th percentiles, individual
points represent outliers, and solid lines are the median similarity between
wellpads and their paired undisturbed plot. Wide dashed lines represent the
median similarity among all undisturbed plots for the given functional
type, and narrow dashed lines represent the 75th and 25th percentiles for
similarity among all undisturbed plots.
Similarity between paired wellpad and undisturbed plots
(within-pair similarity) was less than median similarity among
undisturbed plots (undisturbed similarity) for all functional
types (Fig. 2). Variability for annual forbs and shrubs was high:
within-pair similarity varied from 0 to 80% for the annual forb
functional group and from 0 to 85% for the shrub functional
group. The range of within-pair similarities for the remaining
groups was smaller than for shrubs and annual forbs: 065%
for perennial forbs, approximately 1080% for perennial grass,
and approximately 560% for all nonshrub functional types.
Perennial grasses and the nonshrub functional group (combined
grass and forb functional types) recovered to some extent on all
sites (similarity >0%), while perennial and annual forbs, when
considered as distinct functional groups, showed no recovery on
one or more wellpads (similarity =0%). The low abundance of
annual grasses (primarily Bromus tectorum in this region) pre-
cluded their use in analyses, while the abundance of Agropyron
cristatum (a common species in reclamation seed mixtures) was
a primary contributor to results for perennial grasses.
Recovery of individual shrub species, measured by RI, was
variable. The median RI for wellpads on which Artemisia nova
was found (n=5) was less than 1, as were all individual wellpad
RIs; the median RI of Artemisia tridentata (n=16) was slightly
greater than 1, but individual wellpad RIs ranged above and
below 1; and the median RI of Chrysothamnus viscidiorus
(n=17) was greater than 1, as were the majority of wellpad RIs
(Fig. 3).
0
2
4
6
8
A.nova A.tridentataC.viscidiorus
Recovery Index
Figure 3. Recovery of shrub species cover on wellpads. For each major
shrub species in the “shrub” functional type, we calculated a RI comparing
cover within wellpad-undisturbed pairs. The dotted line represents a RI of
1, or no difference in percent cover between wellpads and their paired
undisturbed plot. Values above 1 indicate percent cover on the wellpad was
equivalent to or exceeded the percent cover for that shrub species on the
paired undisturbed site. Values below 1 indicate the opposite. Boxes and
whiskers represent the 75th percentiles and 95th percentiles, individual
points represent outliers, and solid lines are the median similarity between
wellpads and their paired undisturbed plot.
Tabl e 1 . Number of emergents and residual seeds in the seedbank.
Grass Forb Shrub
Tot a l
Seedlings
Total Seeds
+Seedlings
Undisturbed 993 73 1 1,067 1,155
Wellpad 407 180 5 592 830
Unreclaimed 338 37 4 379 468
Reclaimed 69 143 1 213 362
Total 1,400 253 6 1,659 1,985
Percent emergence of seeds in soil samples from wellpads
was lower than the undisturbed average (87%) for 13 of 19 sites.
Approximately twice as many seeds emerged in undisturbed
samples as in wellpad samples (Table 1). Emerging plants
were disproportionately represented by grass species; 84% of
seedlings were grasses, compared to 15% and <1% for forbs
and shrubs, respectively.
Similarity Within Pairs for Reclaimed and Unreclaimed
Wellpads
Of the 72 species of forbs and grasses we encountered, 21
occurred only on unreclaimed wellpads (Table S1). Eleven
species occurred only on reclaimed wellpads, and four of these
were introduced: A. millefolium,B. tectorum,Ceratocephala
testiculata,andH. niger (Table S1).
Median within-pair similarity was higher on unreclaimed
than reclaimed wellpads for perennial grasses, perennial forbs,
Restoration Ecology 5
Reclamation and sagebrush plant community recovery
0
20
40
60
80
Perennial Forbs
n=17 Annual Forbs
n=8Perennial Grass
n=19 All Forbs
and Grasses
n=19
All Shrubs
n=17
Similarity (%)
Reclaimed Unreclaimed
Figure 4. Similarity of functional type cover within reclaimed and
unreclaimed wellpad-control pairs. Boxes encompass the 75th and 25th
percentiles, whiskers represent the 5th and 95th percentiles, individual
points represent outliers, and solid lines are the median similarity between
wellpads and their paired undisturbed plot. Wide dashed lines represent the
median similarity among all undisturbed plots for the given functional
type, and narrow dashed lines represent the 75th and 25th percentiles for
similarity among all undisturbed plots.
and shrubs (Fig. 4), which account for the bulk of species in
big sagebrush plant communities. Similarity was lower on
unreclaimed versus reclaimed wellpads for annual forbs and for
all nonshrub functional types when analyzed together. Variation
in similarity was greatest for reclaimed wellpads regardless
of functional type (Fig. 4). All individual shrub species had
higher median recovery indices on unreclaimed than reclaimed
wellpads. In the case of A.tridentata, the median RI for unre-
claimed wellpads was greater than 1 (approximately 1.3) and
for reclaimed wellpads it was less than 1 (approximately 0.7;
Fig. 5). The median RI for C.viscidiorus was greater than 1
for both reclaimed and unreclaimed wellpads, and for A.nova
both RIs were lower than 1.
While seedlings emerged on 18 of 19 wellpads, the total
number of seedlings was greater on unreclaimed than reclaimed
wellpads. More grass and shrub seeds emerged on unreclaimed
than reclaimed wellpads, but the reverse was true for forbs,
likely due to the disproportionate presence of annual forbs on
reclaimed wellpads (Table 1).
Environmental Factors, Reclamation, Time, and Plant
Community Recovery
Kendall’s 𝜏-b correlations showed only a single signicant
correlation between within-pair similarity and environment or
reclamation: that of forb and grass species richness with percent
silt (𝜏=0.058, p=0.036). There were no signicant correla-
tions between years since abandonment and any plant commu-
nity response variable. The Mann– Whitney tests for differences
0
2
4
6
8
A.nova A.tridentataC.viscidiorus
Recovery Index
Reclaimed Unreclaimed
Figure 5. Recovery of shrub species cover on reclaimed and unreclaimed
wellpads. The dotted line represents a RI of 1, or no difference in percent
cover between wellpads and their paired undisturbed plot. Values above 1
indicate that percent cover on wellpads exceeded percent cover on the
paired undisturbed plot, while values below 1 indicate the opposite. Boxes
and whiskers represent the 75th percentiles and 95th percentiles, individual
points represent outliers, and solid lines are the median RI.
in recovery rates (recovery over time) indicated higher recov-
ery rates on reclaimed wellpads for grasses and forbs when
combined (U=75, p=0.01; Fig. 6A & 6B) and for perennial
grasses (U=75, p=0.01; Fig. 6G & 6H), but no difference
in rates for the shrub functional type or forb functional type
(Fig. 6CF) or for either A.tridentata (Fig. 7A & 7B) or C.
viscidiorus (Fig. 7C & 7D).
Discussion
Our study assessed how reclamation inuenced succession
within big sagebrush steppe plant communities that were dis-
turbed by oil and gas development. We predicted that while
succession would occur on all wellpads, the rate of succession
would be greater on reclaimed than unreclaimed wellpads. Our
prediction was partially supported in that succession occurred
on most wellpads, as indicated by within-pair similarity and the
RI. In addition, reclamation increased rate of recovery for peren-
nial grasses and combined grasses and forbs. However, this
response was most likely driven by the exotic species, Agropy-
ron cristatum. Conversely, reclamation did not positively affect
therateofrecoveryofArtemisia tridentata or perennial forbs.
Failure of reclamation to promote the recovery of the domi-
nant shrub species, A.tridentata, underscores the challenge of
restoring long-lived, late-successional species in dryland envi-
ronments. Furthermore, the lack of a positive perennial forb
response to reclamation has important implications for recovery
of plant species richness, because forbs account for the bulk of
the biodiversity in big sagebrush plant communities (Anderson
& Inouye 2001).
6Restoration Ecology
Reclamation and sagebrush plant community recovery
Reclaimed Unreclaimed
0
20
40
60
80
0
20
40
60
80
0
20
40
60
80
0
20
40
60
80
Combined Forbs + Grass
n=19
All Shrubs
n=17
Perennial Forbs
n=17
Perennial Grass
n=19
Years Since Abandonment
Similarity (%)
p=0.01
p=0.01
0 25 50 75 0 25 50 75
(A) (B)
(C) (D)
(E) (F)
(G) (H)
Figure 6. Rates of recovery of perennial functional types, shrubs, and
combined forbs and grasses on reclaimed and unreclaimed wellpads. Rates
of change of perennial forb functional types and shrubs on individual
wellpads are represented by colored points and lines, and the dashed line
represents the median recovery rate of all sites. Combined forb and grass
species (A) recovered signicantly faster in reclaimed versus unreclaimed
wellpads as indicated by a Mann– Whitney test, as did perennial grasses
([G]; p=0.01). Annual forbs are not included, as there were too few points
to construct a rate of recovery for that functional type.
We found a number of nonnative species in both undis-
turbed and wellpad plant communities. Nonnative species can
be introduced either intentionally by inclusion in reclamation
seed mixes or unintentionally during wellpad development and
operation. Their inclusion in reclamation seeding mixes is con-
troversial, because some nonnative plants have the ability to
become invasive or to lead to alternate stable states (Ewel &
Putz 2004; Vaness & Wilson 2007). However, they may also
serve as nurse plants or as early colonizers that outcompete less
desirable species (Ewel & Putz 2004) or inhibit soil loss (Allen
1995; D’Antonio & Meyerson 2002). In many parts of the range
of big sagebrush ecosystems, Bromus tectorum is an invasive
species that can form a persistent monoculture. B.tectorum was
present in only one of our sites, a reclaimed wellpad and its
associated undisturbed plot, indicating that it is not currently a
signicant problem in this area. Conversely, A.cristatum,which
was commonly planted on wellpads when reclamation was rst
required, was found on multiple reclaimed wellpads and some of
the adjacent undisturbed plots. It is also likely that the high cover
of A.cristatum was a major contributor to the signicant effect
of reclamation on the perennial grass group, and that this also
Reclaimed Unreclaimed
0
2
4
6
8
0
2
4
6
8
A.tridentataC.viscidiorus
Years Since Abandonment
Recovery Index
(a) (b)
(d)
(c)
0 25 50 75 0 25 50 75
Figure 7. Rates of recovery of shrub species on reclaimed and
unreclaimed wellpads. Rates of change of recovery indices for shrub
species on individual wellpads are indicated by points and colored lines,
and the dashed line represents the median recovery rate of all sites. There
were no signicant differences in rate of recovery between unreclaimed
and reclaimed wellpads for either shrub species.
drove the signicant response to reclamation in the combined
forb and grass species group. On the wellpads where A.crista-
tum had been seeded, abundance of other grass, shrub, and forb
species was very low, suggesting that these wellpads may have
reached an alternate state rather than the intended natural state.
This phenomenon is not limited to A.cristatum in reclamation
seed mixes (Gunnell et al. 2010; Morris et al. 2014, and others),
but rather is a characteristic of introduced perennial grasses, as
noted by other researchers in the western United States (Mar-
lette & Anderson 1986; Redente et al. 1989; Lesica & DeLuca
1996; and others), as well as in South America, Australia, and
the Pacic Islands (D’Antonio & Vitousek 1992). It is unclear
if the wellpads dominated by A.cristatum will be able to sup-
port subsequent successional states, or if the A.cristatum state
will persist. However, the lack of native plant community recov-
ery on these sites as well as the success of introduced perennial
grasses in other ecosystems suggest that while certain intro-
duced species may be preferable for a variety of reasons (as
livestock forage or soil stabilization), the effects of their inclu-
sion in reclamation seed mixes should be carefully monitored.
Studies of succession in shrubland ecosystems of the
Mediterranean and southwestern U.S. deserts have found that
annuals are abundant in early succession (Calvo et al. 2002;
Keeley et al. 2005; Abella 2010), consistent with our results in
big sagebrush plant communities. Our study found annual forbs
on only eight wellpads, but where they did occur, they were
on recently disturbed wellpads. In addition to annual forbs,
Chrysothamnus viscidiorus and relatives in the Ericameria
and Gutierrezia genera in the western United States readily
resprout after disturbances (Bates et al. 2009; Abella 2010;
Restoration Ecology 7
Reclamation and sagebrush plant community recovery
Bates & Davies 2014). Of the three species of shrubs that were
most abundant, C.viscidiorus had the highest RI, and was fre-
quently more abundant on wellpads than on undisturbed plots.
Its status as an early-successional species (Bates et al. 2009;
Bates & Davies 2014) is supported by our study; the wellpads
with the highest cover of C.viscidiorus were also the most
recently disturbed (and most recently reclaimed), and abun-
dance of C.viscidiorus decreased as the age of the wellpad
increased. The presence of these early-successional species on
reclaimed wellpads may indicate that reclamation has not met
its goal of increasing the rate of succession by “skipping” early
seral stages (Prach et al. 2007). Presence of early-successional
species on reclaimed wellpads further indicates that even with
human intervention, these systems recover slowly. Temporally
variable factors, particularly weather, affect seedling germina-
tion and establishment (Chambers 2000). Our seedbank study
suggests that even under ideal conditions, germination and
establishment is not guaranteed, and is not equally successful
for every functional group. The abundance of grass seedlings in
our seedbank study is consistent with the tendency of grasses to
recover more readily than forbs or shrubs. Conversely, the lack
of success of other functional groups indicates that unfavorable
conditions are likely to limit germination, recovery, and rate of
plant growth, even if propagule availability is manipulated by
adding seeds.
Our results may also have been affected by a variety of
herbivores, including native mule deer and pronghorn, feral
horses, and cattle. While other studies have found that grazing
at low stocking rates after disturbance does not negatively affect
recovery of big sagebrush communities (Bates et al. 2009; Bates
& Davies 2014), the historical stocking rates at our sites are
unknown. Cattle are currently grazed at a fairly low stocking rate
in the area, but feral horses are present in uctuating abundance
due to sustained population growth with periodic round-ups as
mandated by federal law (Public Rangelands Improvement Act
1978). Feral horses have been linked to a variety of negative
effects on ecosystems (Davies et al. 2014), and their apparent
preference for certain wellpads in the area of our study may
have prevented reclamation success or slowed successional
processes.
Our study made the assumption that successional processes
are linear, and that all of our sites were therefore on a trajec-
tory toward the same “end state.” This assumption allowed us
to compare the rate of recovery of unreclaimed wellpads to that
of reclaimed wellpads. If succession in this system does not
occur linearly, recently reclaimed wellpads (31 years) and old
unreclaimed wellpads (32 years) may not be directly compa-
rable. However, increasing the rate of succession of plant com-
munities is not the only goal of reclamation. Loss of soil and
nutrients is a risk after disturbance, especially in dryland ecosys-
tems (Burke et al. 1995; Munson et al. 2012). Therefore, another
major goal of reclamation is to prevent soil loss via wind erosion
and runoff. The establishment of grasses such as A.cristatum
and shrubs such as C.viscidiorus protects and stabilizes the
soil (Ewel & Putz 2004). Furthermore, quick-sprouting shrubs
can serve as nurse plants, establishing microhabitats suitable
to late-successional species, as demonstrated by Salsola kali in
reclamation of other semiarid systems (Allen 1995).
Our results suggest that current reclamation is not entirely
effective with regards to increasing the rate of succession to
establish fully recovered plant communities, and that recovery
of these plant communities may not be heavily dependent on
human intervention. Reclamation is an expensive endeavor— in
2009, the estimated cost to reclaim one abandoned well was
approximately $29,000 (Andersen et al. 2009). Furthermore, oil
and gas disturbance in the western United States is extensive,
with about 3 million hectares affected since 2000 (Allred et al.
2015). It is important, therefore, to ensure that reclamation is
effective and efcient both ecologically and economically. A
thorough understanding of reclamation outcomes, beginning
with its effects on plant communities, can assist reclamation
stakeholders in adopting strategies that maximize ecological
effectiveness while minimizing economic cost. Our work sug-
gests that current reclamation practices in big sagebrush ecosys-
tems in the South Baxter Basin, Wyoming, are not currently
effective at speeding up recovery of the plant community over-
all, but that they do result in increased rates of recovery for
C.viscidiorus and perennial grass. This has implications for
other mid-latitude shrub steppe ecosystems, where future condi-
tions may limit both regeneration and survival of shrubs and the
plant community as a whole (Palmquist et al. 2016a) and further
decrease the likelihood of reclamation success. Furthermore, the
limited response of disturbed ecosystems to human interven-
tion during recovery is not unique to big sagebrush ecosystems
or, in fact, shrubland ecosystems, suggesting that this challenge
is potentially inherent in a portion of most reclamation efforts
worldwide, regardless of ecosystem (Ratzlaff & Anderson 1995;
Fernández-Abascal et al. 2004; Kruse et al. 2004; Dodson &
Peterson 2009). Further research is needed to clarify and, where
possible, improve upon the effectiveness of widely used recla-
mation techniques, most of which represent a large capital input
for small ecological gain.
Acknowledgments
Research support was provided by the Wyoming Excellence
Fund. JBB and KAP were supported by the USGS Ecosystems
Mission Area and the Restoration Assessment and Monitoring
Program for the Southwest. WKL and ICB were supported by
the University of Wyoming and Yale University. The authors
thank Don Schramm for assistance in locating eld sites and
our eld and lab technicians who assisted with the study. Any
use of trade, product, or rm names is for descriptive purposes
only and does not imply endorsement by the U.S. Government.
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Supporting Information
The following information may be found in the online version of this article:
Tabl e S 1 . Forb and grass species on undisturbed plots, unreclaimed wellpads, and
reclaimed wellpads.
Coordinating Editor: Lora Perkins Received: 10 February, 2017; First decision: 30 March, 2017; Revised: 17 April,
2017; Accepted: 17 April, 2017
10 Restoration Ecology
... Since the goal of pipeline restoration in our study was to return the sites to pre-disturbance structure and function, restoration will be used to describe the process in this manuscript. Others have used it to describe returning disturbed ecosystems to a target condition (Prach et al. 2007;Rottler et al. 2018;Gann et al. 2019). Rough fescue (Festuca hallii), a valuable resource for livestock production, is negatively impacted by suppression of natural fires, intensive agriculture, and energy development activities (Desserud et al. 2010;Otfinowski et al. 2017;Woosaree & Otfinowski 2018). ...
... Studies of oil and gas disturbance impacts on grasslands have focused on single to few disturbances in one or two grassland types, or disturbances in grasslands other than plains rough fescue (Avirmed et al. 2015;Rottler et al. 2018;. ...
... Particle size distribution of sand, silt, and clay was determined by the Bouyoucos hydrometer method (Kalra & Maynard 1991). Electrical conductivity and pH were determined by saturation paste method (Rhoades 1982); calcium, magnesium, potassium, and sodium cation concentrations by atomic absorption spectrometry (Ballantyne 1978); total nitrogen concentration by Kjeldahl digestion (Kalra & Maynard 1991); and total organic carbon by dichromate oxidation-redox titration (Tiessen & Moir 1993). Sodium adsorption ratio was calculated from sodium, calcium and magnesium concentrations (Janzen 1993). ...
Article
Plains rough fescue (Festuca hallii) once a dominant grassland in the Northern Great Plains, has been reduced to a fraction of its original extent by agricultural intensification and energy sector disturbances, and has become a threatened community type. Despite thousands of kilometers of pipelines in grasslands, little is documented about long term restoration outcomes. This research assessed recovery of rough fescue grassland 6 to 21 years after pipeline construction with topsoil stripping and natural regeneration relative to undisturbed reference sites in south-central Canada. Soil properties varied between pipelines and undisturbed prairie, although most were within theoretical values to support plant growth and development. Vegetation cover, species richness and Shannon diversity and evenness did not differ significantly between pipelines and undisturbed prairie. Multivariate analysis (multi-response permutation procedure) showed plant community composition and its dominant species differed significantly between pipelines and undisturbed prairie. Bray-Curtis dissimilarity indices showed dominant species and functional species groups on pipelines were more similar to undisturbed prairie than the undesirable species group. Presence of early to late successional species and increasing Festuca hallii with pipeline age indicate restoration was possible with topsoil salvage and replacement, using natural regeneration as a revegetation method, but requires time to develop and restore a typical rough fescue grassland ecosystem.
... Less intense disturbances (small non-native species invasions, degraded grazing land) can be addressed with less active revegetation methods, and may include prescribed fire, watering, and controlled grazing (Iverson and Wali, 1992;Menke, 1992;Otfinowski et al., 2017). Seed mixes containing late successional species can be used during reclamation to encourage bypassing of early successional states (Rottler et al., 2018;Soulodre et al., 2021). From 1963 to 2014 in Alberta Canada, approximately 400,000 oil and gas wells were drilled, each approximately 100 × 100 m in size; and only 100,000 achieved their reclamation target (Alberta Energy Regulator, 2021). ...
... Alternative revegetation practices have been undertaken, including no seeding (natural recovery) (Rottler et al., 2018;Elsinger et al., 2022), seeding non-dominant wheatgrasses or a diverse seed mix (Soulodre et al., 2021), or grazing early in the revegetation stage (Labadessa et al., 2020). Natural recovery was widely used in many parts of the world for old field revegetation in Europe (Ruprecht, 2006;Jírová et al., 2012;Albert et al., 2014) or forest restoration (Crouzeilles et al., 2017;Deák et al., 2020). ...
... Reclamation of oil and gas disturbances differ from these studies due to disturbance intensity, including topsoil stripping and replacement alter soil physical and chemical properties making them less favourable for pre-disturbance native plant community development. However, they can be used as general analogues since natural recovery has been applied in many native grasslands in the Great Plains of North America with outstanding outcomes (Desserud and Naeth, 2013;Avirmed et al., 2015;Rottler et al., 2018;Soulodre et al., 2021;Elsinger et al., 2022). Natural recovery is cost effective, with low human intervention, and mostly relies on the residual soil propagule bank and/ or seed dispersal from adjacent areas (Avirmed et al., 2015;Rottler et al., 2018;Shaughnessy et al., 2022;Soulodre et al., 2021;Elsinger et al., 2022). ...
Article
Over the last 90 years, dry mixed grass prairie across North America has been severely impacted by agriculture, urbanization, and oil and gas operations, presenting significant challenges for land reclamation and range management. This study examined how seed mix and natural recovery revegetation treatments influenced plant community development trends on reclaimed well sites in Alberta, Canada. Three seed mixes, dominant wheatgrass (four species with 95% wheatgrass), non-dominant wheatgrass (five species with 80% non-wheatgrass), and diverse (22 grass and forb species), and natural recovery (unseeded) revegetation treatments were compared to undisturbed mixed grass prairie. Five years after reclamation natural recovery led to a plant community with lesser graminoid and greater forb cover, greater species richness and diversity, and greater bare ground relative to seed mix treatments. Seeded treatments resulted in communities dominated by native wheatgrass species. Multivariate tests revealed community composition of undisturbed prairie and the natural recovery treatment differed from seeded treatments. Indicator species analysis showed the natural recovery treatment was dominated by secondary successional perennial species, while the diverse treatment was dominated by native and non-native early to late successional perennial species. This implies that vegetation recovered more rapidly after disturbance with natural recovery than with a diverse seed mix. Non-native species cover showed a declining trend, and five years after reclamation it was <5% across treatments. Natural recovery revegetation was more effective than seeded treatments; however, a diverse seed mix could be used for mixed grass prairie reclamation.
... The challenge of restoring big sagebrush (Artemisia tridentata) is a prominent example in western North America of the need to understand the complex regeneration processes of a long-lived, woody species in a variable environment (Davies et al. 2011, Brabec et al. 2015). Restoration of big sagebrush is slow, and outcomes, particularly of seeding efforts, are often unpredictable and mixed (Knutson et al. 2014, Rottler et al. 2018, Shriver et al. 2019, Davies et al. 2020. Because of the importance of the big sagebrush region (Davies et al. 2011, Finch et al. 2016, detailed management frameworks have been developed (Finch et al. 2016, Chambers et al. 2017, Crist et al. 2019, and the temporal, spatial, and financial extent of restoration activities in the big sagebrush region are among the largest in North America (Young et al. 1979, Pilliod et al. 2017, Copeland et al. 2018. ...
... Big sagebrush is a prime example of a long-lived dryland plant whose distribution, abundance, and potential future viability may be constrained by regeneration. The contemporary relevance of the big sagebrush regeneration challenge is highlighted by the unpredictable and often mixed outcomes from big sagebrush restoration efforts (Knutson et al. 2014, Rottler et al. 2018, Shriver et al. 2019, Davies et al. 2020. ...
... Overall, it would be helpful if models clearly quantify which conditions they are expected to represent. GISSM currently represents, in explicit form, abiotic processes affecting regeneration in undisturbed big sagebrush vegetation while biotic factors are implicitly represented; however, it may be valuable for model applications that support land management decision making, particularly under nonstationary climate conditions, to integrate and expand GISSM into a general vegetation model that explicitly represent responses to fire, invasive annual grasses, and fire-annual grass interactions as well as relevant general biotic processes affecting big sagebrush regeneration such as competition or facilitation (DiCristina and Germino 2006, Hoelzle et al. 2012, McAdoo et al. 2013, Davidson et al. 2019) such as STEP-WAT2 (Palmquist et al. 2018). Further useful model developments could be to explicitly represent variable seed availability which would allow for restoration seeding events at different seeding rates instead of assuming sufficient seeds in every year as well as to differentiate big sagebrush subspecies. ...
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Regeneration is an essential demographic step that affects plant population persistence, recovery after disturbances, and potential migration to track suitable climate conditions. Challenges of restoring big sagebrush (Artemisia tridentata) after disturbances including fire‐invasive annual grass interactions exemplify the need to understand the complex regeneration processes of this long‐lived, woody species that is widespread across the semiarid western U.S. Projected 21st century climate change is expected to increase drought risks and intensify restoration challenges. A detailed understanding of regeneration will be crucial for developing management frameworks for the big sagebrush region in the 21st century. Here, we used two complementary models to explore spatial and temporal relationships in the potential of big sagebrush regeneration representing (1) range‐wide big sagebrush regeneration responses in natural vegetation (process‐based model) and (2) big sagebrush restoration seeding outcomes following fire in the Great Basin and the Snake River Plains (regression‐based model). The process‐based model suggested substantial geographic variation in long‐term regeneration trajectories with central and northern areas of the big sagebrush region remaining climatically suitable, whereas marginal and southern areas are becoming less suitable. The regression‐based model suggested, however, that restoration seeding may become increasingly more difficult, illustrating the particularly difficult challenge of promoting sagebrush establishment after wildfire in invaded landscapes. These results suggest that sustaining big sagebrush on the landscape throughout the 21st century may climatically be feasible for many areas and that uncertainty about the long‐term sustainability of big sagebrush may be driven more by dynamics of biological invasions and wildfire than by uncertainty in climate change projections. Divergent projections of the two models under 21st century climate conditions encourage further study to evaluate potential benefits of re‐creating conditions of uninvaded, unburned natural big sagebrush vegetation for post‐fire restoration seeding, such as seeding in multiple years and, for at least much of the northern Great Basin and Snake River Plains, the control of the fire‐invasive annual grass cycle.
... Comparison of ecosystem development following reclamation of energy sector disturbances with undisturbed ecosystems is commonly used to evaluate reclamation success as they are more biologically stable and representative of predisturbance conditions (Hobbs and Norton 1996;White and Walker 1997;Dhar et al. 2020). Although studies illustrate impacts of oil and gas disturbance on different grassland types (Hammermeister et al. 2003;Avirmed et al., 2015;Rottler et al. 2018;Naeth et al. 2020) including rough fescue (Desserud et al. 2010;Desserud and Naeth 2013;Woosaree and Otfinowski 2018), researchers have rarely addressed plant community changes following different site construction and revegetation methods using long term data relative to natural analogues in rough fescue. This information is critical to elucidate whether response of the restored ecosystem are due to the reclamation activity or natural recovery (White and Walker 1997;Ruiz-Jaen and Aide 2005). ...
... Plant community composition of minimum disturbance with natural recovery sites was most similar to undisturbed prairie, had more late seral species, and was dominated by late successional species Festuca hallii and Hesperostipa spartea. Rottler et al. (2018) reported that natural recovery had greater establishment of late successional species than active reclamation. Hesperostipa spartea often co-dominates with Festuca hallii and may establish more readily from the seed bank or disperse from neighbouring grasslands. ...
Article
Plains rough fescue (Festuca hallii), once dominant in grasslands of the Northern Great Plains, has been reduced to remnants mainly through agricultural and energy sector development. This study assessed the impacts of oil and gas well site disturbances on plains rough fescue grassland to predict successional trends following disturbance. We examined trends in vegetation cover, richness, diversity, and community composition for two construction techniques (topsoil stripping, minimum disturbance), three revegetation methods (agronomic seed mix, native seed mix, natural recovery), and two reclamation scenarios (reclaimed within < 10 yrs; reclaimed within > 10 yrs) relative to adjacent undisturbed prairie (reference sites) over 28 years in 33 grassland sites. Reclamation success was more closely related to methods of construction and revegetation than years since reclamation. Species richness, diversity, both native and non-native species cover, and species composition were similar between undisturbed prairie and areas subject to minimum disturbance and natural recovery. In contrast, undisturbed prairie differed from areas with topsoil stripping and seeding to either agronomic or native species. Plant community composition on minimum disturbance sites with natural recovery was returning to a predisturbed plains rough fescue community within 10 years after reclamation. Impacts of construction method that involved intensive soil handling and seeding with native or non-native seed mixes were disruptive to recovery of fescue grassland. We therefore recommend retaining grassland sod intact through minimum disturbance and utilizing natural recovery as the best option for successful reclamation of native rough fescue grassland after well site disturbance.
... Most studies found the germinable seed bank did not closely reflect vegetation composition ( Harper 1977 ;Coffin and Laurenroth 1989 ;Rottler et al. 2018 ), although extant vegetation usually impacts broad patterns in the seed bank ( Peart 1989 ). Our study supported this, with natural recovery dominated by early seral species, and nondominant wheatgrass and undisturbed treatments dominated by perennial grasses with fewer early seral species in the seed bank. ...
... This was also supported by our aboveground vegetation where early seral species abundance was low ( < 5%). This might be due to seed bank propagule dormancy or microenvironmental conditions that must be satisfied before seed germination and establishment can occur ( Coffin and Laurenroth 1989 ;Rottler et al. 2018 ;Pilon et al. 2019 ). Grazing may be inhibiting succession in natural recovery by increasing early seral species in the seed bank, also noted by others. ...
Article
Reclamation of surface disturbances on grasslands is an important management issue. This research examined how cattle grazing and revegetation treatments influenced vegetation development on mixed prairie well sites. Three seed mix treatments, dominant wheatgrass (a Triticeae tribe) (four species providing 95% wheatgrass seed in the seed mix), non-dominant wheatgrass (five species with 80% non-wheatgrasses in the seed mix), and diverse (22 grass and forb species), and a natural recovery (unseeded) treatment, with and without cattle grazing, were compared to undisturbed (control) prairie for soil seedbank, vegetation composition, ground cover, and biomass. The non-dominant wheatgrass seed mix resulted in communities dominated by wheatgrass species, whereas natural recovery was dominated by early and mid-seral species. Seeding yielded greater above ground biomass with less than 20% bare ground; natural recovery biomass was slightly less with greater bare ground (grazed 45%, ungrazed 23%). Cattle grazing reduced cover of northern wheatgrass (Elymus lanceolatus Scribn. & J.G.Sm.) Gould) in seeded treatments. Species richness and diversity were greater with natural recovery than with seeding and in undisturbed prairie. Multivariate tests showed that plant community composition in undisturbed prairie and natural recovery differed from seeded treatments; natural recovery was dominated by early to mid-successional species. The short term patterns of change in different vegetation parameters suggest that irrespective of grazing, natural recovery and seeding with a diverse native seed mix could be effective approaches for mixed prairie reclamation.
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On the Ground •Restoration practices employed in semiarid sagebrush steppe of the North American Intermountain West are typically based on objectives to restore habitat to mid- to late-seral plant communities. •Incorporating succession management techniques including representation from early seral community species in restoration plans and seed mixtures could bridge the temporal gap between disturbance and stable climax conditions. •Early seral species evolved to establish quickly and occupy disturbed soils, reduce erosion, and provide a food source for wildlife. Additionally, they alter soil chemistry and biology dynamics that favor transition to later seral phases. Many early seral natives reduce exotic weed growth and seed production. •Despite their benefits, early seral species have poor representation in restoration practices largely due to cultural biases. •Continued investigation of early seral natives in restoration practices will better elucidate the benefits of this underused group. Developers of plant materials should focus on developing a broader suite of early seral germplasm sources for Intermountain restoration activities.
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Abstract Energy development is one of the most rapidly increasing land uses in North America, so understanding how wildlife respond to different types of energy infrastructure is crucial for informing land‐use policies. Effects of energy development on wildlife habitat use and selection can vary depending on infrastructure type, level of industrial activity, and density. I examined seasonal habitat use and selection of greater sage‐grouse in relation to energy development in a high‐elevation oil and gas field in western Colorado by linking spatially and temporally explicit energy infrastructure layers with telemetry locations of marked females from 2006 to 2014. Objectives were to (1) quantify energy infrastructure around seasonal use locations; (2) examine how seasonal resource selection is affected by energy infrastructure with disturbed versus reclaimed surface and different levels of industrial activity; and (3) assess current surface disturbance and infrastructure density caps. Between 92% and 97% of seasonal use locations had 1.1%–2.5% disturbed surface during breeding and winter and selected locations with lower densities of active energy features during breeding and roads in winter. Density caps of one active energy feature and 1.5 mi (2.41 km) of road per section were adequate to prevent avoidance except during the breeding season. Disturbance caps should be set at 1.1% disturbed surface and 1.8% total anthropogenic surface in breeding habitat and 2.5% disturbed surface and 3.5% total anthropogenic surface in winter habitat to minimize negative impacts on female habitat selection in this population. Results also support timing restrictions on construction and drilling during breeding and rapid transitioning of well pads from drilling to production.
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Plains rough fescue (Festuca hallii) once a dominant grassland in the Northern Great Plains, has been reduced to a fraction of its original extent by agricultural intensification and energy sector disturbances, and has become a threatened community type. Despite thousands of kilometers of pipelines in grasslands, little is documented about long term restoration outcomes. This research assessed recovery of rough fescue grassland 6 to 21 years after pipeline construction with topsoil stripping and natural regeneration relative to undisturbed reference sites in south‐central Canada. Soil properties varied between pipelines and undisturbed prairie, although most were within theoretical values to support plant growth and development. Vegetation cover, species richness and Shannon diversity and evenness did not differ significantly between pipelines and undisturbed prairie. Multivariate analysis (multi‐response permutation procedure) showed plant community composition and its dominant species differed significantly between pipelines and undisturbed prairie. Bray–Curtis dissimilarity indices showed dominant species and functional species groups on pipelines were more similar to undisturbed prairie than the undesirable species group. Presence of early to late successional species and increasing Festuca hallii with pipeline age indicate restoration was possible with topsoil salvage and replacement, using natural regeneration as a revegetation method, but requires time to develop and restore a typical rough fescue grassland ecosystem. This article is protected by copyright. All rights reserved.
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Identifying, protecting, and restoring habitats for declining wildlife populations is foundational to conservation and recovery planning for any species at risk of decline. Resource selection analysis is a key tool to assess habitat and prescribe management actions. Yet, it can be challenging to map suitable resource conditions across a wide range of ecological contexts and use the resulting models to identify effective and universal habitat improvement actions. We developed a management-centric modeling approach that sought to balance the need to evaluate the consistency of key habitat conditions and improvement actions across multiple, distinct populations, while allowing context-specific environmental variables and spatial scales to nuance selection responses that form the basis of location-specific management prescriptions. To demonstrate this approach, we developed a set of habitat selection models for Gunnison sage-grouse (Centrocercus minimus), a threatened species under the U.S. Endangered Species Act. Conservation, species recovery, and habitat management efforts are needed in six isolated satellite populations (San Miguel, Crawford, Piñon Mesa, Dove Creek, Cerro Summit-Cimarron-Sims, and Poncha Pass) where environmental conditions differ, and the already small number of birds are declining. We used multi-scale and seasonal resource selection analyses to quantify relationships between environmental conditions and sites used by animals. All models included key habitat variables often altered through management actions to assess their differential influences across models. We found important similarities and differences among satellites, indicating that, although some rules of thumb are generally well-grounded, the consideration of population-specific environmental differences could increase the efficiency of local habitat improvement actions. Sage-grouse also had diverse responses to resource conditions at different scales, indicating that regional spatial (e.g., landscape) and local patch scale can differentially influence expected habitat improvements associated with where such management actions are implemented. Although context variables such as topography cannot be manipulated, sage-grouse associations revealed information that could guide the siting of improvement actions. This approach to balancing management objectives associated with habitat assessment may benefit spatially-structured populations with different environmental contexts and species with complex habitat needs and associations.
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On the Ground • There are three general stages of a well's life on US public land: 1) the permitting process to drill, 2) active extraction of fossil fuel resource, and 3) plugging and abandonment of well. • There is no national standard for oil and gas reclamation in the United States similar to mining and therefore current reclamation practices and standards fail to achieve long-term effectiveness across the western United States. • A reclaimed well pad's land potential is determined by 3 properties: static (e.g., climate), dynamic (e.g., soil stability), and process (e.g., water retention). • Understanding a reclaimed well pad's land potential enables federal land agencies to outline surface reclamation goals and requirements consistently and clearly. • Monitoring for land potential increases the capacity of the private industry to practice adaptive management by enabling companies to respond to plant community changes while maintaining long-term progress toward recovery.
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Drylands cover 40% of the global terrestrial surface and provide important ecosystem services. While drylands as a whole are expected to increase in extent and aridity in coming decades, temperature and precipitation forecasts vary by latitude and geographic region suggesting different trajectories for tropical, subtropical, and temperate drylands. Uncertainty in the future of tropical and subtropical drylands is well constrained, whereas soil moisture and ecological droughts, which drive vegetation productivity and composition, remain poorly understood in temperate drylands. Here we show that, over the twenty first century, temperate drylands may contract by a third, primarily converting to subtropical drylands, and that deep soil layers could be increasingly dry during the growing season. These changes imply major shifts in vegetation and ecosystem service delivery. Our results illustrate the importance of appropriate drought measures and, as a global study that focuses on temperate drylands, highlight a distinct fate for these highly populated areas.
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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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The potential influence of seed bank composition on range shifts of species due to climate change is unclear. Seed banks can provide a means of both species persistence in an area and local range expansion in the case of increasing habitat suitability, as may occur under future climate change. However, a mismatch between the seed bank and the established plant community may represent an obstacle to persistence and expansion. In big sagebrush (Artemisia tridentata) plant communities in Montana, USA, we compared the seed bank to the established plant community. There was less than a 20% similarity in the relative abundance of species between the established plant community and the seed bank. This difference was primarily driven by an overrepresentation of native annual forbs and an underrepresentation of big sagebrush in the seed bank compared to the established plant community. Even though we expect an increase in habitat suitability for big sagebrush under future climate conditions at our sites, the current mismatch between the plant community and the seed bank could impede big sagebrush range expansion into increasingly suitable habitat in the future.
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In the coming century, climate change is projected to impact precipitation and temperature regimes worldwide, with especially large effects in drylands. We use big sagebrush ecosystems as a model dryland ecosystem to explore the impacts of altered climate on ecohydrology and the implications of those changes for big sagebrush plant communities using output from 10 Global Circulation Models (GCMs) for two representative concentration pathways (RCPs). We ask: (1) What is the magnitude of variability in future temperature and precipitation regimes among GCMs and RCPs for big sagebrush ecosystems, and (2) How will altered climate and uncertainty in climate forecasts influence key aspects of big sagebrush water balance? We explored these questions across 1980-2010, 2030-2060, and 2070-2100 to determine how changes in water balance might develop through the 21st century. We assessed ecohydrological variables at 898 sagebrush sites across the western US using a process-based soil water model, SOILWAT, to model all components of daily water balance using site-specific vegetation parameters and site-specific soil properties for multiple soil layers. Our modeling approach allowed for changes in vegetation based on climate. Temperature increased across all GCMs and RCPs, whereas changes in precipitation were more variable across GCMs. Winter and spring precipitation was predicted to increase in the future (7% by 2030-2060, 12% by 2070-2100), resulting in slight increases in soil water potential (SWP) in winter. Despite wetter winter soil conditions, SWP decreased in late spring and summer due to increased evapotranspiration (6% by 2030-2060, 10% by 2070-2100) and groundwater recharge (26% and 30% increase by 2030-2060 and 2070-2100). Thus, despite increased precipitation in the cold season, soils may dry out earlier in the year, resulting in potentially longer, drier summer conditions. If winter precipitation cannot offset drier summer conditions in the future, we expect big sagebrush regeneration and survival will be negatively impacted, potentially resulting in shifts in the relative abundance of big sagebrush plant functional groups. Our results also highlight the importance of assessing multiple GCMs to understand the range of climate change outcomes on ecohydrology, which was contingent on the GCM chosen.
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Increasing demands on and and semiarid ecosystems, which comprise one-third of Earth's terrestrial environment, create an urgent need to understand their biodiversity, function, and mechanisms of change. Sagebrush (Artemisia) steppe, the largest semiarid vegetation type in North America, is endangered because of losses to agriculture, excessive grazing, and invasive species. Establishment in 1950 of what is now designated as the Idaho National Engineering and Environmental Laboratory (southeastern Idaho, USA) created the largest existing reserve of this extensive vegetation type. We used cover, density, and frequency data for vascular plants sampled on 79 permanent plots nine times during 45 years to (1) assess long-term changes in abundance and distribution of major species and life forms, (2) assess changes in species richness and plot similarity, and (3) test the hypotheses that plant cover and stability of cover are positively associated with species richness and that invasibility is inversely related to native plant cover and richness. From 1933 through 1957 the area was subject to severe drought, with annual precipitation exceeding the long-term mean only four times. Cover of shrubs plus perennial grasses was 18% in 1950, and the vegetation was heavily dominated by sagebrush. Perennial grass cover was only 0.5%. With elevated precipitation after 1957, shrub cover increased to 25% by 1965, and by 1975 cover of perennial grasses had increased 13-fold. Subsequent fluctuations in cover did not track precipitation closely. Cover and density of major species were often out of phase, and correlation analyses indicated lags of 2-5 yr in responses of species or functional groups to precipitation. Aggregate species richness of the area has not changed appreciably, but richness of shrubs, perennial grasses, and forbs per plot steadily increased from 1950 to 1995. Vegetative heterogeneity also increased, with mean similarity among plots declining from 72% to 40%. Plots having higher species richness tended to maintain higher levels of cover and to vary less in cover relative to their mean level, indicating links between species richness and function. Abundance of normative species was negatively correlated with cover, but not with richness of native species. Thus, adequate cover of native species can render these semiarid communities more resistant to invasion. Maintaining richness and cover of native species should be a high management priority for these ecosystems.