Climate-Driven Shifts in Soil Temperature and Moisture Regimes Suggest Opportunities to Enhance Assessments of Dryland Resilience and Resistance

Bradford, John B.; Shlaepfer, Daniel R.; Lauenroth, William K.; Palmquist, Kyle A.; Chambers, Jeanne C.; Maestas, Jeremy D.; Campbell, Steven

doi:10.3389/fevo.2019.00358

Cited by 48 publications

(56 citation statements)

References 71 publications

(85 reference statements)

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“…Interactions among drought, disturbances and biological invasions have caused pervasive land degradation in dryland regions (Millennium Ecosystem Assessment, 2005). Estimated geographic patterns in ecological resistance and resilience are increasingly being used to guide the application of land treatments designed to prevent further impacts and rehabilitate degraded areas (Chambers et al, 2017), although current tools are often not built upon drought metrics with demonstrated importance for dryland ecosystems (Bradford et al, 2019). Quantitative estimates of ecological drought severity, like those presented here, are derived from process‐based analytical tools that can be leveraged to provide ecologically relevant foundational information about current and future drought patterns to improve these vulnerability assessments.…”

Section: Discussionmentioning

confidence: 99%

Robust ecological drought projections for drylands in the 21st century

Bradford

Schlaepfer

Lauenroth

et al. 2020

Global Change Biology

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145

101

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Dryland ecosystems may be especially vulnerable to expected 21st century increases in temperature and aridity because they are tightly controlled by moisture availability. However, climate impact assessments in drylands are difficult because ecological dynamics are dictated by drought conditions that are difficult to define and complex to estimate from climate conditions alone. In addition, precipitation projections vary substantially among climate models, enhancing variation in overall trajectories for aridity. Here, we constrain this uncertainty by utilizing an ecosystem water balance model to quantify drought conditions with recognized ecological importance, and by identifying changes in ecological drought conditions that are robust among climate models, defined here as when >90% of models agree in the direction of change. Despite limited evidence for robust changes in precipitation, changes in ecological drought are robust over large portions of drylands in the United States and Canada. Our results suggest strong regional differences in long‐term drought trajectories, epitomized by chronic drought increases in southern areas, notably the Upper Gila Mountains and South‐Central Semi‐arid Prairies, and decreases in the north, particularly portions of the Temperate and West‐Central Semi‐arid Prairies. However, we also found that exposure to hot‐dry stress is increasing faster than mean annual temperature over most of these drylands, and those increases are greatest in northern areas. Robust shifts in seasonal drought are most apparent during the cool season; when soil water availability is projected to increase in northern regions and decrease in southern regions. The implications of these robust drought trajectories for ecosystems will vary geographically, and these results provide useful insights about the impact of climate change on these dryland ecosystems. More broadly, this approach of identifying robust changes in ecological drought may be useful for other assessments of climate impacts in drylands and provide a more rigorous foundation for making long‐term strategic resource management decisions.

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Section: Discussionmentioning

confidence: 99%

Robust ecological drought projections for drylands in the 21st century

Bradford

Schlaepfer

Lauenroth

et al. 2020

Global Change Biology

Self Cite

145

101

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“…These predictions were inferred to indicate apparent resilience and resistance and used to prioritize implementation of park burned-area emergency response and weed management plans (Hoh et al, 2015). More recently, the soil and ecological site attributes provided by the US Natural Resource Conservation Service (NRCS) web soil survey have been used to map current and future potential resilience and resistance across the sagebrush steppe biome (Maestas et al, 2016;Bradford et al, 2019), including in protected areas. For example, each of the separate management units of JODA are mapped almost entirely as low resilience currently and in the future (Figure 1A), a predicament also faced by other parks in the region.…”

Section: Introductionmentioning

confidence: 99%

“…To support this need, we evaluate a 7-year (2011-2017) study of native and non-native grass species' responses to a 2011 wildfire in a repeatedly burned and inherently low resilience protected-area landscape in the John Day Fossil Beds National Monument. We use a newly developed class of zero-augmented FIGURE 1 | (A) The five units of the John Day Fossil Beds National Monument, including Clarno (upper left) mapped to the current ecological resilience predictions developed by Bradford et al (2019). Note that future resilience in this region (upper left A) was predicted to remain low under climate change scenarios examined by Bradford et al (2019).…”

Section: Introductionmentioning

confidence: 99%

“…We use a newly developed class of zero-augmented FIGURE 1 | (A) The five units of the John Day Fossil Beds National Monument, including Clarno (upper left) mapped to the current ecological resilience predictions developed by Bradford et al (2019). Note that future resilience in this region (upper left A) was predicted to remain low under climate change scenarios examined by Bradford et al (2019). (B) The five ecological sites in Clarno (John Day Fossil Beds National Monument) mapped by Natural Resources Conservation Service Web Soil Survey for the National Park Service (NPS, 2012) overlain with vegetation monitoring quadrat locations surveyed during 2011-2017 following a National Park Service protocol (Yeo et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

“…We structured our model hierarchically so that observations could be grouped within ecological sites, an important step in contextualizing model-estimated trends over space and time within the resilience and resistance framework. We used the same ecological site descriptions developed through the NRCS web soil survey (NPS, 2012) as was used by Bradford et al (2019) to develop their regional resilience and resistance map, although we retained the NRCS soil survey map unit polygons (see Figure 1B) rather than the coarse grid employed by Bradford et al (2019). Importantly, we were able to utilize attributes of the ecological sites, including associated state-andtransition diagrams (sensu Stringham et al, 2003;Chambers et al, 2014c) and reference plant species lists as articulated hypotheses about fire-driven state transitions (Figure 2).…”

Section: Introductionmentioning

confidence: 99%

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Post-Fire Vegetation Response in a Repeatedly Burned Low-Elevation Sagebrush Steppe Protected Area Provides Insights About Resilience and Invasion Resistance

2020

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Sagebrush steppe ecosystems are threatened by human land-use legacies, biological invasions, and altered fire and climate dynamics. Steppe protected areas are therefore of heightened conservation importance but are few and vulnerable to the same impacts broadly affecting sagebrush steppe. To address this problem, sagebrush steppe conservation science is increasingly emphasizing a focus on resilience to fire and resistance to non-native annual grass invasion as a decision framework. It is well-established that the positive feedback loop between fire and annual grass invasion is the driving process of most contemporary steppe degradation. We use a newly developed ordinal zero-augmented beta regression model fit to large-sample vegetation monitoring data from John Day Fossil Beds National Monument, USA, spanning 7 years to evaluate fire responses of two native perennial foundation bunchgrasses and two non-native invasive annual grasses in a repeatedly burned, historically grazed, and inherently low-resilient protected area. We structured our model hierarchically to support inferences about variation among ecological site types and over time after also accounting for growing-season water deficit, fine-scale topographic variation, and burn severity. We use a state-and-transition conceptual diagram and abundances of plants listed in ecological site reference conditions to formalize our hypothesis of fire-accelerated transition to ecologically novel annual grassland. Notably, big sagebrush (Artemisia tridentata) and other woody species were entirely removed by fire. The two perennial grasses, bluebunch wheatgrass (Pseudoroegneria spicata) and Thurber's needlegrass (Achnatherum thurberianum) exhibited fire resiliency, with no apparent trend after fire. The two annual grasses, cheatgrass (Bromus tectorum) and medusahead (Taeniatherum caput-medusae), increased in response to burn severity, most notably medusahead. Surprisingly, we found no variation in grass cover among ecological sites, suggesting fire-driven homogenization as shrubs were removed and annual grasses became dominant. We found contrasting responses among all four grass species along gradients of topography and water deficit, informative to protected-area conservation strategies. The fine-grained influence of topography was particularly important to variation in cover among species and provides a foothold for conservation in low-resilient, aridic steppe. Broadly, our study demonstrates how to operationalize resilience and resistance concepts for protected areas by integrating empirical data with conceptual and statistical models.

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Modeling cheatgrass distribution, abundance, and response to climate change as a function of soil microclimate

Terry,

Hardegree,

Adler

2024

Ecological Applications

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Exotic annual grass invasions in water‐limited systems cause degradation of native plant and animal communities and increased fire risk. The life history of invasive annual grasses allows for high sensitivity to interannual variability in weather. Current distribution and abundance models derived from remote sensing, however, provide only a coarse understanding of how species respond to weather, making it difficult to anticipate how climate change will affect vulnerability to invasion. Here, we derived germination covariates (rate sums) from mechanistic germination and soil microclimate models to quantify the favorability of soil microclimate for cheatgrass (Bromus tectorum L.) establishment and growth across 30 years at 2662 sites across the sagebrush steppe system in the western United States. Our approach, using four bioclimatic covariates alone, predicted cheatgrass distribution with accuracy comparable to previous models fit using many years of remotely‐sensed imagery. Accuracy metrics from our out‐of‐sample testing dataset indicate that our model predicted distribution well (72% overall accuracy) but explained patterns of abundance poorly (R2 = 0.22). Climatic suitability for cheatgrass presence depended on both spatial (mean) and temporal (annual anomaly) variation of fall and spring rate sums. Sites that on average have warm and wet fall soils and warm and wet spring soils (high rate sums during these periods) were predicted to have a high abundance of cheatgrass. Interannual variation in fall soil conditions had a greater impact on cheatgrass presence and abundance than spring conditions. Our model predicts that climate change has already affected cheatgrass distribution with suitable microclimatic conditions expanding 10%–17% from 1989 to 2019 across all aspects at low‐ to mid‐elevation sites, while high‐ elevation sites (>2100 m) remain unfavorable for cheatgrass due to cold spring and fall soils.

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Climate-Driven Shifts in Soil Temperature and Moisture Regimes Suggest Opportunities to Enhance Assessments of Dryland Resilience and Resistance

Cited by 48 publications

References 71 publications

Robust ecological drought projections for drylands in the 21st century

Robust ecological drought projections for drylands in the 21st century

Post-Fire Vegetation Response in a Repeatedly Burned Low-Elevation Sagebrush Steppe Protected Area Provides Insights About Resilience and Invasion Resistance

Modeling cheatgrass distribution, abundance, and response to climate change as a function of soil microclimate

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