Research and Publications
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California’s high density, fire-excluded forests experienced an extreme drought accompanied by warmer than normal temperatures from 2012 to 2015, resulting in the deaths of millions of trees. We examined tree mortality
and growth of mixed-conifer stands that had been experimentally treated between 2011 and 2013 with two different thinning treatments, one with more structural variability (HighV) and one with less structural variability (LowV), applied alone or in combination with prescribed burning. Tree mortality between 2014 and 2018 varied by species ranging from 42% of white fir (Abies concolor) to 18% of sugar pine (Pinus lambertiana), 12% of
incense cedar (Calocedrus decurrens) and 10% of yellow pine (P. ponderosa and P. jeffreyi). Lower overall tree mortality rates at this location relative to drier locations in the southern Sierra Nevada suggested that drought
effects may have been ameliorated by lower water deficits due to our site’s more northerly location and deep, productive soils in combination with reductions in tree competition following thinning and burning. Averaged
across burn treatments, thinning reduced the overall mortality rate between 2014 and 2018 from 34% to 11%. A total of 23% of the basal area was lost in the unthinned control treatments during this time period, while basal
area was unchanged in the thinned treatments, with growth offsetting mortality. There was no significant difference in mortality or basal area change between LowV and HighV, suggesting that leaving trees at variable spacing may not compromise growth or resilience of the stand during a drought. Overall tree mortality was greater in the prescribed burn treatments, most pronounced in the smaller tree size classes, and varied by species, with burning having a significant effect on incense cedar and all pines, but not white fir. Trees with greater competition (Hegyi index) were more likely to die, particularly when also burned. Burning, however, consumed surface fuels and lowered fire hazard. With predictions of warmer droughts and greater weather variability, reducing forest density (basal area) and keeping surface fuel loads low will be important for building greater resilience to future drought stress and wildfire.
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The need for basic information on spatial distribution and abundance of plant species for research and management in semiarid ecosystems is frequently unmet. This need is particularly acute in the large areas impacted by megafires in sagebrush steppe ecosystems, which require frequently updated information about increases in exotic annual invaders or recovery of desirable perennials. Remote sensing provides one avenue for obtaining this information. We considered how a vegetation model based on Landsat satellite imagery (30 m pixel resolution; annual images from 1985 to 2018) known as the National Land Cover Database (NLCD) “Back-in-Time” fractional component time-series, compared with field-based vegetation measurements. The comparisons focused on detection thresholds of post-fire emergence of fire-intolerant Artemisia L. species, primarily A. tridentata Nutt. (big sagebrush). Sagebrushes are scarce after fire and their paucity over vast burn areas creates challenges for detection by remote sensing. Measurements were made extensively across the Great Basin, USA, on eight burn scars encompassing ~500 000 ha with 80 plots sampled, and intensively on a single 113 000 ha burned area where we sampled 1454 plots.
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Today, American conservation confronts the climate crisis, the biodiversity crisis, a global pandemic, skeptics of these threats, a massive federal deficit, economic hardship, social injustice, and political divisions that threaten our democracy. Yet, at the same time, people continue to explore new ways to work together to use science, collaboration, and innovation to advance efforts to protect our environment, conserve our natural resource legacy, and broaden its benefits for all Americans.
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The researchers report on creating an unburned area data set for the Inland Northwest from 1984 – 2014 and subsequent analyses using this dataset. Here are some of the key findings for this JFSP project:
- Unburned area occurrence is consistent or stabilized to-date, with no evidence of increasing or decreasing trends under current climate conditions
- Unburned areas are utilized by sage grouse and help maintain viable populations when these fire refugia are present
- Persistent unburned islands are ecologically important areas and are related to specific topography and fuel type characteristics
- Persistent unburned area attributes differ between forests and rangelands
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In 2009, at the behest of Congress, the Council on Environmental Quality (CEQ) and the US Department of the Interior (DOI) were asked to develop a national, government-wide climate adaptation strategy for fish, wildlife, plants, and ecosystems. In doing so, the Federal Government recognized the immensity of climate change impacts on the Nation’s vital natural resources, as well as the critical need for partnership among federal, state, and tribal fish and wildlife agencies. More than 90 diverse technical, scientific, and management experts from across the country participated in the development and, in 2012, the National Fish, Wildlife, and Plants Climate Adaptation Strategy (Strategy) was published. Designed to “inspire and enable natural resource managers, legislators, and other decision makers to take effective steps towards climate change adaptation over the next five to ten years,” the time has come for the natural resource community to consider the impact of the Strategy, while identifying the necessary evolution of it, to continue to effectively safeguard the Nation’s natural resources in a changing climate.
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Extreme wildfires are increasing in frequency globally, prompting new efforts to mitigate risk. The ecological appropriateness of risk mitigation strategies, however, depends on what factors are driving these increases. While regional syntheses attribute increases in fire activity to both climate change and fuel accumulation through fire exclusion, they have not disaggregated causal drivers at scales where land management is implemented. Recent advances in fire regime modeling can help us understand which drivers dominate at management-relevant scales. We conducted fire regime simulations using historical climate and fire exclusion scenarios across two watersheds in the Inland Northwestern U.S., which occur at different positions along an aridity continuum. In one watershed, climate change was the key driver increasing burn probability and the frequency of large fires; in the other, fire exclusion dominated in some locations. We also demonstrate that some areas become more fuel-limited as fire-season aridity increases due to climate change. Thus, even within watersheds, fuel management must be spatially and temporally explicit to optimize effectiveness. To guide management, we show that spatial estimates of soil aridity (or temporally averaged soil moisture) can provide a relatively simple, first-order indicator of where in a watershed fire regime is climate vs. fuel-limited and where fire regimes are most vulnerable to change.
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The Sagebrush Treatment Evaluation Project (SageSTEP) evaluated the ecological effects of prescribed fire and cut‐and‐leave treatments in sagebrush communities experiencing tree expansion in North American cold desert shrublands. We used 10 yr of data from the SageSTEP network to test how treatments interacted with pre‐treatment tree dominance, soil climate, and time since treatment to affect plant functional groups and dominant species. Non‐sprouting shrub (Artemisia spp.), sprouting shrub, perennial graminoid, and annual grass responses depended on tree dominance and soil climate, and responses were related to the dominant species’ life‐history traits. Sites with warm and dry soils showed increased perennial graminoid but reduced Artemisia shrub cover across the tree dominance gradient after prescribed burning, while sites with cool and moist soils showed favorable post‐burn responses for both functional types, particularly at low to moderate tree dominance. Cut‐and‐leave treatments sustained or increased native perennial plant functional groups and experienced smaller increases in exotic annual plants in both soil climates across the tree dominance gradient. Both treatments reduced biocrust cover. Selecting appropriate tree‐reduction treatments to achieve desired long‐term outcomes requires consideration of dominant species, site environmental conditions, and the degree of woodland expansion. Careful selection of management treatments will reduce the likelihood of undesirable consequences to the ecosystem.
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We used a common garden study to quantify variation in growth and drought resistance traits in 99 populations of Elymus elymoides from a broad geographic and climatic range in the western United States. Ecotypes from drier sites produced less biomass and smaller seeds, and had traits associated with greater drought resistance: small leaves with low osmotic potential and high integrated water use efficiency (δ13C). Seasonality also influenced plant traits. Plants from regions with relatively warm, wet summers had large seeds, large leaves, and low δ13C. Irrespective of climate, we also observed trade‐offs between biomass production and drought resistance traits. Together, these results suggest that much of the phenotypic variation among E. elymoides ecotypes represents local adaptation to differences in the amount and timing of water availability. In addition, ecotypes that grow rapidly may be less able to persist under dry conditions. Land managers may be able to use this variation to improve restoration success by seeding ecotypes with multiple drought resistance traits in areas with lower precipitation. The future success of this common rangeland species will likely depend on the use of tools such as seed transfer zones to match local variation in growth and drought resistance to predicted climatic conditions.
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Timing is everything, especially when it comes to the complex ecological interactions between plants and the environment. For range managers concerned with maintaining the integrity and productivity of rangelands, it is critical to monitor the seasonal development and condition of grasses and other vegetation on which cattle graze. PhenoMap is a new Web-based tool that managers can use to assess the production and location of high quality forage. It uses satellite imagery to address the need for near-real-time information about plant life cycle events over large spatial areas.
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Urban populations rely on a suite of ecosystem services generally provided by the ecological function of natural areas. But the expansion of urban environments and growing suburban or exurban neighborhoods often necessitates destruction of those natural areas for development supporting a growing urban populace. Ecological impacts from development reduce regional biodiversity and negatively affect the ability of remaining natural areas to provide goods and services critical to people. Secondary impacts to biodiversity also occur at broad geographic scales through commodity production supporting urban centers. For example, agricultural production often involves creating agroeconomic systems based largely on farming a limited number of species, and commonly relegates biological diversity to small patches of land deemed unsuitable for crops. Such practices exacerbate the negative biological effects inherent in urban development and drastically increase the need for urban populations to address biological diversity within municipalities. Residents are becoming progressively knowledgeable about environmental issues and are expressing values and concerns to local and regional managing agencies. Governments are responding to public pressure through recommendations intended to reduce resource use, improve wildlife habitat, and provide a local aesthetic. Although the appropriateness of native plants in urban settings is often questioned, the use of regionally specific native vegetation is identified as one method to meet those recommendations. Native plants as primary landscape elements have the added benefit of increasing biodiversity and creating environments capable of providing ecosystem goods and services within urban environments.