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Wildfire refugia are forest patches that are minimally-impacted by fire and provide critical habitats for fire-sensitive species and seed sources for post-fire forest regeneration. Wildfire refugia are relatively understudied, particularly concerning the impacts of subsequent fires on existing refugia. We opportunistically re-visited 122 sites classified in 1994 for a prior fire refugia study, which were burned by two wildfires in 2012 in the Cascade mountains of central Washington, USA. We evaluated the fire effects for historically persistent fire refugia and compared them to the surrounding non-refugial forest matrix. Of 122 total refugial (43 plots) and non-refugial (79 plots) sites sampled following the 2012...
Public Summary: The area burned by wildfires is expected to increase in many watersheds of the world over the next century as a function of climate change. Increased sedimentation due to soil erosion in burned watersheds can negatively impact downstream aquatic ecosystems and the quality and supply of water. At least 65% of the water supply in the western USA originates in watersheds covered by trees, shrubs, and/or grasses that are prone to wildfire16. Understanding how changing fire frequency, extent, and location will affect watersheds, reservoirs, and the ecosystem services they supply to communities is therefore of great societal importance. A primary threat to socio-ecological systems in this region from...
Abstract (from http://www.publish.csiro.au/WF/WF16165): Interannual variability in burn severity is assessed across forested ecoregions of the western United States to understand how it is influenced by variations in area burned and climate during 1984–2014. Strong correlations (|r| > 0.6) between annual area burned and climate metrics were found across many of the studied regions. The burn severity of individual fires and fire seasons was weakly, but significantly (P < 0.05), correlated with burned area across many regions. Interannual variability in fuel dryness evaluated with fuel aridity metrics demonstrated weak-to-moderate (|r| >0.4) relationships with regional burn severity, congruent with but weaker than...
Streams are classified as perennial (flowing uninterrupted, year-round) or intermittent (flowing part of the year) or ephemeral (flowing only during rainfall events). The classifications of “streamflow permanence” were primarily established in the middle 20th century and are often outdated and inaccurate today if they were not adjusted for changes in land use, wildfires, or climate. Understanding where streams are perennial is important for a variety of reasons. For example, perennial streams receive special regulatory protections under a variety of statutes, and provide important habitat for fish, wildlife, and other species. To predict the likelihood that streams are perennial, we compiled nearly 25,000 observations...
Abstract (from http://www.hydrol-earth-syst-sci.net/21/1/2017/): The phase of precipitation when it reaches the ground is a first-order driver of hydrologic processes in a watershed. The presence of snow, rain, or mixed-phase precipitation affects the initial and boundary conditions that drive hydrological models. Despite their foundational importance to terrestrial hydrology, typical phase partitioning methods (PPMs) specify the phase based on near-surface air temperature only. Our review conveys the diversity of tools available for PPMs in hydrological modeling and the advancements needed to improve predictions in complex terrain with large spatiotemporal variations in precipitation phase. Initially, we review...
Abstract (from ScienceDirect): The interannual variability of tidal marsh plant phenology is largely unknown and may have important ecological consequences. Marsh plants are critical to the biogeomorphic feedback processes that build estuarine soils, maintain marsh elevation relative to sea level, and sequester carbon. We calculated Tasseled Cap Greenness, a metric of plant biomass, using remotely sensed data available in the Landsat archive to assess how recent climate variation has affected biomass production and plant phenology across three maritime tidal marshes in the Pacific Northwest of the United States. First, we used clipped vegetation plots at one of our sites to confirm that tasseled cap greenness provided...
Abstract (from http://www.bioone.org/doi/abs/10.3955/046.089.0305): It is hypothesized that climate impacts forest mosaics through dynamic ecological processes such as wildfires. However, climate-fire research has primarily focused on understanding drivers of fire frequency and area burned, largely due to scale mismatches and limited data availability. Recent datasets, however, allow for the investigation of climate influences on ecological patch metrics across broad regions independent of area burned and at finer scale. One area of particular interest is the distribution of fire refugia within wildfire perimeters. Although much recent research emphasis has been placed on high-severity patches within wildfires,...
Abstract (from http://www.sciencedirect.com/science/article/pii/S0378112716308532): Across the western United States, the three primary drivers of tree mortality and carbon balance are bark beetles, timber harvest, and wildfire. While these agents of forest change frequently overlap, uncertainty remains regarding their interactions and influence on specific subsequent fire effects such as change in canopy cover. Acquisition of pre- and post-fire Light Detection and Ranging (LiDAR) data on the 2012 Pole Creek Fire in central Oregon provided an opportunity to isolate and quantify fire effects coincident with specific agents of change. This study characterizes the influence of pre-fire mountain pine beetle (MPB; Dendroctonus...
Abstract (from http://iopscience.iop.org/article/10.1088/1748-9326/aa6f94/meta): High temperatures and severe drought contributed to extensive tree mortality from fires and bark beetles during the 2000s in parts of the western continental United States. Several states in this region have greenhouse gas (GHG) emission targets and would benefit from information on the amount of carbon stored in tree biomass killed by disturbance. We quantified mean annual tree mortality from fires, bark beetles, and timber harvest from 2003–2012 for each state in this region. We estimated tree mortality from fires and beetles using tree aboveground carbon (AGC) stock and disturbance data sets derived largely from remote sensing. We...
Abstract (from http://onlinelibrary.wiley.com/doi/10.1002/9781119011705.ch10/summary): This chapter discusses an approach that uses MC1 results to create climate-informed state-and-transition simulation model (cSTSMs) in two contrasting landscapes: dry forests in central Oregon and wet forests in western Washington. The studies presented here examine trends in different socioecological values under different climate and management assumptions using a dynamic global vegetation model/STSM approach. The authors found that simulated management actions did not prevent climate-induced vegetation change. Simulated management did in some cases promote desired forest structures and increase resilience to climate change....
Abstract (from http://www.sciencedirect.com/science/article/pii/S0034425716303261): Wildfires shape the distribution and structure of vegetation across the inland northwestern United States. However, fire activity is expected to increase given the current rate of climate change, with uncertain outcomes. A fire impact that has not been widely addressed is the development of unburned islands; areas within the fire perimeter that do not burn. These areas function as critical ecological refugia for biota during or following wildfires, but they have been largely ignored in methodological studies of remote sensing assessing fire severity under the assumption that they will be detected by algorithms for delineating fire...
Abstract (from http://www.sciencedirect.com/science/article/pii/S0034425716305016): Measuring post-fire effects at landscape scales is critical to an ecological understanding of wildfire effects. Predominantly this is accomplished with either multi-spectral remote sensing data or through ground-based field sampling plots. While these methods are important, field data is usually limited to opportunistic post-fire observations, and spectral data often lacks validation with specific variables of change. Additional uncertainty remains regarding how best to account for environmental variables influencing fire effects (e.g., weather) for which observational data cannot easily be acquired, and whether pre-fire agents of...
Aspen forests are “biological hotspots” in the western United States that support numerous wildlife species. Aspen ecosystems are also economically and socially important, providing high quality forage for livestock and game species (e.g. elk), as well as drawing tourists and improving local economies. Aspen ecosystems are in decline across portions of the western U.S., which is thought to be partly due to drought, and recent research suggests that future climate projected for the western U.S. will be even less capable of supporting aspen. We used different research methods to investigate key controls on aspen growth and survivability in the northern Great Basin and central Rockies. Specifically, we projected the...
Unburned islands are areas within wildfire perimeters that did not burn. These islands are important because they serve as a refuge both during and after the fire for plants and animals to survive and subsequently repopulate adjacent burned areas. This project sought to better understand how and why these islands occur – what makes some areas of the landscape fireproof, even as everything around them burns? How can we use that information to manage forests and rangelands in a way that supports continued development of unburned islands and fire refugia, even under climate change? To answer these questions, we developed a historical atlas of unburned islands across the Northwest (Washington, Oregon, and Idaho) and...
Abstract (from http://www.sciencedirect.com/science/article/pii/S0168192315002142): Physically-based models are a powerful tool to help understand interactions of vegetation, atmospheric dynamics, and hydrology, and to test hypotheses regarding the effects of land cover, management, hydrometeorology, and climate variability on ecosystem processes. The purpose of this paper is to evaluate recent modifications and further refinements to a multi-layer plant canopy model for simulating temperature and water vapor within three diverse forest canopies: a 4.5-m tall aspen thicket, a 15-m tall aspen canopy, and a 60-m tall Douglas fir canopy. Performance of the model was strongly related to source strength and profile stability...
Abstract (from http://www.publish.csiro.au/paper/WF15082.htm): The Monitoring Trends in Burn Severity project is a comprehensive fire atlas for the United States that includes perimeters and severity data for all fires greater than a particular size (~400 ha in the western US, and ~200 ha in the eastern US). Although the database was derived for management purposes, the scientific community has expressed interest in its research capacity. As with any derived data, it is critical to understand inherent limitations to maximise the utility of the dataset without compromising the inferences. The classified severity product in particular is of limited use to research due to a lack of both consistency in developing class...
Abstract (from http://onlinelibrary.wiley.com/doi/10.1002/hyp.11264/abstract): Pinyon-juniper (PJ) cover has increased up to 10-fold in many parts of the western U.S. in the last 140+ years. The impacts of these changes on streamflows are unclear and may vary depending on the intra-annual distribution and amount of precipitation. Given the importance of streamflow in the western U.S., it is important to understand how shifts in PJ woodland cover may produce changes in streamflow across the region's diverse hydroclimates. To this end, we simulated the land surface water balance with contrasting woodland and grassland cover with the Hydrologiska Byråns Vattenbalansavdelning (HBV) model at a 4-km resolution across...
Abstract (from Ecosphere): In semi‐arid mountainous regions across the western United States, the distribution of upland aspen (Populus tremuloides) is often related to heterogeneous soil moisture subsidies resulting from redistributed snow. As temperatures increase, interactions between decreasing snowpack and future trends in the net primary productivity (NPP) of aspen forests remain uncertain. This study characterizes the importance of heterogeneously distributed snow water to aspen communities in the Reynolds Creek Critical Zone Observatory located in southwestern Idaho, USA. Net primary productivity of three aspen stands was simulated at sites spanning elevational and precipitation gradients using the biogeochemical...
Abstract (from Biogeosciences): Fire is a dynamic ecological process in forests and impacts the carbon (C) cycle through direct combustion emissions, tree mortality, and by impairing the ability of surviving trees to sequester carbon. While studies on young trees have demonstrated that fire intensity is a determinant of post-fire net primary productivity, wildland fires on landscape to regional scales have largely been assumed to either cause tree mortality, or conversely, cause no physiological impact, ignoring the impacted but surviving trees. Our objective was to understand how fire intensity affects post-fire net primary productivity in conifer-dominated forested ecosystems on the spatial scale of large wildland...
Abstract (from http://www.aimspress.com/aimses/ch/reader/view_abstract.aspx?doi=10.3934/environsci.2015.2.203): Contemporary pressures on sagebrush steppe from climate change, exotic species, wildfire, and land use change threaten rangeland species such as the greater sage-grouse (Centrocercus urophasianus). To effectively manage sagebrush steppe landscapes for long-term goals, managers need information about the potential impacts of climate change, disturbances, and management activities. We integrated information from a dynamic global vegetation model, a sage-grouse habitat climate envelope model, and a state-and-transition simulation model to project broad-scale vegetation dynamics and potential sage-grouse habitat...