Fact Sheet / Brief
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Lower treelines in the Intermountain West are often defined by the boundary beyond which conditions are too dry for trees. Scientists are observing tree mortality in response to global climate changes and associated increased aridity in some places. Land managers are keenly interested in these changing ecological dynamics and how forests will shift in response to climate change.
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Extensive research shows us that native conifer trees, primarily juniper and pinyon pine, but also other conifers, have been increasing their footprint on the landscape at an unprecedented rate over the last 150 years or so, especially in places like the Great Basin. This is part of a global phenomenon of trees encroaching into and replacing adjacent grasslands and shrublands.
Some of that change is expansion in the traditional sense, that is, trees moving from higher elevations or fuel-limited sites protected from fire where they historically existed into areas where they never grew before. But much of the change is what we call ‘infill,’ which is what happens after trees colonize and continue to populate previously tree-less landscapes, turning them from sagebrush or grasslands with just a few trees per acre into closed-canopy woodlands – what you might think of as a forest.
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Large wildfires need four key ingredients to burn, not just one. Ignitions, fuels, and drought thresholds must be crossed at the same time, enhanced by anomalous weather events such as foehn winds. But how do these ingredients, or drivers, fit together in various ecosystems? In this important concept paper, Pausas and Keeley (2021) outline the mechanistic flow of these complex drivers for fire prone ecosystems and illustrate this in the figure below (Fig.1). In brief, the fire weather for a given ecosystem helps to push the other three essential driver thresholds, or saturation points, down. With ignitions, fuel continuity, and drought saturation points simultaneously lowered by the right weather, wildfire will be triggered.
WindNinja, a tool developed by RMRS scientists, delivers high-resolution wind predictions within seconds for emergency fire responders making on-the-ground decisions. The program computes spatially-varying wind fields to help predict winds at small scales in complex terrain. These predictions are extremely important in fire-prone landscapes where local changes in the near-surface wind are not predicted well by either operational weather models or expert judgment but are extremely important for accurate fire behavior predictions.
Because three key thresholds must be crossed all at once for a wildfire to start, avoiding just one of these thresholds─ ignitions, drought, or continuous fuels (Fig.1)─ could significantly reduce the likelihood of wildfire. As climate change makes fire weather more common everywhere, managing ignitions where wind is problematic and managing fuels where drought is problematic will help to keep stochastic, out-of-regime fires contained. Where fire management tools won’t help, a fire danger zone should be designated to reduce human activity and development, much like volcano or flooding zone designations.
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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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Resilience goals should be updated to better apply to 21st century ecosystems. They propose a concept of scaled resilience, which incorporates scales of time, space, and biological level of organization. By measuring disturbance and post-disturbance ecosystem responses in all three dimensions, scaled resilience models can be grounded by data that are much more useful to land managers than simple comparisons to reference site conditions.
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Making lands resilient to climate change has become a legal mandate for US Forest Service land planners (2012 USFS Planning Rule). However, interpreting and applying the directive is challenging because the term “resilience” is rather vague. It is diluted by a variety of definitions in the literature, as well as executed differently in diverse ecosystems by a variety of specialists.
To better grasp how USFS staff interpreted and applied the directive, twenty-six Southwestern Region USFS planners and mangers were interviewed for 30-60 minutes each. The semi-structured interviews were then coded to identify themes and trends. Overall, inductive content analysis of the coded interview data showed that the interviewees had three main areas of concern over the difficulty in reporting and implementing the resilience directive: 1) definitions and scale, 2) flexibility and specificity, and 3) the resilience to climate change paradox.
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Ecosystems worldwide are facing complex interacting stressors that are leading to rapid and potentially irreversible change. Many of these changes involve vegetation type-conversion in various stages and forms. A variety of terms are applied to changes in ecosystems around the world to describe some aspect of long-lasting changes in plant communities. Here we evaluate a representative list of analogous terms for processes and patterns involved in vegetation type-conversion, highlighting similarities and differences. The list illustrates a common problem in ecology, viz. how similar terminology may actually describe different aspects of complex processes. Linking this terminology under a unified, umbrella concept of vegetation type conversion and placing it into the context of an ecological resilience framework, including community reorganization, may help resolve research agendas and conservation efforts.
Weed-Suppressive Bacteria, or WSB, are bacteria strains of the soil bacterium Pseudomonas flourescens (D7, ACK55, and MB906) developed and marketed as a natural way to control exotic grasses, such as cheatgrass. In the late 1900s and early 2000s, scientists began experiments that looked for biological ways to selectively eliminate or inhibit growth of exotic annual grasses.