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Phillip van Mantgem

A century of fire exclusion across many forest types in the western U.S. has resulted in unforeseen changes, including high fuel accumulations, high densities of trees, and increasing dominance of fire-intolerant species. These changes are particularly acute in forests that historically experienced high frequency and low severity fires. In response, the NPS Pacific-West region supports a large prescribed fire program to reduce understory fuels and forest density. Prescribed fire has been generally successful at reducing understory fuels and threats of catastrophic fire, and treated stands are expected to be more resistant to future wildfire. Less well understood is how well prescribed fire confers resistance to...
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Can Prescribed Fire Help Forests Survive Drought in the Sierra Nevada Mountains?
In 2017, California was experiencing its most severe drought in over a millennia. Low rainfall and record high temperatures resulted in increased tree mortality and complete forest diebacks across the West. Though land managers scrambled to respond, they lacked information needed to make informed decisions. Focusing on California’s central and southern Sierra Nevada Mountains, this project seeks to determine whether a key forest management practice – forest thinning via prescribed fire – can help forests better survive drought. Prescribed fire is commonly used in the western U.S. to remove potential wildfire fuel, such as small trees and shrubs. It is also thought that this act of selectively removing trees helps...
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This data consists of observations of individual trees in western US national parks and forests. Information on individual trees include species identity, measurements of tree size, current status (live or dead), local competition, and growth metrics based on tree rings. The data also includes estimates of plot-level characteristics.
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Understanding Fire-caused Vegetation Type Conversion in Southwestern Conifer Forests under Current and Future Climate Conditions
Fire size, frequency, overall area burned, and severity are increasing across many vegetation types in the southwestern U.S. In many cases, large contiguous areas are burning repeatedly at high severity, triggering vegetation type conversions (VTC), where once-dominant coniferous forests fail to return to their pre-fire state, often transitioning to shrub- or grass-dominated systems. Loss of these forests affects biodiversity, ecosystem services, and culturally-valued resources. The science and management communities, however, currently lack a comprehensive understanding of VTC in this region. This study will help identify and fill sizable research gaps by synthesizing manager observations and the current scientific...
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How Does Drought Influence Fire Severity in the Southwestern U.S.?
There is a growing realization that current warming trends may be associated with increases in the size, frequency, and severity of forest fires in the West. While rising temperatures can create drought conditions that favor severe fires, it is also possible that drought limits the ability of trees to survive a fire. During a drought, there is less water available for trees and more outbreaks of harmful insects and pathogens can occur, both of which can weaken trees. Tree mortality is one means of measuring the severity of a fire, and evidence shows that trees exposed to drought conditions for periods of 5-10 years are already more sensitive to the effects of fire – suggesting that drought could indeed increase...
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