Wildfire and drought moderate the spatial elements of tree mortality

Tucker J. Furniss; Andrew J. Larson; Van R. Kane; James A. Lutz

doi:10.1002/ecs2.3214

Wildfire and drought moderate the spatial elements of tree mortality

Tucker J. Furniss
, Andrew J. Larson
, Van R. Kane
, James A. Lutz

Forest Management

Research output: Contribution to journal › Article › peer-review

47 Scopus citations

Abstract

Background tree mortality is a complex process that requires large sample sizes and long timescales to disentangle the suite of ecological factors that collectively contribute to tree stress, decline, and eventual mortality. Tree mortality associated with acute disturbance events, in contrast, is conspicuous and frequently studied, but there remains a lack of research regarding the role of background mortality processes in mediating the severity and delayed effects of disturbance. We conducted an empirical study by measuring the rates, causes, and spatial pattern of mortality annually among 32,989 individual trees within a large forest demography plot in the Sierra Nevada. We characterized the relationships between background mortality, compound disturbances (fire and drought), and forest spatial structure, and we integrated our findings with a synthesis of the existing literature from around the world to develop a conceptual framework describing the spatio-temporal signatures of background and disturbance-related tree mortality. The interactive effects of fire, drought, and background mortality processes altered the rate, spatial structuring, and ecological consequences of mortality. Before fire, spatially non-random mortality was only evident among small (1 < cm DBH ≤ 10)- and medium (10 < cm DBH ≤ 60)-diameter classes; mortality rates were low (1.7% per yr), and mortality was density-dependent among small-diameter trees. Direct fire damage caused the greatest number of moralities (70% of stems ≥1 cm DBH), but the more enduring effects of this disturbance on the demography and spatial pattern of large-diameter trees occurred during the post-fire mortality regime. The combined effects of disturbance and biotic mortality agents provoked density-dependent mortality among large-diameter (≥60 cm DBH) trees, eliciting a distinct post-disturbance mortality regime that did not resemble the pattern of either pre-fire mortality or direct fire effects. The disproportionate ecological significance of the largest trees renders this mortality regime acutely consequential to the long-term structure and function of forests.

Original language	English
Article number	e03214
Journal	Ecosphere
Volume	11
Issue number	8
DOIs	https://doi.org/10.1002/ecs2.3214
State	Published - Aug 1 2020

Funding

Funding was provided by the Joint Fire Science Program (award 16–1‐04–02), the National Park Service (Awards P14AC00122 and P14AC00197), the Ecology Center at Utah State University, and the Utah Agricultural Extension Station at Utah State University which has designated this as journal paper number #9190. We thank Yosemite National Park for logistical assistance and the Yosemite Forest Dynamics Plot field crews, students, and volunteers (listed individually at http://yfdp.org ) for their work. We particularly thank Mark Swanson for his persistent commitment to the YFDP, Sara Germain for her helpful comments throughout the study, Nate Stephenson for his support of our work in the YFDP and for sharing an early version of the pathology examination protocol with us, and two anonymous reviewers for their suggestions on a previous version of this manuscript. This work was performed under National Park Service research permits YOSE‐2010‐SCI‐0003, YOSE‐2011‐SCI‐0015, YOSE‐2012‐SCI‐0061, YOSE‐2013‐SCI‐0012, YOSE2014‐SCI‐0005, YOSE‐2015‐SCI‐0014, YOSE‐2016‐SCI‐0006, YOSE‐2017‐SCI‐0009, and YOSE‐2018‐SCI‐0006 for study YOSE‐0051. The Yosemite Forest Dynamics Plot was made possible by a grant from Jennifer Walston Johnson to the Smithsonian ForestGEO. Funding was provided by the Joint Fire Science Program (award 16?1-04?02), the National Park Service (Awards P14AC00122 and P14AC00197), the Ecology Center at Utah State University, and the Utah Agricultural Extension Station at Utah State University which has designated this as journal paper number #9190. We thank Yosemite National Park for logistical assistance and the Yosemite Forest Dynamics Plot field crews, students, and volunteers (listed individually at http://yfdp.org) for their work. We particularly thank Mark Swanson for his persistent commitment to the YFDP, Sara Germain for her helpful comments throughout the study, Nate Stephenson for his support of our work in the YFDP and for sharing an early version of the pathology examination protocol with us, and two anonymous reviewers for their suggestions on a previous version of this manuscript. This work was performed under National Park Service research permits YOSE-2010-SCI-0003, YOSE-2011-SCI-0015, YOSE-2012-SCI-0061, YOSE-2013-SCI-0012, YOSE2014-SCI-0005, YOSE-2015-SCI-0014, YOSE-2016-SCI-0006, YOSE-2017-SCI-0009, and YOSE-2018-SCI-0006 for study YOSE-0051. The Yosemite Forest Dynamics Plot was made possible by a grant from Jennifer Walston Johnson to the Smithsonian ForestGEO.

Funders	Funder number
9190
Utah State University
YOSE-2015-SCI-0014, YOSE-2011-SCI-0015, YOSE-2013-SCI-0012, YOSE-2018-SCI-0006, YOSE-2012-SCI-0061, YOSE-0051, YOSE-2016-SCI-0006, YOSE2014-SCI-0005, YOSE-2010-SCI-0003, YOSE-2017-SCI-0009
P14AC00122, P14AC00197

Keywords

Smithsonian ForestGEO
Yosemite Forest Dynamics Plot
bark beetles
density dependence
distance dependence
drought
fire effects
forest ecology
large-diameter trees
spatial patterns
tree mortality
wildfire

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10.1002/ecs2.3214

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title = "Wildfire and drought moderate the spatial elements of tree mortality",

abstract = "Background tree mortality is a complex process that requires large sample sizes and long timescales to disentangle the suite of ecological factors that collectively contribute to tree stress, decline, and eventual mortality. Tree mortality associated with acute disturbance events, in contrast, is conspicuous and frequently studied, but there remains a lack of research regarding the role of background mortality processes in mediating the severity and delayed effects of disturbance. We conducted an empirical study by measuring the rates, causes, and spatial pattern of mortality annually among 32,989 individual trees within a large forest demography plot in the Sierra Nevada. We characterized the relationships between background mortality, compound disturbances (fire and drought), and forest spatial structure, and we integrated our findings with a synthesis of the existing literature from around the world to develop a conceptual framework describing the spatio-temporal signatures of background and disturbance-related tree mortality. The interactive effects of fire, drought, and background mortality processes altered the rate, spatial structuring, and ecological consequences of mortality. Before fire, spatially non-random mortality was only evident among small (1 < cm DBH ≤ 10)- and medium (10 < cm DBH ≤ 60)-diameter classes; mortality rates were low (1.7\% per yr), and mortality was density-dependent among small-diameter trees. Direct fire damage caused the greatest number of moralities (70\% of stems ≥1 cm DBH), but the more enduring effects of this disturbance on the demography and spatial pattern of large-diameter trees occurred during the post-fire mortality regime. The combined effects of disturbance and biotic mortality agents provoked density-dependent mortality among large-diameter (≥60 cm DBH) trees, eliciting a distinct post-disturbance mortality regime that did not resemble the pattern of either pre-fire mortality or direct fire effects. The disproportionate ecological significance of the largest trees renders this mortality regime acutely consequential to the long-term structure and function of forests.",

keywords = "Smithsonian ForestGEO, Yosemite Forest Dynamics Plot, bark beetles, density dependence, distance dependence, drought, fire effects, forest ecology, large-diameter trees, spatial patterns, tree mortality, wildfire",

author = "Furniss, \{Tucker J.\} and Larson, \{Andrew J.\} and Kane, \{Van R.\} and Lutz, \{James A.\}",

note = "Publisher Copyright: {\textcopyright} 2020 The Authors.",

year = "2020",

month = aug,

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doi = "10.1002/ecs2.3214",

language = "English",

volume = "11",

journal = "Ecosphere",

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TY - JOUR

T1 - Wildfire and drought moderate the spatial elements of tree mortality

AU - Furniss, Tucker J.

AU - Larson, Andrew J.

AU - Kane, Van R.

AU - Lutz, James A.

PY - 2020/8/1

Y1 - 2020/8/1

N2 - Background tree mortality is a complex process that requires large sample sizes and long timescales to disentangle the suite of ecological factors that collectively contribute to tree stress, decline, and eventual mortality. Tree mortality associated with acute disturbance events, in contrast, is conspicuous and frequently studied, but there remains a lack of research regarding the role of background mortality processes in mediating the severity and delayed effects of disturbance. We conducted an empirical study by measuring the rates, causes, and spatial pattern of mortality annually among 32,989 individual trees within a large forest demography plot in the Sierra Nevada. We characterized the relationships between background mortality, compound disturbances (fire and drought), and forest spatial structure, and we integrated our findings with a synthesis of the existing literature from around the world to develop a conceptual framework describing the spatio-temporal signatures of background and disturbance-related tree mortality. The interactive effects of fire, drought, and background mortality processes altered the rate, spatial structuring, and ecological consequences of mortality. Before fire, spatially non-random mortality was only evident among small (1 < cm DBH ≤ 10)- and medium (10 < cm DBH ≤ 60)-diameter classes; mortality rates were low (1.7% per yr), and mortality was density-dependent among small-diameter trees. Direct fire damage caused the greatest number of moralities (70% of stems ≥1 cm DBH), but the more enduring effects of this disturbance on the demography and spatial pattern of large-diameter trees occurred during the post-fire mortality regime. The combined effects of disturbance and biotic mortality agents provoked density-dependent mortality among large-diameter (≥60 cm DBH) trees, eliciting a distinct post-disturbance mortality regime that did not resemble the pattern of either pre-fire mortality or direct fire effects. The disproportionate ecological significance of the largest trees renders this mortality regime acutely consequential to the long-term structure and function of forests.

AB - Background tree mortality is a complex process that requires large sample sizes and long timescales to disentangle the suite of ecological factors that collectively contribute to tree stress, decline, and eventual mortality. Tree mortality associated with acute disturbance events, in contrast, is conspicuous and frequently studied, but there remains a lack of research regarding the role of background mortality processes in mediating the severity and delayed effects of disturbance. We conducted an empirical study by measuring the rates, causes, and spatial pattern of mortality annually among 32,989 individual trees within a large forest demography plot in the Sierra Nevada. We characterized the relationships between background mortality, compound disturbances (fire and drought), and forest spatial structure, and we integrated our findings with a synthesis of the existing literature from around the world to develop a conceptual framework describing the spatio-temporal signatures of background and disturbance-related tree mortality. The interactive effects of fire, drought, and background mortality processes altered the rate, spatial structuring, and ecological consequences of mortality. Before fire, spatially non-random mortality was only evident among small (1 < cm DBH ≤ 10)- and medium (10 < cm DBH ≤ 60)-diameter classes; mortality rates were low (1.7% per yr), and mortality was density-dependent among small-diameter trees. Direct fire damage caused the greatest number of moralities (70% of stems ≥1 cm DBH), but the more enduring effects of this disturbance on the demography and spatial pattern of large-diameter trees occurred during the post-fire mortality regime. The combined effects of disturbance and biotic mortality agents provoked density-dependent mortality among large-diameter (≥60 cm DBH) trees, eliciting a distinct post-disturbance mortality regime that did not resemble the pattern of either pre-fire mortality or direct fire effects. The disproportionate ecological significance of the largest trees renders this mortality regime acutely consequential to the long-term structure and function of forests.

KW - Smithsonian ForestGEO

KW - Yosemite Forest Dynamics Plot

KW - bark beetles

KW - density dependence

KW - distance dependence

KW - drought

KW - fire effects

KW - forest ecology

KW - large-diameter trees

KW - spatial patterns

KW - tree mortality

KW - wildfire

UR - https://www.scopus.com/pages/publications/85089985001

U2 - 10.1002/ecs2.3214

DO - 10.1002/ecs2.3214

M3 - Article

AN - SCOPUS:85089985001

SN - 2150-8925

VL - 11

JO - Ecosphere

JF - Ecosphere

IS - 8

M1 - e03214

ER -

Wildfire and drought moderate the spatial elements of tree mortality

Abstract

Funding

Keywords

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