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  1. Article: Widespread fire years in the US–Mexico Sky Islands are contingent on both winter and monsoon precipitation

    Arizpe, Alexis H / Falk, Donald A / Woodhouse, Connie A / Swetnam, Thomas W

    International journal of wildland fire. 2020, v. 29, no. 12

    2020  

    Abstract: The climate of the south-western United States and northern Mexico borderlands is marked by a bimodal precipitation regime with the majority of moisture arriving during the cool season via Pacific frontal storm systems, and intense convective storms ... ...

    Abstract The climate of the south-western United States and northern Mexico borderlands is marked by a bimodal precipitation regime with the majority of moisture arriving during the cool season via Pacific frontal storm systems, and intense convective storms during the North American Monsoon (NAM). The fire season occurs primarily during the arid foresummer in May and June, before the development of the NAM. Most tree-ring studies of fire climatology in the region have evaluated only the role of winter precipitation. We used tree-ring-width-based reconstructions of both winter and monsoon precipitation, coupled with fire scar reconstructions of fire history from mountain ranges in the US and Mexico, to quantify the historical role and interactions of both seasons of precipitation in modulating widespread fire years. Winter precipitation was the primary driver of widespread fire years in the region, but years with drought in both seasons had the highest fire frequency and most widespread fires. These relationships define a unique monsoon fire regime, in which the timing and amount of monsoon precipitation are important factors in limiting the length of fire season and regulating widespread fire years.
    Keywords climate ; climatology ; cold season ; drought ; fire frequency ; fire history ; fire regime ; fire season ; growth rings ; monsoon season ; storms ; summer ; wildfires ; winter ; Mexico
    Language English
    Size p. 1072-1087.
    Publishing place CSIRO Publishing
    Document type Article
    Note NAL-AP-2-clean
    ZDB-ID 1331562-6
    ISSN 1448-5516 ; 1049-8001
    ISSN (online) 1448-5516
    ISSN 1049-8001
    DOI 10.1071/WF19181
    Database NAL-Catalogue (AGRICOLA)

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  2. Article ; Online: Eleventh-century shift in timber procurement areas for the great houses of Chaco Canyon.

    Guiterman, Christopher H / Swetnam, Thomas W / Dean, Jeffrey S

    Proceedings of the National Academy of Sciences of the United States of America

    2016  Volume 113, Issue 5, Page(s) 1186–1190

    Abstract: An enduring mystery from the great houses of Chaco Canyon is the origin of more than 240,000 construction timbers. We evaluate probable timber procurement areas for seven great houses by applying tree-ring width-based sourcing to a set of 170 timbers. To ...

    Abstract An enduring mystery from the great houses of Chaco Canyon is the origin of more than 240,000 construction timbers. We evaluate probable timber procurement areas for seven great houses by applying tree-ring width-based sourcing to a set of 170 timbers. To our knowledge, this is the first use of tree rings to assess timber origins in the southwestern United States. We found that the Chuska and Zuni Mountains (>75 km distant) were the most likely sources, accounting for 70% of timbers. Most notably, procurement areas changed through time. Before 1020 Common Era (CE) nearly all timbers originated from the Zunis (a previously unrecognized source), but by 1060 CE the Chuskas eclipsed the Zuni area in total wood imports. This shift occurred at the onset of Chaco florescence in the 11th century, a time with substantial expansion of existing great houses and the addition of seven new great houses in the Chaco Core area. It also coincides with the proliferation of Chuskan stone tools and pottery in the archaeological record of Chaco Canyon, further underscoring the link between land use and occupation in the Chuska area and the peak of great house construction. Our findings, based on the most temporally specific and replicated evidence of Chacoan resource procurement obtained to date, corroborate the long-standing but recently challenged interpretation that large numbers of timbers were harvested and transported from distant mountain ranges to build the great houses at Chaco Canyon.
    Language English
    Publishing date 2016-02-02
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S.
    ZDB-ID 209104-5
    ISSN 1091-6490 ; 0027-8424
    ISSN (online) 1091-6490
    ISSN 0027-8424
    DOI 10.1073/pnas.1514272112
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  3. Article ; Online: Correction for Guiterman et al., Eleventh-century shift in timber procurement areas for the great houses of Chaco Canyon.

    Guiterman, Christopher H / Swetnam, Thomas W / Dean, Jeffrey S

    Proceedings of the National Academy of Sciences of the United States of America

    2016  Volume 113, Issue 6, Page(s) E811

    Language English
    Publishing date 2016-02-09
    Publishing country United States
    Document type Published Erratum
    ZDB-ID 209104-5
    ISSN 1091-6490 ; 0027-8424
    ISSN (online) 1091-6490
    ISSN 0027-8424
    DOI 10.1073/pnas.1525340113
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Direct and indirect climate controls predict heterogeneous early-mid 21st century wildfire burned area across western and boreal North America.

    Kitzberger, Thomas / Falk, Donald A / Westerling, Anthony L / Swetnam, Thomas W

    PloS one

    2017  Volume 12, Issue 12, Page(s) e0188486

    Abstract: Predicting wildfire under future conditions is complicated by complex interrelated drivers operating across large spatial scales. Annual area burned (AAB) is a useful index of global wildfire activity. Current and antecedent seasonal climatic conditions, ...

    Abstract Predicting wildfire under future conditions is complicated by complex interrelated drivers operating across large spatial scales. Annual area burned (AAB) is a useful index of global wildfire activity. Current and antecedent seasonal climatic conditions, and the timing of snowpack melt, have been suggested as important drivers of AAB. As climate warms, seasonal climate and snowpack co-vary in intricate ways, influencing fire at continental and sub-continental scales. We used independent records of seasonal climate and snow cover duration (last date of permanent snowpack, LDPS) and cell-based Structural Equation Models (SEM) to separate direct (climatic) and indirect (snow cover) effects on relative changes in AAB under future climatic scenarios across western and boreal North America. To isolate seasonal climate variables with the greatest effect on AAB, we ran multiple regression models of log-transformed AAB on seasonal climate variables and LDPS. We used the results of multiple regressions to project future AAB using GCM ensemble climate variables and LDPS, and validated model predictions with recent AAB trends. Direct influences of spring and winter temperatures on AAB are larger and more widespread than the indirect effect mediated by changes in LDPS in most areas. Despite significant warming trends and reductions in snow cover duration, projected responses of AAB to early-mid 21st century are heterogeneous across the continent. Changes in AAB range from strongly increasing (one order of magnitude increases in AAB) to moderately decreasing (more than halving of baseline AAB). Annual wildfire area burned in coming decades is likely to be highly geographically heterogeneous, reflecting interacting regional and seasonal climate drivers of fire occurrence and spread.
    MeSH term(s) Climate ; Forecasting ; Humans ; Models, Statistical ; Regression Analysis ; Trees/growth & development ; United States ; Weather ; Wildfires/statistics & numerical data
    Language English
    Publishing date 2017-12-15
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2267670-3
    ISSN 1932-6203 ; 1932-6203
    ISSN (online) 1932-6203
    ISSN 1932-6203
    DOI 10.1371/journal.pone.0188486
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Audio / Video: Special Issue: Fire History in California

    Swetnam, Thomas W

    Fire ecology. 2009, v. 5, no. 3

    2009  

    Abstract: A common refrain that fire historians hear from managers and scientists is: “Haven’t we done enough fire history studies already, especially in ponderosa pine? What more is there to learn?” It is true that there are dozens of published studies in western ...

    Abstract A common refrain that fire historians hear from managers and scientists is: “Haven’t we done enough fire history studies already, especially in ponderosa pine? What more is there to learn?” It is true that there are dozens of published studies in western North America using tree rings to evaluate the historical range and variability of past fire regimes. It is also true that the majority of these studies were conducted in pine dominant or mixed-conifer forests where moderate to high frequency surface fire regimes prevailed for centuries before the fire suppression era.
    Keywords forest fires ; history ; fire regime ; coniferous forests ; California
    Language English
    Size p. 1-3.
    Document type Article ; Audio / Video
    ISSN 1933-9747
    Database NAL-Catalogue (AGRICOLA)

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  6. Article: Spatiotemporal variability of human–fire interactions on the Navajo Nation

    Guiterman, Christopher H / Margolis, Ellis Q / Baisan, Christopher H / Falk, Donald A / Allen, Craig D / Swetnam, Thomas W

    Ecosphere. 2019 Nov., v. 10, no. 11

    2019  

    Abstract: Unraveling the effects of climate and land use on historical fire regimes provides important insights into broader human–fire–climate dynamics, which are necessary for ecologically based forest management. We developed a spatial human land‐use model for ... ...

    Abstract Unraveling the effects of climate and land use on historical fire regimes provides important insights into broader human–fire–climate dynamics, which are necessary for ecologically based forest management. We developed a spatial human land‐use model for Navajo Nation forests across which we sampled a network of tree‐ring fire history sites to reflect contrasting historical land‐use intensity: high human use, primarily in the Chuska Mountains, and low human use, primarily on the central Defiance Plateau. We tested for and compared human‐ and climate‐driven changes in the fire regimes by applying change point detection, regression, and superposed epoch analyses. The historical fire regimes and fire–climate relationships reflect those of similar forests regionally and are similar between the two Navajo landscapes until the early 1800s. We then determined that a previously identified, localized, early (1830s) decline in fire activity was geographically widespread across higher human‐use sites. In contrast, fires continued to burn uninterrupted through this period at the lower use sites. Though the 1830s included significantly wet and cold periods that could have contributed to fire regime decline, human factors pose a more spatiotemporally consistent explanation. A rise in Navajo pastoralism in the 1820s–1830s was concentrated seasonally in the heavy use sites. By the 1880s, livestock numbers more than doubled, grazing became far more spatially widespread, and frequent fire regimes of Navajo forests collapsed. The last widespread fire recorded on either landscape was in 1886. In the Chuska Mountains, livestock and fire coexisted for over 50 yr between the initial 1832 fire decline and the end of frequent fires after 1886, an exceptional pattern in the western United States. Though unique in its timing, character, and spatial dynamics, the collapse of historical fire regimes in Navajo forests contributed to now over a century without frequent surface fire, leaving Navajo forests at risk for large, uncharacteristic high‐severity fires.
    Keywords burning ; climate ; cold ; fire history ; fire regime ; forest fires ; forest management ; forests ; geographical distribution ; grazing ; growth rings ; herd size ; humans ; land use ; landscapes ; livestock ; models ; mountains ; pastoralism ; risk ; spatial variation ; temporal variation ; New Mexico
    Language English
    Dates of publication 2019-11
    Publishing place John Wiley & Sons, Ltd
    Document type Article
    Note JOURNAL ARTICLE
    ZDB-ID 2572257-8
    ISSN 2150-8925
    ISSN 2150-8925
    DOI 10.1002/ecs2.2932
    Database NAL-Catalogue (AGRICOLA)

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  7. Article: Fire Suppression Impacts on Fuels and Fire Intensity in the Western U.S.: Insights from Archaeological Luminescence Dating in Northern New Mexico

    Roos, Christopher I. / Rittenour, Tammy M. / Swetnam, Thomas W. / Loehman, Rachel A. / Hollenback, Kacy L. / Liebmann, Matthew J. / Rosenstein, Dana Drake

    Fire. 2020 July 20, v. 3, no. 3

    2020  

    Abstract: Here, we show that the last century of fire suppression in the western U.S. has resulted in fire intensities that are unique over more than 900 years of record in ponderosa pine forests (Pinus ponderosa). Specifically, we use the heat-sensitive ... ...

    Abstract Here, we show that the last century of fire suppression in the western U.S. has resulted in fire intensities that are unique over more than 900 years of record in ponderosa pine forests (Pinus ponderosa). Specifically, we use the heat-sensitive luminescence signal of archaeological ceramics and tree-ring fire histories to show that a recent fire during mild weather conditions was more intense than anything experienced in centuries of frequent wildfires. We support this with a particularly robust set of optically stimulated luminescence measurements on pottery from an archaeological site in northern New Mexico. The heating effects of an October 2012 CE prescribed fire reset the luminescence signal in all 12 surface samples of archaeological ceramics, whereas none of the 10 samples exposed to at least 14 previous fires (1696–1893 CE) revealed any evidence of past thermal impact. This was true regardless of the fire behavior contexts of the 2012 CE samples (crown, surface, and smoldering fires). It suggests that the fuel characteristics from fire suppression at this site have no analog during the 550 years since the depopulation of this site or the 350 years of preceding occupation of the forested landscape of this region.
    Keywords Pinus ponderosa ; archaeology ; fire intensity ; fire suppression ; growth rings ; landscapes ; luminescence ; occupations ; thermosensitivity ; weather ; New Mexico
    Language English
    Dates of publication 2020-0720
    Publishing place Multidisciplinary Digital Publishing Institute
    Document type Article
    ISSN 2571-6255
    DOI 10.3390/fire3030032
    Database NAL-Catalogue (AGRICOLA)

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  8. Article ; Online: Indigenous fire management and cross-scale fire-climate relationships in the Southwest United States from 1500 to 1900 CE.

    Roos, Christopher I / Guiterman, Christopher H / Margolis, Ellis Q / Swetnam, Thomas W / Laluk, Nicholas C / Thompson, Kerry F / Toya, Chris / Farris, Calvin A / Fulé, Peter Z / Iniguez, Jose M / Kaib, J Mark / O'Connor, Christopher D / Whitehair, Lionel

    Science advances

    2022  Volume 8, Issue 49, Page(s) eabq3221

    Abstract: Prior research suggests that Indigenous fire management buffers climate influences on wildfires, but it is unclear whether these benefits accrue across geographic scales. We use a network of 4824 fire-scarred trees in Southwest United States dry forests ... ...

    Abstract Prior research suggests that Indigenous fire management buffers climate influences on wildfires, but it is unclear whether these benefits accrue across geographic scales. We use a network of 4824 fire-scarred trees in Southwest United States dry forests to analyze up to 400 years of fire-climate relationships at local, landscape, and regional scales for traditional territories of three different Indigenous cultures. Comparison of fire-year and prior climate conditions for periods of intensive cultural use and less-intensive use indicates that Indigenous fire management weakened fire-climate relationships at local and landscape scales. This effect did not scale up across the entire region because land use was spatially and temporally heterogeneous at that scale. Restoring or emulating Indigenous fire practices could buffer climate impacts at local scales but would need to be repeatedly implemented at broad scales for broader regional benefits.
    Language English
    Publishing date 2022-12-07
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2810933-8
    ISSN 2375-2548 ; 2375-2548
    ISSN (online) 2375-2548
    ISSN 2375-2548
    DOI 10.1126/sciadv.abq3221
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  9. Article ; Online: Native American fire management at an ancient wildland-urban interface in the Southwest United States.

    Roos, Christopher I / Swetnam, Thomas W / Ferguson, T J / Liebmann, Matthew J / Loehman, Rachel A / Welch, John R / Margolis, Ellis Q / Guiterman, Christopher H / Hockaday, William C / Aiuvalasit, Michael J / Battillo, Jenna / Farella, Joshua / Kiahtipes, Christopher A

    Proceedings of the National Academy of Sciences of the United States of America

    2021  Volume 118, Issue 4

    Abstract: The intersection of expanding human development and wildland landscapes-the "wildland-urban interface" or WUI-is one of the most vexing contexts for fire management because it involves complex interacting systems of people and nature. Here, we document ... ...

    Abstract The intersection of expanding human development and wildland landscapes-the "wildland-urban interface" or WUI-is one of the most vexing contexts for fire management because it involves complex interacting systems of people and nature. Here, we document the dynamism and stability of an ancient WUI that was apparently sustainable for more than 500 y. We combine ethnography, archaeology, paleoecology, and ecological modeling to infer intensive wood and fire use by Native American ancestors of Jemez Pueblo and the consequences on fire size, fire-climate relationships, and fire intensity. Initial settlement of northern New Mexico by Jemez farmers increased fire activity within an already dynamic landscape that experienced frequent fires. Wood harvesting for domestic fuel and architectural uses and abundant, small, patchy fires created a landscape that burned often but only rarely burned extensively. Depopulation of the forested landscape due to Spanish colonial impacts resulted in a rebound of fuels accompanied by the return of widely spreading, frequent surface fires. The sequence of more than 500 y of perennial small fires and wood collecting followed by frequent "free-range" wildland surface fires made the landscape resistant to extreme fire behavior, even when climate was conducive and surface fires were large. The ancient Jemez WUI offers an alternative model for fire management in modern WUI in the western United States, and possibly other settings where local management of woody fuels through use (domestic wood collecting) coupled with small prescribed fires may make these communities both self-reliant and more resilient to wildfire hazards.
    Language English
    Publishing date 2021-01-19
    Publishing country United States
    Document type Journal Article ; Research Support, U.S. Gov't, Non-P.H.S.
    ZDB-ID 209104-5
    ISSN 1091-6490 ; 0027-8424
    ISSN (online) 1091-6490
    ISSN 0027-8424
    DOI 10.1073/pnas.2018733118
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  10. Article: Disturbance and productivity interactions mediate stability of forest composition and structure.

    O'Connor, Christopher D / Falk, Donald A / Lynch, Ann M / Swetnam, Thomas W / Wilcox, Craig P

    Ecological applications : a publication of the Ecological Society of America

    2017  Volume 27, Issue 3, Page(s) 900–915

    Abstract: Fire is returning to many conifer-dominated forests where species composition and structure have been altered by fire exclusion. Ecological effects of these fires are influenced strongly by the degree of forest change during the fire-free period. ... ...

    Abstract Fire is returning to many conifer-dominated forests where species composition and structure have been altered by fire exclusion. Ecological effects of these fires are influenced strongly by the degree of forest change during the fire-free period. Response of fire-adapted species assemblages to extended fire-free intervals is highly variable, even in communities with similar historical fire regimes. This variability in plant community response to fire exclusion is not well understood; however, ecological mechanisms such as individual species' adaptations to disturbance or competition and underlying site characteristics that facilitate or impede establishment and growth have been proposed as potential drivers of assemblage response. We used spatially explicit dendrochronological reconstruction of tree population dynamics and fire regimes to examine the influence of historical disturbance frequency (a proxy for adaptation to disturbance or competition), and potential site productivity (a proxy for underlying site characteristics) on the stability of forest composition and structure along a continuous ecological gradient of pine, dry mixed-conifer, mesic mixed-conifer, and spruce-fir forests following fire exclusion. While average structural density increased in all forests, species composition was relatively stable in the lowest productivity pine-dominated and highest productivity spruce-fir-dominated sites immediately following fire exclusion and for the next 100 years, suggesting site productivity as a primary control on species composition and structure in forests with very different historical fire regimes. Species composition was least stable on intermediate productivity sites dominated by mixed-conifer forests, shifting from primarily fire-adapted species to competition-adapted, fire-sensitive species within 20 years of fire exclusion. Rapid changes to species composition and stand densities have been interpreted by some as evidence of high-severity fire. We demonstrate that the very different ecological process of fire exclusion can produce similar changes by shifting selective pressures from disturbance-mediated to productivity-mediated controls. Restoring disturbance-adapted species composition and structure to intermediate productivity forests may help to buffer them against projected increasing temperatures, lengthening fire seasons, and more frequent and prolonged moisture stress. Fewer management options are available to promote adaptation in forest assemblages historically constrained by underlying site productivity.
    MeSH term(s) Arizona ; Biodiversity ; Conservation of Natural Resources ; Fires ; Forestry ; Forests ; Models, Biological ; Population Dynamics ; Trees
    Language English
    Publishing date 2017-03-15
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S.
    ZDB-ID 1074505-1
    ISSN 1939-5582 ; 1051-0761
    ISSN (online) 1939-5582
    ISSN 1051-0761
    DOI 10.1002/eap.1492
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