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  1. Article: Dating the origins of persistent oak shrubfields in northern New Mexico using soil charcoal and dendrochronology

    Roos, Christopher I / Guiterman, Christopher H

    Holocene. 2021 July, v. 31, no. 7

    2021  

    Abstract: Megafires in dry conifer forests of the Southwest US are driving transitions to alternative vegetative states, including extensive shrubfields dominated by Gambel oak (Quercus gambelii). Recent tree-ring research on oak shrubfields that predate the 20th ... ...

    Abstract Megafires in dry conifer forests of the Southwest US are driving transitions to alternative vegetative states, including extensive shrubfields dominated by Gambel oak (Quercus gambelii). Recent tree-ring research on oak shrubfields that predate the 20th century suggests that these are not a seral stage of conifer succession but are enduring stable states that can persist for centuries. Here we combine soil charcoal radiocarbon dating with tree-ring evidence to refine the fire origin dates for three oak shrubfields (<300 ha) in the Jemez Mountains of northern New Mexico and test three hypotheses that shrubfields were established by tree-killing fires caused by (1) megadrought; (2) forest infilling associated with decadal-scale climate influences on fire spread; or (3) anthropogenic interruptions of fire spread. Integrated tree-ring and radiocarbon evidence indicate that one shrubfield established in 1664 CE, another in 1522 CE, and the third long predated the oldest tree-ring evidence, establishing sometime prior to 1500 CE. Although megadrought alone was insufficient to drive the transitions to shrub-dominated states, a combination of drought and anthropogenic impacts on fire spread may account for the origins of all three shrub patches. Our study shows that these shrubfields can persist >500 years, meaning modern forest-shrub conversion of patches as large as >10,000 ha will likely persist for centuries.
    Keywords Holocene epoch ; Quercus gambelii ; carbon radioisotopes ; charcoal ; climate ; conifers ; dendrochronology ; drought ; fire spread ; growth rings ; shrubs ; soil ; New Mexico
    Language English
    Dates of publication 2021-07
    Size p. 1212-1220.
    Publishing place SAGE Publications
    Document type Article
    Note NAL-AP-2-clean
    ZDB-ID 2027956-5
    ISSN 1477-0911 ; 0959-6836
    ISSN (online) 1477-0911
    ISSN 0959-6836
    DOI 10.1177/09596836211003255
    Database NAL-Catalogue (AGRICOLA)

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  2. Article: dfoliatR: An R package for detection and analysis of insect defoliation signals in tree rings

    Guiterman, Christopher H / Lynch, Ann M / Axelson, Jodi N

    Dendrochronologia. 2020 Oct., v. 63

    2020  

    Abstract: We present a new R package to provide dendroecologists with tools to infer, quantify, analyze, and visualize growth suppression events in tree rings. dfoliatR is based on the OUTBREAK program and builds on existing resources in the R computing ... ...

    Abstract We present a new R package to provide dendroecologists with tools to infer, quantify, analyze, and visualize growth suppression events in tree rings. dfoliatR is based on the OUTBREAK program and builds on existing resources in the R computing environment and the well-used dplR package. It is designed to aid research in the ecology of insect defoliation events and to reconstruct defoliator outbreak chronologies, but can be applied to other studies where host–non-host comparisons are useful. dfoliatR performs an indexing procedure to remove climatic signals in the host-tree series that are represented in the non-host chronology, or other annually-resolved climate series. It then infers defoliation events in individual trees based on user-specified thresholds. Site-level analyses identify outbreak events that synchronously affect user-defined numbers or proportions of involved host trees. Functions are provided for summary statistics and graphics of tree- and site-level series. We evaluated dfoliatR against OUTBREAK, using eight datasets including 222 host-trees, and found that dfoliatR improves on OUTBREAK with greater user control, identification of defoliation events, computing capacity, and both the statistical summary and graphical outputs. We provide two example data sets and script to enable users to gain familiarity with the package and its capabilities. The source code is available in the Comprehensive R Archive Network (CRAN) and on GitHub.
    Keywords climate ; data collection ; defoliating insects ; defoliation ; detection ; environment ; growth rings ; research ; statistics ; trees
    Language English
    Dates of publication 2020-10
    Publishing place Elsevier GmbH
    Document type Article
    Note NAL-light
    ZDB-ID 2088117-4
    ISSN 1612-0051 ; 1125-7865
    ISSN (online) 1612-0051
    ISSN 1125-7865
    DOI 10.1016/j.dendro.2020.125750
    Database NAL-Catalogue (AGRICOLA)

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  3. Article: A history of recurrent, low-severity fire without fire exclusion in southeastern pine savannas, USA

    Rother, Monica T / Huffman, Jean M / Guiterman, Christopher H / Robertson, Kevin M / Jones, Neil

    Forest ecology and management. 2020 Nov. 01, v. 475

    2020  

    Abstract: The reintroduction and maintenance of historical surface fire regimes are primary goals of ecological restoration across many open, pine-dominated ecosystems in North America. In the United States, most of these ecosystems experienced long periods of ... ...

    Abstract The reintroduction and maintenance of historical surface fire regimes are primary goals of ecological restoration across many open, pine-dominated ecosystems in North America. In the United States, most of these ecosystems experienced long periods of fire exclusion in the 20th century, leaving few locations to serve as reference sites for ecological conditions associated with a continuous history of recurrent, low-severity fire. Here, we present a tree-ring perspective of uninterrupted surface fire activity from three pine savanna sites in the Red Hills Region of northern Florida and southwestern Georgia, USA. Our sites include two old-growth stands of longleaf pine (Pinus palustris): the Wade Tract on Arcadia Plantation and the Larkin Tract on Millpond Plantation. We also sampled the largely second-growth mixed pine savannas of Tall Timbers Research Station. Documentary records for burning at these sites are limited to recent decades and are often incomplete, although regional land-use traditions and scattered historical records indicate frequent fire may have persisted through the 20th century to present day. Fire-scarred cross sections from externally-scarred stumps, dead trees, and live trees provided tree-ring evidence of frequent fires occurring from the beginning of our fire-scar record in the late 19th century onward. Both fire frequency and seasonality were relatively consistent throughout time and among sites. Biennial and annual fire intervals were the most common. Most fire scars occurred in the dormant and early-earlywood portions of the rings, indicating that these fires were human-set fires during the months of January to mid-April, before the main lightning-fire season. Our findings regarding post-settlement fire frequency are consistent with previous estimates of fire frequency during earlier centuries, resulting from lightning and Native American ignitions. We recommend that our sites be used as reference sites for restoration as they are among the relatively few areas in the United States with a continuous history of frequent low-severity fire without 20th century fire exclusion.
    Keywords Pinus palustris ; administrative management ; ecological restoration ; fire frequency ; growth rings ; land use ; lightning ; savannas ; second growth ; Florida ; Georgia
    Language English
    Dates of publication 2020-1101
    Publishing place Elsevier B.V.
    Document type Article
    Note NAL-AP-2-clean
    ZDB-ID 751138-3
    ISSN 0378-1127
    ISSN 0378-1127
    DOI 10.1016/j.foreco.2020.118406
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  4. Article: Mechanisms of forest resilience

    Falk, Donald A / van Mantgem, Philip J / Keeley, Jon E / Gregg, Rachel M / Guiterman, Christopher H / Tepley, Alan J / JN Young, Derek / Marshall, Laura A

    Elsevier B.V. Forest ecology and management. 2022 May 15, v. 512

    2022  

    Abstract: Ecosystems are dynamic systems with complex responses to environmental variation. In response to pervasive stressors of changing climate and disturbance regimes, many ecosystems are realigning rapidly across spatial scales, in many cases moving outside ... ...

    Abstract Ecosystems are dynamic systems with complex responses to environmental variation. In response to pervasive stressors of changing climate and disturbance regimes, many ecosystems are realigning rapidly across spatial scales, in many cases moving outside of their observed historical range of variation into alternative ecological states. In some cases, these new states are transitory and represent successional stages that may ultimately revert to the pre-disturbance condition; in other cases, alternative states are persistent and potentially self-reinforcing, especially under conditions of altered climate, disturbance regimes, and influences of non-native species. These reorganized states may appear novel, but reorganization is a characteristic ecosystem response to environmental variation that has been expressed and documented throughout the paleoecological record. Resilience, the ability of an ecosystem to recover or adapt following disturbance, is an emergent property that results from the expression of multiple mechanisms operating across levels of organism, population, and community. We outline a unifying framework of ecological resilience based on ecological mechanisms that lead to outcomes of persistence, recovery, and reorganization. Persistence is the ability of individuals to tolerate exposure to environmental stress, disturbance, or competitive interactions. As a direct expression of life history evolution and adaptation to environmental variation and stress, persistence is manifested most directly in survivorship and continued growth and reproduction of established individuals. When persistence has been overcome (e.g., following mortality from stress, disturbance, or both), populations must recover by reproduction. Recovery requires the establishment of new individuals from seed or other propagules following dispersal from the parent plant. When recovery fails to re-establish the pre-disturbance community, the ecosystem will assemble into a new state. Reorganization occurs along a gradient of magnitude, from changes in the relative dominance of species present in a community, to individual species replacements within an essentially intact community, to complete species turnover and shift to dominance by plants of different functional types, e.g. transition from forest to shrub or grass dominance. When this latter outcome is persistent and involves reinforcing mechanisms, the resulting state represents a vegetation type conversion (VTC), which in this framework represents an end member of reorganization processes. We explore reorganization in greater detail as this phase is increasingly observed but the least understood of the resilience responses. This resilience framework provides a direct and actionable basis for ecosystem management in a rapidly changing world, by targeting specific components of ecological response and managing for sustainable change.
    Keywords administrative management ; climate ; ecological resilience ; ecosystem management ; ecosystems ; environmental factors ; forest ecology ; forests ; grasses ; introduced species ; life history ; paleoecology ; reproduction ; shrubs ; survival rate
    Language English
    Dates of publication 2022-0515
    Publishing place Elsevier B.V.
    Document type Article
    ZDB-ID 751138-3
    ISSN 0378-1127
    ISSN 0378-1127
    DOI 10.1016/j.foreco.2022.120129
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  5. 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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  6. 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
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  7. 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
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  8. Article: Long-Term Persistence and Fire Resilience of Oak Shrubfields in Dry Conifer Forests of Northern New Mexico

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

    Ecosystems. 2018 Aug., v. 21, no. 5

    2018  

    Abstract: Extensive high-severity fires are creating large shrubfields in many dry conifer forests of the interior western USA, raising concerns about forest-to-shrub conversion. This study evaluates the role of disturbance in shrubfield formation, maintenance and ...

    Abstract Extensive high-severity fires are creating large shrubfields in many dry conifer forests of the interior western USA, raising concerns about forest-to-shrub conversion. This study evaluates the role of disturbance in shrubfield formation, maintenance and succession in the Jemez Mountains, New Mexico. We compared the environmental conditions of extant Gambel oak (Quercus gambelii) shrubfields with adjoining dry conifer forests and used dendroecological methods to determine the multi-century fire history and successional dynamics of five of the largest shrubfields (76–340 ha). Across the study area, 349 shrubfields (5–368 ha) occur in similar topographic and climate settings as dry conifer forests. This suggests disturbance, rather than other biophysical factors, may explain their origins and persistence. Gambel oak ages and tree-ring fire scars in our sampled shrubfields indicate they historically (1664–1899) burned concurrently with adjoining conifer forests and have persisted for over 115 years in the absence of fire. Aerial imagery from 1935 confirmed almost no change in sampled shrubfield patch sizes or boundaries over the twentieth century. The largest shrubfield we identified is less than 4% the size of the largest conifer-depleted and substantially shrub-dominated area recently formed in the Jemez following extensive high-severity wildfires, indicating considerable departure from historical patterns and processes. Projected hotter droughts and increasingly large high-severity fires could trigger more forest-to-shrub transitions and maintain existing shrubfields, inhibiting conifer forest recovery. Restoration of surface fire regimes and associated historical forest structures likely could reduce the rate and patch size of dry conifer forests being converted to shrubfields.
    Keywords climate ; coniferous forests ; dendroecology ; drought ; environmental factors ; fire history ; fire regime ; fire scars ; growth rings ; mountains ; Quercus gambelii ; remote sensing ; topography ; wildfires ; New Mexico
    Language English
    Dates of publication 2018-08
    Size p. 943-959.
    Publishing place Springer US
    Document type Article
    ZDB-ID 1428921-0
    ISSN 1435-0629 ; 1432-9840
    ISSN (online) 1435-0629
    ISSN 1432-9840
    DOI 10.1007/s10021-017-0192-2
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  9. 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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  10. 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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