Article

Fire, Drought, and Humans in a Heterogeneous Lake Superior Landscape

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Abstract

We used dendrochronology and historic data to examine spatial and temporal variation in the historic fire regime of a complex landscape adjacent to Lake Superior in the Huron Mountains, Michigan, USA. Across the study area, 330 dated fire scars were identified and cross-dated from 115 trees and seven sites, spanning the years 1439–2005. Most of the fires were small in spatial extent; larger fires were infrequent and occurred primarily in level landscape positions within 1.5 km of Lake Superior. Small, frequent fires also occurred at the higher elevations attributable to lightning ignitions. The mean fire interval (MFI) from 1439–1751 was 49 yr and then abruptly shortened to 18.5 yr until the 1900s, during which time the MFI across all sites was greater than 78 yr. From 1752–1900s, high fire frequency occurred even in relatively wet years, suggesting an increased human influence. We interpret these patterns in fire intervals in the context of topography and changes in human population, land use, and cultural perspectives on fire.

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... Climate, fuel availability, fire exclusion, and fire suppression are often considered the primary controls on 20th-century fire occurrence in the Great Lakes Region (Heinselman 1996, Meunier et al. 2019b. A diminished role of traditional Indigenous landuse as a source of frequent fire can also explain changes in fire occurrence over the last century in many places (Anderton 1999, Muzika et al. 2015, Guyette et al. 2016, Kipfmueller et al. 2017) and has important implications for understanding the eco-cultural factors that led to the diminished presence of red pine on the landscape since Euro-American colonization (Buckman et al. 2006). More place-based fire history records are needed to characterize and call attention to the complexities of historical red pine fire regimes and provide resource managers actionable metrics to guide the reintroduction of fire to the region's fire-adapted landscapes. ...
... Heinselman acknowledged the potential for humans to augment fire occurrence but considered the answer to this question unobtainable from the available records (Heinselman and Wright 1973:325). Recent research in the Border Lakes Region (Johnson and Kipfmueller 2016, Kipfmueller et al. 2017, Larson et al. 2019) and broader Great Lakes Region (Muzika et al. 2015, Guyette et al. 2016, however, documented widespread evidence of surface fires, particularly in upland-lakeshore environments, suggestive of people as an important driver of past fire activity. ...
... employed differences in scale and our site classification to determine whether variations in fire-climate relationships existed among our sites that could indicate the influence of people on the historical fire regime. At inter-annual scales, if human agency played a significant role in driving fire events, it would be expected that sites with greater hypothesized human influence might have a weaker fire-climate relationship (Muzika et al. 2015). Among our sites in the BWCAW, this would translate to stronger fireclimate relationships at off-route sites where human activities were hypothesized to be less intense, and weaker fire-climate relationships at on-route sites where human actions would carry greater influence, perhaps masking or limiting climate as a driver of fire activity. ...
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Article
The Border Lakes Region of Minnesota and Ontario has long been viewed as a fire‐dependent ecosystem. High‐severity fire in the region's near‐boreal forests has been a focus of ecological research and public fascination. However, the surface fire history within this transnational wilderness landscape has received more limited attention. We used an interdisciplinary, dendroecological approach to characterize the surface fire history of the region, assess potential drivers of historical surface fires, and document the ecological legacies of frequent fires within the red pine forests of the Boundary Waters Canoe Area Wilderness (BWCAW) in northern Minnesota. We used tree‐ring and fire atlas data to reconstruct multi‐century surface fire records for 101 sites and document age structure and composition at 32 sites across the BWCAW. Stratification of these sites relative to their proximity to a primary travel and trade corridor used first by Indigenous groups and later by Euro‐American fur traders through the late 1800s provided strong evidence of human augmentation of fires. The patterns of fire activity, fire–climate relationships, and forest development indicate that traditional landuse by Anishinaabeg (Ojibwe) increased rates of local surface fire and played an important role in shaping the landscape. The decline of traditional subsistence practices by the Border Lakes Anishinaabeg coincided with a sharp decline in surface fires and a period of abundant tree establishment. In the absence of repeat surface fires, many red pine sites have shifted in composition, increased in stem density, and grown vulnerable to forest‐type conversion through future high‐severity fire. These results highlight the need for active fire reintroduction to red pine forests of the Great Lakes Region and underscore the importance of collaboration and guidance from Indigenous Knowledge Keepers in this process. A blended knowledge approach to fire restoration that directly engages with Indigenous perspectives and cultural practices can perpetuate the distinctive character of the largest remaining tracts of long‐lived pine forest in the Great Lakes Region. Carefully developed fire restoration practices would enhance the visitor use experience within one of the most frequently visited wilderness areas in the United States while re‐engaging directly with Indigenous knowledge and traditional cultural practices.
... The landscape (i.e., entire study area) was separated into three landforms according to separations caused by two rivers (Bald, Big, and Park Hills, Fig. 1). Landforms were further divided into ten stands, delineated by clusters of samples with smaller spatial extents (≤1 km 2 ), comparable to those reported as sites in other eastern U.S. fire history studies (Aldrich et al. 2010, 2014, Flatley et al. 2013, Muzika et al. 2015, Johnson and Kipfmueller ❖ www.esajournals.org 2016, Kipfmueller et al. 2017, Stambaugh et al. 2018). ...
... Similar to both Scandinavian studies (Niklasson and Granstrom 2000, Rolstad et al. 2017) and red pine fire history studies in Pennsylvania and Michigan (Drobyshev et al. 2008, Brose et al. 2013, Muzika et al. 2015. Relationship between mean fire interval (MFI) and spatial extent of observation. ...
... The percentage of trees scarred for a given fire year has been shown to depict fire extent (Farris et al. 2010) and proposed as a scale for fire severity (Lombardo et al. 2009, Muzika et al. 2015. In this study, we refined this metric to consider only trees which were recorded within the fire-extent area, therefore removing trees and areas not relevant to that fire ❖ www.esajournals.org ...
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Long‐term, ecosystem‐specific fire regime information improves natural community restoration and management by providing a basis for scientifically reasoned fire management prescriptions. Historical fire regimes can be reconstructed to sub‐annual resolution using fire‐scarred trees, and while such reconstructions have become increasingly prevalent across the eastern USA, little information regarding how they vary at landscape scale is available. Most studies report fire regime characteristics (i.e., frequency, seasonality) at site‐composite levels, commonly at ≤1 km2 spatial resolution. In this study, we analyzed the historical spatial variation of fire regime characteristics over the past four centuries (1620 CE to present) in a red pine/oak landscape (30.75 km2) in north‐central Pennsylvania, USA. Fire event data were reconstructed based on fire scars and locations of 192 living and dead red pines. The spatial and temporal distributions of fire scars revealed a historical fire regime dominated by frequent, dormant season fires most often detected at relatively small spatial extents and by relatively few trees. There was, however, evidence of less frequent, relatively large fires that scarred high percentages of trees. These fire regime characteristics likely resulted in a spatially and temporally transient patchwork of varying vegetation age and structures resulting in a heterogeneous landscape. At the landscape scale, fire frequency changed with human cultures, while fire spatial extent and scarring patterns appeared to be modulated by drought conditions. Results from this study show historical precedence for landscape‐scale burning across a broad range of drought conditions and spatial extents, which should be considered when designing fire‐management and ecosystem restoration objectives.
... Extreme climate and weather conditions can limit or enhance both lightning and anthropogenic ignition rates. Further, within relatively small spatial extents, both ignition types may be dominant (Muzika et al. 2015). For these reasons and others, studies have focused on identifying associations, signatures, and signals to distinguish climate and human forcing of fire regimes. ...
... For these reasons and others, studies have focused on identifying associations, signatures, and signals to distinguish climate and human forcing of fire regimes. Examples of these include the following: frequency of modern era fire causes, spatial patterns of historical fires (Niklasson andGranstrom 2000, Flatley et al. 2011), variance characteristics in fire activity at decadal to century scales (Kitzberger et al. 2007, Bowman et al. 2009), fire seasonality comparisons from historical to modern eras (Evett et al. 2007), strength and changes in climate-fire associations (Muzika et al. 2015), and associations among human occupations and vegetation types (Black et al. 2006). ...
... A wave of fire progressively moved across the region and represents changes in fire frequency from relatively infrequent fires during periods of Native American depopulation (MFIs from 5.6 to 57 yr), increasing fire frequency associated with EAS and industrialization (MFIs from 3.2 to 7.3 yr), and declining to no fire activity leading to, and including, the current era of fire suppression (MFIs from 25 to 52+ yr). Previous fire scar and charcoal studies from across the eastern USA have reached the same conclusion, including evidence for a waveform pattern in fire frequency (Guyette et al. 2002, 2006, Muzika et al. 2015, Lafon et al. 2017. Although many eastern U.S. regions lack fire history records, to date, this waveform pattern has been less consistently found in the Appalachians; some studies report fire frequency unaffected by changes in human populations (Shumway et al. 2001, Aldrich et al. 2010, Flatley et al. 2013. ...
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Article
Increasingly detailed records of long‐term fire regime characteristics are needed to test ecological concepts and inform natural resource management and policymaking. We reconstructed and analyzed twelve 350+ yr‐long fire scar records developed from 2612 tree‐ring dated fire scars on 432 living and dead pine (Pinus pungens, Pinus rigida, Pinus resinosa, Pinus echinata) trees from across central Pennsylvania. We used multiple spatial and time series analysis methods to quantify fire regime characteristics (frequency, seasonality, percentages of trees scarred, extent) and fire–climate–human associations. Prior to the 20th‐century fire suppression, fire regimes at the majority of sites consisted of frequent, low‐to‐moderate severity, dormant season fires. Fires were often regionally synchronous when preceded by significantly dry years. Using documentary archives, we provide the first description of a “wave of fire”—an anthropogenic signal in fire frequency that progressively moved across the region. This “wave of fire” reflects a changing progression of anthropogenic fire regimes from Native American occupation and depopulation, to Euro‐American settlement, to industrialization and declining fire use up to the 20th century era of fire suppression. The wave of fire provides a new perspective on historical and modern fire regime dynamics and identifies socio‐ecological impacts since North American colonization. Because the anthropogenic wave of fire exists at sites across North America, we emphasize the need for a broader determination of its geographic prevalence and variability as such determinations could influence historical ecology interpretations and perspectives on past and future roles of humans in managing ecosystems with fire.
... An AnthroFire Index (AFI) has been developed to detect changes in the fire regime that reflect human ignition influence [28,29]. The AFI was calculated using reconstructed drought [27] and fire occurrence data. ...
... We developed a coarse-scale annual Fire Extent Index (FEI) to examine the relationship between drought and the potential sites burned and trees scarred [11,28]. The FEI was not developed for estimating the area burned but rather to estimate a relative spatial extent variable that could be related to PDSI. ...
... Many of the years calculated as having large FEI values in northern Wisconsin were also extensive fire years in more northerly and eastern regions. For example, in 1780 all sites in Wisconsin burned and three of seven sites (43 percent) were burned in the Huron Mountains of Michigan (175 km northeast) [28]. Similarly, in 1664 fires also coincided in the Huron Mountains and in Wisconsin. ...
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Article
Throughout much of eastern North America, quantitative records of historical fire regimes and interactions with humans are absent. Annual resolution fire scar histories provide data on fire frequency, extent, and severity, but also can be used to understand fire-climate-human interactions. This study used tree-ring dated fire scars from red pines (Pinus resinosa) at four sites in the Northern Sands Ecological Landscapes of Wisconsin to quantify the interactions among fire occurrence and seasonality, drought, and humans. New methods for assessing the influence of human ignitions on fire regimes were developed. A temporal and spatial index of wildland fire was significantly correlated (r = 0.48) with drought indices (Palmer Drought Severity Index, PDSI). Fire intervals varied through time with human activities that included early French Jesuit missions, European trade (fur), diseases, war, and land use. Comparisons of historical fire records suggest that annual climate in this region has a broad influence on the occurrence of fire years in the Great Lakes region.
... Fire scars on red pine or white pine often indicate mean FRIs ranging from 6-60 years in the 15th to late 19th centuries. This has been demonstrated in many sites across the region, from the Menominee Reservation of northern Wisconsin to the Green Mountains of Vermont (Engstrom and Mann 1991;Mann et al. 1994;Guyette and Dey 1995;Sands and Abrams 2011;Muzika et al. 2015;Abadir et al. 2019). ...
... Thus, it is critical to consider the human context when interpreting local fire ecology; in many cases burning was done for a variety of purposes and not necessarily to promote the cooccurring wildlife species. Throughout the GL-NEF, the mid-1700s marks an important time of transition from lower to higher frequency fires (Muzika et al. 2015;Stambaugh et al. 2018;Marschall et al. 2019;Larson et al. 2020). Often fire frequency increased through the mid-to late-1800s as human activities associated with settlement and logging increased ignitions. ...
Chapter
The Great Lakes-Northeastern forest region from Minnesota to New England has varied climates and site conditions that allow diverse fire regimes. In the coldest, boreal forests, infrequent high-severity fires maintain jack pine forests or birch-aspen-spruce-fir-forests. Moderately frequent, mixed-severity fires maintain red/white pine forests on sites with shallow or sandy soils. Fires are least frequent in northern hardwood forests, but can interact with wind-thrown timber to cause intense fires and patches of birch-aspen forests within a late successional matrix. On sandy northern hardwood sites, moderate-severity fires regulate the balance between pines and oaks, and late successional species. Burning by Native Americans created areas of multi-aged pine and oak forests, and savannas, regardless of the fire regime that would have occurred given the climate and soil conditions. These historical fire regimes have been altered by fire exclusion, so that late successional species have gained dominance in most forest types. However, warming climate and use of prescribed fire may reverse this trend.
... In the laboratory, we used a dissecting microscope to crossdate tree samples using standard dendrochronological techniques, assigned exact calendar dates to all fire scars, and determined season of fire when possible (Grissino Mayer andSwetnam 2000, Speer 2010) based on fire-scar position. We followed the convention of assigning ring-boundary scars (dormant season position) to the subsequent year containing the earlywood immediately following fire scars (Muzika et al. 2015, Johnson and Kipfmueller 2016, Meunier et al. 2019b and assessed the sensitivity of our major conclusions to this convention by repeating analyses with ring-boundary scars assigned to the previous year (Supplementary Material). We correlated ring width patterns to master chronologies for the region (Wendland and Swain Henselman 2002 using Cybis CDendro version 9.3.1 to assist with crossdating (Larsson 2018). ...
... Similarly, there is little research in the Upper Great Lakes region on phenology of wood development hence no information on when latewood or earlywood formation begins and ends in red pine. However, our dating is consistent with other studies in this region including large fire years (Heinselman 1973, Drobyshev et al. 2008, Muzika et al. 2015, Guyette et al. 2016, Johnson and Kipfmueller 2016, Kipfmueller et al. 2017, Meunier et al. 2019a, Meunier et al. 2019b, Meunier and Shea 2020, and our major conclusions were the same regardless of whether dormant fire scars (143 of 413 total fire scars) were assigned to the previous or subsequent year (Supplemental Material). ...
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Article
Peatlands contain one-third to one-half of global soil carbon, and disturbances, specifically fire, directly influence these carbon stocks. Despite this, historical variability of peatland fire regimes is largely unknown. This gap in knowledge partly stems from reconstructions of peatland fire regimes with methods limited to evaluating infrequent, severe fire events and not capturing frequent, low-severity events. Furthermore, variability in fire regimes is likely higher in heterogenous landscapes like the hemiboreal subzone, the transition between boreal and temperate biomes, where peatlands are embedded in landscapes including forests with high proportions of fire-dependent species, such as red pine (Pinus resinosa), that are well adapted to frequent low-severity fires. Here, we sought to evaluate the role of low- and moderate-severity fires within hemiboreal peatlands in central North America to better understand historical variability in fire regimes. We reconstructed historical fire regimes using fine-scale (temporal and spatial) dendrochronology methods to estimate frequency of low- and moderate-severity fires, identify synchronous fire events among forested uplands within and surrounding individual peatlands as well as among sites, and assess fire-climate relationships. We collected 220 cross-sections or partial-tree sections within three poor fen peatlands across the Great Lakes Region. Using standard dendrochronological techniques, we crossdated 129 samples, assigning dates to 414 fire scars (128 unique fire years) comprising a 500-year tree-ring record (1520–2019). Prior to the mid-1900s, fire events were frequent and widespread within peatlands we evaluated, with mean fire return intervals (MFRI) ranging from 7 to 31 years. Fire events were also synchronous among forested uplands within and surrounding peatlands. Fires predominantly occurred in the dormant and latewood (growing season) positions and during regionally dry conditions corresponding to mild and moderate drought (Palmer Drought Severity Index ≥ −2.99) but interestingly not during regionally severe drought (Palmer Drought Severity Index ≤ −3.00). While large-scale, high-severity fires are important to the ecology of peatlands and to changing climate-fire interactions, our results suggest that widespread low- to moderate-severity fires were historically frequent in hemiboreal peatlands and likely central to their development and maintenance. Evaluating whether peatlands will continue to be carbon sinks or become carbon sources due to climate change requires an understanding of the inherent variability in fire regimes, especially in hemiboreal systems.
... Similar to the relative tree height hypothesis, the significant elevation difference (i.e., hundreds of metres) between lowlands and ridge tops could lead to higher strike probability for ridge-top trees (Johnson 1966;Minko 1975;Muzika et al. 2015). Again, evidence supporting this hypothesis generally is lacking. ...
... Following the major hypotheses concerning lightning interactions with trees, we expected that the frequency of lightning damage would be conspicuously higher on emergent trees and trees on exposed ridge tops (e.g., Plummer 1912;Muzika et al. 2015). However, only our prediction for the role of emergent status was supported. ...
Article
Lightning strikes millions of trees worldwide each year, yet structured lightning damage surveys are relatively rare. Estimates drawn from the literature suggest that lightning directly or indirectly kills up to 4% of large canopy trees in a stand annually. Lightning is a major cause of death for pines in southeastern US forests and for large cacti in some deserts, but its landscape-level effects exclusive of fire at higher latitudes are poorly known. We quantified damage to trees from lightning and other sources in hemlock-hardwood forests of the Huron Mountain Region of Michigan, USA. This region receives ca. 100 cloud-to-ground lightning flashes per year, with most occurring May-August. We recorded abiotic and biotic damage on 309 trees distributed among 9 transects, each > 2 km long. None of the transect trees had lightning scars, and we observed only 14 clear cases of lightning damage among thousands of trees examined during associated meander surveys (each ca. 0.5 ha). This damage was more commonly associated with emergent stature (50% of struck trees) and higher rates of biotic damage (50%) than we observed in the 309 transect trees (22% emergent status and 16% incidence of biotic damage). Nearly all (93%) of the lightning damaged trees were conifers, suggesting that either susceptibility to, or response to lightning strikes has a phylogenetic basis. These preliminary results provide a foundation for comparative studies in other forests. Accurate quantification of lightning-induced tree mortality will improve forest turnover models and facilitate predictions of future forest structure under conditions of increased lightning frequency.
... These fires were primarily lower severity, much of which burned pine forests to the north of the high severity October 8 Peshtigo Fire (e.g., northern Oconto and Marinette Counties), where presumably slash would have been present (Fig. 2b). These low severity fires of 1871 were detected across study sites in Wisconsin (NWS, CS, NES), the Menominee Indian Reservation to the northeast (Sands and Abrams, 2011), and in the Huron Mountains in the Upper Peninsula of Michigan (Muzika et al. 2015). (Cook et al. 2007) for years prior and subsequent to fire event years (year 0) for a notable historical accounts of settlement era fires (i.e., Table 4) and b ≥ 15% average rate of scarring (minimum 10 recording trees) across all ecological landscapes. ...
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Article
Background The Lake States experienced unprecedented land use changes during Euro-American settlement including large, destructive fires. Forest changes were radical in this region and largely attributed to anomalous settlement era fires in slash (cumulation of tops and branches) following cutover logging. In this study, I place settlement era fires in a historical context by examining fire scar data in comparison to historical accounts and investigate fire-vegetation-climate relationships within a 400-year context. Results Settlement era fires (1851–1947) were less frequent than pre-settlement fires (1548–1850) with little evidence that slash impacted fire frequency or occurrence at site or ecoregion scales. Only one out of 25 sites had more frequent settlement era fires, and that site was a pine forest that had never been harvested. Settlement era fires were similar across disparate ecoregions and forest types including areas with very different land use history. Settlement fires tended to burn during significantly dry periods, the same conditions driving large fires for the past 400 years. The burned area in the October 8, 1871, Peshtigo Fire was comprised of mesic forests where fuels were always abundant and high-severity fires would be expected under the drought conditions in 1871. Furthermore, slash would not have been a major contributor to fire behavior or effects in the Peshtigo Fire when logging was still limited to relatively accessible pine forests. Conclusions Historical written accounts of fires and settlement era survey records provide a reference point for landscape changes but lack temporal depth to understand forest dynamics. Tree-ring analyses provide a longer (ca. 400 year) context and more mechanistic understanding of landscape dynamics. While settlement land use changes of Lake States forests were pervasive, fires were not the ultimate degrading factor, but rather likely one of the few natural processes still at work.
... were detected across study sites in Wisconsin (NWS, CS, NES), the Menominee Indian Reservation to the northeast (Sand and Abrams 2011), and in the Huron Mountains in the Upper Peninsula of Michigan (Muzika et al. 2015). Schulte and Mladenoff (2005) in their analysis of GLO data found that stand-replacing res were never recorded by surveyors within the ecological landscapes associated with the October 8, 1871 Peshtigo Fire ( Fig. 2a). ...
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Background The Lake States experienced unprecedented land use changes during Euro-American settlement (settlement) including large, destructive fires. Forest changes were radical in this region and largely attributed to anomalous settlement era fires in slash (cumulation of tops and branches) following cutover logging. In this study I place settlement era fires in a historical context by examining fire scar data in comparison to historical accounts and investigate fire-vegetation-climate relationships within a 400-year context.ResultsSettlement era fires (1851–1947) were less frequent than historical fires (1548–1850) with little evidence that slash impacted fire frequency or occurrence at site or ecoregion scales. Only one out of 25 sites had more frequent settlement era fires and that site was a pine forest that had never been harvested. Settlement era fires were similar across disparate ecoregions and forest types including in areas with very different land use history. Settlement fires tended to burn during significantly dry periods, the same conditions driving large fires for the past 400 years. The burned area in the October 8, 1871 Peshtigo Fire was comprised of mesic forests where fuels were always abundant and high-severity fires would be expected given the conditions in 1871. Furthermore, slash would not have been a major contributor to fire behavior or effects in the Peshtigo Fire.ConclusionsHistorical records, like written accounts of fires and settlement era survey records, provide a reference point for landscape changes but lack temporal depth to understand forest dynamics or provide a mechanistic understanding of changes. While settlement land use changes of Lake States forests were pervasive, fires were not the ultimate degrading factor, but rather likely one of the few natural processes still at work.
... Thus far, the geography of this fire hiatus appears to cover the Cumberland Plateau and lower Ohio River Valley. Shorter hiatuses occurred in the early 1700s in the Great Lakes region (Muzika et al. 2015;Guyette et al. 2016). ...
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Article
Background Vegetation of the Cumberland Plateau (USA) has undergone dramatic transitions since the last glaciation and particularly since the onset of widespread logging and twentieth century fire exclusion. Shortleaf pine ( Pinus echinata Mill.), one of the most fire-dependent conifers in the US, occurs throughout the Cumberland Plateau, but its abundance has declined dramatically since Euro-American settlement and continues to decline. To better understand the historical ecology of fire within the natural range of shortleaf pine, we reconstructed fire regimes at three new sites throughout the central and southern Cumberland Plateau region based on fire scars on shortleaf pine trees. Results Fire event chronologies extended back to the seventeenth century and revealed historical fire regimes that were frequent and dominated by dormant-season and low-severity events. Fires occurred on average every 4.4 to 5.3 years at the study sites before widespread Euro-American settlement, and were more frequent (2.3 to 3.8 years) following settlement. Cumberland Plateau fires may be linked to adjacent ecoregions such as the Eastern Highland Rim to the west. Among all sites, we found that long-term trends in fire activity were similar and fit into a regional waveform pattern of fire activity likely driven by humans ( i.e., Native American depopulation, European settlement, and twentieth century fire exclusion). Conclusions The decline in shortleaf pine and other fire-dependent ecosystems across the Cumberland Plateau is due to multiple interacting factors and, based on these data, frequent fire should be considered a historically important ecological driver of these systems.
... Tree communities are characteristic of the boreal-deciduous forest ecotone, with white spruce, white pine (Pinus strobus), balsam fir (Abies balsamea), eastern hemlock (Tsuga canadensis), striped maple (Acer pensylvanicum), red maple (Acer rubrum), sugar maple (Acer saccharum), northern white cedar (Thuja occidentalis), trembling aspen (Populus tremuloides), and paper birch (Betula papyrifera). This region of the Huron Mountains includes a portion of the old-growth forest where fire has been a key natural disturbance (Simpson et al. 1990;Muzika et al. 2015). Bedrock of the study region is Pre-Cambrian granite, gneiss, and sandstones (Dorr and Eschmann 1970). ...
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Article
The resource budget model for mast seeding hypothesizes that soil nutrients proximately influence reproduction. Plants in high soil nutrient (particularly N) areas are predicted to have lower reproductive variability over time and higher mean reproduction. While often examined theoretically, there are relatively few empirical tests of this hypothesis. We quantified cone production of 110 individual white spruce (Picea glauca) trees over seven years and quantified plant-available soil macronutrients (N, Ca, K, Mg, P, S) in natural forest conditions across three years with different cone crop conditions. Each of these plant-available soil nutrients were correlated across years (rs = 0.55-0.89; all > 0.81 for total-N); spatially, total-N availability varied 366-fold across trees. Plant-available soil nutrients did not influence variability or mean annual reproduction, contrary to nutrient perturbation experiments. We examined within-year nutrient and cone-production relationships, and observed significant positive relationships between reproduction and plant-available soil nutrients only in a low-reproduction year preceding a mast event. Both during a mast event and the following year, when overall cone production was very high or very low, there were no relationships. Both external drivers (e.g., weather) and internal resource budgets likely influence soil nutrient-reproduction relationships. These results suggest that plant-available soil nutrients may not be a large factor influencing mast-seeding patterns among individuals in this species.
... Although our work addresses a very specific area, the lessons learned here apply to other landscapes as well. The stories learned from old-growth forests in the BWCAW give greater meaning to the growing network of fire history sites in the Great Lakes Region that includes both published results (Drobyshev et al. 2008;Muzika et al. 2015;Guyette et al. 2016;Kipfmueller et al. 2017;Larson and Green 2017) and as-yet unpublished data sets. Sites with evidence of historically frequent low-severity fire likely represent interwoven human and landscape interactions that shaped the diversity of forest conditions across the region. ...
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Article
The creation and modification of landscape patterns through interactions among people and the environment is a defining focus in the discipline of geography. Here, we contribute to that tradition by placing 500 years of red pine (Pinus resinosa) tree-ring data in the context of archaeological, ethnographic, and paleoecological records to describe patterns of Anishinaabeg land use and fire occurrence in the Boundary Waters Canoe Area Wilderness (BWCAW) of northern Minnesota. Multiple lines of evidence suggest that stories of people, fire, and red pine are tightly interwoven in the BWCAW. We suggest that preferential use and maintenance of specific sites with fire by Border Lakes Anishinaabeg before 1900 led to the xerification of forest communities that produced conditions more desirable to people in a rugged near-boreal landscape. Today, after a century of fire absence, these sites represent fading ecological legacies that are still sought by wilderness users for their recreational values and perceived wilderness character. Ironically, protections granted by the 1964 Wilderness Act are resulting in a decline of the red pine forests once used to help justify establishment of the BWCAW. An opportunity exists for wilderness managers, users, and advocacy groups to reassess the need for active management and the strategic return of frequent fire to the aging pine forests of the BWCAW. Engaging descendent communities of the Border Lakes Anishinaabeg in these efforts could help move beyond conventional approaches to wilderness management and restore the reciprocal relationship between people, fire, and red pine in the BWCAW and beyond.
... In much of the upper Midwest, it is likely that both lightning-caused fire and burning by Native Americans played a large role in forest processes during the pre-Euro-American period [28]. In particular, strong evidence exists for humanaugmented fire frequency in certain coniferous forests found in the northern parts of the region [29,30]. The understanding of human influences on fire regimes in the more southern vegetation communities of the region remain relatively poorly understood due to a lack of relevant historic or paleoecological data [28,31]. ...
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Article
1) Background: Frequent fire, climate variability, and human activities collectively influence savanna ecosystems. The relative role of these three factors likely varies on interannual, decadal, and centennial timescales. Here, we tested if Euro-American activities uncoupled drought and fire frequencies relative to previous centuries in a temperate savanna site. (2) Methods: We combined records of fire frequency from tree ring fire scars and sediment charcoal abundance, and a record of fuel type based on charcoal particle morphometry to reconstruct centennial scale shifts in fire frequency and fuel sources in a savanna ecosystem. We also tested the climate influence on fire occurrence with an independently derived tree-ring reconstruction of drought. We contextualized these data with historical records of human activity. (3) Results: Tree fire scars revealed eight fire events from 1822-1924 CE, followed by localized suppression. Charcoal signals highlight 13 fire episodes from 1696-2001. Fire-climate coupling was not clearly evident both before and after Euro American settlement The dominant fuel source shifted from herbaceous to woody fuel during the early-mid 20th century. (4) Conclusions: Euro-American settlement and landscape fragmentation disrupted the pre-settlement fire regime (fire frequency and fuel sources). Our results highlight the potential for improved insight by synthesizing interpretation of multiple paleofire proxies, especially in fire regimes with mixed fuel sources.
... A fire extent index (FEI; Guyette et al. 2002;Muzika et al. 2015) was calculated to evaluate regional fire extent across all sites. FEI provides an additional metric for understanding trends in fire extent by combining both regional and site data. ...
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Article
Along the prairie–forest border in the south-central USA exists one of the most extensive areas of uncut forest in the nation (>323 750 hectares), providing unique potential for developing multi-century records of environmental changes through dendrochronological analyses. Twentieth century changes in vegetation, increased prescribed fire management, and recent years of elevated wildfire activity have increased interest in understanding the region’s long-term fire regime characteristics. To address this need, we analyzed and compared fire intervals, seasonality, severity, and extent based on fire-scar history datasets from three new and ten existing study sites. At the study sites, mean fire intervals ranged from 3 to 10 years prior to Euro-American settlement and generally became more frequent after. The majority of fires occurred in the dormant season and resulted in low percentages of trees scarred. Coinciding with Euro-American settlement (EAS), fire frequencies appear to have varied by geography. At the regional scale, fire regimes have trended towards decreased fire severity and slightly decreased fire intervals over the past 300 years. Further, fires appear to have increased in extent from circa 1770 to the mid to late 1800s, after which it began to decline, circa 1920. Although frequent, descriptions of fire regimes since the eighteenth century should be characterized as time-dependent and spatially variable, likely depending on local socio-ecological influences. Similar influences may explain fire frequency increases following EAS, while fire severity trended lower.
... Moreover, some encourage fire though the retention of low dead branches and production of volatile foliage (jack, pitch, and TMP). Historical fire regimes associated with these species ranged from frequent to infrequent, from surface to stand-replacing events (Heinselman, 1981;Wright and Bailey, 1982), from localized to regional in extent (Drobyshev, 2008;Stambaugh et al., 2018), and originated from both anthropogenic and lightning ignitions (Welch and Waldrop, 2001;Muzika et al., 2015). Historical observations by Chapman (1952) and Goodlett (1954) are corroborated by forest inventories that show the decrease of fire-dependent pine populations since EuroAmerican settlement due to the combined effects of past land-use practices and fire regime alterations (Ahlgren, 1974;Nowacki and Abrams, 1992;Oswalt, 2012). ...
... Fire regimes that have fire years primarily in drought conditions are hypothesized to be more climate controlled, while fire regimes that have fire years in wet years are more anthropogenic controlled (Muzika et al., 2015). From this framework and based on our results, it would appear that the fire regime during the last three centuries was strongly controlled by human influences (e.g., ignitions). ...
Article
In 2011, the most destructive wildfire in Texas history (Bastrop County Complex Fire, BCCF) burned 34,000 acres including most of Bastrop State Park. We used dendrochronological analysis of vegetation paired with documentary information to reconstruct the historical fire regime, changes in forest composition, and possible human influences leading up to this seemingly unique event. In addition, demographics of fire-killed and immediate post-fire regenerating trees were determined through stem aging and a regeneration census. Historical fire frequency was lower during the pre-EuroAmerican Settlement period (pre-1830) compared to later time periods before the 1920s. Since the 1920s, fire occurrence has significantly decreased. Historical fire characteristics appeared to change with local and regional cultural and land use changes. Within the BCCF area were extensive areas of very old (up to 359 yrs old) open-grown post oaks (Quercus stellata) that had been overtopped by 60 year old loblolly pines (Pinus taeda). Historically, oak woodlands likely persisted in the study area due to recurring fire and, though less well documented, by grazing and selective logging for loblolly pines. This region is an ecotone between the oak woodlands and Lost Pines and our data show transitions between the two types through time. It is unclear how this vegetation interaction may have affected the destructive BCCF, but its severity and effects were unprecedented during at least the last three centuries. Little to no loblolly pine natural regeneration existed despite being dominant in the pre-fire forest overstory. Based on stump sprout abundance, blackjack oak (Q. marilandica) will likely be the dominant tree species in the next few decades.
... Many fire history studies in the eastern U.S. have identified human population, settlement patterns, and commerce activities to be closely associated with changes in fire frequency [16,35,[71][72][73][74][75][76]. Compared to human ignitions, lightning ignitions are rare in the northeastern U.S. Most lightning events are accompanied by rain and high levels of humidity, further implicating humans as an important fire ignition source for maintaining frequent fire regimes [77]. ...
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Many fire-adapted ecosystems in the northeastern U.S. are converting to fire-intolerant vegetation communities due to fire suppression in the 20th century. Prescribed fire and other vegetation management activities that increase resilience and resistance to global changes are increasingly being implemented, particularly on public lands. For many fire-dependent communities, there is little quantitative data describing historical fire regime attributes such as frequency, severity, and seasonality, or how these varied through time. Where available, fire-scarred live and remnant trees, including stumps and snags, offer valuable insights into historical fire regimes through tree-ring and fire-scar analyses. In this study, we dated fire scars from 66 trees at two sites in the Ridge and Valley Province of the Appalachian Mountains in central Pennsylvania, and described fire frequency, severity, and seasonality from the mid-17th century to 2013. Fires were historically frequent, of low to moderate severity, occurred mostly during the dormant season, and were influenced by aspect and topography. The current extended fire-free interval is unprecedented in the previous 250–300 years at both sites.
... Understanding the frequency of historic fires has an important role in explaining changes to contemporary forests. The result is a rich history of studies of fire history across the eastern United States (Shumway et al. 2001;Guyette et al. 2006;McEwan et al. 2007; King and Muzika 2014;Muzika et al. 2015; among others). One of the common patterns found in these studies is that surface fires were often frequent events prior to Euro-American settlement of the area and that fire remained frequent during early Euro-American settlement prior to fire suppression efforts in the early and mid-20 th century. ...
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Evidence indicates that the structure of Oklahoma Cross Timbers forests are in transition due to changing climate, land-use patterns, and fire suppression efforts. However, only a handful of studies have addressed the history of fire across the Oklahoma Cross Timbers landscape. This research adds to the body of literature by studying the contemporary forest structure and fire history at Lake Arcadia in Oklahoma County, Oklahoma. Results demonstrate that post oak (Quercus stellata Wangenh.) and blackjack oak (Q. marilandica Münchh.), two common species in Oklahoma Cross Timbers, dominate the forest. However, several mesophytic tree species are found in the overstory as well as the sapling layer of the forest. A total of 25 fire events (mean fire interval = 4.14 years) were documented during the 20 th century using fire-scar analysis of Q. stellata trees and remnant wood (stumps, snags, recently dead trees). High fire frequencies in the early to mid-20 th century corresponded to the recruitment of Q. stellata and Q. marilandica. Wet conditions (PDSI > 0) during the late 20 th century and no fires after 1985 corresponded to the recruitment of non-oak, mesophytic species at the study site. The results of this study suggest that changes in fire frequency and moisture availability are contributing to changes in tree density and species composition at the study site.
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Preprint
Background: Past burning by Native Americans can be analyzed from tree-ring fire-scar records (FSRs) via dendrochronological methods. However, the degree to which FSRs have adequately captured the varied locations where Native Americans burned landscapes, at both local and regional scales, remains largely unknown. Also unassessed is whether individual studies utilizing FSRs provide adequate spatial contextualization of FSR sites alongside Native American geography (e.g. settlements, travel corridors) to facilitate understanding of spatial relationships between fire and settlement. This paper assesses (1) the representativeness of FSR sites with respect to Native American settlement (circa 1760-1820) in eastern North America, (2) whether FSR-based studies provide adequate contextualization of their study sites with respect to settlement, and (3) spatial relationships between settlement and fire frequency gleaned from available FSRs. Results: Many locations with past Native American settlement are not represented by FSRs, and few individual studies provide locations of settlement to compare with FSR site locations. Available FSRs suggest that fire was most frequent at intermediate distances (i.e. 100-150 km) from villages, and least frequent near villages. This trend may be due to the clearing of nearby trees or deliberate burns away from villages for various purposes, but within a reasonable distance for access. Conclusions: Future FSR development should target locations near former settlement to increase spatial balance, and researchers should provide better description (textual or cartographic) of Native American geography to characterize how proximate and in what environments cultural burning occurred. Such efforts will refine understanding of spatial locations and extent of burning. This study underscores the need to develop and share FSRs in locations where past cultural burning occurred before such samples disappear.
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We used dendrochronological methods and remnant fire-scarred red pines (Pinus resinosa Ait.) to reconstruct historical fire regime characteristics and relate these findings to past climate, human land use changes, and vegetation for a landscape in northern Minnesota, USA. A total of 314 fire scars were dated, representing 56 unique fire events from 1565 to 1967. In the period prior to fire exclusion (1535–1935), fire intervals ranged from 1 to 40 years across the landscape and the mean fire interval was 6.6 years. The majority of fire scars (74%) occurred in the dormant season. Climate analyses showed that conditions two years before fire events were significantly wet and, in the year of fires, conditions were significantly dry. Overall, our study reveals complex interactions among climate, humans, and physiographic factors and how these have varied through time. For fire and forest management of red pine specifically, the results point to the use of silvicultural systems with high levels of retention, including non-stand replacing disturbances.
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Populations of many tree species exhibit synchronous and highly temporally variable seed crops across years. This is called mast seeding, and there are two predominant hypotheses for this pattern of reproduction, pollination efficiency and seed-predator satiation. Mast seeding studies typically involve records of population-level reproduction, with less information on the characteristics of reproductive structures. Here, we use data across six years (2012-2017), spanning a range of population-level cone conditions, to characterize i) white spruce (Picea glauca) cone lengths and seeds per cone, and ii) levels of seed predation. We quantified population-level cone production and collected 1,399 cones from a total of 38 trees in the Huron Mountains, Michigan, USA. Linear mixed models showed that mean and minimum cone lengths varied significantly across years; both being longest during the greatest cone production year. Larger cones had more seeds and the slopes of the relationships as well as the intercepts varied significantly across years. Generalized linear mixed models and AIC model selection showed that cones with insect predation damage was greatest when population-level reproduction was the lowest, with a mean proportion of cones damaged 0.82 in that year. Our findings show that white spruce cone characteristics and losses to insect seed predation vary temporally, and follow expectations based on mast seeding hypotheses.
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Examining fire regime characteristics across temporal and spatial scales is critical to understanding relationships between fire and landscape physiography. In the Lake States (Wisconsin, Michigan, Minnesota) we have often relied on either broad extrapolation from local studies, and/or interpretations of coarse-scale Euro settlement era records tied to landscape-scale physiography to understand complex fire regimes. In this study, we used detailed fire frequency and origin-to-first-scar (OFS, patterns of fire-scar formation) intervals to evaluate fire characteristics in relation to physiography at local and landscape scales. We found frequent fires (mean fire return intervals, MFRI = 8 years) and widespread fire years were common among our sites. OFS intervals were also less than half as long (µ = 18.3) as intervals often deemed necessary for seedlings to survive fires (ca. 50 years). We found no differences in either MFRI or OFS intervals nor physiographic effects (topography and water features) at broad ecological landscape scales. Most variability in OFS was accounted for at a site scale with increased water features and topographical ruggedness both resulting in shorter OFS intervals (trees surviving and recording fires at a younger age). We found few differences in MFRI's among sites, which ranged from 4 to 13 years. Relationships between fire resistance and stand level physiography, which was highly variable, may have a greater role than recognized in forest successional stages and stand dynamics.
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Forest ecosystems in eastern North America have been in ux for the last several thousand years, well before Euro‐American land clearance and the 20th‐century onset of anthropogenic climate change. However, the magnitude and uncertainty of prehistoric vegetation change have been difficult to quantify because of the multiple ecological, dispersal, and sedimentary processes that govern the relationship between forest composition and fossil pollen assemblages. Here we extend STEPPS, a Bayesian hierarchical spatio‐temporal pollen‐vegetation model, to estimate changes in forest composition in the upper Midwestern United States from about 2,100 to 300 years ago. Using this approach, we find evidence for large changes in the relative abundance of some species, and significant changes in community composition. However, these changes took place against a regional background of changes that were small in magnitude or not statistically significant, suggesting complexity in the spatio‐temporal patterns of forest dynamics. The single largest change is the infilling of Tsuga canadensis in northern Wisconsin over the past 2000 years. Despite range in‐filling, the range limit of T. canadensis was largely stable, with modest expansion westward. The regional ecotone between temperate hardwood forests and northern mixed hardwood/conifer forests shifted southwestward by 15‐20 km in Minnesota and northwestern Wisconsin. Fraxinus, Ulmus, and other mesic hardwoods expanded in the Big Woods region of southern Minnesota. The increasing density of paleoecological data networks and advances in statistical modeling approaches now enables the confident detection of subtle but significant changes in forest composition over the last 2,000 years. This article is protected by copyright. All rights reserved.
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We developed a fire history for Voyageurs National Park (VNP), MN, USA based on 129 fire-scarred cross sections collected at 39 disjunct locations to develop a baseline understanding of the history of fire in the region. We dated 443 scars representing 126 unique fire years with the earliest fire recorded in 1665 and the most recent in 1972. The Weibull Median Fire Interval from individual fire intervals at the 39 sites is about 18 years and two years for the study area as a whole. Site-scale fire intervals were relatively short, with about 75% of the intervals between fires less than 30 years and more than half of the intervals shorter than 20 years. Approximately 61% of the 126 unique fire years were recorded at only 1 site and about 20% of fires were recorded at 2 or more sites. The median interval between fires that were synchronous at 3 or more sites is 7 years, with the earliest synchronous fire occurring in 1718 and the last in 1936. Fires occurring at more than three sites coincided with summers that are significantly drier than average during the fire year. In VNP, several lines of evidence are suggestive of the potential role of people in augmenting the fire regime above that which would have occurred due to lightning alone. The patterns of fire activity in VNP highlight the same issues that have been noted elsewhere, namely that fires have been prominent in the past in shaping the character of Upper Great Lakes forests and that fire activity has been much reduced since the 20th century. The reduction of fire activity observed after the early 20th century could be as much related to the reduction of human ignition and the removal of people from the landscape as it is to active suppression. This research suggests that the appropriate use of planned fire should be employed as an important management tool, likely through the intentional ignition of fires rather than a reliance on lightning starts alone. This research represents another step in better understanding the processes that have shaped the landscape of Voyageurs National Park, while continuing a dialogue around the future of an ecologically, economically, and culturally significant subset of the Border Lakes landscape.
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The effects of lightning on trees range from catastrophic death to the absence of observable damage. Such differences may be predictable among tree species, and more generally among plant life history strategies and growth forms. We used field-collected electrical resistivity data in temperate and tropical forests to model how the distribution of power from a lightning discharge varies with tree size and identity, and with the presence of lianas. Estimated heating density (heat generated per volume of tree tissue) and maximum power (maximum rate of heating) from a standardized lightning discharge differed 300% among tree species. Tree size and morphology also were important; the heating density of a hypothetical 10 m tall Alseis blackiana was 49 times greater than for a 30 m tall conspecific, and 127 times greater than for a 30 m tall Dipteryx panamensis. Lianas may protect trees from lightning by conducting electric current; estimated heating and maximum power were reduced by 60% (±7.1%) for trees with one liana and by 87% (±4.0%) for trees with three lianas. This study provides the first quantitative mechanism describing how differences among trees can influence lightning–tree interactions, and how lianas can serve as natural lightning rods for trees.
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The effects of climate on wildland fire confronts society across a range of different ecosystems. Water and temperature affect the combustion dynamics, irrespective of whether those are associated with carbon fueled motors or ecosystems, but through different chemical, physical, and biological processes. We use an ecosystem combustion equation developed with the physical chemistry of atmospheric variables to estimate and simulate fire probability and mean fire interval (MFI). The calibration of ecosystem fire probability with basic combustion chemistry and physics offers a quantitative method to address wildland fire in addition to the well-studied forcing factors such as topography, ignition, and vegetation. We develop a graphic analysis tool for estimating climate forced fire probability with temperature and precipitation based on an empirical assessment of combustion theory and fire prediction in ecosystems. Climate-affected fire probability for any period, past or future, is estimated with given temperature and precipitation. A graphic analyses of wildland fire dynamics driven by climate supports a dialectic in hydrologic processes that affect ecosystem combustion: 1) the water needed by plants to produce carbon bonds (fuel) and 2) the inhibition of successful reactant collisions by water molecules (humidity and fuel moisture). These two postulates enable a classification scheme for ecosystems into three or more climate categories using their position relative to change points defined by precipitation in combustion dynamics equations. Three classifications of combustion dynamics in ecosystems fire probability include: 1) precipitation insensitive, 2) precipitation unstable, and 3) precipitation sensitive. All three classifications interact in different ways with variable levels of temperature.
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Fire regimes of pine savannas on barrier islands along the coast of the Gulf of Mexico are unknown. We used dendrochronological techniques to precisely date scars from 52 slash pines (Pinus elliottii Engelm.) located within a 370 ha area on Little St. George Island, Florida, USA, an undeveloped barrier island. We determined the years and seasons of fires and turpentine operations, and mapped the spatial distribution of past fires. We identified five separate periods with different fire frequencies. Fires were frequent between 1866 and 1904 (mean fire-return interval of four years). No scars were found from 1905-1923, years during which turpentine operations (1912-1918) protected trees from fires. Frequent fires were again recorded from 1924-1945, (mean fire return interval of four years). During the period from 1945-1962, turpentine operations (1949-1956) again protected trees from fires, and no fire scars were found. The most recent period, 1963 to the present, had a mean fire-return interval of nine years with active, although not entirely effective, fire suppression. Although the trees used in this study were not old enough to determine presettlement fire frequencies, the data reveal that, over the past 145 years, historic fire regimes of this barrier island slash pine savanna consisted of predominately growing-season fires, with short fire return intervals during the two periods with the least anthropogenic activity on the island. Data from this study imply that historic fire regimes of barrier island slash pine savannas, like mainland longleaf pine savannas, may have involved frequent, primarily growing-season fires.
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Technical Report
Fire scars from natural remnants of red pine (Pinus resinosa Ait.) in an oak-pine forest near Basin Lake, Algonquin Park, Ontario, were dated using dendrochronological methods. A fire scar chronology was constructed from 28 dated fire scars on 26 pine remnants found in a 1 km 2area of this forest. From pith and outside ring date distributions, 2 stand replacement fires are inferred. The composite fire scar chronology spanned 191 years from 1665 to 1856. The fire return interval between 2 stand replacement fires was about 200 years, while the return interval between fires of moderate or greater intensity was 68 years. For fires of low intensity or greater, the mean interval was 22 years. The period of the highest fire frequency was between 1733 and 1780, during which time the fire return interval for the area was 11.8 years.
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Technical Report
Fire-scarred stumps and natural snags of red pine (Pinus resinosa Ait.) on a 70-m tall bluff along Costello Creek, 2 km south of Lake Opeongo, were dated using dendrochronological methods. A fire scar chronology was constructed from 18 of the red pine samples that contained 34 dated fire scars. The composite fire scar chronology spam_ed 358 years from 1636 to 1994. The fire-return interval was 46 years between 2 medium-intensity fires and was 27 years between fires of low intensity or greater. Fire frequency at the study site increased circa 1780 to a mean fire-free interval of 17 years (1780 to 1940). No fires were observed after 1940. Analysis of pith and outside ring data indicated that the fires were not of the stand replacement type. The steep topography and exposed rocky surfaces may have mitigated the effects of intense fires on stand survival. About 66% of the pines were scarred during the 2 medium-intensity fires. The variation in fires from 1636 to t994 is associated with the movement of people into and out of the area. Before 1780, disease epidemics killed many Natives in Ontario, and others were displaced during fur trade wars, which led to a reduction in anthropogenic fires. As a result, only 1 fire was recorded between 1636 and 1779. Beginning about 1780, Natives and later Europeans began hnmigrating into the study area, and fires began to increase in frequency. After 1940, efforts to suppress fires increased, and fire was practically eliminated in the study area.
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The role of humans in historic fire regimes has received little quantitative attention. Here, we address this inadequacy by developing a fire history in northeastern Oklahoma on lands once occupied by the Cherokee Nation. A fire event chronology was reconstructed from 324 tree-ring dated fire scars occurring on 49 shortleaf pine (Pinus echinata) remnant trees. Fire event data were examined with the objective of determining the relative roles of humans and climate over the last four centuries. Variability in the fire regime appeared to be significantly influenced by human population density, culture, and drought. The mean fire interval (MFI) within the 1.2 km2 study area was 7.5 years from 1633 to 1731 and 2.8 years from 1732 to 1840. Population density of Native American groups including Cherokee was significantly correlated (r = 0.84) with the number of fires per decade between 1680 and 1880. Coincident with the Removal of the Cherokee and other native peoples from the eastern United States and immigrations into northeast Oklahoma, the MFI decreased to 1.8 years. After 1925 fire intervals were considerably lengthened (MFI = 16 years) due to fire suppression and decreased fire use until the recent prescribed burning by The Nature Conservancy. Many of the historic fire years that were previously shown to be synchronous across Missouri and Arkansas during drought years were also fire years at this site. Overall the frequency of fires was weakly associated with drought compared to human population density.
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The study of forests dominated by red pine (Pinus resinosa Ait.), one of the few fire-resistant tree species of eastern North America, provides an opportunity to reconstruct long-term fire histories and examine the temporal dynamics of climate forcing upon forest fire regimes. We used a 300-year long spatially explicit dendrochronological reconstruction of the fire regime for Seney National Wildlife Refuge (SNWR, 38,531 ha), eastern Upper Michigan to: (1) identify fire size thresholds with strong vs. weak climate controls, (2) evaluate effect of landform type (outwash channel vs. sand ridges) in modifying climate–fire associations, and (3) check for the presence of temporal changes in the climate control of large fire events over the time period 1700–1983. We used a summer drought sensitive red pine chronology (ITRDB code can037) as a proxy of past fire-related climate variability. Results indicated that fires >60 ha in sand-ridge-dominated portions of SNWR and >100 ha in outwash channels were likely climatically driven events. Climate–fire associations varied over time with significant climate–fire linkages observed for the periods 1700–1800 (pre-EuroAmerican), 1800–1900 (EuroAmerican settlement) and 1900–1983 (modern era). Although an increase in fire activity at the turn of 20th century is commonly associated with human sources of ignitions, our results suggest that such an increase was also likely a climatically driven episode.
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A predictive equation for estimating fire frequency was developed from theories and data in physical chemistry, ecosystem ecology, and climatology. We refer to this equation as the Physical Chemistry Fire Frequency Model (PC2FM). The equation was calibrated and validated with North American fire data (170 sites) prior to widespread industrial influences (before ~1850 CE) related to land use, fire suppression, and recent climate change to minimize non-climatic effects. We derived and validated the empirically based PC2FM for the purpose of estimating mean fire intervals (MFIs) from proxies of mean maximum temperature, precipitation, their interaction, and estimated reactant concentrations. Parameterization of the model uses reaction rate equations based on the concentration and physical chemistry of fuels and climate. The model was then calibrated and validated using centuries of empirical fire history data. An application of the PC2FM regression equation is presented and used to estimate historic MFI as controlled by climate. We discuss the effects of temperature, precipitation, and their interactions on fire frequency using the PC2FM concept and results. The exclusion of topographic, vegetation, and ignition variables from the PC2FM increased error at fine spatial scales, but allowed for the prediction of complex climate effects at broader temporal and spatial scales. The PC2FM equation is used to map coarse-scale historic fire frequency and assess climate impacts on landscape-scale fire regimes.
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Historical evidence suggests that great wildfires burning in the Lake States and Canada can affect atmospheric conditions several hundred miles away ( Smith 1950; Wexler 1950). Several 'dark' or 'yellow' days, as such events are commonly called, have been recorded, often with anecdotal or direct evidence pointing to wildfires as the source ( Plummer 1912; Ludlum 1972). One such 'dark day' occurred across New England in 1780, a year in which people were technologically unable to confirm the source of such a phenomenon. Here we combine written accounts and fire scar evidence to document wildfire as the likely source of the infamous Dark Day of 1780.
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To understand the dynamics of fire in red pine (Pinus resinosa Ait.) forest ecosystems that once dominated areas of the northern Lake States, we dendrochronologically reconstructed the fire regime prior to European settlement (pre-1860), after European settlement (1860-1935), and postrefuge establishment (post-1935) for different portions (wilderness and nonwilderness) and landforms (sand ridges and outwash channels) of the Seney National Wildlife Refuge (SNWR) in eastern Upper Michigan. Using data from 50 sites, we found that the cumulative number of fires showed a slow rate of accumulation from the 1700s to 1859, a steeper pattern suggesting higher fire occurrence from 1860 to 1935, and a return to fewer fires after 1935. Prior to European settlement, the fire cycle (FC) of sand ridge landforms interspersed within a poorly drained lacustrine plain in the Seney Wilderness Area was 91-144 years. This was longer than on glacial outwash channel landforms (53 years) and on sand ridge landforms interspersed within lacustrine plains located outside of the wilderness (47 years). The FC was also shorter (30 years) during this period and has subsequently increased (149-1090 years) after SNWR establishment. Differences in fire regimes among landform types were minor relative to the temporal variation in fire regimes among the three time periods.
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Aldo Leopold's Report on Huron Mountain Club, published privately in 1938, represented a novel synthesis of emerging ideas in forestry, wildlife ecology, protected area design, and landscape-scale planning. Examination of this little-known report provides new insight into the evolution of Leopold's thinking and the development of applied conservation science. The report emerged at a time when insights from scientific ecology were beginning to alter utilitarian and preservationist approaches to conservation and resource management in North America. In his report Leopold integrated ideas from several disciplines, producing a plan that emphasized the establishment of core and buffer zones in protected areas, reduction of overabundant native species, relaxation of predator control policies, and integration of research in the management of protected areas.
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Forests characterized by mixed-severity fires occupy a broad moisture gradient between lower elevation forests typified by low-severity fires and higher elevation forests in which high-severity, stand replacing fires are the norm. Mixed-severity forest types are poorly documented and little understood but likely occupy significant areas in the western United States. By definition, mixed-severity types have high beta diversity at meso-scales, encompassing patches of both high and low severity and gradients in between. Studies of mixed-severity types reveal complex landscapes in which patch sizes follow a power law distribution with many small and few large patches. Forest types characterized by mixed severity can be classified according to the modal proportion of high to low severity patches, which increases from relatively dry to relatively mesic site conditions. Mixed-severity regimes are produced by interactions between top-down forcing by climate and bottom-up shaping by topography and the flammability of vegetation, although specific effects may vary widely across the region, especially the relation between aspect and fire severity. History is important in shaping fire behavior in mixed-severity landscapes, as patterns laid down by previous fires can play a significant role in shaping future fires. Like low-severity forests in the western United States, many dry mixed-severity types experienced significant increases in stand density during the 20th century, threatening forest health and biodiversity, however not all understory development in mixed-severity forests increases the threat of severe wild fires. In general, current landscapes have been homogenized, reducing beta diversity and increasing the probability of large fires and insect outbreaks. Further loss of old, fire tolerant trees is of particular concern, but understory diversity has been reduced as well. High stand densities on relatively dry sites increase water use and therefore susceptibility to drought and insect outbreaks, exacerbating a trend of increasing regional drying. The need to restore beta diversity while protecting habitat for closed-forest specialists such as the northern spotted owl call for landscape-level approaches to ecological restoration.
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Fire historians typically attribute the causes of temporal change in past fire regimes to climatic variation, human land use, or some combination of the two. Most long-term historical reconstructions, however, lack time and place-specific chronologies for all three variables of fire, climate, and people. To test the hypothesis that Mescalero Apache of southeastern New Mexico influenced fire regimes of the Sacramento Mountains, we reconstructed and compared chronologies of key variables for the period A.D. 1700 to the present. Fire-scarred trees were used to reconstruct fire frequencies and culturally modified (peeled) trees, and written histories were used to identify places and times of Mescalero presence. Independent precipitation reconstructions from tree rings were compared with fire and human histories. We found that Mescalero frequently visited the western escarpment of the Sacramento Mountains during the late 1700s through the late 1800s, especially the Dog Canyon area. Fire frequency was higher and seasonal timing of fires was different in sites near Dog Canyon compared to relatively distant sites. Inter-annual to decadal-scale drought might explain some temporal variability in fire and peeling activity, but these relationships were not consistent. We conclude that people increased fire occurrence during certain time periods in localized areas, but broad-scale and persistent human impacts did not occur until the end of the 19th century with the rise of livestock grazing by European settlers and fire suppression by government agencies. [Key words: Culturally modified trees, historical fire regimes, fire-climate-human interactions, Apache, New Mexico.]
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Mean fire interval for the study area was c2 yr; mean fire interval for the individual Pinus ponderosa specimen was 4 yr for the 178-year period, 1722-1900. -from Authors
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Anticipating future forest-fire regimes under changing climate requires that scientists and natural resource managers understand the factors that control fire across space and time. Fire scars – proxy records of fires, formed in the growth rings of long-lived trees – provide an annually accurate window into past low-severity fire regimes. In western North America, networks of the fire-scar records spanning centuries to millennia now include hundreds to thousands of trees sampled across hundreds to many thousands of hectares. Development of these local and regional fire-scar networks has created a new data type for ecologists interested in landscape and climate regulation of ecosystem processes – which, for example, may help to explain why forest fires are widespread during certain years but not others. These data also offer crucial reference information on fire as a dynamic landscape process for use in ecosystem management, especially when managing for forest structure and resilience to climate change.
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Human interaction with fire and vegetation occurs at many levels of human population density and cultural development, from subsistence cultures to highly technological societies. The dynamics of these interactions with respect to wildland fire are often difficult to understand and identify at short temporal scales. Dendrochronological fire histories from the Missouri Ozarks, coupled with human population data, offer a quantitative means of examining historic (1680-1990) changes in the anthropogenic fire regime. A temporal analysis of fire scar dates over the last 3 centuries indicates that the percent of sites burned and fire intervals of anthropogenic fires are conditioned by the following four limiting factors: (a) anthropogenic ignition, (b) surface fuel production, (c) fuel fragmentation, and (d) cultural behavior. During an ignition-dependent stage (fewer than 0.64 humans/km2), the percent of sites burned is logarithmically related to human population (r2 = 0.67). During a fuel-limited stage, where population density exceeds a threshold of 0.64 humans/km2, the percent of sites burned is independent of population increases and is limited by fuel production. During a fuel-fragmentation stage, regional trade allows population densities to increase above 3.4 humans/km2, and the percent of sites burned becomes inversely related to population (r2 = 0.18) as decreases in fuel continuity limit the propagation of surface fires. During a culture-dependent stage, increases in the value of timber over forage greatly reduce the mean fire interval and the percent of sites burned. Examples of the dynamics of these four stages are presented from the Current River watershed of the Missouri Ozarks.
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The western United States is experiencing a severe multiyear drought that is unprecedented in some hydroclimatic records. Using gridded drought reconstructions that cover most of the western United States over the past 1200 years, we show that this drought pales in comparison to an earlier period of elevated aridity and epic drought in AD 900 to 1300, an interval broadly consistent with the Medieval Warm Period. If elevated aridity in the western United States is a natural response to climate warming, then any trend toward warmer temperatures in the future could lead to a serious long-term increase in aridity over western North America.
Article
A recent fire history from coastal pine forests in the northern Great Lakes (Loope and Anderton, 1998), based on fire-scarred Pinus resinosa trees and logging-era stumps, records that light ground fires occurred every five to 20 years in most cases, with fires beginning as early as the 1700s but ending abruptly almost everywhere in the region between 1910 and 1925. Because of the small size and isolated geographic setting of the forests, natural causes of ignition, such as lightning strikes and fires spreading from other locations, are improbable explanations for the close fire intervals. Historic and ethnographic sources suggest the forests were used as Vaccinium sp. collecting localities by Native Americans. The fertility of thse localities was likely maintained using periodic light burning, which was halted due to historic clear-cut logging and increasing white settlement and related fire-suppression activities.
Article
To recover direct evidence of surface fires before European settlement, we sectioned fire-scarred logging-era stumps and trees in 39 small, physically isolated sand patches along the Great Lakes coast of northern Michigan and northern Wisconsin. While much information was lost to postharvest fire and stump deterioration, 147 fire-free intervals revealed in cross-sections from 29 coastal sand patches document numerous close interval surface fires before 1910; only one post-1910 fire was documented. Cross-sections from the 10 patches with records spanning >150 yr suggest local fire occurrence rates before 1910 ca. 10 times the present rate of lightning-caused fire. Since fire spread between or into coastal sand patches is rare, and seasonal use of the patches by Native people before 1910 is well documented, both historically and ethnographically, ignition by humans probably accounts for more than half of the pre-1910 fires recorded in cross-sections.
Article
The U.S. landscape has undergone substantial changes since Europeans first arrived. Many land use changes are attributable to human activity. Historical data concerning these changes are frequently limited and often difficult to develop. Modeling historical land use changes may be neccessary. We develop annual population series from first European settlement to 1999 for all 50 states and Washington D.C. for use in modeling land use trends. Extensive research went into developing the historical data. Linear interpolation was used to complete the series after critically evaluating the appropriateness of linear interpolation versus exponential interpolation.
Article
The authors begin by outlining the role of the dendrochronologists both in the field and in the laboratory. The basic principles of tree-ring dating are then explained in detail, followed by a guide to the collection of archaeological and modern specimens from the field. The final section deals with the laboratory techniques used: the preliminary processing and preparation of archaeological and modern specimens; the process of dating specimens; and finally the compilation of a master chronology.
Article
Due to the paucity of long-term fire chronologies in the upper Midwest, we studied basal cross-sections dating back to 1822 and the impacts of recent fire suppression in pine and oak stands on the Menominee Indian Reservation in northeast Wisconsin. A total of 93 fire events with a fire-return interval (FRI) of 5.9–17.7 y were recorded across all stands before fire suppression activities in 1935. After 1935, we recorded 29 fires. Most stands have only burned 0–3 times since 1935, and only four of 16 stands yielded enough fire years to calculate FRIs. Superposed Epoch Analysis (SEA) determined significantly lower Palmer Drought Severity Index (PDSI) values 1 y before individual fire years. Fire wounding occurred primarily in the dormant season and average tree diameter at time of wounding ranged from 7–30 cm. Current forest composition was dominated by white pine (Pinus strobus L.) and red maple (Acer rubrum L.) overstories, whereas seedlings and saplings were predominantly eastern hemlock (Tsuga canadensis (L). Carrière), witch-hazel (Hamamelis virginiana L.) and sugar maple (A. saccharum Marsh.). Tree species recorded on similar soils in 19th Century General Land Office surveys were mainly aspen (Populus), white pine and eastern hemlock. We conclude that the combination of logging and decreased fire occurrence over the past century resulted in a compositional shift from historic aspen, pine and oak forests towards later successional northern hardwoods.
Article
To recover direct evidence of surface fires before European settlement, we sectioned fire-scarred logging-era stumps and trees in 39 small, physically isolated sand patches along the Great Lakes coast of northern Michigan and northern Wisconsin. While much information was lost to postharvest fire and stump deterioration, 147 fire-free intervals revealed in cross-sections from 29 coastal sand patches document numerous close interval surface fires before 1910; only one post-1910 fire was documented. Cross-sections from the 10 patches with records spanning >150 yr suggest local fire occurrence rates before 1910 ca. 10 times the present rate of lightning-caused fire. Since fire spread between or into coastal sand patches is rare, and seasonal use of the patches by Native people before 1910 is well documented, both historically and ethnographically, ignition by humans probably accounts for more than half of the pre-1910 fires recorded in cross-sections.
Article
Question: How frequent and variable were fire disturbances in longleaf pine ecosystems? Has the frequency and seasonality of fire events changed during the past few centuries? Location: Kisatchie National Forest, Western Gulf Coastal Plain, longleaf pine–bluestem ecosystem, in relatively rough topography adjacent to the Red River, Louisiana, USA. Methods: Cross-sections of 19 remnant pines exhibiting 190 fire scars were collected from a 1.2-km2 area. Tree-rings and fire scars were precisely dated and analysed for the purpose of characterizing past changes in fire and tree growth. Temporal variability in fire occurrence and seasonality was described for the pre- and post-European settlement periods. Seasonality of historic fires was determined by the scar position within the rings. The relationship between fire and drought was investigated using correlation and superposed epoch analysis. Results: The mean fire return interval for the period 1650-1905 was 2.2 years (range 0.5 to 12 yr). Significant new findings include: evidence for years of biannual burning, temporal variability in fire seasonality, an increase in fire frequency and percentage of trees scarred circa 1790, and synchronous growth suppression and subsequent release of trees coinciding with land-use changes near the turn of the 20th century. Drought conditions appeared unrelated to the occurrence of fire events or fire seasonality. Conclusions: Multi-century fire history records from longleaf pine ecosystems are difficult to obtain due to historic land-use practices and the species high resistance to scarring; however, our results indicate potential for reconstructing detailed fire histories in this ecosystem. Fire scars quantitatively documented one of the most frequent fire regimes known. Fire regime information, such as the temporal variability in fire intervals, prevalence of late-growing season fire events and biannual burning, provide a new perspective on the dynamics of longleaf pine fire regimes.
Article
The complexity inherent in variable, or mixed-severity fire regimes makes quantitative characterization of important fire regime attributes (e.g., proportion of landscape burned at different severities, size and distribution of stand-replacing patches) difficult. As a result, there is ambiguity associated with the term ‘mixed-severity’. We address this ambiguity through spatial analysis of two recent wildland fires in upper elevation mixed-conifer forests that occurred in an area with over 30years of relatively freely-burning natural fires. We take advantage of robust estimates of fire severity and detailed spatial datasets to investigate patterns and controls on stand-replacing patches within these fires. Stand-replacing patches made up 15% of the total burned area between the two fires, which consisted of many small patches (<4ha) and few large patches (>60ha). Smaller stand-replacing patches were generally associated with shrub-dominated (Arctostaphylos spp. and Ceanothus spp.) and pine-dominated vegetation types, while larger stand-replacing patches tended to occur in more shade-tolerant, fir-dominated types. Additionally, in shrub-dominated types stand-replacing patches were often constrained to the underlying patch of vegetation, which for the shrub type were smaller across the two fire areas than vegetation patches for all other dominant vegetation types. For white and red fir forest types we found little evidence of vegetation patch constraint on the extent of stand-replacing patches. The patch dynamics we identified can be used to inform management strategies for landscapes in similar forest types. KeywordsFire regime-Fire severity-RdNBR-Variable severity-Fire management
Article
The shapes of landscapes are fundamental to ecosystem processes at various spatial scales. Topographic roughness index (TRI) is a measure of variability in the landscape surface and a proxy of the potential of disturbances to propagate across the earth's surface, such as a wildland fire burning across a landscape. We describe the significance of TRI, present methods for calculation, and demonstrate the utility of the index in a fire frequency prediction model. The model was used to show how the relationships between topography, fire, and humans changed during the period of AD 1620–1850 for a study area (5180 km2) in Missouri, USA. The model predicted historic mean fire return intervals from TRI and two human population variables. The model explained 46% of the variation in mean fire return intervals and demonstrated that topographic roughness was most important in controlling fire frequency during the period AD 1620–1780 when human population density was lowest (<0.35 humans/km2). Due to increases in human population, mean fire return intervals were shortened by up to one-fourth of their original length and the landscape became more homogeneous with respect to fire frequency despite topographic roughness. The use of TRIs in wildland fire research aid in quantifying and visualizing topographic variability and could be applicable to multiple scales and ecosystem processes.
Article
We used dendrochronological methods to construct three fire history chronologies in the interior of the Boston Mountains of Arkansas from 281 dated fire scars identified on 86 shortleaf pine (Pinus echinata) remnants and trees. We describe and contrast these interior sites with sites on the southern perimeter of Boston Mountains that were documented in an earlier study and examine human, topographic and climatic spatial and temporal controls on these fire regimes. Fire frequency and human population density at the interior sites were positively correlated during an early period (1680–1880) of low levels of population, but were negatively correlated during a later period (1881–2000) as human population levels increased to a much higher level. Wide spread fire occurred more often during drought years in the 1700s with fires likely achieving sizes unprecedented during the last century. The early (before 1810) fire scar record showed that fire intervals were about three times longer (MFI = 35 years) at the interior sites than at the perimeter sites. Early transitional (1810–1830) settlement by Cherokees at population densities under 0.26 humans/km2 was highly correlated (r = 0.90) with the number of fires per decade in the interior region of the Boston Mountains. Multiple regression analyses further implicated humans as well as short- and long-term climate variability such as forced by the El Niño/Southern Oscillation (ENSO) and Atlantic Multidecadal Oscillation (AMO).
Article
Over the past century, trees have encroached into grass- and shrublands across western North America. These include Douglas-fir trees (Pseudotsuga menziesii (Mirb.) Franco var. glauca (Beissn.) Franco) encroaching into mountain big sagebrush (Artemisia tridentata Nutt. ssp. vaseyana (Rydb.) Beetle) from stable islands of savanna in southwestern Montana. Our objectives were to quantify the relative area occupied by mountain big sagebrush and grasslands versus Douglas-fir savanna in the Fleecer Mountains of southwestern Montana today and in the past, and to identify the historical role of fire and other factors in maintaining this distribution. To do this, we reconstructed a multicentury history of tree establishment and surface fires from 1120 trees sampled on a grid of 50 plots covering 1030 ha of a modern mosaic of sagebrush–grasslands and Douglas-fir trees. We compared these histories to time series of climate and land use, and to spatial variation in topography and soil moisture availability. Beginning in the mid-1800s, Douglas-fir trees established in areas in which trees did not persist historically. In 1855, less than half the plots (42%) had trees whereas today, most plots do (94%). This encroachment was synchronous with the cessation of frequent surface fires, likely caused by the advent of domestic livestock grazing, and perhaps by the start of several decades of relatively dry summers. Douglas-fir savannas historically occurred on fire-safe sites more often than did sagebrush–grass. Our inference that frequent fire excluded Douglas-fir in the past was supported by the results of a simulation model of fire and associated vegetation dynamics. In the continued absence of fire, mountain big sagebrush and grasslands in southwestern Montana are likely to become more homogeneous as Douglas-fir trees continue to encroach.
Report on the Huron Mountain Club
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Red pine ( Pinus resinosa) Mountain Lake Master tree-ring chronology, IGBP PAGES/World Data Center for Paleoclimatology Data. Boulder, CO: NOAA/NGC Paleoclimatology Program. Retrieved from ftp Predicting spatio-temporal variability in fire return intervals using a topographic roughness index
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Stambaugh, M. C., & Guyette, R. P. (2008a). Red pine ( Pinus resinosa), Mountain Lake, Huron Mountains, MI (MI020): Master tree-ring chronology, IGBP PAGES/World Data Center for Paleoclimatology Data. Boulder, CO: NOAA/NGC Paleoclimatology Program. Retrieved from ftp://ftp.ncdc.noaa.gov/pub/data/ paleo/treering/measurements/northamerica/usa/mi020.rwl Stambaugh, M. C., & Guyette, R. P. (2008b). Predicting spatio-temporal variability in fire return intervals using a topographic roughness index. Forest Ecology and Management, 254, 463–473.
Predicting ecosystem fire using chemistry and climate
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Guyette, R. G., Stambaugh, M. C., Dey, D., & Muzika, R. M. (2012). Predicting ecosystem fire using chemistry and climate. Ecosystems, 15, 322-335.
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Christy, B. (1929). The book of Huron mountain. Big Bay, MI: Huron Mountain Club.
Landscape ecosystems and cover types of the reserve area and adjacent lands of the Huron Mountain Club (Occasional Papers of the Huron Mountain Wildlife Foundation
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Simpson, T. B., Stuart, P. E., & Barnes, B.V. (1990). Landscape ecosystems and cover types of the reserve area and adjacent lands of the Huron Mountain Club (Occasional Papers of the Huron Mountain Wildlife Foundation, No. 4). Big Bay, MI: Huron Mountain Wildlife Foundation.
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MI (MI020): Master tree-ring chronology, IGBP PAGES/World Data Center for Paleoclimatology Data
  • M C Stambaugh
  • R P Guyette
Stambaugh, M. C., & Guyette, R. P. (2008a). Red pine ( Pinus resinosa), Mountain Lake, Huron Mountains, MI (MI020): Master tree-ring chronology, IGBP PAGES/World Data Center for Paleoclimatology Data. Boulder, CO: NOAA/NGC Paleoclimatology Program. Retrieved from ftp://ftp.ncdc.noaa.gov/pub/data/ paleo/treering/measurements/northamerica/usa/mi020.rwl
Traditional stories from non-traditional sources: Tree rings reveal historical use of fire by Native Americans on Lake Superior's southern shore (Master's thesis
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Torretti, R. L. (2003). Traditional stories from non-traditional sources: Tree rings reveal historical use of fire by Native Americans on Lake Superior's southern shore (Master's thesis, Northern Michigan University). Retrieved from http://www.worldcat.org/title/traditional-stories-from-non-traditional-sourcestree-rings-reveal-historical-use-of-fire-by-native-americans-on-lake-superiorssouthern-shore/oclc/52199882
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