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Percentages of fire scars identified to dormant, earlywood, and latewood posi- tions within tree rings and fire scars where ring position was not determined among hemiboreal peatlands of the upper Great Lakes Region.
Source publication
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,...
Contexts in source publication
Context 1
... scars for which we could assign intra-annual ring position (53.7%) primarily occurred in the dormant and latewood positions (Table 2). Fire scars recorded at Haymeadow Flowage (n = 91) and Betchler Lake (n = 190) for which ring position was assigned were primarily within dormant ring positions, indicating these fire scars formed either after onset of dormancy (i.e., late fall) or prior to new wood formation (i.e., early spring) of the next year. ...Context 2
... scars for which we could assign intra-annual ring position (53.7%) primarily occurred in the dormant and latewood positions (Table 2). Fire scars recorded at Haymeadow Flowage (n = 91) and Betchler Lake (n = 190) for which ring position was assigned were primarily within dormant ring positions, indicating these fire scars formed either after onset of dormancy (i.e., late fall) or prior to new wood formation (i.e., early spring) of the next year. ...Citations
... During this period, i.e., around the middle of the 17th century, extreme droughts occurred in many parts of the world. For example, extreme droughts occurred in South Asia in 1615-1626 [55], South America in 1620-1630 [56], Europe in 1625-1632 [57,58], Australia in 1636-1645 [59], South Africa in 1640-1660 [60], and North America in 1655-1675 [61]. Therefore, many parts of the world experienced severe droughts in different years during this stage (1633-1642) (or near this stage). ...
Exploring periodic dry–wet changes is an important topic in climate change research due to its impact on drought and flood disasters. The purpose of this research was to determine the occurrence law of dry–wet changes in China on a scale of several hundred years, using the example of transitional zones. In this study, we analyzed typical areas of the ecotone between agricultural land and pasture along the Great Wall of China. The ring width index of Carya cathayensis was fitted with the March–August Palmer drought severity index (PDSI38). The PDSI38 was divided into different periods using the stepwise function fitting method. The results indicated that there were two dry periods and one wet period in the region from 1543 to 2019. In each dry and wet period, there were also different temporal periods, including long (decades), intermediate (ten years), and short periods (several years). Drought represents a significant threat to agricultural production in China. In the first dry period (1543–1756), four periods with low PDSI38 values (1633–1635, PDSI38 = −1.71; 1636–1939, PDSI38 = −3.35; 1640–1642, PDSI38 = −4.68; and 1643–1645, PDSI38 = −2.92) occurred, during which severe droughts (PDSI38 < −4) lasted for 13 years. The dry–wet change showed the characteristics of a 12-year or multiple 12-year cycle. The results can be used to prepare to effectively address extreme drought scenarios worldwide in the future.
... Boreal peatland fire return intervals (years between fires) typically range from 100 to 130 years (Turetsky et al., 2004;Wieder et al., 2009); however, over the last two decades, peatland fire return intervals have shortened, with some fires occurring within 20-100 years of a previous fire. While few studies have examined boreal peatland fire return intervals, Sutheimer et al. (2021) found that historic return intervals over the last several centuries for hemi-boreal peatlands south of the Canadian/US Great Lakes could occur as frequently as 7 and 31 years between low-intensity fires. Proximal drivers may also influence the propensity for shortening return intervals and postfire effects . ...
Climate change in northern latitudes is increasing the vulnerability of peatlands and
the riparian transition zones between peatlands and upland forests (referred to as ecotones) to greater frequency of wildland fires. We examined early post-fire vegetation regeneration following the 2011 Utikuma complex fire (central Alberta, Canada). This study examined 779 peatlands and adjacent ecotones, covering an area of ~182 km2. Based on the known regional fire history, peatlands that burned in 2011 were stratified into either long return interval (LRI) fire regimes of >80 years (i.e., no recorded prior fire history) or short fire return interval (SRI) of 55 years (i.e., within the boundary of a documented severe fire in 1956). Data from six multitemporal airborne lidar surveys were used to quantify trajectories of vegetation change for 8 years prior to and 8 years following the 2011 fire. To date, no studies have quantified the impacts of post-fire regeneration following short versus long return interval fires across this broad range of peatlands with variable environmental and post-fire successional trajectories. We found that SRI peatlands demonstrated more rapid vascular and shrub growth rates, especially in peatland centers, than LRI peatlands. Bogs and fens burned in 1956, and with little vascular vegetation (classified as “open peatlands”) prior to the 2011 fire, experienced the greatest changes. These peatlands tended to transition to vascular/shrub forms following the SRI fire, while open LRI peatlands were not significantly different from pre-fire conditions. The results of this study suggest the emergence of a positive feedback, where areas experiencing SRI fires in southern boreal peatlands are expected to transition to forested vegetation forms. Along fen edges and within bog centers, SRI fires are expected to reduce local peatland groundwater moisture-holding capacity and promote favorable conditions for increased fire frequency and severity in the future.
... However, spring is projected to become wetter, whereas late growing seasons will be more variable and with frequent drought periods (Kling et al. 2003). Historical data in the upper Great Lakes Region suggest that fires occurred across all seasons (Guyette et al. 2016;Sutheimer et al. 2021). ...
... Many fire years that burned under moderate conditions have been interpreted as evidence of local, anthropogenic controls (Muzika et al. 2015;Guyette et al. 2016). However, moderately dry conditions can be sufficient for widespread fires even in saturated peatlands (Sutheimer et al. 2021). Anthropogenic fires can be synchronous across large areas, and deciphering contributions of various drivers of fires can be difficult, though increasing drought signals (lower Palmer Drought Index, PDI, values) have been correlated with increasingly widespread fire years (Meunier and Shea 2020). ...
Background Drivers of fire regimes vary among spatial scales, and fire history reconstructions are often limited to stand scales, making it difficult to partition effects of regional climate forcing versus individual site histories. Aims To evaluate regional-scale historical fire regimes over 350 years, we analysed an extensive fire-scar network, spanning 240 km across the upper Great Lakes Region in North America. Methods We estimated fire frequency, identified regionally widespread fire years (based on the fraction of fire-scarred tree samples, fire extent index (FEI), and synchronicity of fire years), and evaluated fire seasonality and climate–fire relationships. Key results Historically, fire frequency and seasonality were variable within and among Great Lakes’ ecoregions. Climate forcing at regional scales resulted in synchronised fires, primarily during the late growing season, which were ubiquitous across the upper Great Lakes Region. Regionally significant fire years included 1689, 1752, 1754, 1791, and 1891. Conclusions We found significant climate forcing of region-wide fire regimes in the upper Great Lakes Region. Implications Historically, reoccurring fires in the upper Great Lakes Region were instrumental for shaping and maintaining forest resilience. The climate conditions that helped promote widespread fire years historically may be consistent with anticipated climate–fire interactions due to climate change.
... Two sites were comprised by unharvested old growth whereas most sites were harvested at the time of cutover but subsequently left relatively undisturbed. Samples were collected from both randomly placed plots used in separate analyses of age structure (e.g., Meunier et al., 2019a, b) as well as opportunistically (Meunier et al. 2019b;Sutheimer et al. 2021). Whether or not fires recorded at study locations were the same as particular fires recorded in historical written accounts cannot be precisely known, but I sought to investigate their correspondence as well as their relative importance described further below. ...
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.
... Multiple stands comprised a site which ranged in size from small pine stands within hardwood forests to more extensive pine forests with efforts to sample comparable areas (0.12-2.41 ha, µ = 0.76 ha). Samples were collected from randomly placed plots as well as opportunistically by searching within ~ 200m of plots for additional samples (Meunier et al. 2019b;Sutheimer et al. 2021). ...
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.
Fire can play an important role in peatlands by modifying plant communities and carbon (C) stocks. However, baseline disturbance data on peatland fire history are lacking in the hemi-boreal region. We sampled 29 peatlands in northern Michigan, Wisconsin, and Minnesota and used peat core records, radiocarbon dating, and infrared spectrometry to identify and date past fire events in 4 major hemi-boreal peatland ecotypes including open poor fens, treed poor fens, forested poor fens, and forested rich fens. In this region all types of poor fens had widely variable fire frequencies between sites. The poor fens experienced 2.1 fires per thousand years, or once every 476 years, on average, while the rich fens experienced almost no fire. Overall C stocks ranged from 10.1 to 263.3 kg C m−2 with a mean of 94.6 and median of 90.5 kg C m−2. The long-term apparent rate of carbon accumulation (LARCA) varied between 10–45 g m−2 y−1 with an average of 28 g m−2 y−1. We found a significant negative relationship between fire frequency and LARCA. Our research indicates that fire frequency is not consistent across peatland types and increases in fire frequency will likely diminish peat C stocks. These findings provide a historical context for management decisions concerning wildland fires and their consequences for ecosystem C storage in hemi-boreal peatlands.
