Fire Years Research Articles

Working toward a fire-scar network for the Cumberland Plateau—Fire history results from Bridgestone Nature Reserve at Chestnut Mountain, Tennessee1

We reconstructed historical fire regime characteristics at the Bridgestone Nature Reserve at Chestnut Mountain using tree-ring dated fire scars on live and dead shortleaf pine (Pinus echinata Mill.) trees. Fire-scar records described the historical fire frequency and seasonality from the mid-18th century to present. Overall, we found historical fires occurred relatively frequently, predominantly in the dormant season, and were likely low-severity events. Mean fire intervals (MFIs) were slightly longer in the pre-Euro-American period (1744–1834; MFI = 9.6 yrs) versus the post-Euro-American period (1834–1935; MFI = 5.6 yrs). No fires were recorded after 1940, which in combination with past logging and land uses, is likely a major contributor to the ongoing decline of shortleaf pine and pyrophytic oak species observed here. Surprisingly, the majority of fire event years after 1834 were also recorded at Savage Gulf State Natural Area (52 km to the south), raising questions about potential historical fire sizes, patterns, and driving factors across the Cumberland Plateau landscape. In a landscape where fire-scarred remnants are present but relatively scarce and rapidly disappearing, these data are important for evidencing historical fire regimes and developing a more comprehensive regional network of fire history sites that could reveal valuable historical ecological information for the Cumberland Plateau.

Short-interval fires increasing in the Alaskan boreal forest as fire self-regulation decays across forest types

Climate drivers are increasingly creating conditions conducive to higher frequency fires. In the coniferous boreal forest, the world’s largest terrestrial biome, fires are historically common but relatively infrequent. Post-fire, regenerating forests are generally resistant to burning (strong fire self-regulation), favoring millennial coniferous resilience. However, short intervals between fires are associated with rapid, threshold-like losses of resilience and changes to broadleaf or shrub communities, impacting carbon content, habitat, and other ecosystem services. Fires burning the same location 2 + times comprise approximately 4% of all Alaskan boreal fire events since 1984, and the fraction of short-interval events (< 20 years between fires) is increasing with time. While there is strong resistance to burning for the first decade after a fire, from 10 to 20 years post-fire resistance appears to decline. Reburning is biased towards coniferous forests and in areas with seasonally variable precipitation, and that proportion appears to be increasing with time, suggesting continued forest shifts as changing climatic drivers overwhelm the resistance of early postfire landscapes to reburning. As area burned in large fire years of ~ 15 years ago begin to mature, there is potential for more widespread shifts, which should be evaluated closely to understand finer grained patterns within this regional trend.

Understanding the Greenhouse Gas Impact of Deforestation Fires in Indonesia and Brazil in 2019 and 2020

Deforestation fires are hindering climate change mitigation efforts and compounding global environmental challenges. Indonesia and Brazil have experienced high rates of deforestation fires in recent years, with many of the fires burning in peatland-rich ecosystems. We quantify the greenhouse gas (GHG) emissions associated with the 2019 and 2020 deforestation fires in both countries and determine the share of emissions originating from peatlands. Specifically, we use publicly available data for deforested area estimates and quantify the above-ground biomass (AGB), dry matter, and peat soil emissions associated with these fires. We find that the cumulative emissions impact from deforestation fires in Indonesia and Brazil was 3.7 (±0.4) and 1.9 (±0.2) Gt CO2eq in 2019 and 2020, respectively. Nearly half of this GHG impact can be attributed to emissions from peatlands. However, real-time monitoring tools can underestimate these emissions as fires in peatlands smolder underground and can go undetected by satellites. We compare our results with publicly available land-use and fire emissions data and find that the magnitude of underestimation is of the order of 200–300% for severe fire years and highest in the peatland-rich Brazilian Pantanal. We identify the gaps in current policies that are exacerbating the GHG and climate impacts of deforestation fires in Indonesia and Brazil and emphasize the need for regular pre- and post-fire ground measurement, transparent data sharing, and robust policy enforcement for effective forest and peatland protection.

Examining the status of forest fire emission in 2020 and its connection to COVID-19 incidents in West Coast regions of the United States

Forest fires impact on soil, water, and biota resources. The current forest fires in the West Coast of the United States (US) profoundly impacted the atmosphere and air quality across the ecosystems and have caused severe environmental and public health burdens. Forest fire led emissions could significantly exacerbate the air pollution level and, therefore, would play a critical role if the same occurs together with any epidemic and pandemic health crisis. Limited research is done so far to examine its impact in connection to the current pandemic. As of October 21, nearly 8.2 million acres of forest area were burned, with more than 25 casualties reported so far. In-situ air pollution data were utilized to examine the effects of the 2020 forest fire on atmosphere and coronavirus (COVID-19) casualties. The spatial-temporal concentrations of particulate matter (PM2.5 and PM10) and Nitrogen Dioxide (NO2) were collected from August 1 to October 30 for 2020 (the fire year) and 2019 (the reference year). Both spatial (Multiscale Geographically Weighted Regression) and non-spatial (Negative Binomial Regression) analyses were performed to assess the adverse effects of fire emission on human health. The in-situ data-led measurements showed that the maximum increases in PM2.5, PM10, and NO2 concentrations (μg/m3) were clustered in the West Coastal fire-prone states during August 1 – October 30, 2020. The average concentration (μg/m3) of particulate matter (PM2.5 and PM10) and NO2 was increased in all the fire states severely affected by forest fires. The average PM2.5 concentrations (μg/m3) over the period were recorded as 7.9, 6.3, 5.5, and 5.2 for California, Colorado, Oregon, and Washington in 2019, increasing up to 24.9, 13.4, 25.0, and 17.0 in 2020. Both spatial and non-spatial regression models exhibited a statistically significant association between fire emission and COVID-19 incidents. Such association has been demonstrated robust and stable by a total of 30 models developed for analyzing the spatial non-stationary and local association. More in-depth research is needed to better understand the complex relationship between forest fire emission and human health.

Siberian taiga and tundra fire regimes from 2001–2020

Circum-boreal and -tundra systems are crucial carbon pools that are experiencing amplified warming and are at risk of increasing wildfire activity. Changes in wildfire activity have broad implications for vegetation dynamics, underlying permafrost soils, and ultimately, carbon cycling. However, understanding wildfire effects on biophysical processes across eastern Siberian taiga and tundra remains challenging because of the lack of an easily accessible annual fire perimeter database and underestimation of area burned by MODIS satellite imagery. To better understand wildfire dynamics over the last 20 years in this region, we mapped area burned, generated a fire perimeter database, and characterized fire regimes across eight ecozones spanning 7.8 million km2 of eastern Siberian taiga and tundra from ∼61–72.5° N and 100° E–176° W using long-term satellite data from Landsat, processed via Google Earth Engine. We generated composite images for the annual growing season (May–September), which allowed mitigation of missing data from snow-cover, cloud-cover, and the Landsat 7 scan line error. We used annual composites to calculate the difference Normalized Burn Ratio (dNBR) for each year. The annual dNBR images were converted to binary burned or unburned imagery that was used to vectorize fire perimeters. We mapped 22 091 fires burning 152 million hectares (Mha) over 20 years. Although 2003 was the largest fire year on record, 2020 was an exceptional fire year for four of the northeastern ecozones resulting in substantial increases in fire activity above the Arctic Circle. Increases in fire extent, severity, and frequency with continued climate warming will impact vegetation and permafrost dynamics with increased likelihood of irreversible permafrost thaw that leads to increased carbon release and/or conversion of forest to shrublands.

Marginal imprint of human land use upon fire history in a mire-dominated boreal landscape of the Veps Highland, North-West Russia

Dendrochronological reconstructions inform us about historical climate-fire-human interactions, providing a means to calibrate projections of future fire hazard. Most of these reconstructions, however, have been developed in landscapes with a considerable proportion of xeric sites that could potentially inflate our estimates of the historic levels of fire activity. We provide a 420-year long reconstruction of fires in a mire-dominated landscape of the Veps Nature Park, North-West Russia. The area has mostly escaped large-scale forestry operations in the past and is an example of pristine mid-boreal vegetation with a high (approximately 30% for the area studied) proportion of waterlogged areas with ombrotropic mires. The historical fire cycle was 91.4 years (90% confidence intervals, CI 66.2–137.6 years) over the 1580–1720 period, decreasing to 35.9 (CI 28.1–47.6 years) between 1730 and 1770, and then increasing again to 122.7 years (CI 91.0–178.0 years) over the 1780–2000 period. Early season fires dominated over late season fires during the reconstruction period. We documented a higher fire activity period between 1730 and 1780, resulting from the increase in early season fires. This period coincided with one of the largest multi-decadal declines in the reconstructed spring precipitation since 1600 CE, although we found no significant relationship between fire and precipitation over the whole reconstructed period. The nine largest fire years were associated with negative summer precipitation and positive summer temperature anomalies over the study region. Land-use history of the area did not appear to have an effect on historical fire dynamics. Modern (1996–2016) fire records indicate a regional fire cycle of ∼ 1300 years, featuring a pronounced pattern with early (April–May) and late (July–September) season fires. The uniform fire cycle in the area since 1780, occurrence of nine largest fire years during years with spring-summer droughts, and low ignition frequencies over the last 420 years (0.005 to 0.037 ignitions per year and km2) suggest that the fire regime of the Veps Highland remained largely natural until the onset of the 20th century.

Distribution Pattern of Children with Acute Respiratory Infection during Forest fire at Central Kalimantan Indonesia

Over the past 30 years, forest fire has been one of main ecological issues in Indonesia. Human-caused deforestation was accused to be the reason behind this matter, apart from the drastic changing in global climate. Palangkaraya is one of the citiesaffected by haze of the forest fire in 2015; considered to be the worst year of forest fire with the value of PM10 was above the normal threshold. As the impact to the community wellbeing, the prevalence of acute respiratory infection (ARI) in October 2015was increasing especially in children. The research aimed to analyse the spatial distribution of children with ARI in October 2015 at Palangkaraya City. Data onARI number were collected from Primary Care under Public Health Office of Palangkaraya City. The PM 10 value was collected bythe Environmental Agency of Palangkaraya City. The spatial analyse method was conducted using theAverage Nearest Neighbour (ANN) method. The result shows that the number of ANN ratio is 0.761801. It means that the distribution pattern of children with ARI in Central Kalimantan during the forest fire in October 2015 was in cluster form. Bangladesh Journal of Medical Science Vol. 21(1) 2022 Page : 171-174

Late-Summer Fire Provides Long-Term Control of the Invasive Old World Bluestem (Bothriochloa ischaemum)

Bothriochloa ischaemum (Old World Bluestem) is a problematic invasive grass throughout the southern United States. We measured the long-term effects (12 years) of a single growing-season fire (September 2006) in a grassland dominated by Old World Bluestem. Prescribed fire drastically reduced Old World Bluestem cover (prefire: 76 ± 4% [mean ± standard error], 2007: 8 ± 2%) and cover remained low (21 ± 6%) in 2018 with no additional management. Surprisingly, Old World Bluestem cover in unburned plots decreased 12% during the same time. After the burn, native graminoid cover peaked after 3 years (29 ± 7%) but decreased to 18 ± 5% by 2018, and native annual forb cover, almost absent before the fire, increased dramatically to 39 ± 7% in 2007, then quickly decreased to pre-burn levels. Native perennial forb cover more than doubled in 2007 and continued to increase to 58 ± 5% in 2018. A single growing-season fire greatly reduced the cover of Old World Bluestem, likely due to high fuel loads, low rainfall, and phenological timing; the fire also allowed perennial forbs to establish. Restoring dominance of native grasses after removal of this invasive species will require additional active restoration such as seeding or planting.

Long Term Post-Fire Vegetation Dynamics in North-East Mediterranean Ecosystems. The Case of Mount Athos Greece

Fire is an ecological and disturbance factor with a significant historical role in shaping the landscape of fire-prone environments. Despite the large amount of literature regarding post-fire vegetation dynamics, the north-east Mediterranean region is rather underrepresented in the literature. Studies that refer to the early post fire years and long term research are rather scarce. The current study is conducted in the socially and geographically isolated peninsula of Mount Athos (Holly Mountain) in northern Greece, and it studies vegetation dynamics over a period of 30 years since the last fire. Field data were collected 11 years since the event and were used to identify the present plant communities in the area, using TWINSPAN, and the factors affecting their distribution using CART. Four Landsat (TM, ETM, OLI) images are employed for the calculation of NDVI, which was found effective in detecting the intercommunity variation in the study area, and it is used for long term monitoring. The study includes four communities, from maquis to forest which are common in the Mediterranean region covering a wide altitudinal range. The results suggest that fire affects the various communities in a different way and their recovery differs significantly. While forest communities recover quickly after fire, maintaining their composition and structure, the maquis communities may need several years before reaching the pre-fire characteristics. The dry climatic conditions of the study area are probably the reason for the slow recovery of the most fire prone communities. Given that climate change is expected to make the conditions even drier in the region, studies like this emphasize the need to adopt measures for controlling wildfires and preventing ecosystem degradation.

352 years long fire history of a Siberian boreal forest and its primary driving factor

Fire is a major disturbance agent in the boreal forest, affecting the structure, dynamics and biogeochemical cycles in this biome. In the Asian section of boreal forest, the records of long-term fire history are few that limits our understanding of factors forcing regional fire dynamics. We presented an annually-resolved 352-year (1666–2017) fire chronology based on fire scars of Scots pine ( Pinus sylvestris L.) and Siberian larch ( Larix sibirica Ledeb) from the Transbaikal area in the southeastern Siberia. Fire activity showed an increasing trend from 1720 to 1929 (R 2 = 0.80, P < 0.0001), and a significant decreasing trend from 1920 to 2010 (R 2 = 0.62, P < 0.001). We assessed the potential relationships between drought (as represented by the Palmer Drought Severity Index, PDSI, and the Monthly Drought Code, MDC), ocean-atmosphere circulation and forest fire by Superposed epoch analyses, cross-wavelet analysis and Granger causality analysis. Increased fire activity was associated with stronger drought from previous winter to current summer of fire event years and positive Arctic Oscillation (AO) before and during major fire season (February and April to May), as revealed by superposed epoch analysis. Granger causality pointed to the significant role of drought in driving forest fires. Our findings provide insights into the climate drivers of forest fire activity and its prediction in the Transbaikal region. • Fire history was reconstructed by fire scars in tree rings from 1666 to 2017 in southeastern Siberia. • Fire activity showed a significant increasing trend from 1720 to 1929 and a significant decreasing trend from 1920 to 2009. • Drought was the major climate driver of the fire. • Increased fire activity was associated with the positive Arctic Oscillation (AO) before and during the major fire season (February, April and May).

Regional drought synchronised historical fires in dry forests of the Montane Cordillera Ecozone, Canada

Understanding climate as a driver of low- to moderate-severity fires in the Montane Cordillera Ecozone of Canada is a priority given predicted and observed increases in frequency and severity of large fires due to climate change. We characterised historical fire-climate associations using 14 crossdated fire-scar records and tree-ring proxy reconstructions of summer drought and annual precipitation from the region. We compared fire-climate associations among years when fires burned in multiple study areas. From 1746 to 1945, there were 32 years with moderate fire synchrony in which four to six study areas recorded fire. During four high fire synchrony years, 7 to 10 study areas recorded fire. Below-average annual precipitation and summer drought synchronised fires, whereas infrequent years of high fire synchrony were preceded by a wet summer. After 1945, decreased fire occurrence and synchrony reflects fire exclusion, suppression and climatic variation. Global climate change manifests as blocking high-pressure ridges that superimpose on longer fire-seasons and increased droughts. Combined, they make dry forests increasingly susceptible to synchronous fires, which are difficult to suppress as observed during the record-breaking 2017, 2018 and 2021 fire seasons in British Columbia.

Changes in tree growth synchrony and resilience in Siberian Pinus sylvestris forests are modulated by fire dynamics and ecohydrological conditions

Wildfires are the main disturbance of boreal ecosystems, one of the largest reservoirs of terrestrial carbon. Two-thirds of boreal forests are in Siberia, where peatlands commonly appear mixed with mineral soils. Siberian forests are currently facing a dual shift in environmental conditions regarding climate change and increased fire activity. Therefore, assessing growth patterns of trees subjected to different disturbance regimes is essential to understand the impact of ongoing environmental changes on forest functioning. Following a dendroecological approach, we aimed at analyzing spatial synchrony (âC) patterns of trees subjected to different ecohydrological and fire disturbance conditions in forests of Pinus sylvestris of south-western Siberia. Furthermore, we assessed growth suppression as a proxy for fire occurrence based on tree-ring width chronologies after removing climate signals. Our results endorsed climate as the main driver of âC, which showed different trends depending on substrate type. A release of temperature constraints in the more temperature-limited peat soils led to decreasing âC from mid-1960s onwards, while the opposite pattern was found in mineral soils where stronger reliance on summer precipitation progressively increased âC. However, frequently burned stands suffered a sharp reduction in âC since 1980s likely due to the decoupling of growth from climate as a result of an increase in fire activity. Strong replication of growth suppressions supported by historical and palaeoecological records pointed to 1915, 1952, 1977, 1983, 2003 and 2012 as potential fire years. Post-fire legacies on tree growth after such fire events lasted from one to five years, although differences were modulated by soil type, fire event, growth rate prior fire and tree age. This study highlights the usefulness of addressing spatial synchrony in tree growth and past growth suppressions to disentangle the impacts of climate change and increased fire occurrence on boreal forests.

Carbon dynamics and soil greenhouse fluxes in a Florida's native rangeland before and after fire

Grazing lands, including the native rangelands, cover an extensive area of the southeastern United States, representing an important component of the carbon balance for the region. In Florida, native rangelands extend over 3.1 Mha, experiencing a natural fire frequency between 2 – 5 years and a strong climatic variability. Management includes prescribed fire and mechanical brush control. This study is the first of its kind assessing the impacts of prescribed fire and climatic variability on C dynamics and warming potential in Florida's rangeland. We used a combination of eddy covariance and chamber measurements to estimate net ecosystem C exchange (NEE), greenhouse gas (GHG, CO2, CH4, and N2O) emissions, and C in pre and post-fire aboveground biomass. NEE measurements extended four and a half years since 2016, included a fire event during the fourth year (May 1st, 2019), and two and a half years of GHG measurements . Pre-fire net ecosystem production (NEP) was -368 ± 41 g C m−2 yr−1 and decreased to -181 g C m−2 yr−1 during fire year. After accounting for fire C emissions, net ecosystem C balance was -43 g C m−2 yr−1 in 2019. Soil CO2 dominated GHG emissions increasing 172 g C m−2 yr−1 after fire, N2O fluxes increased from 29, pre-fire year, to 41 g m−2 yr−1 (CO2eqv) post-fire, the ecosystem was a CH4 sink between -1.7 and -3.9 g m−2 yr−1 CO2eqv. The fire effect on C uptake was short-lived, the ecosystem recovered fast after fire, NEP reached pre-fire monthly average two months after, increases in warming potential caused by fire were offset within the next year after. The Florida's rangeland is a suitable ecosystem to mitigate global warming, it acted as a strong C sink offsetting -1148 g C m−2 in four years including a drought and a fire year.

Implementation of Fire Policies in Brazil: An Assessment of Fire Dynamics in Brazilian Savanna

In 2012, the Brazilian government implemented the Federal Brigades Program (FBP), a fire policy strategy to hire and train firefighters to combat wildfires. This study analyzed the impact of this program on fire behavior before (2008–2012) and after (2013–2017) its implementation in the Parque do Araguaia Indigenous Land, the largest indigenous territory with the highest occurrence of fires in the Brazilian tropical savanna. We analyzed the annual pattern of fire incidence in the dry season, the fire impact per vegetation type, the recurrence, and the relationship between fire and precipitation. The datasets were based on active fire products derived from the Moderate Resolution Imaging Spectroradiometer (MODIS), the Landsat and Resourcesat-based burned area products, and the records of the fire combat operations. Our results showed that FBP contributed to the reduction of the number of areas affected by fires and to the formation of a more heterogeneous environment composed of fire-resistant and fire-sensitive native vegetation fragments. On the other hand, after the implementation of the FBP, there was an increase in the recurrence of 3–4 years of fires. We concluded that the FBP is an important public policy capable of providing improvements in fire management activities.

Matadi Masks

Matadi Masks Sihle Ntuli (bio) Matadi Masks // following her voyage through the Congolese port of Matadi, my mother was given three black wooden masks by the local seafarers as a gift. the masks were fine-crafted from redwood, each made distinct by their own unique features, the subtle differences in style for essence. two of the masks were female, the twins carved into an oval shape, with protruding lips & rectangular tribal patterns that appeared like jewelry dangling from wooden ears. the heads of the female masks finished with an elaborate headdress meant to indicate their royalty. the solitary male mask had the same oval shape, though this time there was a large wooden-carved beard, with a distinct tribal design traversing along the flat parts of it. the male lips were less pronounced than their female counterparts. the male mask finishing with its own crown and thus completing the royal set. // the Matadi masks were inspired by Congolese aristocracy, alluding to the storied lineage of the ancient kingdom of Kongo & on her return home, my mother placed the Matadi masks on adjacent walls all along the lounge. the museum aesthetics on display on the walls reminds me that of all the souvenirs that my mother brought home from the sea, it was these Matadi masks that I found to be the most frightening. the oracular spectacle of lifelike form, animism held back by fine & precise detail of a wooden carved indifference. // there were holes carved in the eyes of the Matadi masks, these holes only fueled my fear, doing nothing to calm me. in my eyes, the mystery of the masks was all-seeing, in silence my mind moving towards [End Page 214] an unproven conclusion. of the natural light, on masks appearing harmless, motionless and dead on the living room wall. though at sunset, the false pretense of masks pretending to be still. perhaps it was the glow of incandescent bulbs that gave them a whole new life, & when the lights were turned off, I could have sworn that sometimes I could behold the sight of the mask moving. first to silhouette then fully formed, gradually coming towards me, the presence. in truth, the masks for the Congolese coast of Matadi, it was only fear from a young mind's hallucinations. // on human nature, the firmness of our ways, the waywardness of our eyes, the stay-still maladaptive hush. a touch of change, a barrage of resistance. blind noble seers of royalty looking into me. it was when they found a flaw inside of me that I was humbled by their lesson & began to grow fond of the Matadi masks, unable to hold the lesson firmly, I grew attached to them & in their wisdom of ancient nobility. // so time years went by & the masks have taken on a new meaning. on the nature of time, the unravelling of origins of self. it happened as the masks began to age, time has given them a reddish tinge, serving as a reminder to me, to respect the mature and wise set of Matadi masks & the tree sacrificed to deliver this noble teaching. [End Page 215] Sihle Ntuli Sihle Ntuli is a South African poet living in Durban, KwaZulu Natal. He is a holder of a Master of Arts degree in Classical Civilizations obtained from Rhodes University in Makhanda, Eastern Cape. Ntuli has previously lectured at the University of the Free State in Bloemfontein. He was shortlisted for the DALRO Poetry Prize in 2017. His work has appeared in notable African publications such as Lolwe, Down River Road, & Olongo Africa. He is also featured in the anthology Years of Fire and Ash: South African Poems of Decolonization (Jonathan Ball 2021). He recently released his poetry chapbook Rumblin (Uhlanga Press 2020) Copyright © 2020 Hutchins Center for African and African American Research at Harvard University

Wildfire smoke as a driver of covid-19 fatality rates? A synthetic control analysis of San Francisco Bay Area Counties

BACKGROUND AND AIM: The 2020 wildfire season broke records for the most active fire year on the West Coast, resulting in the worst air quality observed in decades. Concurrently, the public health threat of COVID-19 has caused approximately 3.6 million cases and 59,000 deaths in California to date. Due to the association between air pollution and respiratory disease outcomes, wildfire-specific particulate matter exposure is a hypothesized driver of COVID-19 severity. While several studies have considered this association, methodological challenges exist to study this question due to the ecological fallacy and threat of unmeasured confounders in this proposed etiological question. Additionally, no study has considered wildfire smoke as a natural experiment. This study proposes synthetic control methods (SCM) to study the impact of wildfire smoke on COVID-19 mortality rates, considering smoke exposure as a natural experiment. The San Francisco Bay Area (SFBA)—a densely populated region with record-high smoke exposure—is ideal to study this question. METHODS: The CDC COVID data tracker was used to compute weekly case-fatality ratios for each county in the United States from May 11th to November 10th, 2020. The NOAA hazard mapping Smoke Product was used to identify county-level wildfire smoke exposure; counties with area covered by heavy smoke surpassing 70% on average in a given week were considered exposed. Unexposed counties were considered as potential controls. Counties were considered eligible if more than 100 COVID-19 deaths were reported during the study period. RESULTS:Exposure to heavy smoke started between the weeks starting August 26th to September 7th in six eligible counties in which 1,307 COVID-19 deaths occurred within the study period. Results indicate some counties observed an increase in case fatality ratios, while other counties didn’t exhibit change. CONCLUSIONS:Results can be used to understand environmental drivers of COVID-19 mortality, and protect vulnerable populations from concurrent and potentially concomitant public health threats. KEYWORDS: Covid-19, wildfire smoke, synthetic control method

Fire history of Pinus nigra in Western Anatolia: A first dendrochronological study

Forests in the Mediterranean basin frequently experience fires due to both anthropogenic and natural causes. There are concerns that the fire season will prolong in the Mediterranean basin, the fire frequency will increase with ongoing climate change, moreover, the fire regimes will shift from surface fires to local crown fires. Here, we aim to improve our understanding of the fire regime components of black pine forests in Turkey by 1) reconstructing a high-resolution fire chronology based on tree rings, 2) revealing the seasonality of fires, 3) investigating the relationship between fire and climate, and 4) comparing our reconstruction results with documentary data from forest management units. We collected 62 fire-scarred trees from three sites in Kütahya and developed a 368 year-long (1652–2019) composite fire chronology using dendrochronological methods. We found that at two sites major fire years coincided with dry years. Two major fire years (1853 and 1879) were common to all sites and two additional fire years (1822 and 1894) were found at two sites. Our results show a sharp decline in fire frequency after the beginning of the 20th century at all sites that can be attributed to increased fire suppression efforts and forest management activities in the 20th century. Our results suggest that the spread of fires has been actively suppressed since the first forest protection law in Turkey. Yet, tree-ring based and documentary data corroboration shows that seasonality did not change over the past +350 years.

Historical fire regimes of North American hemiboreal peatlands

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.

Holocene Fire Regime Changes in the Southern Lake Baikal Region Influenced by Climate-Vegetation-Anthropogenic Activity Interactions

Catastrophic fire years that have taken place during the last decade in Siberia, and more generally within the boreal forest, have been directly linked to global warming and had strong repercussions on boreal ecosystems and human populations. In this context the study of the past dynamics of these fires is essential for understanding their links with climate, vegetation and human activity changes on longer time scales than the last few decades. However, few studies on fire dynamics are available for Siberia, and none have been conducted for the entire Holocene period. This study presents the first fire history reconstruction of this area during the Holocene based on charcoals sequestered in sediments of two lakes located on the southern shore of Lake Baikal, in Siberia. The results show a similar trend in the two lakes, with high frequency and high peak magnitude during the Early Holocene and low magnitudes after 6500 cal. yr BP. This difference is interpreted as crown fires versus surface fires. According to pollen records (Dulikha, Vydrino, Ochkovoe) available near the studied lakes, a vegetation transition occurred at the same time. Picea obovata, which has a tree structure prone to crown fires, was dominant during the Early humid Holocene. After 6500 cal. yr BP, conditions were drier and Pinus sylvestris and Pinus sibirica became the dominant species; their tree structure favors surface fires. In addition to vegetation dynamics, the nearby pollen sequence from Dulikha has been used to provide quantitative estimates of past climate, indicating an Early to Middle Holocene climatic optimum between 8000 and 5000 cal. yr BP and an increase in temperatures at the end of the Holocene. These results have been compared to outputs from regional climate models for the Lake Baikal latitudes. Fire dynamics appear to have been more linked to the vegetation than climatic conditions. Over the past 1500 years, the greater presence of human populations has firstly resulted in an increase in the fire frequency, then in its maintenance and finally in its suppression, which may possibly have been due to very recent fire management, i.e., after ca 500 cal. BP.

Spatio-temporal patterns of extreme fires in Amazonian forests

Fires are a fundamental part of the Earth System. In the last decades, they have been altering ecosystem structure, biogeochemical cycles and atmospheric composition with unprecedented rapidity. In this study, we implement a complex networks-based methodology to track individual fires over space and time. We focus on extreme fires—the 5% most intense fires—in the tropical forests of the Brazilian Legal Amazon over the period 2002–2019. We analyse the interannual variability in the number and spatial patterns of extreme forest fires in years with diverse climatic conditions and anthropogenic pressure to examine potential synergies between climate and anthropogenic drivers. We observe that major droughts, that increase forest flammability, co-occur with high extreme fire years but also that it is fundamental to consider anthropogenic activities to understand the distribution of extreme fires. Deforestation fires, fires escaping from managed lands, and other types of forest degradation and fragmentation provide the ignition sources for fires to ignite in the forests. We find that all extreme forest fires identified are located within a 0.5-km distance from forest edges, and up to 56% of them are within a 1-km distance from roads (which increases to 73% within 5 km), showing a strong correlation that defines spatial patterns of extreme fires.