Environmental changes in the northern Altai during the last millennium documented in Lake Teletskoye pollen record

A high-resolution pollen record from Lake Teletskoye documents the climate-related vegetation history of the northern Altai Mountain region during the last millennium. Siberian pine taiga with Scots pine, fir, spruce, and birch dominated the vegetation between ca. AD 1050 and 1100. The climate was similar to modern. In the beginning of the 12th century, birch and shrub alder increased. Lowered pollen concentrations and simultaneous peaks in herbs (especially Artemisia and Poaceae), ferns, and charcoal fragments point to colder and more arid climate conditions than before, with frequent fire events. Around AD 1200, regional climate became warmer and more humid than present, as revealed by an increase of Siberian pine and decreases of dry herb taxa and charcoal contents. Climatic conditions were rather stable until ca. AD 1410. An increase of Artemisia pollen may reflect slightly drier climate conditions between AD 1410 and 1560. Increases in Alnus, Betula, Artemisia, and Chenopodiaceae pollen and in charcoal particle contents may reflect further deterioration of climate conditions between AD 1560 and 1810, consistent with the Little Ice Age. After AD 1850 the vegetation gradually approached the modern one, in conjunction with ongoing climate warming.     

Coniferization of the mixed‐wood boreal forests under warm climate

Mixed‐wood boreal forests are characterized by a heterogeneous landscape dominated by coniferous or deciduous species depending on stand moisture and fire activity. Our study highlights the long‐term drivers of these differences between landscapes across mixed‐wood boreal forests to improve simulated vegetation dynamics under predicted climate changes. We investigate the effects of main climate trends and wildfire activities on the vegetation dynamics of two areas characterized by different stand moisture regimes during the last 9000 years. We performed paleofire and pollen analyses in the mixed‐wood boreal forest of north‐western Ontario, derived from lacustrine sediment deposits, to reconstruct historical vegetation dynamics, which encompassed both the Holocene climatic optimum (ca. 8000–4000 a bp ) and the Neoglacial period (ca. 4000 a bp ). The past warm and dry period (Holocene climatic optimum) promoted higher fire activity that resulted in an increase in coniferous species abundance in the xeric area. The predicted warmer climate and an increase in drought events should lead to a coniferization of the xeric areas affected by high fire activity while the mesic areas may retain a higher broadleaf abundance, as these areas are not prone to an increase in fire activity. Copyright © 2019 John Wiley & Sons, Ltd.     

Fire and vegetation change during the Early Pleistocene in southeastern Australia

Early Pleistocene vegetation in upland southeastern Australia included diverse rainforests and sclerophyll forests, which alternated on precessional timescales. The nature and timing of transitions between these biomes, and the role of fire in maintaining or driving transitions between them, are uncertain. Here we present a high‐resolution pollen record from Stony Creek Basin, a small Early Pleistocene palaeolake in southeastern Australia. The pollen record documents a pattern of vegetation change, over ca. 10 ka at ca. 1590–1600 ka, between sclerophyll forests, dominated by Eucalyptus, Callitris (Cupressaceae) or Casuarinaceae, and rainforests dominated by either angiosperms or conifers of the family Podocarpaceae. Transitions between these biomes typically occurred within ca. 1–2 ka. The associated charcoal record suggests that greatest biomass combustion occurred when local vegetation was dominated by Eucalyptus, and the least biomass combustion occurred when local vegetation was dominated by Podocarpaceae. However, local fires burnt in both sclerophyll and angiosperm‐dominated rainforest vegetation, at least once every several centuries. Fire was very rare (less than about one fire per millennium) only when the local vegetation was rainforest dominated by Podocarpaceae. This suggests that fire was an irregular presence in both sclerophyll‐ and angiosperm‐dominated rainforest biomes during the late Neogene, though was largely absent in Podocarpaceae‐dominated rainforests. Copyright © 2011 John Wiley & Sons, Ltd.     

http://www.sciencedirect.com/science/article/pii/S1674987113001606

The paper reviews previous and recently obtained geological, stratigraphic and geochronological data on the Russian-Kazakh Altai orogen, which is located in the western Central Asian Orogenic Belt （CAOB）, between the Kazakhstan and Siberian continental blocks. The Russian-Kazakh Altai is a typical Pacific-type orogen, which represents a collage of oceanic, accretionary, fore-arc, island-arc and continental margin terranes of different ages separated by strike-slip faults and thrusts. Evidence for this comes from key indicative rock associations, such as boninite- and turbidite （graywacke）-bearing volcanogenic-sedimentary units, accreted pelagic chert, oceanic islands and plateaus, MORB-OIB-protolith blueschists. The three major tectonic domains of the Russian-Kazakh Altai are： （1） Altai-Mongolian terrane （AMT）; （2） subduction-accretionary （Rudny Altai, Gorny Altai） and collisional （Kalba-Narym） terranes; （3） Kurai, Charysh-Terekta, North-East, Irtysh and Char suture-shear zones （SSZ）. The evolution of this orogen proceeded in five major stages： （i） late Neoproterozoic-early Paleozoic subduction-accretion in the Paleo-Asian Ocean; （ii） Ordovician-Silurian passive margin; （iii） Devonian-Carboniferous active margin and collision of AMT with the Siberian conti- nent; （iv） late Paleozoic closure of the PAO and coeval collisional magmatism; （v） Mesozoic post-collisional deformation and anarogenic magmatism, which created the modern structural collage of the Russian- Kazakh Altai orogen. The major still unsolved problem of Altai geology is origin of the Altai-Mongolian terrane （continental versus active margin）, age of Altai basement, proportion of juvenile and recycled crust and origin of the middle Paleozoic units of the Gorny Altai and Rudny Altai terranes.     

Fire and Vegetation History from the Coastal Rain Forest of the Western Oregon Coast Range

High-resolution charcoal and pollen analyses were used to reconstruct a 4600-yr-long history of fire and vegetation near Taylor Lake in the wettest forests of coastal Oregon. Today, fires in these forests are rare because the season of ignition does not coincide with months of dry fuels. From ca. 4600 to 2700 cal yr B.P. fire episodes occurred at intervals of 140±30 yr while forest vegetation was dominated by disturbance-adapted taxa such as Alnus rubra. From ca. 2700 cal yr B.P. to the present, fire episodes have become less common, occurring at intervals of 240±30 yr, and fire-sensitive forest taxa, such as Tsuga heterophylla and Picea sitchensis, have become more prominent. Fire occurrence during the mid-Holocene was similar to that of the more xeric forests in the eastern Coast Range and suggests that summer drought was widespread. After ca. 2700 cal yr B.P., a decrease in fire episode frequency suggests that cooler conditions and possibly increased summer fog allowed the establishment of present-day Picea sitchensis forests within the watershed. These results provide evidence that fire has been an important disturbance agent in the Coast Range of Oregon, and variations in fire frequency and climate have led to the establishment of present-day forests.     

Postglacial fire,vegetation, and climate history across an elevational gradient in the Northern Rocky Mountains,USA and Canada

A 13,100-year-long high-resolution pollen and charcoal record from Foy Lake in western Montana is compared with a network of vegetation and fire-history records from the Northern Rocky Mountains. New and previously published results were stratified by elevation into upper and lower and tree line to explore the role of Holocene climate variability on vegetation dynamics and fire regimes. During the cooler and drier Lateglacial period, ca 13,000 cal yr BP, sparsely vegetated Picea parkland occupied Foy Lake as well as other low- and high-elevations with a low incidence of fire. During the warmer early Holocene, from ca 11,000–7500 cal yr BP, low-elevation records, including Foy, indicate significant restructuring of regional vegetation as Lateglacial Picea parkland gave way to a mixed forest of Pinus-Pseudotsuga-Larix. In contrast, upper tree line sites (ca >2000 m) supported Pinus albicaulis and/or P. monticola-Abies-Picea forests in the Lateglacial and early Holocene. Regionally, biomass burning gradually increased from the Lateglacial times through the middle Holocene. However, upper tree line fire-history records suggest several climate-driven decreases in biomass burning centered at 11,500, 8500, 4000, 1600 and 500 cal yr BP. In contrast, lower tree line records generally experienced a gradual increase in biomass burning from the Lateglacial to ca 8000 cal yr BP, then reduced fire activity until a late Holocene maximum at 1800 cal yr BP, as structurally complex mesophytic forests at Foy Lake and other sites supported mixed-severity fire regimes. During the last two millennia, fire activity decreased at low elevations as modern forests developed and the climate became cooler and wetter than before. Embedded within these long-term trends are high amplitude variations in both vegetation dynamics and biomass burning. High-elevation paleoecological reconstructions tend to be more responsive to long-term changes in climate forcing related to growing-season temperature. Low-elevation records in the NRM have responded more abruptly to changes in effective precipitation during the late Holocene. Prolonged droughts, including those between 1200 and 800 cal yr BP, and climatic cooling during the last few centuries continues to influence vegetation and fire regimes at low elevation while increasing temperature has increased biomass burning in high elevations.     

Variations in Holocene fire activity and its controls in the Ningshao Plain,eastern China

Extensive fires pose catastrophic threats to both human and natural ecosystems. Understanding the history of fire, particularly Holocene palaeofire activity in densely populated areas, is essential for predicting future fire risks and developing effective fire management policies. The complexity of fire activity is influenced by various factors, including climate and anthropogenic activities. In this study, we analysed microcharcoal from the top 35.36 m of a well-dated sediment core HMD1401 in Ningshao Plain, eastern China. We combined our findings with phytolith and diatom evidence to obtain a comprehensive understanding of variations in Holocene fire activity and its controls. The results showed that there was higher fire activity during the early and late Holocene and less fire activity during the mid-Holocene. More frequent fire occurred from c. 10 000–7000 cal. a BP and was primarily caused by abundant biomass and high seasonal flammability due to increased annual temperature and precipitation and warm but dry winter climate. Fire occurrences between c. 7000–2000 cal. a BP remained at a low level, except for the periods c. 5900–5600 cal. a BP and c. 5300 cal. a BP, which may have been caused by extreme climate events. The impact of fire caused by human activity was significantly enhanced during the last two millennia.     

Vegetation,fire, and climate history of the northwestern Great Basin during the last 14,000 years

The northwestern Great Basin lies in the transition zone between the mesic Pacific Northwest and xeric intermountain West. The paleoenvironmental history based on pollen, macroscopic charcoal, and plant macrofossils from three sites in the northwestern Great Basin was examined to understand the relationships among the modern vegetation, fire disturbance and climate. The vegetation history suggests that steppe and open forest communities were present at high elevations from ca 11,000 to 7000 cal yr BP, and were replaced by forests composed of white fir, western white pine, and whitebark pine in the late Holocene. Over the last 11,000 years, fires were more frequent in mid-elevation forests (10–25 fire episodes/1000 years) and rare in high-elevation forests (2–5 fire episodes/1000 years). Applying modern pollen–climate relationships to the fossil pollen spectra provided a means to interpret past climate changes in this region. In the past 9000 years summer temperatures decreased from 1 to 4 °C, and annual precipitation has increased 7–15%. These results indicate that the millennial-scale climate forcing driving vegetation changes can be quantified within the intermountain West in general and northwestern Great Basin in particular. In addition, fire can be considered an important component of these ecosystems, but it does not appear to be a forcing mechanism for vegetation change at the resolution of these records.     

古炭屑与古森林火?

森林火普遍发生在地质历史时期中，它对自然植被系统的演替起着重要作用。不同强度和频率的森林火培育出不同类型的植被：频繁的森林火导致草甸的形成，而热带雨林形成的原因之一是森林火的缺乏。古炭屑作为古森林火的遗迹，具有分布广泛、细胞结构保存完好以及原地埋藏等特点，为研究古森林火发生的强度和频率提供了宝贵的材料。古炭屑的出现与当时的气候因素、植被类型和地理状况有密切关系：干旱、少雨的气候常常伴随高频率森林火的发生，表现出古炭屑的数量增多；易燃物种组成的植被易发生森林火，古炭屑的出现也会增多，而耐火树种会降低森林火的强度，古炭屑则出现少。因此，从古炭屑的数量和种类的变化，可探讨古森林火的发生规律，进而推断长期地质历史时期的气候、植被、地理状况的演变。     

Postglacial vegetation, fire, and climate history of the Siskiyou Mountains, Oregon, USA

The forests of the Siskiyou Mountains are among the most diverse in North America, yet the long-term relationship among climate, diversity, and natural disturbance is not well known. Pollen, plant macrofossils, and high-resolution charcoal data from Bolan Lake, Oregon, were analyzed to reconstruct a 17,000-yr-long environmental history of high-elevation forests in the region. In the late-glacial period, the presence of a subalpine parkland of Artemisia, Poaceae, Pinus, and Tsuga with infrequent fires suggests cool dry conditions. After 14,500 cal yr B.P., a closed forest of Abies, Pseudotsuga, Tsuga, and Alnus rubra with more frequent fires developed which indicates more mesic conditions than before. An open woodland of Pinus, Quercus, and Cupressaceae, with higher fire activity than before, characterized the early Holocene and implies warmer and drier conditions than at present. In the late Holocene, Abies and Picea were more prevalent in the forest, suggesting a return to cool wet conditions, although fire-episode frequency remained relatively high. The modern forest of Abies and Pseudotsuga and the present-day fire regime developed ca. 2100 cal yr B.P. and indicates that conditions had become slightly drier than before. Sub-millennial-scale fluctuations in vegetation and fire activity suggest climatic variations during the Younger Dryas interval and within the early Holocene period. The timing of vegetation changes in the Bolan Lake record is similar to that of other sites in the Pacific Northwest and Klamath region, and indicates that local vegetation communities were responding to regional-scale climate changes. The record implies that climate-driven millennial- to centennial-scale vegetation and fire change should be considered when explaining the high floristic diversity observed at present in the Siskiyou Mountains.     

干旱气候因子与森林火灾

森林火灾作为一种自然灾害, 气候变化直接或间接影响森林燃烧的火环境, 进而对火发生和火行为产生影响. 干旱气候条件与森林火灾的发生有密切的关系, 气象条件通过气温、 日照、 蒸发量、 风力、 空气湿度等影响着森林火灾的发生和发展. 一般情况下, 气温高、 降水少、 湿度小、 风力大易发生森林火灾. 在山区, 山谷风和地形影响森林火灾蔓延, 森林火灾的蔓延主要受山谷风所控制, 具有间歇性, 另外地形的变化在很大程度上制约着火势的蔓延. 所以, 要利用不同时段的气象条件、 山风出现的时间及有利地形, 及时组织灭火和控制火势蔓延. 森林火灾的发生有各种类型, 通过对森林火灾中一些特殊火行为及相关元素对火灾发展蔓延影响分析, 找出森林火灾扑救与逃生的方法及注意事项.     

Postglacial history of East European boreal forests in the mid-Kama region,pre-Urals,Russia

The Ural Mountains are an important climatic and biogeographical barrier between European and Siberian forests. In order to shed light on the postglacial formation and evolution of the boreal forests in the European pre-Urals, we obtained a peat sediment core, Chernaya, from the Paltinskoe bog located between the southern taiga and hemiboreal forest zone in the mid-Kama region. We carried out pollen analysis, non-pollen palynomorph analysis, loss-on-ignition tests and radiocarbon dating. Radiocarbon dated records provide centennial to decennial resolution of the vegetation and environmental history of the European pre-Urals for the last 8.8 ka. The postglacial formation of the pre-Uralian hemiboreal forests reveals four important phases: (i) the dominance of Siberian taiga and forest-steppe in the Early Holocene and beginning of the Middle Holocene (8.8–6.9 ka), indicating a dry climate; (ii) the spread of spruce and European broadleaved trees in the Middle Holocene (6.9–4 ka) under wetter climate conditions; (iii) the maximum extent of broadleaved trees coinciding with the arrival and spread of Siberian fir in the Late Holocene (4–2.3 ka); and (iv) the decline of broadleaved trees since the Early Iron Age (2.3 ka – present) possibly due to general climate cooling and logging. While temperate broadleaved trees possibly spread from local refugia in the Urals, fir arrived from Siberia and spread further west. The carbon accumulation rate of Paltinskoe bog (18.9±10.16 g C m⁻² a⁻¹) is close to the average value of carbon accumulation of northern peatlands. Local development of peat is characterized by non-gradual growth with a phase of intensive carbon accumulation between 3.5 and 2.3 ka. The vegetation was strongly influenced by fire in the Early Holocene and by humans since the Early Iron Age practicing deforestation, agriculture and pasture. Phases of increased anthropogenic activity correlate well with the local archaeological data.     

More than a checkbox: engaging youth in disaster risk reduction and resilience in Canada

Fire has become one of the main disturbances in terrestrial ecosystems worldwide. It is known that elevation influences the occurrence of fire events; however, this variable has been poorly studied, although it is of particularly relevance to the Mexican topography. The objective of this research was to analyze the altitudinal distribution of forest fires in Mexico over a period of 11 years. Elevation gradients were defined based on a Digital Elevation Model and the main ecoregions of the country: (1) shrubland and tropical forests (0–1000 masl), (2) grasslands (1001–2000 masl) and (3) temperate forests (>?2000 masl). Each ecoregion was divided into Climate Research Units and the number of fires per unit was quantified. The G Getis–Ord statistic was applied in order to define the spatial patterns presented by the fire events. A relationship between the occurrence of fires and the El Niño Southern Oscillation phenomenon was also determined through a Pearson correlation. The results showed that the occurrence of fire events presented variability along elevation gradients, with elevation a determining factor in their occurrence. Gradient 3, with the highest elevation, had the greatest number of fires and also presented the largest area of fire event clustering. These results contribute to the knowledge of the spatial distribution of forest fires in Mexico and are of value to appropriate decision-making for effective fire management.

     

Monitoring of fire incidences in vegetation types and Protected Areas of India: Implications on carbon emissions

Carbon emissions released from forest fires have been identified as an environmental issue in the context of global warming. This study provides data on spatial and temporal patterns of fire incidences, burnt area and carbon emissions covering natural vegetation types (forest, scrub and grassland) and Protected Areas of India. The total area affected by fire in the forest, scrub and grasslands have been estimated as 48765.45, 6540.97 and 1821.33 km ², respectively, in 2014 using Resourcesat-2 AWiFS data. The total CO ₂ emissions from fires of these vegetation types in India were estimated to be 98.11 Tg during 2014. The highest emissions were caused by dry deciduous forests, followed by moist deciduous forests. The fire season typically occurs in February, March, April and May in different parts of India. Monthly CO ₂ emissions from fires for different vegetation types have been calculated for February, March, April and May and estimated as 2.26, 33.53, 32.15 and 30.17 Tg, respectively. Protected Areas represent 11.46% of the total natural vegetation cover of India. Analysis of fire occurrences over a 10-year period with two types of sensor data, i.e., AWiFS and MODIS, have found fires in 281 (out of 614) Protected Areas of India. About 16.78 Tg of CO ₂ emissions were estimated in Protected Areas in 2014. The natural vegetation types of Protected Areas have contributed for burnt area of 17.3% and CO ₂ emissions of 17.1% as compared to total natural vegetation burnt area and emissions in India in 2014. 9.4% of the total vegetation in the Protected Areas was burnt in 2014. Our results suggest that Protected Areas have to be considered for strict fire management as an effective strategy for mitigating climate change and biodiversity conservation.     

Fire and other disturbances of the forests in Mount Rainier National Park

The recent history of catastrophic disturbances in forests was reconstructed at Mount Rainier National Park. Basic data were ages of trees based on ring counts of early seral conifer species and maps of age-class boundaries from field work and aerial photographs. Maps illustrate age classes of the forests and show disturbances from fires, snow avalanches, and lahars (volcanic mudflows). Fires are by far the most important major disturbers, followed by snow avalanches and lahars. Fires over 250 ha in size are called fire events. Burns over 1000 ha, which may have been one fire or a series of fires within a short time, are called fire episodes. Important fire events or episodes occurred in the years 1230, 1303, 1403, 1503, 1628, 1688, 1703, 1803, 1825, 1856, 1858, 1872, 1886, 1894, 1930, and 1934 A.D. The largest fire episode was in 1230; it affected approximately 47% of the forests in the park. The majority of the forests are over 350 yr old, and several stands are over 1000 yr old. Stands 350 yr and 100 to 200 yr in age are the most extensive age classes in the park. Three fire frequency indices are compared. None describe fire frequency at Mount Rainier well. Natural fire rotation was estimated at about 434 yr. All but two episodes of major fires since 1300 A.D. correspond well with major droughts reconstructed for locations east of the Cascade Range crest. Impacts of humans on the disturbance regime may have increased the frequency of fire in the 1850–1900 period, followed by a decrease in frequency after 1900. Fuel build-up as a result of fire suppression should have no significant impact on fire frequency, since fires are relatively infrequent and fuels accumulate naturally.     

The δ18O and δ13C records in an aragonite stalagmite from Furong Cave,Chongqing, China: A-2000-year record of monsoonal climate

A 7-cm long aragonite stalagmite, FR0510-1, from Furong Cave, Chongqing, was dated by ²¹⁰Pb and ²³⁰Th methods, revealing a-2000-year record of climate history under the influence of the East Asian Monsoon. The FR0510-1 record resembles Dongge Cave DA record on 10–100-year scales, but quite different from the Wanxiang Cave WX42B record, indicating that while stalagmite δ¹⁸O record represents local/regional moisture change, spatial variability of the monsoonal rainfall over eastern China must take into account. During the past 2000 years, climate in Chongqing was relatively wet in the intervals of 50 BC–AD 250, AD 1150–1450 and AD 1600–1950, and relatively dry during the periods of AD 250–1150 and AD 1450–1600. Dry conditions were prevailing over the Medieval Warm Period, whereas wet climates were dominant during the most time of the Little Ice Age in Chongqing area.     

云南阳宗海流域过去13000年植被演替与森林火灾

以云南阳宗海1020 cm长的湖泊沉积物岩芯为研究对象,由7个木屑和树叶残体样的AMS14C测年建立岩芯年代框架,以18~19 cm间隔获取52个样品作花粉/炭屑分析,重建了阳宗海流域过去13000年的植被、气候以及森林火灾历史。研究结果表明,过去13000年植被演替、气候变化和森林火灾可分为5个阶段:1)13200~11000 cal.a B.P.,植被以常绿、落叶阔叶混交林为主,气候温凉湿润,森林火灾多发,后期(12300~11000 cal.a B.P.)随着温度和湿度的降低,森林火灾发生愈加频繁;2)11000~8000 cal.a B.P.,松林扩张,阔叶林缩小,气候较上阶段温暖偏干,森林火灾发生次数明显降低;3)8000~5000 cal.a B.P.,松林和常绿阔叶林占优势,且出现暖热性的枫香林,流域内气温升至13000 cal.a B.P.以来的最高值,湿度进一步降低,但森林火灾发生频率低;4)5000~800 cal.a B.P.,松林扩张至最盛,常绿阔叶林收缩,落叶阔叶林成分增加,气温和湿度均明显下降,森林火灾发生频率有所增加;5)800 cal.a B.P.至今,松林和常绿阔叶林收缩,落叶阔叶成分增加,草本植物中禾本科迅速上升,可能与人类活动有关,森林火灾发生频率低。阳宗海花粉/炭屑记录重建的植被、气候和森林火灾史表明,在滇中地区,落叶阔叶成分易引起森林火灾,冷气候导致多发的森林火灾,冷干气候是宜森林火灾发生的气候条件。     

Dynamics of forest fires and climate in Ilmen nature reserve, 1948–2013

This paper considers the impact of climatic factors on the forest fire rate in Ilmen State Reserve based on 66 years of direct observation data for 1948–2013. This period was marked by a gradual annual increase in the number of recorded fires in the reserve. The higher fire rate is generally related to lengthening of the fire season and more frequent fires in the spring and summer–early autumn periods. We did not obtain sufficient evidence to verify a relation of the higher fire rate to climate changes. The average monthly and seasonal weather conditions can be involved to explain only some causes of the interannual fire rate variability. The observed changes in some climatic characteristics could have contributed to an increase in the fire rate, while others could have reduced it.     

Environmental change and fire history of southern Patagonia (Argentina) during the last five centuries

Geochemical, geophysical, charcoal and pollen analyses from the very poorly investigated southern Patagonian steppe area show that in the vicinity of Laguna Potrok Aike (Santa Cruz Province, Argentina) and north of the Strait of Magellan the detectable impact of Europeans as explorers, settlers and farmers on fire intensity, vegetation and lake ecosystems started with first regional signs during the 1840s. A massive anthropogenic impact on a supra-regional scale followed as the result of the introduction of sheep farming at the end of the 19th century. Furthermore, since the first European explorations, fires in the steppe areas of southernmost Patagonia as recorded at Laguna Potrok Aike occurred contemporaneously in the steppe-forest ecotone further west and probably also in the Andean forest itself. Environmental changes which are not caused by anthropogenic influence are also revealed and were most likely the result of temperature variations and enhanced and reduced wind speeds, respectively. A fire event around AD 1600, before the arrival of European settlers, occurred during a dry period in the forest and steppe-forest ecotone and followed a wet phase in the steppe that caused favorable ignition conditions in all environments.     

A 560-Year Record of Santa Ana Fires Reconstructed from Charcoal Deposited in the Santa Barbara Basin, California

Microscopic charcoal from varved Santa Barbara Basin sediments was used to reconstruct a 560-yr record (A.D. 1425 to 1985) of Santa Ana fires. Comparison of large (>3750 μm²) charcoal with documented fire records in the Santa Barbara Ranger District shows that high accumulations correspond to large fires (>20,000 ha) that occurred during Santa Ana conditions. The charcoal record reconstructed a minimum of 20 large fires in the Santa Barbara region during the study period. The average time between fires shows no distinct change across three different land use periods: the Chumash period, apparently characterized by frequent burning, the Spanish/Early American period with nominal fire control, and the 20th century with active fire suppression. Pollen data support the conclusion that the fire regime has not dramatically changed during the last 500 yr. Comparison of large charcoal particle accumulation rates and precipitation reconstructed from tree rings show a strong relationship between climate and fire history, with large fires consistently occurring at the end of wet periods and the beginning of droughts.