Fire disturbance of larch woodlands in string fens in northern Québec

2005 ◽  
Vol 83 (6) ◽  
pp. 599-609 ◽  
Author(s):  
Daniel Busque ◽  
Dominique Arseneault
Keyword(s):  
Boreal Forest ◽  
Fire History ◽  
Wood Decay ◽  
Complete Removal ◽  
Tree Density ◽  
Fire Disturbance ◽  
Tree Cover ◽  
Larix Laricina ◽  
Fire Scars ◽  
Large Fires

In this study, dendrochronology was used to reconstruct the fire history and associated dynamics of the last 350 years in three larch (Larix laricina [Du Roi] K. Koch) woodlands in string fens of the northern boreal forest of Quebec. Fire scars were also sampled to reconstruct the fire history across the surrounding uplands. Our results show that string fens are more likely to experience partial disturbance than complete removal of the tree cover during fire. Although large fires burned across the studied landscape in 1733, 1787, 1865, and 1941, no stand-replacing fire has occurred in any of the studied woodlands. At all sites, the oldest larch trees became established around 1640–1680, and several individuals survived each fire identified across the uplands. However, partial disturbance during the most recent 1941 fire, which was associated with severe fire weather, decreased tree density and released the growth of several trees. Although signs of previous fire may have been lost through wood decay, no fire impacted larch growth as severely as the 1941 fire, further emphasizing the modest influence of fire in string fens as compared with uplands. The low fire influence in these minerotrophic peatlands helps explain the high occurrence of the fire-sensitive eastern larch.Key words: boreal forest, fire disturbance, larch woodland, Larix laricina, northern Quebec, string fen.

scholarly journals Integrating fire-scar, charcoal and fungal spore data to study fire events in the boreal forest of northern Europe

The Holocene ◽  
2019 ◽  
Vol 29 (9) ◽  
pp. 1480-1490 ◽  
Author(s):  
Normunds Stivrins ◽  
Tuomas Aakala ◽  
Liisa Ilvonen ◽  
Leena Pasanen ◽  
Timo Kuuluvainen ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Tree Rings ◽  
Fire History ◽  
Statistical Tests ◽  
Sediment Cores ◽  
Fungal Spores ◽  
Fire Dynamics ◽  
Fire Scars ◽  
Fire Event ◽  
Fire Scar

Fire is a major disturbance agent in the boreal forest, influencing many current and future ecosystem conditions and services. Surprisingly few studies have attempted to improve the accuracy of fire-event reconstructions even though the estimates of the occurrence of past fires may be biased, influencing the reliability of the models employing those data (e.g. C stock, cycle). This study aimed to demonstrate how three types of fire proxies – fire scars from tree rings, sedimentary charcoal and, for the first time in this context, fungal spores of Neurospora – can be integrated to achieve a better understanding of past fire dynamics. By studying charcoal and Neurospora from sediment cores from forest hollows, and the fire scars from tree rings in their surroundings in the southern Fennoscandian and western Russian boreal forest, we produced composite fire-event data sets and fire-event frequencies, and estimated fire return intervals. Our estimates show that the fire return interval varied between 126 and 237 years during the last 11,000 years. The highest fire frequency during the 18th–19th century can be associated with the anthropogenic influence. Importantly, statistical tests revealed a positive relationship between other fire event indicators and Neurospora occurrence allowing us to pinpoint past fire events at times when the sedimentary charcoal was absent, but Neurospora were abundant. We demonstrated how fire proxies with different temporal resolution can be linked, providing potential improvements in the reliability of fire history reconstructions from multiple proxies.

The history and pattern of fire in the boreal forest of southeastern Labrador

1983 ◽  
Vol 61 (9) ◽  
pp. 2459-2471 ◽  
Author(s):  
David R. Foster
Keyword(s):  
Boreal Forest ◽  
Fire History ◽  
Fire Regimes ◽  
Strongly Correlated ◽  
History Of ◽  
Large Fires ◽  
Modern Landscape ◽  
Fire Incidence ◽  
Topographic Relief ◽  
Birch Forests

The fire history of the wilderness of southeastern Labrador is marked by a patchy distribution of large fires in time and space. During the 110-year period encompassed by this study, major fires occurred in four decades, 1870–1879, 1890–1899, 1950–1959, 1970–1979. From 1900 to 1951 only 1125 km2 burned; this represents approximately 10% of the total area consumed from 1870 to 1980. Fire records indicate an asynchroneity of the important fire years in southeastern Labrador and adjacent provinces and within Labrador itself. This observation suggests that the meteorological conditions controlling fire occurrence in this portion of the eastern boreal forest are local in nature and extent. The fire rotation for southeastern Labrador is calculated at approximately 500 years, significantly longer than that estimated for other regions of boreal forest. The rare occurrence of large fires is explained by high levels of precipitation and by the preponderance of fire breaks, primarily lakes and peatlands. On the basis of physiographic criteria the region is subdivided into two types of landscape displaying contrasting fire regimes. The large interior plateau, which is covered by extensive peatlands and numerous lakes, has a low fire incidence and extremely long fire rotation. In contrast, large fires are common in the watersheds of the Alexis, Paradise, and St. Augustin rivers where the topographic relief is quite varied and peatlands are scarce. The regional pattern of fire activity has important phytogeographical implications. The lichen woodlands and birch forests are fire-dependent vegetation types; their distribution in the modern landscape is strongly correlated with the historical occurrence of fire during the past 110 years. In addition it is postulated that the historical absence of fire across the large plains in southeastern Labrador has contributed to the development of extensive peatlands in these areas.

Fire history in the southern boreal forest of northwestern Quebec

1993 ◽  
Vol 23 (1) ◽  
pp. 25-32 ◽  
Author(s):  
Pierre-René Dansereau ◽  
Yves Bergeron
Keyword(s):  
Physical Environment ◽  
Fire History ◽  
Age Determination ◽  
Historical Reconstruction ◽  
Fire Scars ◽  
Future Studies ◽  
Fire Cycle ◽  
Large Fires ◽  
Observation Period

Age determination of post-fire forests and the analysis of fire scars on surviving trees have allowed for the historical reconstruction and mapping of fires in a forest area of 11 715 ha in northwestern Quebec, south of Lake Abitibi. Most of the study area was burnt by two large fires (>1000 ha) in 1760 and 1923. All the other fires recorded (1797, 1823, 1870, 1907, 1919) were smaller in extent and occurred in a restricted part (1984 ha) of the study area, characterized by the fragmentation of the forest landscape by water bodies. The compilation of data concerning area burnt per type of surficial material confirms that the physical environment exerts a stronger control on the delimitation of these smaller fires. The data do not allow for the estimation of the fire cycle owing to the small size of the study area and possible temporal changes during the observation period. However, methodological observations are formulated for future studies covering a larger area in the bioclimatic region.

scholarly journals 8,000 years of climate, vegetation, fire and land-use dynamics in the thermo-mediterranean vegetation belt of northern Sardinia (Italy)

2021 ◽  
Author(s):  
Tiziana Pedrotta ◽  
Erika Gobet ◽  
Christoph Schwörer ◽  
Giorgia Beffa ◽  
Christoph Butz ◽  
...  
Keyword(s):  
Land Use ◽  
Bronze Age ◽  
Fire History ◽  
Vegetation History ◽  
Juglans Regia ◽  
Fire Disturbance ◽  
Lake Productivity ◽  
The Past ◽  
Evergreen Oak ◽  
The Bronze Age

AbstractKnowledge about the vegetation history of Sardinia, the second largest island of the Mediterranean, is scanty. Here, we present a new sedimentary record covering the past ~ 8,000 years from Lago di Baratz, north-west Sardinia. Vegetation and fire history are reconstructed by pollen, spores, macrofossils and charcoal analyses and environmental dynamics by high-resolution element geochemistry together with pigment analyses. During the period 8,100–7,500 cal bp, when seasonality was high and fire and erosion were frequent, Erica arborea and E. scoparia woodlands dominated the coastal landscape. Subsequently, between 7,500 and 5,500 cal bp, seasonality gradually declined and thermo-mediterranean woodlands with Pistacia and Quercus ilex partially replaced Erica communities under diminished incidence of fire. After 5,500 cal bp, evergreen oak forests expanded markedly, erosion declined and lake levels increased, likely in response to increasing (summer) moisture availability. Increased anthropogenic fire disturbance triggered shrubland expansions (e.g. Tamarix and Pistacia) around 5,000–4,500 cal bp. Subsequently around 4,000–3,500 cal bp evergreen oak-olive forests expanded massively when fire activity declined and lake productivity and anoxia reached Holocene maxima. Land-use activities during the past 4,000 years (since the Bronze Age) gradually disrupted coastal forests, but relict stands persisted under rather stable environmental conditions until ca. 200 cal bp, when agricultural activities intensified and Pinus and Eucalyptus were planted to stabilize the sand dunes. Pervasive prehistoric land-use activities since at least the Bronze Age Nuraghi period included the cultivation of Prunus, Olea europaea and Juglans regia after 3,500–3,300 cal bp, and Quercus suber after 2,500 cal bp. We conclude that restoring less flammable native Q. ilex and O. europaea forest communities would markedly reduce fire risk and erodibility compared to recent forest plantations with flammable non-native trees (e.g. Pinus, Eucalyptus) and xerophytic shrubland (e.g. Cistus, Erica).

scholarly journals Effects of Soil Abiotic and Biotic Factors on Tree Seedling Regeneration Following a Boreal Forest Wildfire

Ecosystems ◽  
2021 ◽  
Author(s):  
Theresa S. Ibáñez ◽  
David A. Wardle ◽  
Michael J. Gundale ◽  
Marie-Charlotte Nilsson
Keyword(s):  
Boreal Forest ◽  
Betula Pendula ◽  
Fire Severity ◽  
Tree Regeneration ◽  
Soil Biota ◽  
Fire Disturbance ◽  
Burn Severity ◽  
Soil Conditions ◽  
Tree Seedling ◽  
Seedling Regeneration

AbstractWildfire disturbance is important for tree regeneration in boreal ecosystems. A considerable amount of literature has been published on how wildfires affect boreal forest regeneration. However, we lack understanding about how soil-mediated effects of fire disturbance on seedlings occur via soil abiotic properties versus soil biota. We collected soil from stands with three different severities of burning (high, low and unburned) and conducted two greenhouse experiments to explore how seedlings of tree species (Betula pendula, Pinus sylvestris and Picea abies) performed in live soils and in sterilized soil inoculated by live soil from each of the three burning severities. Seedlings grown in live soil grew best in unburned soil. When sterilized soils were reinoculated with live soil, seedlings of P. abies and P. sylvestris grew better in soil from low burn severity stands than soil from either high severity or unburned stands, demonstrating that fire disturbance may favor post-fire regeneration of conifers in part due to the presence of soil biota that persists when fire severity is low or recovers quickly post-fire. Betula pendula did not respond to soil biota and was instead driven by changes in abiotic soil properties following fire. Our study provides strong evidence that high fire severity creates soil conditions that are adverse for seedling regeneration, but that low burn severity promotes soil biota that stimulates growth and potential regeneration of conifers. It also shows that species-specific responses to abiotic and biotic soil characteristics are altered by variation in fire severity. This has important implications for tree regeneration because it points to the role of plant–soil–microbial feedbacks in promoting successful establishment, and potentially successional trajectories and species dominance in boreal forests in the future as fire regimes become increasingly severe through climate change.

Fire regime shift linked to increased forest density in a piñon–juniper savanna landscape

2014 ◽  
Vol 23 (2) ◽  
pp. 234 ◽  
Author(s):  
Ellis Q. Margolis
Keyword(s):  
Regime Shift ◽  
Fire History ◽  
Fire Regime ◽  
Fire Regimes ◽  
Fire Frequency ◽  
Climatic Conditions ◽  
Tree Density ◽  
High Severity ◽  
Wide Range ◽  
In Fire

Piñon–juniper (PJ) fire regimes are generally characterised as infrequent high-severity. However, PJ ecosystems vary across a large geographic and bio-climatic range and little is known about one of the principal PJ functional types, PJ savannas. It is logical that (1) grass in PJ savannas could support frequent, low-severity fire and (2) exclusion of frequent fire could explain increased tree density in PJ savannas. To assess these hypotheses I used dendroecological methods to reconstruct fire history and forest structure in a PJ-dominated savanna. Evidence of high-severity fire was not observed. From 112 fire-scarred trees I reconstructed 87 fire years (1547–1899). Mean fire interval was 7.8 years for fires recorded at ≥2 sites. Tree establishment was negatively correlated with fire frequency (r=–0.74) and peak PJ establishment was synchronous with dry (unfavourable) conditions and a regime shift (decline) in fire frequency in the late 1800s. The collapse of the grass-fuelled, frequent, surface fire regime in this PJ savanna was likely the primary driver of current high tree density (mean=881treesha–1) that is >600% of the historical estimate. Variability in bio-climatic conditions likely drive variability in fire regimes across the wide range of PJ ecosystems.

Degradation or recovery of argan woodlands in South Morocco? Tree count from satellite imagery between 1967–2019 may underestimate pressures on dryland forests status

2021 ◽  
Author(s):  
Irene Marzolff ◽  
Mario Kirchhoff ◽  
Robin Stephan ◽  
Manuel Seeger ◽  
Ali Aït Hssaïne ◽  
...  
Keyword(s):  
Forest Cover ◽  
Canopy Cover ◽  
Biosphere Reserve ◽  
Agroforestry System ◽  
Tree Density ◽  
Tree Cover ◽  
Positive Development ◽  
Natural State ◽  
Remotely Sensed Data ◽  
Change Analysis

<p>In semi-arid to arid South-west Morocco, the once ubiquitous endemic argan tree (<em>Argania spinosa</em>) forms the basis of a traditional silvo-pastoral agroforestry system with complex usage rights involving pasturing and tree-browsing by goats, sheep and camels, smallholder agriculture and oil production. Widespread clearing of the open-canopy argan forests has been undertaken in the 12<sup>th</sup>–17<sup>th</sup> century for sugarcane production, and again in the 20<sup>th</sup> century for fuelwood extraction and conversion to commercial agriculture. The remaining argan woodlands have continued to decline due to firewood extraction, charcoal-making, overgrazing and overbrowsing. Soil and vegetation are increasingly being degraded; natural rejuvenation is hindered, and soil-erosion rates rise due to reduced infiltration and increased runoff. Numerous studies indicate that tree density and canopy cover have been generally decreasing for the last 200 years. However, there is little quantitative and spatially explicit information about these forest-cover dynamics.</p><p>In our study, the tree-cover change between 1967 and 2019 was analysed for 30 test sites of 1 ha each in argan woodlands of different degradation stages in the provinces of Taroudant, Agadir Ida-Outanane and Chtouka-Aït Baha. We used historical black-and-white satellite photography from the American reconnaissance programme CORONA, recent high-resolution multispectral imagery from the commercial WorldView satellites and ultrahigh resolution small-format aerial photography taken with an unmanned aerial system (UAS) to map the presence, absence and comparative crown-size class of 2610 trees in 1967 and 2019. We supplemented the remotely-sensed data with field observations on tree structure and architecture.</p><p>Results show that plant densities reach up to 300 argan trees and shrubs per hectare, and the mean tree density has increased from 58 trees/ha in 1967 to 86 trees/ha in 2019. While 7% of the 1967 trees have vanished today, more than one third of today’s trees could not be observed in 1967. This positive change has a high uncertainty, however, as most of the increase concerns small trees (< 3 m diameter) which might have been missed on the lower-resolution CORONA images.</p><p>When combined with our field data on tree architecture, tree count – albeit a parameter easily attained by remote sensing – is revealed as too simple an indicator for argan-forest dynamics, and the first impression of a positive development needs to be revised: The new small trees as well as trees with decreased crown sizes clearly show much stronger degradation characteristics than others, indicating increased pressures on the argan ecosystem during recent decades. Structural traits of the smaller trees also suggest that the apparent increase of tree count is not a result of natural rejuvenation, but mostly of stump re-sprouting, often into multi-stemmed trees, after felling of a tree. The density of the argan forest in the 1960s, prior to the general availability of cooking gas in the region and before the stronger enforcement of the argan logging ban following the declaration of the UNESCO biosphere reserve, may have marked a historic low in our study area, making the baseline of our change analysis far removed from the potential natural state of the argan ecosystem.</p>

scholarly journals Caribou Conservation: Restoring Trees on Seismic Lines in Alberta, Canada

Forests ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 185 ◽  
Author(s):  
Angelo Filicetti ◽  
Michael Cody ◽  
Scott Nielsen
Keyword(s):  
Boreal Forest ◽  
Rangifer Tarandus ◽  
Site Preparation ◽  
Tree Regeneration ◽  
Tree Density ◽  
Petroleum Exploration ◽  
Rangifer Tarandus Caribou ◽  
Mechanical Site Preparation ◽  
Undisturbed Forest ◽  
Seismic Lines

Seismic lines are narrow linear (~3–8 m wide) forest clearings that are used for petroleum exploration in Alberta’s boreal forest. Many seismic lines have experienced poor tree regeneration since initial disturbance, with most failures occurring in treed peatlands that are used by the threatened woodland caribou (Rangifer tarandus caribou). Extensive networks of seismic lines, which often reach densities of 40 km/km2, are thought to have contributed to declines in caribou. The reforestation of seismic lines is therefore a focus of conservation. Methods to reforest seismic lines are expensive (averaging $12,500 per km) with uncertainty of which seismic lines need which treatments, if any, resulting in inefficiencies in restoration actions. Here, we monitored the effectiveness of treatments on seismic lines as compared to untreated seismic lines and adjacent undisturbed reference stands for treed peatlands in northeast Alberta, Canada. Mechanical site preparation (mounding and ripping) increased tree density when compared to untreated lines, despite averaging 3.8-years since treatment (vs. 22 years since disturbance for untreated). Specifically, treated lines had, on average, 12,290 regenerating tree stems/ha, which is 1.6-times more than untreated lines (7680 stems/ha) and 1.5-times more than the adjacent undisturbed forest (8240 stems/ha). Using only mechanical site preparation, treated seismic lines consistently have more regenerating trees across all four ecosites, although the higher amounts of stems that were observed on treated poor fens are not significant when compared to untreated or adjacent undisturbed reference stands.

Assessing the effects of climate change and land use on northern Labrador forest stands based on paleoecological data

2016 ◽  
Vol 86 (3) ◽  
pp. 260-270 ◽  
Author(s):  
Isabel Lemus-Lauzon ◽  
Najat Bhiry ◽  
James Woollett
Keyword(s):  
Land Use ◽  
Vegetation History ◽  
Ice Age ◽  
Tree Cover ◽  
Forest Composition ◽  
Anthropogenic Factors ◽  
Larix Laricina ◽  
Open Forest ◽  
Historic Land Use ◽  
Study Sites

AbstractWe reconstructed the late Holocene vegetation of the Nain region (northern Labrador, northeastern Canada) in order to assess the influence of climate and historic land use on past shifts in forest composition. Chronostratigraphy was used in combination with macrofossil and pollen data from monoliths sampled from four peatlands. Paleoecological reconstructions produced a vegetation history spanning 4900 years for the Nain region that is largely concordant with other studies in Labrador. An initial open forest tundra phase was followed by an increase in tree cover at around 2800 cal yr BP. Paludification began ∼200 cal yr BP. A decline in Picea and its subsequent disappearance from most of the sites occurred ∼170 cal yr BP (AD 1780) in a period of relatively mild conditions during the Little Ice Age. This event was followed by the establishment of Larix laricina in the region. Local anthropogenic factors are likely responsible for these later developments, as they were not observed in other regional studies. The period around AD 1780 corresponds to the establishment of the Moravian missionaries on the Labrador coast, which increased the need for fuel and lumber. We conclude that changes in land use are reflected in the patterns of vegetation and hydrological change at the study sites.

Mid- and Late Holocene vegetation dynamics and fire history in the boreal forest of European Russia: A case study from Meshchera Lowlands

2016 ◽  
Vol 459 ◽  
pp. 570-584 ◽  
Author(s):  
Elena Yu. Novenko ◽  
Andrey N. Tsyganov ◽  
Elena M. Volkova ◽  
Dmitrii A. Kupriyanov ◽  
Iya V. Mironenko ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Vegetation Dynamics ◽  
Late Holocene ◽  
Fire History ◽  
European Russia
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