scholarly journals Fire risk modulation by long-term dynamics in land cover and dominant forest type in Eastern and Central Europe

2019 ◽  
Author(s):  
Angelica Feurdean ◽  
Boris Vannière ◽  
Walter Finsinger ◽  
Dan Warren ◽  
Simon C. Connor ◽  
...  
Keyword(s):  
Land Cover ◽  
Fire Regime ◽  
Forest Type ◽  
Full Range ◽  
Fire Risk ◽  
Early Holocene ◽  
Tree Cover ◽  
Data Set ◽  
The Past

Abstract. Wildfire occurrence is influenced by climate, vegetation and human activities. A key challenge for understanding fire-climate-vegetation interactions is to quantify the effect vegetation has in mediating fire regime. Here, we explore the relative importance of Holocene land cover and dominant functional forest type, and climate dynamics on biomass burned in temperate and boreo-nemoral regions of Central and Eastern Europe over the past 12 ka BP years. We used an extensive data set of Holocene pollen and sedimentary charcoal records, in combination with climate simulations and novel statistical modelling. Biomass burned was highest during the early Holocene and lowest during the mid Holocene in all three ecoregions, but diverged more markedly over the past 3–4 ka BP. Although the climate was an important driver of fire hazard during the warm and dry early Holocene, tree cover was consistently the strongest predictor of past biomass burning. In temperate forests, biomass burned was high at ~ 45 % tree cover and decreased strongly towards 60 % tree cover. In needleleaf dominated forests, biomass burned was highest at ~ 60–65 % tree cover and abruptly declined at > 65 % tree cover. Biomass burned also increased when arable lands and grasslands reached ~ 15–20 %, although this relationship was highly dynamic depending on land use intensity throughout ignition and fuel type and availability. Our observations cover the full range of Holocene climate variability and land cover changes and illustrates that percentages of land cover is a key predictor of the probability of fire occurrence over timescales of centuries to millennia. We suggest that long-term fire risk may be effectively reduced through land cover management, given that land cover has controlled fire regimes under the dynamic climates of the Holocene.

scholarly journals Fire hazard modulation by long-term dynamics in land cover and dominant forest type in eastern and central Europe

2020 ◽  
Vol 17 (5) ◽  
pp. 1213-1230 ◽  
Author(s):  
Angelica Feurdean ◽  
Boris Vannière ◽  
Walter Finsinger ◽  
Dan Warren ◽  
Simon C. Connor ◽  
...  
Keyword(s):  
Land Use ◽  
Land Cover ◽  
Biomass Burning ◽  
Forest Type ◽  
Fire Hazard ◽  
Fire Regimes ◽  
Early Holocene ◽  
Tree Cover ◽  
The Past

Abstract. Wildfire occurrence is influenced by climate, vegetation and human activities. A key challenge for understanding the risk of fires is quantifying the mediating effect of vegetation on fire regimes. Here, we explore the relative importance of Holocene land cover, land use, dominant functional forest type, and climate dynamics on biomass burning in temperate and boreo-nemoral regions of central and eastern Europe over the past 12 kyr. We used an extensive data set of Holocene pollen and sedimentary charcoal records, in combination with climate simulations and statistical modelling. Biomass burning was highest during the early Holocene and lowest during the mid-Holocene in all three ecoregions (Atlantic, continental and boreo-nemoral) but was more spatially variable over the past 3–4 kyr. Although climate explained a significant variance in biomass burning during the early Holocene, tree cover was consistently the highest predictor of past biomass burning over the past 8 kyr. In temperate forests, biomass burning was high at ∼45 % tree cover and decreased to a minimum at between 60 % and 70 % tree cover. In needleleaf-dominated forests, biomass burning was highest at ∼ 60 %–65 % tree cover and steeply declined at >65 % tree cover. Biomass burning also increased when arable lands and grasslands reached ∼ 15 %–20 %, although this relationship was variable depending on land use practice via ignition sources, fuel type and quantities. Higher tree cover reduced the amount of solar radiation reaching the forest floor and could provide moister, more wind-protected microclimates underneath canopies, thereby decreasing fuel flammability. Tree cover at which biomass burning increased appears to be driven by warmer and drier summer conditions during the early Holocene and by increasing human influence on land cover during the late Holocene. We suggest that long-term fire hazard may be effectively reduced through land cover management, given that land cover has controlled fire regimes under the dynamic climates of the Holocene.

Supplementary material to "Fire risk modulation by long-term dynamics in land cover and dominant forest type in Eastern and Central Europe"

2019 ◽  
Author(s):  
Angelica Feurdean ◽  
Boris Vannière ◽  
Walter Finsinger ◽  
Dan Warren ◽  
Simon C. Connor ◽  
...  
Keyword(s):  
Land Cover ◽  
Central Europe ◽  
Forest Type ◽  
Fire Risk ◽  
Supplementary Material

scholarly journals European wind variability over 140 yr

2013 ◽  
Vol 10 (1) ◽  
pp. 51-58 ◽  
Author(s):  
P. E. Bett ◽  
H. E. Thornton ◽  
R. T. Clark
Keyword(s):  
Full Range ◽  
Reanalysis Data ◽  
Data Set ◽  
Wind Speeds ◽  
The Past ◽  
North East ◽  
The North ◽  
Uncertainty Estimates ◽  
Mean Wind Speed

Abstract. We present initial results of a study on the variability of wind speeds across Europe over the past 140 yr, making use of the recent Twentieth Century Reanalysis data set, which includes uncertainty estimates from an ensemble method of reanalysis. Maps of the means and standard deviations of daily wind speeds, and the Weibull-distribution parameters, show the expected features, such as the strong, highly-variable wind in the north-east Atlantic. We do not find any clear, strong long-term trends in wind speeds across Europe, and the variability between decades is large. We examine how different years and decades are related in the long-term context, by looking at the ranking of annual mean wind speeds. Picking a region covering eastern England as an example, our analyses show that the wind speeds there over the past ~ 20 yr are within the range expected from natural variability, but do not span the full range of variability of the 140-yr data set. The calendar-year 2010 is however found to have the lowest mean wind speed on record for this region.

Long-term variations in the geomagnetic activity level Part II: Ascending phases of sunspot cycles

1994 ◽  
Vol 12 (10/11) ◽  
pp. 1065-1070 ◽  
Author(s):  
V. Mussino ◽  
O. Borello Filisetti ◽  
M. Storini ◽  
H. Nevanlinna
Keyword(s):  
Correlation Coefficient ◽  
Geomagnetic Activity ◽  
Activity Level ◽  
Activity Levels ◽  
Data Set ◽  
The Past ◽  
Long Term Trends ◽  
A Minor ◽  
Long Term Variations

Abstract. Monthly averages of the Helsinki Ak-values have been reduced to the equivalent aa-indices to extend the aa-data set back to 1844. A periodicity of about five cycles was found for the correlation coefficient (r) between geomagnetic indices and sunspot numbers for the ascending phases of sunspot cycles 9 to 22, confirming previous findings based on a minor number of sunspot cycles. The result is useful to researchers in topics related to solar-terrestrial physics, particularly for the interpretation of long-term trends in geomagnetic activity during the past, and to forecast geomagnetic activity levels in the future.

Reduced diversity and productivity of diatoms and other protists during the Early Holocene in the subarctic North Pacific

2020 ◽  
Author(s):  
Heike H. Zimmermann ◽  
Stefan Kruse ◽  
Kathleen R. Stoof-Leichsenring ◽  
Luise Schulte ◽  
Dirk Nürnberg ◽  
...  
Keyword(s):  
Green Algae ◽  
Taxonomic Diversity ◽  
Taxonomic Composition ◽  
Shotgun Sequencing ◽  
Early Holocene ◽  
The Past ◽  
Subarctic North Pacific ◽  
Morphological Differences ◽  
Marine Protists

<p>Marine protists are a phylogenetically diverse group of single-celled eukaryotes that respond sensitively to changes in environmental conditions. Yet, our understanding how long-term climate variability has shaped the taxonomic composition is mostly unknown, especially of non-biomineralizing groups, such as green algae, since traditional micropaleontological studies are limited to the analysis of microfossil remains with often hardly discernable morphological differences between species (e.g. diatoms). Here we present a sedimentary ancient DNA (<em>sed</em>aDNA) record of the marine sediment core SO201-2-12KL, which was retrieved from the eastern continental slope of Kamchatka at 2173 m water depth (N 53.992660°, E 162.375830°) and covers the past 19.9 thousand years. We applied <em>sed</em>aDNA metabarcoding to 63 samples using a diatom-specific, short plastid marker that is part of the <em>rbcL</em> gene. Additionally, we used metagenomic shotgun sequencing on a subset of 26 samples to investigate the overall taxonomic composition of protists. Metagenomic shotgun sequencing revealed a variety of unicellular plankton groups mostly from green algae (especially <em>Bathycoccus</em>) and diatoms. At 11.1 cal kyr BP only single sequences assigned to green algae, diatoms and coccolithophorids could be detected. Metabarcoding showed strong variability in the richness of diatom sequence variants, which was highest during Heinrich Stadial 1 and the Younger Dryas. From about 11.4 cal kyr BP diatom taxonomic diversity strongly decreased until about 10.7 cal kyr BP. This was associated with highest taxonomic and phylogenetic turnover recorded over the past 19.9 cal kyr. Concomitant with this we recorded sequences assigned to <em>Skeletonema</em> <em>subsalsum</em>, a coastal diatom associated with low salinities or freshwater. Tentatively, as we wait for the confirmation by further sequencing, we suggest that the reduced protist diversity during the Early Holocene resulted from sea surface freshening, which led to a strengthened vertical stratification which could have reduced past productivity due to limited nutrient supply from deeper waters to the photic zone.</p>

Recent fire activity in the boreal forests of central western Siberia is unprecedented in the past 5000 years: palaeoenvironmental evidence contextualises a burning issue

2020 ◽  
Author(s):  
Angelica Feurdean ◽  
Andrei Cosmin Diaconu ◽  
Gabriela Florescu ◽  
Mariusz Galka ◽  
Simon M. Hutchinson ◽  
...  
Keyword(s):  
Plant Communities ◽  
Tree Species ◽  
Boreal Forests ◽  
Western Siberia ◽  
Fire Regime ◽  
Fire Regimes ◽  
Vegetation Composition ◽  
The Past ◽  
Invader Species

<p>Although wildfire events in Siberia have increased in frequency and intensity over recent decades, in the absence of long-term records, it is not clear how far this trend deviates from baseline conditions. Short-term datasets categorise the forest fire regime in Siberia as one of surface, litter fires alternating withdevastating crown fires, although there is significant variability within this region likely reflecting vegetation composition. However, a comprehensive understanding of how vegetation composition and properties determine fire regimes remains lacking. To address this question we used two peat records spanning the last 2500 yr and a 5000 yr, respectively of charcoal morphologies-derived fire regime, pollen-based vegetation dynamics and stable isotope and testate amoebae-based climate reconstructions from boreal forests in central western Siberia, combined with fire-related functional traits of key boreal tree species. Compared to the trend over the 5000 yr period (mean fire return interval=FRI of 400 yr), our reconstructed mean FRI of 145 yr for the last five centuries is notably the shortest in the record. Most fires in this area tend to be surface, litter fires, although over the last centuries surface fires show an increased trend towards crowning. Frequent fires between 5000 and 4000 cal yr BP and 1500 cal yr BP to the present were concurrent with the dominance of invader species (primarily Betula) and fire endurer (mainly herbs) with prevalence of resisters (Pinus sylvestris, Pinus sibirica). Longer fire return intervals (up to 500 yr) between 4000 and 1500 cal yr BP were associated with the dominance of fire resisters with a considerable proportion of fire avoiders (Abies sibirica and Picea obovata). The rising number of fire episodes and the intensification of fire events over the past 1500 years have likely promoted fire-adapted plant communities (invaders and endurers) that can rapidly reach maturity, contributing to the reduction of avoider and resister species. This trend demonstrates that fire avoider species particularly fail to regenerate if the intervals between fire episodes are too short and thatan increasing number of fire episodes can drive land cover towards more fire-adapted plant communities. Our long-term perspective shows that the current fire regime lies significantly outside baseline conditions, which may drive future change in forest composition towards an increased prevalence of invader species. This study also contributes to an understanding of disturbance regimes in Pinus-Betula forests and considers the potential of tree species to adapt to new fire regimes.</p><p> </p>

scholarly journals Automatic polygon layers integration and its implementation

2012 ◽  
Vol 60 (4) ◽  
pp. 335-342
Author(s):  
Ondřej Skoupý ◽  
David Procházka
Keyword(s):  
Land Cover ◽  
Land Cover Change ◽  
Landscape Management ◽  
Anthropogenic Factors ◽  
Spatial Integration ◽  
Change Analysis ◽  
Data Set ◽  
Natural Processes ◽  
Land Cover Change Analysis

Land cover change analysis is one of the most important tools for landscape management purposes, as it enables exploring of long-term natural processes especially in contrast with anthropogenic factors. Such analysis is always dependent on quality of available data. Due to long tradition of map making and quality and accuracy of preserved historical cartographic data in the Czech Republic it is possible to perform an effective land use change analysis using maps dating even back to early nineteenth century. Clearly, because map making methodology has evolved since then, the primary problem of land cover change analysis are different sources and thus different formats of analyzed data which need to be integrated, both spatially and contextually, into one coherent data set. One of the most difficult problems is caused by the fact that due to different map acquisition methodologies the maps are loaded with various errors originating from measurement, map drawing, storage, digitalization and finally georeferencing and possible vectorization. This means that some apparent changes may be for example caused by different methodology and accuracy of mapping a landscape feature that has not actually changed its shape and spatial position through the time. This work deals with spatial integration of data, namely identifying corresponding lines in map layers from different epochs and adjusting the borders plotted in the less accurate map to spatially correspond to the more accurate map. For such a purpose, a special program had to be created. It basically follows the work by Malach et al., 2009 who introduced their Layer Integrator. This work however presents a significantly different approach to creating an integration tool.

Long Term Variations in Jupiter’s 11 cm Radio Emission

1975 ◽  
Vol 2 (6) ◽  
pp. 340-342
Author(s):  
P.M. McCulloch
Keyword(s):  
Radio Emission ◽  
Orbital Period ◽  
Full Range ◽  
Rotational Axis ◽  
The Past ◽  
Range Of Values ◽  
Long Term Variations

During the past twelve years five series of observations have been made of the polarization of Jupiter’s radio emission at a wavelength of 11 cm. This data shows characteristics which have been stable over a period of years as well as some unexplained variations. The observations were made during one complete orbital period of Jupiter and hence were obtained over the full range of values of DE, the angle between Jupiter’s rotational axis and the plane of the sky. These are summarized in Table 1. The 1967 observations have been reported previously (Komesaroff and McCulloch 1967) and the 1963 data is from Roberts and Komesaroff (1965).

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