15 research outputs found
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Long-term ecological consequences of forest fires in the continuous permafrost zone of Siberia
Abstract
Wildfires are an important factor in controlling forest ecosystem dynamics across the circumpolar boreal zone. An improved understanding of their direct and indirect, short- to long-term impacts on vegetation cover and permafrost–vegetation coupling is particularly important to predict changes in carbon, nutrient and water cycles under projected climate warming. Here, we apply dendrochronological techniques on a multi-parameter dataset to reconstruct the effect of wildfires on tree growth and seasonal permafrost thaw depth in Central Siberia. Based on annually-resolved and absolutely dated information from 19 Gmelin larch (Larix gmelinii (Rupr.) Rupr.) trees and active soil layer thickness measurements, we find substantial stand-level die-off, as well as the removal of ground vegetation and the organic layer following a major wildfire in 1896. Reduced stem growth coincides with increased δ
13C in the cellulose of the surviving trees during the first decade after the wildfire, when stomatal conductance was reduced. The next six to seven decades are characterized by increased permafrost active soil layer thickness. During this period of post-wildfire ecosystem recovery, enhanced tree growth together with positive δ
13C and negative δ
18O trends are indicative of higher rates of photosynthesis and improved water supply. Afterwards, a thinner active soil layer leads to reduced growth because tree physiological processes become limited by summer temperature and water availability. Revealing long-term effects of forest fires on active soil layer thickness, ground vegetation composition and tree growth, this study demonstrates the importance of complex vegetation–permafrost interactions that modify the trajectory of post-fire forest recovery across much of the circumpolar boreal zone. To further quantify the influence of boreal wildfires on large-scale carbon cycle dynamics, future work should consider a wide range of tree species from different habitats in the high-northern latitudes.</jats:p
Ecological and conceptual consequences of Arctic pollution
This is the final version. Available on open access from Wiley via the DOI in this recordAlthough the effect of pollution on forest health and decline received much attention in the 1980s, it has not been considered to explain the ‘Divergence Problem’ in dendroclimatology; a decoupling of tree growth from rising air temperatures since the 1970s. Here we use physical and biogeochemical measurements of hundreds of living and dead conifers to reconstruct the impact of heavy industrialisation around Norilsk in northern Siberia. Moreover, we develop a forward model with surface irradiance forcing to quantify long‐distance effects of anthropogenic emissions on the functioning and productivity of Siberia’s taiga. Downwind from the world’s most polluted Arctic region, tree mortality rates of up to 100% have destroyed 24,000 km2 boreal forest since the 1960s, coincident with dramatic increases in atmospheric sulphur, copper, and nickel concentrations. In addition to regional ecosystem devastation, we demonstrate how ‘Arctic Dimming’ can explain the circumpolar ‘Divergence Problem’, and discuss implications on the terrestrial carbon cycle.Forest ServiceMinistry of Science and Higher EducationRussian Science Foundatio
Responses of ring widths and maximum densities of Larix gmelinii to climate on contrasting north- and south-facing slopes in central Siberia
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Constitutive resin ducts formation in Pinus sylvestris responds to water availability and temperature in southern Siberia
Constitutive resin ducts (RDs) are a distinctive anatomical trait in the xylem of most conifers, playing a clear defensive role against biotic and abiotic factors. Although resin duct dynamics are well documented in Mediterranean environments, less attention has been dedicated to continental climate. In this study, we evaluated the occurrence and climate response of resin ducts in Pinus sylvestris L. trees in five sites along a 3422 km transect of increasing continentality in the forest-steppe of southern Siberia over the 1966–2016 period. Our results suggest a strong climatic dependence of tree growth and resin duct production under the Siberian continental climate conditions. Tree-ring width and RDs abundance were positively affected by summer precipitation and negatively influenced by temperature and solar radiation, suggesting a link between RDs formation and the water deficit period that limits RW. However, the RDs climate signal was generally weaker, with the strongest climate response occurring later in the season, showing independent signals when the RW effect was removed. The site played a key role as an explanatory factor of the climate response variability. Although no clear pattern was found along the transect, potential differences are due to phenotypic variations between the P. sylvestris populations. Warming-induced drought conditions during the growing season, associated to ongoing climate warming, might affect tree growth and resin ducts production with an increase of this critical defensive structure abundance in conifers growing in the forest-steppe in southern Siberia
Dendroclimatic studies of Larix cajanderi Mayr. in the Omoloy River Basin
This study presents the results of research on the climatic signal of radial growth of Siberian larch (Larix cajanderi Mayr.) in the Omoloy River Basin, (north-eastYakutia). Tree-ring width chronologies were obtained from three sites located in the valley complexes of subarctic tundra and forest-tundra ecotone, with chronologies spanning up to 498 years. Comparative analysis of radial growth dynamics and its statistical parameters indicated similar variability patterns within the study region. Dendroclimatic analysis revealed that the primary limiting factor determining the magnitude of radial growth in Siberianlarch is the air temperature during the first half of the growing season. Increasing temperatures have led to an increased role of precipitation and changes in the strength of growth-temperature correlations, especially in northern sites.This study highlights the potential for dendroclimatic and dendroecological researchin northern Yakutia.</jats:p
Cooling and societal change during the Late Antique Little Ice Age from 536 to around 660 AD
Climatic changes during the first half of the Common Era have been suggested to play a role in societal reorganizations in Europe and Asia. In particular, the sixth century coincides with rising and falling civilizations, pandemics, human migration and political turmoil. Our understanding of the magnitude and spatial extent as well as the possible causes and concurrences of climate change during this period is, however, still limited. Here we use tree-ring chronologies from the Russian Altai and European Alps to reconstruct summer temperatures over the past two millennia. We find an unprecedented, long-lasting and spatially synchronized cooling following a cluster of large volcanic eruptions in 536, 540 and 547 AD (ref.), which was probably sustained by ocean and sea-ice feedbacks, as well as a solar minimum. We thus identify the interval from 536 to about 660 AD as the Late Antique Little Ice Age. Spanning most of the Northern Hemisphere, we suggest that this cold phase be considered as an additional environmental factor contributing to the establishment of the Justinian plague, transformation of the eastern Roman Empire and collapse of the Sasanian Empire, movements out of the Asian steppe and Arabian Peninsula, spread of Slavic-speaking peoples and political upheavals in China. © 2016 Macmillan Publishers Limited. All rights reserved
Prominent role of volcanism in Common Era climate variability and human history
© 2020 Elsevier GmbH Climate reconstructions for the Common Era are compromised by the paucity of annually-resolved and absolutely-dated proxy records prior to medieval times. Where reconstructions are based on combinations of different climate archive types (of varying spatiotemporal resolution, dating uncertainty, record length and predictive skill), it is challenging to estimate past amplitude ranges, disentangle the relative roles of natural and anthropogenic forcing, or probe deeper interrelationships between climate variability and human history. Here, we compile and analyse updated versions of all the existing summer temperature sensitive tree-ring width chronologies from the Northern Hemisphere that span the entire Common Era. We apply a novel ensemble approach to reconstruct extra-tropical summer temperatures from 1 to 2010 CE, and calculate uncertainties at continental to hemispheric scales. Peak warming in the 280s, 990s and 1020s, when volcanic forcing was low, was comparable to modern conditions until 2010 CE. The lowest June–August temperature anomaly in 536 not only marks the beginning of the coldest decade, but also defines the onset of the Late Antique Little Ice Age (LALIA). While prolonged warmth during Roman and medieval times roughly coincides with the tendency towards societal prosperity across much of the North Atlantic/European sector and East Asia, major episodes of volcanically-forced summer cooling often presaged widespread famines, plague outbreaks and political upheavals. Our study reveals a larger amplitude of spatially synchronized summer temperature variation during the first millennium of the Common Era than previously recognised
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Prominent role of volcanism in Common Era climate variability and human history
© 2020 Elsevier GmbH Climate reconstructions for the Common Era are compromised by the paucity of annually-resolved and absolutely-dated proxy records prior to medieval times. Where reconstructions are based on combinations of different climate archive types (of varying spatiotemporal resolution, dating uncertainty, record length and predictive skill), it is challenging to estimate past amplitude ranges, disentangle the relative roles of natural and anthropogenic forcing, or probe deeper interrelationships between climate variability and human history. Here, we compile and analyse updated versions of all the existing summer temperature sensitive tree-ring width chronologies from the Northern Hemisphere that span the entire Common Era. We apply a novel ensemble approach to reconstruct extra-tropical summer temperatures from 1 to 2010 CE, and calculate uncertainties at continental to hemispheric scales. Peak warming in the 280s, 990s and 1020s, when volcanic forcing was low, was comparable to modern conditions until 2010 CE. The lowest June–August temperature anomaly in 536 not only marks the beginning of the coldest decade, but also defines the onset of the Late Antique Little Ice Age (LALIA). While prolonged warmth during Roman and medieval times roughly coincides with the tendency towards societal prosperity across much of the North Atlantic/European sector and East Asia, major episodes of volcanically-forced summer cooling often presaged widespread famines, plague outbreaks and political upheavals. Our study reveals a larger amplitude of spatially synchronized summer temperature variation during the first millennium of the Common Era than previously recognised