Browsing by Subject "REGIMES"

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  • Vihma, Timo; Graversen, Rune G.; Chen, Linling; Handorf, Dörthe; Skific, Natasa; Francis, Jennifer A.; Tyrrell, Nicholas L; Hall, Richard; Hanna, Edward; Uotila, Petteri; Dethloff, Klaus; Karpechko, Alexey; Björnsson, Halldor; Overland, James E. (2020)
    We investigate factors influencing European winter (DJFM) air temperatures for the period 1979-2015 with the focus on changes during the recent period of rapid Arctic warming (1998-2015). We employ meteorological reanalyses analysed with a combination of correlation analysis, two pattern clustering techniques, and back-trajectory airmass identification. In all five selected European regions, severe cold winter events lasting at least 4 days are significantly correlated with warm Arctic episodes. Relationships during opposite conditions of warm Europe/cold Arctic are also significant. Correlations have become consistently stronger since 1998. Large-scale pattern analysis reveals that cold spells are associated with the negative phase of the North Atlantic Oscillation (NAO-) and the positive phase of the Scandinavian (SCA+) pattern, which in turn are correlated with the divergence of dry-static energy transport. Warm European extremes are associated with opposite phases of these patterns and the convergence of latent heat transport. Airmass trajectory analysis is consistent with these findings, as airmasses associated with extreme cold events typically originate over continents, while warm events tend to occur with prevailing maritime airmasses. Despite Arctic-wide warming, significant cooling has occurred in northeastern Europe owing to a decrease in adiabatic subsidence heating in airmasses arriving from the southeast, along with increased occurrence of circulation patterns favouring low temperature advection. These dynamic effects dominated over the increased mean temperature of most circulation patterns. Lagged correlation analysis reveals that SCA- and NAO+ are typically preceded by cold Arctic anomalies during the previous 2-3 months, which may aid seasonal forecasting.
  • Aakala, Tuomas (2018)
    Wildfires virtually disappeared from the Fennoscandian forests in the 20th century, but have left persistent legacies in forest structure. Here, I reconstructed past fires in three northern boreal landscapes (each 2 km x 2 km) from fire scars, and described the fire regime for the past 300 years. The average fire cycles (1700-1999) were 72 and 156 years in Pinus sylvestris-dominated landscapes, and 579 years in a Picea abies-dominated landscape. At the site level, the number of fires was clearly related to soil hydraulic properties. Age structures from 1800 live and dead trees showed strong cohorts associated with large fires in two of the landscapes. Although tree growth and regeneration in sub-arctic regions are considered highly climate-sensitive, fires have been a major driver of forest dynamics in these areas. Continued absence of fires will lead to considerable changes in the forest structure and species composition in the future.
  • Seidl, Rupert; Honkaniemi, Juha; Aakala, Tuomas; Aleinikov, Alexey; Angelstam, Per; Bouchard, Mathieu; Boulanger, Yan; Burton, Philip J.; De Grandpre, Louis; Gauthier, Sylvie; Hansen, Winslow D.; Jepsen, Jane U.; Jogiste, Kalev; Kneeshaw, Daniel D.; Kuuluvainen, Timo; Lisitsyna, Olga; Makoto, Kobayashi; Mori, Akira S.; Pureswaran, Deepa S.; Shorohova, Ekaterina; Shubnitsina, Elena; Taylor, Anthony R.; Vladimirova, Nadezhda; Vodde, Floortje; Senf, Cornelius (2020)
    Disturbance regimes are changing in forests across the world in response to global climate change. Despite the profound impacts of disturbances on ecosystem services and biodiversity, assessments of disturbances at the global scale remain scarce. Here, we analyzed natural disturbances in boreal and temperate forest ecosystems for the period 2001-2014, aiming to 1) quantify their within- and between-biome variation and 2) compare the climate sensitivity of disturbances across biomes. We studied 103 unmanaged forest landscapes with a total land area of 28.2 x 10(6) ha, distributed across five continents. A consistent and comprehensive quantification of disturbances was derived by combining satellite-based disturbance maps with local expert knowledge of disturbance agents. We used Gaussian finite mixture models to identify clusters of landscapes with similar disturbance activity as indicated by the percent forest area disturbed as well as the size, edge density and perimeter-area-ratio of disturbed patches. The climate sensitivity of disturbances was analyzed using Bayesian generalized linear mixed effect models and a globally consistent climate dataset. Within-biome variation in natural disturbances was high in both boreal and temperate biomes, and disturbance patterns did not vary systematically with latitude or biome. The emergent clusters of disturbance activity in the boreal zone were similar to those in the temperate zone, but boreal landscapes were more likely to experience high disturbance activity than their temperate counterparts. Across both biomes high disturbance activity was particularly associated with wildfire, and was consistently linked to years with warmer and drier than average conditions. Natural disturbances are a key driver of variability in boreal and temperate forest ecosystems, with high similarity in the disturbance patterns between both biomes. The universally high climate sensitivity of disturbances across boreal and temperate ecosystems indicates that future climate change could substantially increase disturbance activity.
  • Aakala, Tuomas; Pasanen, Leena; Helama, Samuli; Vakkari, Ville; Drobyshev, Igor; Seppa, Heikki; Kuuluvainen, Timo; Stivrins, Normunds; Wallenius, Tuomo; Vasander, Harri; Holmstrom, Lasse (2018)
    Forest fires are a key disturbance in boreal forests, and characteristics of fire regimes are among the most important factors explaining the variation in forest structure and species composition. The occurrence of fire is connected with climate, but earlier, mostly local-scale studies in the northern European boreal forests have provided little insight into fire-climate relationship before the modern fire suppression period. Here, we compiled annually resolved fire history, temperature, and precipitation reconstructions from eastern Fennoscandia from the mid-16th century to the end of the 19th century, a period of strong human influence on fires. We used synchrony of fires over the network of 25 fire history reconstructions as a measure of climatic forcing on fires. We examined the relationship between fire occurrence and climate (summer temperature, precipitation, and a drought index summarizing the influence of variability in temperature and precipitation) across temporal scales, using a scale space multiresolution correlation approach and Bayesian inference that accounts for the annually varying uncertainties in climate reconstructions. At the annual scale, fires were synchronized during summers with low precipitation, and most clearly during drought summers. A scale-derivative analysis revealed that fire synchrony and climate varied at similar, roughly decadal scales. Climatic variables and fire synchrony showed varying correlation strength and credibility, depending on the climate variable and the time period. In particular, precipitation emerged as a credible determinant of fire synchrony also at these time scales, despite the large uncertainties in precipitation reconstruction. The findings explain why fire occurrence can be high during cold periods (such as from the mid-17th to early-18th century), and stresses the notion that future fire frequency will likely depend to a greater extent on changes in precipitation than temperature alone. We showed, for the first time, the importance of climate as a decadal-scale driver of forest fires in the European boreal forests, discernible even during a period of strong human influence on fire occurrence. The fire regime responded both to anomalously dry summers, but also to decadal-scale climate changes, demonstrating how climatic variability has shaped the disturbance regimes in the northern European boreal forests over various time scales.
  • Zilitinkevich, S. S.; Esau, I.; Kleeorin, N.; Rogachevskii, I.; Kouznetsov, R. D. (2010)
  • Limpens, Juul; Fijen, Thijs P. M.; Keizer, Iris; Meijer, Johan; Olsthoorn, Fanny; Pereira, Ana; Postma, Roel; Suyker, Mariette; Vasander, Harri; Holmgren, Milena (2021)
    Arctic and subarctic ecosystems are changing rapidly in species composition and functioning as they warm twice as fast as the global average. It has been suggested that tree-less boreal landscapes may shift abruptly to tree-dominated states as climate warms. Yet, we insufficiently understand the conditions and mechanisms underlying tree establishment in the subarctic and arctic regions to anticipate how climate change may further affect ecosystem structure and functioning. We conducted a field experiment to assess the role of permafrost presence, micro-topography and shrub canopy on tree establishment in almost tree-less subarctic peatlands of northern Finland. We introduced seeds and seedlings of four tree-line species and monitored seedling survival and environmental conditions for six growing seasons. Our results show that once seedlings have emerged, the absence of permafrost can enhance early tree seedling survival, but shrub cover is the most important driver of subsequent tree seedling survival in subarctic peatlands. Tree seedling survival was twice as high under an intact shrub canopy than in open conditions after shrub canopy removal. Under unclipped control conditions, seedling survival was positively associated with dense shrub canopies for half of the tree species studied. These strong positive interactions between shrubs and trees may facilitate the transition from today's treeless subarctic landscapes towards tree-dominated states. Our results suggest that climate warming may accelerate this vegetation shift as permafrost is lost, and shrubs further expand across the subarctic.
  • Häkkinen, Esko (2020)
    Émile Durkheim known among other things for his pioneering sociology of criminal law was also a corporatist theorist and can be interpreted as a predecessor for an institutionalist approach that has recently gained popularity in comparative criminal justice. Durkheim suggested an inverse relationship between the intensities of ‘repressive’ regulation and ‘restitutive’ welfare state regulation. Contemporary institutionalist research has arrived at the same conclusion, but the connection between Durkheim’s theory and the empirical observations of modern comparative research has gone largely unnoticed in both legal scholarship and sociology. Correcting this omission might prove useful for substantive theory: Apart from welfare state strength, neo-institutionalist research has also associated lenient criminal law with corporatist political economy and consensus democracy. Durkheim’s political sociology proposes an answer for the interrelationship between these factors. Durkheim considered social corporatism a democratic institution and as such a precondition for a democracy capable of building the collective restitutive regulation that could alleviate society’s reliance on punitive justice as a basis for social cohesion.
  • Charitsis, Vassilis; Fyrberg Yngfalk, Anna; Skålén, Per (2019)
    While previous critical marketing research on co-creation has focused on how consumers' cognitive and social abilities are governed, this article focuses on how firms' marketing strategies attempt to govern every aspect of consumers' lives. By drawing on a biopolitical framework and a study of Nike+, a marketing system for runners which Nike has developed around its self-tracking devices, three biopolitical marketing dimensions were identified: the gamification of the running experience, the transformation of running into a competitive activity and the conversion of running into a social activity. In identifying these marketing dimensions, the study demonstrates how self-tracking affordances are deployed in the development of a biopolitical marketing environment that tames, captures and appropriates value from different aspects of consumers' lives, including - and combining - their social behaviours, cognitive capacities and bodily conducts. This article contributes to critical studies of value co-creation by focusing on the tamed self-tracking body as a resource for value creation, but also by demonstrating that consumers engage, through cognitive labour, in the production of the biopolitical environment that leads to their exploitation.