| 1. |
- Alakukku, Laura, et al.
(författare)
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Maatalouden ympäristötuen vaikuttavuuden seurantatutkimus (MYTVAS 3) : loppuraportti
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Since 1995, agri-environmental support partly funded by the EU has formed the core of Finland’s agri-environmental policy. This system has had a variety of impacts on the relationship between agriculture and the environment. Today’s agri-environmental support is one of the packages included in the Rural Development Programme for Mainland Finland (2007–2013/2014), which both in itself and through the underlying EU legislation requires monitoring of the impacts of the measures implemented. The study monitoring the impact of the 2nd Finnish agri-environmental scheme (MYTVAS 3), which ran from 2008 to 2013, forms part of this monitoring. The MYTVAS 3 monitoring study was also financed by the Ministry of the Environment. The monitoring study was carried out by a consortium coordinated by MTT Agrifood Research Finland and including the Finnish Environment Institute (SYKE), the University of Helsinki, the Finnish Game and Fisheries Research Institute and the University of Turku.The purpose of the MYTVAS 3 monitoring study was to find out how agri-environmental support and its various measures have affected the state of the environment in agricultural areas, how agri-environmental support has affected the potential for farming and how agri-environmental support should be developed to increase its impact. The monitoring focused on the impacts of agri-environmental support on the nutrient load from agriculture on the waterways and on biodiversity. When evaluating the findings presented, we should remember that while monitoring data shows that something happened, it does not necessarily explain what caused it. It is not always possible to show that particular developments were a specific outcome of the current agri-environmental support system and the implementation of its measures. The delay between a measure and its observed impact is often long, and the cause-and-effect relationships are complicated and partly unknown. Also, other agricultural policy and fluctuations on the market may affect the state of the agricultural environment directly or indirectly.The monitoring data show that agri-environmental support has not had a detrimental impact on the potential for farming. Despite a slight increase in the incidence of weeds, they do not cause problems of the kind that would require amendments to the content of agri-environmental measures. Carbon levels in the surface stratum of arable land seems to be continuing their slow decline, and there is still need for measures to preserve organic material in the soil.Compliance with the fertilisation limits in the agri-environmental support system would seem to have had very little impact on crop quality. Variations in the weight and protein content per hectolitre and per 1,000 seeds were of the same order between 2006 and 2012 as they were between 1995 and 2005. Crop quantities have also not been noticeably affected by compliance with the fertilisation limits. Average crop yields remained stable between 1986 and 2013, and no clearly different crop years were observed in the 2000s. It is possible, however, that the lower fertilisation levels could have lowered crop potential in the years with advantageous weather conditions in the 2000s and that protein contents have been lower in advantageous years.The monitoring data also show that the nutrient load potential of agriculture, measured by nutrient balances, has decreased continuously for nitrogen and particularly for phosphorus. The decrease in the nutrient load potential is due above all to a decrease in the use of synthetic fertilisers. The decline in nitrogen fertilisation has bottomed out in recent years, and low protein levels measured in high crop yield years show that there is no point in further reducing nitrogen fertilisation. Optimising nitrogen fertilisation according to how advantageous the growing season is and effectively using the soluble nitrogen in cattle manure are key measures in achieving reasonable nitrogen balances and good crop quality despite fluctuations in growing season conditions. New crop variants have been found to make more efficient use of nitrogen than old ones, and thus the introduction of new variants should be promoted. Despite the decrease in the nutrient balances, there are indications that nutrient loads in runoff water from domestic animal production sites are becoming an increasing problem. Indeed, the fundamental problem with the nutrient load from agriculture is the diversification of livestock farming and crop farming, which has made it more difficult to use nutrients appropriately. Therefore attention must be paid to measures that both boost the use of nutrients in manure and reduce the levels of nutrients that end up in manure. Based on nutrient load monitoring in the catchment areas of rivers, the phosphorus load per hectare of cropland has decreased in each programme period, being about 80% of the level of the first period (1995–1999) in the third period (2007–2013). Because of the increase in the area of cropland, the nitrogen load on waterways from agriculture continued to grow during the second programme period (2000–2006) but peaked in the third (2007–2013). A similar trend was found in the nitrogen load per hectare of cropland.The most important threat to biodiversity is caused by the development of landscape structure, typically involving a decrease in the number of open or half-open areas excluded from actual cultivation. The consequence of the clearing of margins and ecological islands located in crop fields, drainage measures aimed at increasing arable land and all rationalisation of cultivated areas is the diminishing of exactly those areas that are the most important from the perspective of the biodiversity of the agricultural environment. However, the measure-specific findings in the monitoring study show that biodiversity benefits have been locally achieved where measures have been implemented on a broad enough scale (biodynamic farming, traditional biotopes, wetlands, buffer zones, green fallow / nature management areas). Particular care should therefore be taken that all cultivated land continues to have a sufficient percentage of non-cultivated areas, whether they be natural meadows, nature management areas, biodiversity strips, buffer zones, filter strips, headlands, ecological islands, etc. Including the rather popular nature management areas as a new voluntary measure under basic measures was a significant contribution to biodiversity.Regarding the rural landscape, it may be noted that by visual inspection the area of cropland has remained largely unchanged, at the level of the landscape as a whole it is far more common for the landscape to become more closed than to become more open. This trend was also observed in the visual inspection of traditional biotopes, even if the openness of the meadows monitored largely remained unchanged.The only measures that directly address the reduction of gaseous emissions in the agri-environmental support system are the longterm grass cultivation on peat fields and special aid agreements for slurry injection in cropland. While other measures have indirectly affected gaseous emissions, the impact of agri-environmental support as a whole on reducing gaseous emissions from agriculture has been negligible. In general, we may conclude that the goals, content and support levels of agri-environmental support measures must be increasingly adapted and customised by region, by type of farming and by farm, because both the state of the agricultural environment and the needs of society differ greatly between different types of rural area.
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| 2. |
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Ancient Supercontinents and the Paleogeography of Earth
- 2021
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Samlingsverk (redaktörskap) (refereegranskat)abstract
- Ancient Supercontinents and the Paleogeography of Earth offers a systematic examination of Precambrian cratons and supercontinents. Through detailed maps of drift histories and paleogeography of each continent, this book examines topics related to Earth’s tectonic evolution prior to Pangea, including plate kinematics, orogenic development, and paleoenvironments. Additionally, this book discusses the methodologies used, principally paleomagnetism and tectonostratigraphy, and addresses geophysical topics of mantle dynamics and geodynamo evolution over billions of years. Structured clearly with consistent coverage for Precambrian cratons, this book combines state-of-the-art paleomagnetic and geochronologic data to reconstruct the paleogeography of the Earth in the context of major climatic events such as global glaciations. It is an ideal, up-to>date reference for geoscientists and geographers looking for answers to questions surrounding the tectonic evolution of Earth.
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| 3. |
- Elming, Sten-Åke, et al.
(författare)
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Paleo-Mesoproterozoic Nuna supercycle
- 2021
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Ingår i: Ancient Supercontinents and the Paleogeography of Earth. - : Elsevier. ; , s. 499-548
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Bokkapitel (refereegranskat)abstract
- We review models of the Precambrian supercontinent Nuna (c.1.80–1.20 Ga) and present a new model of the Nuna life-cycle. We explore the option where Amazonia−West Africa and Congo−São Francisco cratons were not a part of Nuna but form a cluster of cratons named Atlantica. Nuna was finally assembled at c.1.65 Ga, encompassing Laurentia, Baltica, Siberia, proto-Australia, North China, and India. The break up of Nuna is here suggested to have started at c.1.3 Ga with Australian cratons moving away from Laurentia. Varying drift rates and length between coeval poles from separate cratons support the operation of modern style plate tectonics during the Nuna supercycle. Moreover, if there was no link between Nuna and the Atlantica cratons, the size of Nuna might not meet the criteria for a supercontinent, but should be regarded as a huge landmass.
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| 4. |
- Evans, David A.D., et al.
(författare)
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An expanding list of reliable paleomagnetic poles for Precambrian tectonic reconstructions
- 2021
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Ingår i: Ancient Supercontinents and the Paleogeography of Earth. - : Elsevier. ; , s. 605-639
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Bokkapitel (refereegranskat)abstract
- We present a compilation of reliable Precambrian paleomagnetic poles from three successive international workshops (in years 2009, 2014, 2017), comprising paleomagnetists specializing in Precambrian tectonic reconstructions. The working groups compiled lists of two global classes of poles, published through the end of 2017. “Grade-A” results are judged to provide essential constraints on tectonic reconstructions; “Grade-B” poles are judged to be suggestive of high-quality, but not yet demonstrated to be primary, or perhaps lacking precise geochronologic or other constraints. Our catalog documents a resurgence of high-quality data acquisition in recent years, and highlights specific cratons and time intervals that are most lacking in the data needed to reconstruct those blocks through supercontinental cycles.
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| 5. |
- Gong, Zheng, et al.
(författare)
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Paleomagnetism, magnetic anisotropy and U-Pb baddeleyite geochronology of the early Neoproterozoic Blekinge-Dalarna dolerite dykes, Sweden
- 2018
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Ingår i: Precambrian Research. - : Elsevier BV. - 0301-9268 .- 1872-7433. ; 317, s. 14-32
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Tidskriftsartikel (refereegranskat)abstract
- Paleogeographic proximity of Baltica and Laurentia in the supercontinent Rodinia has been widely accepted. However, robust paleomagnetic poles are still scarce, hampering quantitative tests of proposed relative positions of the two cratons. A recent paleomagnetic study of the early Neoproterozoic Blekinge-Dalarna dolerite (BDD) dykes in Sweden provided a 946–935 Ma key pole for Baltica, but earlier studies on other BDD dykes discerned large variances in paleomagnetic directions that appeared to indicate more complicated motion of Baltica, or alternatively, unusual geodynamo behavior in early Neoproterozoic time. We present combined paleomagnetic, rock magnetic, magnetic fabric and geochronological studies on BDD dykes in the Dalarna region, southern Sweden. Positive baked-contact and paleosecular variation tests support the reliability of the 951–935 Ma key pole (Plat = −2.6°N, Plon = 239.6°E, A95 = 5.8° N = 12 dykes); and the ancient magnetic field was likely a stable geocentric axial dipole at that time, based on a positive reversal test. Detailed analysis of the 947 Ma Nornäs dyke, one of the dykes previously showing anomalous directions, suggests a partial viscous remagnetization. Therefore, the observed large variances in nearly coeval BDD dykes are suspected to result from present-day overprints that were not adequately removed in earlier studies. In addition, we obtained a 971 Ma virtual geomagnetic pole (Plat = −27.0°N, Plon = 230.4°E, A95 = 14.9° N = 4 dykes) for Baltica. Comparing similar-aged poles from Laurentia, we suggest that Baltica and Laurentia drifted together from high to low latitude between 970–960 Ma and 950–935 Ma, and returned back to high latitude by 920–870 Ma. In this scenario, the apparent polar wander paths of Baltica and Laurentia may be more complicated than the previously proposed, solitary Sveconorwegian and Grenville loops. The new U-Pb baddeleyite ages do not support BDD dykes as a giant circumferential swarm generated by a mantle plume, and the prolonged timespan of dyke intrusion is likely associated with the plate boundary forces as causing gravitational extension at the waning stage of the Sveconorwegian orogeny.
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| 6. |
- Luttinen, Arto, et al.
(författare)
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Age, geochemistry, and origin of the mid-Proterozoic Häme mafic dyke swarm, southern Finland
- 2022
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Ingår i: Bulletin of the Geological Society of Finland. - : The Geological Society of Finland. - 0367-5211 .- 1799-4632. ; 94, s. 75-101
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Tidskriftsartikel (refereegranskat)abstract
- We have reappraised the age and composition of the mid-Proterozoic Flame dyke swarm in southern Finland. The dominant trend of the dykes of this swarm is NW to WNW. Petrographic observations and geochemical data indicate uniform, tholeiitic low-Mg parental magmas for all of the dykes. Nevertheless, the variability in incompatible trace element ratios, such as Zr/Y and La/Nb, provides evidence of changing mantle melting conditions and variable crustal contamination. Our ID-TIMS 207Pb/206Pb ages for four low-Zr/Y-type dykes indicate emplacement at 1639 ± 3 Ma, whereas the most reliable previously published ages suggest emplacement of the high-Zr/Y-type dykes at 1642 ± 2 Ma. We propose that the Hame dyke swarm, and possibly also the other mid-Proterozoic mafic dyke swarms in southern Finland, records a progressive decrease in Zr/Y values due to magma generation under developing areas of thinned lithosphere. We consider that the formation of mafic magmas was most probably associated with the upwelling of hot convective mantle in an extensional setting possibly related to the nearby Gothian orogeny. The generation of tholeiitic magmas below continental lithosphere was probably promoted by the elevated mantle temperature underneath the Nuna supercontinent. We speculate that the origin of most of the relatively small mid-Proterozoic mafic dyke swarms, anorthosites, rapakivi granites, and associated rocks found across Nuna was similarly triggered by extensional plate tectonics and the convection of anomalous hot upper mantle below the supercontinent.
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| 7. |
- Meert, Joseph G., et al.
(författare)
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The magnificent seven : A proposal for modest revision of the Van der Voo (1990) quality index
- 2020
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Ingår i: Tectonophysics. - : Elsevier. - 0040-1951 .- 1879-3266. ; 790
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Tidskriftsartikel (refereegranskat)abstract
- Thirty years ago, Rob Van der Voo proposed an elegant and simple system for evaluating the quality of paleomagnetic data. As a second-year Ph.D. student, the lead author remembers Rob waxing philosophical about the need to have an appropriate, but not overly rigid evaluation system. The end result was a 7-point system that assigned a (1) or (0) for any paleomagnetic result based on objective criteria. The goal was never to reject or blindly accept any particular result, but merely to indicate the degree of quality for any paleomagnetic pole. At the time, the global paleomagnetic database was burgeoning and it was deemed useful to rank older paleomagnetic results with the newer data being developed in modern laboratories. Van der Voo's, 1990 paper launched a silent revolution in paleomagnetism. Researchers began to evaluate their data against those seven criteria with the anticipation that reviewers would be similarly critical.Today, paleomagnetism is a mature science. Our methods, analyses, and results are more sophisticated than they were 30 years ago. Therefore, we feel it is appropriate to revisit the Van der Voo (1990) criteria in light of those developments. We hope to honor the intention of the original paper by keeping the criteria simple and easy to evaluate while also acknowledging the advances in science. This paper aims to update the criteria and modernize the process. We base our changes on advances in paleomagnetism and geochronology with a faithful adherence to the simplicity of the original publication. We offer the “Reliability” or “R” index as the next generation of the Van der Voo “Quality” or “Q” index. The new R-criteria evaluate seven different information items for each paleomagnetic pole including age, statistical requirements, identification of magnetic carriers, field tests, structural integrity, presence of reversals and an evaluation for possible remagnetization.
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| 8. |
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| 9. |
- Pesonen, Lauri J., et al.
(författare)
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Precambrian supercontinents and supercycles—an overview
- 2021
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Ingår i: Ancient Supercontinents and the Paleogeography of Earth. - : Elsevier. ; , s. 1-50
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Bokkapitel (refereegranskat)abstract
- There is ample evidence that supercontinent cycles on Earth have been operating since the Late Paleoproterozoic. Evidence for the supercontinent cyclicity arises from multidisciplinary observations from geology, geochronology, geophysics (e.g., paleomagnetism, seismology, heat flow), isotope geology, and geochemistry. This overview summarizes current views of Precambrian supercontinent episodicity or cyclicity. In addition, paleogeographic reconstructions based on global key paleomagnetic poles and kinematic models of Paleo-Mesoproterozoic Nuna supercycle, Meso-Neoproterozoic Rodinia supercycle, and the Phanerozoic Gondwana/Pangea supercycle are explored. The lifecycle of supercontinents is tested by geological, geophysical, and geochemical data coupled with secular evolution trends of Earth. Results suggest that (1) supercontinent cyclicity has a characteristic (quasi-) period of ~700–500 million years, supported by planetary secular evolutionary trends, but other periods are also present; (2) supercontinents Nuna, Rodinia, and Gondwana/Pangea have different configurations and secular evolutionary trends possibly due to different tectonic styles of assembly; (3) globally averaged plate velocity during the Precambrian reveals a wave-like pattern with peaks and lows corresponding with features in several secular evolution indices including the distribution of U−Pb ages, passive margins, metamorphic events, tectonic proxies, and magmatic activity; (4) the data suggest three tectonomagmatic lulls during the Proterozoic, but the proposed Mesoproterozoic quiescent period, coined as “boring billion” years of Earth history (1.8–0.8 Ga) appears to be seen mainly by atmospheric and biospheric data rather than tectonomagmatic activity; and (5) tectonic processes driving supercontinent cyclicity are interactive, with feedbacks from all six spheres of the Earth—the geosphere, cryosphere, hydrosphere, biosphere, atmosphere, and magnetosphere.
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| 10. |
- Pesonen, Lauri J., et al.
(författare)
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Preface
- 2021
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Ingår i: Ancient Supercontinents and the Paleogeography of Earth. - : Elsevier. ; , s. xv-xvi
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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