Holocene pollen records from the central Arctic Foothills, northern Alaska: testing the role of substrate in the response of tundra to climate change

1   To explore the role of edaphic controls in the response of arctic tundra to climate change, we analysed Holocene pollen records from lakes in northern Alaska located on glaciated surfaces with contrasting soil texture, topography and tundra communities. Using indicator taxa, pollen accumulation rates (PARs) and multivariate comparison of fossil and modern pollen assemblages, we reconstructed the vegetational changes at Upper Capsule Lake (Sagavanirktok surface) and Red Green Lake (Itkillik II surface) in response to increased effective moisture between the early and middle Holocene. 2   In the Red Green record, low PARs and the continuous presence of taxa indicative of prostrate-shrub tundra (PST; Equisetum , Polypodiaceae, Thalictrum and Rosaceae) indicate that the vegetation resembled PST throughout the Holocene. During the warm, dry early Holocene (11 300–10 000 cal years BP), PST also occurred on Sagavanirktok surfaces, as evidenced by PST indicators (Bryidae, Polypodiaceae, Equisetum and Rosaceae) in this interval of the Upper Capsule record. However, PARs increased, suggesting increased vegetation cover, PST taxa declined and taxa indicative of dwarf-shrub tundra (DST; Rubus chamaemorus and Lycopodium annotinum ) increased between 10 000 and 7500 cal years BP. 3   We hypothesize that between the early and middle Holocene the fine-textured soils and smooth topography of Sagavanirktok surfaces led to increased soil moisture, greater vegetation cover, permafrost aggradation, anoxic and acidic soil conditions, slower decomposition and the development of a thick organic layer. In contrast, soil moisture remained low on the better-drained Itkillik II surface, and vegetational changes were minor. 4   Landscape-scale substrate variations have an effect on how tundra responds to climate change, suggesting that the response of arctic ecosystems to future variability may be spatially heterogeneous. Journal of Ecology (2003) 91 , 1034–1048Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73204/1/j.1365-2745.2003.00833.x.pd

Past Arctic aliens have passed away, current ones may stay

Published version. Source at http://doi.org/10.1007/s10530-015-0937-9.Increased human activity and climate change are expected to increase the numbers and impact of alien species in the Arctic, but knowledge of alien species is poor in most Arctic regions. Through field investigations over the last 10 years, and review of alien vascular plant records for the high Arctic Archipelago Svalbard over the past 130 years, we explored long term trends in persistence and phenology. In total, 448 observations of 105 taxa have been recorded from 28 sites. Recent surveys at 18 of these sites revealed that alien species had disappeared at half of them. Investigations at a further 49 sites characterised by former human activity and/or current tourist landing sites did not reveal any alien species. Patterns of alien species distribution suggest that greater alien species richness is more likely to be aligned with ongoing human inhabitation than sites of transient use. The probability of an alien species being in a more advanced phenological stage increased with higher mean July temperatures. As higher mean July temperatures are positively correlated with more recent year, the latter finding suggests a clear warming effect on the increased reproductive potential of alien plants, and thus an increased potential for spread in Svalbard. Given that both human activity and temperatures are expected to increase in the future, there is need to respond in policy and action to reduce the potential for further alien species introduction and spread in the Arctic

Shrub growth and expansion in the Arctic tundra: an assessment of controlling factors using an evidence-based approach

Woody shrubs have increased in biomass and expanded into new areas throughout the Pan-Arctic tundra biome in recent decades, which has been linked to a biome-wide observed increase in productivity. Experimental, observational, and socio-ecological research suggests that air temperature—and to a lesser degree precipitation—trends have been the predominant drivers of this change. However, a progressive decoupling of these drivers from Arctic vegetation productivity has been reported, and since 2010, vegetation productivity has also been declining. We created a protocol to (a) identify the suite of controls that may be operating on shrub growth and expansion, and (b) characterise the evidence base for controls on Arctic shrub growth and expansion. We found evidence for a suite of 23 proximal controls that operate directly on shrub growth and expansion; the evidence base focused predominantly on just four controls (air temperature, soil moisture, herbivory, and snow dynamics). 65% of evidence was generated in the warmest tundra climes, while 24% was from only one of 28 floristic sectors. Temporal limitations beyond 10 years existed for most controls, while the use of space-for-time approaches was high, with 14% of the evidence derived via experimental approaches. The findings suggest the current evidence base is not sufficiently robust or comprehensive at present to answer key questions of Pan-Arctic shrub change. We suggest future directions that could strengthen the evidence, and lead to an understanding of the key mechanisms driving changes in Arctic shrub environments

Biological soil crusts of Arctic Svalbard and of Livingston Island, Antarctica

Biological soil crusts (BSCs) occur in arid and semi-arid regions worldwide including the Polar Regions. They are important ecosystem engineers, and their composition and areal coverage should be understood before assessing key current functional questions such as their role in biogeochemical nutrient cycles and possible climate change scenarios. Our aim was to investigate the variability of BSCs from Arctic Svalbard and the Antarctic Island, Livingston, using vegetation surveys based on classification by functional group. An additional aim was to describe the structure of BSCs and represent a classification system that can be used in future studies to provide a fast and efficient way to define vegetation type and areal coverage. Firstly, this study demonstrates huge areas occupied by BSCs in Arctic Svalbard, with up to 90 % of soil surface covered, dominated by bryophytes and cyanobacteria, and showing an unexpectedly high variability in many areas. Livingston Island has lower percentage coverage, up to 55 %, but is dominated by lichens. Our findings show that both Polar Regions have varied BSC coverage, within the sites and between them, especially considering their harsh climates and latitudinal positions. Secondly, we have classified the BSCs of both areas into a system that describes the dominant functional groups and local geography, creating a simple scheme that allows easy identification of the prevailing vegetation type. Our results represent the first contribution to the description of BSCs based on their functional group composition in Polar Regions

Propuesta de alternativa para la pacificación del tránsito frente a la sede 13 (calle 47 entre las carreras 13 y 14) de la Universidad Católica de Colombia

Trabajo de investigaciónEste proyecto busca generar espacios seguros para los peatones, con el fin de reducir los accidentes de tránsito, que al año 2018 según datos del IDECA, en la intersección de la carrera 13 con calle 47 se establecieron en 13. Gracias a las diferentes alternativas de pacificación del tránsito que se encuentran disponibles en la actualidad, se ha logrado disminuir los accidentes de tránsito, es por esto, que en esta investigación se propone diseñar un paso a nivel sobre la calle 47 entre Carreras 13 y 14, con el fin de ampliar las vías peatonales basándose en la cartilla de andenes para Bogotá de la Secretaria Distrital De Planeación y el Decreto 327 del 2004. De igual manera se verifico el nivel de servicio actual del andén del costado norte y el nivel de servicio que se prestará con las alternativas propuestas, finalmente se llevó a cabo una simulación de la condición actual de movilidad del corredor con el fin de determinar cómo se comportara el corredor con la alternativa planteada en la investigación. Todas las conclusiones de la investigación se basan en mejorar las condiciones de movilidad peatonal con el fin de conseguir una movilidad más segura y que no represente conflicto entre los diferentes actores viales del corredor.INTRODUCCIÓN 1. ANTECEDENTES Y JUSTIFICACIÓN 2. PLANTEAMIENTO Y FORMULACIÓN DEL PROBLEMA 3. OBJETIVOS 4. MARCO DE REFERENCIA 5. ALCANCES Y LIMITACIONES 6. METODOLOGÍA 7. VISITA DE CAMPO 8. INSPECCIÓN VISUAL DE SEGURIDAD 9. ESTUDIO DE LA ALTERNATIVA 10. DISEÑO DE LA ALTERNATIVA 11. MODELACIÓN EN PTV VISSIM 2020 VERSIÓN EDUCATIVA 12. CONCLUSIONES BIBLIOGRAFÍA ANEXOSPregradoIngeniero Civi

Using value of statistical life for the ex ante evaluation of transport policy options: a discussion based on ethical theory

This paper aims to discuss a number of questions that are highly important for the ex ante evaluation of the safety impacts of transport policy options, from the perspective of ethical theory: (1) Is it morally OK to express prevention on acceptance of fatalities or risks in monetary terms? (2) How useful is the concept of the value of a statistical life (VOSL) for ex ante evaluations of transport policy options? (3) What are the pros and cons of pricing protection of lives or prevention of risks in ex ante evaluations? (4) Which methods are available for expressing (protection of) human lives in monetary terms, and what are the main related methodological discussions? (5) Are all safety-related costs generally included in ex ante evaluations of the safety impacts of transport policy options, and if not: what is the relevance of excluded costs categories from an ethical perspective? (6) How important is the distribution of safety effects from an ethical perspective? The answer to the first question highly depends on the ethical theory that is used. With respect to question 2 we think that the VOSL is a useful concept, but that its application is not straightforward, for several reasons. Thirdly we think that probably pricing safety improves the quality of decision making, but to the best of our knowledge there is no research to underpin this expectation. The answer to question 4 is that several methods exist to estimate the value of a statistical life (VOSL), willingness-to-pay (WTP) methods being the most common category of methods. However, several methodological issues arise that make estimates of VOSL less straightforward. With respect to question 5 we conclude that behaviour-related avoidance costs are often overlooked and that these costs are relevant from an ethical perspective because the freedom to move and the freedom to participate in activities are challenged. Finally the answer to question 6 is that from an ethical perspective, in terms of the evaluation of policy measures, it might matter which groups of the population are the victims of the transport system, or are at risk. Egalitarian theories as well as sufficientarianism are useful theories to discuss distribution effects. Different theories conclude differently. © 2012 The Author(s)