Migration Delays Research Articles

Migratory passage and run size of American Shad and river herring in the Raritan River, New Jersey, USA

AbstractObjectiveRestoration of many populations of anadromous American Shad Alosa sapidissima and river herring (Alewife A. pseudoharengus and Blueback Herring A. aestivalis) has been hampered by the presence of barriers to their spawning migrations and insufficient monitoring of run size. Here, we describe results of a 10‐year (2012–2021) study of American Shad and river herring passage at the Island Farm Weir (IFW), the downstream‐most migration barrier on the Raritan River, New Jersey, United States.MethodsWe used passive integrated transponder tags applied to fish that were captured and released downstream of the IFW to estimate passage rates and migration delays associated with upstream movements through an antenna array on a vertical slot fishway within the weir. By combining estimated passage rates with video monitoring of the total numbers of American Shad and river herring transiting the fishway, we estimated the annual run size below the weir.ResultResults suggest that the fishway on the IFW is moderately effective for American Shad (passage rate = 41%; 95% credible interval [CI] = 21–61%) but ineffective for the smaller‐bodied river herring (passage rate = 0.5%, 95% CI = 0–2%; fallback‐adjusted passage rate = 1.1%, 95% CI = 0.0–4.5%). The IFW may have also delayed the spawning migrations of those fish that did pass, with total passage times ranging from 0.4 to 20.9 days (mean ± standard deviation = 8.2 ± 5.3 days) for American Shad and 15.0 days for the one river herring that passed within the same year that it was tagged. Run size estimates during the study period ranged from 103 to 2624 individuals for American Shad and from 1486 to 53,334 for river herring.ConclusionRestoration of these species in the Raritan River will likely require removal of the IFW or replacement of its current fish passage device with one that increases the passage rates of alosines.

Survival implications of diversion entrainment for out‐migrating juvenile Chinook Salmon and steelhead

AbstractObjectiveEfforts to ameliorate the negative effects of diversion dams on aquatic species of concern are important in rivers where water withdrawal supports agricultural economies, and they are likely to become increasingly important with impending climate change. A multi‐year study was conducted to evaluate the survival consequences of diversion dam passage for juvenile Chinook Salmon Oncorhynchus tshawytscha and steelhead O. mykiss in the highly managed Yakima River, Washington. Canal entrainment and passage were evaluated at four diversion dams in the lower Yakima River where seaward‐migrating juvenile salmon and steelhead either pass dams via spill bays or enter canals with downstream fish‐screening facilities designed to collect entrained fish and return them to the main‐stem river.MethodsWe used acoustic telemetry to monitor the downstream migration behavior of 4403 juvenile Chinook Salmon and steelhead during 2018–2021.ResultPercent entrainment into canals was substantial (6–59%) at three of the four diversion dams studied, and entrainment probability was positively associated with the proportion of streamflow diverted into canals. Survival probability estimates for groups of tagged fish that were entrained into canals were lower than survival probability estimates for tagged fish that passed through spill bays on the dams. Absolute differences in survival probabilities between routes ranged from 0.099 to 0.369, demonstrating that canal entrainment reduced the survival of outmigrating juvenile Chinook Salmon and steelhead. We also found that entrainment resulted in migration delays, which could further affect survival because fish are increasingly exposed to predation and decreased water quality as water temperature increases throughout the migration season.ConclusionCanal entrainment resulted in increased mortality and travel time through the study area, highlighting the need to limit the entrainment of juvenile salmon and steelhead at diversion dams in rivers where salmon recovery is important.

Specific prostaglandins are produced in the migratory cells and the surrounding substrate to promote Drosophila border cell migration.

Introduction: A key regulator of collective cell migration is prostaglandin (PG) signaling. However, it remains largely unclear whether PGs act within the migratory cells or their microenvironment to promote migration. Here we use Drosophila border cell migration as a model to uncover the cell-specific roles of two PGs in collective migration. The border cells undergo a collective and invasive migration between the nurse cells; thus, the nurse cells are the substrate and microenvironment for the border cells. Prior work found PG signaling is required for on-time border cell migration and cluster cohesion. Methods: Confocal microscopy and quantitative image analyses of available mutant alleles and RNAi lines were used to define the roles of the PGE2 and PGF2α synthases in border cell migration. Results: We find that the PGE2 synthase cPGES is required in the substrate, while the PGF2α synthase Akr1B is required in the border cells for on-time migration. Akr1B acts in both the border cells and their substrate to regulate cluster cohesion. One means by which Akr1B may regulate border cell migration and/or cluster cohesion is by promoting integrin-based adhesions. Additionally, Akr1B limits myosin activity, and thereby cellular stiffness, in the border cells, whereas cPGES limits myosin activity in both the border cells and their substrate. Decreasing myosin activity overcomes the migration delays in both akr1B and cPGES mutants, indicating the changes in cellular stiffness contribute to the migration defects. Discussion: Together these data reveal that two PGs, PGE2 and PGF2α, produced in different locations, play key roles in promoting border cell migration. These PGs likely have similar migratory versus microenvironment roles in other collective cell migrations.

Time to Treatment Initiation and HIV Viral Suppression in People Diagnosed With HIV-1 During COVID-19 Pandemic in Ex-Aquitaine, France (ANRS CO3 AQUIVIH-NA Cohort-QuAliCOV Study).

The COVID-19 pandemic's impact on initiation and effectiveness of antiretroviral therapy (ART) in people diagnosed with HIV remains unclear. We evaluated critical delays in HIV care in people diagnosed before and during the pandemic in ex-Aquitaine, France. We considered adults diagnosed with HIV-1 in 2018-2021 and enrolled in the ANRS CO3 AQUIVIH-NA and followed them until October 10, 2022 for those diagnosed during the pandemic (April 01, 2020-December 31, 2021) and until March 31, 2020 for historical controls. We compared their characteristics at inclusion and the median time between diagnosis and ART initiation, ART initiation and viral suppression, and diagnosis and virologic, suppression (effective management). Eighty-three individuals were diagnosed during the pandemic versus 188 during the prepandemic period. Median follow-up was 549 (interquartile range: 329-713) days. Populations were similar in sex, age, HIV acquisition mode, hospital type, and clinical characteristics at diagnosis; however, fewer were foreign-born during the pandemic (15.7% versus 33.5%, P = 0.003). The probability of ART initiation, therapeutic success, and effective management was higher in people living with HIV (PLWH) diagnosed during the pandemic in adjusted analyses (hazard ratio [HR]: 2.0; 95% CI: 1.5 to 2.7; HR: 1.7; 95% CI: 1.2 to 2.3; HR: 1.8; 95% CI: 1.3 to 2.6, respectively). Those diagnosed during the pandemic were 2.3 (95% CI: 1.2 to 4.1) times more likely to be virologically suppressed within six months of diagnosis compared with historical controls. Pandemic-related reorganizations may have resulted in newly diagnosed PLWH being prioritized; however, the lower proportion of foreign-born PLWH diagnosed during the pandemic period, likely because of reduced migration and potential delays in diagnosis, may contribute to these preliminary findings.

MSM: Mobility-Aware Service Migration for Seamless Provision: A Data-Driven Approach

Mobile Edge Computing (MEC) is a promising approach to support high-quality time-sensitive applications. With the increasing number of mobile devices, achieving efficient service migration management has become non-trivial in MEC. In addition, the service migration issue is difficult to be solved in real-time due to user mobility and dynamic network conditions. In this paper, we investigate the mobility-aware service migration problem in MEC by introducing a data-driven framework. Firstly, service migration is formulated as an optimization problem for minimizing the long-term system delay that consists of computing, communication, and migration delays. Secondly, we propose a Mobility-aware Service Migration scheme, named MSM, consisting of three layers: 1) the data collection layer; 2) the association patterns analysis layer; and 3) the service migration layer. Specifically, we first collect users’ historical Wi-Fi traces to mine the association patterns. We then design a user management mechanism to reduce the complexity of decision-making by using user association patterns. Finally, we formulate the service migration as a 2D-Markov decision process and devise a deep reinforcement learning (DRL) based algorithm to obtain service migration decisions in a large-scale MEC scenario. Extensive data-driven experiments are conducted to demonstrate the efficacy of MSM in reducing the system delay.

Hydropower peaking and stalled salmon migration are linked by altered reservoir hydraulics: A multidisciplinary synthesis and hypothesis

AbstractAdding variable renewable energy (solar, wind) in electricity portfolios will increase need for fast grid responses through hydropower peaking. Over 60 years of daily hydropeaking by four dams on the lower Snake River, United States of America provide an example of long‐term environmental impacts. Downstream‐migrating Chinook salmon (Oncorhynchus tshawytscha) subyearlings that normally transit the dammed river in summer slowed their migration into autumn with about one‐third of those delayed overwintering in the reservoirs. Specific cause for stalled migration is controversial, with options including evolution of a new migratory strain and action of environment on individual migrants. Analysis of archived dam data shows evidence of reservoir seiches (standing waves of waterbody oscillations) caused by within‐day hydropower peaking during the October–February period of stalled migration. Analyses of limnological literature identified typical water movements in seiches and analyses of biological literature identified typical effects on fish kinematics (shape, motion) of changing flows in a fish's immediate proximity. Process‐focused inference predicts anomalous fish‐migration behavior in seiche hydraulics, which matches fish‐tracking data obtained by others in Lower Monumental Reservoir. Fish tracks include upstream swimming (‘downstream’ in reverse seiche flows) and periods of disoriented movements typical of responses to repeatedly changing flows. This multi‐disciplinary, process‐focused synthesis yields a testable hypothesis that seiche‐flow hydraulics in the lower Snake River reservoirs from hydropower peaking contribute to known out‐migration delay and overwintering of late‐migrating fall Chinook salmon subyearlings. As hydropower peaking causes seiches in downstream reservoirs elsewhere in North America and Europe, migratory species elsewhere may be susceptible to similar migration delays with long‐term population effects.

Scheduling Policies for Stability and Optimal Server Running Cost in Cloud Computing Platforms

We propose throughput and cost optimal job scheduling algorithms in cloud computing platforms offering Infrastructure as a Service. We first consider online job migration and propose job scheduling algorithms to minimize job migration and server running costs. We consider algorithms that assume knowledge of job-size on the arrival of jobs. We characterize the optimal cost subject to system stability. We develop a drift-plus-penalty framework based algorithm that can achieve optimal cost arbitrarily closely. Specifically, this algorithm yields a tradeoff between delay and costs. We then relax the job-size knowledge assumption and give an algorithm that uses readily offered service to the jobs. We show that this algorithm gives order-wise identical cost as the job size based algorithm. Later, we consider offline job migration that incurs migration delays. We again present throughput optimal algorithms that minimize server running cost. We illustrate the performance of the proposed algorithms and compare these to the existing algorithms via simulation.

Magnetic Migration Delays in Fe-Based Amorphous Alloys

Magnetic Migration Delays in Fe-Based Amorphous Alloys

Multislot Fishway Improves Entrance Performance and Fish Transit Time over Vertical Slots

Pool-type fishways have been increasingly tested to improve fish passage performance and minimize migration delays. Designing cost-effective fishways is essential for a trade-off between water uses and successful longitudinal connectivity restoration. The multislot fishway (MSF) concept, which operates with 30–50% lower discharge than a vertical slot fishway (VSF), was recently developed. This study assessed and compared the entrance performance (entrance time; entry efficiency) and transit times of two cyprinids for VSFs and MSFs. Four configurations, with the same structural characteristics (slope; water depth; head drop; pool width and depth), operating with different discharges (Q), were tested (VSF 1: Q = 112 L·s−1; VSF 2: Q = 80 L·s−1; MSF 1: Q = 58 L·s−1; MSF 2: Q = 37 L·s−1). Hydrodynamics characterization was performed using a numerical model. Results showed that entry efficiency was higher in MSFs than in VSFs, while entrance time and transit time were overall lower. Numerical modelling revealed that velocities were around 30% lower in MSFs, and turbulence could reach a difference of around 70% in Reynolds shear stress and 50% in turbulent kinetic energy. Overall, MSFs can be considered as a cost-effective fishway solution that can balance the trade-offs between divergent interests in water uses.

Enterprise adoption of cloud computing with application portfolio profiling and application portfolio assessment

With the continued appeal and adoption of cloud computing, an assessment of cloud run costs and migration affordability prior to adoption would assist enterprises that have several legacy applications targeted for cloud migration. However, as cloud migrations have become more prevalent, many have been characterised by unsuccessful migration or application modernisation attempts. The primary reason behind the failed attempts is insufficient planning upfront, to identify which legacy applications are suitable to realise the benefits of public or private cloud, leading to time and cost overruns. There is a need for strategic decision making for application portfolios to mitigate the risks of cost overruns and migration delays. Thus, a Rough Order of Magnitude (ROM) of cloud run costs for an application portfolio is required in the planning phase as an input into IT governance. To obtain the ROM cloud run costs, it is necessary to baseline application data, preferably through automated discovery, and perform quantitative analysis of the applications. Therefore, we propose an approach to (a) baseline application data using Application Portfolio Profiling (APP), and (b) perform quantitative analysis of applications using an Application Portfolio Assessment (APA), to inform the legacy application migration decision. APP and APA are proposed as part of a Cloud Computing Considerations for Companies (CCCC) framework that enables an enterprise to make an informed decision regarding which legacy applications are to be migrated as part of enterprise Cloud Computing adoption. This decision is important because of the change in operating model, infrastructure requirements, hidden costs and commercial models inherent with cloud computing adoption. We validate the proposed framework through applying it to a real-world use case scenario that provides the necessary coverage to test the proposed framework.

Thermal sensitivity and flow-mediated migratory delays drive climate risk for coastal sockeye salmon

Climate change is subjecting aquatic species to increasing temperatures and shifting hydrologic conditions. Understanding how these changes affect individual survival can help guide conservation and management actions. Anadromous Pacific salmon ( Oncorhynchus spp.) in some large river systems are acutely impacted by the river temperatures and flows encountered during their spawning migrations. However, comparatively little is known about drivers of en route mortality for salmon in smaller coastal watersheds, and climate impacts may differ across watersheds and locally adapted salmon populations. To understand the effects of climate on the survival of coastal sockeye salmon ( Oncorhynchus nerka; hísn in Haíɫzaqv), we tagged 1785 individual fish with passive integrated transponders across four migration seasons in the Koeye River—a low-elevation watershed in coastal British Columbia—and tracked them during their relatively short migration (∼13 km) from river entry to spawning grounds. Overall, 64.7% of sockeye survived to enter the spawning grounds, and survival decreased rapidly when water temperatures exceeded 15 °C. The best-fitting model included an interaction between river flow and temperature, such that temperature effects were worse when flows were low, and river entry ceased at the lowest flows. Results revealed temperature-mediated mortality and migration delays from low water that may synergistically reduce survival among sockeye salmon returning to coastal watersheds.

Can Energy Depletion of Wild Atlantic Salmon Kelts Negotiating Hydropower Facilities Lead to Reduced Survival?

Repeat spawners constitute an important component of Atlantic salmon populations, but survival of post-spawning individuals (kelts) are often compromised by anthropogenic structures such as hydropower plants (HPPs). Potential effects of HPPs include migration delays and associated increased energy depletion, which potentially results in increased overall mortality. We combined a detailed 3D hydraulic model with high-resolution 3D tracking of tagged kelts (length 73–104 cm) to obtain estimates of kelt movement through water. These estimates were then used in an energetics model to estimate hourly energy expenditure while negotiating the HPP area. Hourly kelt energy expenditure varied between 0.8 and 10.1 kJ × h−1 and was dependent on kelt length. Degree of additional energy depletion can amount to several percent of remaining energy content (our study indicates 4–5 percentage points) potentially leading to reduced post-spawning survival. In turn, this can nullify the iteroparous breeding strategy and jeopardize long-term stability and persistence of Atlantic salmon populations inhabiting HPP rivers.

Avian Predation on Steelhead is Consistent with Compensatory Mortality

ABSTRACTNumerous factors such as predation, disease, injury, and environmental conditions (e.g., river flows, hydropower operations) can influence survival rates of fish. Although mortality due to predation is commonly assumed to be additive and result in a directly proportional reduction on survival rates, compensatory processes may work to counteract or negate the effects of predation mortality on survival rates. We applied a random effects model to a long‐term, mark‐recapture‐recovery data set on anadromous steelhead (Oncorhynchus mykiss) from the Snake River Basin in the northwestern United States to assess whether avian predation mortality constitutes an additive or compensatory source of mortality. Specifically, our assessment focused on predation mortality due to double‐crested cormorants (Phalacrocorax auritus) and Caspian terns (Hydroprogne caspia) on colonies in the Columbia River estuary. In addition, we evaluated several candidate environmental indices to examine potential interactions between the effects of predation versus environmental conditions on steelhead survival rates. Average predation rates were 3.3% for the double‐crested cormorant colony and 17.0% for the Caspian tern colony. For both colonies, the estimated correlation between the predation rate and survival rate of steelhead was near zero, indicating that mortality due to avian predation is compensatory. Models that included variables for river flow, juvenile migration timing, and an index of forage biomass in the ocean accounted for 56–59% of the variation in steelhead survival, whereas avian predation rates accounted for <1% of the variation. Management efforts to reduce the abundance of the bird colonies are unlikely to improve the survival or conservation status of steelhead; however, results indicate that steelhead survival could be improved by hydropower management decisions that increase river flows and reduce juvenile migration delays. © 2020 The Wildlife Society.

A method for detecting tumor cells derived from colorectal cancer by targeting cell surface glycosylation with affinity capillary electrophoresis

Circulating tumor cells (CTCs) are involved in metastasis; thus, one of the most important approaches for identifying metastatic cancer is to detect CTCs in blood. In the present study, we examined whether directly analyzing cells with capillary electrophoresis (CE) could distinguish cancer cells from normal cells, based on differences in cell surface glycosylation. We compared human colorectal cancer (CRC) cell lines to a normal colon epithelium cell line. Our results demonstrated that direct CE analysis could successfully distinguish between CRC and normal cells with high reproducibility, based on migration times. We found that the weighted-average migration time was significantly shorter for CRC cells than for normal cells. Next, we observed changes in the electrophoretic behaviors of CRC cells by adding five different types of lectins. When Aleuria aurantia lectin was added, migration delays were observed in CRC cells, but not in normal colon cells. Therefore, by focusing on shifts in migration time after adding specific lectins, we could distinguish cancer cells from normal cells. These findings suggested that this diagnostic method of directly analyzing cells with CE after adding specific lectin(s) could be useful for detecting the difference in the sugar moieties on a surface of normal and cancer cells.

Efficient virtual network function placement strategies for Cloud Radio Access Networks

The new generation of 5G mobile services place stringent requirements for cellular network operators in terms of latency and costs. The latest trend in radio access networks (RANs) is to pool the baseband units (BBUs) of multiple radio base stations and to install them in a centralized infrastructure, such as a cloud, for statistical multiplexing gains. The technology is known as Cloud Radio Access Network (CRAN). Since cloud computing is gaining significant traction and virtualized data centers are becoming popular as a cost-effective infrastructure in the telecommunication industry, CRAN is being heralded as a candidate technology to meet the expectations of radio access networks for 5G. In CRANs, low energy base stations (BSs) are deployed over a small geographical location and are connected to a cloud via finite capacity backhaul links. Baseband processing unit (BBU) functions are implemented on the virtual machines (VMs) in the cloud over commodity hardware. Such functions, built in software, are termed as virtual functions (VFs). The optimized placement of VFs is necessary to reduce the total delays and minimize the overall costs to operate CRANs. Our study considers the problem of optimal VF placement over distributed virtual resources spread across multiple clouds, creating a centralized BBU cloud. We propose a combinatorial optimization model and the use of two heuristic approaches, which are, branch-and-bound (BnB) and simulated annealing (SA) for the proposed optimal placement. In addition, we propose enhancements to the standard BnB heuristic and compare the results with standard BnB and SA approaches. The proposed enhancements improve the quality of the solution in terms of latency and cost as well as reduce the execution complexity significantly. We also determine the optimal number of clouds, which need to be deployed so that the total links delays, as well as the service migration delays, are minimized, while the total cloud deployment cost is within the acceptable limits.

Imidacloprid and chlorpyrifos insecticides impair migratory ability in a seed-eating songbird

Birds that travel long distances between their wintering and breeding grounds may be particularly susceptible to neurotoxic insecticides, but the influence of insecticides on migration ability is poorly understood. Following acute exposure to two widely used agricultural insecticides, imidacloprid (neonicotinoid) and chlorpyrifos (organophosphate), we compared effects on body mass, migratory activity and orientation in a seed-eating bird, the white-crowned sparrow (Zonotrichia leucophrys). During spring migration, sparrows were captured, held and dosed by gavage daily for 3 days with either the vehicle control, low (10% LD50) or high (25% LD50) doses of imidacloprid or chlorpyrifos and tested in migratory orientation trials pre-exposure, post-exposure and during recovery. Control birds maintained body mass and a seasonally appropriate northward orientation throughout the experiment. Imidacloprid dosed birds exhibited significant declines in fat stores and body mass (mean loss: −17% low, −25% high dose) and failed to orient correctly. Chlorpyrifos had no overt effects on mass but significantly impaired orientation. These results suggest that wild songbirds consuming the equivalent of just four imidacloprid-treated canola seeds or eight chlorpyrifos granules per day over 3 days could suffer impaired condition, migration delays and improper migratory direction, which could lead to increased risk of mortality or lost breeding opportunity.

Disruptions in asymmetric centrosome inheritance and WDR62-Aurora kinase B interactions in primary microcephaly

Recessive mutations in WD repeat domain 62 (WDR62) cause microcephaly and a wide spectrum of severe brain malformations. Disruption of the mouse ortholog results in microcephaly underlain by reduced proliferation of neocortical progenitors during late neurogenesis, abnormalities in asymmetric centrosome inheritance leading to neuronal migration delays, and altered neuronal differentiation. Spindle pole localization of WDR62 and mitotic progression are defective in patient-derived fibroblasts, which, similar to mouse neocortical progenitors, transiently arrest at prometaphase. Expression of WDR62 is closely correlated with components of the chromosome passenger complex (CPC), a key regulator of mitosis. Wild type WDR62, but not disease-associated mutant forms, interacts with the CPC core enzyme Aurora kinase B and staining of CPC components at centromeres is altered in patient-derived fibroblasts. Our findings demonstrate critical and diverse functions of WDR62 in neocortical development and provide insight into the mechanisms by which its disruption leads to a plethora of structural abnormalities.

Neural-specific deletion of the focal adhesion adaptor protein paxillin slows migration speed and delays cortical layer formation.

Paxillin and Hic-5 are homologous focal adhesion adaptor proteins that coordinate cytoskeletal rearrangements in response to integrin signaling, but their role(s) in cortical development are unknown. Here, we find that Hic-5-deficient mice are postnatal viable with normal cortical layering. Mice with a neural-specific deletion of paxillin are also postnatal viable, but show evidence of a cortical neuron migration delay that is evident pre- and perinatally, but is not detected at postnatal day 35 (P35). This phenotype is not modified by Hic-5 deficiency (double knockout). Specific deletion of paxillin in postmitotic neurons using Nex-Cre-mediated recombination as well as in utero electroporation of a Cre-expression construct identified a cell-autonomous requirement for paxillin in migrating neurons. Paxillin-deficient neurons have shorter leading processes that exhibited multiple swellings in comparison with control. Multiphoton imaging revealed that paxillin-deficient neurons migrate ∼30% slower than control neurons. This phenotype is similar to that produced by deletion of focal adhesion kinase (FAK), a signaling partner of paxillin, and suggests that paxillin and FAK function cell-autonomously to control migrating neuron morphology and speed during cortical development.

Father's Migration and Leaving the Parental Home in Rural Mozambique.

Migration is an increasingly common demographic phenomenon and has important implications for the well-being of family members left behind. Although extensive research has examined the impact of parental labor migration on school-age children, less is known about its effect on adolescents. In this study, the authors used longitudinal survey data collected in rural Mozambique (N = 515) to assess the association between father's migration and adolescent children's leaving the parental home, an important component of the transition to adulthood. The results showed that father's migration delays home-leaving for adolescent girls and that these effects are not mediated by school enrollment. The results for boys were inconclusive. The authors also found that remittances and longer durations of paternal migration were negatively associated with the transition out of the home. On the basis of the findings, they argue that father's migration delays girls' marriage.

South to north: Contrasting late-glacial and early-Holocene climate changes and vegetation responses between south and north Norway

Norway shows south–north climate and vegetation gradients today. Were there similar gradients during the late-glacial and early Holocene, 14,700–9000 years ago? A comparison was made along a south–north transect in Norway of plant-macrofossil reconstructions of past vegetation changes and independent summer temperature records derived from parallel chironomid data (C-Tjul). Three lake sites were selected with sediment cores with good chronological control. The importance of soil moisture is reflected by the reconstructed vegetation in relation to the temperature regime. Besides climate drivers, how important were intrinsic succession and competition in influencing vegetation patterns? Were migration delays significant, why and by how much? Oceanic climate in the late-glacial in south-west Norway resulted in snow-bed vegetation and glacier development in the Younger Dryas (YD). In contrast, the north was arid and continental, even into the early Holocene. Overall, temperatures were about 2°C colder than in the south. The YD impact differed markedly between south and north Norway. In the south, cooling at c. 12,700 cal. yr BP was swift and marked by strong responses. In the north, there was no impact at the chronological start of the YD, but cooling occurred later about 12,450 cal. yr BP together with increased aridity. During the early Holocene, temperature and oceanicity increased progressively northwards as the North Atlantic Current became established. Birch woodland developed in the south about 660 years after the start of the Holocene, after about 1000 years on Andøya, and after about 1450 years in northernmost Norway. However, the 590 year lag in the south after C-Tjul reached 11°C, the limiting temperature for tree-birch growth, decreased to 400 years in the north, as the birch tree-line kept pace with temperature rise. In the far north, a thermal maximum of 1°C above today’s mean July temperature and parallel vegetation development were recorded from 10,100 to 9370 cal. yr BP. On Andøya, temperatures exceeded present values by 1°C after 9700 cal. yr BP. There was no detectable period of above modern temperatures further south before 9000 cal. yr BP.