We present a new pollenaclimate calibration data-set from northern Europe consisting of 583 modern pollen samples and high-resolution, GIS-based modern climate data. The pollen data are characterised ...by high taxonomic resolution (167 taxa) and homogenous taphonomy (all samples are from small-to-medium-sized lakes). To assess the potential of this calibration set for the reconstruction of different climatic parameters, we use novel regression tree methods to analyse the effect on pollen composition and variability of four parameters: summer temperature, winter temperature, water balance, and continentality index. We use multivariate regression trees to analyse the variation in pollen assemblages in modern climate space, while boosted regression trees are used to analyse the relative influence of different climatic parameters on each taxon. We find taxon responses to be relatively individualistic. While most taxa (65%) are most responsive to summer temperature, other parameters are either primary determinants or significant secondary determinants for many taxa. At the assemblage level, significant variation is found in assemblages from similar summer temperature regimes, with distinct clusters of assemblages also identified along the continentality gradient. As a multivariate method, we consider boosted regression trees highly effective in describing and modelling modern climateataxon relationships.
At regional scale, it is dominantly considered in the European literature that litter decomposition is higher in soils from calcareous than siliceous bedrocks because of higher pH in the former ...forest ecosystems. We tested the alternative hypothesis that this should rather be due to differences in physical characteristics of the bedrock, with likely higher decomposition on calcareous than siliceous bedrocks in wet climates because of more favourable texture in the former and nutrient leaching in the latter, and the opposite in dry climates because of higher drought stress in calcareous soils. We assessed, four consecutive years with contrasting climates, the litter decomposition of a unified litter of Abies alba needles with the litterbag method in 70 forest sites located on both bedrocks and in wet oceanic and dry continental climates of the European Alps and the Pyrenees. Average and annual climate data were analysed with principal component analyses and the effects of bedrock type, average and annual climate drought stresses on litter decomposition were analysed, separately in the Alps and the Pyrenees, with analyses of variance. We found, in both mountain ranges, a highly significant bedrock type by average climate drought stress interaction on litter decomposition, due to a strong decrease in litter decomposition from wet oceanic to dry continental sites on calcareous bedrocks only. Although litter decomposition did not change over all years in siliceous sites with increasing climate drought stress, it increased during wet years in the dry continental sites only, in particular in the Pyrenees where interannual climate variability was higher. Together our results strongly support the physical hypothesis and not the chemical hypothesis. We argue that the chemical hypothesis was proposed based on studies only conducted in low elevation wet temperate sites comparing mull humus types from deciduous forests on calcareous soils to mor and moder humus types from evergreen forests on highly sandy siliceous bedrocks. Our study conducted on a wider range of climate and bedrock conditions bring strong evidence that litter decomposition is rather dependent on the physical characteristics of the bedrocks.
•Litterbag experiment conducted in 70 sites from the Alps and the Pyrenees.•Litter decomposition is higher on siliceous than calcareous soils in dry climates.•Soil pH does not explain differences in litter decomposition.
ABSTRACT
Oceanity and continentality strongly influence the climate of a region. Aiming at understanding these influences on the Iberian Peninsula climate, the spatial distributions of precipitation, ...air temperature and five climatic indices are analysed during the period 1901 and 2012 and in three sub‐periods (1901–1940, 1941–1980 and 1981–2012). This study focuses on investigating the continental and oceanic characteristics of the Iberian climate by using the Conrad–Pollak and Johansson Continentality Indices, as well as Kerner and Marsz Oceanity Indices. Gridded precipitation and air temperature data sets are used on a monthly basis. Results reveal hyper‐oceanic (maritime) characteristics in the northernmost portion of Iberia, continental in the inner region comprising Extremadura, Castile‐La Mancha and Andalusia, and maritime characteristics in between. It is worth noting that within these regions the continental (maritime) characteristics become stronger (weaker) between 1981 and 2012. Statistically significant linear trends show an increase in both temperature (2–4°C) and on continental influences in the northwestern and southeastern regions of Iberia for the entire period. Statistically significant correlations are also found between the Johansson Continentality Index and both Conrad–Pollak and Marsz Oceanity Indices at a 95% confidence level, revealing a good agreement of results among these indices.
The continentality level depends on several geographical factors, such as altitude which also plays an important role. In effect, the aim of this work is to carry out some simple tests related to the ...relationship continentality-altitude, by: a) calculating the regressions between altitude and a series of indices deriving from the analysis of the yearly march of temperature for each location examined; b) evaluating the characteristics of the thermal regime of some high mountain localities. The results obtained confirm a trend towards for a marked increase in the degree of oceanicity of the climate along with increasing altitude.
The Indian subcontinent has a unique physiography, which is important from the weather and climate perspective, having a prominent role in the 30-year period of reference. Conrad Continentality Index ...(CCI) and Kerner Oceanity Index (KOI) are investigated to determine the influence of continentality and oceanity over the Indian region from 1981–2010 and further to evaluate the teleconnections between ENSO (El Niño–Southern Oscillation)/Indian Ocean Dipole (IOD) and Conrad Continentality/Kerner Oceanity Indices. KOI shows a positive relationship with SST, especially over the Niño3 region of the Pacific (warm tongue) for all the India, Central India and Peninsular India regions. CCI, for Northeast India, shows positive correlation with SST over Niño1 + 2 regions (coastal South America), while Peninsular India and Central India showed no relation. The study identifies the importance of Conrad Continentality and Kerner Oceanity Indices as indicators for studying the impact of coupled ocean-atmosphere phenomena like ENSO and IOD. These indices also have utmost importance for the fields of agriculture and solar/wind for the Indian region since they also consider the impact of local climatic conditions.
The aim of the paper is to present general characteristics of the climate in Poland during the Vistulian (Weichselian), expressed by changes of its continentality during warm and cold intervals. This ...last glacial stage in Poland is commonly subdivided into Early Vistulian (MIS 5d-a), Lower Plenivistulian (MIS 4), Interplenivistulian (MIS 3), and Upper Plenivistulian and Late Vistulian (MIS 2). Main climatic features of this glacial stage could be reconstructed, based on compilation from published data concerning characteristics of glacial, fluvial and aeolian sedimentary environments, geomorphology, analysis of indicator plant species, Coleoptera, and geographical distribution of periglacial structures. These data were indicative especially for evaluation of mean temperature of the warmest and the coldest months but could be also helpful in determination of drier intervals and some aspects of general atmospheric circulation. Paleoclimatic characteristics of the last glacial stage from the territory of Poland were put into the European context. During the Early Vistulian in eastern Poland, higher continentality was characteristic for interstadials (Amersfoort, Brörup and Odderade), and was considerably lower during the intervening colder stadials (Herning, a cooling between Amersfoort and Brörup, Rederstall). Among the interstadials, the most continental climate occurred during Brörup (similar continentality as at present), considerably less during Amersfoort and the least during Odderade. A decreasing trend of continentality for the cold stadials of the Early Weichselian eastwards in Europe could result from a remarkably less dynamic Gulf Stream in the North Atlantic when the ocean was covered with vast sea ice during winters, whereas the adjoining continent was occupied by permafrost, and the atmospheric circulation was presumably driven also by the Scandinavian ice sheet.
Aim
Knowledge of broad‐scale biogeographical patterns of animal migration is important for understanding ecological drivers of migratory behaviours. Here, we present a flyway‐scale assessment of the ...spatial structure and seasonal dynamics of the Afro‐Palaearctic bird migration system and explore how phenology of the environment guides long‐distance migration.
Location
Europe and Africa.
Time period
2009–2017.
Major taxa studied
Birds.
Methods
We compiled an individual‐based dataset comprising 23 passerine and near‐passerine species of 55 European breeding populations, in which a total of 564 individuals were tracked during migration between Europe and sub‐Saharan Africa. In addition, we used remotely sensed primary productivity data (the normalized difference vegetation index) to estimate the timing of vegetation green‐up in spring and senescence in autumn across Europe. First, we described how individual breeding and non‐breeding sites and the migratory flyways link geographically. Second, we examined how the timing of migration along the two major Afro‐Palaearctic flyways is tuned with vegetation phenology at the breeding sites.
Results
We found the longitudes of individual breeding and non‐breeding sites to be related in a strongly positive manner, whereas the latitudes of breeding and non‐breeding sites were related negatively. In autumn, migration commenced ahead of vegetation senescence, and the timing of migration was 5–7 days earlier along the Western flyway compared with the Eastern flyway. In spring, the time of arrival at breeding sites was c. 1.5 days later for each degree northwards and 6–7 days later along the Eastern compared with the Western flyway, reflecting the later spring green‐up at higher latitudes and more eastern longitudes.
Main conclusions
Migration of the Afro‐Palaearctic landbirds follows a longitudinally parallel leapfrog migration pattern, whereby migrants track vegetation green‐up in spring but depart before vegetation senescence in autumn. The degree of continentality along migration routes and at the breeding sites of the birds influences the timing of migration on a broad scale.
Aim
The global relationship between treeline elevation and temperature (or latitude as a proxy) is well established. However, additional large‐scale and regional abiotic influences such as mass ...elevation effect (MEE), continentality and isolation are superimposed onto the latitude‐treeline relationship. To quantify these effects, we apply globally applicable measures and test the effects of MEE, an aspect of continental climate and isolation on treeline elevation.
Location
Global treeline elevations (n = 629).
Methods
We sampled treeline sites using earth observation. We calculated MEE as the distance to the nearest mountain chain limits. Continentality was assessed by the distance to the nearest coastline. Isolation was calculated by the nearest distance of a mountain chain to another mountain chain within a comparable elevational band.
Results
The global latitudinal pattern showed a distinct bimodal latitude‐treeline elevation relationship. Treeline elevations increased substantially with increased MEE and distance to coastlines while isolation even decreased treeline elevations.
Main Conclusions
Our study shows a globally consistent effect of MEE and distance to the coastline on treeline elevation, contributing to our basic understanding of large‐scale biogeographic processes governing treeline formation. MEE and continentality reduce cloudiness and increase solar radiation, resulting in higher treeline elevations. Isolation effects are not consistent and may be influenced by immigration and speciation. Understanding global treeline formation using comprehensive measures contributes to a better understanding of how environmental conditions determine vegetation boundaries at large spatial scales.
Current multi-proxy studies on a long sediment sequence preserved at Sokli (N Finland), i.e. in the central area of Fennoscandian glaciations, are drastically changing classic ideas of glaciations, ...vegetation and climate in northern Europe during the Late Pleistocene. The sediments in the Sokli basin have escaped major glacial erosion due to non-typical bedrock conditions. In this review, the Sokli record is compared in great detail with other long proxy records from central, temperate and northern, boreal Europe. These comprise the classic records of La Grande Pile (E France) and Oerel (N Germany) and more recently obtained records from Horoszki Duże (E Poland) and Lake Yamozero (NW Russia). The focus of the review is on pollen, lithology and macrofossil- and insect-based temperature inferences. The long records are further compared with recent proxy data from nearby terrestrial sites as well as with the rapidly accumulating high-resolution proxy data from the ocean realm. The comparison allows a re-examination of the environmental history and climate evolution of the Last Interglacial–Glacial (LI–G) cycle (MIS 5–2). It shows that environmental and climate conditions during MIS 5 (ca 130–70 ka BP) were distinctly different from those during MIS 4–2 (ca 70–15 ka BP). MIS 5 is characterized by three long forested intervals (broadly corresponding to MIS 5e, 5c, 5a), both in temperate and northern boreal Europe. These mild periods were interrupted by two short, relatively cold and dry intervals (MIS 5d and 5b) with mountain-centered glaciation in Fennoscandia. Millennial scale climate events were superimposed upon these longer lasting climate fluctuations. The time interval encompassing MIS 4–2 shows open vegetation. It is characterized by two glacial maxima (MIS 4 and 2) with sub-continental scale glaciation over northern Europe and dry conditions in strongly continental eastern European settings. High amplitude climate oscillations of millennial duration characterized the climate variability of MIS 3. Mild climate conditions in early MIS 3 caused large-scale deglaciation of the Fennoscandian Ice Sheet, and ice-free conditions with Betula-dominated vegetation (including tree birch) persisted over large parts of Fennoscandia, possibly interrupted by glaciation, during major part of MIS 3 till ca 35 ka BP. Overall, MIS 5 was mostly mild with warmest or peak interglacial conditions at the very start during MIS 5e. MIS 4–2 was mostly cold with most extreme or peak glacial conditions in the closing phase during MIS 2. This points to a subdivision of the last climate cycle into an early, overall mild interglacial half and a late, overall cold glacial half, each with duration of ca 50 ka. This review also shows that the climate variability in central and northern Europe during the LI–G cycle was mostly in degrees of continentality with major shifts in winter temperature and precipitation values; summer temperatures, on the other hand, remained largely unchanged. It points to the waxing and waning of sea-ice over the North Atlantic Ocean as a possible characteristic feature of the Late Pleistocene. The present compilation, based on long terrestrial sequences, high-resolution multi-proxy data from the oceans, and quantified paleo-climate data, strongly favors a definition of entire Marine Oxygen Isotope Stage 5 as the Last Interglacial similar as in the original marine stratigraphy and the stratigraphy at La Grande Pile in France. The proxy-based climate data places the start of the Last Glacial at the base of MIS 4 and the northwest European Pleniglacial. It shows that the division between the Eemian (MIS 5e) and the Early Weichselian (MIS 5d-a) is not useful, as not relevant from a climate point of view.
•European and marine proxy data provides new insights in MIS 5–2 climate evolution.•Study divides last climate cycle into early (MIS 5) mild and late (MIS 4–2) cold part.•Changes in degree of continentality characterized climate variability during MIS 5–2.•Summer temperatures generally fluctuated only slightly during last climate cycle.•Minor ice-cover over N Europe during MIS 3 persisted until ca 35 ka BP.
Few continental palaeoenvironmental sedimentary sequences from Southern Europe are long enough to span the last interglacial period (Marine Isotopic Stage-MIS 5), the last glacial cycle (MIS 4 to 2) ...and the Holocene. El Cañizar de Villarquemado (North-Eastern Iberian Peninsula) is an exceptional sedimentary lacustrine sequence spanning the last ca. 135,000 years of environmental change in an area of inland Iberia characterized by Mediterranean climate with strong continentality. We present a multiproxy study which combines palynological, sedimentological and geochemical analyses framed by an independent, robust chronology. Hydrological and climate evolutions were reconstructed by sedimentological and geochemical proxies. Development of wetlands and shallow carbonate lakes support relatively humid conditions during MIS 6, till the onset of MIS 4, and during the Holocene. Palaeohydrological conditions were drier during MIS 5 (dominance of peat environments) than during the Holocene (more frequent carbonate-producing lakes). Sedimentological evidence indicates extremely arid conditions during MIS 3 with greater activity of alluvial fans prograding into the basin. Sedimentary facies variability highlights a large environmental and hydrological variability during MIS 2 and a rapid humidity response to the onset of the Holocene.
Compared to classic Mediterranean sites, we found novel pollen assemblages for the end of MIS 6 and MIS 5 indicating that the vegetation cover was essentially represented by sustained high proportions of continentality-adapted taxa dominated by Juniperus during the relatively humid conditions since MIS 6 till the onset of MIS 4. Higher evapotranspiration in inland Iberia would have increased during periods of higher seasonal insolation maxima, impeding soil development and the usual mesophyte expansion during interglacials observed in other Mediterranean areas. Four main periods of forest development occurred in Villarquemado during MIS 5e, MIS 5c, MIS 5a and the Holocene; secondary peaks occurred also during MIS 3. During colder but still relatively humid MIS 4, junipers and Mediterranean taxa disappear but some mesophytes and cold-tolerant species persisted and Pinus became the dominant tree up to modern times. Pollen assemblages and geochemical data variability suggest a dominant control of seasonality and the impact of North Atlantic dynamics both during MIS 5 (cold events C18-C24) and full glacial conditions (HE and D-O interstadials). At millennial scales, steppe herbaceous assemblages dominated during the extremely arid conditions of MIS 3 and pines and steppe taxa during glacial period MIS 2. Villarquemado sequence demonstrates that the resilient behaviour of conifers in continental areas of inland Southern European regions is key to understand the glacial–interglacial vegetation evolution and to evaluate scenarios for potential impacts of global change.
•Continentality and moisture drove Mediterranean landscapes during last interglacial.•Evapotranspiration impeded soil development and mesophyte expansion in inland Iberia.•The resilient behaviour of conifers is key to evaluate impacts of Global Change.
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