Degree Of Continentality Research Articles

Биоклиматические варианты оробиома Северо-Восточного Забайкалья

Introduction. The spatial structure of the biota at the regional level of its organization is most closely associated with the climate, expressed primarily through bioclimatic indicators. In the geography of the botanical diversity of Northeastern Transbaikalia, which is characterized by a complex organization of vegetation cover, the influence of a number of important gradients of climatic conditions is expressed. The identification of these gradients was the purpose of this research. Methods and materials of the research. The methodological basis of the research was the ecosystem approach to the identification and evaluation of phytocenotic diversity associated with ecological and geographical factors that determine its spatial differentiation. The geographic and genetic classification of plant communities was used to identify the typological diversity of vegetation. The climatic characteristics of the Northeastern Transbaikalia was given on the basis of key bioclimatic indicators (global model BioClim). The bioclimatic substantiation of the spatial structure was carried out taking into account the principles of identifying the diversity of ecosystems at the regional level. Mapping of the bioclimatic variants of the orobiome was compiled using the clustering of units according to the average values of parameters by the k-means method. Research results and discussion. A joint analysis of vegetation and climate made it possible, for the first time for Northeastern Transbaikalia, to determine the internal structure of ecosystem diversity that develops in the mountains within the framework of an orobiome. It also allowed mapping the spatial organization of ecosystems at the regional level on a climate basis. Using the cluster analysis of climatopes of the main vegetation formations, subdivisions of the orobiome (bioclimatic variants) are proposed. Two variants of the Ist order are expressed through the structure of the vegetation cover of mountain systems: the relatively low Patom highland in the north, and more massive ridges of the strongly dissected North Baikal and Stanovoy highlands in the south. Variants of the IInd order, differing in the degree of continentality and moisture conditions, have specificity in the altitudinal belts and sub-belts of vegetation. Diversity within belts and sub-belts, expressed through the typological diversity of vegetation at the level of formations, classes, and groups of associations, is marked by climatic differences in bioclimatic variants of the IIIrd order. The diversity of climatic conditions that determine the phytocoenotic diversity of Northeastern Transbaikalia is characterized through integral bioclimatic types of orobiome, determined by temperature and moisture supply. Three ombroclimatic types were distinguished by continentality conditions. The influence of the complex orographic structure of a vast mountainous territory, as well as zonal and sectoral patterns in changing climatic conditions, is characterized in their change from continental to extracontinental in according to the degree of climate continentality. The same factors determine the identification of three thermoclimatic types, which are associated with the distinguished altitudinal vegetation belts (mountain tundra, subalpine, mountain taiga). The temperate cold type is expressed in the intermountain depressions and low mountains of the Patom highlands, the cold type is associated with the middle mountains and the lower part of the high mountains (mountain taiga and subalpine belts), and the extra cold type is distinguished in the high mountains of the most massive ridges – Kodar and Kalar. Conclusion. Quantitative interpretation of the climatic conditions of the bioclimatic variants of the orobiome made it possible to give an integral evaluation of the climatic conditionality of the development of basic vegetation formations, the altitudinal belt divisions, and the altitudinal spectra of vegetation in general. The resulting basis can be used for the sustainable development of the region in connection with economic activities in areas adjacent to the Baikal-Amur Railway, for monitoring and forecasting changes in vegetation and ecosystems in general due to climate change and intensification of economic activities in the region.

ESTIMATION OF THE DEGREE OF CLIMATE CONTINENTALITY IN SARATOV REGION AT THE BEGINNING OF THE XXI CENTURY

A quantitative assessment of climate change is given in the territory of the Saratov region at the beginning of the 21st century. As a result of the research, an increase in annual air temperature was noted everywhere - its average value for the region was 7,1°С, the largest increase in average monthly temperatures was observed in winter. An analysis of the annual amount of precipitation showed their increase in the west of the region and in its central part, a decrease in precipitation was observed in the north of the region and in the Trans-Volga region. The conditions of the degree of climate continentality are estimated in different natural and climatic zones: forest-steppe, arid steppe and semi-desert for the period from 2005 to 2020. The calculated indices of climate continentality using the methods of G. Zenker, I. Schrepfer, L.A. Gorchinsky, S.P. Khromov, N.N. Ivanov showed a synchronous trend towards a decrease in the degree of continentality, which is associated with regional warming, which is most pronounced in the cold period.

Upward Treeline Shifts in Two Regions of Subarctic Russia Are Governed by Summer Thermal and Winter Snow Conditions

Climate warming impacts on alpine treeline dynamics. However, we still lack robust assessments of the long-term impacts of climate on tree recruitment at the treeline, particularly in remote areas such as the subarctic regions of Russia subjected to different climate influences. We expected that the treelines in two regions may have different features and dynamics patterns. We analyzed climate variables and assessed treeline dynamics by quantifying recruitment using the tree rings of ca. 7000 trees of four species (Betula pubescens Ehrh. ssp. tortuosa, Pinus sylvestris L., Picea abies Ledeb. ssp. obovata, Larix gmelinii Rupr.) along 14 altitudinal transects (series of study plots). We compared the Khibiny Massif (Kola Peninsula) and the western Putorana Plateau, subjected to oceanic and continental influences, respectively. In both regions, summers became warmer, and winters became snowier during the past century. At the low part of the treeline ecotone, tree recruitment has slowly increased since the mid-18th century at the Putorana Plateau and the mid-19th century at the Khibiny but accelerated in the early 20th century at both regions and reached a maximum peak in the second half of the past century. Treeline encroachment intensified in the 1930s at the Khibiny and the 1950s at the Putorana Plateau. Trees encroached in the tundra leading to upward treeline shifts in the late 20th century. The slope exposure affected the rates of treeline shift with higher upward advances on southern-oriented slopes. Tree recruitment and early-winter precipitation were positively correlated. The differences in species composition, treeline altitude and influences of slope orientation on treeline dynamics can be explained primarily by differences in the degree of continentality. The abundance of saplings in both regions allows the future encroachment of trees into tundra and further treeline upward shifts to be forecast.

Geographic variation and temporal trends in ice phenology in Norwegian lakes during the period 1890–2020

Abstract. Long-term observations of ice phenology in lakes are ideal for studying climatic variation in time and space. We used a large set of observations from 1890 to 2020 of the timing of freeze-up and break-up, and the length of ice-free season, for 101 Norwegian lakes to elucidate variation in ice phenology across time and space. The dataset of Norwegian lakes is unusual, covering considerable variation in elevation (4–1401 m a.s.l.) and climate (from oceanic to continental) within a substantial latitudinal and longitudinal gradient (58.2–69.9∘ N, 4.9–30.2∘ E). The average date of ice break-up occurred later in spring with increasing elevation, latitude and longitude. The average date of freeze-up and the length of the ice-free period decreased significantly with elevation and longitude. No correlation with distance from the ocean was detected, although the geographical gradients were related to regional climate due to adiabatic processes (elevation), radiation (latitude) and the degree of continentality (longitude). There was a significant lake surface area effect as small lakes froze up earlier due to less volume. There was also a significant trend that lakes were completely frozen over later in the autumn in recent years. After accounting for the effect of long-term trends in the large-scale North Atlantic Oscillation (NAO) index, a significant but weak trend over time for earlier ice break-up was detected. An analysis of different time periods revealed significant and accelerating trends for earlier break-up, later freeze-up and completely frozen lakes after 1991. Moreover, the trend for a longer ice-free period also accelerated during this period, although not significantly. An understanding of the relationship between ice phenology and geographical parameters is a prerequisite for predicting the potential future consequences of climate change on ice phenology. Changes in ice phenology will have consequences for the behaviour and life cycle dynamics of the aquatic biota.

Broad‐scale patterns of the Afro‐Palaearctic landbird migration

AbstractAimKnowledge 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.LocationEurope and Africa.Time period2009–2017.Major taxa studiedBirds.MethodsWe 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.ResultsWe 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 conclusionsMigration 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.

Vegetation and climate record from Abric Romaní (Capellades, northeast Iberia) during the Upper Pleistocene (MIS 5d−3)

This study addresses the pollen record of Abric Romaní archaeological site and the climate evolution of the last interglacial and glacial stadials in the Iberian Peninsula. The new pollen record spans the interval from 110,000 to 55,000 years ago. In general, the glacial/stadial vegetation is characterized by a steppe and herbaceous communities indicating dry and cold climatic conditions, whereas the vegetation optimum of past interglacials can be described as pine-oaks with mediterranean forest indicating milder and moister climatic conditions. During the first half of the MIS 5a and the MIS 5c, the region was warmer, which is characterized by temperate forests. However, the existence of Artemisia steppes during the second part of the MIS 5a indicates that the degree of continentality can be related to the low winter temperatures and precipitation. During MIS 4, a colder and dryer climate enabled the development of open vegetation (dominated by Artemisia with Poaceae and other Asteraceae) around the study site.

The specificities of the climate of Danilovgrad (Montenegro)

Danilovgrad and the Bjelopavlica Plain belong to the submediterranean zone of the Mediterranean climate region. The aim of this paper was to determine some specific characteristics of the Danilovgrad climate, such as the degree of continentality, aridity and bioclimatic characteristics. Data used in the research cover the period 1955-2011. The results of the study showed the dominance of the continental effect on temperature, while oceanicity was less pronounced. In hygric terms, during most of the year the climate of Danilovgrad is characterized as low humid to perhumid. Moreover, in the period October-March it is very humid, which points to the domination of oceanic influences. During the three summer months, it is dry to very dry. Based on the average monthly values of the equivalent temperature - an indicator of physiological (subjective) feeling of heat, the winter months in Danilovgrad are not assessed as very cold. It is cold in January, and in February and December it is cool. It is fresh in March and November, comfortable in April and October, and warm in May and September. In Danilovgrad, in summer it is overheated and a little muggy. All considered indicators point to quite pronounced oscillations during the year, especially in terms of humidity. Comparing the obtained results with Podgorica, it can be concluded that the climate of Danilovgrad is more continental, a bit colder and wetter.

Indicators of specificity of climate: The example of Podgorica (Montenegro)

Climatic indices complexly display the climate of a place, and certainly influence its more qualitative characterization. In this paper, the specificity of the climate is analyzed, such as the degree of continentality and aridity, in the example of the city of Podgorica. The climate was considered on the basis of the data for almost the entire instrument period (1951–2017). The results obtained for thermal continentality show that maritime influences are primary and predominant, but the influence of the continent is also significant. In a hygric sense, the climate of Podgorica is characterized as poorly arid to poorly humid with significant oscillations during the year. The warmer period of the year, especially the summer, has the characteristics of arid climate. The colder period of the year, especially from November to February, has the characteristics of humid and even perhumidic climate, while the transitional seasons show signs of semi-aridity and semi-humidity.

Geographical characteristics of the timberline in the Carpathians

The pattern of timberline distribution on mountain ranges world-wide is related to global factors. The basic factor is temperature and the amount of radiation, which falls with increasing distance from the equator. Additionally, this basic relationship is overlaid by the specific features of the type of climate on the massif (degree of continentality or oceanity) and the mass-elevation effect. In the Carpathians, the mass elevation effect seems to have bigger impact on the location of timberline (R 2 = 0.71, p = 0.00) than their latitudinal location (R 2 = 0.56, p = 0.00). The timberline altitude changes by 70 m a.s.l. (±20 m) with each degree of latitude. The influence of the type of the climate is complex and it is not clearly visible due to past and recent human impact.

Climate and soil salinity in the deserts of Central Asia

A comparative analysis of climatic and soil salinity characteristics of the deserts of Central Asia, including deserts of the Turan Depression, the Gobi Desert, and deserts of the Dzungar and Tarim depressions was performed. The climatic characteristics—the degree of aridity, the degree of continentality, and the amount and regime of precipitation—are different in these deserts. No direct relationships between the areas occupied by the automorphic salt-affected soils and the aridity of the climate are observed in the studied regions. In the automorphic landscapes of Asian deserts, the degree and chemistry of the soil salinization and the distribution of salt-affected soils are controlled by the history of the particular territories rather than by their modern climatic conditions. The presence and properties of the salt-bearing rocks and the eolian migration of salts play the most significant role. The deficit of moisture in the modern climate favors the preservation of salt accumulations in places of their origin. The specific features of the climate, including the regime of precipitation, affect the redistribution of salts in the profiles of automorphic salt-affected soils. An increase in the degree of climatic continentality is accompanied by the decrease in the intensity of weathering and initial accumulation of salts. A different situation is observed in the soils of hydromorphic desert landscapes, in which the degree of salinity of the surface horizons and the area occupied by salt-affected soils are directly influenced by the modern climatic conditions.

Comparison of cropland and forest surface temperatures across the conterminous United States

Global climate models (GCM) investigating the effects of land cover on climate have found that replacing extra-tropical forest with cropland promotes cooling. We compared cropland and forest surface temperatures across the continental United States in 16 cells that were approximately 1°×2° using 1km2 MODIS land surface temperature (LST) data and land cover from the 0.0009km2 National Land Cover Database (NLCD). We found that forest surface temperatures tended to be cooler than cropland surface temperatures. This relationship held for spring, summer, fall, and annually. In winter, cropland surface temperatures were cooler than forest surface temperatures except in the southeastern United States, where forest surface temperatures were also cooler in winter. The difference between cropland and forest surface temperatures was driven by daytime maxima, which tended to be twice as large as differences in nighttime minima. The dominance of daytime maxima was influenced by the degree of continentality. For cells on coastal margins or with a high proportion of inland lakes, differences between cropland and forest nighttime minima tended to be very small. In more continental locations croplands were noticeably cooler at night which often led to insignificant differences between cropland and forest average surface temperatures.

Quantitative reconstructions of changes in regional openness in north-central Europe reveal new insights into old questions

By applying the recently developed model REVEALS (Regional Estimates of VEgetation Abundance from Large Sites) (Sugita, 2007) to pollen data from a large number of sites across Northern Germany and Denmark, we construct maps of regional patterns in landscape openness and in cover abundance of key plant taxa in the cultural landscape of north-central Europe for selected time slices in the Holocene.The results indicate that the pattern of landscape openness across the regions of northern Germany and Denmark prior to the introduction of agriculture was affected by soil conditions and degree of continentality. The 8.2 ka climate event did not lead to a general decrease in tree cover, although some changes in species composition were observed. The early phases of agriculture also had little effect on landscape openness at the regional scale, but later human impact lead to large scale deforestation and development of arable areas, grasslands and of heathlands in the north-western part of the region. The timing and degree of deforestation, and the weight between arable and grazing areas varied in space, partly due to differences in natural conditions, partly due to differences in cultural impact.

Application of the Global Bioclimatic Classification to Iran: implications for understanding the modern vegetation and biogeography

This study aims at proposing a new bioclimatic zonation for Iran based on the recently developed Global Bioclimatic Classification System (GBC) and tries to re-appraise this classification system by checking the degree of correspondence between its bioclimatic zones and the distribution of major phytogeographical regions, biomes, and a selection of plant and insect taxa of Iran. After application of the GBC to Iranian meteorological data, three macrobioclimates, ten bioclimates, and three bioclimatic variants were distinguished. The Mediterranean macrobioclimate is the dominant macrobioclimate and correlates with the Irano-Turanian biogeographical region, the Tropical macrobioclimate in southern Iran correlates with the Saharo-Sindian region and finally a small Temperate macrobioclimatic zone in northern Iran correlates with the Euro-Siberian region. Mediterranean macrobioclimate of Iran displays a wide range of bioclimates including Mediterranean pluviseasonal-oceanic, Mediterranean xeric-oceanic, Mediterranean pluviseasonal-continental, Mediterranean xeric-continental, Mediterranean desertic-oceanic, and Mediterranean desertic-continental. Tropical macrobioclimate also shows a range of bioclimates including Tropical xeric, Tropical desertic, and Tropical hyperdesertic. Finally, Temperate macrobioclimate has only one bioclimate i. e. Temperate oceanic. In conclusion, bioclimatic zones identified using the GBC system correlate well with the main phytogeographical regions of Iran at macrobioclimatic level and with major biomes at bioclimatic level. An advantage of the GBC over other bioclimatic classification systems is the inclusion of both seasonal and annual variations in those climatic parameters which are significant for the growth and development of plant populations and communities. GBC distinguishes several types of Mediterranean climate regimes for Iran and helps to differentiate between two different desert climate types i. e. Mediterranean and Tropical deserts in arid parts of the country. Because the climate in the Irano-Turanian region clearly differs from the Mediterranean region in its degree of continentality and seasonality, we propose the term ‘ xero-estival-continental’ or ‘Irano-Turanian’ instead of ‘Mediterranean’ bioclimate when describing the climate of continental Middle East and Central Asia.

Are environmental factors responsible for geographic variation in the sex ratio of the Greenlandic seed‐bugNysius groenlandicus?

AbstractUntil recently nothing indicated an unequal sex ratio in the widespread Greenland seed‐bugNysius groenlandicus(Zetterstedt) (Heteroptera: Lygaeidae). However, recently populations more or less devoid of males were discovered in high arctic Northeast Greenland. This initiated an inspection of the entire material of the species collected in Greenland and now preserved at the Zoological Museum, University of Copenhagen. It was found that the sex ratio varied significantly among different locations. In most cases females were most abundant, but males were either scarce or absent only in samples from Northeast Greenland, indicating that here the species reproduces asexually. This paper demonstrates that the differing sex distributions can be explained by climatic factors (temperature, precipitation) and that the degree of continentality (distance from the open sea) promotes female‐biased sex ratios.

Climate continentality and treeline species distribution in the Alps

The distribution of tree species and the elevation of the alpine treeline are strongly affected by climate continentality. In the present work we performed a detailed survey of the upper limits of tree vegetation in two areas with contrasting climate located in the central Italian Alps, in order to evaluate the structure of the treeline under different degrees of continentality. Tree and krummholz (stunted) individual position, their dimension and life form were recorded from the upper limit of the closed forest to the species limit. The results were compared with an estimation of tree species distribution at the treeline in the whole Lombardy Alps, performed by a survey of tree species occurrence in areas of known climatic traits. The structure of the treeline (upper limits, life form altitudinal arrangement) and its ongoing dynamics were different in the two areas: climate continentality assessed by hygric and thermal continentality indices influenced the distribution of some treeline species. Although the influence of human and geomorphologic disturbance could not be excluded, the importance of the degree of continentality must be stressed when evaluating the response of the treeline to past and present climatic change.

Longitudinal Differences in Scots pine Frost Hardiness

AbstractThe autumn frost hardiness of Scots pine (Pinus sylvestris L.) populations from Scandinavia (57°28’-68°54’ N, 13°00’-27°00’ E) and the Komi Republic in Russia (61°30’-64°20’ N, 49°10’-54°50’ E), and open pollinated families from a population in Komi (61°43’ N, 51°07’ E) were examined in artificial freezing tests with one-year-old seedlings. The aims were to estimate genetic variation in hardiness between families of Russian origin and to compare populations of Russian (continental) and Scandinavian (maritime) origins. The longitudinal distance between the Scandinavian and Russian seed sources was associated with a significant difference in climatic conditions. At latitude 63°N the degree of continentality (the difference between July and January monthly mean temperatures) was 23.7°C for longitude 15°E in Sweden and 35.2°C for longitude 54°E in Komi. The narrow-sense heritability of frost hardiness calculated for the Russian families was 0.22. This indicates relatively high genetic control of the trait, of similar magnitude as earlier shown for populations of Scandinavian origin. Both Scandinavian and Russian populations showed a strong clinal variation in frost hardiness, northern populations being the hardiest. In addition, Russian populations were more frost hardy than Scandinavian ones from corresponding latitudes and attained the same level of hardiness as Scandinavian populations from 4.1° latitude further north. The results indicate that the longitude or continentality of the origins of Scots pine populations is associated with adaptive pressures that have significant effects on hardiness and are distinct from photoperiodic effects. When enriching breeding or production populations by including populations from remote origins it is essential to recognize not only latitudinal origin, but also longitudinal origin or temperature regime, in order to match material to the planned utilization areas.

Radar Surveys on Scandinavian Glaciers, in Search of Useful Climate Archives

Ice cores obtained from cold glaciers are known to contain detailed archives on past climates. So far, no such data-set has been retrieved from Scandinavia, in part because most Scandinavian glaciers are largely of a temperate type, thus having a less well preserved climatic signal. However, within the more continental parts of the Scandinavian mountain range, glaciers often have a substantial cold surface layer in the ablation area. Past climate variations may be reconstructed from studies of crystallography and stratigraphy of ice from the cold surface layer. The thicknesses of such cold layers at two closely situated sites in northern Sweden have been mapped by a ground based high resolution radar. The best results were obtained by using the frequency interval 700-900 MHz. The two investigated glaciers Storglaciaren and Marmaglaciaren are situated 20 km from each other in an area with a strong east-west climatic gradient. The annual average air temperature is similar at the two sites, whilst the precipitation rate on Storglaciaren is almost double that of Marmaglaciaren. The radar soundings show that Marmaglaciaren has a significantly thicker cold surface layer, 65 m on average compared with 30 m on Storglaciaren. The difference is caused by less snow cover insulation from winter cold and less net ablation on Marmaglaciaren. The measured thicknesses of the cold surface layer therefore seem to correlate well with the degree of continentality at the sites. Radar sounding is a highly useful tool for locating glaciers containing a potential relatively well preserved climatic signal. Such glaciers may be found within the more continental parts of the Scandinavian mountain range.

The air temperature in cracow from 1826 to 1990: Persistence, fluctuations and the urban effect

AbstractMean monthly air temperatures in Cracow for the period 1826–1990 were used. The temperatures of the coldest (Tlow) the warmest (Thigh) periods of the year, and mean annual temperatures (Ta), were calculated. The persistence of temperatures was examined using the correlation coefficients between monthly temperatures in succeeding months. A significant temperature persistence was found for a cold season (December‐March) and also for the summer (July‐August). Long‐term fluctuations were analysed by means of 20‐year and 30‐year running mean values and the positive and negative squared deviations of moving 20‐year subperiods. Two warm stages were found. One at the beginning of the present century, the second at the end of the period analysed. The first warm phase was connected with a decrease in the degree of continentality. Warm phases were also linked with a decrease in the temperature variability.The spectrum and the moving spectrum in 40‐year subperiods of monthly and annual temperature records were calculated. An 8‐year period was found in Tlow, Ta, and in the monthly series of the cold season, and 4‐ and 5‐year periods were found in Thigh and in the monthly series of the warm season.By comparing the temperature in Cracow with that at the neighbouring stations of Wieliczka, Bochnia, and Tarnów, it was found that the difference in annual means increased from −0.3°C at the end of the previous century to 1.0°C in the last two decades. About 0.5°C of this increase occurred in the last 40‐year period of abrupt expansion and industrialization of the city of Cracow.

Raised channel systems as indicators of palaeohydrologic change: a case study from Oman

The aim of this paper is to determine the extent to which “raised” channel systems may be used as indicators of long-term paleohydrologic change, and hence of broader paleoenvironmental changes, in arid areas during the Cenozoic. The paper reviews the paleohydrologic significance of former drainage systems in arid areas, and demonstrates the application of paleohydrologic methods to the analysis of the long-term evolution of a complex series of exhumed, multistorey, raised channel systems in interior Oman. The paper discusses the range of possible autocyclic and allocyclic controls on changes in channel behaviour through time, as a means of establishing the paleoenvironmental significance of observed changes in paleochannel pattern, morphology, sedimentology and stability. The paper identifies some of the major allocyclic controls, including climatic changes, and particularly the seasonality, magnitude, frequency and distribution of rainfall events during the Cenozoic, together with the degree of continentality and hence the strength and persistence of arid wind systems. Base-level changes, due to eustatic fluctuations and/or tectonic activity, may also act to control long-term patterns of aggradation followed by large-scale landscaping lowering. However, long-term fan ageing associated with progressive aggradation and steepening of paleochannel systems, may also eventually lead to fanhead trenching, independent of any external controls. In addition, progressive expansion of the drainage network and resulting river capture, can lead to marked increases in water and sediment supplies to the fluvial system. The paper also emphasizes the difficulties involved both in differentiating the wide range of possible controls on paleohydrologic response, and also in developing an accurate and precise chronology for desert paleodrainage systems, and in their correlation with non-fluvial sedimentological sequences. The raised channel systems of interior Oman consist of heavily desert varnished chert-and/or ophiolite-rich gravels, dating from some time during the Plio-Pleistocene period. The paleochannels from sinuous gravel ridges rising <30 m above the surounding plains. At least 12 successive generations of superimposed paleochannel systems have been identified, representing major periods of fluvial activity, each of varying duration and character. The earlier generations form typically broad, sinuous, single-thread channels, comprising fine-grained, chert-rich gravels, emented by clear crystalline calcite, and associated with bankfull paleodischarges of up to 1400 m 3 s −1. The later generations become increasingly narrow, steep and less sinuous, with single-thread distributary channels which narrow rapidly downfan. The gravels are coarser grained and dominated by increasing concentrations of ophiolites. The latest stage is associated with fanhead entrenchment, and formation of terrace gravel sheets, poorly cemented by CaCO 3, and dominated by ophiolites. Peak paleoflows may have exceeded 13,000 m 3 s −1. The observed changes have resulted from a complex combination of both internally and externally generated environmental changes during the Cenozoic. Progressive extension of the drainage network on to the ophiolite massif of the mountain source area resulted in river capture and a concomitant increase both in paleodischarges and in supplies of ophiolitic sediments to the paleodrainage system. The early sinuous channels may have developed under a humid to sub-humid climate, in which perennial or seasonal flows allowed the distinct meander paleochannels to form. Ephemeral flows, characterized by flash flood regimes, were probably associated with the later distributary systems, which may reflect semi-arid to arid climatic conditions. The large-scale deflation of the interfluve sediments, which resulted in the eventual exhumation of the cemented, gravel-capped, multistorey paleochannel sequence, is also likely to have occurred during periods of marked continentality, probably during periods of low sea-level associated with the Quaternary glaciations.

Veronica beccabunga gliedert sich in drei vikariierende Unterarten

Summary 1. The 3 subspecies (subsp. beccabunga ; subsp. abscondita M. A. Fischer; subsp. muscosa (K orsh .) A.J elen .) differ mainly in the length of the peduncle of the raceme, the orientation of the pedicels, the size of the corolla, the length of the style; further but ± overlapping differential characters include mean leaf size, leaf margin, number of racemes per shoot, number of flowers per raceme, size and shape of capsule. (See Table 1 and Fig. 1!) 2. In most of the characters, subsp. beccabunga holds an intermediate position between subsp. abscondita and subsp. muscosa . 3. Intermediate populations between the subspp. seem to be very rare or completely absent. 4. The distribution ranges of the 3 subspp. are strikingly different with little overlapping (see Figs. 2 and 3): subsp. beccabunga is distributed in almost whole Europe, in S. Siberia (Altai mts.), W. and N. Turkey, W. Georgia, N. Soviet Armenia; — subsp. abscondita in S. and E. Turkey, N. and SW. (Adzharia) Georgia, most parts of Soviet Armenia, in Iraqi Kurdistan (northernmost mountainous border region of Iraq), NW. and N. (central Elburz mts.) Iran, and Lebanon; — subsp. muscosa in the NE. border region of Iran, in Afghanistan, Tadzhikistan, Kirgizia, at the SE. border of Kazakhstan, in N. Pakistan, Kashmir, NW. India, Nepal, the W. border region of Sinkiang. 5. The type of habitat seems to be the same in all subspp., the altitudinal range and the degree of continentality, however, are remarkably different, both low in subsp. beccabunga , higher in subsp. abscondita , and highest in subsp. muscosa (see Table 1). In the contact areas of subsp. beccabunga and subsp. abscondita , the former seems to inhabit lower, the latter higher altitudes.