Mosaic vegetation characteristic of the prehistoric lava fields of the «Hekla» area near Galtaleakur, Iceland (original) (raw)
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Vegetation on lava fields in the Hekla area, Iceland
1991
The vegetation development on 13 dated historical lava fields around the volcano Mt. Hekla is described. The lava fields have been divided into three main topographical categories, the main surface, holes and crags. The investigation was concentrated on the main surface at 22 sites in the 11 oldest lava fields, the oldest from 1 158, the youngest from 1947. At each site the topography, substrate (profile, pH and loss on ignition), flora and the physiognomy and the floristical composition of the vegetation were studied. Local climatic conditions (temperatures) are described for one lava field. The vegetation description included a floristic inventory, quantitative analyses (releves) of the vegetation both of permanent and non-permanent plots, drawings and photographic documentation. The total number of analyses made were: 1566 for the main surface, 81 for the holes and 13 for the crags. At each site the fo llowing abiotic factors were recorded: (a) the irregularity of the topography, (b) the age of the lava field, (c) the elevation, (d) the number of deposited tephra falls, (e) the quantity of deposited aeolian material between the tephra layers, (f) the cover of tephra and (g) the surface roughness was judged for every plot. In studies of the colonization of plants in the youngest fields records were also made of: (a) the position within the layer of clinkers, (b) the microsurface (texture) of the lava blocks and the age ofthe lava field when the analyses were carried out. The analyses made ofthe main surface were treated with the clustering and relocation program TABORD and with the ordination program Canonical Correspondence Analysis (CCA, CANOCO program). First, local clusters were obtained for each of the lava fields. These primary clusters were then clustered again to obtain a set of second-order clusters. The CANOCO results were used to check whether the second-order clusters were ecologically and floristically homogeneous or needed to be subdivided. The classification results were compared with vegetation types described earlier. Due to the phytosociologically incomplete floristic composition of many clusters an ad hoc typology was used with three hierarchical levels: communities, variants and facies. Eleven communities, some variants and facies are described and their distribution interpreted in terms of the prevailing environmental conditions. The dynamics of the vegetation in the historical lava fields is in the Hekla area, Iceland.-Acta phytogeogr. suec. 77, Uppsala. 110 pp.
The Pleistocene Floras (2.4-0.8 Ma) - Shaping the Modern Vegetation of Iceland
Late Cainozoic Floras …, 2011
The Pleistocene vegetation history of Iceland is closely linked to the onset of large scale northern hemisphere glaciations. The first regional glaciation in Iceland occurred at ca 2.5 Ma (Praetiglian), just before the deposition of the oldest Pleistocene plant-bearing sediments in Iceland (Brekkukambur Formation, 2.4-2.1 Ma). Both the macro-and microfloras of the Brekkukambur Formation are not very well preserved and do not allow detailed interpretations of the palaeoenvironment. However, based on plant and insect remains from the coeval Kap København Formation of northern Greenland, this time marked a last phase of global warmth with boreal forests extending as far north as 82°N. Younger plantbearing sedimentary formations in Iceland investigated here are ca 1.7, 1.1, and 0.8 Ma in age. They were deposited during interglacials and their floras are very similar to the modern flora of Iceland. It is unclear at the moment whether and how frequently plants survived in Iceland during cold phases. Dispersal mechanisms of plant taxa found in interglacial deposits show that all of them are dispersed by wind or birds over long distances and hence Iceland could have been re-colonized within a rather short period after each cold phase. The composition of the modern flora of Iceland is the result of the dispersal modes and climatic tolerances (competitiveness) of its members. These general conditions appear to have controlled the flora and vegetation of Iceland in a similar way since more than 1.7 million years.
Progress in Physical Geography: Earth and Environment
Lava flows pose a hazard in volcanic environments and reset ecosystem development. A succession of dated lava flows provides the possibility to estimate the direction and rates of ecosystem development and can be used to predict future development. We examine plant succession, soil development and soil carbon (C) accretion on the historical (post 874 AD) lava flows formed by the Hekla volcano in south Iceland. Vegetation and soil measurements were conducted all around the volcano reflecting the diverse vegetation communities on the lavas, climatic conditions around Hekla mountain and various intensities in deposition of loose material. Multivariate analysis was used to identify groups with similar vegetation composition and patterns in the vegetation. The association of vegetation and soil parameters with lava age, mean annual temperature, mean annual precipitation and soil accumulation rate (SAR) was analysed. Soil carbon concentration increased with increasing lava age becoming co...
Late Cainozoic Floras of Iceland
Topics in Geobiology, 2011
The Topics in Geobiology series covers the broad discipline of geobiology that is devoted to documenting life history of the Earth. A critical theme inherent in addressing this issue and one that is at the heart of the series is the interplay between the history of life and the changing environment. The series aims for high quality, scholarly volumes of original research as well as broad reviews. Geobiology remains a vibrant as well as a rapidly advancing and dynamic field. Given this field's multidiscipline nature, it treats a broad spectrum of geologic, biologic, and geochemical themes all focused on documenting and understanding the fossil record and what it reveals about the evolutionary history of life. The Topics in Geobiology series was initiated to delve into how these numerous facets have influenced and controlled life on Earth. Recent volumes have showcased specific taxonomic groups, major themes in the discipline, as well as approaches to improving our understanding of how life has evolved. Taxonomic volumes focus on the biology and paleobiology of organisms-their ecology and mode of life-and, in addition, the fossil record-their phylogeny and evolutionary patterns-as well as their distribution in time and space. Theme-based volumes, such as predator-prey relationships, biomineralization, paleobiogeography, and approaches to high-resolution stratigraphy, cover specific topics and how important elements are manifested in a wide range of organisms and how those dynamics have changed through the evolutionary history of life. Comments or suggestions for future volumes are welcomed.
Vegetation history since the mid-Holocene in northeastern Iceland
Écoscience, 2018
Palynological analysis of peat cores collected near two abandoned farms in the Svalbarðstunga Valley of the Þistilfjorður region of northeastern Iceland was used to reconstruct the mid-Holocene vegetation history and to distinguish climatic and anthropogenic impacts on terrestrial ecosystems since colonization. The first site, Hjálmarvík, is located along the coast of Þistilfjorður, while Kúðá is located 12 km inland. From 6430 to ca. 4500 cal BP, shrub tundra and birch woodland dominated the landscape. Between ca. 4500 and ca. 1170 cal BP, cooler and wetter conditions favored peatland species, while birch significantly declined. From 1170 cal BP to the present, grassland and peatland were prevalent. Birch woodland had virtually disappeared from the inland regions by 5810 cal BP and from the coast by 3450 cal BP. However, isolated trees persisted in certain areas. Following the initial Norse settlement of Svalbarðstunga at about 1000 AD, the development of agriculture and sheep grazing promoted the spread of sedges and facilitated the introduction of new plant species. Ecological changes linked to the Norse landnám were more limited in Svalbarðstunga than elsewhere in Iceland, where abrupt changes such as woodland clearance and erosion have been associated with human settlement.
Late Cainozoic Floras …, 2011
The oldest plant fossils currently known from Iceland are ca 15 Ma, their deposition coinciding with the Mid-Miocene Climatic Optimum. At this time, forests in Iceland were dominated by mixed broadleaved deciduous and coniferous taxa with a few broadleaved evergreen genera such as Rhododendron and Ilex. Lowland forests were dominated by Glyptostrobus. Questions about the colonization history of Iceland or proto-Iceland are of particular interest since not much is known about the availability of effective land bridges allowing for colonization from Europe and/or North America at that time. In addition to geological data, in this chapter we use two lines of biological evidence to speculate about the early colonization of Iceland. First, we will examine the biogeographic patterns of key taxa such as Cryptomeria, Rhododendron ponticum-type, and Fagus friedrichii. Then we look at dispersal modes found in early colonizers of Iceland. Dispersal modes of at least some taxa indicate that Iceland was connected to the adjacent continents at the time of colonization. However, it cannot be determined when exactly this early colonization happened. The taxa recorded in the oldest sedimentary rocks in Iceland may have had different origins, either representing elements that were already present in the region since the Palaeogene or colonizing proto-Iceland from