Maja Lisowska

Lichen Diversity on Glacier Moraines in Svalbard

Abstract This paper contributes to studies on the lichen biota of Arctic glacier forelands. The research was carried out in the moraines of three different glaciers in Svalbard: Longyearbreen, Irenebreen and Rieperbreen. In total, 132 lichen taxa and three lichenicolous lichens were recorded. Eight species were recorded for the first time in the Svalbard archipelago: Arthonia gelidae, Buellia elegans, Caloplaca lactea, Cryptodiscus pallidus, Fuscidea kochiana, Merismatium deminutum, Physconia distorta, and Polyblastia schaereriana. One species, Staurothele arctica, was observed for the first time in Spitsbergen (previously recorded only on Hopen island). All the studied glaciers lie in Spitsbergens warm region. However, Kaffiøyra Plain, where Irenebreen is located, is characterized by higher levels of humidity, which may explain its different lichen composition compared to that of the other two moraines. The forelands of Rieperbreen and Longyearbreen are located in the same area of Svalbard, which is also the warmest and the driest and where high species diversity is expected. This proved to be true for the Rieperbreen moraine, but not for the Longyearbreen moraine, where species diversity was lowest. The expansion of tourism along Longyearbyen appears to be a major factor behind the poor development of lichen biota on the Longyearbreen moraine.

Components of the Natural Environment

Western Sorkapp Land geological structure is very varied. Pre-Quaternary bedrock consists of three complexes: (1) the most extensive rocks from the Middle Proterozoic to the Silurian, folded in the Caledonian Orogeny: dolomites, phyllites, schists, quartzites, limestones, sandstones, breccias, and others; (2) Early Carboniferous clastic sediments: sandstones, including quartzitic sandstones, siltstones, and shales; and (3) Triassic sedimentary rocks: sandstones and conglomerates. None of these complexes lies horizontally. Loose Quaternary deposits (marine, glacial, fluvial, organic, frost-weathering, slope, including talus and solifluction) are not continuous. The climate is Arctic and marine-type. Average annual temperatures vary from −9 to −3 °C there. Average annual precipitation totals reach 300–500 mm. The mountains in northwest Sorkapp Land remain free of glaciers due to their exposure to relatively warm and dry eastern foehn winds. All the lowlands are unglaciated too. Sorkapp Land glaciation is clearly Arctic-type for two reasons: the common presence of permafrost, and the very weak influence of altitude on the distribution and extent of glaciers. The principal landform types in western Sorkapp Land are coastal lowlands, mountains, and mountain valleys. Nonglacial rivers and lakes (supplied directly by atmospheric precipitation and an active layer of permafrost) play an important part. There are also karst springs and glacial rivers and lakes in the northeast and southeast of the study area. Typically for the High Arctic, the flora of western Sorkapp Land is dominated by cryptogams, mainly lichens—about 170 species—whereas vascular plant flora includes 82 species. Different vegetation types often create complex mosaics, following diverse habitat conditions (bedrock, terrain relief, hydrology, etc.). In a few places the presence of seabird colonies has a local but strong impact on the vegetation.

Conclusions and Prognosis for Environmental Change

The first and direct result of climate warming has been glacial recession, which stimulated an entire process of landscape (and seascape) changes along the eastern boundary between western Sorkapp Land (devoid of glaciers) and the glaciated peninsula interior. A completely new landscape has appeared there. Also fore-fields of glaciers have been indirectly influenced by the glaciers’ retreat. Some sequences of non-glacial and non-postglacial coastline have been affected by an increase in the geomorphic activity of the sea due to a shorter sea-ice season. During the next few decades, the described trend of environmental-landscape transformation will continue unless the climate cools down. In the case of a progressive warming, the extensive tongues of big glaciers will first retreat and then disappear. The main result of that would be an expansion of non-glacial landscape, vegetation and animal life to the east, into the currently glaciated peninsula’s interior. On the basis of repeated vegetation mapping, significant changes in composition and extent of several plant communities were documented. Decrease in species diversity, leading to a more uniform vegetation, has been observed mainly in dry habitats. In some cases boundaries between plant communities that were clear in the 1980s, have now vanished. Fruticose epigeic lichens, like Flavocetraria nivalis, Cladonia rangiferina, and other species of Cladonia have disappeared from the most part of the study area and their extent is now limited to steep rocky slopes. In some communities increase in abundance of Salix polaris was recorded. The main cause of vegetation changes in Sorkapp Land is the rapidly growing reindeer population in the area.

Environmental and Landscape Changes

Climate changes in western Sorkapp Land mirror global fluctuations. The Little Ice Age ended with a cold period in the 1890s. A warm contemporary period began in the early twentieth century. Afterwards, secondary cold and warm climate fluctuations occurred. The most recent fluctuation, since the 1980s, shows a significant warming trend. The mean annual temperature increased by almost 2 °C and the mean annual total precipitation increased by about 60 mm since the 1980s (according to data of the station located 10 km from the study area). Almost all the snow patches melt during the warmest and sunniest summer seasons. The so-called active layer of permafrost had doubled at sites below 100 m of altitude from the 1980s to 2008. Almost all Sorkapp Land glaciers have undergone a continuous recession since the beginning of the twentieth century. Two processes are important for glacier recession: decrease in snow accumulation in firn fields due to the summer thawing of a larger snow mass, and summer thawing of ice on the surface of glacier tongues, which results in a decrease in ice thickness. Thus, the equilibrium-line altitude of a glacier shifts upward, reducing the accumulation zone. Hence, the entire surface of the glaciers undergoes lowering each year, which results in a decrease in their volume and their overall retreat. Since the 1980s, an acceleration of the glaciers’ recession has occurred, causing great changes in landforms and Quaternary. New accumulation landforms appeared in the front of glaciers and around glacier tongues in their marginal zones, that is, on lowlands and valley floors abandoned by glaciers and in their forefields situated below the marginal zones (i.e., beyond the former extent of the glaciers). New erosion landforms, apart from proglacial river incisions, prevail on the steep slopes of valleys and mountain massifs. The cliffs of tidewater glaciers undergo the quickest retreat. Karst processes have intensified due to higher air temperatures and larger quantities of flowing water. Surface and underground streams carry much more water today than in the 1980s. However, the soil is generally drier on the lowlands between the streams today due to the deepening of the active layer above the permafrost. The river and lake network changed the most due to glacier recession. Ice-dammed lakes disappeared due to the recession of glaciers. On the basis of repeated vegetation mapping, significant changes in composition and extent of several plant communities were documented. Decrease in species diversity, leading to a more uniform vegetation, has been observed mainly in dry habitats. In some cases boundaries between plant communities that were clear in the 1980s have now vanished. Fruticose epigeic lichens, such as Flavocetraria nivalis, Cladonia rangiferina, and other species of Cladonia have disappeared from the most part of the study area and their extent is now limited to steep rocky slopes. In some communities increase in abundance of Salix polaris was recorded. The main cause of vegetation changes in Sorkapp Land is the rapidly growing reindeer population in the area.