Moss Banks Research Articles

Colonization by lichens and the development of lichen-dominated communities in the maritime Antarctic

Three long-term studies of lichen growth and colonization have been undertaken at Signy Island, South Orkney Islands, in the maritime Antarctic. Small individual thalli of several crustose species and uncolonized plots on 12 fresh rock surfaces were photographically monitored at intervals of 3–4 years over a period of up to 20 years. The development of Ochrolechia frigida colonies on a regenerating moss bank, recently uncovered by a receding glacier, was similarly monitored. The results indicate that many lichens growing in sites enriched by nitrogenous compounds derived from populations of sea birds, have relatively rapid colonization and growth rates. Mean percentage increase in thallus area can be as high as 15–32% per annum in some nitrophilous saxicolous species (e.g. Acarospora macrocyclos, Xanthoria elegans and species of Buellia and Caloplaca), but as low as 0.4–4% in nitrophobous species ( Lecanora physciella, Lecidea sp., Rhizocarpon geographicum). Umbilicaria antarctica and Usnea antarctica also yielded data indicating high growth rates, with colonist plants reaching several centimetres after 20 years. Colonization by mixed assemblages of lichens of new rock surfaces can attain 40–>90% cover after 20 years in nutrient-enriched sites, and even 20–25% in non-biotically influenced sites. Colonization by or increase in extant O. frigida on the regenerating moribund moss bank was also quite rapid. It is suggested that the exceptionally large thalli of several lichen species and the locally extensive dense lichen fellfield communities in the maritime Antarctic may be much younger than previously supposed.

Late Pleistocene and Holocene glacial history of James Ross Island, Antarctic Peninsula

Studies of Quaternary glacial stratigraphy and morphology around the Antarctic Peninsula have shown that James Ross Island in the western Weddell Sea probably has the best occurrences of stratigraphic sections with dateable material in the region. The stratigraphy includes sections with indefinite radiocarbon age, and three separate aminozones can be recognized. Except for indications of an early deglaciation around c. 10,000 BP, the field evidence from northern James Ross Island suggests a glacial readvance around 7000 BP. It is concluded that the readvance reflects the combined effects of eustatic sea level rise and Holocene warming, leading to increased precipitation and a positive mass balance. The most recent large‐scale deglaciation in the area took place around 6000–5000 BP. This confirms the evidence from lake sediments and moss banks in other parts of the Antarctic Peninsula region, which shows that, in most cases, the initiation of organic deposition took place after c. 6000 BP. The literature on the Holocene glacial and environmental history of the region is reviewed in light of the new field evidence.

Stratigraphic and Paleoclimatic Studies of a 5500-Year-Old Moss Bank on Elephant Island, Antarctica

Analyses of a core from the deepest known moss peat bank in Antarctica, on Elephant Island, South Shetlands, show that this Chorisodontium aciphyllum-dominated bank began to grow ca. 5500 14C yr BP. Combined with other studies in the region the present study indicates more extensive glaciation before 5000 to 6000 BP than today on some of the South Shetland Islands. The main hypothesis is that these frozen moss banks contain important paleoclimatic information. The stratigraphic parameters analyzed included degree of humification, organic and mineral matter content, bulk density, chronology, volumetric growth and organic accumulation rates, carbon and nitrogen concentrations, C/N ratios, nitrogen accumulation rates, and finally magnetic analyses to detect tephra horizons. A discussion of the interrelationships between these parameters is followed by theoretical calculations of annual net primary productivity combined with multivariate analysis of the data set. Results of the analysis show that three calculated productivity peaks coincide with three periods of milder and more humid summers, at 4150-3900, 3180-3030, and 2030-1840 BP. However, the period with possibly the warmest summers, 3180-3030 BP, is interpreted also to have been characterized by cold winters. The data suggest that the periods with the coldest summers (and possibly also winters) prevailed at the earliest stage of the moss bank development, at ca. 3500 BP, and 2500 BP.

Late Holocene tephrochronology of the northern Antarctic Peninsula

Andesitic and basaltic andesitic tephra layers are abundant in Holocene deposits from the Antarctic Peninsula. Visually discernible tephra horizons occur in three lakes on Livingston Island. Tephra in two other lakes and in a moss bank on Elephant Island, with very low ash concentrations, were detected magnetically. Deception Island is the most likely volcanic source for the tephra. With direct 14C dating, age/depth curves, and cross-correlations at least 14 tephra horizons dating to between ca. 4700 and 250 yr B.P. were identified and now form the basis for a preliminary regional tephrochronology that will be a valuable dating tool for investigating the Holocene climatic history of Antarctica.

Stratigraphic and Paleoclimatic Studies of a 5500-Year-Old Moss Bank on Elephant Island, Antarctica

Stratigraphic and Paleoclimatic Studies of a 5500-Year-Old Moss Bank on Elephant Island, Antarctica

The Food Storage Behaviour of the Northwestern Crow

The food storage behaviour of the Northwestern crow (Corvus caurinus) was investigated on Mitlenatch Island, British Columbia. The crows stored mostly intertidal food, especially clams, crabs, fish and worms, on the hillsides surrounding the intertidal beach. They also carried food to other parts of the island, presumably to be stored. Storage sites included, in decreasing order of importance, grass clumps, moss banks and the sides of rocks. The choice of substrate is discussed in relation to its camouflaging effect. Food items were most often carried and stored singly. Some individuals carried two items at a time. On average, it took a crow 24.9 sec to hide a food item. The crows stored food in exclusive and non-exclusive areas. Exclusive areas were defended and associated with a nesting territory, whereas non-exclusive areas were not, resulting in several birds using them. Food items were almost always covered and it was shown experimentally that this significantly reduced the chance that the cached item was stolen. The availability, abundance, profitability and preservation qualities of the stored food were discussed. Storage seems to result from a relative scarcity of non-intertidal food at high tide early in the breeding season. During this period too, females are forming and laying eggs, and may depend on the stored food at high tide. The success of 3-colour-ringed crows in relocating their food caches was 76%. The birds appeared to have memorized the location of their food stores. Olfaction appeared to be unimportant for the detection of experimentally-hidden clams. Experiments demonstrated that single stored clams were found more slowly than clumped ones. The problem of stored food decomposition was studied and discussed in relation to the short-term storage strategy.

The Formation of Vertical Edges on Antarctic Moss Peat Banks

Moss peat banks, which can be up to 3 m deep, greater than 2500 m2 in area, and up to 5000 yr old, occur in the Antarctic. Radiocarbon dates show that the peat accumulation rate has varied from 0.25 to 2.00 mm yr-1. These peat banks have an abrupt vertical edge of exposed peat, which does not appear to be due to erosion of a once-larger peat bank. These edges seem to have arisen because, as peat accumulates and the moss banks become deeper, increased snow-lie prevents outward growth of the banks at their edges.

The Rate of Peat Accumulation in Antarctic Moss Banks

(1) Three Antarctic moss banks were studied in detail: two dominated by Polytrichum alpestre Hoppe and one by Chorisodontium aciphyllum (Hook. f. et Wils.) Broth. (2) The rate of upward growth of the moss banks, 0.9-1.3 mm yr-1, is approximately half the annual shoot growth. (3) The amount of decomposition which has occurred at different depths of the peat in these banks was calculated from measurements of bulk density and compression. The decomposition rate appears to be < 1%Y yr-1. Peat 20-30 cm below the surface is permanently frozen, and about half the original material has decomposed by the time it becomes incorporated into this permafrost. Evidence is presented that a slow decomposition rate is an intrinsic characteristic of Polytrichum alpestre. (4) The rate of peat accumulation, 89-158 g m-2 yr-1, is about half the rate of production, 162-350 g m-2 yr-1. The former is similar to accumulation rates of peat elsewhere in the world.