Studies of Classification, Biomass, and Microclimate of Vegetation Near
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ticus Willem, a collembolan, Belgica antarctica Jacobs, local terrestrial ecosystem, and (3) to investigate the a wingless midge, and Alaskozetes antarcticus (Mich- environmental adaptations of one species, the cosmo- ael), a large orbatit mite. politan moss Bryum argenteum, through studies of In the previous summer (1970-1971) Mr. Dunkle growth and reproduction in relation to microclimate. gathered respiration data only on Cryptopygus. This Observations were made on exposed ground near the year, he obtained Q02s on all three species at tem- southern end of Hut Point Peninsula, near Caughley peratures ranging from 00 to 20°C. For biomass de- Beach, at Turks Head and at Horseshoe Bay on the termination we extracted the insects from 274 separate west coast of Ross Island, and on the mainland at plant samples. An optical scanner is now being used Cape Bernacchi, Gneiss Point, Hobbs Strand, and to count the insects and sort them into size classes. near the western shore of Lake Fryxell in Taylor Approximately 2 grams (dry weight) of both Cryp- Valley. topygus and Belgica were returned to Davis for calori- A tentative classification of the plant communities metric determinations. We also collected 76 plant encountered in these areas is presented in table 1. The samples, mainly lichens, which will be used for calori- communities dominated by lichens or algae can readily metric determinations. be accommodated within three subformations of the Antarctic Non-Vascular Cryptogam Tundra Forma- Mr. Marsh initiated a study on the feeding rates of tion previously recognised in the maritime Antarctic, the three species under consideration. An isotope while several associations and even sociations are com- (cesium-134) was incorporated in their food, and the mon to the two regions. The bryophyte communities rate at which the isotope accumulated is a measure of present greater problems owing to the widespread their ingestion rates. All unused cesium- i 34 was retro- occurrence of short turf forming species of Bryum. graded to the University of California, Davis; the The other principal bryophyte community comprises waste material was turned over to the Navy for dis- cushions of Sarconeurum glaciate, often heavily en- posal. Although no isotopes were used in the field, the crusted with lichens such as Caloplaca darbishirei, station and surrounding grounds were monitored bi- and this could be placed in the Encrusted Moss Sub- weekly for background radiation. These records were formation. As an alternative, however, it is proposed sent to the National Science Foundation, Office of that all the present bryophyte communities, together Polar Programs. with the Encrusted Moss Subformation and possibly The principal investigator departed Palmer on certain essentially bryophytic vegetation from the R/V Hero on January 28; Marsh, Dunkle, and Boussy Fruticose Lichen and Moss Cushion Subformation, returned with Southwind, leaving Palmer on February should be combined into a new Short Moss Turf and 25, 1972. Cushion Subformation. The work was supported under National Science In terms of growth form, the plant communities Foundation grant GV-24329. recorded near McMurdo Sound in general appear to resemble those occupying the drier, more exposed habitats available in the maritime Antarctic, but with Studies of classification, Table 1. Plant communities recorded near McMurdo Sound. biomass, and microclimate Antarctic Non-Vascular Cryptogam Tundra Formation of vegetation near McMurdo Sound Crustaceous Lichen Subformation aCaloplaca spp association aCaloplaca elegans sociation R. E. LONGTON Other sparsely developed communities as yet unclassi- Department of Botany fied University of Manitoba, Winnipeg, Canada Fruticose Lichen and Moss Cushion Subformation aAndreaea spp—Usnea spp association aUsnea antarctica—socjatjon Plant ecological investigations were carried out by Usnea antarctica—Omphalodiscus decussatus sociation the author from McMurdo Station, southern Victoria Short Moss Turf and Cushion Subformation Bryum spp association Land, between December 6, 1971, and January 6, Bryum antarcticum sociation 1972. The objectives were (1) to determine whether Bryum argenteum sociation a vegetation classification developed in the maritime Sarconeurum glaciale—Caloplaca darbishirei association Antarctic (Longton, 1967; Gimingham and Smith, Alga Subformation 1970) could be extended for use at a continental ant- aPrasiola crispa association Other communities as yet unclassified arctic site, (2) to obtain preliminary determinations of the biomass of bryophyte communities as a contribu- aAssocjations and sociations recorded in the maritime Antarc- tion towards an understanding of the dynamics of the tic by Gimingham and Smith (1970). 86 ANTARCTIC JOURNAL considerably lower total plant cover and proportion- equals 0.75 percent of dry weight, mean percentage ally greater representation of algal communities and cover equals 1.4 percent, mean loss on ignition of 20 short moss turfs. These observations, together with cores corrected for contribution from soil organic mat- descriptions of vegetation elsewhere in continental ter (LI - S) equals 0.3755 gram (±.0141 SE), Antarctica (Siple, 1938; Perkins, 1945; Rudolph, community biomass equals 14.1 grams per square 1963; Bowra et al., 1966), thus suggest that it may meter assuming an ash content of 10 percent. prove possible to adapt the earlier classification to The studies on growth and reproduction in Bryum include the macroscopic terrestrial plant communities argenteum form part of a recently initiated investiga- of Antarctica as a whole. tion of the eco-physiology of populations from a vari- The Bryum spp communities range from scattered ety of environmental regimes, along the lines of pre- small stands less than 5 centimeters wide to occasional, vious work on Polytrichum alpestre (Longton, 1972). almost continuous swards extending over several me- The most detailed observations were made on a ters. The turfs are up to 4 centimeters deep, but the population at Cape Armitage. Biomass sampling was erect shoots are usually chlorophyllose only in the up- carried out on two occasions 19 days apart, and per 1 to 2 millimeters. Below this depth most of the additional small samples were collected at intervals of leaves and stems are pale brown in color and densely approximately 5 days to permit determination of the interwoven with rhizoids. However, when portions of pattern of growth and the development of any game- turf were moistened, placed with the stems horizontal, tangia present. Microclimate data also were collected and enclosed in a Petri dish at approximately 20°C. during a 27-day period using thermistors and a Grant in continuous light, secondary protonema and leafy Instruments (Developments) Ltd nine-channel re- buds developed freely from both stem and rhizoid corder to obtain temperature reading to the nearest tissue to the base of the profile. Biomass can there- 0.5°C. at 15-minute intervals, a Kipp and Zonen fore be assessed from the dry weight of turf in known solarimeter with a Rustrak model 288 recorder to area samples. This was estimated from data for loss give a continuous record of solar radiation, and a on ignition, as it was impossible to separate the dense Casella 7-day hair hygrograph placed on the surface wefts of rhizoids from their sandy substratum. of a Bryum argenteum turf for continuously monitor- A 2.3-centimeter-diameter cork borer was used to ing relative humidity. Radiation and humidity were take a total of 105 samples to the base of Bryum spp read off the charts at 7.5- and 30-minute intervals re- turfs at four sites. Dry weight and loss on ignition spectively, and these data, together with the tempera- after 16 hours at 550°C. were determined for the ture records, are being analyzed using a computer moss turf and adhering soil comprising each core, and program giving the following breakdown of each days also for two or three soil samples collected immediately results: mean daily value, mean value for each of 12 below the moss turfs at each site. Biomass can then be successive 2-hour time intervals (i.e., 0001 to 0200 determined from: hours, 0201 to 0400 hours . 2201 to 2400 hours), and percentage of readings each day within successive Community biomass per m2 = 5°C. increments, the increment around 0°C. being (LI - S) x 104 x C +B divided into two. These data can, in addition, be A x 102 averaged over a specified number of days, and mean where LI is loss on ignition per core, S is the contribu- daily maximum, minimum, and overall mean values tion to LI from the organic content of soil within the computed. The analysis was based on local time. core, A is the surface area of the core in square centi- Some results are illustrated in the figure and table meters, B is a correction factor for ash content of the 2. The figure shows a vertical temperature profile, moss, and C is percentage cover. An estimate of S based on data for the 12 daily time intervals aver- can be obtained from the weight of the residue re- aged over 5 days. The data show many of the ex- maining after igniting each core and the percentage pected features, including wide diurnal fluctuation loss on ignition of the soil samples, while C was de- just below the surface of the moss turf, and suggest termined in the field at each site, usually by the line that temperatures above 8°C. prevailed at this level intercept method. B is unknown, but previous work for substantial periods during the afternoons. This suggests that the ash content of mosses normally ranges is confirmed in table 2, which indicates that although from 5 to 15 percent of dry weight (Shacklette, 1965). 45 percent of the plant level reading during the Although admittedly crude, this method should same period were within the range 0.0 0 to 2.50C., provide, for the first time, reasonable estimates of the 22 percent of the records, representing an average biomass of some terrestrial communities in continental of approximately 5 hours per day, were between Antarctica.