Antarctic terrestrial ecosystems: The Vestfold Hills in context

Antarctic terrestrial ecosystems are briefly described, with emphasis on Signy Island in the maritime antarctic region, and the McMurdo oasis, southern Victoria Land, and Vestfold Hills in the continental antarctic region.As the largest and best known coastal ice-free oasis, the Vestfold Hills contain excellent examples of terrestrial sublithic, epilithic, chasmoendolithic, epiphytic and terricolous algal communities, as well as epilithic, endolithic, and epiphytic lichen communities, and moss communities. Many of the numerous lakes support dense communities of aquatic algae.     

Photochemical reactions of chlorophyll in dehydrated Photosystem II: two chlorophyll forms (680 and 700 nm)

Lichens and phototolerant poikilohydric mosses differ from spinach leaves, fern fronds or photosensitive mosses in that they show strongly decreased F_o chlorophyll fluorescence after drying. This desiccation-induced fluorescence loss is rapidly reversible under rehydration. Fluorescence emission from Photosystem II at 685 nm was decreased more strongly by dehydration than 720 nm emission. Reaction centers of Photosystem II lose activity on dehydration and regain it on hydration. Heating of desiccated lichens increased F_o chlorophyll fluorescence. The activation energy for the reversible part of the temperature-dependent fluorescence increase was 0.045 eV, which corresponds to the energy difference between the 680 and 697 nm absorption bands. In desiccated chlorolichens such as Parmelia sulcata, heating induces the appearance of positive variable fluorescence related to the reversible reduction of Q_A due to overcoming the energy barrier. This is interpreted to provide information on the mechanism of photoprotection: energy is dissipated by changing Chl680 or P680 into a chlorophyll form, which absorbs at 700 nm and emits light at 720 nm (Chl-720 or P680(700)) with a low quantum yield. Dissipation of light energy in this trap is activated by desiccation.     

Pathological traits observed in a historic Great Basin Native American Indian Skeleton

During the excavation of an irrigation ditch in Churchill County, Nevada, a burial was encountered, with associated artifacts indicative of historical provenience. The pattern of occlusal attrition, the lack of dental work, and the skeletal morphology indicate the individual was a Great Basin Native American Indian. Sex determination was female and age at death estimated as 40±. The skeleton is nearly complete and several of the long bones, as well as the vertebrae, scapulae, sternum and xiphoid process have minor pathologies, either osteophytic growths or areas of porosities and pitted appearances. The left sacroiliac joint is extensively affected by an unusual pathology, with the auricular surfaces of both the sacrum and ilium having a scooped out or hollowed appearance. Although the other pathologies are interpreted as being related to both age and possibly the lifestyle of a female Great Basin Indian during historic times, the sacroiliac pathological condition is construed as a manifestation of a more severe affliction.     

Effects of perennial neighbors and nitrogen pulses on growth and nitrogen uptake by Bromus tectorum

An experiment was conducted to determine if growth and biomass responsesof the annual grass Bromus tectorum are affected by themagnitude and timing of nitrogen (N) pulses and if these responses areinfluenced by different perennial neighbor species. Nitrogen(NH₄:NO₃) was applied in three pulse treatments of varyinginterpulse length (3-d, 9-d, or 21-d between N additions). The total amount of Nadded was the same among treatments; hence, both the frequency and magnitude ofN pulses varied (i.e., the longer the interpulse period,the greater the amount of N added for a single pulse).Bromus showed little response to the different N-pulsetreatments. The only characteristic that varied among pulse treatments wasspecific leaf area (SLA), which was significantly greater whenBromus was grown under the 21-d N pulse than when grownunder the 3-d or 9-d N pulses. Bromus height, leaf andtiller numbers, leaf area and aboveground biomass were not affected by theN-pulse treatments nor were tissue-N contents and concentrations. However,Bromus production and tissue-N were significantly differentwhen Bromus was grown with different perennial neighborspecies. Tiller production, aboveground biomass, and seed numbers ofBromus were lowest when the perennial neighbor was thetussock grass Agropyron desertorum, intermediate when theneighbor was the evergreen shrub Artemisia tridentata, andgreatest when the neighbor was the deciduous shrub Chrysothamnusnauseosus. N contents of Bromus leaves were alsolowest when the neighbor was Agropyron. In contrast, root Nuptake capacities were greatest for Agropyron-Bromus rootmixes and lowest for Chrysothamnus-Bromus root mixes. Theseresults suggest that perennial neighbors affect growth, seed production, and Nuptake of Bromus to a greater extent than the timing andmagnitude of N pulses.     

Dental modifications and tool use in the western Great Basin

Nondietary function is an important concern in the study of the human dentition and its role in adaptation. The purpose of the present investigation is to describe and interpret a pattern of dental wear in the anterior dentition of precontact hunter-gatherers that inhabited the western Great Basin. These data are discussed in light of ethnographic documentation as a means by which the archaeological record is linked with associated behavior of the representative populations. A series of 171 dentitions from a group of archaeological localities was examined. Of 1,931 teeth observed, 16 of these showed narrow (0.4-2.0 mm) transverse grooves located on the midocclusal surfaces of anterior teeth. The grooves were restricted in occurrence to five older adult males. Documentation of prehistoric and historic western Great Basin aboriginal populations indicates an adaptation that involves use of plant materials in the production of a variety of utilitarian objects, such as fish nets, basketry, funerary bags, fowling bags, and rope. In postcontact contexts, the anterior dentition has been shown to play an important role in the preparation of materials used for the production of this equipment. It seems most likely, then, that the grooves observed herein resulted directly from the use of the dentition as part of the tool assemblage for the production of other tools.     

Ecosystem integrity in the Great Lakes Basin: an historical sketch of ideas and actions

The concepts of ecosystem and integrity effectively entered the binational political arena in the Great Lakes Basin in the early 1970's. They were brought together explicitly in the statement of the purpose of the 1978 Great Lakes Water Quality Agreement. The 1987 Protocol to that Agreement has helped to specify the practical meaning of ecosystem integrity of the Great Lakes Basin. The proceedings of a binational workshop in 1988, titled An Ecosystem Approach to the Integrity of the Great Lakes Basin in Turbulent Times, helped to clarify the conceptual meaning. An Ecosystem Charter for the Great Lakes-St. Lawrence River Basin was proposed in 1989 to help achieve more thorough implementation of the commitment to ecosystem integrity. The evolutionary emergence of this political concept and related practice is described in the paper.List of abbreviations used in the text CUSIS Canada-U.S. Inter-University Seminar Series - LAA Environmental Lakes Area - EPA Environmental Protection Agency - GLBC Great Lakes Basin Commission - GLC Great Lakes Commission - GLER Great Lakes Ecosystem Rehabilitation - GLFC Great Lakes Fishery Commission - GLSAB Great Lakes Science Advisory Board - GLU Great Lakes United - GLWQA Great Lakes Water Quality Agreement - HASP Heritage Area Security Plan - IBP International Biological Program - IJC International Joint Commission - IZAP Inundation Zone Adaptive Plan - LAMP Lake-wide Management Plan - LLRS Lake Levels Reference Study - MAB Man and the Biosphere program - NEPA National Environmental Policy Act - PLUARG Pollution from Land Use Activities Reference Group - RAP Remedial Action Plan - SCOL Salmonid Communities in Oligotrophic Lakes - SGLFMP Strategic Great Lakes Fishery Management Plan - SPOF Strategic Plan for Ontario Fisheries - UNESCO United Nations Educational, Scientific and Cultural Organization Aquatic Ecosystem Health and Management Society. Symposium at the University of Waterloo, July 23–25, 1990.     

The effect of single and combined pollutants on lichen water content

The effects of lead, sodium chloride and sulphur dioxide, single and combined, on water content ofHypogymnia physodes (L.)Nyl. andXanthoria parietina (L.) Th. Fr. were studied. Lead, sodium chloride and their combinations, reduced water content in lichens, this reduction being partially correlated with the decrease of pollutant-influenced photosynthesis.     

Geomicrobiological Changes in Two Ephemeral Desert Playa Lakes in the Western United States

The geochemistry and microbiology of two ephemeral playa lakes in the Western United States, Surprise Valley Alkali Lake (SVAL) and Eldorado Playa (EP), were examined over one wetting cycle, revealing dramatic temporal changes in suspended mineralogy, aqueous chemistry, and bacterial populations. In SVAL the predominant suspended mineral changed from smectite to vermiculite and clinoptilolite, which led to a depletion of soluble Mg²⁺. Nitrate became depleted in both playas as a result of biological nitrogen demand imparted by unusually dense microbial communities reaching ～1 × 10⁸ cultivable heterotrophs per ml of water. One hundred eighty eight bacterial isolates were obtained, representing sixty phylotypes and four phyla: Actinobacteria, Bacteroidetes, Proteobacteria, and Firmicutes. Phylogenetic analyses suggested that the microbial communities reflected different phases of succession, with SVAL changing from a diverse community with abundant Yonghaparkia to a less diverse late summer community with abundant Bacteroidetes and Proteobacteria such as Loktanella, Rhodobaca, Saccharospirillum, Flexibacter, and phylogenetically novel members of the Flexibacteriaceae. In EP, a diverse assemblage of bacteria often associated with soils was replaced very quickly by a much less even community dominated by Yonghaparkia, Sandarakinorhabdus, and relatives of Belliella baltica. Strikingly, the early summer microbial community from SVAL was not significantly different from the EP community that developed within one week of flooding, even though these playas are almost 1000 km apart, whereas sympatric communities in different phases of succession were different. To our knowledge, this is one of the first geomicrobiological studies of a recharge playa, the dominant playa type worldwide.