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The present article explores the structure of and recent developments in research activities in the polar regions. Based on a bibliographic study of published papers indexed in the ISI Web of Science during the period 1981–2007, we have analyzed trends in publication, scientific disciplines and subdisciplines, coauthorship, and international collaboration within the field of polar research. We have uncovered several rather striking trends. Scientific output in terms of refereed publications has increased far more rapidly in polar research compared to science in general, quadrupling rather than doubling over the surveyed period. There is a nearly 1∶1 ratio between papers covering the Arctic relative to the Antarctic, with the vast majority within either the geosciences (40%) or biology (33%). There has been particularly a steep rise in the number of climate-related papers. The U.S.A. is by far the largest contributor to polar research on both the Arctic and the Antarctic, followed by Canada, the U.K., Germany, Norway, and Russia. The number of coauthored papers has grown markedly, reflecting geopolitical shifts and changing national and international funding priorities during the period. We believe our publication-based survey reveals interesting developments in scientific activities and international cooperation in general, and in polar science strategies and priorities in particular.
The Arctic is extremely vulnerable to projected climate change, and global warming may result in major community reorganizations. The aim of this study was a thorough investigation of plant biomass production throughout an entire growing season in five different high arctic vegetation types: Cassiope, Dryas, and Salix heath, grassland, and fen. The main focus was on the gross ecosystem production (GEP), and the biotic and abiotic factors which may influence GEP. Photosynthesis, aboveground biomass, and carbon, nitrogen, and chlorophyll content were measured weekly during nine weeks.
There were large differences in seasonal growth and production within and among vegetation types. Mosses contributed considerably to the total C and N pool in grassland, fen, and Salix heath. Fen, which had the highest pool of leaf N, leaf chlorophyll, and moss N, was the most productive vegetation type in terms of GEP, despite the lowest total biomass. Across vegetation types, leaf biomass, leaf N, and moss N pool size influenced GEP. Within most vegetation types GEP correlated with leaf N, in correspondence with the notion that N may limit plant production in many high arctic ecosystems. The timing of the peaks in C and N pools in leaves did not coincide with that in the mosses and in woody tissues. This emphasizes the importance of sampling throughout the growing season, when using field data from the Arctic to estimate plant biomasses and modeling C and N fluxes and pool sizes.
The Northern Patagonia Icefield (NPI), covering 3953 km2, is the second largest temperate ice body in South America. Despite its importance as a climate change indicator because of its location and size, data on ground-based mass balance and meteorological records for the analysis of glacier (snout) variations are still lacking. The use of multitemporal satellite images to estimate equilibrium line altitude variations could be a surrogate for such analyses. Since late-summer snowlines of temperate glaciers coincide with the equilibrium line, we analyzed five Landsat images spanning 1979–2003 and an ASTER-derived digital elevation model to reveal oscillations in the equilibrium line altitude (ΔZELA). The average ELAs range between 870 m and 1529 (± 29 m), with lower altitudes on the west side. Winter snow cover accumulation indicates higher elevations (relative to the glacier snout) of the transient snowlines in the west. Thus, one of the reasons for the higher retreating rates observed on the west side is that the lower part of the ablation area is likely exposed to year-round ablation. Glacier sensitivity to ΔZELA oscillations would depend upon the topographic condition of the accumulation area (gentle or steep). In outlet glaciers with gentle accumulation areas such as San Rafael and San Quintin, ΔZELA of up to 65 and 70 m at the central flow part and bare ice area variations > 5 km2 and > 13 (± 0.6 km2) were observed, respectively.
Spatial and temporal variation in mycorrhizal associations may significantly impact plant community dynamics. In this study we evaluated the distribution and abundance of mycorrhizal associations in alpine plant communities to gain a better understanding of the potential effects of microhabitat and host identity on plant-fungus mutualisms. We surveyed the abundance of ectomycorrhizae (ECM) associated with Salix sp. and the abundance of arbuscular mycorrhizae (AMF) associated with Taraxacum ceratophorum, T. officinale, Polemonium viscosum, and P. delicatum in plots under willow canopies and in adjacent open meadows. AMF colonization of T. ceratophorum, T. officinale, and P. viscosum was greater in open meadow than in understory habitats. Conversely, ECM abundance was greater in the willow understory than in the surrounding open meadow. AMF abundance in three of the four host species was negatively correlated with ECM abundance in the soil microsite. Taraxacum ceratophorum showed consistently high colonization by AMF regardless of habitat or ECM abundance. Our results suggest that willow-mediated heterogeneity in light and nutrient availability influence the distribution of AMF associations across the willow-meadow ecotone. Furthermore, species-specific plant life history traits related to growth strategies, carbon allocation patterns, and stress tolerance likely affect mycorrhizal dependence and interspecific variation in mycorrhizal associations.
Lakes may serve as sentinels for the impacts of changing climate in alpine areas. In the Rocky Mountain region, 2002 was a year with extremely low snowpack. We examined the summer phytoplankton community in Green Lake 4 for a 6-year period that included the summer of 2002. The phytoplankton community variation was examined in the context of the changes in physical and chemical properties of Green Lake 4. The physical changes associated with the 2002 drought included warmer surface water temperatures and greater hydraulic residence times; whereas the chemical changes included higher concentrations of acid neutralizing capacity (ANC) and major ions. During the summer of 2002 the phytoplankton community was dominated by Synedra sp. and Ankyra sp.; two previously rare species. The growth of Synedra sp. was sufficient to cause a decrease in silica concentrations, which has not been observed in other summers in the water quality monitoring record. The results of a redundancy analysis (RDA) indicated that concentrations of major ions and ANC were aligned with Synedra sp. and Ankyra sp. during the 2002 drought year. Following the 2002 drought year, Chrysococcus sp. and Chlorococcum sp., which became abundant, were aligned with nitrate in the RDA. These results indicate that the response of the phytoplankton community to the extreme drought was most strongly correlated with water quality changes that occurred, rather than temperature and hydraulic residence time. The dominant species in the post-drought phytoplankton community were found to be associated with nitrate, which is brought to the watershed by atmospheric deposition and may represent an anthropogenic driver of phytoplankton community composition.
On the western Tibetan Plateau the endangered Tibetan antelope, Pantholops hodgsonii, has traditionally been hunted for subsistence. Although several hunting techniques are used, a common one that leaves evidence on the landscape is the use of earth or stone diversionary barriers, or drive-lines, with hiding depressions used for shooting. Within the western Chang Tang Nature Reserve on the northwestern Tibetan Plateau we located 45 examples of these generally funnel-shaped trap systems near the northern limits of human habitation in Gertse and Rutok counties, Ngari Prefecture, Tibet Autonomous Region, China. The more recently maintained drive-lines were located farther to the north, and many of the southern ones we observed had, according to locals, not been used in many years, as hunting activity apparently has moved northward. Increasing human population and settlement of northern areas, new pastoral land-tenure arrangements and associated fencing, as well as modern techniques for hunting antelope and increased markets for their fine wool are all changing the human-wildlife dynamic at the northern edge of human habitation in the Chang Tang. Such new developments are likely to result soon in a relegation of the nomadic pastoralists' old hunting practices to a tradition of the past.
As with glaciers, long-lasting snowpatches have measurable features that are likely to be affected by a warming climate. Changes in these snowpatches are important as they often affect the down-slope thermal regime, water supply, nutrients, soil development, and vegetation. Australia's longest-lasting snowpatches, occurring in the Snowy Mountains, are formed during northwesterly winds, being deposited on southeasterly slopes where they are protected from insolation. Longevity of snowpatches is determined by winter snow and summer temperatures, with 155 days variation in the date of thaw among years. Snowpatches generally occurred in the same locations annually, but differences in direction of the winds during deposition affected snowpatch formation, accumulating aspect, and spatial melt patterns among years. Date of thaw of snowpatches was related to the general snowpack that has declined significantly over the past 54 years. Snowpatches previously multi-year in duration, melted in 2006 in the same year that they formed. Australian snowpatches have already declined with the resultant loss of specialized vegetation. Trends in reducing amount of snow and earlier thaw cast doubt on the long-term future of these snowpatches and their specialized plant communities.
The distribution of soil mites was studied in the foreland of the Hardangerjøkulen glacier in central south Norway, close to a glacier snout, which has been receding since 1750. Twenty sampling plots were distributed along a gradient spanning from 30 to 230 years, and five additional plots were in 10,000-year-old soil nearby. To standardize the microhabitat, all 320 soil cores (each 10 cm2 and 3 cm deep) were taken in Salix herbacea vegetation. The main focus was on oribatids, and most juveniles were identified to species. Two small, parthenogenetic species were pioneers, with high abundance in young soil: Tectocepheus velatus and Liochthonius cf. sellnicki, although their dominance values decreased sharply with time. The youngest soils also contained unidentified Actinedida and Gamasidae, and pitfall traps revealed the rather large, predatory actinedid species Podothrombium strandi. The number of oribatid species increased gradually with soil age. The oldest soil contained 19 oribatid species, but only six of them, all in low densities, were unique to this soil. Parthenogenetic species were present in all age classes of soil. Although there exist few earlier studies on mite succession in glacial foreland soil, mites are clearly among the earliest colonizers along receding glaciers.
We studied effects of oil and gas exploration, using the most recent seismic exploration technologies, on tundra plant communities and soils in four vegetation types in the Low Arctic of western Canada, two to three years post-disturbance. For all four vegetation types, seismic lines had less vascular plant cover and more bare ground than adjacent “reference” tundra. For the two upland tundra vegetation types, mosses and lichens were less abundant on seismic lines than in reference plots. There were no apparent differences in organic layer thickness between seismic lines and reference areas, but active layer depth (at the time of sampling) was significantly greater on seismic lines for the upland tundra and one of the wetland vegetation types. Diversity and richness were lower, and community composition was different, on seismic lines (as compared to reference plots) in upland tundra vegetation types but not in wetland types. The results suggest that (1) upland vegetation types are less resistant to seismic disturbance, (2) active layer depth increases following seismic disturbance, and (3) impacts from modern seismic techniques in upland tundra are similar to, or somewhat greater than, the initial impacts observed from the earliest phases of winter exploration ∼30 years ago.
The role of backcountry huts as introduction points for the establishment and spread of non-native plants into remote natural areas has received little attention. We surveyed soil and vegetation around 25 backcountry huts in the subalpine landscape of the Australian Alps to examine the role that such huts play in acting as foci for invasion by non-native species into remote mountain areas. We found that the hut surroundings were characterized by greater soil compaction, lower vegetation height, and more bare ground relative to the native plant community located 100 m from huts. At the landscape-scale, a total of 32 non-native species were recorded within 100 m of huts. Seven species were found at greater than 50% of huts (Hypochoeris radicata, Taraxacum officinale, Acetosella vulgaris, Trifolium repens, Cerastium glomeratum, Agrostis capillaris, Poa annua), and these tended to be the species that have (a) been long-established (>50–100 yrs) and (b) are the most frequent in the broader landscape. Hence, huts act to promote these ruderals by providing opportunities for their establishment, but such opportunities are not confined to hut surroundings. Several other non-native species, however, were common around huts but largely absent from the wider landscape (e.g. Anthoxanthum odoratum, Plantago major, Polygonum aviculare, Stellaria media). This suggests that some species are advantaged by the disturbance and dispersal opportunities provided by hut recreational activities in a way that is not catered for elsewhere in the Australian Alps. A weak negative relationship between non-native species richness and increasing altitude was found, but native species richness and distance of hut from access road were poor predictors of non-native species richness. Our study highlights that recreational activities may provide opportunities for the establishment of non-native plant species in remote high mountain areas, some of which are novel to the landscape, and that these may form the basis for further invasion into adjoining native vegetation.
The results of two simulations of hourly ablation, from late July to September 2002, at a site on the Place Glacier are described. First, ablation is modeled from a data set collected at the glacier site; second, from a data set collected off-glacier at a site below the glacier tongue. The glacier data set simulations, based as they are on global and reflected short-wave radiation measurements, a net long-wave radiation model and the bulk turbulent heat transfer approach, provides a reasonably good simulation of cumulative ablation, amounting to almost 1.2 m during the experimental period, mostly due to melting out of the preceding winter snowpack. Average melt component flux densities due to net short-wave radiation, net long-wave radiation, sensible heat and latent heat due to moisture exchange are 93.1, −22.6, 14.4 and 3.91 W m−2, respectively, during this time. The glacier site data are also used to fit a snow albedo model to albedo measurements for old and new snow cover. The albedo model is then used in the second simulation, which is based on global radiation measurements, a similar net long-wave radiation model, and a heat transfer approach in which turbulent mixing due to katabatic and geostrophic flow is parameterized from the off-glacier temperature data. The second simulation scheme performs best if the katabatic component of the parameterization scheme is suppressed because the wind regime at the glacier site appears to be intermittent, but the scheme itself is based upon the idea of a continuously flowing glacier wind.
Sediment deposited from turbid meltwater from Hubbard Glacier dominates the benthic environment in Disenchantment Bay, a glacial fjord in southern Alaska. Sedimentation rates during the meltwater season average 22 cm yr−1 at a station 12 km from the glacier. Samples were collected for foraminiferal analyses from multicores and a piston core. Samples from multicores show annual trends in abundance of Elphidium spp. and Textularia earlandi. Lithofacies consist of couplets of laminated mud deposited by meltwater discharge in summer and diamicton beds deposited as ice-rafted debris during winter. Within mud layers, counts of Elphidium spp. and T. earlandi increase upcore until the winter diamicton layer, where they are absent to rare. Evidence for this variation in abundance can be seen at depth in the piston core. High C∶N ratios (30–90) indicate that carbon flux is from refractory, terrestrial sources rather than labile organic matter. We hypothesize that the pattern of seasonal variation is related to vertical migration of foraminifera toward a preferred sediment depth, then death following reproduction in late summer. Episodic events reduce total abundance, impacting the intra-annual pattern. The high resolution record from an Alaskan glacial fjord can be used to better understand in situ foraminiferal ecology.
The evaluation of fungal root endophytes of two multizonal mountain plant species (Soldanella carpatica and Homogyne alpine) in relation to altitude was conducted. The comparison of root colonization by coarse arbuscular mycorrhizal fungi (AMF) and the fine AMF endophyte (Glomus tenue), as well as the presence of dark septate endophytes (DSE) were assessed along altitudinal gradients (1000–2050 m a.s.l.) on calcareous and non-calcareous substrata in the Tatra Mts. (Western Carpathians). Additionally, AMF species composition in the rhizosphere of the investigated plants was determined. Coarse AMF dominated over the fine endophyte in roots of S. carpatica and H. alpina. In the case of S. carpatica, there was a tendency for coarse AMF colonization decline with increasing altitude, while the reverse trend was observed for the fine endophyte. In contrast, the altitudinal patterns of the two types were opposite in H. alpina. Fifteen AMF species associated with the rhizosphere of S. carpatica were identified at the sites located in the Western Tatra Mountains, whereas spores of only four species were isolated from the rhizosphere of H. alpina in the High Tatra Mountains. None of the identified AMF species was observed to occur both in the High and Western Tatra Mts. DSE accompanied AMF in the roots of S. carpatica and H. alpina at each site; however, the root colonization by this group of fungi was low. The DSE colonization did not have a consistent relationship with altitude in both plant species. The results suggest that at the investigated altitudes factors such as the type of substrata, host plants, and local plant species composition may play a more important role in determining root colonization as well as the establishment of a local AMF community than the climatic changes with increasing elevation above sea level.