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Seabirds are an important factor affecting the chemical properties of the arctic soil environment. The objective of this work was to study the differences in content and distribution of heavy metals in organic soils resulting from the differential influence of seabirds. Studies were conducted in two stations in the southwest part of Spitsbergen—the first without the influence of seabirds and the second directly affected by an avian colony. Basic properties of soils as well as total content of Ca, Na, Mg, K, Fe, Al, Cu, Zn, Ni, Mn, Pb, Cd, Co, and Cr were determined. Reference was made to the previously published contents of different forms of phosphorus (P) for these locations. The studies showed that Zn, Mn, Cu, and Cd contents were higher in the soils that had been in the vicinity of the seabird colony. High statistically positive correlations of Cd, Cu, and Zn were noted with particular P forms. In the case of Pb, Cr, Co, and Ni content, the seabird influence was not dominant; probably other factors were more relevant (the processes of weathering, denudation, leaching, and atmospheric pollutants transported in the form of dust or gases). Clear segregation was observed of individual positions conditioned by selected soil features and by heavy metals content.
Woody plants in windy environments have been used as indicators of prevailing wind direction, because wind can influence plant growth form. We investigated whether non-woody plants also display consistent prevailing wind deformation by observing the direction of asymmetry in growth form of cushion plants, graminoids, and prostrate shrubs growing in highly wind-exposed treeless environments in alpine Tasmania and subantarctic Macquarie Island. Wind distortion of individual plants was inferred from vertical photographs of feldmark and alpine heath vegetation. High correspondence in growth direction between plants of different types suggests a uniform wind influence on plants at the local scale (within <2 m). Dominant wind direction inferred from plant distortion was not consistent with the strongest and most frequent winds. On a relatively dry mountain with shallow soils the plants responded to strong northwest winds in an apparent desiccation response. Elsewhere, they responded to strong southwest winds in an apparent ice abrasion response. We conclude that, in maritime alpine and subantarctic environments, the direction of wind distortion can be measured using any of shrubs, graminoids, or cushion plants, but that this direction is not necessarily a response to the prevailing strongest winds, but rather winds that most damage foliage, the cause of damage varying with environmental context.
Atmospheric warming is expected to cause shifts in arctic tundra vegetation composition, especially in the abundance and distribution of shrub species. Greater shrub abundance will impact the carbon exchanges between tundra ecosystems and the atmosphere, including ecosystem respiration. Here, total respiration under the shrub canopy (RT) and its components soil respiration (RS) and respiration from the ground cover vegetation (RG) were investigated at three tundra sites in the Canadian Low Arctic with varying shrub coverage. Seasonal RT and RS mean values were significantly greater (P < 0.05) at the site with greatest shrub abundance; mean values were 3.70 and 3.22 μmol m-2 s-1, respectively. Mean RG did not differ among sites; mean values ranged from 0.45 to 0.52 μmol m-2 s-1. Soil temperature exerted a stronger control on RT and RS compared to soil moisture. Differences in RT and RS among sites were attributed to differences in soil properties, such as soil total N content and bulk density. These findings suggest that belowground sources of respired carbon dioxide in Low Arctic tundra may vary with long-term shrub expansion as soil microclimate conditions and physiochemical properties adjust to changes in shrub coverage.
Temporal changes in the properties of glaciers located on the central Tibetan Plateau are a sensitive indicator of climate change and the water supply. To estimate the region-wide glacier budgets for three study sites covering the region extending from West- Geladandong to Bugyai Kangri, we compared 1968/1969 topographic maps, the 2000 SRTM DEM, and recent ASTER DEMs for glacier mass budget calculations. Between ∼1969 and ∼2015, the specific mass budget was -0.31 ± 0.05 m w.e. a-1 for the entire Tanggula Mountains, which is lower than the global average. This ongoing mass loss is mainly caused by increasing summer temperatures since the 1960s. Heterogeneous glacier behavior can be explained by a combination of factors, including meteorological conditions, proglacial lakes, and surge-type glaciers.
The slope-fluvial system comprises two subsystems: (a) the slope subsystem, with the dominance of mass movements, and (b) the fluvial (channel) subsystem, with fluvial processes dominating. The most interesting element of this system, and the most difficult to identify and explore, is the slope-to-channel transition zone between the dominance of slope processes and the dominance of fluvial processes. This article aims at exploring the detailed structure of the slope-fluvial system, with a particular focus on the transition zone between the slope and fluvial subsystems in the alpine and montane environments of the Western Tatra Mountains. This purpose is pursued through: (1) identifying the morphometry of headwaters, and (2) delimiting a theoretical border between the slope subsystem and the fluvial subsystem. To this end, a statistical analysis of morphometric parameters of 50 first- to third-order subcatchments was conducted. Particular attention was paid to analyzing the catchments' gradient-to-area relationship. On the basis of gradient-to-area relationship, seven catchment types were defined, characterized by various sequences of slope-fluvial system sections, as well as a border between the slope subsystem and the fluvial subsystem. Based on the morphometric parameters and the slope-fluvial system structure, the catchments under research may be divided into two groups, representing areas with different natural environmental conditions. Alpine zone comprises mostly catchment systems in their initial development stage, with little-developed drainage networks, classified entirely to the slope subsystem. These catchments have very high gradients, elongated shapes, and low bifurcation ratios. Montane zone is composed mainly of catchments at a similar development stage, with relatively large surface areas (∼1 km2) and well-developed drainage networks, which include fluvial reaches. Such catchments are usually wide-shaped and have low gradients and high bifurcation ratios. The transition from slope process dominance to fluvial process dominance may be either smooth or abrupt.
Auklets (Aethia spp.) are small seabirds, endemic to the North Pacific Ocean, that nest in rock crevices on islands in Alaska and Russia. Nesting habitats for least (A. pusilla) and crested (A. cristatella) auklet colonies in the southern part of their range (Aleutian and Kuril Islands) are becoming overgrown by vegetation, which is fertilized by the auklets, making rock crevices unavailable for breeding. Colonization of newly created volcanic habitats suggests that auklets are habitat-limited in the southern range. The largest colonies there of least and crested auklets exist on lava slopes <100 years old. We propose that in the south, volcanic activity is required to maintain auklet populations. In contrast, colonies in the northern Bering Sea and Sea of Okhotsk show no indication of habitat limitation. They occur in more persistent talus slope habitats maintained by weathering, slumping, frost heaving, and tumbling. Biological processes there are slower and vegetation communities not as developed. We propose a conceptual model describing the interaction of geological and biological processes that influence auklet demography. We conclude that least and crested auklets require episodic disturbance (provided by volcanoes, earthquakes, and rock fall deposits) to maintain access to nest crevices. Auklets thereby provide an example of disturbance-adapted, early successional species that self-inhibit if their habitat is not regularly disturbed.
This study examined vegetation greening at two arctic sites: the Apex River Watershed (ARW), Baffin Island, Nunavut (a Low Arctic site) and the Cape Bounty Arctic Watershed Observatory (CBAWO), Melville Island, Nunavut (a High Arctic site). The vegetation at both study sites was characterized using a supervised land-cover classification approach using high spatial resolution satellite remote sensing data (i.e., IKONOS [4 m] and WorldView-2 [2 m]). Meanwhile, Normalized Difference Vegetation Index (NDVI) data spanning the past 30 years were derived from intermediate spatial resolution data (i.e., Landsat TM/ETM/OLI [30 m]). The land-cover classifications were used to partition the Landsat NDVI time series by vegetation type. Climate variables (i.e., temperature, precipitation, and growing season length [GSL]) were examined to explore potential relationships of NDVI to climate warming trends. The results of the land-cover classifications demonstrated inherent trends of vegetation types along elevation and moisture gradients. The NDVI time series for the CBAWO (1985–2015) demonstrated an overall significant increase in greening, specifically in the dry and mesic vegetation types. Conversely, similar greening (overall or by vegetation type) was not observed for the ARW (1984–2015). Based on climate data from the nearest permanent weather station (Mould Bay, Nunavut), the overall increase in NDVI at the CBAWO was largely attributed to a significant increase in July temperatures and GSL.
Himalayan glaciers are normally difficult to monitor through field observations because of highly rugged and extremely inaccessible mountainous terrain. Thus, using Landsat data (MSS, ETM and TM), changes in glacier area, length, and debris cover have been delineated in the Baspa basin, which is a highly glacierized sub-basin of the Satluj River in the western Himalaya. Out of the total 109 glaciers inventoried through Landsat TM imagery (2011), 36 glaciers were found to be heavily debris covered (32.5 ± 2.0%). A shrinkage in glacier area of 41.2 ± 10.5 km2 (i.e., 18.1 ± 4.1%) at a rate of 1.18 ± 0.3 km2 a-1 from 1976 (227.4 ± 9.4 km2) to 2011 (186.2 ± 3.7 km2) has been recorded. The overall glacier retreat studied for 33 glaciers varied from 3.3 ± 0.03%, that is, 0.87 ± 0.06 km at a rate of 17.2 ± 1 m a-1 to 30 ± 6.6%, that is, 0.60 ± 0.04 km at a rate of 24.8 ± 0.2 m a-1. Consequently, the debris cover has increased by 23.5 ± 1.4 km2 (16.3 ± 3.8%) from 1976 to 2011. Overall, the clean, small sized, low-altitude glaciers with south to southwest aspect and relatively steep slope have lost maximum area, which indicated a major control of these factors on the glacier changes. Simultaneously, a trend estimation of observed climatic data (1976/1985–2008) of three meteorological stations (Sangla, Rakcham, and Chitkul) using Mann Kendall test, Sen's Slope estimator and linear regression test revealed an increase in temperature and rainfall while a decline in snowfall. Importantly, the Tmin has increased significantly at 95% confidence level during all the studied periods. The mean annual Tmin and Tmax indicated a rising trend at a rate of 0.076 and 0.071 °C a-1. Thus, the changes in temperature and precipitation may be the major causes of accelerating the glacier ablation. The higher area changes (53.0 ± 0.4%), of small glaciers <0.5 km2 mark their sensitivity to climatic changes especially rising temperature. Under the warming climate, formation and progressive expansion of glacial lakes is expected because of the glacier recession in the basin. For instance, the Baspa Bamak Proglacial Lake at the snout of Baspa Bamak glacier has expanded continuously from 2000 onward.
The dynamics of the Greenland Ice Sheet and drift of sea ice from the Arctic Ocean reaching Denmark Strait are poorly constrained. We present data on the provenance of Fe oxide detrital grains from two cores in the Denmark Strait area and compare the Fe grain source data with other environmental proxies in order to document the variations and potential periodicities in ice-rafted debris delivery during the Holocene. Based on their Fe grain geochemistry, the sediments can be traced to East Greenland sources and to more distal sites around the Arctic Basin. On the Holocene time scales of the two cores, sea ice biomarker (IP25) data, and quartz weight percent reveal positive associations with T°C and inverse associations with biogenic carbonate wt%. Trends in the data were obtained from Singular Spectrum Analysis (SSA), and residuals were tested for cyclicity. Trends on the environmental proxies explained between 15 and 90% of the variance. At both sites the primary Fe grain sources were from Greenland, but significant contributions were also noted from Banks Island and Svalbard. There is a prominent cyclicity of 800 yrs as well as other less prominent cycles for both Greenland and arctic sources. The Fe grain sources from Greenland and the circum—Arctic Ocean are in synchronization, suggesting that the forcings for these cycles are regional and not local ice sheet instabilities.
Recent literature suggests a shifting paradigm in relation to photobiology associated with ultraviolet (UV) radiation. UV has been repeatedly shown to be less detrimental to plant performance than previously thought. Nonetheless, relatively few plant species have been studied; too few to make definitive statements about effects of UV on plants at the ecosystem scale. We present findings of a field-based study using natural solar radiation, coupled with UV screening films, to determine physiological costs and benefits of exposure to solar UV for three species representative of subalpine Australian flora: a tree (Eucalyptus pauciflora), a forb (Geranium antrorsum), and a grass (Poa hiemata). Photochemical and photosynthetic responses to UV exclusion varied among species; exposure to UV was of no consequence to the structure, chemistry, or incidence of photoinhibition for E. pauciflora. UV was effectively screened at the leaf surface of P. hiemata. The response of G. anstrorsum to UV exclusion suggests greater susceptibility to photodamage; less successful in screening against UV and exposure reduced rates of photosynthesis, despite increased capacity to scavenge reactive oxygen species (via accumulating ascorbate). This study clarifies that responses to UV are highly species-specific, and that the endemic native flora is seemingly well-adapted to mitigate negative effects.
An analysis of the local atmospheric circulation in a northern Himalayan valley in the region of Mount Everest is presented. Data were collected using an automatic weather station over a one-year period in 2014. A ground-based wind profiler radar (WPR) and an in situ GPS radiosonde (RS) were also employed. This study focuses on the characteristics of afternoon strong wind events in the downstream of Rongbuk Valley. We found that: (1) The occurrence of the southwesterly wind during non-monsoon was in good consistency with high values of westerly wind at high levels over this region and confirmed to be driven by the strong westerly jet aloft. (2) The strong afternoon wind in monsoon season has a persistent southeasterly direction, which differs from the prevailing direction of the strong wind in non-monsoon. This flow was found to be independent of the wind aloft and was strongly seasonal, developing at Qomolangma Station (QOMS) when the subtropical jet stream had moved northward and was most stable and strongest in the early monsoon season but before the rainy season. (3) The southeasterly wind in monsoon is colder than local air, suggesting that it is driven by a strong thermal gradient from the Arun Valley to QOMS. Our results contribute to improving our knowledge of local circulation patterns in the Himalayas, and also to gaining a detailed understanding of the mountain chain's role in both the monsoon system and regional transport of atmospheric pollutants.