FINE STRUCTURE OF THE SNOW ALGA (CHLAMYDOMONAS NIVALIS) AND ASSOCIATED BACTERIA1

Chlamydomonas nivalis (Bau.) Wille is present in red snow as large spherical resting cells. Fine structural studies reveal an abundance of clear granules in the cytoplasm and occasional starch grains in the chloroplast. Individual cells display a thick cell wall with a smooth outer surface. Cells may be surrounded by a loose fibrous network in which encapsulated bacteria are seen. The bacteria have a characteristic Gram-negative cell wall and constrictive mode of division. The algal-bacterial association appears to be characteristic of red snow populations.     

Energy feedbacks of northern high-latitude ecosystems to the climate system due to reduced snow cover during 20th century warming

The warming associated with changes in snow cover in northern high-latitude terrestrial regions represents an important energy feedback to the climate system. Here, we simulate snow cover-climate feedbacks (i.e. changes in snow cover on atmospheric heating) across the Pan-arctic over two distinct warming periods during the 20th century, 1910–1940 and 1970–2000. We offer evidence that increases in snow cover–climate feedbacks during 1970–2000 were nearly three times larger than during 1910–1940 because the recent snow-cover change occurred in spring, when radiation load is highest, rather than in autumn. Based on linear regression analysis, we also detected a greater sensitivity of snow cover–climate feedbacks to temperature trends during the more recent time period. Pan-arctic vegetation types differed substantially in snow cover–climate feedbacks. Those with a high seasonal contrast in albedo, such as tundra, showed much larger changes in atmospheric heating than did those with a low seasonal contrast in albedo, such as forests, even if the changes in snow-cover duration were similar across the vegetation types. These changes in energy exchange warrant careful consideration in studies of climate change, particularly with respect to associated shifts in vegetation between forests, grasslands, and tundra.     

杉木人工林冰雪灾害受灾和萌生情况调查

以九龙山国家级自然保护区的主要公益林杉木人工林作为研究对象,选择具有代表性的受灾区域,自海拔700 m至900 m设置样地,共10块样地,总面积4 000 m2。分析其受2008年初严重冰雪灾害破坏及灾后萌生情况与胸径、树高、尖削度、海拔之间的关系。结果表明：1）杉木人工林损害严重,其中断冠、断干植株比例较高,而掘根和冻死植株相对较少;杉木具有极强的萌生能力,以断冠杉木的萌生能力最强。2）不同胸径、树高、尖削度的杉木对于冰雪灾害的抵御能力及萌生能力存在一定差异,小径级矮小的个体受灾较重,易被冻死和掘根,大径级的较高个体受灾相对较轻,主要表现为断冠和断干危害,且不同径级下的受灾杉木上部萌生均占较大比例。3）杉木的抵御能力和萌生能力与海拔存在一定的关系,高海拔地区杉木受灾较重,而中海拔地区的杉木萌生能力相对较强。     

青藏高原1979-2007年间的积雪变化

利用雪深被动微波遥感数据产品,对青藏高原1979—2007年积雪深度、积雪日数的分布变化及其趋势进行了分析。结果表明:青藏高原积雪日数、积雪深度和海拔三者之间在空间上具有显著正相关;青藏高原积雪在1988年发生突变,该年前后积雪分布有显著不同,这与20世纪80年代中后期青藏高原由暖干时期进入暖湿时期有关;将青藏高原按夏季水汽来源不同将其分为南北两部分,发现29年来北部积雪日数变化与全国积雪变化相反呈极显著增加趋势(R2=0.39,P0.01),以1.40 d/a的趋势增加,主要原因是西北部地区冬季积雪日数增加;南部积雪深度与全国积雪变化一致呈极显著减少趋势(R2=0.24,P0.01),以-0.04 cm/a的趋势减少,主要原因是东南部春、夏、秋三季积雪深度减少。     

Impact of spruce forest on rainfall interception and seasonal snow cover evolution in the Western Tatra Mountains,Slovakia

The paper analyzes the impacts of the spruce forest on precipitation interception and evolution of snow cover in the mountain catchment of the Jalovecky creek, the Western Tatra Mountains, Slovakia. Both processes were monitored at the elevation of 1420 m a.s.l.. Interception was measured from the end of August 2006 until November 2008 by a network of 13 raingauges. Mean interception over the studied period in forest window was 23%. Mean values for the dripping zone under tree branches, near stems of the trees and under the young trees were 28%, 65% and 44%, respectively. With exception of forest window, the interception at the same characteristic positions was highly variable. Calculated daily precipitation thresholds needed to fulfill the storage capacity of the canopy were about 0.8–0.9 mm. Differences in snow accumulation and melt in the open area (elevation 1500 m a.s.l.) and in the forest were measured in winters 2003–2008. Snow depths (SD) and water equivalents (SWE) were typically smaller in the forest, although the differences were getting smaller towards the end of snow season. SD and SWE in the forest were higher than in the open area for a short time before the end of season in winters 2003 and 2005. The correlations between SD and SWE in the open area and in the forest explained about 90% of variability. The energy balance snow model UEB satisfactorily simulated the evolution of snow cover in the forest and in the open area.     

Nitrate concentrations in snow from remote areas: implication for the global NO x flux

Increased emissions of nitrogen compounds to the atmosphere by human activities have been well documented. However, in order to better quantify these anthropogenic emissions, better knowledge of natural emissions rates must be known. In addition, variation in natural emissions through time should be documented. In this note we present data collected and/or analyzed by us for NO₃ ^– in recent snow from remote regions of the world. We also summarize existing data sets from other remote regions. This is done to establish a better understanding of NO₃ ^– deposition rates in these regions as well as to add more information to our global understanding of NO₃ ^– deposition.     

PHOTOSYNTHESIS IN THE SNOW: THE ALGA CHLAMYDOMONAS NIVALIS (CHLOROPHYCEAE)1

Red blooms of snow algae consisting almost exclusively of large spherical red cells of Chlamydomonas nivalis (Bauer) Wille are widespread during the summer in the Beartooth Mountains in Montana and Wyoming. Field studies designed to examine the effects of temperature, light, and water potential on algal activity were performed with natural populations using photosynthetic ¹⁴C-HCO₃- or ¹⁴CO₂ incorporation as a measure of activity. The algae photo-synthesized optimally at 5.4 × 10⁴ lx, but were not inhibited by increased light intensity up to 8.6 × 10⁴ lx, the maximum observed in the field. Photosynthesis was sensitive to a reduction in water potential, and since low water potentials develop in snow at temperatures below 0 C, it is unlikely that significant algal activity occurs at the sub-0 temperatures which occur throughout winter. Photosynthesis was much lower following melting of the snow, but this was probably due to decreased diffusion of CO₂. The optimal temperatures varied considerably among the different algal populations. Most samples photo-synthesized optimally at 10 or 20 C but retained substantial activity at temperatures as low as 0 or -3 C. Exceptional samples photosynthesized optimally at 0 or -3 C. It is proposed that the varied temperature responses reflect the presence of different temperature strains. Taken together, the data suggest that development of the snow algae can occur only during the summer months.     

Spectral distribution of light under a subarctic winter lake cover

This study examines the spectral distribution of light penetrating the snow and ice cover of a lake in subarctic Labrador. Using a large sample under a range of cover conditions, the role of distinct layers, (snow, white or snow ice, black or clear ice) commonly found in subartic and temperate lake winter covers, was investigated. Measurement and analysis were restricted to wavelengths between 450 nm and 720 nm. Snow and white ice light transmittance was greatest at 450 and 470 to 500 nm respectively. Absorption was greatest in the red portion of the measured spectrum; white ice showing greater red absorption than snow. Black ice light transmittance showed only a slight wavelength dependence. The differential spectral absorption of light by snow and white ice layers produced a marked spectral distribution of the light that reaches the lake water surface. The importance of a spectral, rather than polychromatic, approach to the study of light, in winter biological limnology studies, is stressed.     

The consequences of multiple resource shifts on the productivity and composition of alpine tundra communities: inferences from a long-term snow and nutrient manipulation experiment

Background: Gradients in the amounts and duration of snowpack and resulting soil moisture gradients have been associated with different plant communities across alpine landscapes.

Aims: The extent to which snow additions could alter plant community structure, both alone and in combination with nitrogen (N) and phosphorus (P) additions, provided an empirical assessment of the strength of these variables on structuring the plant communities of the alpine tundra at Niwot Ridge, Colorado Front Range.

Methods: A long-term snow fence was used to study vegetation changes in responses to snowpack, both alone and in conjunction with nutrient amendments, in plots established in dry and moist meadow communities in the alpine belt. Species richness, diversity, evenness and dissimilarity were evaluated after 20 years of treatments.

Results: Snow additions, alone, reduced species richness and altered species composition in dry meadow plots, but not in moist meadow; more plant species were found in the snow-impacted areas than in nearby controls. Changes in plant community structure to N and N + P additions were influenced by snow additions. Above-ground plant productivity in plots not naturally affected by snow accumulation was not increased, and the positive responses of plant species to nutrient additions were reduced by snow addition. Plant species showed individualistic responses to changes in snow and nutrients, and indirect evidence suggested that competitive interactions mediated responses. A Permanova analysis demonstrated that community dissimilarity was affected by snow, N, and P additions, but with these responses differing by community type for snow and N. Snow influenced community patterns generated by N, and finally, the communities impacted by N + P were significantly different than those affected by the individual nutrients.

Conclusions: These results show that changes in snow cover over a 20-year interval produce measureable changes in community composition that concurrently influence and are influenced by soil nutrient availability. Dry meadow communities exhibit more sensitivity to increases in snow cover whereas moist meadow communities appear more sensitive to N enrichment. This study shows that the dynamics of multiple limiting resources influence both the productivity and composition of alpine plant communities, with, species, life form, and functional traits mediating these responses.     

Isolation and characterization of polymorphic microsatellite markers in the red snow crab (Chionoecetes japonicus)

A total of 12 polymorphic microsatellite DNA loci were isolated from the red snow crab, Chionoecetes japonicus (Brachyura: Majidae), one of important fisheries resources in the Far East. The number of alleles observed at each locus ranged from two to 19, with the observed and expected heterozygosities of 0.125-0.875 and 0.156-0.949, respectively, suggesting these loci to be a useful molecular marker for population analysis in this species. Of the 12 loci, seven also were available for genotyping of the snow crab, Chionoecetes opilio, implying these loci as a useful molecular marker in the genus Chionoecetes.     

水源圈对荒漠草原土壤种子库的影响

草场上,由于饮水的需求导致牲畜经常在水源点和草场间往返,从而出现"水源圈"现象。本研究以新疆准噶尔盆地东南缘荒漠草原人工水源点为中心,在距其50、100、200、400、800和1200 m处设置了6个采样点,通过室内培养获得了土壤种子库数据。结果表明:土壤种子库共有17种植物,分属于8科,藜科和菊科居多,其中1年生草本植物10种,多年生草本植物7种。水源圈内土壤种子库密度在211.5~362.5粒·m-2,其中距水源点50 m处土壤种子库密度最低,距水源点1200 m处最高。距离水源圈越近,土壤种子库的物种数量极显著增加(P0.01),1年生草本植物种数所占比例减小,多年生草本植物种数所占比例增大。在相邻采样点间,土壤种子库物种组成相似性指数较高,为0.70~0.84,表现出较小的空间异质性。距离水源点越近,多样性指数、丰富度指数和均匀度指数越大,水源圈效应增加了土壤种子库物种数量,导致主要建群植物种子减少,短命、类短命草本植物种子增加。     

Snow depth manipulation and its influence on soil frost and water dynamics in a northern hardwood forest

Climate change will likelyresult in warmer winter temperatures leading toless snowfall in temperate forests. Thesechanges may lead to increases in soil freezingbecause of lack of an insulating snow cover andchanges in soil water dynamics during theimportant snowmelt period. In this study, wemanipulated snow depth by removing snow for twowinters, simulating the late development of thesnowpack as may occur with global warming, toexplore the relationships between snow depth,soil freezing, soil moisture, and infiltration.We established four sites, each with two pairedplots, at the Hubbard Brook Experimental Forest(HBEF) in New Hampshire, U.S.A. and instrumentedall eight plots with soil and snow thermistors,frost tubes, soil moisture probes, and soillysimeters. For two winters, we removed snowfrom the designated treatment plots untilFebruary. Snow in the reference plots wasundisturbed. The treatment winters (1997/1998 and1998/1999) were relatively mild, withtemperatures above the seasonal norm and snowdepths below average. Results show the treatedplots accumulated significantly less snow andhad more extensive soil frost than referenceplots. Snow depth was a strong regulator ofsoil temperature and frost depth at all sites.Soil moisture measured by time domainreflectometry probes and leaching volumescollected in lysimeters were lower in thetreatment plots in March and April compared tothe rest of the year. The ratio of leachatevolumes collected in the treatment plots tothat in the reference plots decreased as thesnow ablation seasons progressed. Our data showthat even mild winters with low snowfall,simulated by snow removal, will result inincreased soil freezing in the forests at theHBEF. Our results suggest that a climate shifttoward less snowfall or a shorter duration ofsnow on the ground will produce increases insoil freezing in northern hardwood forests.Increases in soil freezing will haveimplications for changes in soil biogeochemicalprocesses.     

Effects of seasonal snow on the growing season of temperate vegetation in China

Variations in seasonal snowfall regulate regional and global climatic systems and vegetation growth by changing energy budgets of the lower atmosphere and land surface. We investigated the effects of snow on the start of growing season (SGS) of temperate vegetation in China. Across the entire temperate region in China, the winter snow depth increased at a rate of 0.15 cm yr^?1 (P = 0.07) during the period 1982–1998, and decreased at a rate of 0.36 cm yr^?1 (P = 0.09) during the period 1998–2005. Correspondingly, the SGS advanced at a rate of 0.68 day yr^?1 (P < 0.01) during 1982–1998, and delayed at a rate of 2.13 day yr^?1 (P = 0.07) during 1998–2005, against a warming trend throughout the entire study period of 1982–2005. Spring air temperature strongly regulated the SGS of both deciduous broad‐leaf and coniferous forests, whereas the winter snow had a greater impact on the SGS of grassland and shrubs. Snow depth variation combined with air temperature contributed to the variability in the SGS of grassland and shrubs, as snow acted as an insulator and modulated the underground thermal conditions. In addition, differences were seen between the impacts of winter snow depth and spring snow depth on the SGS; as snow depths increased, the effect associated went from delaying SGS to advancing SGS. The observed thresholds for these effects were snow depths of 6.8 cm (winter) and 4.0 cm (spring). The results of this study suggest that the response of the vegetation's SGS to seasonal snow change may be attributed to the coupling effects of air temperature and snow depth associated with the underground thermal conditions.     

Geochemical Approach to Human Health Risk Assessment of Inhaled Trace Elements in the Vicinity of Industrial Enterprises in Tomsk,Russia

Human health risks due to exposure of heavy metals in the atmospheric air of Tomsk, Russia, were studied. The concentrations of 22 metals in the ambient air were calculated on the basis of the ICP–MS experimental determination of their contents in the insoluble fraction of snow cover. Non-carcinogenic hazards were estimated for the areas of power plant (“Zone PP”), brickworks location (“Zone BF”), zone influenced by concrete product plants (“Zone CP”), and petrochemical plant suburbs (“Zone PCP”). Manganese, Al, Cu, and Ba make the largest contribution to the integral non-cancer hazard caused by chronic inhalation intake in all areas. Zinc is added to the above listed elements in the “Zone PP” and V, Co, Cr, and Ni in the “Zone BF” are also added. Densely populated residential areas “Zone BF” and “Zone PP” were characterized by the higher levels of diseases risks associated with human inhalation intake of metals in comparison with other areas. The dust load should be primarily decreased in the zones subjected to harmful effects of brick factories and other construction materials. As to the power station, the portion of natural gas in consumption should increase from year to year for decreasing heavy metal emissions from burning of coal.     

黑龙江省中部地区森林对融雪径流的影响

利用多元回归统计方法,分析黑龙江省呼兰河和汤旺河流域森林覆被率、单位面积立木蓄积对融雪径流量和融雪输沙量的影响。结果表明森林能增加融雪径流量,减少融雪输沙量。而趋势分析结果显示了两个流域融雪径流量呈减少趋势,这与研究地区森林资源变化的趋势一致。因此,植树造林是增加融雪径流量,减少东北地区春耕干旱的一项有效措施。     

Snow craneflies of the Genus Chionea Dalman (Diptera: Limoniidae) from Korea

The Korean snow cranefly genus Chionea Dalman is reviewed taxonomically. Four species are identified: C. crassipes Boheman, C. kanenoi Sasakawa, C. mirabilis Vanin and C. deogyusana sp. nov. Among them, C. deogyusana sp. nov. is new to science, and C. kanenoi is reported for the first time in Korea. A key to Korean species and photographs of external features are given.     

Flexible response to short‐term weather in a cold‐adapted songbird

To improve survival during winter, temperate species use a variety of behavioural and physiological adaptations. Among songbirds, the maintenance of lipid reserves is a widely‐used strategy to cope with the severity of winter; however, little is known regarding how multiple synchronously acting environmental mechanisms work together to drive these effects. In a context where temperate winter conditions are becoming more variable, it is important to widen our understanding regarding the flexible adaptations that may allow wintering species to adjust to projected climate change. Using a long‐term dataset collected across multiple wintering populations (7 years; 8 locations), we analyzed the effects of daily variation in weather (e.g. temperature, snowfall) on the variation in energy reserves (i.e. fat stores) of wintering snow buntings Plectrophenax nivalis. Our results support the prediction that birds carry more reserves to increase the safety margin against starvation when conditions are energy‐demanding and access to food is unpredictable (i.e. colder, snowier conditions). Birds responded to daily changes in weather by increasing their reserves as conditions deteriorated, with maximal temperatures and snow depth being the most important predictors of fattening decisions. We also found that females consistently exhibited higher fat reserves than males relative to their body size, suggesting that differential physiological adaptations among sexes or social dominance may play an additional role in explaining variation in energy reserves across individuals in this species. Overall, our findings increase knowledge on phenotypic adjustments used by species wintering in temperate zones to match variation in their environment.     

A Model for Bacterial Colonization of Sinking Aggregates

Sinking aggregates provide important nutrient-rich environments for marine bacteria. Quantifying the rate at which motile bacteria colonize such aggregations is important in understanding the microbial loop in the pelagic food web. In this paper, a simple analytical model is presented to predict the rate at which bacteria undergoing a random walk encounter a sinking aggregate. The model incorporates the flow field generated by the sinking aggregate, the swimming behavior of the bacteria, and the interaction of the flow with the swimming behavior. An expression for the encounter rate is computed in the limit of large Péclet number when the random walk can be approximated by a diffusion process. Comparison with an individual-based numerical simulation is also given.