Photosynthetic pigments of plants and lichens inhabiting arctic tundra of West Spitsbergen

The content of photosynthetic pigments and the ratios between them were studied in 71 species of vascular plants, 17 species of Bryophyta, and 10 species of lichens inhabiting West Spitsbergen. With an increase in the level of organization from lichens to vascular plants, the content of photosynthetic pigments (chlorophylls (Chl) and carotenoids (Car)) increased; the Chl a/b ratios and light-harvesting complex values varied independently of organism taxonomy; the Chl/Car ratio tended to increase. The content of pigments is related to taxon advancement at the level of both divisions and higher plant families. In plants inhabiting Arctic region, the pigment content in primitive species was lower than in more advanced ones. In angiosperms inhabiting Spitsbergen, the amount of Chl was lower than in plants inhabiting other botanicgeographical regions.     

Progress in the study of algae and mosses in biological soil crusts

Algae and mosses are not only two of the familiar communities in the process of desert vegetational succession,but also have the highest biomass in biological soil crusts.Meanwhile,being the pioneer plants,algae and mosses are involved in the establishment of biological soil crusts,which have great importance in arid environments and play a major role in desert ecosystems,such as being the indicator of the vegetation type,soil-holding,preventing erosion by water and wind,and sand fixation.This paper reviews the advances in the study of algae and mosses in arid and semi-arid areas.It mainly describes the ecological functions of algae and mosses including their influences on water cycle,circulation of substances,and community succession.In addition,the relationships between algae and mosses are discussed.Finally,some suggestions are proposed for the research orientations of algae and mosses in biological soil crusts.Ecologically,algae and mosses have significant ecological importance in arid areas,especially in those areas where environmental problems are becoming increasingly serious.     

Progress in the study of algae and mosses in biological soil crusts

Algae and mosses are not only two of the familiar communities in the process of desert vegetational succession, but also have the highest biomass in biological soil crusts. Meanwhile, being the pioneer plants, algae and mosses are involved in the establishment of biological soil crusts, which have great importance in arid environments and play a major role in desert ecosystems, such as being the indicator of the vegetation type, soil-holding, preventing erosion by water and wind, and sand fixation. This paper reviews the advances in the study of algae and mosses in arid and semi-arid areas. It mainly describes the ecological functions of algae and mosses including their influences on water cycle, circulation of substances, and community succession. In addition, the relationships between algae and mosses are discussed. Finally, some suggestions are proposed for the research orientations of algae and mosses in biological soil crusts. Ecologically, algae and mosses have significant ecological importance in arid areas, especially in those areas where environmental problems are becoming increasingly serious.     

Disturbance of biological soil crust increases emergence of exotic vascular plants in California sage scrub

Biological soil crusts (BSCs) are comprised of soil particles, bacteria, cyanobacteria, green algae, microfungi, lichens, and bryophytes and confer many ecosystem services in arid and semiarid ecosystems worldwide, including the highly threatened California sage scrub (CSS). These services, which include stabilizing the soil surface, can be adversely affected when BSCs are disturbed. Using field and greenhouse experiments, we tested the hypothesis that mechanical disturbance of BSC increases emergence of exotic vascular plants in a coastal CSS ecosystem. At Whiting Ranch Wilderness Park in southern California, 22 plots were established and emergence of exotic and native plants was compared between disturbed and undisturbed subplots containing BSC. In a separate germination study, seed fate in disturbed BSC cores was compared to seed fate in undisturbed BSC cores for three exotic and three native species. In the field, disturbed BSCs had significantly (>3×) greater exotic plant emergence than in undisturbed BSC, particularly for annual grasses. Native species, however, showed no difference in emergence between disturbed and undisturbed BSC. Within the disturbed treatment, emergence of native plants was significantly, and three times less than that of exotic plants. In the germination study, seed fates for all species were significantly different between disturbed and undisturbed BSC cores. Exotic species had greater emergence in disturbed BSC, whereas native plants showed either no response or a positive response. This study demonstrates another critical ecosystem service of BSCs—the inhibition of exotic plant species—and underscores the importance of BSC conservation in this biodiversity hotspot and possibly in other aridland ecosystems.     

Phototolerance of lichens, mosses and higher plants in an alpine environment: analysis of photoreactions

 Adaptation to excessive light is one of the requirements of survival in an alpine environment particularly for poikilohydric organisms which in contrast to the leaves of higher plants tolerate full dehydration. Changes in modulated chlorophyll fluorescence and 820-nm absorption were investigated in the lichens Xanthoria elegans (Link) Th. Fr. and Rhizocarpon geographicum (L.) DC, in the moss Grimmia alpestris Limpr. and the higher plants Geum montanum L., Gentiana lutea L. and Pisum sativum L., all collected at altitudes higher than 2000 m above sea level. In the dehydrated state, chlorophyll fluorescence was very low in the lichens and the moss, but high in the higher plants. It increased on rehydration in the lichens and the moss, but decreased in the higher plants. Light-induced charge separation in photosystem II was indicated by pulse-induced fluorescence increases only in dried leaves, not in the dry moss and dry lichens. Strong illumination caused photodamage in the dried leaves, but not in the dry moss and dry lichens. Light-dependent increases in 820-nm absorption revealed formation of potential quenchers of chlorophyll fluorescence in all dehydrated plants, but energy transfer to quenchers decreased chlorophyll fluorescence only in the moss and the lichens, not in the higher plants. In hydrated systems, coupled cyclic electron transport is suggested to occur concurrently with linear electron transport under strong actinic illumination particularly in the lichens because far more electrons became available after actinic illumination for the reduction of photo-oxidized P700 than were available in the pool of electron carriers between photosystems II and I. In the moss Grimmia, but not in the lichens or in leaves, light-dependent quenching of chlorophyll fluorescence was extensive even under nitrogen, indicating anaerobic thylakoid acidification by persistent cyclic electron transport. In the absence of actinic illumination, acidification by ca. 8% CO₂ in air quenched the initial chlorophyll fluorescence yield F_o only in the hydrated moss and the lichens, not in leaves of the higher plants. Under the same conditions, 8% CO₂ reduced the maximal fluorescence yield F_m strongly in the poikilohydric organisms, but only weakly or not at all in leaves. The data indicate the existence of deactivation pathways which enable poikilohydric organisms to avoid photodamage not only in the hydrated but also in the dehydrated state. In the hydrated state, strong nonphotochemical quenching of chlorophyll fluorescence indicated highly sensitive responses to excess light which facilitated the harmless dissipation of absorbed excitation energy into heat. Protonation-dependent fluorescence quenching by cyclic electron transport, P700 oxidation and, possibly, excitation transfer between the photosystems were effectively combined to produce phototolerance. Received: 10 December 1999 / Accepted: 13 April 2000     

Green algae in alpine biological soil crust communities: acclimation strategies against ultraviolet radiation and dehydration

Green algae are major components of biological soil crusts in alpine habitats. Together with cyanobacteria, fungi and lichens, green algae form a pioneer community important for the organisms that will succeed them. In their high altitudinal habitat these algae are exposed to harsh and strongly fluctuating environmental conditions, mainly intense irradiation, including ultraviolet radiation, and lack of water leading to desiccation. Therefore, green algae surviving in these environments must have evolved with either avoidance or protective strategies, as well as repair mechanisms for damage. In this review we have highlighted these mechanisms, which include photoprotection, photochemical quenching, and high osmotic values to avoid water loss, and in some groups flexibility of secondary cell walls to maintain turgor pressure even in water-limited situations. These highly specialized green algae will serve as good model organisms to study desiccation tolerance or photoprotective mechanisms, due to their natural capacity to withstand unfavorable conditions. We point out the urgent need for modern phylogenetic approaches in characterizing these organisms, and molecular methods for analyzing the metabolic changes involved in their adaptive strategies.     

实验室条件下两种生物土壤结皮对荒漠植物种子萌发的影响

生物土壤结皮广泛分布在干旱、半干旱区,深刻影响着土壤表层特性,进而对植物种子散布、萌发和定居产生极大的影响。到目前为止,生物土壤结皮与植物关系的研究很少见到,并且这些有限的研究所得出的结论存在着争议。研究了不同年龄的两种生物土壤结皮（苔藓结皮和藻类结皮）对油蒿（Artemisia ordosica）和雾冰藜（Bassia dasyphylla）种子萌发的影响,同时也研究了这两种结皮在失去活性前后对油蒿、雾冰藜和小画眉草（Eragrostis poaeoides）种子萌发的影响。苔藓和藻类结皮的出现对油蒿和雾冰藜种子的萌发均有显著的促进作用,而结皮年龄对植物种子的萌发没有显著的差异。对于不同的植物种,结皮类型和活性对种子的萌发具有不同的作用。雾冰藜在两种结皮上的萌发有显著的差异而油蒿和小画眉草在两种结皮上的萌发没有显著差异。活藻类显著地增加了三种植物的种子萌发,活苔藓仅增加了油蒿和雾冰藜种子萌发量而对小画眉草种子的萌发没有作用,研究表明,生物土壤结皮对一些植物种子萌发具有明显的促进作用。     

Species composition and ecologo-phytocenotic spectra of vascular plants, mosses, and lichens on gold-mining sites in the taiga zone of the lower Amur River basin, the Russian Far East

Two-hundred-three species of vascular plants, 50 species of bryophyte and 41 species of lichens have been found on dredging and hydraulic gold-mining sites in the taiga zone of the lower Amur River basin. The main features of the anthropogenic relief and vegetation have been described. Dredging and hydraulic dumps are supposed to have the biggest similarity in the species composition and set of ecologo-phytocenotic elements, while the biggest difference is observed between dredging and hydraulic dumps on the one hand and pockets and settling pits, on the other. According to the data obtained in different regions, the species diversity of vascular plants growing on dredging and hydraulic gold-mining sites is quite rich.     

Comparisons of photosynthesis-related traits among understory lichens,mosses and vascular plant leaves in a high-elevation subalpine forest

对比高海拔亚高山森林林下地衣、藓类及维管植物叶片的光合相关性状 在高海拔亚高山森林中,许多地衣和藓类植物欣欣向荣,甚至成为林地表层的优势物种。尽管它们在森林生态系统中承担着不可替代的功能,但我们对其光合作用相关的功能性状水平知之甚少,对相同生境下藓类植物和维管植物的比较研究也较为匮乏。因此,本研究选择中国青藏高原东缘亚高山林下常见的3种地衣、3种藓类和4种维管植物,测定并对比了它们的碳、氮、磷含量及化学计量比、单位面积光合组织干重、叶绿素含量及光合光响应曲线的异同。研究结果表明,林下地衣的氮含量高于藓类植物,二者的氮、磷、叶绿素、光合速率及光合氮利用效率均低于维管植物叶片。不同种类地衣的光合相关性状与其生长环境相符,而林地表层的3种藓类植物和3种草本植物的功能性状在各自功能群中的种间差异均不显著。总之,这些结果表明高海拔亚高山林下地衣和藓类植物的优势与其光合相关性状关系不大,对严酷环境较强的适应能力可能是它们得以繁荣生长的关键。     

A survey of metal concentrations in higher plants, mosses, and lichens collected on King George Island in 1988

Antarctica is considered to be one of the least polluted regions on earth, and therefore, it is important to survey and control the level of contamination. Antarctic vegetation is very sparse and is essentially restricted to seashore oases and nunataks. Therefore, any data concerning metal levels in plants and lichens are of crucial value for this area. Our first goal was to determine metal concentrations in two higher plants and the most dominant species of mosses and lichens collected in 1988. We then compared the results of our survey with recent studies employing similar methodology. In our study, Cr, Cu, Fe, Ni, Pb, V, and Zn concentrations in mosses, C. quitensis and D. antarctica were also higher than typical values for mosses and vascular plants from unpolluted areas indicating anthropogenic influence. Mosses were determined to be better bioindicators of metals than lichens. Hg concentrations in mosses were significantly higher than those in shoots of C. quitensis and D. antarctica. Increases in Cr, Pb, and V concentrations over time were observed in moss when concentrations from samples collected in 1988 were compared with more recent data from other studies. Our results for King George Island may apply at least to all the maritime Antarctic where climate and plant communities are similar.     

Acidobacteria in microbial communities of the bog and tundra lichens

Bacterial communities of the lichens from a Sphagnum bog (Karelia) and tundra (Vorkuta oblast) were investigated. Members of the phylum Acidobacteria were numerous in the thallus of living and decaying lichens (3.8 × 10⁸ cells/g), constituting 6 to 32% of the total bacterial number. Pure cultures of acidobacteria were isolated from the samples of living and decaying lichen thallus. Ten of them were identified and classified as members of subgroup 1 of the Acidobacteria. The hydrolytic activity of two strains isolated from the living and decomposing zones of the thallus was investigated. They were capable of growth on xylan, starch, pectin, laminarin, and lichen extract. Acidobacteria were shown to be a stable and numerous component of microbial communities of the bog and tundra lichens.     

Transfer of radionuclides to ants, mosses and lichens in semi-natural ecosystems

There is a scarcity of data on transfer of both natural and anthropogenic radionuclides to detritivorous invertebrates for use in the assessment of radiation exposure. Although mosses and lichens have been extensively used in biomonitoring programs, the data on transfer of radionuclides to these species are limited, particularly for natural radionuclides. To enhance the available data, activity concentrations of ¹³⁷Cs, ²²⁶Ra and ²²⁸Ra were measured in ants, mosses and lichens and corresponding undisturbed soil collected from semi-natural ecosystems in Serbia and Montenegro and biota/soil concentration ratios (CR) calculated. Since the majority of internal dose to biota is expected to come from ⁴⁰K, the activity concentrations of this radionuclide were also determined. The mean CR values for ¹³⁷Cs, ²²⁶Ra and ²²⁸Ra in ants analyzed in this study were found to be 0.02, 0.06 and 0.02, respectively. The mean CR values of radionuclides in mosses were found to be 2.84 for ¹³⁷Cs, 0.19 for ²²⁶Ra and 0.16 for ²²⁸Ra, while those in lichens were found to be 1.08 for ¹³⁷Cs, 0.15 for ²²⁶Ra and 0.13 for ²²⁸Ra. The CR values obtained in this study were compared with default CR values used in the ERICA Tool database and also with those reported in other studies.     

Response of plants and the dominant microarthropod, Cryptopygus antarcticus, to warming and contrasting precipitation regimes in Antarctic tundra

We examined the influence of warming and supplemental precipitation on plant production and abundance of the dominant microarthropod, the springtail Cryptopygus antarcticus (Collembola), in tundra dominated by the vascular plants Colobanthus quitensis and Deschampsia antarctica along the Antarctic Peninsula. Tundra cores were placed in plots near Palmer Station where they were warmed with infrared heaters in combination with receiving supplemental precipitation. Diel canopy air and soil temperatures and air vapor pressure deficits in warmed plots were elevated 0.8 °C, 2.2 °C and 0.13 kPa, respectively. After two growing seasons, total aboveground plant production was greater under warming as a result of enhanced production by C. quitensis, which more than offset declines in moss biomass. Total aboveground plant production was also greater under supplemental precipitation primarily as a result of enhanced moss production. Total aboveground plant production was greatest under the combination of warming and supplemental precipitation, primarily as a result of enhanced C. quitensis production. C. antarcticus were more abundant in cores receiving supplemental precipitation and there was a strong treatment interaction; these springtails were most abundant in warmed cores receiving supplemental precipitation. Over 50% of the variability in the abundance of C. antarcticus could be explained by differences in aboveground plant biomass. However, plant production did not appear directly responsible for differences in C. antarcticus abundance; when we examined C. antarcticus abundance per unit of aboveground plant biomass, differences in its abundance among treatments were still apparent implying these differences were not the direct result of plant biomass. The responses of C. antarcticus were consistent with its known moisture and thermal preferences, suggesting that abiotic factors played a dominant role in controlling its abundance. Precipitation regime had large impacts on warming responses and these were species specific, illustrating the importance of future precipitation regimes in predicting system responses to warming.     

Viability, diversity and composition of the bacterial community in a high Arctic permafrost soil from Spitsbergen, Northern Norway

The viable and non-viable fractions of the bacterial community in a 2347-year-old permafrost soil from Spitsbergen were subjected to a comprehensive investigation using culture-independent and culture-dependent methods. LIVE/DEAD BacLight staining revealed that 26% of the total number of bacterial cells were viable. Quantitatively, aerobic microcolonies, aerobic colony-forming units and culturable anaerobic bacteria comprised a minor fraction of the total number of viable bacteria, which underlines the necessity for alternative cultivation approaches in bacterial cryobiology. Sulfate reduction was detected at temperatures between -2 degrees C and 29 degrees C while methanogenesis was not detected. Bacterial diversity was high with 162 operational taxonomic units observed from 800 16S rDNA clone sequences. The 158 pure cultures isolated from the permafrost soil affiliated with 29 different bacterial genera, the majority of which have not previously been isolated from permafrost habitats. Most of the strains isolated were affiliated to the genera Cellulomonas and Arthrobacter and several of the pure cultures were closely related to bacteria reported from other cryohabitats. Characterization of viable bacterial communities in permafrost soils is important as it will enable identification of functionally important groups together with the as yet undescribed adaptations that bacteria have evolved for surviving subzero temperatures for millennia.     

Widespread distribution of some minor chlorophyll-protein complexes in some plants and algae

The use of the non-ionic detergent octyl beta-d-glucoside has allowed the demonstration in spinach of a chlorophyll a+b-protein complex of apparent molecular weight 29 kilodaltons (Camm and Green, 1980, Plant Physiol 66: 428-432). Complexes analogous to this one also can be demonstrated in three grasses, in dicots of the Chenopodiaceae, Fabaceae, and Asteraceae, and in the siphonaceous green alga Acetabularia mediterranea. These complexes are clearly distinguishable from the light harvesting complex on the basis of the chlorophyll a/b ratio, apparent molecular weight, and polypeptide composition. In addition, most plants surveyed contained two, not one, minor chlorophyll a complexes as well as the chlorophyll a complex of Photosystem I.     

Interactions betweenSphagnum mosses and field layer vascular plants in the development of peat-forming systems

The interactions between field layer vascular plants andSphagnum mosses in peat-forming systems are discussed in terms of differences in growth strategies, access to light, acquisition of mineral nutrients and water and the processes involved in the formation of the micro-topographical structures characteristic for these systems. To keep pace with the vertical growth ofSphagnum, the co-occurring vascular plants require a growth strategy involving continuous movement of the growing point and meristematic tissue upwards and a frequent formation of adventitious roots. The growth form and architecture of the vascular plants determine the occurrence and distribution of the structural units on a mire, the hummocks, lawns and hollows. Dwarf shrubs and other vascular plants with an orthotropic growth pattern characterise hummocks, where they form a firm matrix which reinforces and supports the spongy biomass ofSphagnum. In a similar way, clonal herbs stabilise the lawns because of the predominantly plagiotropic, or only weakly orthotropic, growth pattern of the rhizomes and coarse roots in the upper, oxic layers. Extended periods of drought often may have deleterious effects on the mosses but smaller impacts on the vascular plants because of their more efficient water conducting system. Different sources of mineral nutrients are used bySphagnum (atmospheric deposition) and the vascular plants (mineralisation of the organic matter). The presence ofSphagnum, therefore, reduces the supply of nutrient resources to the vascular plants.Sphagnum thereby gains a competitive advantage. A high rate of mineralisation would be beneficial to the vascular plants by increasing their growth rates causing shading of theSphagnum mosses and covering the moss layer by the above-ground litter fall. However, the slow decomposition ofSphagnum litter keeps the system in balance as it will reduce the nutrient supply to the vascular plants.     

Microclimates and water budget of algae,lichens and a moss on some nunataks in Queen Maud Land

During the Norwegian Antarctic Expedition of 1984–1985, land parties worked in the area of Mühlig-Hofmannfjella and Gjelsvikfjella in Queen Maud Land (5° 20E, 1° 37W, 1000–1600 m a.s.l.). The nunataks in this area, which represents one of the climatic limits for terrestrial life on earth, is among those areas absorbing the highest quantity of shortwave radiation during a period of 24 h in summer. In spite of this the air temperature never, or very seldom, exceeds 0° C. The limiting factor for photosynthesis over most of the summer was water availability. Melt-water plays an important role in spring. During rest of the growth season, water from condensation is probably the most important water source for plants. On calm nights the rate of condensation during 6 h may reach 0.5 mm, which constitutes only 10%–30% of daily potential evapotranspiration. Plants situated in narrow clefts or shielded by stone blocks have the highest rate of potential photosynthesis. These locations are shielded from direct solar radiation most of the time, but the radiation from surrounding stone surfaces is higher than from the atmosphere and heat loss by turbulence is smaller than for exposed locations. These locations also probably have the highest rate of actual photosynthesis.     

Relationships between the diversity patterns of vascular plants,lichens and invertebrates in the Central Asian forest-steppe ecotone

The Central Asian forest-steppe ecotone has been exposed to large alterations in grazing pressure in the last two decades, but the consequences for biodiversity have not been studied so far. We analyzed the biodiversity of the edges and the interior of Siberian larch forests in the forest-steppes of eastern Kazakhstan (Saur, Kazakh Altai) and western Mongolia (Mongolian Altai, Khangai) across different groups of organisms (vascular plants, epiphytic lichens, soil macroarthropods, oribatid mites, moths). The species richness of these groups was related to each other only at the forest edge, but not in the interior. Species richness of vascular plants, soil macroarthropods and oribatid mites at the forest edges was positively correlated. This indicates that these ground-inhabiting groups of organisms responded similarly to the variation in the grazing pressure of livestock, which is kept at spatially varying densities by mostly nomadic or transhumant herders. The species richness of epiphytic lichens was only positively correlated with that of vascular plants, and the richness of the (volant) moths was not correlated with that of any other group. The complete lack of correlation between the diversity of groups of organisms in the forest interior suggests that the diversity of the five studied groups is controlled by specific environmental factors, including light and moisture. Except for the Mongolian Altai, which was subjected to the highest grazing pressure, vascular plants, lichens, soil macroarthropods, and moths had a higher diversity at the edges than in the interior; the opposite was true for the oribatid mites. The latter probably benefit from the higher soil moisture inside the forest, whereas the other four groups are favored by increased availability of light, the proximity to the steppe with a partial mixing of species pools, and the soil macroarthropods also by increased dung abundance.     

Limited effects of early snowmelt on plants,decomposers, and soil nutrients in Arctic tundra soils

In addition to warming temperatures, Arctic ecosystems are responding to climate change with earlier snowmelt and soil thaw. Earlier snowmelt has been examined infrequently in field experiments, and we lack a comprehensive look at belowground responses of the soil biogeochemical system that includes plant roots, decomposers, and soil nutrients. We experimentally advanced the timing of snowmelt in factorial combination with an open‐top chamber warming treatment over a 3‐year period and evaluated the responses of decomposers and nutrient cycling processes. We tested two alternative hypotheses: (a) Early snowmelt and warming advance the timing of root growth and nutrient uptake, altering the timing of microbial and invertebrate activity and key nutrient cycling events; and (b) loss of insulating snow cover damages plants, leading to reductions in root growth and altered biological activity. During the 3 years of our study (2010–2012), we advanced snowmelt by 4, 15, and 10 days, respectively. Despite advancing aboveground plant phenology, particularly in the year with the warmest early‐season temperatures (2012), belowground effects were primarily seen only on the first sampling date of the season or restricted to particular years or soil type. Overall, consistent and substantial responses to early snowmelt were not observed, counter to both of our hypotheses. The data on soil physical conditions, as well interannual comparisons of our results, suggest that this limited response was because of the earlier date of snowmelt that did not coincide with substantially warmer air and soil temperatures as they might in response to a natural climate event. We conclude that the interaction of snowmelt timing with soil temperatures is important to how the ecosystem will respond, but that 1‐ to 2‐week changes in timing of snowmelt alone are not enough to drive season‐long changes in soil microbial and nutrient cycling processes.