METHODOLOGICAL APPROACH TO PRODUCTIVITY ASSESSMENT OF HYPOARCTIC SHRUBS ON THE TAIMYR PENINSULA

Сообщества с кустарниковыми ивами в подзоне типичных тундр восточноевропейского сектора Арктики

Tobacco plants (Nicotiana tabacum L.) were grown from transplanting until floral expression in the phytotron units of Southeastern Plant Environment Laboratories to evaluate the relationship between relative growth rate (RGR) and relative accumulation rates (RAR) of N, P, K, Ca, and Mg. RAR is calculated to be analogous to RGR. Plants were grown in both controlled-environment rooms with artificial light and air-conditioned greenhouses with natural light at three temperature conditions and three application rates of N-P-K. RGR and RAR were calculated only for the period of grand growth which occurred within the interval from 7 to 32 days after transplanting. In general, neither RGR nor RAR were affected by temperature or nutrient level. However, both temperature and nutrient level affected dry matter accumulation of the plants apparently by an influence on the rapidity with which plants adjusted to their new environment during the initial 7-day interval after transplanting. RAR for P and K were coequal with RGR of the whole plant; thus, the concentrations of P and K within the plant tended to remain constant during growth. RAR for N, Ca, and Mg were less than RGR for the whole plant; thus, internal concentrations of these nutrients declined during growth. RAR of N, Ca, and Mg for the whole plant were equivalent to RGR of the roots. As a rationale for the association of RGR of roots and RAR of N, it is proposed that the soluble carbohydrate pool in the roots concurrently influences both N absorption, as NO3 -, and growth of new roots of immature plants.

Новые ассоциации и высшие синтаксоны ивняков в восточноевропейском секторе Арктики

Seedlings production is one of the most important stages of the production system and directly influences the performance of the plant in the field. In this sense, the present work aims to evaluate the use of biomass doses of Spirulina platensis and Scenedesmus sp. via root system on the production of yellow passion fruit seedlings. A greenhouse experiment was carried out using a randomized block design in a 2 × 5 factorial scheme (Spirulina platensis and Scenedesmus sp., at the doses 0.0%, 0.2%, 0.4%, 0.8 % and 1% m/v), with four blocks and two experimental units per plot. At 60 days, leaf number, total seedling length, shoot diameter, root system length, shoot length, shoot and root fresh mass, dry mass, root dry mass and total chlorophyll were measured. Spirulina platensis showed superior performance compared to Scenedesmus sp., for the variables stem diameter, shoot length, fresh shoot mass, fresh root mass, dry shoot mass and root dry mass. The doses influenced the number of leaves, root fresh mass, root dry mass, shoot length and fresh shoot mass significantly. The best dose of microalga applied was 0.8% in passion fruit seedlings at 60 days.

As part of a large-scale experiment on the dynamics of boreal forest communities, we examined the effects of experimental manipulations on the spatial pattern of two shrub species, Salix glauca and Betula glandulosa, before and after the population peak of the herbivore Lepus americanus, the snowshoe hare. Despite high rates of twig browsing during the peak, at most sites the basic characteristics of the spatial pattern recovered quickly. Only where food addition and predator exclosure enhanced and prolonged the hare density peak was there a sharp decline in the intensity of spatial pattern of the preferred winter food plant Betula. The spatial pattern of these shrubs is resilient to normal changes in herbivory and may persist, therefore, for decades through several hare population cycles. Key words: Betula glandulosa, Lepus americanus, Salix glauca, spatial pattern.

This study investigates effects of reducing the ambient UV radiation on gas exchange and chlorophyll fluorescence of two shrub species, Salix arctica and Vaccinium uliginosum, in a high arctic heath in Northeast Greenland in July and August. On two sites films, Mylar and Lexan, were used to reduce UV-B radiation and UV-B + A radiation, respectively. A UV transparent film, Teflon, and no film were used as controls. Field measurements showed that the plants under Teflon, Mylar, and Lexan received approximately 91, 39, and 17% of the ambient UV-B irradiance, respectively. Reduced UV radiation increased maximal photochemical efficiency (F v /F m ) in both species. The responses varied in significance according to species, sites and time of growing season. Net assimilation (P n ), measured as net CO2 uptake, was not significantly affected. But over the whole growing season stomatal conductance and intercellular CO2concentration were decreased by both UV treatments. The underlying mechanisms for these results are discussed. PAR-irradiance had a negative influence on the absolute values of F v /F m . A positive correlation was found between F v /F m and P n measured at ambient CO2-level. It is concluded that it cannot be excluded, that the observed short-term effects could result in long-term negative effects on growth and survival for the investigated species.

Purpose : identification of plant potential, ecological and economic suitability of deer pastures of the forest-tundra zone located in the zone of anthropogenic influence Material and methods . Ground geobotanical survey of the vegetation cover of deer pastures was carried out by route method in accordance with the method of geobotanical studies. The ecological and economic value of each type of pasture was determined based on the data of the ecological and economic classification of deer pastures in the north. Results . 25 species of reindeer pastures are described on the right bank of the Norilsk River in the northwestern part of the Putorana Plateau. On the basis of signs of uniformity in the structure of vegetation (proximity of species composition, similarity of vertical and horizontal structures), they are combined into 4 types: tundra, swamps, shrubs and light forests. Tundra (30.9%) and shrub (27.6%) types of pastures dominate. The most important feature is the active participation in the structure of phytocenoses of shrubs (Betula nana s. str, Salix glauca s. str, S. lanata s. str.) and shrubs (Ledum palustre. Vaccinium uliginosum s. str, V. vitis-idaea s. str.). Green fodder is most nutritious in the first half of summer. The nutritional value of fruticose lichens does not change during the year. Reindeer pastures with lichen cover and high (from 5 to 12 o-days/ha) reindeer capacity during the snowy period occupy insignificant (24.3%) areas. Basically, these are willow and dwarf dwarf shrub-lichen tundras and larch sparse forests of dwarf-shrub moss-lichen. The participation of lichens in the ground cover of plant communities does not exceed 25–35%. The following lichen species have been recorded: Cladonia arbuscula, C. stellaris, C. rangiferina, C. cornuta, C. deformis, C. mitis, Cetraria cucullata, and C. islandica. The most widespread species of the genus Cetraria: Cetraria islandica and C. cucullata, with a clear advantage of the latter. The main forage species of the genus Cladonia (Cladonia arbuscula, C. stellaris, C. rangiferina) are not widely distributed. Pastures with a high (from 9 o-days/ha to 14 o-days/ha) reindeer capacity in the summer, early autumn and late spring periods prevail in the study area. Basically, these are communities of shrub and marsh types. Shrubs (Salix glauca s. str, S. lanata s. str., S. hastata, Betula nana s. str.), shrubs (Salix reticulata, Vaccinium vitis-idaea s. str.) and forbs (species of the genera Petasites, Pedicularis, Astragalus, Hedysarum, Equisetum, Bistorta).

The main purpose of this investigation was to describe the spatial arrangement of shoot tissues, as seen in transverse section, and allometric relationships in two contrasting species of Polygonatum i.e., Polygonatum odoratum which commonly grows in mixed pine-oak forest with shoots rectangular in shape, and Polygonatum multiflorum found in oak-hornbeam forest with cylindrical shoots. The mass and length of the aerial shoots of each individual plant were measured. The shoot regions of each plant were then categorized as basal (b), central (c) or apical (a). Transverse sections of these shoot regions were subsequently cut, and the following parameters were measured: (1) Diameter of shoots, (2) thickness of the outer and inner zones of parenchyma and (3) thickness of the sclerenchyma zone. Additional allometric relationships between the various measurements were computed and determined as Pearson’s correlation coefficients (r). Both species of Polygonatum differed significantly with respect to the length, diameter and thickness of the outer zone of parenchyma. Shoots of P. multiflorum were taller but narrower than those of P. odoratum, which had a significantly wider zone of outer parenchyma. Allometric relationships were stronger for P. multiflorum, and for both species, they were generally stronger in the basal part of the shoot. We conclude that in P. multiflorum, the strong correlation between the diameter and length of the shoot seems to be important to the growth in shaded environments.

SUMMARY . i (1) We investigated interactions between snowshoe hares (Lepus americanus) and their food plants in winter during a cyclic fluctuation in numbers at Kluane, Yukon, between 1977 and 1985. • (2) The winter diet of hares at Kluane was dominated by four species of shrubs and trees. Betula glandulosa, the most preferred species, was common on only four of nine study plots. Salix glauca was eaten most often in mid-winter, when Betula was covered by snow. Where Betula was absent, Salix was eaten at or above the level expected from its relative abundance. Picea glauca was generally not preferred, but was eaten, especially where Betula was absent. Shepherdia canadensis was eaten fourth most often. (3) By the peak of the cycle in the winter of 1981-82, hares had removed much of the biomass of small twigs of Betula glandulosa and Salix glauca from three study plots. Hares had little effect on the biomass of Pice a glauca twigs. The biomass of these three species on two control plots at the end of the 1981-82 winter was, however, still sufficient to support the hares residing there. A larger population of hares on a third plot with added food depleted their supply of natural foods more severely. ( 4) An analysis of the fates of tagged twigs showed that hares browsed an average of 63% of Betula glandulosa twigs, 26% of Salix glauca twigs, 20% of Shepherdia twigs, and 14% of Picea glauca twigs in the winter during the 3 years of peak density. At the peak in hare numbers in 1981-82, over 80% of Betula twigs were eaten. Twigs within 50 em of the ground were browsed most often. (5) Heavily-browsed Betula glandulosa bushes grew new twigs rapidly after hare numbers had declined. Salix glauca showed less terminal regrowth, but produced stump sprouts, which we did not measure. Picea glauca and Shepherdia were not heavily browsed, nor did they grow faster after browsing by hares. (6) Adult hares became heavier in spring as numbers rose, and then lighter as their numbers declined. The latter effect was absent on plots with added food. Growth rates of juvenile hares in summer and autumn declined as hare numbers rose, but did so more slowly on two plots where food was added. Juveniles lost mass in winters of peak density, but did not do so on two plots with added food. The growth rates of juvenile hares recovered within 2 years of the decline. (7) Our results suggest that snowshoe hares at Kluane did not experience an absolute food shortage in winter at peak densities. Also, radio telemetry studies at Kluane showed that most hares died of predation, not starvation. We suggest that a relative food shortage

Summary Primary production in Arctic and Antarctic lakes is typically dominated by benthic photosynthetic organisms. These include aquatic mosses that can be very abundant although they must be able to tolerate extreme seasonal climatic variation in irradiance and temperature. Climate change is expected to cause increased nutrient run‐off and to prolong ice and snow cover on Arctic lakes. Despite the substantial role that aquatic mosses play in Arctic and Antarctic lakes, our study is the first of its kind to study the in situ growth and nutrient‐use efficiency of an Arctic aquatic moss, Drepanocladus trifarius, and how the net production of this species is coupled with a range of climatic factors undergoing change. Here, we verify the use of growth segments as a technique to record historic growth. We then used the method to reconstruct the growth of D. trifarius by comparing in situ measured growth with that determined from growth segments after one year's growth in a high Arctic lake. Finally, we determined nutrient‐use efficiency, resorption efficiency and resorption proficiency by measuring the tissue nutrient content in different annual growth segments. The observed annual mean production of D. trifarius was about 2–3 mg DW shoot−1 year−1 expressed as biomass increase and 10–30 mm shoot−1 year−1 expressed as length increase, while the age of most shoots was 7–10 years. About 90% of the variation in annual net production was explained by between‐year variability in snow prolongation and net radiation in June. The low tissue‐N (1.05%DW) and tissue‐P (0.081%DW) contents found in D. trifarius suggest that its growth in Lake Sommerfuglesø is limited by the availability of N and P during summer when the availability of light is sufficient for extensive growth of this species. P resorption was 43% in D. trifarius, whereas no N resorption was recorded, and P proficiency ranged between 0.02 and 0.04% DW, which is comparable to the concentrations measured in other plant types under P limitation, suggesting that P resorption is an advantageous trait for the existence of moss in this oligotrophic environment. Our results suggest that predicted prolongation of snow cover and consequent decrease in net radiation in lakes will decrease annual net primary production. Our results also suggest that species able to exploit elevated nutrient contents have an advantage in more nutrient‐rich lakes in future and indicate that dominance patterns may change. We therefore foresee that climate change will have dramatic effects on the annual net production of mosses and thus whole lake primary production in Lake Sommerfuglesø and similar lake types dominated by mosses in the high Arctic.

Piper aduncum L. (Piperaceae) has great potential for economic exploration because of the proven use of its essential oil in the agriculture and in the human health. A technique that improves its propagation, as the tissue culture, becomes necessary. Some parameters must be determined for the successful cultivation in vitro. Thus, this study aimed to determine the salts concentration of MS medium, temperature, luminosity and light quality for in vitro culture of this species. The following treatments were conducted: 1/4MS, 1/2MS, MS and 2MS; 20℃, 25℃, 30℃ and 35℃; monochromatic blue, red and white lights and the combination of red and blue, using light emitting diodes (LEDs); luminosities of 17, 37, 48 and 73 μmol·m-2·s-1 obtained with cool white fluorescent lamp. After 35 days, the treatments were analyzed. To determine the salts concentration of MS, the variables were evaluated: number of shoots, leaves and roots, length and width of leaves, length and dry mass of root and shoots and percentage of death by necrosis. To the plantlets under different temperatures, length and dry mass of shoot and root, number of shoots, number, length and width of leaves and survival and rooting percentages were measured. The plantlets that were maintained under different luminosities were evaluated for length of shoot and root, dry mass of leaf and root. To evaluate the growth under the LEDs, the length and dry mass of shoot and root, number of shoots and roots, percentage of rooting and sprouting were assessed. The medium 1/4MS and the medium 1/2MS showed better responses for number and length of root, leaf width and shoot length. The temperature 25℃ provided the highest number of leaves, length of shoot and root, root dry mass and rooting percentage. The luminosity 73 μmol·m-2·s-1 provided higher values in length of root and dry mass of leaf and root. The red LED provided plantlets with greater growth. Thus, for the in vitro cultivation of Piper aduncum, 1/4MS, environment temperature of 25℃, light intensity of 73 μmol·m-2·s-1 and environments with red light to obtain high quality plantlets for propagation of this species are recommended.

The relative fuel-potentials of 12 northern tundra and forest–tundra ground species of the Mackenzie delta area were evaluated from measured fuel characteristics by simulating a test fire with the Rothermel (1972) fire behavior model. The relative importance of the fuel parameters were in decreasing order: moisture content, biomass, fineness (surface/volume ratio), packing ratio, silica-free ash content, and caloric content. The fuel-potential ratings of the vascular species and of the communities were differentiated primarily by their leaf characteristics. Dead leaves of Calamagrostis canadensis and Eriophorum vaginatum constituted the most flammable fuels measured. Evergreen Ledum palustre and Empetrum nigrum were clearly differentiated from the live vascular species by higher flammability ratings. Of the cryptogam fuels, Cladonia-type lichens were rated intermediate between the above evergreen ericoids and the deciduous woody species (Betula glandulosa, Vaccinium uliginosum, Salix glauca), while Sphagnum sp. was rated comparable to the latter groups. Epilobium angustifolium received the lowest ratings of all species.Subject to the limitations with respect to ether-extractive contents, the relative fuel potential of tundra and forest–tundra plant communities can be rated on measured fuel characteristics, community composition, and the criteria of the Rothermel model. Possible applications of this study were raised, particularly the use of relatively nonflammable plants in land management.

Controls on leaf wax fractionation and δ2H values in tundra vascular plants from western Greenland

Due to the above global average warming, the winter climate in West Greenland is increasingly characterized by warm spells causing snow melt and soil exposure. These events might activate soil microbes and associated nutrient cycles, with consequences for the tundra ecosystem, even in the following summer.Here we studied effects of winter warming in a dry heath tundra ecosystem in Blæsedalen on Disko Island, West Greenland near Arctic Station, characterized by low shrub vegetation (Betula nana, Salix glauca, Vaccinium uliginosum, Empetrum nigrum, Cassiope tetragona). We established replicate 0.5 m2 plots equipped with custom-made heating probes that were pre-installed in the growing season aiming to warm up the surrounding soil in the following winter campaign to a depth of 15 cm during a week. Nitrogen (N) transformation pathways from organic N (proteins and amino acids) to ammonium (inorganic N) and microbial N uptake were quantified in the tundra soil using 15N labelling techniques, accompanied by greenhouse gas flux measurements.In situ warming resulted in soil CO2 loss, and activated microbial CH4 uptake. Under laboratory conditions, we could also detect several freeze-thaw induced emission peaks of N2O and N2. For the first time nanoSIMS analysis revealed rapid soil microbial uptake of amino acid alanine into microbial cells in winter soils. Furthermore, optical microscopy and Raman spectroscopy analysis of microbial communities provided insights into both their immediate response to the warming and into memory effects in the following growing season, with increased microbial activity in the samples taken from plots that have been warmed.In sum, we highlight a fast activation of microbial N turnover due to Arctic winter warming events, which results in changes in nutrient cycling that persist in the following growing season.

Rapid climate change in the Arctic may increase sexual reproduction in plants because of changes in both abiotic factors, such as temperature, and biotic factors, such as pollination. Pollination may currently limit plant reproduction in the Arctic, where cold temperatures hinder pollinator activity. To understand how warming may affect pollination and plant reproduction, we studied three plant species in western Greenland. Two species were hermaphroditic and insect-pollinated (Vaccinium uliginosum and Chamerion latifolium), and one was dioecious and insect- and wind-pollinated (Salix glauca). We measured how pollinator visitation and plant reproduction varied across three temperature zones. We also conducted pollinator exclusion and pollen supplementation experiments to measure pollinator dependence and pollen limitation. Proportion of fruit set in Vaccinium and Salix was pollen limited in every temperature zone, and Vaccinium and Chamerion depended on pollinator-mediated outcrossing for maximum reproductive success. Furthermore, higher pollinator visitation to Vaccinium in the warmer temperature zones mirrored lower pollen limitation and higher fruit set, suggesting that temperature zone indirectly influenced reproduction via changes in pollination. Taken together, our results demonstrate that both abiotic factors and pollination are important in limiting reproduction in the Arctic and that plant–pollinator interactions can mediate the response of plant reproduction to warming.