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Plant survival in the Arctic after R.M.M. Crawford

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Plant survival in the Arctic after R.M.M. Crawford

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    1. Plant survival in the Arctic (after R.M.M. Crawford)

    2. Polar areas covering 16.5% of the Earth’s surface water availability extremes and rapid fluctuations in environment (water states) north and south polar regions differ (geology, energy transport and balance)

    3. Arctic and Antarctica Arctic covered by Arctic Ocean (90% multi-year ice), connected to temperate oceans, transport and exchange of heat energy is affected + input of heat from oceanic currents = cyclones, low pressure Antarctica, a huge continent located at the center of the South polar region, regular movement of air masses, nightless summer + sunless winter, 24 hour radiation in summer brings daily more energy than on the equator But the sum of energy during the year is low *Arctic 3 mil.y.a. and Antarctica 25 mil.y.a. => Antarctic sea weeds are better adapted than Arctic macroalgae

    4. Arctic tundra 5.5% of the Earth’s land surface influenced by man minimally low temperature short growing season limiting factors: thermal input water nutrients

    5. Phytogeographical division Low Arctic - shrubs, graminoids Hight Arctic - sparse vegetation - dwarf evergreens, rossete and mat herbs

    6. Polarity: wet and dry habitats soil drainage dry habitats - dormant earlier wet habitats - overwintering buds protected in wet mud - growth continues until the very last days of summer

    7. Temperature problem convenient are sheltered habitats sun-tracking activity of flowers flowers – parabolic shape (attract pollinators, speed up development and reproduction) papillose epidermal cells act as lenses compact rosettes, hairs

    8. Photosynthesis high rates of photosynthesis and growth (˜ temperate plants) but for a shorter time - exclusively C3 plants - high activity of enzymes (= metabolic compensation) - lipids as storage? NO! >cuticle

    9. Carefully controlled allocation of carbon > growth > reserves (northern plants more C to underground organs) northern plants show a high rate of respiration – fast mobilization of storage substances High respiration as the reason for southern limits to the distribution of Arctic plants

    10. Plant Nutrients soils 1. skeletal soils of screes, dunes 2. peat (bogs, sedge medows) limited inputs of nutrients (almost no chemical weathering), only 1 % of nutrients in living biomass >precipitation >biological sources (e.g., animal excrements) the slowest cycling of nutrients exception: nutrient-rich bird cliffs

    11. nitrogen - wet sites – cyanobacteria - cyanobacteria associated with lichens - Dryas drummondii – N-fixing nodules phosphorus - from snowfall and precipitation (P, Ca content of vegetation may affect population dynamics of lemmings)

    12. Reproduction sexual reproduction 10 000x more energy - costly than asexual reproduction 80% of Arctic species perform asexual reproduction (stolons, rhizomes, apomixis) often sexual and asexual reproduction together Completion of the sexual reproduction over several seasons (even 7 or 8 years)

    13. Altitudinal limits to the survival of trees and shrubs (after R.M.M. Crawford)

    14. timberlines: both evergreen conifers and deciduous broad leaved trees limiting factors: similar to Arctic plants, especially a short growing season (but no permafrost)

    15. Tropical timberlines cloud zone: humid climate and stable temperature > little rainfall higher up timberline not well defined (smaller trees…shrub…mountain desert)\ pachycaul plants – woody forms of normally herbaceous plants (Echium, Senecio, Lobelia) – protection against fluctuating temperature Pinus canariensis – long needles – absorbtion of humidity, dew

    16. Temperate timberline 1. abrupt timber-line - critical stage: seedling establishment - shade-tolerant trees (Nothofagus) under protection of parental trees - New Zealand, S America 2. ecotone timber-line - twisted trees (=Krummholz) - above snow cover branches exposed to damage - Europe, N America - twisted forms genetically fixed, - special growth regulators (scopulin…)

    17. Deciduous X Evergreen Deciduous trees and shrubs: - investment to new photosynthetic organs every season - less dangerous during winter Evergreen trees and shrubs: - longer time for photosynthesis - freezing risk during severe winters

    18. Altitude of timberline Altitude of timberline decreases by 80m with 1° poleward S hemisphere: timberline lower then in the N hemisphere (Tyrol 47°N: 2300m X Ands 47°S: 1100m) tree height is not smaller at the timber-line

    19. Temperature effect on tree growth Koppen’s rule: Tree growth requires a minimal summer warmth represented by the mean daily maximum temperature of 10°C for 1 month Betula – t > 6°C X Pinus –July, August t

    20. Reproduction Populus tremula – vegetative reproduction Sorbus aucuparia - lighter seeds but higher growth rates (higher respiration rate)

    21. Essential features of mountain plants: plants from lower altitudes - earlier bud break; plants from higher altitudes – delayed bud break, but faster life cycle crucial for survival: to develop sufficient protection and reserves (thick cuticle, carbohydrate storage, etc.) consequently: long-living trees and shrubs as well as perennial herbs are common in the mountain flora

    22. Thank you for your attention! Arctic and mountain plants are admirable!

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