birch autecology Flashcards
autecology
= the ecology of a single species
Mountain birch, Betula pubescens spp. tortuosa
- studied at Abisko research station, N Sweden
- occupies sub-arctic boreal forest, 700-850 trees per hectare
- polycormic, 3 trunks on average
- bud burst in late May
- 4-6m tall
- up to 70% biomass below ground
- scaly, sticky buds
- smooth, brownish bark
- monoecious species
- reproduces sexually through catkins
- alternate simple leaves
- longevity up to 500years
weather and meteorology of Swedish lapland
- very dry (rain shadow, 330mm/annum precipitation)
- temperatures below -40C
- winter warming phenomenon from climate change, warm weather for a few days in the middle of winter
resource allocation
= balance between
- root growth
- shoot growth
- sexual reproduction
- repair mechanisms against damage
- defence against plant competition, herbivory, pathogens, pollution
sexual reproduction
- introduces variety of progeny in the future
- seeds allow effective long-distance dispersal
advantages of asexual reproduction
= plants at high altitudes/latitudes favour asexual reproduction as there is only a small sexually reproductive window
- well-adapted genotypes can be preserved and multiplied
- root sprouts take advantage of already existing root system
- no fragile seedling state, good for harsh environments
- rigorous regrowth after disturbance
disadvantages of asexual reproduction
- little variation to cope with fluctuating environment
- root sprouts, disease spreads from old to young individuals of clone, susceptible for fast spread of epidemics also because they are genetically identical
biotic disturbances
- autumn moth
- reindeer
- lemmings, eat plant roots in large numbers when there is a population boom
- moose, eat bark and destroy branches over winter
biotic disturbance, autumn moth
- eggs grown on birch trees
- hatch into caterpillars at the same time as buds burst
- strip trees then ‘parachute’ to ground and strip all ground vegetation including lichen and mosses
- when there are large numbers they destroy all vegetation over a large geographical area
- cycle of population fluctuations from fluctuating carrying capacity every 10yrs, massive peak every 100 years
- warmer winters mean peaks in population occuring more frequently
abiotic disturbances
- changing air and soil temperatures
- extreme events, especially wildfires
- elevated CO2 concentrations
- UV-B radiation from ozone depletion
functions of mountain birch
- dense canopies, good nesting cover
- food source for herbivores and insects
- shaded moist environment below perfect for cryptograms (mosses and lichens)
- root nodules, mycorrhizae
- traditional Sami homes and crafts (historical and socioeconomic significance)
