Biogeography - BIOMES

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Geographical Biogeosciences
GEOB 102
Greg Henry

GEOB 102 BIOMES Biomes 1: Introduction biome • largest division of the terrestrial ecosystem • regional-scale ecosystems • related to climate and soil type life form- mode of existence, physical size, and structure annual mode of existence: one life cycle in one growing season (seed germinates, plant grows, reproduces, then dies) perennial mode of existence: lives more than one growing season, reproduces more than once Growth Form Mode of Existence Size, Structure and Shape trees perennial large wood structures with a single stem lianas perennial grow on trees, extend roots into trunk, and are found in tropical areas shrubs perennial grown on ground, multi- stemmed, wood, shorter herbs perennial and annual small, non-woody plants perennial mosses, blanket the floor of the forest, grow up on stems, non-vascular, get bryophytes water by being close to the ground epiphytes perennial supported by other plants -there are taller trees in the understory because of more life There are six principle biomes: 1. forest 2. savanna 3. shrubland 4. grassland 5. desert 6. tundra biomes are further divided into formation classes Biomes, Climate and Soils Ecosystem determinants –factors that determine ecosystem characteristics Vegetation characteristics = f ( CL + O + R + P + T) CL = climate (energy and water = water balance) O = organisms (litter + bacteria + (other decomposers) > nutrients) R = topographic relief (elevation, slope, aspect) P= parent material or geologic substrate (rock) that is the basis of soil T = time since disturbance CLORPT also relates to vegetation characteristics CL = climate and soils = factors responsible for general similarities in vegetation and sub-continental or regional scales = biomes and formation classes ORPT = local scale factors which cause variation between sites = habitats Global climate determines biomes and formations o classified based on temperature and moisture Tropical Rainforests AClimates Savanna Deserts B Climates Broadleaf and mixed forest C Climates Temperate Rainforest Grasslands D Climates Needle-leaf forests Arctic and Alpine Tundra E Climates Forest Biome o Low-latitude rainforest o Monsoon forest o Subtropical evergreen forest o Mid-latitude deciduous forest o Sclerophyll forest o Needle-leaf forest Forest Formations Forest formations with a positive water balance in the growing season: - water and energy are available = positive water balance in growing season - equatorial forest/tropical rainforest (evergreen) - subtropical evergreen forest (evergreen) - tropical seasonal forest/monsoon (deciduous) - midlatitude deciduous forest (deciduous) forest formations with a negative water balance in the growing season: -water limited (winter-wet) or energy limited (long, cold winter) -energy or water limited = water deficit in growing season - sclerophyll forest (evergreen) - needleleaf forest (evergreen) Biomes 2: Needleaf Forest of BC ─ Coastal Temperate Rainforest o Needle-leaf forest ⋅ Coastal temperate rainforest ⋅ Montane Forest ⋅ Boreal Forest Location - 40-65° latitude (including Vancouver, Vancouver Island, coastal BC) - windward west coasts of continents Climate Temperature - maritime, cool summers, moderate winters Precipitation - abundant annual precipitation winters = mild & wet summers = warm & dry Water Balance - summer water deficit, despite high total annual precipitation Soils - Podzolic Order - accumulation of leaf litter, leaching of the Ae horizon due to rain podzols - leached Ae horizon - abundant leaf litter - locally variable local variation - Geysolic (water logged) -  Organic (bogs) Vegetation Characteristics Productivity: high Life-forms: trees, shrubs, herbs, epiphytes, bryophytes Vegetation structure - large trees, multiple canopy layers Adaptations • large size, long life span • shade-tolerance - trees can regenerate beneath canopy of old forests • nurse plants (logs) - seedlings grow on downed logs o old growth forest attributes – caused by fine-scale disturbances/ “gap” dynamics o historically >90% coast forests >250 yrs old = “old growth” o does old growth = climax ? no Disturbance Why are fires so infrequent? o Soil moisture due to abundant precipitation Human Impacts urbanization - conversion of forest = change in land cover = permanent loss of forest industrial forestry (clearcuts) versus old-growth = change in land use = forests remain, but change in structure and composition eg. central Vancouver Island Biomes 3: Needleleaf Forests of BC ─Interior Dry Forests Location - 40-65° latitude (including the Okanagan, Cariboo, Kootenays) - leeward (towards side in which wind blows on) of mountain ranges, continental locations Climate Temperature - continental, cold winters and hot summers Precipitation – dry land, leeside of mountain ranges (rain shadow), dry year round, especially summer , low precipitation Water Balance - pronounced summer water deficit Soils - Brunisolic, Luvisolic and Podzolic Order o Brunisols = younger or slower developing soils in colder environments o Luvisols = leaching of theAe horizon on basic parent material o Podsols = leaching of theAe horizon on acidic parent material o underlying bedrock is an important factor Vegetation Characteristics Productivity: moderate Life-forms: trees, shrubs, herbs, epiphytes, bryophytes Vegetation structure - large trees, multiple canopy layers Adaptations Adapted and tolerant of drought and fire - Drought - Fire - thick bark, fire scars (Douglas-fir, ponderosa pine, larch) - serotinous cones, seed dispersal (fire melts waxy coating and releases seeds) and germination (lodgepole pine) Disturbance Fire (changes with elevation) Elevation Low Intermediate High Forest Type submontane montane subalpine Fire Frequency high mixed low Fire Severity low mixed high Human Impacts fire suppression Research is low Need to Restore high ongoing low Insects – eg. mountain pine beetle Human Impacts urbanization - conversion of forest grazing and ranching industrial forestry fire exclusion climate change Biomes 4: Savanna 2 formations: savanna woodland thorn tree-tall grass savanna Location - transition between forests and grasslands or deserts ofAfrica and South America - Sahel and Serengeti Plains (Africa), - llanos, campo cerrado and pantanal (SouthAmerica) Climate Tropical Wet-Dry Precipitation - less than in other tropical climates (900-1800 mm/yr) - distinct wet-dry seasons due to migration of ITCZ -  dry season = winter/spring (subtropical high) -  wet season = summer/fall (ITCZ low = cloud and rain) Temperature -  dry season = cool temperatures initially -  early spring, prior to rain = dry, hotter Moisture Balance: - Winter = cool dry - Spring = hot -  Summer = warm + wet Is there a water deficit? substantial water deficit If so, when? during dry season Which season is most conducive to fire? peaks in spring Soils - range of fertility, often deepAh horizons -  riparian zones = rich soils -  annual floods in wet season deposit fertile silt Vegetation Characteristics Productivity: - variable, depends on precipitation + water balance Limited by: - soil water in dry period Life forms: trees, shrubs, and herbs (especially grasses) adapted to dry conditions Dominant Vegetation: rain-green vegetation - produce leaves and flowers during wet season Adaptations: Drought Resistance - deciduous leaves conserve water during dry season - grasses dieback during drought Savanna woodlands: - open forest, widely-spaced trees with mainly grass understory - variable mixture of woody and herbaceous plants - depends on climate-soil-fire-herbivory interactionsDrought resistance Disturbance Fire - frequency highest in tropical savanna and grassland biomes = 2-10 yrs - susceptible during spring drought at end of winter dry season Herbivory - large herds of migratory grazing ungulates (zebra, antelope, wildebeests) Disturbance adaptations - coarse-barked trees with thorns to deter herbivores - sprouting = adaptation to herbivory and fire Human Impacts - land use change – agriculture and domestic livestock around settlements - roads and fences, fire
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