terrestrial biome

biomes

• large scale terrestrial communities, shaped by physical environment, categorized by dominant plant growth forms and characteristics

• plants occupy sites for a long time, good indicator of climatic conditions and disturbance

how do plants help describe climatic conditions

• taken many forms n response to selection pressures such as aridity, extreme temperatures, intense solar radiation, grazing, crowding

• biomes are delineated by growth form, not relatedness

• convergence evolution of similar growth forms among distantly related species in response to similar selection pressures

How many biomes are there?

• 9 biomes divided by annual precipitation and temperature climatic zones

  • similar assenblages on distant continents, similar responses to climate conditions/ change

• complexity arises:

  • seasonality, extremes

  • salinity

  • soil properties/ chemistry

  • species interactions

climate diagrams

• climate diagrams: graphs of average monthly temperature and precipitation at a location

• every 1C corresponds to 2mm of precipitation

  • more water loss occurs at higher temps so you need more precipitation

  • also show below 0C

tropical biomes

• temperature is warm and constant

• precipitation exceed 2000mm/ yr

• may have wet/ dry seasonality

• biotic interactions important

• 50% of earths species, 37% of earth’s carbon. 11% of terrestrial surface

• nutrient poor soils

• diverse plant life forms: emergent trees, canopy trees, lianas, epiphytes, understory

  • adaptations: butresses, waxy leaves with drip tip

tropical seasonal forests and savannas

• annual temps warm and constant

• precip seasonal

• shorter fewer trees more grasses/ shrubs

• tropical dry forests, thorn woodlands, tropical savannas

• recurrent fires, large herbivores africa), floodplains inluence grass dominance

• deforestation

• adaptations: drought decidious, ant acacia mutualism

desserts

• high temperatures, low water availability

• correspond wth high pressure zones of hadley cells

• can be fairly diverse

• humans have used deserts for grazing desertification and salinization

• adaptations:

  • succulence

  • drought decidious

  • short annual life history

temperate grass lands

• grass dominated landscapes

• seasonal temp variation and periods of subfreezing

• similar climate as deciduous forest, but less rainfall

  • fire and grazing maintain grassland

• rich organic soil

• many converted to agricultural land

  • tall grass prairie 5% remaining

  • desertification, salinization

• adaptation

  • high rot:shoot ratio

  • basal meristems

temperate shrublands and woodlands

• open canopy, short trees

• hot/ dry summers/ cool wet winters

  • medditerranean climate or rain shadow effects

• nutrient poor soils

• fire (30-40 year interval)

• adaptations evergreen leaves, sclerophyllous leaves

• cheatgrass problem especially for fires

temperate deciduous forests

• moist fertile, freeze in winter

• oaks, maples, beech

• verticle structure

• agriculture, very little old growth remains

• adaptations

  • deciduous leaves, deal with freezing

• northern hardwoods

• southern hardwoods

  • bottomland hardwood

  • bald cypress swamps

  • southern mixed mesophytic

temperate evergreen forest

• high range of precipitation (50-400 cm)

• includes the temperate rainforests (OR, WA), coastal forests (CA), fire maintained pine flatwoods (LA)

• leaves acidic and nutrient poor

• douglas fir, pines, junipers, eucalyptus, podocarpus, monkey puzzle tree

• important fro wood paper production extensively cleared little oldgrowth remains

• adaptations

  • needle-leaved trees (year long growing season, low nutrients)

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boreal forest (taiga)

• continuous subfreezing temperature for many months

• only in N hemisphere, 1/3 of earth’s forested land

• permafrost: subsurface soil layer that impedes water drainage

  • cold and wet soil, slow decomposition, large carbon stores

• fire

• spruces, pines, larches, birches

• adaptations

  • conifers have vascular tissu better for thawing and freezing,

tundra

• very low growing season temps, low precipitation, short growing season

• wet soils, permafrost

• sedes, forbs, grasses, low growing shrubs, lichen, moss

• adaptations

  • low growing, out of wind microclimate

  • rough leaves

what happens with biological communites on mountains?

• resemble the biomes that form along latitudinal gradient

• alpine zone, subalpine zone, montane zone, lower montane zone