Lecture 3 - World Biomes

biomes w/ few trees

tundra, desert, grassland, savanna

no trees or a few that are widely spaced

**what do they have in common: low rainfall

closed canopy tree cover biomes

boreal, temp deciduous, trop deciduous, temp rain forest, trop rain forest

**all forests receive at least moderate rainfall (100-150cm or 40-60in/yr)

mean annual temp

it tracks latitude

tundra

cold, dry areas, betwene treeline and ice caps

few species but tend to be uniqeuly adapted to cold and only live in arctic/antarctic regions

polar bears, arctic fox, lemmings, caribous

plants grow low to ground (licens, mosses, grasses, shrubs)

low productivity

areas w/ fewest fires (cold, many fire breaks, low fuel load)

boreal forest/taiga

coniferous and broadleaf trees, not usually taller than 30m

¼ to 1/3 of all forests are boreal

half of all boreal forests in canada

no land mass at an equivalent latitude in southern hemisphere for forests to grow so only in norhtern hemisphere

grassland, shrubland, scrubland, woodland

these biomes all have few trees but enough precipitation and warmth for moderate productivity of many other plants

these biomes grade into each other, with different proportions of many of the same kinds of plants (grasses, shrubs, herbs, some trees)

shrublands

about as productive as savanna

summers are hot and dry

shrubs, grasses, herbs

adapted to fire, caused by frequent lightning

grassland

can be more productive than shrublands because grass grows quickly each year

roughly 80% of fires globally occur in grasslands each year

native grasslands like the great plains prairies were very biodiverse but most of these original ecosystems have been lost to agriculture

found on every continent except antarctica

desert

defined by precipitation less than 50cm per year although many get less than 10 cm

more bare ground than vegetation - low productivity

some seeds can survive waiting 100 years for rain to sprout

desert and semidesert cover about 1/3 of earth’s land surface

most are between 20-30 deg N or S, where atmospheric circulation patterns mean the air is dry

deserts can be cold or hot

savanna

hot dry areas

mixed woodland and grassland - some trees but open canopy

acacia trees in african savanna; eucalyptus in australia

more productive than tundra or desert, but still low productivity

some savanna commuities experience fires every 1-5 years (few firebreaks in topography; dry and hot; fast-growing plants for fuel load)

closed-canopy tree cover (forests)

boreal forest

temperate deciduous forest

temperate rain forest

tropical deciduous forest

tropical rain forest

deciduous vs rain forest

deciduous = moderate amount of annual rain/snowfall

rain forests = receive the most precipitation of any biomes

temperate vs. tropical forests

temperate = areas w/ moderate avg temperature, and more seasonal temperature changes (cold winters and hot summers)

tropical = areas with hot average temperature, doesn’t change a lot over the year

temperate deciduous forest

moderate temperature, moderate precipitatino

four seasons: leaves fall in autumn and grow back in spring

mid-latitudes: easten US and canada, europe, china, japan

many species of plants: broadleaf trees i.e. oak, maple, beech

temperate rain forest

mild climate - heavier rainfall

**somewhat warm all year but seasonally rainy (winter) and foggy (summer)

between coasts and mountains

sitka spruce, douglas fir, hemlock, maple, salmonberry, huckleberry

many ferns and mosses

**least common of the forest types bc it requires very specific conditions

tropical deciduous forest

warm all year, but moderate rainfall (rainfall is seasonal)

trees drop leaves in dry season

occurs to the north and south of tropical rainforests

tropical rainforest

highest average temperature and highest average rainfall of any biome

up to twice as productive as any of the other forests

forest productivity based on type

temperate deciduous, temperate rainforest, and tropical decisuous are all about the same productivity

tropical rainforest = up to 2x as productive as the other ones

boreal forests = least productive per unit area