Eco - Biomes

biome definition

a biome is a large scale land (or water) area occurring in several parts of the world, that is characterized by the form of the organisms and climate in that area

what are the two primary ways of categorizing and studying large scale patterns of biodiversity?

biodiversity - evolutionary history and patterns of related species

biomes - convergent evolution of species with similar adaptations in similar climates; classification by functional types of the organisms

convergent evolution

process by which unrelated organisms evolve a resemblance to each other in response to common environmental conditions (often partial or incomplete)

why do different adaptations occur in biomes with different climates?

this occurs because no single type of organism can survive and reproduce in the entire range of conditions on Earth

forests vs woodlands

forests - trees dominate, continuous canopy

woodlands - trees dominate, canopy open

savannas vs grasslands

savannas - tropical grassland; scattered trees

grasslands - grasses dominate, but many other non-woody species present

shrublands vs deserts

shrublands - multiple-stemmed, shorter woody plants dominate; generally continuous plant cover

deserts - large areas of open ground; many different plant forms possible, many annuals

tropical rainforests characteristics

• between 10 degrees N and 10 degrees S

• annual precipitation > 2000 mm

• no seasonal changes

• high biomass, high diversity - about 50% of Earth species

• broadleaved evergreen and deciduous trees

where do tropical forests occur?

Central and South America, Africa, Southern and Southeastern Asia, Oceana, and Australia

tropical forests characteristics

• high species diversity

• high productivity

• threatened by human urbanization and harvesting of plants and animals

• occupy a relatively small area globally

where do tropical rainforests occur?

they occur where the ITCZ occurs (area where the northeast trade winds from the northern hemisphere and the southeast trade winds from the southern hemisphere come together)

can be highly seasonal; always warm and have high rainfall

temperate evergreen forest characteristics

• 30 degrees to 50 degrees N and S, coastal, continental, and maritime zones

• lower diversity than tropical and deciduous forests

• leaves tend to be acidic, and soils nutrient poor

• smallest biomes, typically have low diversity and high productivity

• threatened by logging

where do temperate rain forests occur?

they occur in Western North America, Southwestern South America, and others

temperate deciduous forests characteristics

• 30 degrees to 50 degrees N, on continental edges with enough rainfall for tree growth

• leaves are deciduous in winter

• oaks and maples occur everywhere in this biome

• species diversity lower than tropical rainforests

• warm summers and cold winters (highly seasonal)

• productive and moderately high in productivity

where do deciduous forests occur?

they occur in Europe, Asia, and North America

where were american chestnut trees dominant and what threatenes them?

they were once dominant in North America and were killed off by logging and a fungal disease (Chestnut blight)

temperate and tropical grasslands compare and contrast

both have extended dry season, regular fires, productive, and diverse’

temperate - warm summers, cold winters

tropical - hot summers, warm winters

temperate grasslands characteristics

• 
  

between 30 degrees and 50 degrees latitude

warm, moist summers and cold, dry winters

grasses dominate; maintained by frequent fires and large herbivores

prairies and temperate grasslands

• perennial grasses with many different dicot species

• high light above, dark below

• less rainfall than forests

• frequent fires

• litter - thick decaying organic matter

• large amount of biomass belowground

• deep and fertile soils

why is fire important?

fire is important for habitat diversity and structure

tropical seasonal forests and savannas characteristics

• north and south of the wet tropics

• wet and dry seasons associated w/ movement of the ITCZ

• shorter trees, deciduous in dry seasons, more grasses and shrubs

temperate shrublands and woodlands characteristics

• between 30 degrees and 40 degrees latitude

• evergreen shrubs and trees

• Mediterranean type climates - wet winters and hot, dry summers

• fire is common and helps maintain the biome

• low to very high diversity, warm summers, long dry season, fire important

• Mediterranean shrublands ecologically important

deserts characteristics

• in high pressure zones at 30 degrees N and S

• high temperatures, low moisture

• sparse vegetation and animal populations

• low water availability constrains plant abundance and influences form

• can be hot or cold, or hot sometimes and cold other times

• always have extended dry periods

• low species diversity, low productivity, but amazing adaptations and a wide diversity of life forms

boreal forests (taiga) characteristics

• 50 degrees to 65 degrees N

• long, severe winters

• permafrost (soil that remains frozen year round) prevents drainage and results in saturated soils

• trees are conifers - pines, spruces, larches - and birches

• largest biome by area

• very cold winters and brief summers

• low diversity and low productivity due to climate

• threatened by resource extraction and climate change

• huge global carbon reservoir

tundra characteristics

• above 65 degrees latitude, mostly in the Arctic

• cold temperatures, low precipitation

• short summers with long days

• vegetation: sedges, forbs, grasses, low-growing shrubs, lichens, and mosses

• widespread permafrost

arctic tundra characteristics

• long, cold winter, brief summer, dry

• no trees

• often with permafrost

• low productivity

• low diversity

• highly threatened by climate change

• Kamchatka, eastern Siberia; Alaska

what are freshwater and marine ecosystems often classified based on?

salinity, flow, depth, and light availability

eutrophic lake vs oligotrophic lake

eutrophic - floating algal mats and dense phytoplankton populations

oligotrophic - lower productivity and much clearer water

watersheds

an area of land that channels rainfall, snowmelt, and runoff into a common waterbody such as a stream, river, lake, or ocean

differences between terrestrial and aquatic biomes: productivity

productivity on land - temperature and rainfall

productivity in ocean - availability of light and nutrients (P, N, Fe)

land-water margins

transitions between terrestrial and aquatic biomes create unique ecosystems