unit 3.3

desert

typically 250 mm of rainfall of less per year, not uniform in distribution

low vegetation and low productivity

temp changes from day→night & summer→winter

deserts recovering from disturbances

takes a long time due to ….

• lack of water which means low vegetation

• low species diversity

• slow nutrient cycling

tropical deserts

sahara and namib deserts of africa

hot & dry most of year= forms crust

few plants

tropical desert dust storms

increased 10X in Sahara since 1950 due to drought and human influences (driving on crust) 

• breaks up surface allowing wind to pick up dust

temperate deserts

mojave desert in southern california

daytime temp are high in summer and cold at night

more precipitation (winter months)= more vegetation

drought resistant shrubs and water conserving cacti and succulents (more biomass=bigger food web)

cold deserts

gobi desert of mongolia

summer: warm

winter: cold

sparse rainfall BUT year-round= supports plant life

sparse vegetation

grasslands

occur in interior of continents

generally too wet for desert but too dry for forest but too dry for forest

seasonal drought,

fires & grazing by herds of mammals prevents trees and shrubs from dominating

• all have low avg precipitation and various average temperatures

tropical grasslands

dry grasslands of tropical areas

seasonal rain with a low average rainfall (600-1200 mm)

constant temperature year-round with distinct wet and dry seasons

seasonal droughts with fire playing a large role with many fire-adapted and drought adapted plants

open landscape with few widely spaced clusters of trees

animals in tropical grasslands

home to large herds of migratory grazing mammals and their predators

grazers (grasses and herbs) browsers (leaf and twigs)

resource partitioning by animals reduces competition

migrations typically due to food and water availability.

temperate grasslands

prairies of mid america, pampas of south america, steppes of asia

summers: warm/hot/ dry

winters: cold

precipitation is uneven through the year

2 types of temperate grasslands

tall grass prairies get about 880 mm of annual rainfall

short grass prairies get about 250 mm of annual rainfall

mixing of the two types occurs with rainfall somewhere in between

soil of temperate grasslands

deep fertile soil= good for agriculture

grass dies & adds organic material while roots live & hold soil together

high winds of temperate grasslands

continuous winds=rapid evaporation so cause periodic fires during season drought but doesn’t kill grass’ root

high wind and fire hinders tree growth except around streams & rivers

humans impact on temperate grasslands

humans have destroyed many temperate grasslands for agriculture and grazing cattle

2nd most disturbed biome

killed many grazing animals

tundra or cold grasslands

most of alaska and north russia

between the Taiga (boreal forest) and the permanent ice of the northern hemisphere

1/5 of the Earth's land surface

annual precipitation is <250 mm with most water held in ice

winters are cold with high winds

winters with little sunlight, summers with almost constant sunlight

soil is nutrient poor and takes a long time to recover from disturbances

permafrost

frozen soil during most of the year except brief summers

due to permafrost, high winds, and cold winters it contains only short stunted plant life

mosses, lichens, small grasses underneath the winter layer of snow and ice.

what permafrost creates

lots of bogs, ponds, and shallow lakes→ permafrost does not allow melted ice and snow to penetrate the soaking into the ground

tundra or cold grasslands animals

home too many animals (mostly migratory birds feeding of the insects from shallow water pools)

mammals survive because of thick coats & specialized behaviors

global warming

causes permafrost to melt in some areas disrupting these ecosystems

causes CH4 (methane) and CO2 to release which causes more warming which melts permafrost

causes soil to sink or subside

alpine tundra 

high elevations of mountains above the tree line but below the permanent snow line whatever the location/latitude

• similar vegetation type but alpine tundra typically receive more sunlight

5 main temperate shrubland or chaparral

all along shores or west coast of continents, typically near deserts

• southern california

• central chile

• southwestern africa

• southwestern australia

• mediterranean shores

temperate shrubland or chaparral

moderate temperatures

close proximity of oceans accounts for more rainfall

ocean fog reduces evaporation

spiny evergreen shrubs and scattered leathery-leafed trees

nutrient poor soil

fires in temperate shrubland or chaparral 

common during droughts

plant species are depended on fire to germinate

re-sprout from roots left in tact after fire

we live in the areas when we shouldn’t because mild, wet winters and dry, warm summers

forests

trees!

wide range of annual rainfall and temperatures determine the three major types

Tropical Rainforest

Tropical Dry Forest

Cloud Forest

Temperate Deciduous Forest

Temperate Coniferous Forest

Temperate Rainforest

Taiga, or Boreal Forest

tropical rainforest

amazon, congo, southeast asia

equator→10 degrees N & S

2500-4500 mm in rainfall

uniformly warm temperature 27 C (80 F)

pollination is primarily by insect, bird, or bat

tropical forest trees

broadleaf and evergreen, distinct layers

forest floor bare due to little light reaching floor

drop leaves all year round

forest layers

shows vertical stratification because of light being the limiting factor

• emergent layer

• canopy

• understory

• ground level

emergent layer

tallest trees

canopy

top of forest and receives lots of sunlight

• the emergent layer and canopy are where most bugs, birds and bats are located

• lower level more shaded

understory

mostly shaded

ground level

usually has very little plant growth

tropical rainforest biome features

containing over ½ of terrestrial species

2/3 of plants in rainforest are trees

highest biome in primary productivity

nutrient poor soil in tropical rainforest

decomposers break things down immediately due to humidity

plants take up nutrients immediately

what isn’t taken up is washed away by rainfall into rivers or streams

lianas

vines rooted in soil but climb tress

• philodendrons

epiphytes

grow solely on trees ex. orchids & bromeliads

tropical forest destruction

being logged (slash and burn) for space, timber, mining, and farms

• soil poor to begin with→deteriorates rapidly and new law must be cut for new farms

• leads to erosion and mudslide→ farmers cannot re-fertilize land due to poverty

tropical rainforest are disappearing 

humans damaged half of these forests by

slash and burn deforestation

agricultural and grazing use

human settlements.

current rate it is predicted that the rainforest will be severely damaged or possibly gone in your lifetime!

3 consequences of disrupting ecosystems

1- reduce earth's biodiversity by destroying the habitat many species live in

2- accelerate climate change/global warming by eliminating forests / trees and their ability to uptake CO2

3- change local regional weather which may prevent the rainforests from being able to replace themselves.

• this will result in the much less biodiverse tropical grasslands.

tropical dry forest

india

located in equatorial regions

two distinct seasons, wet season and dry season

trees drop their leaves during dry season, (deciduous) → soil is more nutrient rich than rainforests because of this

• stays there because dry soil keeps nutrients in it, and drops all at once

recover from disturbances better

temperate deciduous forest

moderate average temperatures with warm summers and cold winters

plentiful rainfall spread throughout the year, 800-1400 mm

mid-latitude regions→ temperate climate zones

forests dominated by deciduous trees (drop their leaves in the fall) = soils rich in humus, organic material from decaying leaves

temperate deciduous forest disturbances

this biome has been disturbed more than any other by humans

by secondary succession it can rebound in 100 to 200 years, we have increased in forests

where people lived, and cut wood, to become developed countries= most forest small and isolated rarely larger than 50 acres

animals in temperate deciduous forest

rarely top predators→habitat fragmentation and overhunting 

they need big areas which we don’t have

• single mountain lion needs ~300 square miles/75,000 hectares

• gray fox, red wolf, bobcat and black bear are other top predators

where forest meet farmland

isolated forests also create more forest edges where forest meets grassland/farms

increases numbers generalist (deer, woodchucks, birds, etc)

decreases specialist (fox squirrels, etc)

T.D.F.'s tend to recover from disturbances better than drier biomes.

temperate evergreen forest

pine forest

mild climates with less rainfall than deciduous forests

if dry enough may give way to chaparrals

dominated by coniferous trees; (cone bearing trees)

• soil tends to be acidic due to breakdown of pine needles

taiga/ boreal forests/ evergreen coniferous forests

cold, wet climates that promote the growth of coniferous forests

• great ring of northern coniferous forests in eurasia and north america

• some occur at high altitude in mountain ranges (not latitude but elevation)

bitter cold winters with summers just long enough to let the ground thaw.

trees in taiga/ boreal forests/ evergreen coniferous forests

needle leaf evergreen trees predominate

trees only 5-10 meters tall, mainly spruce, cedar, fir, hemlock and pine

needles are slow to break down and contribute to the high soil acidity

animals in taiga/ boreal forests/ evergreen coniferous forests

homes too many large mammals (bears, wolves, lots of moose)

no reptiles except garter snakes

one of the largest biomes on earth

not many humans (due to cold) but it is being extensively logged (same amount as rainforest)

coastal coniferous forests/ temperate rain forests

found in areas of high rainfall or moisture from ocean fog (rain like tropical rainforest, near oceans)

huge conifers

• douglas firs & redwoods of northern california, oregon, washington and canada

mountains

show dramatic changes in altitude which affects temperature and other climate factors, soil and vegetation, and oxygen content

mountains (which contain other biomes) and account for 1/4 of land

little oxygen, cold temperature, and wind play roles in defining habitat

difference in rainfall amount on different sides of mountain

humans in mountains

1.2 billion people live in or on edge of mountain ranges

4.0 billion people depend on mountain systems for some or all of their water

snow and ice melts in the summer→releases water into streams & rivers used by humans for irrigation & consumption

erosion in mountains 

steep slopes allows for soil erosion when vegetation is cleared (think mudslides) 

“islands of biodiversity”

mountains act as "islands of biodiversity" with many endemic species- no where else in world= no backup populations

different levels of mountains have different characteristic and specialist cannot survive by leaving area of mountain range, cannot just move around because other layers don’t have necessary supplies

mountains climate

regulate earth's climate as snow and ice reflect solar radiation

feedback loop of warming→ melting→ less reflection→more warming

how we’ve effected terrestrial ecosystems

2005 Millenium Ecosystem Assessment 62% of world’s terrestrial ecosystems are used unsustainably or already degraded

• as population increases

• how much is too much

• how can we protect natural resources

• how can we fix natural resources already degraded or destroyed