lecture 18- grasslands, bringing nature home

% global distribution of grasslands

28% of terrestrial biosphere

types of grasslands

temperate, tropical, tundra

temperate grasslands

praries (US), steppes (europe), pampas (south america), veldt (south africa)

tropical grasslands

areas with seasonal rain & drought

tundra

around arctic circle above latitudes where trees survive

natural factors that maintain landscapes as grasslands

grazing, fires

unnatural factor that maintains landscapes as grasslands

mowing

how long have grasslands been around

since 70MYA

early grassland definition

wet, temperate biome occupied polar regions

first grasslands lived in forests of

conifers, ginkgos, dicot angiosperms, ferns

morphology of earliest grasses suggest ____ origins

forest

secondary grasslands

10,000-6800 years ago

spread of - deforestation, pastoralism, arabile farming

domesticaiton of _____ led to secondary grasslands

maize (central america), rice (asia), wheat (middle east)

semi natural (secondary) grasslands

formed by human low-intensity land use due to tree cutting, haymaking, low-intensity traditional farming

hypsodont

high-crowned teeth in horses and enamel extending past the gum line. teeth persist longer under diet of tough abrasive material

co-evolution of grasslands and horses

brachydont → hypsodont transition in horse teeth is associated with the browser → grazer transition

what caused change in horse diet

aridification (climate drying and cooling), emergence of ecosystems dominated by grasslands

silica cells role in grasslands

make grasses tough, grass phytoliths with distinctive shapes that can fossilize well and be used to trace the emergence and spread of grasslands

grasses now comprise of about _____ species

12,000

economic importance of grasses

food, beverages, construciton materials

wheat, maize, rice, barley, oats

majority of corn crop feeds animals or is used for biofules

wheat, maize, rice are ____% of our calories (+ protein & micronutrients)

50%

ecologic importance of grasses

high biodiversity in grasslands, generator of worlds richest soils, especially by temperate praries

how are graslands able to harbor so many other species

different resource niches, habitat heterogeneity, top-down effects, natural selection for complementarity

why are grasslands important

biodiversity, human well being, ecosystem services,

grassland biodiversity supports

high animal diversity

major threat to grasslands

woody encroachment

what percent of north america’s tall grass prairie lands have been converted to other uses (agriculture, urbinization)

98%

why are our croplands bad

they are monocultures of simply corn, wheat, or sugarcane and do not support high biodiversity of plants or animals

flowers and ____ evolved together

insects

most insect herbivores can only eat plants that

they share an evolutionary history with

insectivorus birds

birds that eat insects as major part of their diet

how many tons of prey do insectivorus birds consume and how many birds are insectivorus

400 to 500 million tons of prey and 6,000 out of 10,000 species

• they consume similar to what the human population do of food

• they use as much energy as New York City

what percent of terrestrial birds in north america rely on insects to feed their young

96%

what is the ratio between species loss and habitat loss

1:1

species richness depends on

size of area

extinction debt

number of species that are destined to go extinct after habitat loss, even though they have not dissapeared yet.

short lived and long lived species in extinction debt

blue, long-lived species - survive longer after habitat loss. extinction debt is paid slowly, so species richness gradually declines over a long period

orange, short-lived species- dissapperar quickly after habitat loss. species richness drops faster to new lower equilibrium