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Draw a map of the locations of the Grasslands of the Midwest in 1830
Tallgrass prairie
range
species richness
relationship to fire
density of vegetation
North to Canada and South to Gulf of Mexico
moderate to high species richness
fire dependent
little to no exposed soil (dense vegetation
Shortgrass prairie
range
species richness
density of vegetation
North to Canada, South to Texas
occurs over much of Western US between mountain ranges
moderate to high species richness
lots of exposed soil
Mixed grass prairie
where found
what is it a combination of?
species richness
relationship to fire
in between tall and shortgrass prairie
combination of shortgrass prairie on dry ridges and tallgrass prairie in wetter areas
fire dependent in some areas
Sandhills Mixed grass prairie
what is it made up of?
species richness
relationship to fire
sand dunes covered with prairie
consists of tallgrass and shortgrass prairie plants that can survive on sandy soils
low to moderate species richness
fire dependent
Draw a map of the forest type locations of the Midwest in 1830
Eastern Deciduous Forest
where located
species richness
relationship to fire
where do they grow in the landscape?
eastern half of US
high species richness
there are many subtypes, some of which are fire dependent
in Midwest, they grow on steep hills along rivers
often grow as fire-created savannahs
Riparian Forest
where located
species richness
where do they grow in the landscape?
rapidly expanding West
low to moderate species richness
limited to floodplains along rivers
Ponderosa Pine Forest
where located
species richness
relationship to fire
extensions of the large Ponderosa Pine Forests in the Western US
low species richness, but many of the species aren’t found anywhere else in the Midwest (so they are important)
often grow as fire-created savannahs
Scattered White Pines
where did they come from?
where do they grow?
relics of when White Pine Forests were widespread in the Midwest
grow in cooler sites (steep, North-facing slopes. White Pines and a couple other Northern species survive
2 main factors that determine where ecosystems grow
temperature
precipitation
other factors influencing where ecosystems occur
soil - especially sandy & gravelly soils
fire - can create savannahs and grasslands that replace forests
patterns of temperature around the globe
generally warmer @ equator & colder @ poles
can be influenced by ocean currents
more extreme colds and warms in center of continents, far from large insulating bodies of water (like oceans) (called Continental Climate)
humidity in air also insulates against strong temperature swings
patterns of precipitation around the globe
generally highest at equator & declines towards poles
proximity to warm oceans & winds carrying water from ocean affects it
rainshadows → mountain ranges “block” the flow of moisture, creating dry area downwind of mountains (wet side and dry side (warm air goes towards mountains collecting moisture, air rises and cools, causing rain, other side of mountain is dry)
Grasslands cover roughly ___% of the world’s land area and are found on most continents
30%
Grasslands are usually found in the _____ (center, edge, side.. etc) of continents. Why?
the center
because extreme temperature swings create grasslands rather than shrublands
Grasslands occupy places with _________ levels of precipitation. About ___-____ inches of rain
moderate levels
10-35 inches
How much are grasslands affected by humans?
They are heavily impacted by humans on most continents
When did the first grasses evolve? and where?
60-110 mya in Africa and South America
When did grasslands become widespread in North America? and what was their impact?
30 mya → they are a fairly young / recent ecosystem
these early grasslands supported an incredible community of grassland mammals in Midwest
What is the Pleistocene Epoch and when did it occur?
it began about 2.2 mya
glaciers moved South out of Canada and into the Midwest
climate varied widely over short time spans
What did the climate fluctuations caused by the glacial advances of the Pleistocene Epoch cause? What does this mean for today’s grassland plants?
the climate fluctuations pushed ecosystems back and forth acorss the continent
the combination of the recent origin and constant movement of grasslands caused 3 things:
1. many grassland species of today are fairly tolerant of change
2. tallgrass prairies contain relatively few endemic species
3. b/c of the lack of endemics & tolerance of change, Tallgrass prairie has relatively few endangered species
Define endemic species
a species that is found only in a particular location or ecosystem
Why does tallgrass prairie have few endangered species?
there are few endemic species found in tallgrass prairie
combined with the fact that they are fairly tolerant of change due to climate fluctuations that occured during the Pleistocene Epoch
= few endangered species
What species make up tallgrass prairie if there are few endemic species?
TGP is largely made up of species “borrowed” from other ecosystems
like from forest openings in eastern US
or deserts of southwest US
the current version of TGP has only occured together as an ecosystem for the last 30,000-50,000 years
What happened in the Ice Ages (Pleistocene Epoch)?
beginning 2.2 mya, glaciers grew in Canada and spread south across US at least 7 times = glacial advances
In between the glacial advances were times when glaciers melted and climate became hot and dry = interglacial periods
Map out where the glaciers formed from 20,000 years ago and their max extents
What 3 things caused the growth of glaciers?
periodic shifts in the tilt of the Earth’s axis
periodic shifts in the shape of the Earth’s orbit around the sun
the position of the continents - not preventing tropical water from reaching poles (current position of continents blocks tropical water from reaching the poles)
(for 1&2, glaciers grow when tilt of axis and shape of orbit cause summer to be cooler → because of cool summers, winter snows in Canada don’t melt completely during summer
Tallgrass prairie has ________ species richness
high
Between Nebraska & Iowa, there are _____ species of prairie plants
1200
High species richness in plants leads to high richness in…
soil bacteria
round worms
insects
reptiles
soil fungi
spiders
mammals
richness of insects directly related to richness of plants (positive)
each plant species supports some # of insects that live nowhere else on Earth
define Disturbance
any action that disturbs vegetation in a place
disturbance at small scale
pocket gopher mounds
ant mounds (also eat certain seeds changing plant community)
bison carcass
disturbance at medium scale
storms
fire
bison grazing
disturbance at large scale
drought
fire
on a landscape scale, __________ levels of disturbance create __________ species richness. why?
moderate levels of disturbance create high species richess
disturbance reduces populations of competitively dominant plants
creates germination sites for seeds of less dominant plants
in grasslands, disturbance usually controls populations of dominant grasses that outcompete forbs
brief description of both r & k selected species
r = small, short lived, not competitive
k = large, long lived, highly competitive
r-selected species strategy
produce a huge # of seeds / offspring that are highly mobile (not much energy invested in each seed)
live in disturbed places = “weedy” species
ex: dandelion, Western ragweed
k-selected species strategy
produce few seeds / offspring that are large, less mobile, high energy
live in non-disturbed places
ex: compassplant, big bluestem
human activities usually have a stronger negative impact on ___-selected species
k selected bc r-selected like the disturbed places
on a landscape scale, many habitats are mosaics of places that are at different stages of recovering from disturbance. what does this lead to?
great species richness
how long has fire been a part of grasslands?
long before the arrival of humans, it is an important part of many ecosystems
why do grasslands burn so frequently?
very few firebreaks present and lots of land for lightning to strike
dry grass is a great fuel
Midwest is windy
How are fires in grasslands ignited? and when in the year does it happen?
lightning
march-november
when do most fires happen?
while most t-strorms are in june/july, the prairies are wetter / greener then
early spring and mid-late fall: lightning is less common, but grasses are dry
Overall:
summer fires are fairly frequent but small (except in drought years)
dormant season burns are uncommon but can be huge
Human use of fire
Native Americans used fire frequently, and these likely occasioanlly got out of control
Why did they burn?
to create firebreaks to protect from wildfires
to clear land for agriculture
to attract big grazers
Tallgrass prairies burned every __-__ years on every point of land
3-5 (they are wetter but have more fuel buildup)
Shortgrass prairie burned every __-__ years on every point of land
5-25 (they are more dry, but have less fuel buildup)
most grass fires are ___-moving and relatively ___ intensity
fast-moving, low intensity
The impact of fires depends on several factors
grazing history (reduces fuel available)
wind speed & direction
season
fire history
plant species present
presence of small fire breaks (gopher mounds, deer trails) → creates patchy burns
define both headfire and backfire
headfire = fire moving with wind
backfire = fire moving against wind → slow moving and can heat soil
Note 
Flashcard (21)