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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 - 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 richness
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
3 impacts of fire in tallgrass prairie (ranked)
kills seedlings of most woody plants
impacts nutrient cycling
opens soil surface to sunlight (for months to a year or two)
How do fires kill seedlings of woody plants? (and why not prairie plants?)
if not burned every 5-10 years, most tall / mixed grass prairie will turn into forests / shrublands
woody plant seedlings die because their meristems are located above ground and are killed by fire
prairie plants survive because their meristems are located below ground & the fire moves so fast that temperatures don’t reach fatal levels
How do fires in TGP impact nutrient cycling?
in prairies, nutrients get “locked up” in plant litter (dead plants on soil surface)
fire converts plant litter to ash, returning many nutrients to the soil
Why is it important that fires open up the soil surface to sunlight?
it speeds up warming of soil, impacts soil moisture, and improves seedling survival
how are prairie plants impacted by fires (can be negatively)
prairie plants must use energy to resprout after a burn. If fires occur too frequently. if fires occur too frequently and always at the same time of year, some prairie plants are favored over others.
in TGP region, fires are usually in March and April, hurting those plants that green-up early in Spring & benefitting plants that green-up later in the year.
Can some woody plants resprout after fires?
Yes.
in original prairies, some woody plants were maintained as constantly regrowing trees or shrubs
If fires didn’t occur for several years, trees would explode in height
Ex: Black Oak, Bur Oak, blackberries, wild plum, sumac
Where do savannas form?
form where fire is frequent & rain of seeds from surrounding forest is big
fire killed majority of tree seedlings
but occasionally, seedlings got missed by several consecutive fires & grew big enough to survive future fires
created savannas of TGP w/ bur, white, & black oak and prairies w/ Ponderosa Pine
Is animal mortality high due to fires in prairies? How might an animal get away?
It is not as high as it might seem it would be logically
escape below ground
fly away
walk around the fire
What types of animals face high mortality due to fires?
less mobile animals face higher mortality
spiders
baby birds and mice
larval insects
How can fire planners minimize mortality of sensitive animals?
time fires carefully
only burn ½ or less per year
leave unburned patches unburned - refuges for less mobile animals
List post-fire impacts
post-fire prairie is open habitat for months
some animals prefer open prairies (ex: N. American Deer Mouse)
others prefer dense, unburned prairies (ex: Northern Short-tailed Shrew)
recently burned prairies also attract grazers
How do bison grazing impact recently burned prairies (shifting mosaic)?
after fires, grazers prefer nutritious and easy-to-digest resprouting plants
grazing prevents buildup of thick plant litter
surrounding ungrazed areas have thick growth and fast buildup of plant litter
this makes the ungrazed location easy-to-ignite in the future
How and why are prescribed fires used?
prescribed fires are used frequently in prairies & other ecosystems
they are “easy” to control with proper planning and training
they are used to:
control woody plants
control invasive species (smooth brome, kentucky bluegrass)
create pre-settlement fire conditions
general conservation status of grasslands around the world
all grassland types worldwide are hurting
What is the #1 reason grasslands are hurting worldwide?
Habitat loss
Why has habitat loss impacted prairies so much? (aka why have humans destroyed so much prairie?)
prairies build great soils underneath them (esp Tallgrass and Mixed grass prairies)
they are easy to plow
prairie plants have little apparent economic value
How much has each prairie type decreased by in the US?
Tallgrass Prairie = 96-98% gone across US
Mixed Grass Prairie = 60-80% gone depending on state
Shortgrass Prairie = 25-50% gone
Other causes of grasslands to be hurting (list)
habitat fragmentation
invasive species
climate change
pollution
lack of fire (big one)
improper grazing (too light or too little)
decrease in disturbances (pocket gophers, bison wallowing)
the woody growth form has appeared many times in ______________ (related or unrelated) plant growths
unrelated
define succession
succession = the gradual, predictable change in species living in an area over time following disturbance
What types of ecosystems go through succession and what factors drive it?
all ecosystems go through succession
it is driven by: 1. mobility of seeds, and 2. tolerance of shade
Diagram an example of succession in Riparian Forest
define climax community
climax community = the group of plants & animals associated with them that show up late in succession & persist indefinitely until the next disturbance
define pioneer species
pioneer species = species that show up early in succession nd quickly disappear b/c of shade
give an example of both a climax community plant and pioneer species and if each is K-selected or r-selected
climax community → silver maple, K-selected
pioneer species → smartweed, r-selected
diagram where each type of forest (& prairie / savanna) grows relative to a river / slope
RQ: How does bison grazing INCREASE the biodiversity of prairies?
bison graze more on dominant grasses than forbs and woody plants
they knock back the dominant grass populations and allow forbs to come in
RQ: Why would bison graze the same spots over and over again, and leave the surrounding vegetation ungrazed?
b/c their urine then goes onto the soil and the grasses end up being more productive and nutritious
RQ: Bison dramatically impact nitrogen cycling in the soil. How?
they consume plants that are hard to break down & return the nutrients to labile forms (easy to breakdown)
nitrogen in their urine is mostly urea which is easy to change into ammonium
reduce plant matter above ground and therefore reduce likelihood to lose nitrogen to burn
increase shoot nitrogren content by grazing
all in all, they increase rates of nitrogen cycling
RQ: What is a wallow and how do they impact the prairie landscape?
a wallow = a patch of bare soil created by the bison pawing at & rolling in the dirt.
the soil becomes compacted, which means they collect rainwater in the spring and create a little patch of a different habitat.
they support different vegetation
overall, they increase plant diversity
RQ: How do bison carcasses impact the vegetation?
they release large amounts of fluids with high N content as they decompose
carcasses kill plants below them
initially the mass amount of nutrients released are toxic to the plants but eventually it becomes a highly fertile area (2-3x higher)
more disturbance
RQ: What is masting?
masting = when oak trees drop a large amount of acorns at the same time in the same year
RQ: How do increased acorn crops impact the number of gypsy moth pupae?
increased acorn crop (masting) → increased survival & breeding of mice → increased predation of gypsy moth pupae
(opposite is true for low acorn crop)
RQ: How did the researchers test the impact of mouse populations on the number of gypsy moth pupae?
they removed mice from 3 grids, kept them in 3 grids, then compared the amount of pupae attacked
RQ: What roles do white-tailed deer and white-footed deer mice have on the life cycle of ticks and the bacterium causing Lyme Disease?
Wherever the deer & mice are highest in concentation (affected by masting), the ticks are likely to follow. Ticks get the bacterium from mice and later attach to deer
RQ: How do increased acorn crops impact the risk of getting Lyme Disease?
“Acorns determine larval tick densities by affecting the use of oak forests by deer, resulting in high use of oak forests by deer, resulting in high densities of both host-seeking uninfected ticks and ticks parasitizing mice…” (1025).
acorns increase, lyme disease increase
RQ: What is the relationship between gypsy moths and acorns?
moth defoliation reduces acorn production
RQ: What percentage of human crop plants are pollinated by animal pollinators?
70%
RQ: Why are wild, native beeds going to be increasingly important as pollinators for food plants for humans in the coming ages?
b/c the type of bee (Apis mellifera) that is typically used / managed is difficult to maintain
RQ: Have there been examples of local extinctions of wild bees leading to a decrease in crop pollination?
Yes, in California watermelon fields
RQ: Why are more diverse bee communities valuable for crop pollination? (see section on Indonesian farming)
some rare, highly efficient pollinators contribute disproportionately to their abundance
& a diverse community may be more capable to provide more consistent services across the spectrum of weather conditions and spatial & temporal availability of coffee bloom
(Complementarity among species)
RQ: Why is the abundance of natural habitat important for crops pollinated by bees?
if there is natural habitat nearby, the bees will provide greater function as well as being more stable and predictable
what is mesophication
Oak Decline
describe why mesophication is happening (related to fire)
fires used to sweep from the prairies into the various forests, especially on the tops of hills
these fires killed the seedlings and adults of fire intolerant tree species like ironwood, hackberry, linden…
this kept forests on the upper slopes fairly open and sunlight reached the forest floor
the seedlings of white, bur & black oak, and shagbark & bitternut hickory need lots of sun
w/ control of fire seedlings of fire intolerant species survive & forest canopy fills in. This reduces survival of oak and hickory seedlings
Therefore, fire dependent oaks & hickories decline while fire intolerant species increase (= mesophication)
Note 
Flashcard (30)