Temperate%20Grasslands

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Temperate Grasslands

• Prairies, (N. Am. Great Plains, Palouse,
  California)
• Steppes (Russia - Ukraine Hungary-Rumania)
• Pampas (Argentina - Uruguay)
• Veldt (S. Africa) NZ tussock grasslands

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Temperate grasslands
prairies, steppes, pampas, veldt..
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Temperate grasslands

• Prairies and steppes have continental climates
  characterised by large annual range of
  temperature, cool - cold winters, with most of
  precipitation as snow, and hot, commonly droughty
  summers because of high evapotranspiration rates.

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North American grasslands
Calgary
Chicago
Cheyenne
Omaha
Abilene
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Palouse prairie
eastern Washington, and Oregon, Idaho
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California grasslands
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Classifying the American prairie
above Carpenter, 1940. below Clements and
Weaver, 1939.
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Mean annual temperature and precipitation in US
prairies
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Temperature regimes(Great Plains stations)
Temperature (C)
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Precipitation regimes(west- east transect)
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The prairie-forest boundary

• Budyko suggested that the forest - grassland
  boundary in the midwest corresponds with a
  dryness ratio of 1.1 -1.2 (dotted line)

Budyko dryness ratio values, N. America
Hare (1980) Atmos.-Ocean 18, 127-153.
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Pacific air mass dominance period (months of the
year)
9 months
lt1 month
12 months
lt1 month
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Soils

• Loessic parent material - derived from aeolian
  reworking of glacial and fluvioglacial deposits
  in northern North America and Europe during late
  glacial periods.
• Limited areas of glacial, fluvioglacial, and
  alluvial deposits

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Soil genesis

• In humid areas on forest margins BRUNIZEMS are
  the dominant soil type. Characterized by
  moderately acid A horizon (pH 5-6).
• In tall-grass prairies CHERNOZEMS (MOLLISOLS)
  are dominant. A horizon has pH of about 6-7.
  Dominant processes are melanization and
  calcification. Rodent (esp. gopher) and insect
  activity may recycle gt100 ton/ha/of soil per year
  to surface.

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Chernozem/Mollisol profiles
mixed-grass short grass
Melanization
Calcification
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Soil mosaic in humid prairies (humic gleys in
hollows soil erosion on ridges)
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Soil catena in dry prairies
1. Chernozem
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depression
2
3
Na, Mg, etc
2. Solonetz 3. Solod
textural B Na saturation of B and C horizons
Solonetzic solod profile
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Chernozem-solonetz mosaic in grazed steppe,
Rumania
S
C
S
S
S
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Some common grass species
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2
3
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1. Andropogon gerardii (big bluestem) 2.
Bouteloua curtipendula (sideoats grama) 3.
Schizachyrium scoparius (little bluestem) 4.
Koeleria macrantha (?) 5. Bouteloua gracilis
(blue grama)
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Grass-climate relations(highly schematic)
E. Illinois
W.Wyoming
2m tall
1m tall
0.5m tall
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Topography and plant cover mixed grass prairies
(ungrazed)
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Grass phenology
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Cardinal temperatures for net photosynthesis, C4
and C3 plants
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C4 grassesa) less tolerant of low temperatures
(e.g. flowering inhibited by night T lt13C) b)
more tolerant of moisture deficits
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C4grasses in regional grass flora
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20
30
40
50
60
80
70
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Polar and tropical source areas for prairie
grassesNote no pre-Miocene grass fossils known
from plains area. Conclusion Prairies
developed in lee of rising Cordillera in
mid-Tertiary.
C3 Agropyron, Elymus Koeleria, Poa, Stipa
sedges
Bouteloua, Buchloe Andropogon C4
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Prairie forbs

• Streletsk reports 180 spp of flowering plants
  from the Ukrainian steppes (only 20 of which are
  grasses).
• In the tall-grass prairies of North America gt70
  spp may be in flower at once.
• Forbs have variable drought tolerances and
  phenologies.
• Flowering times range from March (e.g.
  Tulipa/Hyacintha in steppes) - Sept/Oct (e.g.
  Delphinium spp.).

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Some N. American prairie forbs
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1
2
1. Amorpha canescens 2. Asclepias tuberosa 3.
Helenium autumnale 4. Verbena stricta 5. Aster
laevis
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5
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Annual productionof plant biomass in prairie
grasslandsnote 60-80 below-ground
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Biomass(ungrazed prairie)
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Grazers
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Consumptionrelatively small intake by shoot
grazers vs. root suckers(predominantly
nematodes)BUT is this a product of historical
factors?
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Rapid decline in grazer populations in last 200
years as a result of habitat destruction and
hunting.
Buffalo - almost extinct Gophers - 98 decline
1900
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Buffalo grazing Manitoba
In vallies and humid situations, the grass grows
to a great height, which fattens our horses in a
short time, but the buffalo usually makes choice
of the hilly, dry ground to feed on, the blades
of grass on which are small, short and tender.
When a numerous herd of these animals stay any
length of time in one place, the ground is
absolutely barren there for the remainder of the
season Umfreville (1790)
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Buffalo grazing North Dakota
This afternoon I rode a few miles up Park river.
The few spots of wood along it have been ravaged
by buffaloes none but the large trees are
standing . . . The small wood and brush are
entirely destroyed, and even the grass is not
permitted to grow. The bare ground is more
trampled by these cattle than the gate of a
farmyard . . . Alexander Henry (1801)
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(No Transcript)
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Was there a grazing sequence?
Antelope reported to follow buffalo they appear
to prefer heavily-grazed land with dense
populations of forbs.
Antilocapra americana
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Colonization of old coyote burrows by gophers -
effects of dogtown on neighbouring vegetation
10 m
pre-
post-
Eastern Colorado prairies burrow entrances shown
by arrows
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Effects of dogtown age on local plant cover
grassland replaced by herbaceous shubland
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Carnivores
(all hole nesters)
Burrowing owl Kit fox
Badger
swift fox, coyote, wolf, bears
Photo credits Greg Lasley, Bill Standley
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Pre-Pleistocene fauna

• Selection of prairie flora for tolerance of heavy
  grazing a product of radiation of diverse
  herbivore assemblage in Mio-Pliocene.
• In the Pliocene the N. American plains were home
  to 7 genera of horses, 12 genera of antelopes
  camelids, peccaries, tapirs and rhinoceroses
  (plus a diverse group of carnivores)
• Think of a Nebraskan Serengeti.

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Pliocene plains fauna
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Fire on the prairies
Are the tall-grass prairies a climatic climax, or
is fire the predominant generative and
maintaining factor?
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The argument in favour of fire
I grew up in the timbered upland peninsula
formed by the junction of the Missouri and
Mississippi Rivers. The prairie began a few
miles to the north and extended far into Iowa.
The broad rolling uplands were prairie, whatever
their age and origin, the stream-cut slopes were
timbered.. From grandparents I heard of the
early days when people dared not build their
houses beyond the shelter of the wooded slopes,
until the plough stopped the autumnal prairie
fires. In later field work in Illinois, in the
Ozarks, in Kentucky, I met parallel conditions of
vegetation limits coincident with breaks in
relief. I gave up the search for climatic
explanation of the humid prairies. Carl Sauer,
1969. Agricultural Origins and Dispersals.
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A prairie landscape in Illinois,showing the
restriction of woodland to moister (and more
fire-proof) valley bottoms
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Prairie fires Texas
the Indians of the interior have another
intolerable method, . . . which is to fire the
plains and forests . . . both to drive the
mosquitoes away and at the same time drive
lizards and like things from the earth to eat.
They also kill deer by encircling fires deprived
of pasturage, the animals are forced to seek it
where the Indians may trap them. Cabeza de
Vaca, A.N. Relación (1542) Shipwrecked by a
hurricane on the coast of Texas with his crew in
1527 Cabeza de Vaca lived with the Indians in
Texas from 1528-1535.
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Prairie fires the Dakotas
the Plains are on fire in view of the fort on
both sides of the river, it is said to be common
for the Indians to burn the Plains near their
Villages every Spring for the benefit of their
horses and to induce the Buffalow to come near
them. Lewis and Clarks Journals - describing
their winter quarters in North Dakota in 1805.
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Prairie fires Oklahoma
Oct 31, 1832 It was the time when hunting
parties of Indians set fire to the prairies the
herbage . . . was in that parched state,
favorable to combustion . . . Irving, W.A. A
Tour on the Prairies (1835)
Oct. 24, 1849 yesterday we could see the
smoke of the Prairie burning in every direction
but today it got close to us. It was the work of
the Osages Woodhouse, S.W. Journals (1992)
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Fire and prairie restoration
Fire season Fire season
Spring Late-summer
Flame height (L, m) 1.90.4 0.70.1
Intensity (I kW/m)1 1260520 12020
Litter consumption () 100 912
II 259.83L2.174
Data Copeland et al., 2002. Restoration
Ecology, 10,31-323
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Fire and prairie restoration
Data Copeland et al., 2002. Restoration
Ecology, 10, 31-323
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Fire and prairie restoration
Data Copeland et al., 2002. Restoration
Ecology, 10, 31-323
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Prairies in the late Quaternary
PollenViewer
Where were the prairies at LGM? Most LGM pollen
assemblages in southern Great Plains have no
modern analogues, but Neb/Kansas open
subalpine forest/parkland? C.Texas sagebrush
steppe? northern Mexico-NM juniper/pinyon
woodland?
see Poaceae and prairie forbs
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Climatic change produces a shifting prairie -
forest ecotone(cf. Hypsithermal)
500 km
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Recent (and future?) climate change in the
prairies (Moon Lake, ND)
AD
Droughts
Wets