1. Temperate Grasslands
Prairies, (N. Am. [Great Plains, Palouse, California])
Steppes (Russia - Ukraine [Hungary-Rumania])
Pampas (Argentina - Uruguay)
Veldt (S. Africa); NZ tussock grasslands

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

3. 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.

4. North American grasslands
Calgary
Chicago
Cheyenne
Omaha
Abilene
Note isolated areas, and peninsula extending eastwards from Omaha

5. Palouse prairie
eastern Washington, and Oregon, Idaho

6. California grasslands

7. Classifying the American prairie
above: Carpenter, 1940.
below: Clements and Weaver, 1939.

8. Mean annual temperature and precipitation in US prairies

9. Temperature regimes (Great Plains stations)
Temperature (°C)

10. Precipitation regimes (west- east transect)

11. The prairie-forest boundary
Budyko suggested that the forest - grassland boundary in the midwest corresponds with a dryness ratio* of (=dotted line)
Budyko dryness ratio values, N. America
Hare (1980) Atmos.-Ocean 18,

12. Pacific air mass dominance period (months of the year)

13. 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

14. 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 Dominant processes are melanization and calcification. Rodent (esp. gopher) and insect activity may recycle >100 ton/ha/of soil per year to surface.

15. Chernozem/Mollisol profiles
mixed-grass short grass
Melanization
Calcification

16. Soil mosaic in humid prairies (humic gleys in hollows; soil erosion on ridges)

17. Soil catena in dry prairies
1. Chernozem 1
depression 2 3
Na, Mg, etc
2. Solonetz
3. Solod
textural B;
Na+ saturation of
B and C horizons
Solonetzic solod profile

18. Chernozem-solonetz mosaic in grazed steppe, Rumania

19. Some common grass species1 2 3 4
1. Andropogon gerardii (big bluestem)
2. Bouteloua curtipendula (sideoats grama)
3. Schizachyrium scoparius (little bluestem)
4. Koeleria macrantha (?)
5. Bouteloua gracilis (blue grama) 5

20. Grass-climate relations (highly schematic)
W.Wyoming
E. Illinois
~2m tall
~1m tall
~0.5m tall

21. Topography and plant cover: mixed grass prairies (ungrazed)

22. Grass phenology

23. Cardinal temperatures for net photosynthesis, C4 and C3 plants

24. C4 grasses: a) less tolerant of low temperatures (e. g
C4 grasses: a) less tolerant of low temperatures (e.g. flowering inhibited by night T <13°C) b) more tolerant of moisture deficits

25. % C4 grasses in regional grass flora10 20 30 40 50 60 80 70

26. C3
Agropyron, Elymus
Koeleria, Poa, Stipa
+ sedges
Polar and tropical source areas for prairie grasses Note: no pre-Miocene grass fossils known from plains area. Conclusion: Prairies developed in lee of rising Cordillera in mid-Tertiary.
Bouteloua, Buchloe
Andropogon C4

27. 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 >70 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.).

28. Some N. American prairie forbs3 1 2
1. Amorpha canescens
2. Asclepias tuberosa
3. Helenium autumnale
4. Verbena stricta
5. Aster laevis 4 5

29. Annual production of plant biomass in prairie grasslands note: 60-80% below-ground
1000 kcal m-2 a-1

30. Biomass (ungrazed prairie)

31. Grazers
“The single greatest impediment to the settlement of the country” US Congress [1976] of the Rocky Mtn locust

32. Consumption: relatively small intake by shoot grazers vs
Consumption: relatively small intake by shoot grazers vs. root suckers (predominantly nematodes) BUT is this a product of historical factors?
1000 kcal m-2 a-1

33. Rapid decline in grazer populations in last 200 years as a result of habitat destruction and hunting.
1600: Buffalo Pop 30-60M (estimated)
1850: Pop <<20M
: 10M hides shipped east
Buffalo - almost extinct;
Gophers - 98% decline
1900

34. 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)

35. 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)

37. Was there a grazing sequence?
Antelope reported to follow buffalo; they appear to prefer heavily-grazed land with dense populations of forbs.
Antilocapra americana

38. Colonization of old coyote burrows by gophers - effects of “dogtown” on neighbouring vegetation
pre-
post-
~10 m
Eastern Colorado prairies: burrow entrances shown by arrows

39. Effects of dogtown age on local plant cover: grassland replaced by herbaceous shubland

40. Carnivores (all hole ‘nesters’) Burrowing owl Kit fox Badger
Owls bait the entrances to their burrows with dung pellets; attracts dung beetles, which they prey on. Fertilizes soil, increases grass growth.
Burrowing owl Kit fox Badger
+ swift fox, coyote, wolf, bears
Photo credits: Greg Lasley, Bill Standley

41. 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’.

42. Pliocene plains fauna

43. Fire on the prairies
Are the tall-grass prairies a climatic climax, or is fire the predominant generative and maintaining factor?

44. 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, Agricultural Origins and Dispersals.

45. A prairie landscape in Illinois, showing the restriction of woodland to moister (and more fire-proof) valley bottoms

46. 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

47. 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 Clark’s Journals - describing their winter quarters in North Dakota in 1805.

48. 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)

49. Fire and prairie restoration
Fire season
Spring
Late-summer
Flame height (L, m)
1.9±0.4
0.7±0.1
Intensity (I; kW/m)1
1260±520
120±20
Litter consumption (%)
100
91±2
II= L2.174
Data: Copeland et al., Restoration Ecology, 10,31-323

50. Fire and prairie restoration
Data: Copeland et al., Restoration Ecology, 10,

51. Fire and prairie restoration
Data: Copeland et al., Restoration Ecology, 10,

52. 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”

53. Climatic change produces a shifting prairie - forest ecotone (cf
Climatic change produces a shifting prairie - forest ecotone (cf. Hypsithermal)
500 km

54. Recent (and future?) climate change in the prairies (Moon Lake, ND)AD
Droughts
Wets