Yellowstone's Northern Range - Greater Yellowstone Science ...

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THE NORTHERN RANGE 20 Figure 2.4 Tracking of the Palmer Drought severity Index (a commonly lIsed indicator of fire risk) over the past century in Yellowstone shows a gradual drying trend, which may have a variety of effects on vegetation communities, as discussed in this chapter. Note especially the extreme and historically unprecedented dryness of 1988, when Yellowstone experienced fires on a scale apparently not equalled since about 1700. Courtesy of Grant Meyer, Middlebury College. Yellowstone Palmer Drought Severity Index Time Series -7 - o "Large ll fire years -5 - >-< - U) 5: -3 - - .... III -1 § - i~ - ;::i , U) 1 - - 3 - - ~\ 5 - 1890 1910 1930 I I ,''' MY' ~, 1988.1 (;) tf \ • I I 1950 1970 1990 range in Lamar Valley vary widely; from 39°F (3.9°C) at the Lamar Ranger Station, to 40SF (4.7°C) at Pebble Creek, to 48.1 OF (8.9°C) at the east end of Lamar Canyon (Friedman and Norton 1981). It is a matter of some interest whether or not the changes in climate experienced by Yellowstone during the 1900s are in part the result of human influence on the atmosphere. Romme and Turner (1991) have proposed a series of alternative scenarios that may arise in the greater Yellowstone ecosystem as human-caused global climate change progresses in the future. These scenarios feature significant changes in vegetation communities, with consequences ranging from minor to grave for various mammal species. For example, a slight warming and drying of the park's climate will almost eliminate whitebark pine, an important food species for grizzly bears and other animals. Yet another reason to continue the present investigations of the northern range is the opportunity this research provides to establish baseline information against which to measure such changes. CLIMATE: RESEARCH RECOMMENDATIONS Over the past 20 years much of greater Yellowstone has been subjected to intense scrutiny using palynological methods to reconstruct paleoclimates. Particularly well-studied is the area from central Yellowstone south through the Grand Tetons. Research needs to be expanded to the north and east of Yellowstone, especially to understand more about the very important prehistoric variations in the Great Plains monsoonal pattern, and how it has affected the northern range in the past. A lake on the northern range has been identified as one of the very few "varved lakes" known in North America. Research on this lake could yield patterns in annual weather and vegetation, at the very least, back to the Pleistocene. Daily weather records from many stations in the park are archived in original hard copy at a facility on the east coast. These records need to be accessioned and computerized so that the weather during the historic period can be better understood.
PREIDSTORlC AND EARLY HISTORlC SETTING 21 FIRE AND THE NORTHERN RANGE Yellowstone National Park featnres a variety of substantially different fire regimes (Despain 1990). These differences might most easily be shown in the length of a given plant community's "fIre-return interval," that being "the amount of time between successive fIres on the same site" (Despain 1990). The fIre-return interval is largely determined by the age of the vegetation and the rate at which fuel accumulates, so in a slow-growing forest the fire-return interval is much longer than in a shrub community or a grassland. About 80 percent of the park's forests are lodgepole pine, which on Yellowstone's infertile central plateau have a fire-return interval in excess of 300 years (Romme and Despain 1989b). Barrett (1994) reported a considerably shorter fire-retum interval, with a mean interval of 200 years, for lodgepole pine on more fertile andesitic mountain terrain in northeastern Yellowstone, and a mean interval of more than 350 years for high-elevation whitebark pine forests. Houston (1973) sampled 40 fIre-scarred trees on the northern range "to reconstmct the frequency and size of fIres during the past 300 to 400 years in .northern Yellowstone National Park." Houston, by aging fire scars on trees adjacent to northern range plant communities, was able to measure the frequency of fires in the grasslands adjacent to the trees, because the trees regularly survived such fires and continued to grow. Houston (1973) estimated "mean adjusted intervals of 20- 25 years between fires" on the northern range, and suggested that this fire frequency may have been in part the result of fIrerelated activities by Indians, who are believed to have set fires in other parts of North America for a variety of purposes, including game drives and vegetation management (there is as yet no evidence that Indians regularly set fires in Yellowstone, either in the grasslands or in the park's forests). But fIre was suppressed whenever possible on the northern range after the establishment of Yellowstone National Park in 1872, and fire has been to some extent excluded from exercising its influence on the range since then: The best interpretation may be that much of the area would have burned at least one to four times since the establishment of the park were it not for the actions of modem man. Changes that have occurred in the vegetation seem best explained by a reduction in fIre frequency but have also occurred within a fluctuating climate regime ... and with concomitant foraging by ungulates (Houston 1973). FIRE: RESEARCH RECOMMENDATIONS There have been important advances in sampling techniques and statistical analyses since the publication of Houston's (1973) fIre history study of the northern range. These advances are significant enough to justify a new and more ambitious fire history study on this range, incorporating Houston's (1973) findings. This new study should have a larger sample size, and the collections must be well referenced spatially so that we can better map the approximate extent of individual fires in the past. It is possible to collect fire scar samples from large Douglas-fir trees without killing the tree, and new Figure 2.5. Additional research in fire history should shed Ught 011 the complex interactions of herbivores, climate, and fire in shaping vegetation communities. NPS photo.
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Page 60 and 61: Figure 4.1. Northern range, showing
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Page 66 and 67: THE NORTHERN RANGE 50 public lands,
Page 68 and 69: THE NORTIlERN RANGE 52 Figure 4.5.
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Page 77 and 78: SOIL, EROSION, SEDIMENTS, AND WATER
Page 79 and 80: SOIL, EROSION, SEDIMENTS, AND WATER
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ELK POPULATION ISSUES 71 ... Other
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ELK POPULATION ISSUES 73 1996d), so
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ELK POPULATION ISSUES 75 the northe
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ELK POPULATION ISSUES 77 It has evo
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THE NORTHERN RANGE 82 Competition t
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THE NORTHERN RANGE 88 not aware of
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THE NORTHERN RANGE 90 tion size, an
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THE NORTHERN RANGE 92 activity (95
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THE NORTHERN RANGE 104 practically
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THE NORTHERN RANGE 106 appear suppr
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AppendixA. Conferences, Meetings, a
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lJO Year Estimate Comment Source 19
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lJ2 , Estimated # of Elk Year Date
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lJ4 Winter Total Count 1967-68 397
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116 Year Date of Count Parkwide Par
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118 Counts and estimates of mule de
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120 Northern Yellowstone winter ran
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122 Population estimates and reduct
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124 Actual count Inside Outside Est
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Pronghorn counted during spring sur
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128 Year 1939 1940 1941 1942 1943 1
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Ground and aerial counts of bighorn
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REFERENCE LIST NOTES ON THIS REFERE
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Pages 199-210 in Carbyn, L.N., S.H.
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Yellowstone National Park. Technica
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mammal mortality in the 1988 Yellow
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National Park. International Journa
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Mehus, C.A. 1995. Influences ofbraw
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__ , and __ . 1996a. Preburn root b
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Pages 127-138 in F.J. Singer, ed. E
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some northern Yellowstone elk. M.S.
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