For my complete profile please visit: https://www.researchgate.net/profile/Peter_Wigand to see my profile Download any of my 104 research contributions at: https://www.researchgate.net/profile/Peter_Wigand/research Phone: 775 622 5805 Address: 2210 Seneca Dr
Reno, NV
89506
Integration of pollen records, and fossil woodrat midden data recovered from multiple strata of f... more Integration of pollen records, and fossil woodrat midden data recovered from multiple strata of fossil woodrat (Neotoma spp.) dens (middens) in both northern and southern Nevada reveal a detailed paleoclimatic proxy record for the Great Basin during the last 45,000 years in growing detail. Clear, late Holocene climate-linked elevational depressions of plant species` distributions have occurred throughout the Great Basin of up to 200 m below today`s and by as much as 1000 m below what they were during the middle Holocene. Horizontal plant range extentions during the Holocene reflecting the final northern most adjustments to Holocene climates range up to several hundred kilometers in the Great Basin. Well documented lags evidenced in the late Holocene response of vegetation communities to increased precipitation indicate reduced effectiveness in the ability of plant communities to assimilate excess precipitation. This resulted in significant runoff that was available for recharge. These responses, although indicating both rapid and dramatic fluctuations of climate for the Holocene, fall far short of the scale of such changes during the late Pleistocene. Extension of these results to Pleistocene woodrat den and pollen data evidence spans lasting several hundred to a thousand or more years during which significantly greater amountsmore » of precipitation would have been available for runnoff or recharge.« less
Semi-arid woodlands have dominated the middle elevations of Great Basin mountain ranges during th... more Semi-arid woodlands have dominated the middle elevations of Great Basin mountain ranges during the Holocene where subalpine woodlands prevailed during the Pleistocene. Ancient woodrat middens, and in a few cases pollen records indicate in the late Pleistocene and early Holocene woodland history lowered elevation of subalpine woodland species. After a middle Holocene retrenchment at elevations in excess of 500 meters above today, Juniper-dominated semi-arid woodland reached its late Holocene maximum areal extent during the Neoglacial (2 to 4 ka). These records, along with others indicate contracting semi-arid woodland after the Neoglacial about 1.9 ka. Desert shrub community expansion coupled with increased precariousness of wetland areas in the southern Great Basin between 1.9 and 1.5 ka coincide with shrinking wet-lands in the west-central and northern Great Basin. Coincident greater grass abundance in northern Great Basin sagebrush steppe, reaching its maximum between 1.5 and 1.2 ka, corresponds to dramatic increases in bison remains in the archaeological sites of the northern Intermontane West. Pollen and woodrat midden records indicate that this drought ended about 1.5 ka. Succeeding ameliorating conditions resulted in the sudden northward and downward expansion of pinon into areas that had been dominated by juniper during the Neoglacial. Maximum areal extent more » of pinon dominated semi-arid woodland in west-central Nevada was centered at 1.2 ka. This followed by 100 years the shift in dominance from juniper to pinon in southern Nevada semi-arid woodlands. Great Basin woodlands suffered from renewed severe droughts between .5 to .6 ka. Effectively wetter conditions during the {open_quotes}Little Ice Age{close_quotes} resulted in re-expansion of semi-arid woodland. Activities related to European settlement in the Great Basin have modified prehistoric factors or imposed new ones that are affecting woodland response to climate. « less
High resolution pa lcobol ;mtcal record .... provide sutncienl detail to correlate events regiona... more High resolution pa lcobol ;mtcal record .... provide sutncienl detail to correlate events regionally. Om.'e correlated events can he examined In tandem to determine the underlying Inputs that fashioned them. Several localities in the Great Oasin have p..1.1eobotanical records of sufficient detail to generate TC'glonal reconstructions of vl"g<'tation ~'hanges for the last 2 ka and provide conclusions as to the climates that caused them. [n southern Nevada. analysis of 266 pollen samples from the upper two-thirds of a IS-meler -Iong, lO-cm-(\\lameter set of overlapping cores retrieved from Lower Pahranagat Lake (elevation 975 meter.-;). Llnc:oln County. Nevada. Is providing a detailetl record o(vegetation change at an Interval of every 14 years over the last 3.8 ka. Samples. averaging a bout 3.8 years of pollen deposition with about 10.4 year gaps between each. outline a record of dry and wet periods with rapid onsets and terminations. Periodic Increases in the values of sagebrush (Artemisia) pollen . sometimes coincident with increases in juniper pollen renect intervals of cooler and/or wetter ('limate. Occasional. sometlmcs sevcre. drought Is marked by incrcased bur sage (Ambrosia· typc) and saltbush (Chenopodilneae) pollen and decreased regional conifer pollen. Drier climates between 3.0 and 2.5 ka. 2.4 and 2.0 ka are eclipsed In magnitude by the severe droughts of the last 1.9 ka. In particular. the d.-oughts between 1.9 and 1.6 ka and at 0.9 and 0.3 ka have little paralld dUring the late Holocem' {last 4.0 ka} in southern Nevada. The ratio of a!luatic to littoral pollen types indica les generally deeper water l.'Ondltions aoout 1.6 to 1.3 ka (also C'haracteristic of most of the early part of the record from 3.7 to 2.0 ka) and more variable. but predumlnantly more marshy. conditions during most of the last 1.3 ka. OngOing geomorphic investiga tions in the Low(:r Pahnlnaf!;at Lake ,-\\Tea s ug~est that the sudden shift from lake to marsh conditions around 1.2 to 1.4 ka Jllny be linked to the impact of extreme rainfall events. These may have eroded a s pillway thmugh the alluvial fans that Impounded the lake dUling the early portion of the Lale Holocene (3.7- 1.4 ka l. thereby redUCing the eff('etJve lake level after 1.4 ka. Increasing Pinus (pine) pollen vnlues with r('specl to Junipen.lS ijunipcr) pollen values indicate that pinon pine is now more abundant in the southern Creal Basin than at a ny time since the beginning of the -NeoglaCial". about 4.0 ka. This is due not only to a shift from harsher winters about 2.0 ka (in pa ri evidenced by the decline ()f .Juniper dominan('c in the woodland), but also to period s of summer -s hlftcd rainfall (jnc rea~ed summer rainfall often with decreased winter rainfall). which favored seedling survival rluring the summer. In southern Nevnda. evidence of summer·shifted precipita tion during the first millennium of the Christian Era is seen In the expansion of grasses (reflected In Poaceae pollenl prererling expansions of pinon pine w1thout coincident expansions of winter preclpitation·lov1ng speCies such as sagebrush and j Ullipcr. To the north. pollen and woodral middcn records from the Carson Sink of the central Great Basin (Lead Lake. Nevada) evidence summer· shifted rainfall in contemporaneous expansion of pinon pine into semi·arld woodlands. Pollen records from the northern Great Basin (in particular. the hlgh· resolution pollen record from Diamond Pond . sout.h -central Oregon) Indicate grass expansion at the expense of juniper at the same time. providing further evidence of a major period of summer-shifted preci pitation that characterized much of the Intermountain West.
The microfossil record from the Playa Vista cores clearly reflects both local and regional patter... more The microfossil record from the Playa Vista cores clearly reflects both local and regional patterns of environmental change. Some of these changes may have been the result of regional or local climatic change or both, but others may reflect changes in geomorphic processes as the result of climatic, tectonic, or oceanic (e.g., tidal, current, or wave action) influences. Some of these influences, as well as their impact on Native Americans, may be revealed through a more detailed local and regional comparison of both terrestrial and estuary environments over time, as reflected in the micro- and macrofossil records. Three factors must be examined in greater detail in order to compare these records: (1) our knowledge of the vegetation structure of prehistoric wetlands in southern California ( ie., whether there are adequate modern analogues with which we can compare our reconstructions); (2) how this vegetation structure is reflected in the pollen record; and (3) what impact the directi...
Pollen, spore, and algae records from a variety of depositional contexts provide 12 kyr of paleoc... more Pollen, spore, and algae records from a variety of depositional contexts provide 12 kyr of paleoclimatic proxy data for southwestern North America. Macrofossils and pollen from ancient woodrat nests in the drier interior provide species-level identifications, and exact spatial and chronometric information. Occasionally, charcoal counts from pollen slides provide fire history data. Vegetation dynamics is primarily recorded on century to millennial timescale, though in a few cases to the near-decade level. During the Pleistocene/Holocene transition, conifer forests were replaced by oak-dominated deciduous forest in more mesic (moister) areas, and in the drier interior sub-Alpine woodlands fled to mountain-top retreats and were replaced by juniper woodlands. In some areas, sagebrush steppe was replaced by chaparral and oak woodlands. In the Great Basin and northern Desert Southwest, retreating sagebrush steppe and juniper woodlands were replaced by drought-loving shrub communities. As Mohave and Sonoran desert species became established near their current limits during the early Holocene, pinon pine began its northward expansion from the lower Colorado River area reaching its northern limits during the middle to late Holocene. During the middle Holocene, more xerophytic plant species dominated the interior, though more mesophytic species were common in southern California. After 5,500 rcyr BP, more moisture-loving species re-expanded in the region, with their distribution climaxing about 3,700 rcyr BP. Current plant distributions were established by about 2,000 rcyr BP following extensive periods of fire which consumed much of the lower elevation Neopluvial forest.
Waters and Stafford (Reports, 23 February 2007, p. 1122) provided useful information about the ag... more Waters and Stafford (Reports, 23 February 2007, p. 1122) provided useful information about the age of some Clovis sites but have not definitively established the temporal span of this cultural complex in the Americas. Only a continuing program of radiometric dating and careful stratigraphic correlations can address the lingering ambiguity about the emergence and spread of Clovis culture.
The Munkers Creek phase was initially defined using cultural assemblages from the William Young s... more The Munkers Creek phase was initially defined using cultural assemblages from the William Young site in the north central Flint Hills of Kansas. Radiocarbon ages from the type site are suspect due to extremely large standard deviations on all but one date and because of stratigraphic inconsistencies. Recently, samples of curated wood charcoal from stratigraphically separate cultural levels at the William Young site were submitted for dating in an attempt to better ascertain the age range for the site&amp;#x27;s Munkers Creek phase cultural ...
Integration of pollen records, and fossil woodrat midden data recovered from multiple strata of f... more Integration of pollen records, and fossil woodrat midden data recovered from multiple strata of fossil woodrat (Neotoma spp.) dens (middens) in both northern and southern Nevada reveal a detailed paleoclimatic proxy record for the Great Basin during the last 45,000 years in growing detail. Clear, late Holocene climate-linked elevational depressions of plant species` distributions have occurred throughout the Great Basin of up to 200 m below today`s and by as much as 1000 m below what they were during the middle Holocene. Horizontal plant range extentions during the Holocene reflecting the final northern most adjustments to Holocene climates range up to several hundred kilometers in the Great Basin. Well documented lags evidenced in the late Holocene response of vegetation communities to increased precipitation indicate reduced effectiveness in the ability of plant communities to assimilate excess precipitation. This resulted in significant runoff that was available for recharge. These responses, although indicating both rapid and dramatic fluctuations of climate for the Holocene, fall far short of the scale of such changes during the late Pleistocene. Extension of these results to Pleistocene woodrat den and pollen data evidence spans lasting several hundred to a thousand or more years during which significantly greater amountsmore » of precipitation would have been available for runnoff or recharge.« less
Semi-arid woodlands have dominated the middle elevations of Great Basin mountain ranges during th... more Semi-arid woodlands have dominated the middle elevations of Great Basin mountain ranges during the Holocene where subalpine woodlands prevailed during the Pleistocene. Ancient woodrat middens, and in a few cases pollen records indicate in the late Pleistocene and early Holocene woodland history lowered elevation of subalpine woodland species. After a middle Holocene retrenchment at elevations in excess of 500 meters above today, Juniper-dominated semi-arid woodland reached its late Holocene maximum areal extent during the Neoglacial (2 to 4 ka). These records, along with others indicate contracting semi-arid woodland after the Neoglacial about 1.9 ka. Desert shrub community expansion coupled with increased precariousness of wetland areas in the southern Great Basin between 1.9 and 1.5 ka coincide with shrinking wet-lands in the west-central and northern Great Basin. Coincident greater grass abundance in northern Great Basin sagebrush steppe, reaching its maximum between 1.5 and 1.2 ka, corresponds to dramatic increases in bison remains in the archaeological sites of the northern Intermontane West. Pollen and woodrat midden records indicate that this drought ended about 1.5 ka. Succeeding ameliorating conditions resulted in the sudden northward and downward expansion of pinon into areas that had been dominated by juniper during the Neoglacial. Maximum areal extent more » of pinon dominated semi-arid woodland in west-central Nevada was centered at 1.2 ka. This followed by 100 years the shift in dominance from juniper to pinon in southern Nevada semi-arid woodlands. Great Basin woodlands suffered from renewed severe droughts between .5 to .6 ka. Effectively wetter conditions during the {open_quotes}Little Ice Age{close_quotes} resulted in re-expansion of semi-arid woodland. Activities related to European settlement in the Great Basin have modified prehistoric factors or imposed new ones that are affecting woodland response to climate. « less
High resolution pa lcobol ;mtcal record .... provide sutncienl detail to correlate events regiona... more High resolution pa lcobol ;mtcal record .... provide sutncienl detail to correlate events regionally. Om.'e correlated events can he examined In tandem to determine the underlying Inputs that fashioned them. Several localities in the Great Oasin have p..1.1eobotanical records of sufficient detail to generate TC'glonal reconstructions of vl"g<'tation ~'hanges for the last 2 ka and provide conclusions as to the climates that caused them. [n southern Nevada. analysis of 266 pollen samples from the upper two-thirds of a IS-meler -Iong, lO-cm-(\\lameter set of overlapping cores retrieved from Lower Pahranagat Lake (elevation 975 meter.-;). Llnc:oln County. Nevada. Is providing a detailetl record o(vegetation change at an Interval of every 14 years over the last 3.8 ka. Samples. averaging a bout 3.8 years of pollen deposition with about 10.4 year gaps between each. outline a record of dry and wet periods with rapid onsets and terminations. Periodic Increases in the values of sagebrush (Artemisia) pollen . sometimes coincident with increases in juniper pollen renect intervals of cooler and/or wetter ('limate. Occasional. sometlmcs sevcre. drought Is marked by incrcased bur sage (Ambrosia· typc) and saltbush (Chenopodilneae) pollen and decreased regional conifer pollen. Drier climates between 3.0 and 2.5 ka. 2.4 and 2.0 ka are eclipsed In magnitude by the severe droughts of the last 1.9 ka. In particular. the d.-oughts between 1.9 and 1.6 ka and at 0.9 and 0.3 ka have little paralld dUring the late Holocem' {last 4.0 ka} in southern Nevada. The ratio of a!luatic to littoral pollen types indica les generally deeper water l.'Ondltions aoout 1.6 to 1.3 ka (also C'haracteristic of most of the early part of the record from 3.7 to 2.0 ka) and more variable. but predumlnantly more marshy. conditions during most of the last 1.3 ka. OngOing geomorphic investiga tions in the Low(:r Pahnlnaf!;at Lake ,-\\Tea s ug~est that the sudden shift from lake to marsh conditions around 1.2 to 1.4 ka Jllny be linked to the impact of extreme rainfall events. These may have eroded a s pillway thmugh the alluvial fans that Impounded the lake dUling the early portion of the Lale Holocene (3.7- 1.4 ka l. thereby redUCing the eff('etJve lake level after 1.4 ka. Increasing Pinus (pine) pollen vnlues with r('specl to Junipen.lS ijunipcr) pollen values indicate that pinon pine is now more abundant in the southern Creal Basin than at a ny time since the beginning of the -NeoglaCial". about 4.0 ka. This is due not only to a shift from harsher winters about 2.0 ka (in pa ri evidenced by the decline ()f .Juniper dominan('c in the woodland), but also to period s of summer -s hlftcd rainfall (jnc rea~ed summer rainfall often with decreased winter rainfall). which favored seedling survival rluring the summer. In southern Nevnda. evidence of summer·shifted precipita tion during the first millennium of the Christian Era is seen In the expansion of grasses (reflected In Poaceae pollenl prererling expansions of pinon pine w1thout coincident expansions of winter preclpitation·lov1ng speCies such as sagebrush and j Ullipcr. To the north. pollen and woodral middcn records from the Carson Sink of the central Great Basin (Lead Lake. Nevada) evidence summer· shifted rainfall in contemporaneous expansion of pinon pine into semi·arld woodlands. Pollen records from the northern Great Basin (in particular. the hlgh· resolution pollen record from Diamond Pond . sout.h -central Oregon) Indicate grass expansion at the expense of juniper at the same time. providing further evidence of a major period of summer-shifted preci pitation that characterized much of the Intermountain West.
The microfossil record from the Playa Vista cores clearly reflects both local and regional patter... more The microfossil record from the Playa Vista cores clearly reflects both local and regional patterns of environmental change. Some of these changes may have been the result of regional or local climatic change or both, but others may reflect changes in geomorphic processes as the result of climatic, tectonic, or oceanic (e.g., tidal, current, or wave action) influences. Some of these influences, as well as their impact on Native Americans, may be revealed through a more detailed local and regional comparison of both terrestrial and estuary environments over time, as reflected in the micro- and macrofossil records. Three factors must be examined in greater detail in order to compare these records: (1) our knowledge of the vegetation structure of prehistoric wetlands in southern California ( ie., whether there are adequate modern analogues with which we can compare our reconstructions); (2) how this vegetation structure is reflected in the pollen record; and (3) what impact the directi...
Pollen, spore, and algae records from a variety of depositional contexts provide 12 kyr of paleoc... more Pollen, spore, and algae records from a variety of depositional contexts provide 12 kyr of paleoclimatic proxy data for southwestern North America. Macrofossils and pollen from ancient woodrat nests in the drier interior provide species-level identifications, and exact spatial and chronometric information. Occasionally, charcoal counts from pollen slides provide fire history data. Vegetation dynamics is primarily recorded on century to millennial timescale, though in a few cases to the near-decade level. During the Pleistocene/Holocene transition, conifer forests were replaced by oak-dominated deciduous forest in more mesic (moister) areas, and in the drier interior sub-Alpine woodlands fled to mountain-top retreats and were replaced by juniper woodlands. In some areas, sagebrush steppe was replaced by chaparral and oak woodlands. In the Great Basin and northern Desert Southwest, retreating sagebrush steppe and juniper woodlands were replaced by drought-loving shrub communities. As Mohave and Sonoran desert species became established near their current limits during the early Holocene, pinon pine began its northward expansion from the lower Colorado River area reaching its northern limits during the middle to late Holocene. During the middle Holocene, more xerophytic plant species dominated the interior, though more mesophytic species were common in southern California. After 5,500 rcyr BP, more moisture-loving species re-expanded in the region, with their distribution climaxing about 3,700 rcyr BP. Current plant distributions were established by about 2,000 rcyr BP following extensive periods of fire which consumed much of the lower elevation Neopluvial forest.
Waters and Stafford (Reports, 23 February 2007, p. 1122) provided useful information about the ag... more Waters and Stafford (Reports, 23 February 2007, p. 1122) provided useful information about the age of some Clovis sites but have not definitively established the temporal span of this cultural complex in the Americas. Only a continuing program of radiometric dating and careful stratigraphic correlations can address the lingering ambiguity about the emergence and spread of Clovis culture.
The Munkers Creek phase was initially defined using cultural assemblages from the William Young s... more The Munkers Creek phase was initially defined using cultural assemblages from the William Young site in the north central Flint Hills of Kansas. Radiocarbon ages from the type site are suspect due to extremely large standard deviations on all but one date and because of stratigraphic inconsistencies. Recently, samples of curated wood charcoal from stratigraphically separate cultural levels at the William Young site were submitted for dating in an attempt to better ascertain the age range for the site&amp;#x27;s Munkers Creek phase cultural ...
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