A 36,000-yr vegetation history from the Peloncillo Mountains, southeastern Arizona, USA

Holmgren, Camille A.; Betancourt, Julio L.; Rylander, Kate Aasen

doi:10.1016/j.palaeo.2006.02.017

Cited by 57 publications

(49 citation statements)

References 43 publications

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“…The opportunity for assessing the seasonality of precipitation changes, a rare opportunity in proxy records, is possible due to the high taxonomic resolution afforded by packrat midden records where species-level identifications are common. The importance of summer precipitation in the Borderlands was inferred previously from the diverse suite of C 4 grasses and summer-flowering annuals found in glacial-aged packrat middens (Betancourt et al, 2001;Holmgren et al, 2003;Holmgren et al, in prep), although the amount of summer precipitation was unknown. We now estimate that summer precipitation was equivalent to at least 50% of modern values and may have reached amounts similar to today.…”

Section: Late Pleistocene Climatementioning

confidence: 93%

Inferences about winter temperatures and summer rains from the late Quaternary record of C₄ perennial grasses and C₃ desert shrubs in the northern Chihuahuan Desert

Holmgren

Norris

Betancourt

2006

J Quaternary Science

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Late Quaternary histories of two North American desert biomes-C 4 grasslands and C 3 shrublands-are poorly known despite their sensitivity and potential value in reconstructing summer rains and winter temperatures. Plant macrofossil assemblages from packrat midden series in the northern Chihuahuan Desert show that C 4 grasses and annuals typical of desert grassland persisted near their present northern limits throughout the last glacialinterglacial cycle. By contrast, key C 3 desert shrubs appeared somewhat abruptly after 5000 cal yr B.P. Bioclimatic envelopes for select C 4 and C 3 species are mapped to interpret the glacialinterglacial persistence of desert grassland and the mid-to-late Holocene expansion of desert shrublands. The envelopes suggest relatively warm Pleistocene temperatures with moist summers allowed for persistence of C 4 grasses, whereas winters were probably too cold (or too wet) for C 3 desert shrubs. Contrary to climate model results, core processes associated with the

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Section: Late Pleistocene Climatementioning

confidence: 93%

Inferences about winter temperatures and summer rains from the late Quaternary record of C₄ perennial grasses and C₃ desert shrubs in the northern Chihuahuan Desert

Holmgren

Norris

Betancourt

2006

J Quaternary Science

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“…Clovis Mammoth Behavior and Extinction. During the Clovis period, evidence for C 4 grasses in the SPV riparian corridor is lacking, but C 4 grasses probably grew on the bajada and nearby hillsides (9,12,13,17). We propose that Clovis mammoths sought new C 4 plant growth farther from the river during the summer rainy season and remained closer to the river, foraging on mixed C 3 -C 4 plants, during the winter.…”

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confidence: 86%

“…Large pluvial lakes were surrounded by hillsides covered with pinyon-juniper woodlands and rich understories of C 3 shrubs, C 4 annuals, and C 4 grasses (11,12); springs and shallow ponds were supported by a high water table (10); and a C 4 grassland stretched from southern Arizona to central Texas (12)(13)(14)(15)(16)(17). A warm and arid period began around 13,000 14 C yBP (15,000 cal BP), culminating in a severe drought that coincided with mammoth extinction and Clovis occupation of the SPV (10,900 14 C yBP or 12,800 cal BP) (18).…”

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confidence: 99%

Isotopic paleoecology of Clovis mammoths from Arizona

Metcalfe

Longstaffe

Ballenger

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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The causes of megafaunal extinctions in North America have been widely debated but remain poorly understood. Mammoths (Mammuthus spp.) in the American Southwest were hunted by Clovis people during a period of rapid climate change, just before the regional onset of Younger Dryas cooling and mammoth extirpation. Thus, these mammoths may provide key insights into late Pleistocene extinction processes. Here we reconstruct the seasonal diet and climatic conditions experienced by mammoths in the San Pedro Valley of Arizona, using the carbon ( 13 C/ 12 C) and oxygen ( 18 O/ 16 O) isotope compositions of tooth enamel. These records suggest that Clovis mammoths experienced a warm, dry climate with sufficient summer rainfall to support seasonal C 4 plant growth. Monsoon intensity may have been reduced relative to the preceding time period, but there is no isotopic evidence for severe drought. However, it is possible that the "Clovis drought", inferred from stratigraphic evidence, occurred suddenly at the end of the animals' lives and thus was not recorded in the enamel isotopic compositions. Unlike mammoths that lived before the Last Glacial Maximum, Clovis mammoths regularly increased C 4 grass consumption during summer, probably seeking seasonally green grasslands farther from the river valley. This predictable seasonal behavior may have made mammoths easier to locate by Clovis hunters. Furthermore, Clovis mammoths probably had no previous experience of such sudden climatic change as is believed to have occurred at the time of their extinction.geochemistry | stable isotopes | bioapatite | paleoclimate | Paleoindian

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“…Whereas drivers are typically presented as time series concurrent with biological responses ( Fig. 2A), triggers are discrete events in time or relatively short, discrete sections of a time series (e.g., an El Niño period, Holmgren et al 2006).…”

Section: A Common Framework For Describing State Changementioning

confidence: 99%

Analysis of abrupt transitions in ecological systems

Bestelmeyer

Ellison

Fraser³

et al. 2011

Ecosphere

256

314

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Abstract. The occurrence and causes of abrupt transitions, thresholds, or regime shifts between ecosystem states are of great concern and the likelihood of such transitions is increasing for many ecological systems. General understanding of abrupt transitions has been advanced by theory, but hindered by the lack of a common, accessible, and data-driven approach to characterizing them. We apply such an approach to 30-60 years of data on environmental drivers, biological responses, and associated evidence from pelagic ocean, coastal benthic, polar marine, and semi-arid grassland ecosystems. Our analyses revealed one case in which the response (krill abundance) linearly tracked abrupt changes in the driver (Pacific Decadal Oscillation), but abrupt transitions detected in the three other cases (sea cucumber abundance, penguin abundance, and black grama grass production) exhibited hysteretic relationships with drivers (wave intensity, sea-ice duration, and amounts of monsoonal rainfall, respectively) through a variety of response mechanisms. The use of a common approach across these case studies illustrates that: the utility of leading indicators is often limited and can depend on the abruptness of a transition relative to the lifespan of responsive organisms and observation intervals; information on spatiotemporal context is useful for comparing transitions; and ancillary information from associated experiments and observations aids interpretation of response-driver relationships. The understanding of abrupt transitions offered by this approach provides information that can be used to manage state changes and underscores the utility of long-term observations in multiple sentinel sites across a variety of ecosystems.

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A 36,000-yr vegetation history from the Peloncillo Mountains, southeastern Arizona, USA

Cited by 57 publications

References 43 publications

Inferences about winter temperatures and summer rains from the late Quaternary record of C₄ perennial grasses and C₃ desert shrubs in the northern Chihuahuan Desert

Inferences about winter temperatures and summer rains from the late Quaternary record of C₄ perennial grasses and C₃ desert shrubs in the northern Chihuahuan Desert

Isotopic paleoecology of Clovis mammoths from Arizona

Analysis of abrupt transitions in ecological systems

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A 36,000-yr vegetation history from the Peloncillo Mountains, southeastern Arizona, USA

Cited by 57 publications

References 43 publications

Inferences about winter temperatures and summer rains from the late Quaternary record of C4 perennial grasses and C3 desert shrubs in the northern Chihuahuan Desert

Inferences about winter temperatures and summer rains from the late Quaternary record of C4 perennial grasses and C3 desert shrubs in the northern Chihuahuan Desert

Isotopic paleoecology of Clovis mammoths from Arizona

Analysis of abrupt transitions in ecological systems

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Inferences about winter temperatures and summer rains from the late Quaternary record of C₄ perennial grasses and C₃ desert shrubs in the northern Chihuahuan Desert

Inferences about winter temperatures and summer rains from the late Quaternary record of C₄ perennial grasses and C₃ desert shrubs in the northern Chihuahuan Desert