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Accueil du site → Doctorat → États-Unis → 2000 → Modeling plant species’ range limiters for paleoclimatic reconstruction in the Sonoran Desert over the past 50,000 years

Arizona State University (2000)

Modeling plant species’ range limiters for paleoclimatic reconstruction in the Sonoran Desert over the past 50,000 years

Arundel, Samantha Lynn Thompson

Titre : Modeling plant species’ range limiters for paleoclimatic reconstruction in the Sonoran Desert over the past 50,000 years

Auteur : Arundel, Samantha Lynn Thompson

Université de soutenance : Arizona State University

Grade : Doctor of Philosophy (PhD) 2000

Résumé
Proxy data for past climates are needed from every geographical region. Quantified paleoclimate reconstructions can be used to tune General Circulation Models (GCM). In deserts, plant proxy data may be extracted from rodent middens. Macrofossils found in middens are often identifiable to the species level. At this level, climatic limitations particular to each individual taxon can be determined by analyzing their modern distribution. When species’ distributions are found to change in the fossil record, their climatic limiters can be used for paleoclimatic : interpretation. Specific limits should be known for each species used in a climate reconstruction. Range limiters can be ascertained through autecological study of a species, but these studies take years to complete. The method presented here used a high-resolution midden data set by determining the climatic limiters to plant distributions, instead of the species’ climate spaces. This research relied on plant macrofossil data from packrat middens to track fluxes in species’ distributions in the Sonoran Desert since the last glacial period (past 50,000 years). The research method developed objective, quantified climatic limitations for 35 plant species’ distributions, using a Geographic Information System for both analysis and display, along with digital datasets and specialized climate interpolation software. The quantified climatic limiters of plant species’ distributions provided a foundation for reconstructing paleoclimates. Research results suggest that the most important differences between glacial and modern climates were almost 4.5°C lower mean winter temperatures and somewhat lower temperatures during the monsoon (July-August). Mean monsoon rainfall was halved, mean fall precipitation may have been more than double today’s values, while minimum winter precipitation was around 50% more than today. Four to five millimeters more rain fell during the summer (May-June). Winter and monsoon temperatures increased gradually to modern values. The largest drop in fall precipitation occurred between the late Wisconsin and the early Holocene. Monsoon precipitation made half the step between Wisconsin levels and modern levels during the late Wisconsin ; the other half step lasted through the Holocene. In other words, almost-modern levels of monsoon rainfall were established by the early Holocene, but precipitation did not exceed today’s amounts.

Mots clés : Geotechnology, Climatic reconstruction, Applied sciences, Paleoecology, Geography, Earth sciences, Range limiters, Sonoran Desert

Accès au document : Proquest Dissertations & Theses

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