Spring dust in western North America and its interannual variability – Understanding the role of local and transported dust

Author(s):  
Dongchul Kim ◽  
Mian Chin ◽  
Carlos A. Cruz ◽  
Daniel Tong ◽  
Hongbin Yu
2008 ◽  
Vol 73 (1) ◽  
pp. 83-102 ◽  
Author(s):  
Phil R. Geib ◽  
Edward A. Jolie

Despite ranking at the low end of the continuum in net caloric benefit relative to other foods, small seeds assumed great dietary importance in many parts of the world, including western North America. In a series of publications, Adovasio (1970a, 1974, 1980, 1986) argued that coiled basketry technology was invented in the eastern Great Basin during the early Holocene as a specialized food-processing technique. Coiled baskets are indeed useful for collecting and processing seeds, but it does not necessarily follow that they were originally designed for this purpose. A whole basket recently discovered at Cowboy Cave in southeastern Utah returned an AMS radiocarbon assay of 7960 ± 50 B.P., making it currently the earliest directly dated coiled basket from the Americas. This basket is not a parching tray and likely had nothing to do with harvesting seeds. We discuss the implications of this find with regard to tracking the temporal spread of coiled basketry technology in western North America and the role of coiled and twined forms in the initiation of small seed exploitation. Coiled and twined baskets for small seed processing may result from reconfiguration of existing technologies to create novel forms suited to a new food exploitation strategy.


1984 ◽  
Vol 62 (2) ◽  
pp. 336-342 ◽  
Author(s):  
James E. Eckenwalder

Fossilized leaves resembling those of contemporary intersectional hybrids occur together with leaves assignable to sections Tacamahaca Spach and Aigeiros Duby in Miocene and Pliocene sediments in western North America. They are not referable to any particular extant hybrid species and are assigned to the extinct Populus × parcedentata Axelrod. Together with other evidence, these ancient hybrids raise questions concerning the evolutionary role of hybridization between species of the two parent sections. Present evidence about hybridization as a bridge for intersectional gene flow is contradictory. The apparent absence of backcrossed individuals in most studied hybridizing populations is offset by morphological pecularitics shared by sympatric cottonwoods and balsam poplars that are not shared with their cladistic sister species.


1971 ◽  
Vol 103 (9) ◽  
pp. 1207-1216 ◽  
Author(s):  
D. F. Hardwick

AbstractClimatic factors which may control the time of occurrence of seasonal phenomena are discussed, and in particular the role of temperature in initiating periodic cycles in animals in continental North America. The seasonal flight periods of nine species of noctuid moths at two localities in western North America are considered in terms of the lengths of the summer season at these localities. Among the species discussed, those that are in flight prior to midsummer fly earlier, and those that are in flight after midsummer fly later, in the area with a long summer than in the area with a short summer. A factor termed the "phenological date," which is based on the number of days above 42°F in a given area, is proposed as a measure of seasonal development. The factors of photoperiod and temperature that may have a controlling influence on periodic events are discussed. Variance analysis suggests that the phenological date has greater predictive value in estimating the periods of flight of the species considered than have the other factors.


2020 ◽  
Author(s):  
Brendan Byrne ◽  
Junjie Liu ◽  
A. Anthony Bloom ◽  
Kevin Bowman ◽  
Zachary Butterfield ◽  
...  

<p>Semi-arid ecosystems have been recognized as an important driver of interannual variability (IAV) in the growth rate of atmospheric CO2. However, the importance of these ecosystems for IAV in gross primary productivity (GPP) and net ecosystem exchange (NEE) over North America is not well characterized. In this study, we examine IAV over temperate North America using NEE constrained by surface-based and space-based atmospheric CO2 measurements over 2010–2015 and upscaled GPP from FluxSat over 2001–2017. We show that the arid west of North America provides a larger contribution to IAV in GPP and NEE than the more productive eastern half of North America. This occurs because flux anomalies in western North America are temporally coherent across the growing season leading to an amplification of GPP and NEE for wet years. In contrast, IAV in eastern North America shows seasonal compensation effects, wherein positive anomalies during April–June are compensated for by negative anomalies during July–September. </p>


2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Alexander Gershunov ◽  
Tamara Shulgina ◽  
Rachel E. S. Clemesha ◽  
Kristen Guirguis ◽  
David W. Pierce ◽  
...  

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