Tertiary Centers and Migration Routes

Chaney, Ralph W.

doi:10.2307/1943260

Cited by 137 publications

(69 citation statements)

References 5 publications

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“…Our calculations show that the carbon required for growth of the deciduous leaf canopies could be fixed in around 10 to 25 d, a period representing only 5% to 15% of the 6-month growing season. Therefore, preliminary scaling of A indicates a possible solution to the P n paradox, and suggests that the deciduous leaf habit may not be as critical to the carbon balance of polar forests as previously postulated (Chaney, 1947;Hickey, 1984;Wolfe and Upchurch, 1987;Spicer and Chapman, 1990).…”

Section: Discussionmentioning

confidence: 64%

“…However, in common with modern polar vegetation, they would have experienced strong seasonality in daylength (Creber and Chaloner, 1985). For example, trees at a latitude of 69°are exposed to continuous sunlight for 6 weeks in the summer and an equal period of darkness in winter (Beerling and Osborne, 2002).Fossils suggest that polar forests were largely deciduous (Spicer and Chapman, 1990), and this is frequently interpreted as an adaptation for minimizing canopy respiration during the warm, dark polar winter (Chaney, 1947;Hickey, 1984; Wolfe and Upchurch, 1987; Spicer and Chapman, 1990). However, comparative analyses of evergreen and deciduous trees have recently overturned this paleobotanical dogma (Royer et al, 2003).…”

mentioning

confidence: 99%

“…Fossils suggest that polar forests were largely deciduous (Spicer and Chapman, 1990), and this is frequently interpreted as an adaptation for minimizing canopy respiration during the warm, dark polar winter (Chaney, 1947;Hickey, 1984; Wolfe and Upchurch, 1987; Spicer and Chapman, 1990). However, comparative analyses of evergreen and deciduous trees have recently overturned this paleobotanical dogma (Royer et al, 2003).…”

mentioning

confidence: 99%

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The Penalty of a Long, Hot Summer. Photosynthetic Acclimation to High CO2 and Continuous Light in “Living Fossil” Conifers

Osborne

Beerling

2003

Plant Physiology

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Deciduous forests covered the ice-free polar regions 280 to 40 million years ago under warm "greenhouse" climates and high atmospheric pCO 2 . Their deciduous habit is frequently interpreted as an adaptation for minimizing carbon losses during winter, but experiments with "living fossils" in a simulated warm polar environment refute this explanation. Measured carbon losses through leaf abscission of deciduous trees are significantly greater than losses through winter respiration in evergreens, yet annual rates of primary productivity are similar in all species. Here, we investigate mechanisms underlying this apparent paradox by measuring the seasonal patterns of leaf photosynthesis (A) under pCO 2 enrichment in the same trees. During spring, A increased significantly in coastal redwood (Sequoia sempervirens), dawn redwood (Metasequoia glyptostroboides), and swamp cypress (Taxodium distichum) at an elevated pCO 2 of 80 Pa compared with controls at 40 Pa. However, strong acclimation in Rubisco carboxylation capacity (V c,max ) completely offset the CO 2 response of A in all species by the end of 6 weeks of continuous illumination in the simulated polar summer. Further measurements demonstrated the temporary nature of acclimation, with increases in V c,max during autumn restoring the CO 2 sensitivity of A. Contrary to expectations, the acclimation of V c,max was not always accompanied by accumulation of leaf carbohydrates, but was associated with a decline in leaf nitrogen in summer, suggesting an alteration of the balance in plant sources and sinks for carbon and nitrogen. Preliminary calculations using A indicated that winter carbon losses through deciduous leaf abscission and respiration were recovered by 10 to 25 d of canopy carbon fixation during summer, thereby explaining the productivity paradox.Geological evidence shows that today's permanent polar ice sheets are a recent phenomenon, appearing some 34 million years ago (Ma) in Antarctica and 3 Ma in the Arctic (Zachos et al., 2001). Earlier periods of global warmth extending back to 280 Ma enabled forests to cover the polar regions and reach latitudes as high as 85°in both hemispheres (Spicer and Chapman, 1990). These ancient high latitude forests quite likely grew in an environment unlike any on Earth today, with mean winter temperatures above freezing (Pole and Macphail, 1996;Markwick, 1998; Tripati et al., 2001;Dutton et al., 2002), and an atmospheric pCO 2 enriched over current ambient levels (Royer et al., 2001). However, in common with modern polar vegetation, they would have experienced strong seasonality in daylength (Creber and Chaloner, 1985). For example, trees at a latitude of 69°are exposed to continuous sunlight for 6 weeks in the summer and an equal period of darkness in winter (Beerling and Osborne, 2002).Fossils suggest that polar forests were largely deciduous (Spicer and Chapman, 1990), and this is frequently interpreted as an adaptation for minimizing canopy respiration during the warm, dark polar winter (Chaney, 1947;Hickey, 1984; Wolfe...

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Section: Discussionmentioning

confidence: 64%

mentioning

confidence: 99%

mentioning

confidence: 99%

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The Penalty of a Long, Hot Summer. Photosynthetic Acclimation to High CO2 and Continuous Light in “Living Fossil” Conifers

Osborne

Beerling

2003

Plant Physiology

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“…1, [4][5][6][7] argues that it was an adaptation to photoperiod, allowing the avoidance of carbon losses by respiration from a canopy of leaves unable to photosynthesize in the darkness of warm polar winters [8][9][10][11] . Here we test this proposal with experiments using 'living fossil' tree species grown in a simulated polar climate with and without CO 2 enrichment.…”

mentioning

confidence: 99%

Carbon loss by deciduous trees in a CO2-rich ancient polar environment

Royer

Osborne

Beerling

2003

Nature

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“…On this basis we may conclude that the successive phases of the Devonian lowland vegetation, as recorded by the Psilophyton, Hyenia, and Archaeopteris Floras (Arber, 1921;Dorf, 1955), represent no more than the replacement of different ecologic units migrating from upland into lowland areas, and not evolutionary change as such. Analogous replacements are well documented for the Late Pennsylvanian (Elias, 1933), and also for the Tertiary as shown by the time-space relations of the Arcto-Tertiary, Neotropical-Tertiary, and MadroTertiary Geofloras (Chaney, 1947;Axelrod, 1939;1958).…”

Section: Evolutionary Significance Of Devonian Psilophytesmentioning

confidence: 64%

Evolution of the Psilophyte Paleoflora

Axelrod

1959

Evolution

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Tertiary Centers and Migration Routes

Cited by 137 publications

References 5 publications

The Penalty of a Long, Hot Summer. Photosynthetic Acclimation to High CO2 and Continuous Light in “Living Fossil” Conifers

The Penalty of a Long, Hot Summer. Photosynthetic Acclimation to High CO2 and Continuous Light in “Living Fossil” Conifers

Carbon loss by deciduous trees in a CO2-rich ancient polar environment

Evolution of the Psilophyte Paleoflora

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