Brett J. Tipple

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The relation between the partial pressure of atmospheric carbon dioxide (pCO2) and Paleogene climate is poorly resolved. We used stable carbon isotopic values of di-unsaturated alkenones extracted from deep sea cores to reconstruct pCO2 from the middle Eocene to the late Oligocene (approximately 45 to 25 million years ago). Our results demonstrate that pCO2(More)
The evolution of grasses using C4 photosynthesis and their sudden rise to ecological dominance 3 to 8 million years ago is among the most dramatic examples of biome assembly in the geological record. A growing body of work suggests that the patterns and drivers of C4 grassland expansion were considerably more complex than originally assumed. Previous(More)
Leaf-wax n-alkanes (2)H/(1)H ratios are widely used as a proxy in climate reconstruction. Although the broad nature of the relationship between n-alkanes δ(2)H values and climate is appreciated, the quantitative details of the proxy remain elusive. To examine these details under natural environmental conditions, we studied a riparian broadleaf angiosperm(More)
Local climate and environment broadly affect the deuterium/hydrogen (D/H) ratios of plant materials, however the degree to which an individual plant’s leaf waxes D/H ratios are affected by these parameters remains in question. Understanding these issues is particularly important in order to reconstruct past floral transitions and changes in the(More)
Isotope hydrology has focused largely on landscapes away from densely inhabited regions. In coming decades, it will become increasingly more important to focus on water supplies and dynamics within urban systems. Stable isotope analyses provide important information to water managers within large cities, particularly in arid regions where evaporative(More)
This study investigates stable carbon and hydrogen isotope compositions of leaf wax n-alkanes from 3 angiosperm and 2 conifer species from a semi-desert natural environment. The dC and dD n-C27 alkane data show a clear distinction between Populus tremuloides/Syringa vulgaris ( 31.9 to 32.7‰ and 168 to 186‰, respectively) and Pinus sylvestris/ Picea pungens(More)
The extent to which both water source and atmospheric humidity affect δ(2)H values of terrestrial plant leaf waxes will affect the interpretations of δ(2)H variation of leaf waxes as a proxy for hydrological conditions. To elucidate the effects of these parameters, we conducted a long-term experiment in which we grew two tree species, Populus fremontii and(More)