Jennifer C McElwain, A CO2 partial pressure based paleoaltimeter using Quercus kelloggii and Quercus douglasii

Paleoelevation and how the topography of the earth has changed through time remains one of the great geological unknowns An NSF funded project to develop a new method of estimating past elevation of land surfaces will be undertaken over the next three years-. The new paleoaltimeter method will first be tested extensively on modern vegetation- specifically I want to undertake detailed investigation of how aspects of leaf anatomy and morphology change along elevational and latitudinal gradients in response to decreases in CO2 partial pressure and temperature respectively. This new tool once developed will enable us to build a detailed uplift history of the Sierra Nevadas, using fossil floras, and address the current controversy as to whether these mountains have uplifted relatively recently (since the Middle Miocene ~14 Ma) or achieved their current elevation well before the Miocene and have actually decreased in mean elevation by as much as 2000 meters over the last 14 million years.

In order to undertake this research I will collect herbarium specimens of Quercus kelloggii (California Black Oak) and Quercus douglasii (California Blue Oak) across their entire native range in California and Southern Oregon. The collection protocol will involve collection of duplicate herbarium specimens (one for the Field Museum and one for the local state park/state forest or national park or where suitable collections facilities are not available duplicate herbarium specimens will be deposited in the University and Jepson Herbarium, University of California Berkeley). Fruiting or flowering branches will be targeted for both herbarium specimens. 10 to 20 additional individual leaves from random areas within the plant canopy, including shade and full sun leaves will be sampled from each tree for (a) cuticular analysis to study leaf surface anatomy and micromorphology, (b) leaf physiognomy analysis (size and shape, degree of lobing, leaf venation etc) and (c) for future molecular analysis. Permanent slides of leaf cuticle will be made and housed within Field Museum Collections. Ecological, habit, aspect and precise latitude, longitude and elevation data will be recorded for each tree sampled. A soil ph test in the field will be undertaken for each tree sampled using a probe but no soil samples will be collected.

Photo Credits: Title, Research, Treefrog and Blue Oak (Mike Benard),