HR: 14:10h
AN: B13B-03    [Abstracts]
TI: Airsheds, Isotopes and Ecosystem Metabolism in Mountainous Terrain
AU: * Sulzman, E
EM: elizabeth.sulzman@oregonstate.edu
AF: Department of Crops and Soil Science, Oregon State University, 3017 Agricultural Life Sciences Buidling, Corvallis, OR 97331 United States
AU: Barnard, H
EM: holly.barnard@oregonstate.edu
AF: Department of Forest Science, Oregon State University, 321 Richardson Hall, Corvallis, OR 97331 United States
AU: Bond, B J
EM: barbara.bond@oregonstate.edu
AF: Department of Forest Science, Oregon State University, 321 Richardson Hall, Corvallis, OR 97331 United States
AU: Czarnomski, N M
EM: nicole.czarnomski@oregonstate.edu
AF: Department of Forest Science, Oregon State University, 321 Richardson Hall, Corvallis, OR 97331 United States
AU: Hauck, M
EM: mark.hauck@oregonstate.edu
AF: Department of Forest Science, Oregon State University, 321 Richardson Hall, Corvallis, OR 97331 United States
AU: Kayler, Z
EM: zachary.kayler@oregonstate.edu
AF: Department of Forest Science, Oregon State University, 321 Richardson Hall, Corvallis, OR 97331 United States
AU: Mix, A C
EM: amix@coas.oregonstate.edu
AF: College of Oceanic and Atmospheric Sciences, Oregon State University, Burt Hall, Corvallis, OR 97331 United States
AU: Pypker, T
EM: pypkert@coas.oregonstate.edu
AF: College of Oceanic and Atmospheric Sciences, Oregon State University, Burt Hall, Corvallis, OR 97331 United States
AU: Rugh, W
EM: rughb@coas.oregonstate.edu
AF: College of Oceanic and Atmospheric Sciences, Oregon State University, Burt Hall, Corvallis, OR 97331 United States
AU: Unsworth, M
EM: unswortm@coas.oregonstate.edu
AF: College of Oceanic and Atmospheric Sciences, Oregon State University, Burt Hall, Corvallis, OR 97331 United States
AB: At least 20% of the terrestrial surface of the earth is covered by mountains, which contain many of the world's most productive ecosystems. Interactions between vegetation and the physical environment are often very different in mountains than on flat land. However, few studies have addressed these unique interactions, and many of the tools used to measure and monitor ecosystem metabolism are difficult or impossible to use in complex, mountainous terrain. In a project we call the "Andrews Airshed study" located in western Oregon Cascades, we aim to identify and explore sources of variation in the isotopic composition of ecosystem respiration (δ¹³C_R-eco) and airflow patterns in cold-air drainage, with the eventual aim of "inverting" this understanding so that we can use δ¹³C_R-eco to monitor intra- and inter-annual variations in ecosystem metabolism on a basin scale. We are measuring patterns of airflow, quantifying the CO₂ concentration in the flow, and measuring the carbon isotope composition of ecosystem-respired CO₂ as well as soil-respired CO₂ (δ¹³C_R-soil), which accounts for more than half of δ¹³C_R-eco. We have designed an automated air sampling device that we programmed to sample air at 10 ppm intervals from 30 m above the stream in our 100 ha, deeply-incised watershed. Samples are collected via Valco valves into stainless steel tubing that can be connected directly to an isotope ratio mass spectrometer. We also designed and installed soil gas sampling probes, which are located in five 10 m² sampling plots from ridge top to valley floor to the opposite ridge top. Weekly samples (May-Sept, 2005) of air from soil and the nocturnal air flow show seasonal variation in δ¹³C_R-eco over a 2 per mil range, with more enriched values corresponding to lower soil moisture. Soil-respired CO₂ also reveal seasonality and are isotopically enriched compared with above-ground air. δ¹³C_R-soil values from north- and south-facing slopes of the watershed differ by 1 per mil, with south-facing values consistently enriched relative to those of the north-facing slope. We are concurrently conducting studies to determine the appropriate footprint of respired CO₂ in the nocturnal airstream, which will allow us to overlay the data properly.
DE: 1040 Radiogenic isotope geochemistry
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
DE: 3322 Land/atmosphere interactions (1218, 1631, 1843)
SC: Biogeosciences [B]
MN: Fall Meeting 2005