HR: 1340h
AN: B23A-0922    [Abstracts]
TI: A 3PG-based Model to Simulate Delta-13C Content in Three Tree Species in The Mica Creek Experiment Watershed, Idaho
AU: * Wei, L
EM: liangwei@vandals.uidaho.edu
AF: Department of Forest Resources, University of Idaho, P.O. Box 441133, 6th & Line St, Moscow, ID 83843, United States
AU: Marshall, J D
EM: jdm@uidaho.edu
AF: Department of Forest Resources, University of Idaho, P.O. Box 441133, 6th & Line St, Moscow, ID 83843, United States
AB: 3PG (Physiological Principles in Predicting Growth), a process-based physiological model of forest productivity, has been widely used and well validated. Based on 3PG, a 3PG-δ¹³C model to simulate δ¹³C content in plant tissue is built in this research. 3PG calculates carbon assimilation from utilizable absorbed photosynthetically active radiation (PAR), and calculates stomatal conductance from maximum canopy conductance multiplied by physiological modifier which includes the effect of water vapor deficit and soil water. Then the equation of Farquhar and Sharkey (1982) was used to calculate δ¹³C content in plant. Five even-aged coniferous forest stands located near Clarkia, Idaho (47°15'N, 115°25'W) in Mica Creek Experimental Watershed, were chosen to test the model, (2 stands had been partial cut (50% canopy removal in 1990) and 3 were uncut). MCEW has been extensively investigated since 1990 and many necessary parameters needed for 3PG are readily available. Each of these sites is located near a UI Meteorological station, which recorded half-hourly climatic data since 2003. These site-specific climatic data were extend to 1991 by correlating with data from a nearby SNOTEL station (SNOwpack TELemetry, NRCS, 47°9' N, 116°16' W). Forest mensuration data were obtained form each stand using variable radius plots (VRP). Three tree species, which consist more than 95% of all trees, were parameterized for 3PG model, including: grand fir (Abies grandis Donn ex D. Don), western red cedar (Thuja plicat Donn ex D. Don a) and Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco). Because 4 out of 5 stands have mixed species, we also used parameters for mixed stands to run the model. To stabilize, the model was initially run under average climatic data for 20 years, and then run under the actual climatic data from 1991 to 2006. As 3PG runs in a monthly time step, monthly δ¹³C values were calculated first, and then yearly values were calculated by weighted averages. For testing the model, tree cores were collected from each stand and species. Ring-widths of tree cores were measured and cross-dated with a ring-width chronology obtained from MCEW. δ¹³C contents of tree- ring samples from known year were tested. Preliminary results indicate 3PG-δ¹³C simulated values are consistent with observed values in tree-rings. δ¹³C values of modeled species are different: western red cider has the highest delta¹³C values among the three species and western larch has the lowest.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting