Show simple item record

Improving Models of Forest Carbon and Water Cycling: Revisiting Assumptions and Incorporating Variability

dc.contributor.advisor Oren, Ram Ward, Eric Jason 2012-05-25T20:05:36Z 2012-05-25T20:05:36Z 2012
dc.description.abstract <p>This dissertation examines issues concerning sap flux scaled estimates of the canopy-averaged transpiration rate of trees per unit leaf area (E<sub>L</sub>) and stomatal conductance (G<sub>S</sub>), as well as their implications in the water and carbon balance of individuals and stands, with the final goal of an integrated assessment of 11 years of such data from two species (<italic>Pinus taeda</italic> and <italic>Liquidambar styraciflua</italic>) at the Duke Free Air Carbon dioxide Enrichment (Duke FACE) facility. These issues include (1) the effects of allometric relationships and xylem characteristics on the gas phase transport of water from leaves and the hydraulic supply of it, (2) consideration of the hydraulic capacitance in the inference of stomatal behavior from sap flux data and (3) the dynamic modeling of stomatal conductance to environmental drivers using Bayesian techniques. It is shown that a) for resolution of sap flux in conifers at the scale of minutes under dynamic conditions, time constants for both stomatal responses and hydraulic capacitance of sapwood must be considered, (b) nighttime conductance can lead to large errors in rates of sap flux measured under some conditions, (c) variation in allometry between <italic>P. taeda</italic> individuals can lead to different rates of transpiration and carbon assimilation per unit leaf area and that (d) hydraulic time constants for the stems of mature <italic>P. taeda</italic> at Duke FACE trees varied by the stem length considered and were on the order of 30-45 minutes for a 10-m segment. An analysis incorporating all these elements leads to the conclusions that (e) both elevated CO<sub>2</sub> (eCO<sub>2</sub>) and fertilization (FR) resulted in proportionally larger reductions in the E<sub>L</sub> and G<sub>S</sub> of P. taeda as soil moisture decreased with (f) eCO<sub>2</sub> having little to no effect in months of high soil moisture and (g) FR leading to ~14% reduction of GS under high soil moisture in absence of eCO<sub>2</sub>, while (h) both eCO<sub>2</sub> and FR led to reduced E<sub>L</sub> and G<sub>S</sub> of <italic>L. styraciflua</italic> across soil moisture conditions.</p>
dc.subject Ecology
dc.subject Environmental science
dc.subject Plant biology
dc.subject forest ecology
dc.subject forest models
dc.subject global change
dc.subject hierarchical modeling
dc.subject physiological ecology
dc.subject Pinus taeda
dc.title Improving Models of Forest Carbon and Water Cycling: Revisiting Assumptions and Incorporating Variability
dc.type Dissertation
dc.department Ecology

Files in this item


This item appears in the following Collection(s)

Show simple item record