Stem respiration and carbon dioxide efflux of young Populus deltoides trees in relation to temperature and xylem carbon dioxide concentration.

Oxidative respiration is strongly temperature driven. However, in woody stems, efflux of CO(2) to the atmosphere (E (A)), commonly used to estimate the rate of respiration (R (S)), and stem temperature (T (st)) have often been poorly correlated, which we hypothesized was due to transport of respired CO(2) in xylem sap, especially under high rates of sap flow (f (s)). To test this, we measured E (A), T (st), f (s) and xylem sap CO(2) concentrations ([CO(2)*]) in 3-year-old Populus deltoides trees under different weather conditions (sunny and rainy days) in autumn.

Stored water use and transpiration in Scots pine: a modeling analysis with ANAFORE.

We estimated daily use of stored water by Scots pine (Pinus sylvestris L.) trees growing in a temperate climate with the ANAFORE model (ANAlysis of FORest Ecosystems) and compared the simulation results with sap flow measurements. The original model was expanded with a dynamic water flow and storage model that simulates sap flow dynamics in an individual tree.

Resistance to radial CO diffusion contributes to between-tree variation in CO efflux of Populus deltoides stems.

Rates of CO efflux of stems and branches are highly variable among and within trees and across stands. Scaling factors have only partially succeeded in accounting for the observed variations. In this study, the resistance to radial CO diffusion was quantified for tree stems of an eastern cottonwood (Populus deltoides Bartr.

Temporal variation and high-resolution spatial heterogeneity in soil CO2 efflux in a short-rotation tree plantation.

Soil CO2 efflux (SR) is the second largest carbon flux on earth. We investigated the driving factors of the seasonal change and short-distance spatial variation in SR in a short-rotation plantation of willow (Salix viminalis Orm). Total annual SR ranged from 723 to 1149 g Cm(-2) year(-1).

Drought and the diurnal patterns of stem CO2 efflux and xylem CO2 concentration in young oak (Quercus robur).

A young potted oak (Quercus robur L.) tree was subjected to drought by interrupting the water supply for 9 days. The tree was placed in a growth chamber in which daily patterns of temperature and radiation were constant.

Daytime depression in tree stem CO2 efflux rates: is it caused by low stem turgor pressure?

Background And Aims: Daytime CO2 efflux rates (FCO2) from tree stems are often reported to be lower than expected from the exponential relationship between temperature and respiration. Explanations of daytime depression in FCO2 have focused on the possible role of internal CO2 transport in the xylem. However, another possible cause that has been overlooked is the daily dynamics of the water status in the living stem tissues and its influence on stem growth rate and thus respiration.

Effects of ring-porous and diffuse-porous stem wood anatomy on the hydraulic parameters used in a water flow and storage model.

Calibration of a recently developed water flow and storage model based on experimental data for a young diffuse-porous beech tree (Fagus sylvatica L.) and a young ring-porous oak tree (Quercus robur L.) revealed that differences in stem wood anatomy between species strongly affect the calibrated values of the hydraulic model parameters.

Parameter sensitivity and uncertainty of the forest carbon flux model FORUG: a Monte Carlo analysis.

The Monte Carlo technique can be used to propagate input variable uncertainty and parameter uncertainty through a model to determine output uncertainty. However, to carry out Monte Carlo simulations, the uncertainty distributions or the probability density functions (PDFs) of the model parameters and input variables must be known. This remains one of the bottlenecks in current uncertainty research in forest carbon flux modeling.

Stomatal oscillations in orange trees under natural climatic conditions.

Background And Aims: Stomatal oscillations have been reported in many plant species, but they are usually induced by sudden step changes in the environment when plants are grown under constant conditions. This study shows that in navel orange trees (Citrus sinensis) pronounced stomatal oscillations occur and persist under natural climatic conditions.

Methods: Oscillations in stomatal conductance were measured, and related to simultaneous measurements of leaf water potential, and flow rate of sap in the stems of young, potted plants.

A mathematical model linking tree sap flow dynamics to daily stem diameter fluctuations and radial stem growth.

To date, models for simulating sap flow dynamics in individual trees with a direct link to stem diameter variation include only the diameter fluctuation driven by a change in stem water storage. This paper reports results obtained with a comprehensive flow and storage model using whole-tree leaf transpiration as the only input variable. The model includes radial stem growth based on Lockhart's equation for irreversible cell expansion.

Unravelling the relationship between stem temperature and air temperature to correct for errors in sap-flow calculations using stem heat balance sensors.

Results from measurement of sap flow by heat balance sensors on the stem of a young oak tree (Quercus robur L.) revealed that thermal disequilibrium (i.e.

Use of X-ray computed microtomography for non-invasive determination of wood anatomical characteristics.

Quantitative analysis of wood anatomical characteristics is usually performed using classical microtomy yielding optical micrographs of stained thin sections. It is time-consuming to obtain high quality cross-sections from microtomy, and sections can be damaged. This approach, therefore, is often impractical for those who need quick acquisition of quantitative data on vessel characteristics in wood.

An experimental system for analysis of the dynamic sap-flow characteristics in young trees: results of a beech tree.

This paper describes an experimental system designed for analysis of the dynamic water flow through young trees, complemented with test results of a 2-year-old beech tree (Fagus sylvatica L.). The system allows automatic and simultaneous measurements of a complex set of plant physiological processes at leaf, branch, stem and root levels [transpiration (E), sap flow (F) and diameter fluctuations (Δd)], in combination with the micrometeorological variables that control these processes [soil and air temperature (T and T), vapour pressure deficit of the air (D) and photosynthetically active radiation (PAR)].