[1] Combining sap flux and eddy covariance measurements provides a means to study plant stomatal conductance and the relationship between transpiration and photosynthesis. We measured sap flux using Granier-type sensors in a northern hardwood-dominated old growth forest in Michigan, upscaled to canopy transpiration, and calculated canopy conductance. We also measured carbon and water fluxes wit...

Many researchers are using sap flux to estimate tree-level transpiration, and to scale to standand catchment-level transpiration; yet studies evaluating the comparability of sap flux-based estimates of transpiration (Et) with alternative methods for estimating Et at this spatial scale are rare. Our ability to accurately scale from the probe to the tree to the watershed has not yet been demonstr...

Transpiration is generally assumed to be insignificant at night when stomata close in response to the lack of photosynthetically active radiation. However, there is increasing evidence that the stomata of some species remain open at night, which would allow for nighttime transpiration if there were a sufficient environmental driving force. We examined nighttime water use in co-occurring species...

The fluorescent compound trisodium, 3-hydroxy-5,8,10-pyrenetrisulfonate (PTS) was used to quantify the apoplastic flux through red pine (Pinus resinosa Ait.) root systems-that portion of the total water flux reaching the xylem without ever crossing a semipermeable membrane. Flow was induced by pressure through detopped root systems, and by transpiration through intact seedlings. Apoplastic flux...

BACKGROUND AND AIMS In most fruit crops, storage quality varies greatly between regions and seasons, causing significant commercial loss. Understanding the sources of this variability will contribute to the knowledge of fruit developmental physiology and may also benefit commercial fruit production via altered managements that reduce it or forecasts that predict it. A causal-chain relationship ...

Simulations of above-canopy water vapor and CO2 fluxes were calculated by the USGF linked model of canopy gas exchange and subsurface processes for the 1996-1997 winter wheat season at the AmeriFlux Wheat Site, Oklahoma. Soil surface CO2 flux plus canopy gas exchange and transpiration plus soil evaporation modeled the CO2 and water vapor fluxes, respectively. Parameter values for net photosynth...

We investigated the assumption, necessary for comparison between bottom-up scaling of plot level fluxes to top-down scaling of regional models, that small plots of sap flux are representative of the transpiration component of regional land-surface atmosphere water vapor interactions. We conducted sap flux measurements in three stands dominated by sugar maple (Acer saccharum Marsh.) representing...

to diffuisive and turbulent vapor flux in the external air, a similar diffusive resistance which results from the internal leaf geometry, inclusive of the stomlata, and1 parallel to the latter, a resistance to vapor diffusion1 throu-gh the cuticle. In contrast. the last 2 resistances do not exist in the evaporation froml an open water sturface or a moist blotter paper. The resistanice in these ...

[1] Scaling transpiration from trees to larger areas is a fundamental problem in ecohydrology. For scaling stand transpiration from sap flux sensors we asked if plot representativeness depended on plot size and location, the magnitude of environmental drivers, parameter needs for ecosystem models, and whether the goal was to estimate transpiration per unit ground area (EC), per unit leaf area (...

Effect of time dependent normal transpiration on the problem of unsteady viscous flow and heat transfer in the vicinity of an axisymmetric stagnation point of an infinite circular cylinder moving simultaneously with time-depended angular and axial velocities and with time-dependent wall temperature or wall heat flux are investigated. The impinging free stream is steady with a strain rate . A re...