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Savannas and open grasslands often co-exist in semi-arid regions. Questions that remain unanswered and are of interest to biometeorologists include: how do these contrasting landscapes affect the exchanges of energy on seasonal and annual time scales; and, do biophysical constraints imposed by water supply and water demand affect whether the land is(More)
The Moderate Resolution Spectroradiometer (MODIS) sensor has provided near real-time estimates of gross primary production (GPP) since March 2000. We compare four years (2000 to 2003) of satellite-based calculations of GPP with tower eddy CO2 flux-based estimates across diverse land cover types and climate regimes. We examine the potential error(More)
Understanding seasonal changes in photosynthetic parameters and stomatal conductance is crucial for modeling long-term carbon uptake and energy fluxes of ecosystems. Gas exchange measurements of CO2 and light response curves on blue oak leaves (Quercus douglasii H. & A.) were conducted weekly throughout the growing season to study the seasonality of(More)
[1] In this paper, we analyzed 3 years of carbon flux data from continuous eddy covariance measurements to investigate how soil moisture, rain pulses, and growth alter the response of ecosystem respiration to temperature. The data were acquired over an annual grassland and from the grass understory of an oak/grass savanna ecosystem in California. We(More)
This paper describes a new method to monitor continuously soil CO2 profiles using small solid-state CO2 sensors buried at different depths of the soil. Based on the measurement of soil CO2 profile and a gaseous diffusivity model, we estimated soil CO2 efflux, which was mainly from heterotrophic respiration, and its temporal variation in a dry season in a(More)
Most satellites provide, at best, a single daily snapshot of vegetation and, at worst, these snapshots may be separated by periods of many days when the ground was obscured by cloud cover. Since vegetation carbon exchange can be very dynamic on diurnal and day-to-day timescales, the limited temporal resolution of satellite data is a potential limitation in(More)
We recommend an automated statistical method (Moving Point Test, or MPT) to determine the friction velocity (u*) thresholds in nighttime eddy flux filtering. Our intention is to make the determination of the u* thresholds objective and reproducible and to keep flux treatment consistent over time and across sites. In developing the MPT method, we recognize(More)
Np, for NPP Nec, Net ecosystem carbon exchange, as measured by micrometeorologists NB, Net biome productivity Gp, Gross primary productivity Jpmax, maximum flux density of canopy photosynthesis Reco, ecosystem respiration Rplant, plant respiration Rauto, soil autotrophic respiration Rhetero, soil heterotrophic respiration Rsoil, total soil respiration(More)
The eddy covariance method for estimating fluxes of trace gases, energy and momentum in the constant flux layer above a plant canopy fundamentally relies on accurate measurements of the vertical wind speed. This wind speed is typically measured using a three-dimensional ultrasonic anemometer. Previous studies comparing anemometers with orthogonal transducer(More)
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