The exchange of carbon dioxide is a key measure of ecosystem metabolism and a critical intersection
between the terrestrial biosphere and the Earth’s climate. Despite the general agreement that
the terrestrial ecosystems in North America provide a sizeable carbon sink, the size and distribution
of the sink remain uncertain. We...
The eddy-covariance method often underestimates fluxes under stable, low-wind conditions at night when turbulence is not well developed. The most common approach to resolve the problem of nighttime flux underestimation is to identify and remove the deficit periods using friction-velocity (u*) threshold filters (u*[superscript Th]). This study modifies an accepted...
Two distinct nocturnal subcanopy flow regimes are observed beneath a tall (16 m) open pine forest canopy. The first is characterized by weaker mixing, stronger stability, westerly downslope flow decoupled from the flow above the canopy and much smaller than expected ecosystem respiration from the eddy flux plus storage measurements...
The exchange of carbon dioxide is a key measure of ecosystem metabolism and a critical intersection
between the terrestrial biosphere and the Earth’s climate. Despite the general agreement that
the terrestrial ecosystems in North America provide a sizeable carbon sink, the size and distribution
of the sink remain uncertain. We...
Accurate estimates of forest aboveground biomass are needed to reduce uncertainties in the terrestrial carbon flux. The Geoscience Laser Altimeter System (GLAS) onboard the Ice, Cloud and land Elevation Satellite is now the first spaceborne lidar sensor that will provide global estimates of vegetation height. This study investigated the utility...
Vegetation carbon uptake and respiration constitute the largest carbon cycle of the planet with an annual turnover
in the order of 120 GT. Currently, neither ecosystem carbon uptake (through photosynthesis) nor ecosystem
carbon release (through respiration) can be measured directly during the daytime. Instead, flux-tower measurements
rely on nighttime respiration...
Understanding plant photosynthesis, or Gross Primary Production (GPP), is a crucial aspect of quantifying the terrestrial carbon cycle. Remote sensing approaches, in particular multi-angular spectroscopy, have proven successful for studying relationships between canopy-reflectance and plant-physiology processes, thus providing a mechanism to scale up. However, many different instrumentation designs exist and...
High spatiotemporal resolution satellite imagery is useful for natural resource management and monitoring for land-use and land-cover change and ecosystem dynamics. However, acquisitions from a single satellite can be limited, due to trade-offs in either spatial or temporal resolution. The spatial and temporal adaptive reflectance fusion model (STARFM) and the...
Accurate and reliable estimates of gross primary productivity (GPP) are required for monitoring the global carbon cycle at different spatial and temporal scales. Because GPP displays high spatial and temporal variation, remote sensing plays a major role in producing gridded estimates of GPP across spatiotemporal scales. In this context, understanding...