Forests play a crucial role in the global carbon (C) cycle by storing and sequestering a substantial amount of C in the terrestrial biosphere. Due to temporal dynamics in climate and vegetation activity, there are significant regional variations in carbon dioxide (CO2) fluxes between the biosphere and atmosphere in forests...
Forests dominate carbon (C) exchanges between the terrestrial biosphere and the atmosphere on land. In the long term, the net carbon flux between forests and the atmosphere has been significantly impacted by changes in forest cover area and structure due to ecological disturbances and management activities. Current empirical approaches for...
We sought to improve net ecosystem exchange (NEE) estimates for a tall, dense, mature Douglas-Fir forest in the Oregon Coast range characterized by weak flows, systematic wind directional shear, and limited turbulent mixing throughout the diurnal period. We used eddy covariance (EC) observations at two levels and concurrent biological measurements...
We present an atmospheric inverse modeling framework to constrain terrestrial biosphere CO₂ exchange processes at subregional scales. The model is operated at very high spatial and temporal resolution, using the state of Oregon in the northwestern United States as the model domain. The modeling framework includes mesoscale atmospheric simulations coupled...
This paper examines albedo perturbation and radiative forcing after a high-severity fire in a
mature forest in the Oregon Cascade Range. Correlations between postfire albedo and seedling, sapling,
and snag (standing dead tree) density were investigated across fire severity classes and seasons for years
4-15 after fire. Albedo perturbation was...
This paper examines albedo perturbation and radiative forcing after a high-severity fire in a
mature forest in the Oregon Cascade Range. Correlations between postfire albedo and seedling, sapling,
and snag (standing dead tree) density were investigated across fire severity classes and seasons for years
4-15 after fire. Albedo perturbation was...
Worldwide measurements of nearly 130C3 species covering all
major plant functional types are analysed in conjunction with
model simulations to determine the effects of mesophyll
conductance (gm) on photosynthetic parameters and their
relationships estimated from A/Ci curves. We find that an
assumption of infinite gm results in up to 75%...
Worldwide measurements of nearly 130C3 species covering all
major plant functional types are analysed in conjunction with
model simulations to determine the effects of mesophyll
conductance (gm) on photosynthetic parameters and their
relationships estimated from A/Ci curves. We find that an
assumption of infinite gm results in up to 75%...
The global terrestrial carbon sink offsets one-third of the world’s fossil fuel emissions, but the strength of this sink is highly sensitive to large-scale extreme events. In 2012, the contiguous United States experienced exceptionally warm temperatures and the most severe drought since the Dust Bowl era of the 1930s, resulting...
The global terrestrial carbon sink offsets one-third of the world’s fossil fuel emissions, but the strength of this sink is highly sensitive to large-scale extreme events. In 2012, the contiguous United States experienced exceptionally warm temperatures and the most severe drought since the Dust Bowl era of the 1930s, resulting...
The global terrestrial carbon sink offsets one-third of the world’s fossil fuel emissions, but the strength of this sink is highly sensitive to large-scale extreme events. In 2012, the contiguous United States experienced exceptionally warm temperatures and the most severe drought since the Dust Bowl era of the 1930s, resulting...
This study quantifies the short-term effects of low-, moderate-, and high-severity fire on carbon pools and fluxes in the Eastern Cascades of Oregon. We surveyed 64 forest stands across four fires that burned 41,000 ha (35%) of the Metolius Watershed in 2002 and 2003, stratifying the landscape by burn severity...
The reliable simulation of gross primary productivity (GPP) at various spatial and temporal scales is of significance to quantifying the net exchange of carbon between terrestrial ecosystems and the atmosphere. This study aimed to verify the ability of a nonlinear two-leaf model (TL-LUEn), a linear two-leaf model (TL-LUE), and a...
This paper examines albedo perturbation and radiative forcing after a high-severity fire in a
mature forest in the Oregon Cascade Range. Correlations between postfire albedo and seedling, sapling,
and snag (standing dead tree) density were investigated across fire severity classes and seasons for years
4-15 after fire. Albedo perturbation was...
In recent years, measurements of atmospheric carbon dioxide with high precision and accuracy have become increasingly important for climate change research, in particular to inform terrestrial biosphere models. Anthropogenic carbon dioxide emissions from fossil fuel burning have long been recognized to contribute a significant portion of the carbon dioxide in...
Worldwide measurements of nearly 130C3 species covering all major plant functional types are analysed in conjunction with model simulations to determine the effects of mesophyll conductance (gm) on photosynthetic parameters and their relationships estimated from A/Ci curves. We find that an assumption of infinite gm results in up to 75%...
Background: Management strategies have been proposed to minimise the effects of climate
change on forest resilience.
Aims: We investigated the Pacific Northwest US region forest carbon balance under current
practices, and changes that may result from management practices proposed for the region’s
34 million ha of forests to mitigate climate...
It is well established that individual organisms can acclimate and adapt to temperature to optimize their functioning. However, thermal optimization of ecosystems, as an assemblage of organisms, has not been examined at broad spatial and temporal scales. Here, we compiled data from 169 globally distributed sites of eddy covariance and...
The regular monitoring of evapotranspiration from satellites has been limited because of discontinuous temporal coverage, resulting in snapshots at a particular point in space and time. We developed a temporal upscaling scheme using satellite-derived instantaneous estimates of evapotranspiration to produce a daily-sum evapotranspiration averaged over an 8-day interval. We tested...
Terrestrial ecosystem-atmosphere exchange of carbon, water vapor, and energy has been measured for over a decade at many sites globally. To minimize measurement and analysis errors, quality assurance data have been collected over short periods along-side tower instruments at AmeriFlux research sites. Theoretical and empirical error and uncertainty values have...
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...
We propose the Breathing Earth System Simulator (BESS), an upscaling approach to quantify global gross primary productivity and evapotranspiration using MODIS with a spatial resolution of 1-5 km and a temporal resolution of 8 days. This effort is novel because it is the first system that harmonizes and utilizes MODIS...
Fossil fuel emissions aside, temperate North America is a net sink of carbon dioxide at present¹⁻³. Year-to-year variations in this carbon sink are linked to variations in hydroclimate that affect net ecosystem productivity³,⁴. The severity and incidence of climatic extremes, including drought, have increased as a result of climate warming⁵⁻⁸....
Surface albedo is a key parameter in the Earth's energy balance since it affects the amount of solar radiation directly absorbed at the planet surface. Its variability in time and space can be globally retrieved through the use of remote sensing products. To evaluate and improve the quality of satellite...
To guide the future development of CO₂-atmospheric inversion modeling systems, we analyzed the errors arising from prior information about terrestrial ecosystem fluxes. We compared the surface fluxes calculated by a process-based terrestrial ecosystem model with daily averages of CO₂ flux measurements at 156 sites across the world in the FLUXNET...
Five years of eddy-covariance and other measurements at a mature ponderosa pine forest and a nearby young plantation are used to contrast the carbon fluxes for long-term averages, seasonal patterns, diel patterns and interannual variability, and to examine the differing responses to water-stress. The mature forest with larger leaf area...
We present an inverse modeling framework designed to constrain CO2 budgets at regional scales. The approach captures atmospheric transport processes in high spatiotemporal resolution by coupling a mesoscale model with Lagrangian Stochastic backward trajectories. Terrestrial biosphere CO₂ emissions are generated through a simple diagnostic flux model that splits the net...
Carbon sequestration is increasingly recognized as an ecosystem service, and forest management has a large potential to alter regional carbon fluxes − notably by way of harvest removals and related impacts on net ecosystem production (NEP). In the Pacific Northwest region of the U.S.,
the implementation of the Northwest Forest...
We analyzed 7 years (2002–2008) of micrometeorological and concurrent biological
observations of carbon and water fluxes at a mature ponderosa pine forest in central
Oregon in a semiarid climate. We sought to evaluate the extent that gross primary
productivity, net ecosystem exchange, ecosystem respiration, net primary productivity, net
ecosystem productivity,...
Remote sensing of variables necessary to estimate net primary
production of vegetation over large temporal and spatial scales has been a
goal of climate change research. This thesis consists of two studies that
address the reliability of satellite and airborne sensors to quantify a basic
component of all production models,...