A5010489381- Atmospheric and Environmental Gas Dynamics
- Plant Water Relations and Carbon Dynamics
- Atmospheric chemistry and aerosols
- Climate variability and models
- Plant responses to elevated CO2
- Atmospheric Ozone and Climate
- Environmental and Agricultural Sciences
- Pasture and Agricultural Systems
- Air Quality and Health Impacts
- Remote Sensing in Agriculture
- Fire effects on ecosystems
- Air Quality Monitoring and Forecasting
- Forest ecology and management
- Cryospheric studies and observations
- Atmospheric aerosols and clouds
- Vehicle emissions and performance
- Tree-ring climate responses
- Climate change and permafrost
- Meteorological Phenomena and Simulations
- Remote Sensing and LiDAR Applications
- Forest, Soil, and Plant Ecology in China
- Peatlands and Wetlands Ecology
- Forest Management and Policy
- Species Distribution and Climate Change
- Ecology and Vegetation Dynamics Studies
Planetary Science Institute
2015-2024
Harvard University
2015-2024
Harvard University Press
2012-2024
Northwestern University
2018
Northrop Grumman (Germany)
2016
Tsinghua University
2010
State Key Joint Laboratory of Environment Simulation and Pollution Control
2010
University of California, Davis
2005
University of New Hampshire
1995-2003
University of California, Irvine
1997-2003
FLUXNET is a global network of micrometeorological flux measurement sites that measure the exchanges carbon dioxide, water vapor, and energy between biosphere atmosphere. At present over 140 are operating on long-term continuous basis. Vegetation under study includes temperate conifer broadleaved (deciduous evergreen) forests, tropical boreal crops, grasslands, chaparral, wetlands, tundra. Sites exist five continents their latitudinal distribution ranges from 70°N to 30°S. has several...
Abstract The turbulent exchanges of CO 2 and water vapour between an aggrading deciduous forest in the north‐eastern United States (Harvard Forest) atmosphere were measured from 1990 to 1994 using eddy covariance technique. We present a detailed description methods used rigorous evaluation precision accuracy these measurements. partition sources error into three categories: (1) uniform systematic errors are constant independent measurement conditions (2) selective result when exchange varies...
Abstract Terrestrial ecosystems sequester 2.1 Pg of atmospheric carbon annually. A large amount the terrestrial sink is realized by forests. However, considerable uncertainties remain regarding fate this over both short and long timescales. Relevant data to address these are being collected at many sites around world, but syntheses still sparse. To facilitate future synthesis activities, we have assembled a comprehensive global database for forest ecosystems, which includes budget variables...
The eddy correlation method was used to measure the net ecosystem exchange of carbon dioxide continuously from April 1990 December 1991 in a deciduous forest central Massachusetts. annual uptake 3.7 +/- 0.7 metric tons per hectare year. Ecosystem respiration, calculated relation between nighttime and soil temperature, 7.4 year, implying gross production 11.1 observed rate accumulation reflects recovery agricultural development 1800s. Carbon rates were notably larger than those assumed for...
We use eddy covariance measurements of net ecosystem productivity (NEP) from 21 FLUXNET sites (153 site-years data) to investigate relationships between phenology and (in terms both NEP gross photosynthesis, GEP) in temperate boreal forests. Results are used evaluate the plausibility four different conceptual models. Phenological indicators were derived time series, remote sensing examine spatial patterns (across sites) temporal years); an important conclusion is that it likely neither these...
We used eddy covariance; gas-exchange chambers; radiocarbon analysis; wood, moss, and soil inventories; laboratory incubations to measure the carbon balance of a 120-year-old black spruce forest in Manitoba, Canada. The site lost 0.3 ± 0.5 metric ton per hectare year (ton C ha −1 ) from 1994 1997, with gain 0.6 0.2 moss wood offset by loss 0.8 soil. remained frozen most year, decomposition organic matter increased 10-fold upon thawing. stability pool (∼150 tons appears sensitive depth...
The net ecosystem exchange of carbon dioxide was measured by eddy covariance methods for 3 years in two old-growth forest sites near Santarém, Brazil. Carbon lost the wet season and gained dry season, which opposite to seasonal cycles both tree growth model predictions. 3-year average loss 1.3 (confidence interval: 0.0 2.0) megagrams per hectare year. Biometric observations confirmed but imply that it is a transient effect recent disturbance superimposed on long-term balance. Given episodic...
The annual net uptake of CO 2 by a deciduous forest in New England varied from 1.4 to 2.8 metric tons carbon per hectare between 1991 and 1995. Carbon sequestration was higher than average because increased photosynthesis 1995 decreased respiration. Interannual shifts were associated with the timing leaf expansion senescence. Shifts respiration anomalies soil temperature, deep snow winter, drought summer. If this ecosystem is typical northern biomes, interannual climate variations on...
Abstract Phenology, by controlling the seasonal activity of vegetation on land surface, plays a fundamental role in regulating photosynthesis and other ecosystem processes, as well competitive interactions feedbacks to climate system. We conducted an analysis evaluate representation phenology, associated seasonality ecosystem‐scale CO 2 exchange, 14 models participating N orth A merican C arbon P rogram S ite ynthesis. Model predictions were evaluated using long‐term measurements...
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) satellite-based calculations GPP with tower eddy CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> flux-based across diverse land cover types and climate regimes. examine the potential error contributions from meteorology, leaf area index (LAI)/fPAR,...
Volcanic aerosols from the 1991 Mount Pinatubo eruption greatly increased diffuse radiation worldwide for following 2 years. We estimated that this increase in alone enhanced noontime photosynthesis of a deciduous forest by 23% 1992 and 8% 1993 under cloudless conditions. This finding indicates aerosol-induced volcano terrestrial carbon sink contributed to temporary decline growth rate atmospheric dioxide after eruption.
Net uptake of carbon dioxide (CO 2 ) measured by eddy covariance in a 60- to 80-year-old forest averaged 2.0 ± 0.4 megagrams per hectare year during 1993 2000, with interannual variations exceeding 50%. Biometry indicated storage 1.6 over 8 years, 60% live biomass and the balance coarse woody debris soils, confirming eddy-covariance results. Weather seasonal climate (e.g., growing-season length or cloudiness) regulated fluctuations uptake. Legacies prior disturbance management, especially...
We analyzed 13 years (1992−2004) of CO 2 flux data, biometry, and meteorology from a mixed deciduous forest in central Massachusetts. Annual net uptake ranged 1.0 to 4.7 Mg‐C ha −1 yr , with an average 2.5 . Uptake rates increased systematically, nearly doubling over the period despite age 75–110 years; there were parallel increases midsummer photosynthetic capacity at high light level (21.5−31.5 μ mole m −2 s ), woody biomass (101−115 1993−2005, mostly due growth one species, red oak), peak...
Insights into how terrestrial ecosystems affect the Earth's response to changes in climate and rising atmospheric CO 2 levels rely heavily on predictions of biosphere models (TBMs). These contain detailed mechanistic representations biological processes affecting ecosystems; however, their ability simultaneously predict field‐based measurements vegetation dynamics carbon fluxes has remained largely untested. In this study, we address issue by developing a constrained implementation new...
ABSTRACT Our objective is to describe a multi‐layer model of C 3 ‐canopy processes that effectively simulates hourly CO 2 and latent energy ( LE ) fluxes in mixed deciduous Quercus‐Acer (oak–maple) stand central Massachusetts, USA. The key hypothesis governing the biological component stomatal conductance g s varied so daily carbon uptake per unit foliar nitrogen maximized within limitations canopy water availability. hydraulic system modelled as an analogue simple electrical circuits...
Abstract Previous studies have suggested that solar‐induced chlorophyll fluorescence (SIF) is correlated with Gross Primary Production (GPP). However, it remains unclear to what extent this relationship due absorbed photosynthetically active radiation (APAR) and/or light use efficiency (LUE). Here we present the first time series of near‐surface measurement canopy‐scale SIF at 760 nm in temperate deciduous forests. GPP estimated eddy covariance diurnal and seasonal scales ( r 2 = 0.82 0.73,...