Net Ecosystem Exchange Research Papers (original) (raw)

This study reports the seasonal assessment of energy balance components and carbon dioxides fluxes over a drip irrigated kiwifruit orchard, with a Leaf Area Index (LAI) of 3 at full canopy development. The most remarkable amount of energy... more

This study reports the seasonal assessment of energy balance components and carbon dioxides fluxes over a drip irrigated kiwifruit orchard, with a Leaf Area Index (LAI) of 3 at full canopy development. The most remarkable amount of energy partitioning throughout the whole season was due to latent heat flux that had values approximating to those of sensible heat flux (about

Eddy covariance measurements of CO2 fluxes were conducted in 2004 at the agricultural site of Lonzée, Belgium, over a sugar beet crop. Additional measurements of biomass net primary production and leaf area index (LAI) were carried out.... more

Eddy covariance measurements of CO2 fluxes were conducted in 2004 at the agricultural site of Lonzée, Belgium, over a sugar beet crop. Additional measurements of biomass net primary production and leaf area index (LAI) were carried out. The response of the fluxes to climatic and non-climatic variables was analysed. Nighttime fluxes were dependent on turbulence, temperature and high soil water

We analysed 6 years (1997–2002) of continuous eddy covariance CO2 fluxes over a mixed temperate forest in the Belgian Campine region and present the long-term mean seasonal changes in net ecosystem exchange (NEE), gross primary production... more

We analysed 6 years (1997–2002) of continuous eddy covariance CO2 fluxes over a mixed temperate forest in the Belgian Campine region and present the long-term mean seasonal changes in net ecosystem exchange (NEE), gross primary production (GPP) and total ecosystem respiration (RE). Seasonal changes in NEE, GPP and RE were tightly correlated, with extremes in July and December/January. Nonetheless, maximum rates of RE slightly lagged behind the maximum rates of GPP. We observed a substantial increase in NEE at optimum light conditions (reduced uptake) above 24 °C. Because this increase is unlikely to be related only to the increase in RE, we hypothesize that it also indicates a significant decrease in GPP under dry and warm meteorological conditions. Because this increase in NEE was better correlated with atmospheric vapour pressure deficit than with temperature, we further hypothesize that the observed change in NEE was predominantly related to the effect of high atmospheric evapora...

Urbanisation is increasing tremendously in some parts of the world. Consequently, many rural forests may become depleted, although many opportunities exist for urban forests to increase. However, few studies have quantified the carbon (C)... more

Urbanisation is increasing tremendously in some parts of the world. Consequently, many rural forests may become depleted, although many opportunities exist for urban forests to increase. However, few studies have quantified the carbon (C) sequestration capacities of urban and rural forests in specific climatic zones. The present study compared carbon sequestration in two temperate deciduous forests located in Nagoya and

Turf grasses are ubiquitous in the urban landscape of the United States and are often associated with various types of environmental impacts, especially on water resources, yet there have been limited efforts to quantify their total... more

Turf grasses are ubiquitous in the urban landscape of the United States and are often associated with various types of environmental impacts, especially on water resources, yet there have been limited efforts to quantify their total surface and ecosystem functioning, such as their total impact on the continental water budget and potential net ecosystem exchange (NEE). In this study, relating turf grass area to an estimate of fractional impervious surface area, it was calculated that potentially 163,800 km2 (± 35,850 km2) of land are cultivated with turf grasses in the continental United States, an area three times larger than that of any irrigated crop. Using the Biome-BGC ecosystem process model, the growth of warm-season and cool-season turf grasses was modeled at a number of sites across the 48 conterminous states under different management scenarios, simulating potential carbon and water fluxes as if the entire turf surface was to be managed like a well-maintained lawn. The results indicate that well-watered and fertilized turf grasses act as a carbon sink. The potential NEE that could derive from the total surface potentially under turf (up to 17 Tg C/yr with the simulated scenarios) would require up to 695 to 900 liters of water per person per day, depending on the modeled water irrigation practices, suggesting that outdoor water conservation practices such as xeriscaping and irrigation with recycled waste-water may need to be extended as many municipalities continue to face increasing pressures on freshwater.

We developed an individual-based stochastic-empirical model to simulate the carbon dynamics of live and dead trees in a Central Amazon forest near Manaus, Brazil. The model is based on analyses of extensive field studies carried out on... more

We developed an individual-based stochastic-empirical model to simulate the carbon dynamics of live and dead trees in a Central Amazon forest near Manaus, Brazil. The model is based on analyses of extensive field studies carried out on permanent forest inventory plots, and syntheses of published studies. New analyses included: (1) growth suppression of small trees, (2) maximum size (trunk base diameter) for 220 tree species, (3) the relationship between growth rate and wood density, and (4) the growth response of surviving trees to catastrophic mortality (from logging). The model simulates a forest inventory plot, and tracks recruitment, growth, and mortality of live trees, decomposition of dead trees (coarse litter), and how these processes vary with changing environmental conditions. Model predictions were tested against aggregated field data, and also compared with independent measurements including maximum tree age and coarse litter standing stocks. Spatial analyses demonstrated that a plot size of ~10 ha was required to accurately measure wood (live and dead) carbon balance. With the model accurately predicting relevant pools and fluxes, a number of model experiments were performed to predict forest carbon balance response to perturbations including: (1) increased productivity due to CO2 fertilization, (2) a single semi-catastrophic (10%) mortality event, (3) increased recruitment and mortality (turnover) rates, and (4) the combined effects of increased turnover, increased tree growth rates, and decreased mean wood density of new recruits. Results demonstrated that carbon accumulation over the past few decades observed on tropical forest inventory plots (~0.5 Mg C ha−1 year−1) is not likely caused by CO2 fertilization. A maximum 25% increase in woody tissue productivity with a doubling of atmospheric CO2 only resulted in an accumulation rate of 0.05 Mg C ha−1 year−1 for the period 1980–2020 for a Central Amazon forest, or an order of magnitude less than observed on the inventory plots. In contrast, model parameterization based on extensive data from a logging experiment demonstrated a rapid increase in tree growth following disturbance, which could be misinterpreted as carbon sequestration if changes in coarse litter stocks were not considered. Combined results demonstrated that predictions of changes in forest carbon balance during the twenty-first century are highly dependent on assumptions of tree response to various perturbations, and underscores the importance of a close coupling of model and field investigations.

We report on net ecosystem production (NEP) and key environmental controls on net ecosystem exchange (NEE) of carbon dioxide (CO2) between a mangrove forest and the atmosphere in the coastal Florida Everglades. An eddy covariance system... more

We report on net ecosystem production (NEP) and key environmental controls on net ecosystem exchange (NEE) of carbon dioxide (CO2) between a mangrove forest and the atmosphere in the coastal Florida Everglades. An eddy covariance system deployed above the canopy was used to determine NEE during January 2004 through August 2005. Maximum daytime NEE ranged from −20 to −25 μmol

Land surface phenology (LSP) is a key indicator of ecosystem dynamics under a changing environment. Over the last few decades, numerous studies have used the time series data of vegetation indices derived from land surface reflectance... more

Land surface phenology (LSP) is a key indicator of ecosystem dynamics under a changing environment. Over the last few decades, numerous studies have used the time series data of vegetation indices derived from land surface reflectance acquired by satellite-based optical sensors to delineate land surface phenology. Recent progress and data accumulation from CO 2 eddy flux towers offers a new

To determine factors controlling the carbon dynamics of an intensively man-aged landscape, we measured net CO 2 exchange with the atmosphere using eddy covariance and soil CO 2 fluxes using static chambers along a chronosequence of slash... more

To determine factors controlling the carbon dynamics of an intensively man-aged landscape, we measured net CO 2 exchange with the atmosphere using eddy covariance and soil CO 2 fluxes using static chambers along a chronosequence of slash pine (Pinus elliottii var. elliottii) plantations consisting of a recent clearcut, a mid-rotation (10-yr-old) stand, and a rotation-aged (24-yr-old) stand. Daytime net ecosystem exchange of CO 2 (NEE day) at the clearcut was not significantly different than zero during the growing season of the first year following harvest and reached levels that were 40% of those at the older stands during the second growing season. NEE day was similar at the mid-rotation and ro-tation-aged sites, reflecting the similar leaf areas of these stands. Nighttime net ecosystem exchange of CO 2 (NEE night) was an exponential function of air or soil temperature at all sites. However, low decomposition rates of litter and flooding of the site following harvest likely constr...

Peatlands may play an important role in global carbon cycles, and thus developing better estimates of carbon exchange in those ecosystems has become a main concern. In this study, the relationship between spectral indices and CO2 fluxes... more

Peatlands may play an important role in global carbon cycles, and thus developing better estimates of carbon exchange in those ecosystems has become a main concern. In this study, the relationship between spectral indices and CO2 fluxes was tested for different communities in a Sphagnum-dominated peatland. Fluxes were measured with a portable climate- controlled chamber while reflectance was simultaneously recorded

Eddy covariance (EC) estimates of carbon dioxide (CO2) fluxes and energy balance are examined to investigate the functional responses of a mature mangrove forest to a disturbance generated by Hurricane Wilma on October 24, 2005 in the... more

Eddy covariance (EC) estimates of carbon dioxide (CO2) fluxes and energy balance are examined to investigate the functional responses of a mature mangrove forest to a disturbance generated by Hurricane Wilma on October 24, 2005 in the Florida Everglades. At the EC site, high winds from the hurricane caused nearly 100% defoliation in the upper canopy and widespread tree mortality.

Carbon sequestration in forests is of great interest due to concerns about global climate change. Carbon storage rates depend on ecosystem fluxes (photosynthesis and ecosystem respiration), typically quantified as net ecosystem exchange... more

Carbon sequestration in forests is of great interest due to concerns about global climate change. Carbon storage rates depend on ecosystem fluxes (photosynthesis and ecosystem respiration), typically quantified as net ecosystem exchange (NEE). Methods to estimate forest NEE without intensive site sampling are needed to accurately assess rates of carbon sequestration at stand-level and larger scales. We produced spatially-explicit estimates of NEE for 9 770 ha of slash pine (Pinus elliottii) plantations in North-Central Florida for a single year by coupling remote sensing-based estimates of leaf area index (LAI) with a process-based growth simulation model. LAI estimates produced from a neural-network modeling of ground plot and Landsat TM satellite data had a mean of 1.06 (range 0–3.93, including forest edges). Using the neural network LAI values as inputs, the slash pine simulation model (SPM2) estimates of NEE ranged from −5.52 to 11.06 Mg·ha−1·a−1 with a mean of 3.47 Mg·ha−1·a−1. Total carbon storage for the year was 33 920 t, or about 3.5 tons per hectare. Both estimated LAI and NEE were highly sensitive to fertilization.