Search

Surface-layer parameterizations for heat, mass, momentum, and turbulence exchange are a critical component of the land surface models (LSMs) used in weather prediction and climate models. Although formulations derived from Monin–Obukhov similarity theory (MOST) have long been used, bulk Richardson (Rib) parameterizations have recently been suggested as a MOST alternative but have been evaluated over a limited number of land-cover and climate types. Examining the parameterizations' applicability over other regions, particularly drylands that cover approximately 41% of terrestrial land surfaces, is a critical step toward implementing the parameterizations into LSMs. One year (1 January–31 December 2018) of eddy covariance measurements from a 10-m tower in southeastern Arizona and a 200-m tower in western Texas were used to determine how well the Rib parameterizations for friction velocity ( u * ), sensible heat flux (H), and turbulent kinetic energy (TKE) compare against MOST-derived parameterizations of these quantities. Independent of stability, wind speed regime, and season, the Rib u * and TKE parameterizations performed better than the MOST parameterizations, whereas MOST better represented H. Observations from the 200-m tower indicated that the parameterizations' performance degraded as a function of height above ground. Overall, the Rib parameterizations revealed promising results, confirming better performance than traditional MOST relationships for kinematic (i.e., u * ) and turbulence (i.e., TKE) quantities, although caution is needed when applying the RibH parameterizations to drylands. These findings represent an important milestone for the applicability of Rib parameterizations, given the large fraction of Earth's surface covered by drylands. Significance Statement: Weather forecasting models rely upon complex mathematical relationships to predict temperature, wind, and moisture. Monin–Obukhov similarity theory (MOST) has long been used to forecast these quantities near the land surface, even though MOST's limitations are well known in the scientific community. Researchers have suggested an alternative to MOST called the bulk Richardson (Rib) approach. To allow for the Rib approach to be used in weather forecasting models, the approach needs to be tested over different land-cover and climate types. In this study, we applied the Rib approach to dry areas of the United States and found that the approach better represented turbulence variables than MOST relationships. These findings are an important step toward using Rib relationships in weather forecasting models. [ABSTRACT FROM AUTHOR]

Narragansett Bay, the largest estuary in New England, is a heavily urbanized watershed impacted by deposition and runoff. Nutrient budgets and local policy rely on deposition data from a 1990 study that did not include any direct observations of dry deposition of gaseous ammonia (NH3(g)) and particulate ammonium (p‐NH4+) due to uncertainties in their flux direction and measurement difficulty. Recent work has shown that wet deposition of ammonium (NH4+) to the Bay has increased by a factor of 6 over the past three decades, leading to a 2.5‐fold increase in wet nitrogen (N) deposition. This documented increase in wet deposition of NH4+ is concurrent with managed nutrient reductions in urbanized estuaries but has potentially increased the impacts of atmospheric N deposition, including the dry deposition of NH3(g) and p‐NH4+. However, the lack of NH3(g) and p‐NH4+ measurements hinders our interpretation of this important N source. For the first time over Narragansett Bay, and to our knowledge over open water, dry (particulate and gas phase) total ammonia (NHx = NH3(g) + p‐NH4+) and the bidirectional NH3(g) flux were quantified using a relaxed eddy accumulation sampling technique. We find that dry deposition of NHx comprises 9.6% of total (wet + dry) N deposition. During the fall season, the dominant flux direction for NH3(g) is upward, which also has implications for urban air quality. We estimate that NH3(g) emitted from the Bay to the atmosphere makes up to 10% of the local NH3(g) emission budget for fall. Plain Language Summary: Estuaries around the world receive nitrogen from various sources, including from the atmosphere through rainfall (wet deposition) and gasses and particulates (dry deposition). Such is the case in Narragansett Bay, RI, where a scarcity of measurements hinders our understanding of how atmospheric nitrogen influences this system. Recent work has shown that wet deposition has increased by 2.5‐fold since 1990, driven by a 6‐fold increase in ammonium wet deposition. Gaseous ammonia is subjected to few emission regulations and is poorly understood because gaseous ammonia can flux upward and downward (bi‐directional). For the first time over Narragansett Bay, and to our knowledge over open water, dry deposition of total ammonia (gaseous ammonia + particulate ammonium) and the gaseous ammonia flux were quantified using a technique called relaxed eddy accumulation. We found that dry deposition of total ammonia made up 9.6% of total nitrogen deposition. The dominant flux direction of gaseous ammonia was upward (i.e., out of the water) during the fall season. Loss of nitrogen from the Bay to the atmosphere has implications for urban air quality. We estimated that gaseous ammonia emitted from the Bay to the atmosphere makes up to 10% of the local gaseous ammonia emission budget. Key Points: Dry deposition of gaseous ammonia and particulate ammonium comprises 9.6% of total nitrogen entering Narragansett Bay from the atmosphereThe dominant flux of gaseous ammonia is upward (out of the water) during the fall season when surface water concentrations are elevatedAmmonia released from Narragansett Bay to the atmosphere makes up to 10% of the local gaseous ammonia emission budget [ABSTRACT FROM AUTHOR]

Measurements of atmospheric ammonia (NH3) concentrations and fluxes are limited in coastal regions in the eastern U.S. In this study, continuous and high temporal resolution measurements (5s) of atmospheric NH3 concentrations were recorded using a cavity ring‐down spectrometer in a temperate tidal salt marsh at the St Jones Reserve (Dover, DE). Micrometeorological variables were measured using an eddy covariance system which is part of the AmeriFlux network (US‐StJ). Soil, plant, and water chemistry were also analyzed to characterize the sources and sinks of atmospheric NH3. A new analytical methodology was used to estimate the average ecosystem‐scale diurnal cycle of NH3 fluxes by replicating the characteristics of a chamber experiment. This virtual chamber approach estimates positive surface fluxes in continuing strongly stable conditions when mixing with the air above is minimal. Our findings show that tidal water level may have a significant impact on NH3 emissions from the marsh. The largest fluxes were observed at low tide when more soil was exposed. While it is expected that NH3 fluxes will peak when the air temperature maximizes, high tide occurred concurrently with midday peaks in solar irradiance led to a decrease in NH3 fluxes. Furthermore, soil, plant, and water chemistry measurements underpinning the NH3 concentrations and fluxes lead us to conclude that this coastal wetland ecosystem can act as either a sink or a source of NH3. Such measurements provide novel data on which we can base reliable parameterizations to simulate NH3 emissions from coastal salt marsh ecosystems using surface‐atmosphere transfer models. Plain Language Summary: Coastal wetlands such as salt marshes, mangroves, and seagrasses provide a natural environment for the sequestration and long‐term storage of carbon dioxide (CO2) from the atmosphere. As a fertilizer, nitrogen (N) increases the vegetative growth and thus more CO2 may be fixed in plants as biomass representing the short‐term storage pool of carbon, therefore reducing its atmospheric level. Salt marshes, in particular, have been identified as being highly effective at carbon sequestration as well as adsorbing and transforming N. However, there are limited atmospheric measurements of ammonia (NH3) concentrations and exchanges in coastal areas of the Eastern and Mid‐Atlantic U.S. This pilot study represents one of the few atmospheric measurements of NH3 over temperate tidal salt marshes in the Mid‐Atlantic U.S. The high temporal resolution measurements of NH3 concentrations indicated that local sources, such as agriculture and industry, may have a considerable impact on the local atmospheric NH3 concentrations. The results also show that tidal water levels in salt marshes may have a significant effect on NH3 emissions. Key Points: Continuous and high temporal resolution of ammonia (NH3) concentrations were measured using cavity ring‐down spectroscopy over a salt marshAverage diurnal cycles of NH3 fluxes were estimated in a coastal ecosystem using a new analytical methodologyTidal water level was identified as a key parameter influencing NH3 emissions in wetlands [ABSTRACT FROM AUTHOR]

In the stable conditions prevailing at night, concentrations of emitted gases (e.g., radon [Rn], carbon dioxide [CO2], methane [CH4], ammonia [NH3], and nitrous oxide [N2O]) build up at the surface, with intermittent interruptions due to the passage of packets of turbulence. The applicability of conventional experimental methods is then questionable. Here, a statistical approach is proposed, in which micrometeorological field data are used to replicate the likely characteristics of a chamber experiment, yielding estimates of surface fluxes at the surface itself with reduced requirement for adequate fetch. Application of the virtual chamber methodology to two recent field studies is explored: (a) a study of nocturnal CO2 emission from a farmland area in Ohio in 2015; and (b) an investigation of NH3 effluxes from a crop previously treated with urea ammonium nitrate (UAN) in Illinois in 2014. For both datasets, the virtual chamber approach yields results in general agreement with eddy covariance (EC) data. [ABSTRACT FROM AUTHOR]

Despite a wealth of expertise involving leading institutions over at least 15 years, a base of the pyramid (BoP) model resulting in scalability has yet to emerge. We posit that institutional gaps between BoP goals of developing human and social capital on one hand and a short‐term profit focus of business on the other contribute to the lack of scalability. We address this gap by proposing a social intermediary to link the BoP with firms involved in the BoP. The social intermediary will coordinate and interpret the informal market requirements of the BoP to the firm in a "bottoms up" approach. We illustrate the bottoms up approach through a case involving Deutsche Gesellschaft fur Internationale Zusammenarbeit, a German government agency, with the garment manufacturing industry in Pakistan. The case study involves implementation of labor standards and productivity in the Pakistan garment industry, resulting in improved productivity and labor standards enabling garment manufacturers to access global supply chains. [ABSTRACT FROM AUTHOR]

Quantification of the emission rates of various gases from soils at night remains a challenge, confronting climate science (in the case of CO2 and CH4) and agriculture science (for NH3 and N2O, among others). In the stable conditions prevailing at night, concentrations of such emitted gases build up at the surface during the night, with intermittent interruptions commonly attributed to the passage of packets of turbulence. The utility of conventional micrometeorological experimental methods in such circumstances is questionable, and chamber methods have been developed to meet the challenge. Here, a statistical approach is proposed, in which micrometeorological field data are used to replicate the likely characteristics of a chamber experiment, yielding estimates of surface fluxes at the surface itself and not at some height above it. The methodology proposed is developmental at this time, with details intended to correspond to the use of both closed and vented chambers. Its application to three recent field studies is explored: (1) a study of nocturnal CO2 emission from two test areas (one previously tilled and the other not) in Ohio in 2015; (2) a similar experiment conducted in Zimbabwe in 2013 (one area previously tilled and a second left fallow), and (3) an investigation of NH3 effluxes from a crop previously treated with urea ammonium nitrate (UAN), in Illinois in 2014. There are few measurements with which to compare the results presented here, however the values obtained are within the range of available field data. [ABSTRACT FROM AUTHOR]

With sustainability education in a growth mode, many business educators ponder how best to introduce or more fully integrate sustainability into the business school curriculum. Simulations provide an important pedagogical tool in addressing this challenge. The following resource review evaluates simulations which, through varying approaches, address sustainability in business. The review involves offerings ranging from stand-alone courses to modules supporting individual courses. The review concludes with an overview of customization and learning outcomes offered by each participating firm. [ABSTRACT FROM AUTHOR]

Following Sine and David's research on the potential of environmental jolts shifting the status quo in U.S. energy policy, we focus on the potential for environmental non-profit organizations in Japan to shift the status quo through institutional entrepreneurial efforts following the environmental jolt from the Fukushima nuclear power catastrophe. We evaluate the institutionalization of energy policy in Japan both pre- and post-Fukushima as the context for examining the potential for change in Japan's energy policy. We utilize mixed qualitative and quantitative research methods to evaluate the attitudes and strategic inclinations of privately funded Japanese environmental non-profit organizations. Following Dreiling andWolf's model of material--organizational dependencies versus ideological motivations of non-profit organizations, we develop a typology to identify which, if any, segments of environmental Japanese non-profit organizations might pursue institutional entrepreneurial (Levy and Scully) opportunities in support of renewable energy policy. [ABSTRACT FROM AUTHOR]

The attitudes of Susquehanna River stakeholders regarding natural gas hydraulic fracturing (fracking) in the Marcellus Shale region reflect differing concerns on economic, social, and environmental issues based on gender, education level, and income. The focus on the U.S. State of Pennsylvania section of the Susquehanna River derives from the U.S. States of New York and Maryland, neighbors of Pennsylvania to the immediate north and south, respectively, enacting bans on fracking, while Pennsylvania has catapulted, through Marcellus fracking, to become the second largest natural gas producing state in the U.S. In this Pennsylvania survey, female and more highly educated stakeholders favor a moratorium on fracking, while males and lower income stakeholders support fracking. Of the four categories used to organize the survey, i.e. economic opportunity, health and safety, communities, and energy security, the category of health and safety ranked first in both the 2012 and 2017 survey. [ABSTRACT FROM AUTHOR]

Airborne turbulence measurement gives a spatial distribution of air-surface fluxes that networks of fixed surface sites typically cannot capture. Much work has improved the accuracy of such measurements and the estimation of the uncertainty peculiar to streams of turbulence data measured from the air. A particularly significant challenge and opportunity is to distinguish fluxes from different surface types, especially those occurring in patches smaller than the necessary averaging length. The flux fragment method (FFM), a conditional-sampling variant of eddy covariance in the space-time domain, was presented in 2008. It was shown capable of segregating the mean flux density (CO2, H2O, sensible heat) in maize from that in soybeans over the patchwork farmlands of Illinois. This was, however, an ideal surface for the method, and the random-error estimate used a relatively rudimentary bootstrap resampling. The present paper describes an upgraded random-error estimate that accounts for the serial correlation of the time/space series and the heterogeneity of the signal. Results are presented from the Alaskan tundra. Though recognized as important, systematic error estimates are not covered in this paper. Some discussion is offered on the relation of the FFM to other approaches similarly motivated, particularly those using wavelets. Successful measurement of the variation of air-surface exchange over heterogeneous surfaces has value for developing and improving process models relating surface flux to remotely sensible quantities, such as the vegetative land-cover type and its condition. [ABSTRACT FROM AUTHOR]

Abstract: Deposition of trace gases, such as sulfur dioxide (SO2), can affect plant and soil chemistry in different ecosystems. Measurements over a complex ecosystem, like a forest clearing, are necessary to determine more accurate deposition rates that can be used to improve parameterizations and models. The flux-gradient technique was used to determine SO2 fluxes over grass in a clearing at Duke Forest, North Carolina, USA on 25 June – 2 July 2008. The mean flux was −0.037 ± 0.024 μg m−2 s−1. Dew on the canopy enhanced the uptake of SO2, which increased deposition rates. Deposition velocities (Vd ) fluctuated greatly with a mean of 1.00 ± 0.48 cm s−1. The large variation in Vd was not fully captured by estimates determined from a multilayer model (MLM) and a big-leaf model (BLM). Mean deposition velocities derived from the MLM and BLM were 1.25 ± 0.21 cm s−1 and 0.63 ± 0.12 cm s−1, respectively. The model estimations of Vd in this study were probably affected by uncertainties associated with canopy resistance, particularly with stomatal and non-stomatal processes. [Copyright &y& Elsevier]

ABSTRACT To differentiate ecosystem management, three models of firm-level environmental stewardship are paired with three types of trust, which serve as informal governance mechanisms. The interconnectedness of organizational fields and the influence of intertemporality and interspatiality (time and space) are key dynamics in developing decentralized networks as an approach for linking firms, organizational fields, and global sustainability efforts. Interviews with 18 firms, government agencies, and nonprofit-making organizations from Japan and the USA are utilized to discuss the key concepts in the paper. Copyright © 2011 John Wiley & Sons, Ltd and ERP Environment. [ABSTRACT FROM AUTHOR]

The article reports on the use of the Flux-gradient technique to measure the magnitude of trace gas fluxes over an unfertilized agricultural field. Extensive spatial and temporal variability were exhibited by trace gas fluxes that are dependent on factors such as meteorology ambient concentration, and emission source size. In this study, Flux-gradient technique was used to measure ammonia, nitric acid and sulphur dioxide over unfertilized soybean field. It is concluded that in order to more accurately determine stomatal resistance and its influence on fluxes in future studies, quantification of vegetation characteristics would be beneficial.

This paper explores the theoretical underpinnings of collaboration and ecosystem management in order to identify the relationships and processes involved in implementing ecosystem management programs through cross-sector collaboration. Ecosystem management requires a highly adaptive and resilient social-ecological governance approach, which addresses spatiality and temporality issues. In order to explore possible implementation issues with ecosystem management, propositions are developed dealing with adaptive governance, institutional isomorphism and collective action. The paper concludes with a discussion of the theoretic underpinnings involved in implementing ecosystem management through cross-sector collaborations. Copyright © 2010 John Wiley & Sons, Ltd and ERP Environment. [ABSTRACT FROM AUTHOR]

To accurately predict ecosystem responses induced by climate warming at local-to-global scales, models are in need of more precise knowledge of response during periods of environmental stress such as drought. In this paper, we studied environmental control of canopy-level water use efficiency (WUE) during drought at an eddy flux site in an oak-hickory forest in central Missouri, USA. Two consecutive severe droughts in the summers of 2006 and 2007 afforded coverage of a broad range of environmental conditions. We stratified data to obtain subranges that minimized cross-correlations among putative WUE-controlling factors. Our results showed that WUE was subject to control by atmospheric saturation deficit (ASD), soil water potential (SWP) and the ratio of diffuse to total photosynthetically active radiation ( If/ It). Generally, WUE was found to scale with 1/(ASD)0.5, consistent with predictions from stomatal optimization theory. In contrast, SWP and If/ It were related to WUE in a linear fashion. ASD was better correlated with WUE than either of the other two factors. It was also observed that the relationship between WUE and any single controlling factor was subject to influence of the other two. One such example was an opposite response of WUE to SWP between low and high ASD values, suggesting a breakdown of stomatal optimality under severe environmental stresses and a shift from optimal stomatal regulation to nonstomatal regulation at leaf scale. We have demonstrated that different data handling (stratified vs. nonstratified) or selection (hourly vs. daily) could lead to different conclusions on the relationship between WUE and its controls. For this reason, we recommend modelers to be cautious when applying WUE-response formulas at environmental conditions or at time scales different from those at which they are derived. [ABSTRACT FROM AUTHOR]

During the last several decades, numerous policies and programs intended to advance environmental goals have been formulated in the US by governmental bodies and implemented by businesses and nongovernmental organizations. This article forwards a multi-sectoral perspective that business and nonprofit organizations have also been significantly involved in environmental policy and program formulation, as well as implementation, and that governments have also fulfilled the latter strategic role in US environmental policy. In this article, nine US environmental initiatives are described and categorized according to which of the three sectors' organizations were significant formulators of the programs and which were significant implementors. Implications for future research include investigation of other environmental dyadic program combinations in addition to those presented, extension of the present analysis beyond dyads into environmental policy networks, inclusion of the strategic environmental program evaluation stage to complement formulation and implementation and exploration of effectiveness variables in cross-sectoral, inter-organizational collaborations. Implications for educators and practitioners are also presented. Copyright © 2002 John Wiley & Sons, Ltd. and ERP Environment. [ABSTRACT FROM AUTHOR]

The high-arctic terrestrial environment is generally recognized as one of the world's most sensitive areas with regard to global warming. In this study, we examined the influence of an isolated warm period on net ecosystem carbon dioxide (CO2) exchange at high latitude during autumn. Using the Free Air Temperature Increase (FATI) technique, we manipulated air, soil, and vegetation temperatures in late August in a tundra site at Zackenberg in the National Park of North and East Greenland (74°N 21°W). The consequences for gross canopy photosynthesis, canopy respiration, and belowground respiration of increasing these temperatures by approximately 2.5°C were determined with closed dynamic CO2 exchange systems. Under current temperatures, the ecosystem acted as a net CO2 source, releasing 19 g CO2-C m−2 over the 14-day study period. Warm soils and senescing vegetation in autumn were unequivocally responsible for this efflux. Heating enhanced CO2 efflux to 29 g CO2-C m−2. This effect was attributed to a 39% increase in belowground respiration, which was the main component of the carbon (C) budget. Gross photosynthesis, on the other hand, was not affected significantly by the simulated warming. Although the aftereffects of an isolated warm period on the C balance in early winter could be significant, simulations with a simple C budget model suggest that soil carbon pools are not affected to a great extent by such a climatic disturbance. The influence on atmospheric carbon, however, appears to be significant. [ABSTRACT FROM AUTHOR]

Land surface temperature (LST) is a key variable in the determination of land surface energy exchange processes from local to global scales. Accurate ground measurements of LST are necessary for a number of applications including validation of satellite LST products or improvement of both climate and numerical weather prediction models. With the objective of assessing the quality of in situ measurements of LST and to evaluate the quantitative uncertainties in the ground-based LST measurements, intensive field experiments were conducted at NOAA's Air Resources Laboratory (ARL)'s Atmospheric Turbulence and Diffusion Division (ATDD) in Oak Ridge, Tennessee, USA, from October 2015 to January 2016. The results of the comparison of LSTs retrieved by three narrow angle broadband infrared temperature sensors (IRT), hemispherical longwave radiation (LWR) measurements by pyrgeometers, forward looking infrared camera with direct LSTs by multiple thermocouples (TC), and near surface air temperature (AT) are presented here. The brightness temperature (BT) measurements by the IRTs agreed well with a bias of <0.23 °C, and root mean square error (RMSE) of <0.36 °C. The daytime LST(TC) and LST(IRT) showed better agreement (bias = 0.26 °C and RMSE = 0.67 °C) than with LST(LWR) (bias > 1.1 and RMSE > 1.46 °C). In contrast, the difference between nighttime LSTs by IRTs, TCs, and LWR were <0.47 °C, whereas nighttime AT explained >81% of the variance in LST(IRT) with a bias of 2.64 °C and RMSE of 3.6 °C. To evaluate the annual and seasonal differences in LST(IRT), LST(LWR) and AT, the analysis was extended to four grassland sites in the USA. For the annual dataset of LST, the bias between LST (IRT) and LST (LWR) was <0.7 °C, except at the semiarid grassland (1.5 °C), whereas the absolute bias between AT and LST at the four sites were <2 °C. The monthly difference between LST (IRT) and LST (LWR) (or AT) reached up to 2 °C (5 °C), whereas half-hourly differences between LSTs and AT were several degrees in magnitude depending on the site characteristics, time of the day and the season. [ABSTRACT FROM AUTHOR]

Abstract: Atmospheric ammonia has been shown to degrade regional air quality and affect environmental health. In-situ measurements of ammonia are needed to determine how ambient concentrations vary in different ecosystems and the extent to which emission sources contribute to those levels. The objective of this study was to measure and compare ammonia concentrations in two Tennessee Valley (USA) ecosystems: a forested rural area and a metropolitan site adjacent to a main transportation route. Integrated samples of atmospheric ammonia were collected with annular denuder systems for ~4weeks during the summer of 2009 in both ecosystems. Ancillary measurements of meteorological variables, such as wind direction and precipitation, were also conducted to determine any relationships with ammonia concentration. Measurements in the two ecosystems revealed ammonia concentrations that were mostly representative of background levels. Arithmetic means were 1.57±0.68μgm−3 at the metropolitan site and 1.60±0.77μgm−3 in the forest. The geometric mean concentrations for both sites were ~1.46μgm−3. Wind direction, and to a lesser extent air temperature and precipitation, did influence measured concentrations. At the metropolitan site, ammonia concentrations were slightly higher in winds emanating from the direction of the interstate highway. Meteorological variables, such as wind direction, and physical factors, such as topography, can affect measurement of ambient ammonia concentrations, especially in ecosystems distant from strong emission sources. The 12-h integrated sampling method used in this study was unable to measure frequent changes in ambient ammonia concentrations and illustrates the need for measurements with higher temporal resolution, at least ~1–2h, in a variety of diverse ecosystems to determine the behavior of atmospheric ammonia and its environmental effects. [Copyright &y& Elsevier]

Abstract: We analyzed net CO2 exchange data from 13 flux tower sites with 27 site-years of measurements over maize and wheat fields across midcontinent North America. A numerically robust “light-soil temperature-VPD”-based method was used to partition the data into photosynthetic assimilation and ecosystem respiration components. Year-round ecosystem-scale ecophysiological parameters of apparent quantum yield, photosynthetic capacity, convexity of the light response, respiration rate parameters, ecological light-use efficiency, and the curvature of the VPD-response of photosynthesis for maize and wheat crops were numerically identified and interpolated/extrapolated. This allowed us to gap-fill CO2 exchange components and calculate annual totals and budgets. VPD-limitation of photosynthesis was systematically observed in grain crops of the region (occurring from 20 to 120 days during the growing season, depending on site and year), determined by the VPD regime and the numerical value of the curvature parameter of the photosynthesis-VPD-response, σ VPD. In 78% of the 27 site-years of observations, annual gross photosynthesis in these crops significantly exceeded ecosystem respiration, resulting in a net ecosystem production of up to 2100g CO2 m−2 year−1. The measurement-based photosynthesis, respiration, and net ecosystem production data, as well as the estimates of the ecophysiological parameters, provide an empirical basis for parameterization and validation of mechanistic models of grain crop production in this economically and ecologically important region of North America. [Copyright &y& Elsevier]