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The responses of crop functioning to changing climate and atmospheric CO2 concentration ([CO2]) could have large effects on food production, and impact carbon, water and energy fluxes, causing feedbacks to climate. To simulate the responses of temperate crops to changing climate and [CO2], accounting for the specific phenology of crops mediated by management practice, we present here the development of a process-oriented terrestrial biogeochemical model named ORCHIDEE-CROP (v0), which integrates a generic crop phenology and harvest module and a very simple parameterization of nitrogen fertilization, into the land surface model (LSM) ORCHIDEEv196, in order to simulate biophysical and biochemical interactions in croplands, as well as plant productivity and harvested yield. The model is applicable for a range of temperate crops, but it is tested here for maize and winter wheat, with the phenological parameterizations of two European varieties originating from the STICS agronomical model. We evaluate the ORCHIDEE-CROP (v0) model against eddy covariance and biometric measurements at 7 winter wheat and maize sites in Europe. The specific ecosystem variables used in the evaluation are CO2 fluxes (NEE), latent heat and sensible heat fluxes. Additional measurements of leaf area index (LAI), aboveground biomass and yield are used as well. Evaluation results reveal that ORCHIDEE-CROP (v0) reproduces the observed timing of crop development stages and the amplitude of pertaining LAI changes in contrast to ORCHIDEEv196 in which by default crops have the same phenology than grass. A near-halving of the root mean square error of LAI from 2.38 ± 0.77 to 1.08 ± 0.34 m² m-2 is obtained between ORCHIDEEv196 and ORCHIDEE-CROP (v0) across the 7 study sites. Improved crop phenology and carbon allocation lead to a general good match between modelled and observed aboveground biomass (with a normalized root mean squared error (NRMSE) of 11.0-54.2%), crop yield, as well as of the daily carbon and energy fluxes with NRMSE of ~9.0-20.1 and ~9.4-22.3 % for NEE, and sensible and latent heat fluxes, respectively. The model data mistfit for energy fluxes are within uncertainties of the measurements, which themselves show an incomplete energy balance closure within the range 80.6-86.3 %. The remaining discrepancies between modelled and observed LAI and other variables at specific sites are partly attributable to unrealistic representation of management events. In addition, ORCHIDEE-CROP (v0) is shown to have the ability to capture the spatial gradients of carbon and energy-related variables, such as gross primary productivity, NEE, sensible heat fluxes and latent heat fluxes, across the sites in Europe, an important requirement for future spatially explicit simulations. Further improvement of the model with an explicit parameterization of nutrition dynamics and of management, is expected to improve its predictive ability to simulate croplands in an Earth System Model. [ABSTRACT FROM AUTHOR]

Concentrations of atmospheric carbon dioxide (CO2) have continued to increase whereas atmospheric deposition of sulphur and nitrogen has declined in Europe and the USA during recent decades. Using time series of flux observations from 23 forests distributed throughout Europe and the USA, and generalised mixed models, we found that forest-level net ecosystem production and gross primary production have increased by 1% annually from 1995 to 2011. Statistical models indicated that increasing atmospheric CO2 was the most important factor driving the increasing strength of carbon sinks in these forests. We also found that the reduction of sulphur deposition in Europe and the USA lead to higher recovery in ecosystem respiration than in gross primary production, thus limiting the increase of carbon sequestration. By contrast, trends in climate and nitrogen deposition did not significantly contribute to changing carbon fluxes during the studied period. Our findings support the hypothesis of a general CO2-fertilization effect on vegetation growth and suggest that, so far unknown, sulphur deposition plays a significant role in the carbon balance of forests in industrialized regions. Our results show the need to include the effects of changing atmospheric composition, beyond CO2, to assess future dynamics of carbon-climate feedbacks not currently considered in earth system/climate modelling.

Despite an emerging body of literature linking canopy albedo to forest management, understanding of the process is still fragmented. We combined a stand-level forest gap model with a canopy radiation transfer model and satellite-derived model parameters to quantify the effects of forest thinning, that is removing trees at a certain time during the forest rotation, on summertime canopy albedo. The effects of different forest species (pine, beech, oak) and four thinning strategies (light to intense thinning regimes) were examined. During stand establishment, summertime canopy albedo is driven by tree species. In the later stages of stand development, the effect of tree species on summertime canopy albedo decreases in favour of an increasing influence of forest thinning on summertime canopy albedo. These trends continue until the end of the rotation where thinning explains up to 50% of the variance in near-infrared canopy albedo and up to 70% of the variance in visible canopy albedo. More intense thinning lowers the summertime shortwave albedo in the canopy by as much as 0.02 compared to unthinned forest. The structural changes associated with forest thinning can be described by the change in LAI in combination with crown volume. However, forests with identical canopy structure can have different summertime albedo values due to their location: the further north a forest is situated, the more the solar zenith angle increases and thus the higher is the summertime canopy albedo, independent of the wavelength. Despite the increase of absolute summertime canopy albedo values with latitude, the difference in canopy albedo between managed and unmanaged forest decreases with increasing latitude. Forest management thus strongly altered summertime forest albedo. [ABSTRACT FROM AUTHOR]

Gross primary productivity (GPP) is the largest and most variable component of the global terrestrial carbon cycle. Repeatable and accurate monitoring of terrestrial GPP is therefore critical for quantifying dynamics in regional-to-global carbon budgets. Remote sensing provides high frequency observations of terrestrial ecosystems and is widely used to monitor and model spatiotemporal variability in ecosystem properties and processes that affect terrestrial GPP. We used data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and FLUXNET to assess how well four metrics derived from remotely sensed vegetation indices (hereafter referred to as proxies) and six remote sensing-based models capture spatial and temporal variations in annual GPP. Specifically, we used the FLUXNET "La Thuile" data set, which includes several times more sites (144) and site years (422) than previous efforts have used. Our results show that remotely sensed proxies and modeled GPP are able to capture statistically significant amounts of spatial variation in mean annual GPP in every biome except croplands, but that the total variance explained differed substantially across biomes (R² ≈ 0.1 - 0.8). The ability of remotely sensed proxies and models to explain interannual variability GPP was even more limited. Remotely sensed proxies explained 40-60% of interannual variance in annual GPP in moisture-limited biomes including grasslands and shrublands. However, none of the models or remotely sensed proxies explained statistically significant amounts of interannual variation in GPP in croplands, evergreen needleleaf forests, and deciduous broadleaf forests. Because important factors that affect year-to-year variation in GPP are not explicitly captured or included in the remote sensing proxies and models we examined (e.g., interactions between biotic and abiotic conditions, and lagged ecosystems responses to environmental process), our results are not surprising. Nevertheless, robust and repeatable characterization of interannual variability in carbon budgets is critically important and the carbon cycle science community is increasingly relying on remotely sensing data. As larger and more comprehensive data sets derived from the FLUXNET community become available, additional systematic assessment and refinement of remote sensing-based methods for monitoring annual GPP is warranted. [ABSTRACT FROM AUTHOR]

Nitrous oxide (N2O) emissions are highly variable in time, with high peak emissions lasting a few days to several weeks and low background emissions. This temporal variability is poorly understood which hampers the simulation of daily N2O emissions. In structured soils, like clay and peat, aggregates hamper the diffusion of oxygen, which leads to anaerobic microsites in the soil, favourable for denitrification. Diffusion of N2O out of the aggregates is also hampered, which leads to delayed emissions and increased reduction of N2O to N2. In this model simulation study we investigate the effect of aggregates in soils on the N2O emissions. We present a parameterization to simulate the effects of aggregates on N2O production by denitrification and on N2O reduction. The parameterization is based on the mobile-immobile model concept. It was implemented in a field-scale hydrological-biogeochemical model combination. We compared the simulated fluxes with observed fluxes from a fertilized and drained peat soil under grass. The results of this study show that aggregates strongly affect the simulated N2O emissions: peak emissions are lower, whereas the background emissions are slightly higher. Including the effect of aggregates caused a 40% decrease in the simulated annual emissions relative to the simulations without accounting for the effects of aggregates. The new parameterization significantly improved the model performance regarding simulation of observed daily N2O fluxes; r² and RMSE improved from 0.11 and 198 g N2O-N ha-1 d-1 to 0.41 and 40 g N2O-N ha-1 d-1, respectively. Our analyses of the model results show that aggregates have a larger impact on the reduction than on the production of N2O. Reduction of N2O is more sensitive to changes in the drivers than production of N2O and is in that sense the key to understanding N2O emissions from denitrification. The effects of changing environmental conditions on reduction of N2O relative to N2O production strongly depend on the NO3 content of the soil. More anaerobic conditions have hardly any effect on the ratio of production to reduction if NO3 is abundant, but will decrease this ratio if NO3 is limiting. In the first case the emissions will increase, whereas in the second case the emissions will decrease. This study suggests that the current knowledge of the hydrological, biogeochemical and physical processes may be sufficient to understand the observed N2O fluxes from a fertilized clayey peatland. Further research is needed to test how aggregates affect the N2O fluxes from other soils or soils with different fertilization regimes. [ABSTRACT FROM AUTHOR]

Winter CO2 fluxes represent an important component of the annual carbon budget in northern ecosystems. Understanding winter respiration processes and their responses to climate change is also central to our ability to assess terrestrial carbon cycle and climate feedbacks in the future. The factors influencing the spatial and temporal pattern of winter respiration (RECO) of northern ecosystems are poorly understood. For this reason, we analyzed eddy covariance flux data sets from 57 ecosystem sites ranging from 35° N to 70° N. Deciduous forests carry the highest winter RECO ratios (9.7-10.5 gCm-2 d-1), when winter is defined as the period during which air temper10 ature remained below 0 °°C. By contrast, wetland ecosystems had the lowest winter RECO (2.1-2.3 gCm-2 d-1). Evergreen needle-leaved forests, grasslands and croplands were characterized by intermediate winter RECO values of 7.4-7.9 gCm-2 d-1, 5.8-6.0 gCm-2 d-1, and 5.2-5.3 gCm-2 d-1, respectively. Cross site analysis showed that winter air or soil temperature, and the seasonal amplitude of the leaf area index inferred from satellite observation, which is a proxy for the amount of litter available for RECO in the subsequent winter, are the two main factors determining spatial pattern of daily mean winter RECO. Together, these two factors can explain 71% (Tair, ÉLAI) or 69% (Tsoil, ÉLAI) of the spatial variance of winter RECO across the 57 sites. The spatial temperature sensitivity of daily winter RECO was determined empirically by fitting an Arrhenius relationship to the data. The activation energy parameter of this relationship was found to decrease at increasing soil temperature at a rate of 83.1 KJ엯C-1 (r =-0.32, p<0.05), which implies a possible dampening of the increase in winter RECO due to global warming. The interannual variability of winter RECO is better explained by soil temperature than by air temperature, likely due to the insulating effects of snow cover. The increase in winter RECO with a 1엯C warming based calculated from the spatial analysis was almost that double that calculated from the temporal analysis. Thus, models that calculate the effects of warming on RECO based only on spatial analyses could be over-estimating the impact. [ABSTRACT FROM AUTHOR]

Most countries use a 1-year-resolution emission factor approach (Tier 1 or 2) to estimate terrestrial N2O emissions as part of their national greenhouse gas inventory. Little attention has so far been paid to the effect of the temporal resolution of the approach (e.g., day, season, and year) on N2O emission estimates. The effect of lumping temporal variation can be very large because of daily or seasonal variations of processes causing N2O emissions. Therefore, we compared atmual N2O emissions from a model with daily time steps (DNDC) with those of a model with annual time steps (INITIATOR). Emissions were simulated for two intensively managed grassland plots in the Dutch fen meadow landscape. Annual N2O emissions from the investigated grasslands were sensitive to rainfall distribution within the year, especially to summer rainfall. We recommend that Tier 2 N2O emission estimates for intensively managed grasslands on peat soils in the temperate climate zone are adjusted for relative summer rainfall. [ABSTRACT FROM AUTHOR]

1. Pullets were given a control diet or a diet supplemented with a non-starch-polysaccharide hydrolysing enzyme preparation (NSP-enzyme) from weeks 6 to 14 of age to induce differences in the viscosity of the small intestinal ingesta. Half of each feeding group (n = 25) was infected with 250 embryonated Ascaridia galli eggs at an age of 6 weeks. 2. At 14 weeks of age, before the pullets were slaughtered, a balance experiment was conducted, to sample ingesta for viscosity measurements. Also, tissue samples of jejunum and ileum were taken for morphometrical and histopathological studies. 3. An infection of pullets with A. galli reduced the viscosity of the jejunal ingesta at high initial levels of viscosity after feeding the NSP-enzyme unsupplemented diet. 4. The faecal A. galli egg output by the pullets expressed as eggs per g excrement (EpG) was significantly reduced in infected pullets given the NSP-enzyme supplemented diet. Also, the number and length of worms was less in these pullets. 5. The tunica muscularis of the jejunum was significantly thickened, this effect being more pronounced at a low intestinal viscosity. 6. NSP-enzyme addition resulted in an increased length of jejunal villus and was paralleled by a decrease in jejunal viscosity. 7. Histopathology of jejunal and ileal sections revealed no pathological alterations. 8. The apparent retention of organic matter was increased after enzyme addition while parasite infection exerted no effect. [ABSTRACT FROM AUTHOR]

Half-hourly measurements of the net exchanges of carbon dioxide and water vapor between terrestrial ecosystems and the atmosphere provide estimates of gross primary production (GPP) and evapotranspiration (ET) at the ecosystem level and on daily to annual timescales. The ratio of these quantities represents ecosystem water use efficiency. Its multiplication with mean daylight vapor pressure deficit (VPD) leads to a quantity which we call "inherent water use efficiency" (IWUE*). The dependence of IWUE* on environmental conditions indicates possible adaptive adjustment of ecosystem physiology in response to a changing environment. IWUE* is analyzed for 43 sites across a range of plant functional types and climatic conditions. IWUE* increases during short-term moderate drought conditions. Mean annual IWUE* varied by a factor of 3 among all sites. This is partly explained by soil moisture at field capacity, particularly in deciduous broad-leaved forests. Canopy light interception sets the upper limits to canopy photosynthesis, and explains half the variance in annual IWUE* among herbaceous ecosystems and evergreen needle-leaved forests. Knowledge of IWUE* offers valuable improvement to the representation of carbon and water coupling in ecosystem process models. [ABSTRACT FROM AUTHOR]

Chambers are widely used to measure surface fluxes of nitrous oxide (N2O). Usually linear regression is used to calculate the fluxes from the chamber data. Non-linearity in the chamber data can result in an underestimation of the flux. Non-linear regression models are available for these data, but are not commonly used. In this study we compared the fit of linear and non-linear regression models to determine significant non-linearity in the chamber data. We assessed the influence of this significant nonlinearity on the annual fluxes. For a two year dataset from an automatic chamber we calculated the fluxes with linear and non-linear regression methods. Based on the fit of the methods 32% of the data was defined significant non-linear. Significant non-linearity was not recognized by the goodness of fit of the linear regression alone. Using non-linear regression for these data and linear regression for the rest, increases the annual flux with 21% to 53% compared to the flux determined from linear regression alone. We suggest that differences this large are due to leakage through the soil. Macropores or a coarse textured soil can add to fast leakage from the chamber. Yet, also for chambers without leakage non-linearity in the chamber data is unavoidable, due to feedback from the increasing concentration in the chamber. To prevent a possibly small, but systematic underestimation of the flux, we recommend comparing the fit of a linear regression model with a non-linear regression model. The non-linear regression model should be used if the fit is significantly better. Open questions are how macropores affect chamber measurements and how optimization of chamber design can prevent this. [ABSTRACT FROM AUTHOR]

Water-use efficiency (WUE) has been recognized as an important characteristic of vegetation productivity in various natural scientific disciplines for decades, but only recently at the ecosystem level, where different ways exist to characterize water-use efficiency. Hence, the objective of this research was (a) to systematically compare different ways of calculating ecosystem water-use efficiency (WUEe) from eddy-covariance measurements, (b) quantify the diurnal, seasonal and interannual variability of WUEe in relation to meteorological conditions, and (c) analyse between-site variability of WUEe as affected by vegetation type and climatic conditions, across sites in European forest ecosystems. Day-to-day variability of gross primary productivity (GPP) and evapotranspiration (ET) were more strongly coupled than net ecosystem production (NEP) and ET, obviously because NEP also depends on the respiration that is not heavily coupled to water fluxes. However, the slope of daytime NEP versus ET (mNEP) from half-hourly measurements of a single day may also be used as a WUEe-estimate giving very similar results to those of the GPP-ET slope (mGPP), since the diurnal variation is dominated by GPP. Since ET is the sum of transpiration (linked to GPP) and evaporation from wet vegetation and soil surfaces (not linked to GPP) we expected that WUEe is increasing when days after rain are excluded from the analysis. However only very minor changes were found, justifying an analysis of WUEe related to vegetation type. In most of the studied ecosystems the instantaneous WUEGPP was quite sensitive to diurnally varying meteorological conditions and tended to decline from the morning to the afternoon by more than 50% because of increasing vapour pressure deficits (VPD). Seasonally, WUEGPP increased with a rising monthly precipitation sum and rising average monthly temperatures up to a threshold of 11, 14 and 18°C in boreal, temperate and Mediterranean ecosystems, respectively. Across all sites, the highest monthly WUEGPP-values were detected at times of positive anomalies of summer-precipitation. During drought periods with high temperatures, high VPD, little precipitation and low soil water content, the water-use efficiency of gross carbon uptake (WUEGPP) tended to decrease in all forest types because of a stronger decline of GPP compared to ET. However the largest variation of growing season WUEGPP was found between sites and significantly related to vegetation type: WUEGPP was highest in ecosystems dominated by deciduous trees ranging from 5.0 gCO2 kgH2O-1 for temperate broad leaved deciduous forests (TD), to 4.5 for temperate mixed forests (TM), 3.5 for temperate evergreen conifers (TC), 3.4 for Mediterranean broad-leaved deciduous forests (MD), 3.3 for Mediterranean broad-leaved evergreen forests (Mbeg), 3.1 for Mediterranean evergreen conifers (MC), 2.9 for boreal evergreen conifers (BC) and only 1.2 g CO2 kgH2O-1 for a boreal wetland site (BT). Although vegetation type and meteorology co-vary, the WUEGPP variation was hardly related to meteorology, as we could show by comparing similar meteorological conditions only. Furthermore we compared across-site WUEGPP only under conditions when the 10% high GPP rates were exhibited. The between site differences remained, and at all sites ecosystem reached higher WUEGPP levels under this condition. This means when vegetation is most productive usually it also maximises the amount of carbon gained per water lost. Overall our results show that water-use efficiency exhibits a strong time-scale dependency in the sense that at longer time-scale meteorological conditions play a smaller role compared to shorter time scale. Moreover, we highlight the role of vegetation in determining carbon-water relation at ecosystem level. Consequently, all predictions of changing carbon-water cycle under changing climate should take into this role and the differences between vegetation types. These results show the strong time-scale dependency of water-use efficiency. [ABSTRACT FROM AUTHOR]

Due to uncertainties of several aspects of emerging health technologies, there is a need to anticipate these developments early. A first step would be to gather information and develop future visions about the technology. This paper introduces metaphor analysis as a novel way to do this. Specifically, we study the future of pharmacogenomics by comparing this technology with orphan drugs, which are more established and often act as a model with comparable (economic, research organisation, etc.) characteristics. The analysis consists of describing the dominant metaphors used and structurally exploring (dis)similarities between pharmacogenomics and orphan drugs developments. This comparison leads to lessons that can be learnt for the emerging pharmacogenomics future. We carried out a comprehensive literature review, extracting metaphors in a structured way from different areas of the drug research and development pipeline. The paper argues that (1) there are many similarities between orphan drugs and pharmacogenomics, especially in terms of registration, and social and economic impacts; (2) pharmacogenomics developments are regarded both as a future 'poison' and a 'chance', whereas orphan drugs are seen as a 'gift', and at the same time as a large 'problem'; and (3) metaphor analysis proves to be a tool for creating prospective images of pharmacogenomics and other emerging technologies. [ABSTRACT FROM AUTHOR]

A study was conducted to evaluate effects of age at weaning in combination with different weaning procedures on 2 breeds of lambs (Merinoland, Rhoenschaf). Lambs were either weaned at 8 or 16 wk of age in 2 stages or with the traditional method of weaning by abrupt separation. In the 2-stage treatment, lambs were prevented from nursing their dam for 1 wk (stage 1) before their separation (stage 2). Control animals were nursed by their dams until they were separated. Lamb BW and behavior (vocalization, agitation) were recorded before and after separation. After separation, lambs weaned at 8 wk of age had greater (P = 0.004) ADG compared with lambs weaned at 16 wk of age. Control lambs had greater (P < 0.001) agitation scores [1 = no agitation (normal behavior; i.e., feeding, resting, lying, standing, or play behavior) to 3 = high agitation (continuously moving, restlessness, or vocalization)] irrespective of weaning age and breed. On the day of separation, 2-stage lambs had scores from 1.17 to 1.35, whereas control lambs were scored from 1.70 to 1.79. After separation, lambs weaned in 2 stages vocalized up to 98.2% less (P = 0.001) than control animals. Furthermore, bleats were greater for Rhoenschaf lambs and at a weaning age of 8 wk (P < 0.05). Differences between treatments were greatest on the day of separation. Vocalization decreased continuously within the first 3 d of weaning to zero. Lambs weaned in 2 stages were less distressed than lambs weaned by the traditional method of abrupt separation based on behavioral data, but ADG until 12 and 16 wk of age did not differ (P > 0.05) for either treatment in this study. [ABSTRACT FROM AUTHOR]

An intercomparison is made of the Net Ecosystem Exchange of CO2, NEE, for eight Dutch grassland sites; four natural grasslands, two production grasslands and two meteorological stations within a rotational grassland region. At all sites the NEE was determined during at least 10 months per site, using the eddy-covariance (EC) technique, but in different years. The photosynthesis-light response analysis technique is used along with the respiration-temperature response technique to partition NEE among Gross Primary Production (GPP) and Ecosystem Respiration (Re) and to obtain the eco-physiological characteristics of the sites at the field scale. Annual sums of NEE, GPP and Re are then estimated using the fitted response curves with observed radiation and air temperature from a meteorological site in the centre of The Netherlands as drivers. These calculations are carried out for four years (2002-2005). The estimated annual Re for all individual sites is more or less constant per site and the average for all sites amounts to 1390±30 gCm²a-1. The narrow uncertainty band (±2%) reflects the small differences in the mean annual air temperature. The mean annual GPP was estimated to be 1325 gCm-2a-1, and displays a much higher standard deviation, of ±100 gCm-2a-1 (8%), which reflects the relatively large variation in annual solar radiation. The mean annual NEE amounts to -65±85 gCm-2a-1, which implies that on average the grasslands act as a source, with a relatively large standard deviation. From two sites, four-year records of CO2 flux were available and analyzed (2002-2005). Using the weather record of 2005 with optimizations from the other years, standard deviation of annual GPP was estimated to be 171-206 gCm-2a-1 (8-14%), of annual Re 227-247 gCm-2a-1 (14-16%) and of annual NEE 176-276 gCm-2a-1. The inter-site standard deviation was higher for GPP and Re, 534 gCm-2a-1 (37.3%) and 486 gCm-2a-1 (34.8%), respectively. However, the inter-site standard deviation of NEE was similar to the interannual one, amounting to 207 gCm-2a-1. Large differences occur due to soil type. The grasslands on organic (peat) soils show a mean net release of CO2 of 220±90 gCm-2a-1 while the grasslands on mineral (clay and sand) soils show a mean net uptake of CO2 of 90±90 gCm-2a-1. If a weighing with the fraction of grassland on organic (20%) and mineral soils (80%) is applied, an average NEE of 28±90 gCm-2a-1 is found, which means that on average the Dutch grasslands behave like a small sink for CO2. The results from the analysis illustrate the need for regionally specific and spatially explicit CO2 emission estimates from grassland. [ABSTRACT FROM AUTHOR]

The article presents a study which analyzes uncertainties and errors in time-integrated eddy correlation data for forest sites in the Amazon. It explores possible advective losses of carbon dioxide emissions for the specific situation of flux measurements at two Amazon forest sites. Based on results, it shows that uncertainties and errors caused by data spikes, delay corrections, and high-frequency loss are small.

Summary¶Observations of sensible and latent heat flux above forest downwind of a forest edge show these fluxes to be larger than the available energy over the forest. The enhancement averages to 56 W m-2, or 16% of the net radiation, at fetches less than 400 m, equivalent to fetch to height ratios less than 15. The enhancement of turbulent energy fluxes is explained by advection and increases with the difference in temperature and humidity of the air over the upwind area as compared to the forest. The relatively high temperature and humidity of the upwind air are not caused by high surface heat fluxes, but are explained by the relatively low aerodynamic roughness of the upwind surface. Although the heat fluxes over forest are enhanced, the momentum fluxes are almost adjusted to the underlying forest. The different behaviour of heat and momentum fluxes is explained by absorption of momentum by pressure gradients near the forest edge. It is concluded that fetch requirements to obtain accurate surface fluxes from atmospheric observations need to be more stringent for scalar fluxes as compared to momentum fluxes. [ABSTRACT FROM AUTHOR]

Abstract. This paper responds to the Forum contribution by Piovesan & Adams (2000) who criticized the results obtained by the EUROFLUX network on carbon fluxes of several European forests. The major point of criticism was that the data provided by EUROFLUX are inconsistent with current scientific understanding. It is argued that understanding the terrestrial global carbon cycle requires more than simply restating what was known previously, and that Piovesan & Adams have not been able to show any major conflicts between our findings and ecosystem or atmospheric-transport theories. [ABSTRACT FROM AUTHOR]