Abstract: Soil erosion varies spatially, and the variability is commonly estimated using the revised universal soil loss equation. Neglecting information about estimation uncertainty, however, may lead to improper decision-making. One geostatistical approach to spatial analysis is joint stochastic simulation, which draws alternative, equally probable, joint realizations of a regionalised variable. Differences between the realizations provide a measure of spatial uncertainty and allow us to carry out an error propagation analysis. The objective of this paper was to assess spatial uncertainty of a soil erodibility factor (K) model resulting from the uncertainties in the input parameters (texture and organic matter). The 500 km2study area was located in central-eastern Sardinia (Italy) and 152 samples were collected according to pedological horizons. A Monte Carlo analysis was performed incorporating spatial cross-correlation information through joint turning bands simulation was incorporated. A linear coregionalization model was fitted to all direct and cross-variograms of the input variables, which included three different structures: a nugget effect, a spherical structure with a shorter range (3500 m) and a spherical structure with a longer range (10000 m). The K factor was then estimated for each set of the 500 joint realizations of the input variables, and the ensemble of the model outputs was used to infer the soil erodibility probability distribution function. This approach permits delineation of the areas characterised by greater uncertainty, to improve supplementary sampling strategies and K value predictions.
Abstract: In the past few decades, many studies showed a significant worldwide warming, and consequently, changes
in frequency and persistence of extreme high-temperature events were observed. In order to analyse summer Tuscany (Italy)
patterns of climate change during the period 1955–2004, indices of temperature and of extreme events were investigated
for evidence of trend and change in inter-annual variability by using data of 40 weather stations. Least square regression
analysis and Theil-Sen nonparametric regression were applied for evidence of trends. The Mann–Kendall test was applied
to each time series to look for statistically significant trends.
The results showed a general increase in minimum and maximum temperatures and extreme temperature events.
Maximum temperature increase (+0.44 °C/decade) was slightly greater than minimum temperature (+0.38 °C/decade) and
consequently, an increase in summer daily temperature range (DTR) was noted (+0.06 °C/decade).
Inter-annual summer climate variability showed an increasing trend in the whole region, especially in regard to extreme
event occurrences while a small decreasing trend concerning diurnal temperature range was observed
Abstract: Besides playing an essential role in plant photosynthesis, solar radiation is also involved in many other important biological processes. In particular, it has been demonstrated that ultraviolet (UV) solar radiation plays a relevant role in grapevine (Vitis vinifera) in the production of certain important chemical compounds directly responsible for yield and wine quality. Moreover, the exposure to UV- B radiation (280-320 nm) can affect plant-disease interaction by influencing the behaviour of both pathogen and host. The main objective of this research was to characterize the solar radiative regime of a vineyard, in terms of PAR (Photosynthetically Active Radiation) and UV components. In this analysis, solar spectral UV irradiance components, broadband UV (280-400 nm), spectral UV-B and UV-A (320-400 nm), the biological effective UVBE, as well as the PAR (400-700 nm) component, were all considered. The diurnal patterns of these quantities and the U-VB/PAR and UV-B/UV-A ratios were analysed to investigate the effect of row orientation of the vineyard in combination with solar azimuth and elevation angles. The distribution of PAR and UV irradiance at various heights of the vertical wall of the rows was also studied.
The results showed that the highest portion of plants received higher levels of daily radiation, especially the UV-B component.
Row orientation of vine walls had a pronounced effect on the global PAR received by the two sides of the wall and, to a lesser extent, UV-A and UV-B. When only the diffused component was considered, this geometrical effect was greatly attenuated. UV-B/PAR and UV-A/PAR ratios were also affected with potential consequences on physiological processes. Because of the high diffusive capacity of the UV-B radiation, the UV-B/PAR ratio was significantly lower on the plant portions exposed to full sunlight than on those in the shade.
Abstract: A rising global population and demand for protein-rich diets are increasing pressure to maximize agricultural productivity. Rising atmospheric [CO2] is altering global temperature and precipitation patterns, which challenges agricultural productivity. While rising [CO2] provides a unique opportunity to increase the productivity of C-3 crops, average yield stimulation observed to date is well below potential gains. Thus, there is room for improving productivity. However, only a fraction of available germplasm of crops has been tested for CO2 responsiveness. Yield is a complex phenotypic trait determined by the interactions of a genotype with the environment. Selection of promising genotypes and characterization of response mechanisms will only be effective if crop improvement and systems biology approaches are closely linked to production environments, that is, on the farm within major growing regions. Free air CO2 enrichment (FACE) experiments can provide the platform upon which to conduct genetic screening and elucidate the inheritance and mechanisms that underlie genotypic differences in productivity under elevated [CO2]. We propose a new generation of large-scale, low-cost per unit area FACE experiments to identify the most CO2-responsive genotypes and provide starting lines for future breeding programmes. This is necessary if we are to realize the potential for yield gains in the future.
Abstract: UV Index information is currently recommended as a vehicle to raise public awareness about the risk of sun-exposure. It remains unknown to what extent this information can change personal sun-protective behavior. The aim of the study was to analyze the effects of UV-Index (UV-I) information provided by low cost, commercially available UV-I sensors on major indicators of sun-tanning behavior. A randomized-controlled trial was carried out on 94 healthy volunteers aged 21–23 years. After the exclusion of subjects with photosensitive disorders (n = 3), 91 subjects were randomized in two arms after stratification based on phototype and sex. Both arms received a diary to be filled every day with a log of intentional sun-exposure during summer. Subjects in the intervention group also received a commercially available UV-I sensor. The UV-I sensors were switched on and the UV-value was recorded in 77% of days with sun-exposure. During days of sun-exposure, subjects randomized to the intervention group had longer average time of sun-exposure (227.7 vs 208.7 min per day, P = 0.003), also between noon and 4 pm (P < 0.001), and less frequently adopted sun protective measures than controls (hat [6.4%vs 10.2%, P = 0.007], sunglasses [23.9%vs 30.8%, P = 0.003], sunscreen [41.4%vs 47.2%, P = 0.02]) and they experienced more frequent sunburns (27.8%vs 21.5%, P = 0.004). The odd ratio of sunburns was 1.60 for subjects in the intervention group compared with controls (after adjustment for sex, sunscreen use and skin type). The mean UV-I value recorded by volunteers was lower (5.6 [SD ± 0.9]) than that (7.3 [SD ± 0.46]) recorded by a professional instrument in the same period at the same latitude. Poststudy laboratory tests showed that the sensor was able to detect only about 60% of the solar diffuse radiation. The use of UV-I sensors changed the sun protective behavior of sunbathers in the direction of less use of sun protective measures. One possible explanation is that the low cost UV-meters may have functioned incorrectly and under-reported UV exposure. This may have led to an underestimation of UV-I values, erroneously reassuring subjects and causing a less protective sunbathing behavior. Another hypothesis relies on a cognitive pitfall in the subjects’ dealing with intermediate UV-I values, as they may have been discouraged in the use of sunscreen as they did not feel that they had yet been exposed to very harmful UV radiation.
Abstract: This paper provides an overview of the aims, objectives, research activities under-taken, and a selection of results generated in the European Commission-funded project entitled "Modelling the Impact of Climate Extremes" (MICE) - a pan-European end-to-end assessment, from climate model to impact model, of the potential impacts of climate change on a range of economic sectors important to the region. MICE focussed on changes in temperature, precipitation and wind extremes. The research programme had three main themes - the evaluation of climate model performance, an assessment of the potential future changes in the occurrence of extremes, and an examination of the impacts of changes in extremes on six activity sectors using a blend of quantitative modelling and expert judgement techniques. MICE culminated in a large stakeholder-orientated workshop, the aim of which was not only to disseminate project results but also to develop new stakeholder networks, whose expertise can be drawn on in future projects such as ENSEMBLES. MICE is part of a cluster of three projects, all related to European climate change and its impacts. The other projects in the cluster are PRUDENCE (Prediction of Regional Scenarios and Uncertainties for Defining European Climate Change Risks and Effects) and STARDEX (Statistical and Regional Dynamical Downscaling of Extremes for European Regions).
Abstract: Artemisia annua L. (Qinghao, Asteraceae) is a promising and potent antimalarial herbal drug. Its activity has been ascribed to
the content of artemisinin, a sesquiterpene lactone that is very effective against drug-resistant Plasmodium. Many studies have
pointed out that the presence of polymethoxyflavonoids in the phytocomplex can enhance the bioavailability or the activity of
artemisinin. In this study the production of both artemisinin and flavonoids by plants of an aromatic ecotype of A. annua L.
was characterized in different aerial parts of the plants at different developmental stages. The qualitative profile of the investigated
plant parts was similar; in addition to artemisinin, four flavonoids were identified: chrysoplenetin, casticin, eupatin and artemetin.
The highest contents of both flavonoids and artemisinin were found at the full blooming stage. At this developmental stage, artemisinin
was higher in leaves than in inflorescences, while the total flavonoid levels were similar in both plant organs.
Abstract: The current work investigates on the applicability of a widespread bio-geochemical model (BIOME-BGC) to estimate seasonal photosynthesis and transpiration within water limited Mediterranean forest environments. The use of the model required a preliminary calibration phase, aimed at setting its ecophysiological parameters to properly simulate the behavior of three Mediterranean species (Quercus ilex L., Quercus cerris L. and Pinus pinaster Ait.). For each of these species, the calibration of BIOME-BGC was performed by adjusting the monthly gross primary productivity (GPP) estimates of 10 forest plots to those of a simplified parametric model, C-Fix, which is based on the use of satellite and ancillary data. In particular, BIOME-BGC was run modifying the eco-physiological parameters controlling stomatal conductance, in order to identify the best model configurations to reproduce the spatial, intra-and inter-annual GPP variations simulated by C-Fix. Next, the fraction of leaf nitrogen in Rubisco was adjusted to fit also the magnitudes of the C-Fix GPP estimates. The subsequent testing phase consisted of applying the original and calibrated versions of BIOME-BGC in independent forest sites where the three species considered were dominant and for which field measurements of photosynthesis and transpiration were available. In all cases the use of the calibrated BIOME-BGC versions led to notably improve the GPP and transpiration estimation accuracy of the original model. The results obtained encourage the operational application of BIOME-BGC in Mediterranean forest environments and indicate a possible strategy to integrate its functions with those of C-Fix. (c) 2007 Elsevier B.V. All rights reserved.
Abstract: The objective of this paper is to evaluate the impacts of agriculture and water policy scenarios on the sustainability of selected irrigated farming systems in Italy, in the context of the forthcoming implementation of the directive EC 60/2000. Directive EC 60/2000 (Water Framework Directive) is intended to represent the reference norm regulating water use throughout Europe. Five main scenarios were developed reflecting aspects of agricultural policy, markets and technologies: Agenda 2000, world market, global sustainability, provincial agriculture and local community. These were combined with two water price levels, representing stylised scenarios for water policy. The effects of the scenarios on irrigated systems were simulated using multi-attribute linear programming models representing the reactions of the farms to external variables defined by each scenario. The output of the models consists of economic, social and environmental indicators aimed at quantifying the impact of the scenarios on different aspects of sustainability relevant for irrigated farming systems. Five Italian irrigated farming systems were considered: cereal, rice, fruit, vegetables and citrus. The results show the diversity of irrigated systems and the different effects that water pricing policy may produce depending on the agricultural policy, market and technological scenarios. They also highlight a clear trade-off between socio-economic sustainability and environmental (water, nitrogen, pesticide) sustainability. Water pricing will have, in most cases, less impact than agricultural markets and policy scenarios, though it appears to be an effective instrument for water regulation in the least intensive irrigated systems considered. This emphasises the need for a differentiated application of the Water Framework Directive at the local level as well as a more careful balance of water conservation, agricultural policy and rural development objectives. (c) 2006 Elsevier Ltd. All rights reserved.
Abstract: We evaluated the performance of a general circulation model (HadCM3), a regional circulation model (HadRM3P) and an artificial neural network (ANN), in reproducing daily maximum and minimum temperature (T-max and T-min) at site scale (Florence, Italy) for the present climate. The T-max and T-min values that were observed and those reproduced by HadCM3, HadRM3P and ANN for both the present and future climate scenarios (IPCC scenarios A2 and B2) were then used as input data in a cropping systems simulation model (CropSyst). In particular, climatic impact on the phenological developmental stages of a summer crop (sunflower Helianthus annuus L.) and winter crop (durum wheat Triticum aestivum L.) were evaluated. In addition, the frequency of extreme climatic events during specific crop phenological stages (i.e. number of events with T-max and T-min above and below stressful thresholds) were evaluated. The comparison between observed T-max and T-min, values and those produced by HadCM3, HadRM3P and ANN for the present climate, provided evidence for a higher accuracy of the ANN model in simulating these variables. The crop phenological stages and the related extreme climate events were therefore also better reproduced using the ANN climate data. The use of HadCM3 and HadRM3P climate data in climate change impact assessments seemed to result in an overestimation of the impacts (i.e. greater reduction in the length of development phases and greater changes in the frequency of extreme climate events during the most sensitive development stages) compared with those obtained using ANN climate data.
Abstract: Crop growth simulation models have been mainly developed to simulate final yield reliably. Thus, a main challenge in these models is the definition of a stable method for expressing the growth of harvested organs (e.g., fruit, seed, tuber, etc.). Generally, two approaches have been used: growth rate analysis of harvested organs [yield growth rate (YGR)] and analysis of harvest index (HI) increase over time (dHI/dt). This work aims to: 1) examine whether YGR and dHI/dt increase linearly over much of growing period, and 2) compare the two growth indices in terms of stability across a number of treatments, in order to identify which is the best indicator of harvest-organ growth. This analysis has already been performed fora large number of field crops, including wheat (Triticum aestivum L.), sunflower (Helianthus annuus L.), soybean (Glycine max L. (Merr.) and pea (Pisum sativum L.), but it has never been attempted in crops where final yield is not simply seeds. In this study, YGR and dHI/dt performances for tomato (Lycopersicum esculentum Mill.), potato (Solanum tuberosum L.), and eggplant (Solanum melongena L.) were compared using 21, 18, and 4 datasets, respectively. Results indicated that both descriptors of harvest-organ growth increased linearly for most of the growth period, whilst the comparison among the two variables in terms of stability showed that, although a direct statistical test failed, dHI/dt was more suitable to describe harvest-organ growth (smaller coefficient of variability) under a large range of crop management conditions (e.g., irrigation, sowing date, planting density, and water salt concentration).
Abstract: A stable, conservative variable is needed to describe the level of water-deficit stress to which grapevines are subjected. In agronomic crops, a function based on the amount of transpirable water stored in the soil has been found to provide such stable functions. This initial study examined whether this approach could be used to describe the response of transpiration rate and leaf area development rate in grapevines. The soil in which four-year-old grapevines (Vitis vinifera L. cv. Sangiovese) were growing was allowed to dry over several days. Both transpiration rate, which is assumed to be proportional to the gas exchange capability of the plant, and leaf area development rate did not decrease until the fraction of the transpirable soil water (FTSW) declined to about 0.35. Below 0.35 FTSW there was a continuous decline in each process until they were zero at FTSW = 0. The overall behavior of the plants to the drying soil was well described by logistic equations based on FTSW.
Abstract: The impact of powdery (Uncinula necator) and downy mildew (Plasmopara viticola) on grapevine leaf gas exchange was analysed. Gas exchange measurements (assimilation A, transpiration E, stomatal conductance g(s), intercellular concentration of CO2Ci) were made on three different leaf materials: (i) healthy tissue of diseased leaves, (ii) infected tissue of diseased leaves, (iii) healthy tissue of healthy leaves (control treatment). Using the same source of leaf tissue, photosynthetic pigment concentration (chlorophyll a, b) and fluorescence levels (minimal fluorescence F-0, maximal fluorescence F-m and the optimal quantum yield [F-m - F-0]/F-m) were determined to explain the mechanism of action of the two diseases on leaf assimilation. The results indicated that powdery and downy mildew reduced the assimilation rates, not only through a reduction in green leaf area (visual lesions), but also through an influence on gas exchange of the remaining green leaf tissues, determining a 'virtual lesion'. The ratios between virtual and visual lesions were higher in powdery mildewed leaves than in the downy mildewed leaves. The photosynthetic fluorescence level (F-v/F-m) was affected by neither of the two pathogens. The reduction in intercellular concentration of CO2 and photosynthetic pigment may explain the lower assimilation rates in the healthy tissues of powdery and downy mildewed leaves respectively.
Abstract: The paper reports the first results of the Project WADI (Sustainability of European Irrigated Agriculture under Water Directive and Agenda 2000), funded under the 5th Framework Programme of the European Union (EU). The objective of the project is to evaluate the economic, social and environmental sustainability of European irrigated farming under different scenarios concerning water policy and the Common Agricultural Policy. The methodology relies on scenario analysis combined with farm level mathematical programming models. Two pilot case studies are presented for Italy: cereal farming and fruit farming. According to the first results, the impact of the directive, up to reasonable prices, may be summed up in a minor reduction of water use associated with a sharp decrease of farm income and a significant reduction of employment. Nevertheless, different farming systems may react in very different ways. More detailed local analyses are needed in order to support the design of effective and efficient policies at basin level. (C) 2004 Elsevier Ltd. All rights reserved.
Abstract: Plants of Vitis vinifera (cv. Sangiovese) were submitted to elevated carbon dioxide concentrations in the field, using a FACE array; the experiment took place in a vineyard in Central Italy, throughout two growth seasons. The effects of fumigation on stem hydraulic properties and leaf water relations were evaluated. A significant decrease in stomatal conductance did not result in marked differences in leaf water potentials of FACE plants. Apparently, embolism formation showed to increase and hydraulic sufficiency to decrease after two years of exposure to elevated CO2. The allometric relationships between stem hydraulic conductivity, leaf area and stem cross-sectional area of xylem imply a physiological origin, though being unclearly affected by elevated CO2. The effect of elevated CO2 on water relations and hydraulic parameters of Sangiovese grapevine displayed variation reliant on fumigation time-span. Under these experimental conditions, changes in hydraulic properties in FACE plants did not provide a direct explanation for variations in leaf water relations in comparison with controls.
Abstract: The estimation of transpiration fluxes through wide vegetated land surfaces is of great importance for the proper planning and management of environmental resources, particularly in areas where water is a main limiting factor during at least part of the growing cycle. While remotely sensed techniques cannot directly measure these fluxes, they can provide useful information on vegetation variables such as Leaf Area Index (LAI), which are functionally related to the mentioned processes. The aims of the present work were: ( a) to illustrate the use of multi-temporal LAI profiles derived from National Oceanic and Atmospheric Administration Advanced Very High Resolution Radiometer (NOAA-AVHRR) Normalized Difference Vegetation Index (NDVI) data as input for a biogeochemical model (Forest-BGC) which simulates the main processes of forest vegetation ( transpiration and photosynthesis); and (b) to analyse the sensitivity of the calibrated model to its main driving variables ( meteorological data and NDVI-derived LAI profiles) in order to assess their relative importance for operational transpiration monitoring. In particular, the model was applied to two oak stands in the Tuscany Region ( central Italy), which are representative of Mediterranean forests and for which a calibration phase had already been performed. Simulations were carried out for a 15-year period ( 1986 - 2000) using as inputs daily meteorological data and NDVI-derived monthly LAI profiles. The sensitivity of the model to both input types was then assessed through other model runs with fixed values of the two variables. The results of these experiments indicated that the remotely sensed LAI estimates are the main determinant of simulated transpirations, especially during the Mediterranean arid season ( summer) when water resources are the primary limiting factor for vegetation development.
Abstract: increased atmospheric CO2 concentration are known to affect crop performance and water consumption. This study evaluated potato yield and water use efficiency (WUE) by assessing tuber yield and monitoring actual crop evapotranspiration (ET) for two consecutive years. Potato (Solanum tuberosum L.) cv. Bintje was grown in a free air CO2 experiment (FACE) in central Italy, under both ambient and elevated CO2 (550 mumol mol(-1)). FACE, ringed and non-ringed control plots were arranged in a replicated Latin-square experimental design. The best cultural practices were applied including ample water supply. ET was monitored throughout the crop cycle, on an hourly basis, by using the residual energy balance approach. Net radiation and soil heat flux were measured on three replicates for each treatment. Canopy radiative temperature was also monitored on the same plots by means of infrared thermometers, while wind and temperature profiles were measured separately at a central location. Instruments were frequently exchanged to avoid systematic errors due to sensors mismatch. Sensible heat flux was computed on the basis of air and canopy temperatures and of the aerodynamic resistance-and latent heat flux as the residual of the crop energy balance. Mean seasonal daytime canopy temperature of FACE was increased 0.6 degreesC in 1998 and 0.9 degreesC and 1999 as a result of increased canopy resistance. As a result, mean daily water use in 1998 was 6.58 +/- 0.12 and 7.22 +/- 0.14 mm per day for FACE and control, respectively. On a seasonal basis, FACE used 342 mm of water compared with 375 rum used by the crop under ambient conditions. During the second year of the study, the effect of fumigation on the water use by the crop was more evident. Daily mean water use in FACE was 4.98 +/- 0.24, compared with 5.9 +/- 0.25 under ambient conditions while total seasonal water consumption was 297 and 353 mm, respectively. The overall FACE water saving across both years was 11.8%. The higher tuber yield and lower ET lead to a substantial increase in WUE of FACE, namely 70 and 67% in 1998 and 1999, respectively. These figures are higher than reported in previous FACE experiments, for either cool or warm seasons crops and suggest that this basic commodity would benefit from a CO2 enriched air, both in terms of yield performance and water savings. (C) 2003 Elsevier Science B.V. All rights reserved.
Abstract: Potato (Solanum tuberosum L cv. Bintje) was exposed to ambient and elevated carbon dioxide (CO2), to ambient and elevated ozone (O-3) and to elevated levels of both gases during two growing seasons, 1998 and 1999. Experiments in open-top chambers (OTC) were carried out in Finland, Sweden, Ireland, United Kingdom, Germany and Belgium and a FACE (Free Air Carbon dioxide Enrichment) experiment was carried out in Italy. In OTCs the plants were grown tinder ambient CO2 concentrations or with 550 and 680 mul 1(-1) CO2 alone or in combination with ambient or elevated 03 concentrations (target seasonal mean of 60 nl 1(-1) 8 h per day). In the FACE systems the plants were exposed to ambient or 550 mul 1(-1) CO2. In the OTC experiments the reducing sugar content of potato tubers decreased significantly with increased concentration Of O-3. The starch content of potato tubers decreased, with negative impact on tuber quality, but the ascorbic acid concentration increased as a function of the AOT40 (The sum of the differences between hourly ozone concentration and 40 nl 1(-1) for each hour when the concentration exceeds 40 nl 1(-1) during a relevant growing season). However, simultaneous exposure to elevated CO2 counteracted the ozone effect. With increase in the CO2 exposure, glycoalkaloid and nitrate concentrations decreased yielding. improved quality, while the citric acid concentration decreased causing a higher risk for discoloration after cooking. The amount of dry matter and starch increased significantly in the FACE experiment. (C) 2002 Elsevier Science B.V. All rights reserved.
Abstract: The current work deals with the use in a Mediterranean environment of a simulation model of forest ecosystem processes which was originally created for temperate areas (FOREST-BGC). The model was calibrated and applied on two deciduous forest stands in Tuscany (Central Italy) by using conventional and remote sensing data as inputs. First, information on the two stands needed to initialise the model was derived from different sources, while meteorological data were extrapolated from a nearby station by an existing procedure (MT-Clim). Temporal profiles of leaf area index (LAI) were then derived both from direct ground measurement and from the processing of NOAA-AVHRR NDVI data. The model was calibrated using stand transpiration values obtained for 1997 by a sap flow method. Next, its performances were tested against the same transpiration values measured in 1998. The results obtained indicate that FOREST-BGC is capable of simulating water fluxes of Mediterranean forests when suitable LAI profiles are considered. Moreover. the derivation of these profiles from NDVI data can improve the model performance probably due to an enhanced consideration of the effects of the typical Mediterranean summer water stress. These results support the final objective of the work, which is the development of a procedure capable of integrating conventional and remote sensing data to operationally simulate water and carbon fluxes on a regional scale. (C) 2002 Elsevier Science B.V. All rights reserved.
Abstract: The main objective of the CHIP project was to perform 'standardised' investigations of potato (Solanum tuberosum L. cv Bintje) responses to increased O-3 and CO2 Concentrations by means of open-top chambers (OTC) and free air carbon dioxide enrichment (FACE) systems. The experimental sites are located across Europe representing a broad range of different climatic conditions. In 1998 and 1999 a total number of 12 OTC experiments and four FACE experiments were conducted. According to the specific needs for subsequent modelling purposes, environmental data were collected during experiments, i.e. air temperature, global radiation, air humidity (vapour pressure deficit (VPD)), soil moisture and trace gas concentrations. In the present paper, the results of these measurements are summarised. It was shown that the experiments covered a considerable range of growing season mean air temperatures (13.8-19.9 degreesC) and global irradiances (12.0-21.3 MJ m(-2) per day), the most important driving variables for crop growth simulation models. Analysis of the soils used during the experiments demonstrated that in most cases sufficient nutrient elements were available to guarantee an undisturbed growth. Mean concentrations Of CO2 and O-3 in ambient air and in different treatments illustrate the observed variability of trace gas exposures between different sites and experiments. However, the effects of these parameters on growth and yield are subject of separate papers. The general climatic conditions across Europe are also causing important growth and yield effects. Comparison of marketable tuber yields revealed an increase at higher latitudes. This result was associated with lower temperatures and VPD and longer day lengths at the higher latitudes, which in turn were associated with longer growing seasons. (C) 2002 Elsevier Science B.V. All rights reserved.
Abstract: This paper reviews the knowledge on effects of climate change on agricultural productivity in Europe and the consequences for policy and research. Warming is expected to lead to a northward expansion of suitable cropping areas and a reduction of the growing period of determinate crops (e.g. cereals), but an increase for indeterminate crops (e.g. root crops). Increasing atmospheric CO2 concentrations will directly enhance plant productivity and also increase resource use efficiencies. In northern areas climate change may produce positive effects on agriculture through introduction of new crop species and varieties, higher crop production and expansion of suitable areas for crop cultivation. Disadvantages may be an increase in the need for plant protection, the risk of nutrient leaching and the turnover of soil organic matter. In southern areas the disadvantages will predominate. The possible increase in water shortage and extreme weather events may cause lower harvestable yields, higher yield variability and a reduction in suitable areas for traditional crops. These effects may reinforce the current trends of intensification of agriculture in northern and western Europe and extensification in the Mediterranean and southeastern parts of Europe. Policy will have to support the adaptation of European agriculture to climate change by encouraging the flexibility of land use, crop production, farming systems etc. In doing so, it is necessary to consider the multifunctional role of agriculture, and to strike a variable balance between economic, environmental and social functions in different European regions. Policy will also need to be concerned with agricultural strategies to mitigate climate change through a reduction in emissions of methane and nitrous oxide, an increase in carbon sequestration in agricultural soils and the growing of energy crops to substitute fossil energy use. The policies to support adaptation and mitigation to climate change will need to be linked closely to the development of agri-environmental schemes in the European Union Common Agricultural Policy. Research will have further to deal with the effect on secondary factors of agricultural production, on the quality of crop and animal production, of changes in frequency of isolated and extreme weather events on agricultural production, and the interaction with the surrounding natural ecosystems. There is also a need to study combined effects of adaptation and mitigation strategies, and include assessments of the consequences on current efforts in agricultural policy to develop a sustainable agriculture that also preserves environmental and social values in the rural society. (C) 2002 Elsevier Science B.V. All rights reserved.
Abstract: Central to the CHanging climate and potential Impacts on Potato yield and quality project (CHIP) was the consideration of the potential impacts of ozone and CO2 on growth and yield of future European Potato crops. Potato crops, cv. Bintje, were exposed to ambient or elevated ozone; targeted daily average, 60 nl 1(-1) for 8 h, and ambient or elevated CO2; targeted 680 mul 1(-1) averaged over the full growing season, in open top chambers (OTCs) at six European sites in 1998 and 1999, or to elevated CO2 (550 mul 1(-1)) in Free Air Carbon dioxide Enrichment facilities (FACE) at two sites in both years. Some OTC experiments included 550 mul 1(-1). Above and below ground biomass were measured at two destructive harvests; at maximum leaf area (MLA) and at final-harvest. Final-harvest fresh weight yields of marketable-size tubers, >35 turn diameter, from ambient conditions ranged from 1 to 12 kg m(-2). There was no consistent (P > 0.1) CO2 x 03 interaction for growth or yield variables at either harvest. No consistent effects of ozone were detected at the maximum-leaf-area harvest. However, at final harvest, ozone had reduced both above-ground biomass and tuber dry weight (P < 0.05), particularly of the largest ( > 50 mm) size class. These yield losses showed linear relationships both with accumulated ozone exposure; AOT40 expressed as nl 1(-1) h over 40 nl 1(-1), and with yields from chambered ambient-ozone treatments (P < 0.05) but, because of partial confounding between the treatment AOT40s and the ambient-ozone yields in the data, the two relationships were not completely independent. Yields from ambient-ozone treatments, however, explained a significant (P < 0.01) amount of the residual variation in ozone effects unexplained by AOT40. When averaged over all experiments, mean dry weights and tuber numbers from both harvests were increased by elevated CO2. Only green leaf number at the MLA harvest was reduced. The CO2 responses varied between sites and years. For marketable-size tubers, this variation was unrelated to variation in ambient-CO2 treatment yields. Yield increases resulting from the 680 mul 1(-1) and 550 mul 1(-1) treatments were similar. Thus elevating [CO2] from 550 to 680 mul 1(-1) was less effective than elevating [CO2] from ambient to 550 mul 1(-1). On average, CO2 elevation to 680 mul 1(-1) increased the dry weight of marketable-size tubers by about 17%, which far exceeded the average ozone-induced yield loss of about 5%. The net effect of raising CO2 and O-3 concentrations on the European potato crop would be an increase marketable yield. (C) 2002 Elsevier Science B.V. All rights reserved.
Abstract: This paper describes the effects of elevated CO2 (550 and 680 mul 1(-1)) and O-3 (60 nl 1(-1) O-3 as an 8 h mean), alone or in combination, on canopy development and senescence in potato (Solanum tuberosum L. cv Bintje) across a range of European agro-climatic conditions. The assessments were made within the European CHIP project (CHanging climate and potential Impacts on Potato yield and quality) that was conducted for two growing seasons (1998 and 1999) in free air CO2 enrichment systems (FACE) and open-top chamber facilities (OTCs) at seven European sites. A comparison of chambered and unchambered experimental plots was included to examine the effects of chamber enclosure. Phenological growth stages, plant height, leaf area index (LAI) and the number of green and yellow leaves were recorded non-destructively throughout the growing season and by a destructive intermediate harvest at maximum leaf area (MLA). In the dynamic growth analysis CO2 and O-3 effects were studied over three developmental stages: canopy expansion, full canopy and canopy senescence. Chamber enclosures promoted potato crop development (taller plants, more leaves) during the initial growth stages and led to a faster decline of LAI and a higher number of yellow leaves. The growth in ambient plots varied between sites and seasons, as did the scale of the treatment responses. Despite the large background variation, some overall treatment effects could be detected across all sites. Both levels of increased CO2 reduced final plant height in comparison to ambient concentrations, which indicates a premature ending of the active plant growth. At the stage of full canopy and crop senescence the average number of green leaves was significantly (P < 0.05) decreased by 680 mul 1(-1) CO2 (OTC experiments) and LAI showed the same tendency (P = 0.07). As there was however no indication of a decreased leaf formation during initial growth and at full canopy, this must have been due to an earlier leaf fall. In the FACE experiments LAI had already began to decline at the stage of full canopy at 550 mul 1(-1) CO2 but not in ambient CO2 (DAE x CO2, P < 0.05). These observations strongly indicated that elevated CO2 induced a premature senescence during full canopy. O-3 did not have an overall detrimental effect on crop development during initial growth nor at full canopy, but did induce a faster reduction of LAI during crop senescence (DAE x O-3, P < 0.05). Final plant height was not affected by O-3. There were few CO2 x O-3 interactions detected. There was a suggestion (P = 0.06) that O-3 counteracted the CO2-induced decrease of green leaves at full canopy, but on the other hand during crop senescence the decline of LAI due to elevated O-3 was faster at ambient, compared to elevated CO2 (P < 0.05). These responses of canopy development to elevated CO2 and O-3 help to explain the treatment responses of potato yield within the CHIP project at sites across Europe. (C) 2002 Elsevier Science B.V. All rights reserved.
Abstract: Potato cv. Bintje was grown in open-top-chambers and free-air-CO2-enrichment systems at 7 sites across Europe for 2 years (1998-99). The effect of different treatments (CO2 enrichment and O-3 fumigation) on the chlorophyll content of fully expanded upper and lower canopy leaves was investigated collecting Minolta SPAD-502 meter readings. In both CO2 treated and O-3 fumigated plants, leaves had lower chlorophyll content than those in ambient air controls; season-long chlorophyll averages were 9.3% lower in the 'CO2' treatments, 9.1% lower in 'O-3' treatments and 12.3% lower in 'CO2+O-3' treatments. The analysis of chlorophyll content in three different growth phases (Emergence-Tuber Initiation; Tuber Initiation-Maximum Leaf Area; Maximum Leaf Area-Harvest) showed that in the early growth period, i.e. before tuber initiation there was a slight indication for an higher chlorophyll content at elevated CO2 (+ 3.8%) or O-3 (+1.7%). However, from tuber initiation onwards the leaves of plants grown under elevated CO2 or O-3 showed a progressively lower chlorophyll content (-4.8% for CO2 treatments and -2.6% for O-3 treatments) indicating a faster senescence of leaves that increased during the late growth period (-12.8% for CO2 treatments and -12.7% for O-3 treatments) and that was enhanced by CO2-O-3 interaction (-17.8%). (C) 2002 Elsevier Science B.V. All rights reserved.
Abstract: Although using hourly weather data offers the greatest accuracy for estimating growing degree-day values, daily maximum and minimum temperature data are often used to estimate these values by approximating the diurnal temperature trends. This paper presents a new empirical model for estimating hourly mean temperature. The model describes the diurnal variation using a sine function from the minimum temperature at sunrise until the maximum temperature is reached, another sine function from the maximum temperature until sunset, and a square-root function from then until sunrise the next morning. The model was developed and calibrated using several years of hourly data obtained from five automated weather stations located in California and representing a wide range of climate conditions. The model was tested against an additional data-set at each location. The temperature model gave good results, the root-mean-square error being less than 2.0°C for most years and locations. The comparison with published models from the literature showed that the model was superior to the other methods. Hourly temperatures from the model were used to calculate degree-day values. A comparison between degree-day estimates from the model and those obtained from other selected methods is presented. The results showed that the model had the best accuracy in general regardless of the season
Abstract: Accurate estimates of crop evapotranspiration (ETc), that quantify the total water used by a crop, are needed to optimize irrigation scheduling for horticultural crops and to minimize water degradation. During early growth, accurate assessments of ETc are difficult in vegetable crops because of high soil evaporation due to frequent irrigation. A model to estimate ETc for vegetable crops, using only daily reference evapotranspiration data as an input parameter, was developed. It calculates crop transpiration and soil evaporation based on ground cover and daily radiation intercepted by the canopy. The model uses a two-stage soil evaporation method adapted to conditions of variable reference evapotranspiration. The model was evaluated against data using measurements from two seasons of lettuce crop, two tomato fields in the same season, and one season of broccoli crop production. Using all of the crop data, the root-mean-square error for measured versus modelled daily ETc was 0.72 mm/day, indicating that the model works well
Abstract: In an arid environment, the effect of evaporation on energy balance can affect air temperature recordings and greatly impact on degree-day calculations. This is an important consideration when choosing a site or climate data for phenological models. To our knowledge, there is no literature showing effect of the underlying surface and its fetch around a weather station on degree-day accumulation. In this paper, we present data to show that this is a serious consideration, and it can lead to dubious models. Microscale measurements of temperature and energy balance are presented to explain why the differences occur. For example, the effect of fetch of irrigated grass and wetting of bare soil around a weather station on diurnal temperature are reported. A 43-day experiment showed that temperature measured on the upwind edge of an irrigated grass area averaged 4% higher than temperatures recorded 200 m inside the grass field. When the single-triangle method was used with a 10°C threshold and starting on May 19, the station on the upwind edge reached 900 degree-days on June 28, whereas the interior station recorded 900 degree-days on July 1. Clearly, a difference in fetch can lead to big errors for large degree-day accumulations. Immediately after wetting, the temperature over a wet soil surface was similar to that measured over grass. However, the temperature over the soil increased more than over the grass as the soil surface dried. Therefore, the observed difference between temperatures measured over bare soil and those over grass increases with longer periods between wettings. In most arid locations, measuring temperature over irrigated grass gives a lower mean annual temperature, resulting in lower annual cumulative degree-day values. This was verified by comparing measurements over grass with those over bare soil at several weather stations in a range of climates. To eliminate the effect of rainfall frequency, using temperature data collected only over irrigated grass is recommended for long-term assessment of climate change effects on degree-day accumulation. In high evaporative conditions, a fetch of at least 100 m of grass is recommended. Our results clearly indicate that weather stations sited over bare soil are not transferable to those based on temperature recorded over irrigated grass. At a minimum, all degree-day-based phenology models reported in the literature should clearly describe the weather station site.
Abstract: A convenient and stable method for expressing crop seed growth is important both in experimental and simulation studies. The conventional approach has been to measure the seed growth rate (SGR) of individual seeds and multiply this by the number of seeds per unit ground area. An alternative to measurements of SGR has emerged from the observation that during seed growth, harvest index (NI) increases linearly over time. The objective of this study was to examine and compare SGR and dHI/dt as the appropriate description of crop seed growth on the basis of 22 data sets representing four crop species for which there were intensive measures of seed gros th and HI. Seed growth was analyzed by linear, quadratic, cubic, and logistic models, in regression analysis. These analyses showed that SGR and dHI/dt were not constant for the entire seed growth period. However, constant values for these two measures of seed growth Here statistically equivalent to a cubic function of seed growth for much of the seed growth period. A linear increase in SGR and dHI/dt was found to be statistically appropriate when seed weight and harvest index were increasing from 10 to 90% of their maximum value. It was Found in comparisons of the coefficients of variability that the stability of dHI/dt was greater than for SGR for individual cultivars grown under a range of conditions. Overall, this analysis indicated that a constant dHI/dt is an attractive approach for expressing crop seed growth.
Abstract: An open-air experiment was performed in Pistoia (Italy) to investigate the possible protective role played by different contents of UV-B absorbing compounds to realistic UV-B supplementation and to study its effect on plant fruit production. A mutant line and its normal counterpart of Lycopersicon esculentum Mill, which differ in the content of UV-B absorbing compounds, were used. Additional UV-B radiation in the field was supplied to simulate a 20% stratospheric ozone depletion. Two groups of plants were grown: ‘control’, where plants received only natural solar UV-B radiation, and ‘UV-B’ treatment, where plants were grown under supplemental UV-B.
The results of the experiment showed that the content of UV-B absorbing compounds of treated plants did not differ from that of the control in both lines. This indicates that natural sunlight, in Mediterranean areas, is saturating for synthesis of these compounds also in plants with normal content of UV-B absorbing compounds. Consequently, plants are not able to produce significant additional amounts of them, in response to a realistic UV-B supplementation, in order to protect the plant from additional UV-B radiation.
No different responses to the UV-B supplementation were found between the two lines. The most significant UV-B effect was an earlier reddening of fruits in comparison with the ‘control’ accompanied by a reduction in the size of mature fruits. No significant effects of UV-B treatment were observed in biomass accumulation, leaf ontogeny, flowering or productivity.
Abstract: The objectives of this paper are to: (1) present 10 years of phenological data for nine natural species growing in a Mediterranean-type climate, (2) present threshold temperatures that were derived for the computation of cumulative degree-days (CDD), and (3) evaluate the sensitivity of the nine natural species to weather variability. The study was conducted at the Phenological Research Garden of Oristano, Sardinia, Italy, during the period 1986–96. The observations were made on five typical Mediterranean species and four species that are typical of higher latitudes. The mean annual pattern of phenological events and the CDD from 1 January are given for each development stage. Temperature thresholds were evaluated by comparing the standard deviation about the mean number of days in the development period for each species. A good relationship between timing of phenophase occurrence and temperature was observed for the Mediterranean species, which were little affected by variations in rainfall. Phenological development of the non-native species was affected by springtime rainfall.
Abstract: A transient electrochemical reactivity test is proposed for anodised Al, based on the cathodic control during the failure of the protective layers. The method is meant to identify failure modes and to rank samples treated with different processes and products. The method consists of imposing a cathodic constant current density for a given time, to which a fast cathodic amperostatic step follows; the observed overvoltage transients are modelled with an equivalent circuit: the parallel of the oxide layer time dependent resistance R-t(a) and a pseudo-capacitance C. The general features of overvoltage transients are: (i) a maximum after <1 ms because surface is etched with possible formation of tiny pits, when pits become large and passing maxima disappear; (ii) R tends to decrease with the extent of cathodic attack: higher R values are displayed by electrobrightened samples; (iii) C is initially constant and grows after a critical attack time: electrocoloured and electrobrightened samples show higher and lower C values, respectively; (iv) a increases with the extent of cathodic attack. The electrochemical parameters can be correlated to the surface aspect of anodised samples: pit-free starting surfaces correlate with high R and low C values, even distributions of tiny pits correlate with decreasing R, severely etched surfaces with large pits and when Al surface is attained R becomes low and C high. The best performing layers are those electrobrightened before anodisation: they display highly resistive oxides and are not lean to the formation of large pits (typical pits are in the micron range).
Abstract: Plants show different levels of sensitivity to ultraviolet-B (UV-B) radiation and acclimation to high UV-B irradiances had been developed in many species. A field experiment was performed during 1995 to study the adaptive responses of oak plants (Quercus robur L.) to artificial UV-B supplementation.
The most important effect of UV treatment was the increase in leaf thickness and the accumulation of phenolic compounds in the secondary wall of the adaxial epidermis of leaves in UV treated plants; the secondary wall of cells in the abaxial epidermis, while plant morphology was sensible to UV treatment.
Abstract: A FACE (Free Air CO2 Enrichment) experiment was carried out on Potato (Solanum tuberosum L., cv. Primura) in 1995 in Italy. Three FACE rings were used to fumigate circular field plots of 8 m diameter while two rings were used as controls at ambient CO2 concentrations. Four CO2 exposure levels were used in the rings (ambient, 460, 560 and 660 mu mol mol-l). Phenology and crop development, canopy surface temperature, above-and below-ground biomass were monitored during the growing season. Crop phenology was affected by elevated CO2, as the date of flowering was progressively anticipated in the 660, 560, 460 mu mol mol(-1) treatments. Crop development was not affected significantly as plant height, leaf area and the number of leaves per plant were the same in the four treatments. Elevated atmospheric CO2 levels had, instead, a significant effect on the accumulation of total nonstructural carbohydrates (TNC = soluble sugars + starch) in the leaves during a sunny day. Specific leaf area was decreased under elevated CO2 with a response that paralleled that of TNC concentrations. This reflected the occurrence of a progressive increase of photosynthetic rates and carbon assimilation in plants exposed to increasingly higher levels of atmospheric CO2. Tuber growth and final tuber yield were also stimulated by rising CO2 levels. When calculated by regression of tuber yield vs. the imposed levels of CO(2)concentration, yield stimulation was as large as 10% every 100 mu mol mol(-1) increase, which translated into over 40% enhancement in yield under 660 mu mol mol(-1). This was related to a higher number of tubers rather than greater mean tuber mass or size. Leaf senescence was accelerated under elevated CO2 and a linear relationship was found between atmospheric CO2 levels and leaf reflectance measured at 0.55 mu m wavelength. We conclude that significant CO2 stimulation of yield has to be expected for potato under future climate scenarios, and that crop phenology will be affected as well.
Abstract: During the last few decades many experiments have been performed to evaluate the responses of plants to enhanced solar UV-B radiation (280–320 nm) that may occur because of stratospheric ozone depletion; most of them were performed in controlled environment conditions where plants were exposed to low photosynthetically active radiation (PAR) levels and high UV-B irradiance. Since environmental radiative regimes can play a role in the response of plants to UV-B enhancement, it appears doubtful whether it is valid to extrapolate the results from these experiments to plants grown in natural conditions. The objective of this work was to evaluate the effects on physiology and morphology of a bean (Phaseolus vulgaris L.) cultivar Nano Bobis, exposed to supplemental UV radiation in the open-air. UV-B radiation was supplied by fluorescent lamps to simulate a 20% stratospheric ozone reduction. Three groups of plants were grown: control (no supplemental UV), UV-A treatment (supplementation in the UV-A band) and UV-B treatment (supplemental UV-B and UV-A radiation). Each group was replicated three times. After 33 days of treatment plants grown under UV-B treatment had lower biomass, leaf area and reduced leaf elongation compared to UV-A treatment. No significant differences were detected in photosynthetic parameters, photosynthetic pigments and UV-B absorbing compounds among the three groups of plants. However, plants exposed to UV-A treatment showed a sort of ''stimulation'' of their growth when compared to the control. The results of this experiment showed that plants may be sensitive to UV-A radiation, thus it is difficult to evaluate the specific effects of UV-B (280–320 nm) radiation from fluorescent lamps and it is important to choose the appropriate control. Environmental conditions strongly affect plant response to UV radiation so further field studies are necessary to assess the interaction between UV-B exposure and meteorological variability.
Abstract: Bidirectional reflectance factors (BRFs) of crop stands are strongly influenced by canopy architecture. In wheat, as well as in many other crops, canopy architecture changes dramatically with the phenological development of the plant community.
A ground-based experiment was performed to examine the effect of panicles of winter wheat (Triticum aestivum L.) at the flowering stage on canopy BRFs. Reflectance factors were measured in the field with a portable radiometer in the red (0-63-0-69 μm) and near-infrared (0-76-0-90 μm) wavelength intervals. Observations were made at three viewing angles and 14 solar zenith angles during two consecutive days on a control target and on a target where panicles had been removed.
Panicles did not contribute significantly to the red nor to the near-infrared (NIR) reflectance factors computed from nadir observations. Off-nadir NIR reflectance was also not altered by the presence of panicles, but was moderately sensitive to illumination angle. Off-nadir red reflectance in the backscattcring direction was higher in the canopy with panicles than in the canopy without panicles: at a solar zenith angle of about 50° the difference in the reflectance of the two targets reached a maximum of about 39 per cent.
These findings imply a potential to identify crops and their phenological development by more fully exploiting reflectance at several different viewing and solar angles.
