Sun Z.,University of Connecticut |
Gebremichael M.,University of Connecticut |
Ardo J.,Lund University |
Nickless A.,South African Council for Scientific and Industrial Research |
And 4 more authors.
Atmospheric Research | Year: 2012
Most existing remote sensing-based evapotranspiration (ET) algorithms rely exclusively on polar-orbiting satellites with thermal infrared sensors, and therefore the resulting ET values represent only "instantaneous or snapshot" values. However, daily ET is more meaningful and useful in applications. In this study, daily ET estimates are obtained by combining data from the MODIS sensor aboard the polar-orbiting Terra satellite and the SEVIRI sensor aboard the geostationary-orbiting MSG satellite. The procedure consists of estimating the instantaneous evaporative fraction (EF) based on the MODIS/Terra land data products, and estimating the daily net radiation and daily available energy based on the 30-min SEVIRI/MSG data products. Assuming constant EF during the daytime, daily ET is estimated as the product of the SEVIRI/MSG-based daily available energy and MODIS/Terra-based instantaneous EF. The daily ET estimates are evaluated against flux tower measurements at four validation sites in Africa. Results indicate that the synergistic use of SEVIRI/MSG and MODIS/Terra has the potential to provide reliable estimates of daily ET during wet periods when daily ET exceeds 1. mm/day. The satellite-based daily ET estimates however tend to underestimate ET by 13% to 35%. The daily ET estimation algorithm can further be improved by incorporating a temporal data-filling interpolation technique to estimate the unavailable net radiation information during cloudy sky conditions, and by improving the accuracy of the instantaneous EF. The assumption of constant evaporative fraction during the daytime is reasonable, and does not result in substantial errors in the daily ET estimates. © 2012 Elsevier B.V.
van Wesemael B.,Catholic University of Louvain |
Paustian K.,Colorado State University |
Andren O.,Swedish University of Agricultural Sciences |
Cerri C.E.P.,University of Sao Paulo |
And 9 more authors.
Plant and Soil | Year: 2011
As regional and continental carbon balances of terrestrial ecosystems become available, it becomes clear that the soils are the largest source of uncertainty. Repeated inventories of soil organic carbon (SOC) organized in soil monitoring networks (SMN) are being implemented in a number of countries. This paper reviews the concepts and design of SMNs in ten countries, and discusses the contribution of such networks to reducing the uncertainty of soil carbon balances. Some SMNs are designed to estimate country-specific land use or management effects on SOC stocks, while others collect soil carbon and ancillary data to provide a nationally consistent assessment of soil carbon condition across the major land-use/soil type combinations. The former use a single sampling campaign of paired sites, while for the latter both systematic (usually grid based) and stratified repeated sampling campaigns (5-10 years interval) are used with densities of one site per 10-1,040 km2. For paired sites, multiple samples at each site are taken in order to allow statistical analysis, while for the single sites, composite samples are taken. In both cases, fixed depth increments together with samples for bulk density and stone content are recommended. Samples should be archived to allow for re-measurement purposes using updated techniques. Information on land management, and where possible, land use history should be systematically recorded for each site. A case study of the agricultural frontier in Brazil is presented in which land use effect factors are calculated in order to quantify the CO2 fluxes from national land use/management conversion matrices. Process-based SOC models can be run for the individual points of the SMN, provided detailed land management records are available. These studies are still rare, as most SMNs have been implemented recently or are in progress. Examples from the USA and Belgium show that uncertainties in SOC change range from 1.6-6.5 Mg C ha-1 for the prediction of SOC stock changes on individual sites to 11.72 Mg C ha-1 or 34% of the median SOC change for soil/land use/climate units. For national SOC monitoring, stratified sampling sites appears to be the most straightforward attribution of SOC values to units with similar soil/land use/climate conditions (i. e. a spatially implicit upscaling approach). © 2010 Springer Science+Business Media B.V.
Freibauer A.,Institute of Agricultural Climate Research |
Mathijs E.,Catholic University of Leuven |
Brunori G.,University of Pisa |
Damianova Z.,Programme Director Innovation Programme Applied Research and Communications Fund |
And 4 more authors.
EuroChoices | Year: 2011
Sustainable Food Consumption and Production in a Resource-constrained World This article summarises the findings of the Third Foresight Exercise organised by the EU Standing Committee on Agriculture Research (SCAR). The challenges ahead for the European agri-food system differ in their complexity, scale and speed to those we have faced in the past, pointing to a new level of change. The interconnections between these combined challenges and the limited understanding of the various feedback loops linking them, contribute to uncertainty about future developments. There is growing evidence, however, that these challenges are so large that a 'business-as usual' approach is not an option and that transformative change is needed which will open up a window for innovation, new ideas and new paradigms. Three pathways have been identified to guide the transition to a sustainable agri-food system: consumption changes, technological innovation and organisational innovation. To make the transition successful, research and innovation programmes should be transformed in order to tackle these challenges and to produce the necessary system innovations. Diversity of approaches and paradigms, transdisciplinarity, experimentation in both the technological and social realm and coordination should be promoted in the design of the research and innovation programmes. © 2011 The Agricultural Economics Society and the European Association of Agricultural Economists.
Anderson T.-H.,Institute of Agroecology |
Anderson T.-H.,Institute of Agricultural Climate Research |
Martens R.,Institute of Agroecology |
Martens R.,Institute of Biodiversity
Soil Biology and Biochemistry | Year: 2013
We attempted to quantify microbial growth in soil by means of DNA determination after glucose amendment. An FDNA conversion factor of 5.0 was used to convert μg DNA g-1 soil to μg Cmic g-1 soil during the growth phase. The conversion factor acquired rested on a regression analysis between soil microbial biomass-C (Cmic) estimated by the substrate-induced respiration technique (SIR) and dsDNA using a modified, miniaturized dsDNA extraction procedure which included 44 field and forest soils with a coefficient of determination of r2 = 0.95. Verification of this conversion factor was tested on eight arable soils where Cmic was determined by substrate-induced respiration (SIR)-, chloroform fumigation-incubation (CFI)-, chloroform fumigation-extraction (CFE)-, and application of the FDNA conversion factor. The congruency between the Cmic values obtained through these different techniques was satisfactory since five of eight soils gave similar Cmic values which were not statistically significantly different. The soils were thereafter amended with glucose and microbial growth followed by Cmic determinations with CFI, CFE, and DNA conversion over a period of up to 264 h at 22 °C. Concomitant CO2 analyses gave clues to two kinds of growth processes with respect to speed. Based on DNA conversion the calculated traditional growth parameters such as the specific growth rate (μ) lay in the range between 0.0046 and 0.022 h-1 which is several fold slower than μ values based on CO2 conversion but are in accordance with data in the earlier literature on growth rates for bacteria and fungi in soil done with traditional plate counts. These results suggest that DNA determinations can be applied as an alternative index for growth studies in situ. © 2012 Elsevier Ltd.
Anderson T.-H.,Institute of Agroecology |
Anderson T.-H.,Institute of Biodiversity |
Heinemeyer O.,Institute of Agroecology |
Heinemeyer O.,Institute of Agricultural Climate Research |
And 2 more authors.
Soil Biology and Biochemistry | Year: 2011
In soil ecology, microbial parameters have been identified as sensitive indicators of changes in the soil environment. The Braunschweig FACE project provided the opportunity to study the effects of elevated CO2 (550 μmol mol-1) as compared to ambient CO2 (370 μmol mol-1) on total microbial biomass (Cmic), Cmic-to-Corg ratio and the fungal-to-bacterial respiratory ratio together with total Corg, Nt, C:N ratio and pH over a six-year period. Field management followed a typical crop rotation system of this region with either a crop-related full nitrogen supply (N100) or 50% reduced N supply (N50). The soil microbial parameters responded to the elevated CO2 treatment in varying intensities and time spans. The fungal-to-bacterial respiratory ratio was the most sensitive parameter in responding to an elevated CO2 treatment with highly significant differences to ambient CO2-treated control plots in the third year of CO2 fumigation. After six years bacterial respiratory activity had increased in ascending order to 34% in FACE-treated plots (N50 and N100) as compared to control plots. Soil microbial biomass (Cmic) responded more slowly to the FACE treatment with highly significant increases of >12% after the fourth year of CO2 fumigation. The Cmic-to-Corg ratio responded very late in the last two years of the CO2 treatment with a significant increase of >7.0% only in the N100 variant. Total Corg and Nt were slightly but significantly increased under FACE around 10.0% with ascending tendency over time starting with the second year of CO2 treatment. No significant FACE effects could be recorded for the C:N ratio or pH.These results suggest that under FACE treatment changes in the soil microbial community will occur. In our study the fungal-to-bacterial respiratory ratio was superior to total Cmic as microbial bioindicators in reflecting changes in the soil organic matter composition. © 2011 Elsevier Ltd.