  Management effects on net ecosystem carbon and GHG budgets at European crop sites; ; et al in Geophysical Research Abstracts (2011, April 08), 13 Detailed reference viewed: 83 (10 ULg) The carbon balance of European croplands: A cross-site comparison of simulation models; ; et al in Agriculture, Ecosystems & Environment (2010), 139(3), 419-453 Croplands cover approximately 45% of Europe and play an important role in the overall carbon budget of the continent. However, the estimation of their carbon balance remains uncertain due to the diversity ... [more ▼] Croplands cover approximately 45% of Europe and play an important role in the overall carbon budget of the continent. However, the estimation of their carbon balance remains uncertain due to the diversity of crops and cropping systems together with the strong influence of human management. Here, we present a multi-site model comparison for four cropland ecosystem models namely theDNDC,ORCHIDEESTICS, CERES-EGC and SPA models. We compare the accuracy of the models in predicting net ecosystem exchange (NEE), gross primary production (GPP), ecosystem respiration (Reco) as well as actual evapotranspiration (ETa) for winter wheat (Triticum aestivum L.) and maize (Zea mays L.) derived from eddy covariance measurements on five sites along a gradient of climatic conditions from eastern to southwesterly Europe. The models are all able to simulate daily GPP. The simulation results for daily ETa and Reco are, however, less accurate. The resulting simulation of daily NEE is adequate except in some cases where models fail due to a lack in phase and amplitude alignment. ORCHIDEE-STICS and PAshowthe best performance. Nevertheless, they are not able to simulate full crop rotations or the multiple management practices used. CERES-EGC, and especially DNDC, although exhibiting a lower level of model accuracy, are able to simulate such conditions, resulting in more accurate simulation of annual cumulative NEE. [less ▲] Detailed reference viewed: 58 (2 ULg)Measurements necessary for assessing the net ecosystem carbon budget of croplands; ; et al in Agriculture, Ecosystems & Environment (2010), 139(3), 302-315 There are a number of methods that can be used to help assess carbon budgets at the site to continental scales. Eddy covariance (EC) networks have been developed over the last decade and have been used to ... [more ▼] There are a number of methods that can be used to help assess carbon budgets at the site to continental scales. Eddy covariance (EC) networks have been developed over the last decade and have been used to make many advances in our understanding. However, eddy covariance measurements of CO2 and water vapour exchanges quantify the fluxes only on short time scales, but do not assess the impacts of long-term processes that contribute to biogeochemical cycling in croplands, such as harvest or residue removal and other management practices, so many other supplementary measurements are required to attribute different components of the carbon flux. Such methods include isotope studies, chamber flux measurements of C and other greenhouse gases, inventories of above- and below-ground biomass as well as management in- and outputs, book-keeping modelling, process modelling, experimental manipulation and earth observation (e.g. remote sensing). In this review, we summarise the component fluxes that make up the total cropland carbon budget, describe the key fluxes and methods used to estimate them, and examine how they need to be integrated to obtain the net ecosystem carbon budget of European croplands. We describe the uncertainties and difficulties inherent at each stage and how these can be minimised. [less ▲] Detailed reference viewed: 25 (1 ULg) |
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