Papers by kristof vanoost
At the scale of hillslopes, a detailed mechanistic understanding of the processes controlling OC ... more At the scale of hillslopes, a detailed mechanistic understanding of the processes controlling OC stabilization is still lacking. Here, we aimed to study the impact of geomorphic and pedogenic processes on the distribution of OC quality (ability of OC to release carbon dioxide through metabolic pathways) along an agricultural hillslope in the Belgian loess belt. We collected soil cores at four topographic positions along the hillslope (summit, convex shoulder, backslope and footslope). We assessed (i) cumulative soil erosion using diagnostic soil horizons and the 137 Cs techniques, (ii) OC stocks and its quality (NaOCl-resistant OC), and (iii) reactive soil mineral phases (concentration of Fe, Al and Si in specific oxalate and dithionite-citrate-bicarbonate extractants). Our results show that ongoing erosion has resulted in a small amount of reactive soil phases (e.g. Fe and Al-oxyhydroxides) in the upper first meter of the most eroded soil profile (backslope position). The erosion observations show that this is related to the truncation and rejuvenation of the backslope soil profile by bringing unweathered and calcareous loess to the soil surface. As a consequence, the potential of soil to stabilize OC by molecular interactions with soil minerals is substantially reduced by erosion when calcareous loess is reached. This was supported by the observed amount of mineral-protected OC (using NaOCl-resistant OC as an indicator) which was significantly lower at the eroded midslope than at the other slope positions. The combined effect of geomorphic and pedogenic processes thus strongly impacts the distribution of soil OC quality along the hillslope. We observed a spatial differentiation of the labile OC pool (i.e. the OC not resistant to NaOCl) along the hillslope with a significant enrichment at the depositional site. The labile OC pool contributed 64 ± 5%, 69 ± 5%, 40 ± 22% and 49 ± 6% of total OC at the footslope, backslope, convex shoulder and summit, respectively. Despite the fact that a part of this high labile OC stock at the footslope (5.8 ± 0.2 kg OC m −2 ) can be protected from microbial degradation due to specific environmental conditions, our results suggest that a large part of this depositional OC stock has a high potential for mineralization given its quality.
1] Sediments mobilized by interrill erosion are often highly enriched in soil organic carbon (SOC... more 1] Sediments mobilized by interrill erosion are often highly enriched in soil organic carbon (SOC) in comparison to source soils. This selectivity may lead to the preferential mobilization of SOC with specific properties, e.g., SOC that is especially susceptible to decomposition. This may then have important implications with respect to the role of soil erosion in the global carbon cycle. We addressed this issue by investigating the behavior of different SOC components in field rainfall simulation experiments on arable fields in loess-derived soils. We characterized the mobilization of mineral-bound organic carbon (MOC) and particulate organic carbon (POC) by interrill erosion using size fractionation and we used the C:N ratio as a tracer variable to determine the composition of the SOC in eroded sediments. MOC was found to be preferentially mobilized by interrill erosion in comparison to POC. The enrichment ratio (i.e., the ratio of the concentration of a soil constituent in the eroded sediment to its concentration in the original soil) of MOC decreased with increasing sediment concentration. The enrichment ratio of POC displayed a similar pattern to that of MOC but enrichment was less pronounced. Furthermore, sediments were found to be enriched in fine POC while they were impoverished with respect to coarse POC. The selective MOC mobilization together with the dominance of MOC in the total SOC pool in the soil explained the dominance of MOC in interrill eroded sediment. The fact that it is mainly MOC that is mobilized by interrill erosion implies that the SOC in the interrill eroded sediments is on average at least as recalcitrant than that in the source soils which may have important implications for the fate of the mobilized SOC. In order to understand the role of soil erosion in C cycling, MOC and POC need to be considered separately not only because they are chemically different but also because of their different behaviors with respect to geomorphic processes.
Soil erosion rates in cultivated areas have intensified during the last decades leading to both o... more Soil erosion rates in cultivated areas have intensified during the last decades leading to both on and off-site problems for farmers and rural communities. Furthermore, soil redistribution processes play an important role in sediment and carbon storage within, and exports from, cultivated catchments. This study focuses on the impact of land consolidation and changes in landscape structure on medium term soil erosion and landscape morphology within a 3.7-ha field in France. The area was consolidated in 1967 and we used the 137 Cs-technique to quantify soil erosion for the period ). We measured the 137 Cs inventories of 68 soil cores sampled along transects covering the entire area and especially specific linear landforms located along both present and past field borders (i.e., lynchets and undulations landforms, respectively). These results were then confronted with the outputs of a spatially-distributed 137 Cs conversion model that simulates and discriminates soil redistribution induced by water and tillage erosion processes. Our results showed that tillage processes dominated the soil redistribution in our study area for the last 55 years and generated about 95% (i.e., 4.50 Mg·ha −1 ·yr − 1) of the total gross erosion in the field. Furthermore, we demonstrated that soil redistribution was largely affected by the presence of current and also former field borders, where hotspots areas of erosion and deposition (>20 Mg·ha −1 ·yr −1 ) were concentrated. Land consolidation contributed to the acceleration of soil erosion through the conversion of depositional areas into sediment generating areas. Although the conversion model was able to reproduce the general tendencies observed in the patterns of 137 Cs inventories, the model performance was relatively poor with a r 2 of 0.20. Discrepancies were identified and associated with sampling points located along the current field borders. Our data suggests that tillage erosion processes near field boundaries cannot be described as a typical diffusive process. These processes near field boundaries should be characterised and taken into account in a future version of the model to accurately simulate rates and patterns of past soil redistribution in fragmented cultivated hillslopes. We also showed that the use of an accurate DEM resulting from LIDAR data, based on present-day topography, leads to the underestimation of soil redistribution rates by the model, especially in this landscape submitted to recent and important morphological changes. Our results have important implications for the simulation of tillage erosion processes and our understanding of soil redistribution processes in complex cultivated areas. This is of particular interest to improve our knowledge and prediction of patterns of soil physical parameters, such as carbon storage or water content, particularly sensitive to surface erosion and landscape structuration.
The effects of soil redistribution on the carbon (C) cycle and the need for spatially and depth-e... more The effects of soil redistribution on the carbon (C) cycle and the need for spatially and depth-explicit C estimates at large scales have recently been receiving growing attention. In eroding agricultural landscapes, C gets transported from erosional to depositional landscape elements forming a heterogeneous pattern in quantity and quality of the distributed carbon. At present, methods and research to characterize this horizontal and vertical variability are either limited to local slope scales or, if applied to larger scales, to surface soil horizons with large uncertainties when extrapolated to deeper layers. In this study, we used soil profile data collected in two zones of differing soil texture (loam and clay-rich soils) in Luxembourg, to calibrate a linear mixed-effect model to predict the 3D soil C stock distribution on a regional scale for cropping systems using a set of spatially-explicit hydrologic, climatic, pedologic and geomorphologic variables. We demonstrate that due to a high spatial variability of C stocks it is mandatory to consider various environmental processes to predict C accurately on a regional scale, especially in deeper soil layers, and to avoid simple depth extrapolation of topsoil C data as has been done earlier in flat landscapes. Using estimates of topsoil C contents derived from hyperspectral remote sensing, we predict spatial patterns of C stocks for cropland on a regional scale and provide new insights into the spatial heterogeneity of soil C storage covering a large area. The variability of C stocks in the two texture zones expressed as values larger or smaller than the mean ± standard deviation is hereby lower in the loam zone (26.2%) than in the clay zone (38.7%). We estimate a mean C stock (to 100 cm soil depth) of 9.4 ± 3.1 kg/m 2 for the clay-rich soils and 11.3 ± 2.4 kg/m 2 for loamy soils. This represents the first regional estimate for C stocks for the research area using continuous spatial explicit datasets.
Carbon exchange associated with accelerated erosion following land cover change is an important c... more Carbon exchange associated with accelerated erosion following land cover change is an important component of the global C cycle. In current assessments, however, this component is not accounted for. Here, we integrate the effects of accelerated C erosion across point, hillslope, and catchment scale for the 780-km 2 Dijle River catchment over the period 4000 B.C. to A.D. 2000 to demonstrate that accelerated erosion results in a net C sink. We found this longterm C sink to be equivalent to 43% of the eroded C and to have offset 39% (17-66%) of the C emissions due to anthropogenic land cover change since the advent of agriculture. Nevertheless, the erosion-induced C sink strength is limited by a significant loss of buried C in terrestrial depositional stores, which lagged the burial. The time lag between burial and subsequent loss at this study site implies that the C buried in eroded terrestrial deposits during the agricultural expansion of the last 150 y cannot be assumed to be inert to further destabilization, and indeed might become a significant C source. Our analysis exemplifies that accounting for the nonsteady-state C dynamics in geomorphic active systems is pertinent to understanding both past and future anthropogenic global change.
This research investigates the impact of human activities on carbon (C) dynamics in a mountainous... more This research investigates the impact of human activities on carbon (C) dynamics in a mountainous and semi-arid environment. Despite the low C status of drylands, soil organic carbon (SOC) is the largest C pool in these systems and therefore may offer significant C sequestration potential in systems recovering from degradation. Nevertheless, quantification of this potential is limited by lack of knowledge concerning the magnitude of and controls on regional SOC stocks. Therefore, this study aimed to (i) investigate the variability of soil organic carbon in relation to recovery period and key soil and topographical variables, and (ii) quantify the effects of recovery period following abandonment on SOC stocks. Soil profiles were sampled in the Sierra de los Filabres (southeast Spain) in different land units along geomorphic and degradation gradients. SOC contents were modelled using recovery period and soil and topographical variables. Sample depth, topographic position, altitude, recovery period and stone content were identified as the main factors for predicting SOC concentrations. SOC stocks in 1 m depth of soil varied between 3.16 and 76.44 t/ha. Recovery period (years since abandonment), topographic position and altitude were used to predict and map SOC stocks in the top 0.2 m. The results show that C accumulates rapidly during the first 10-50 yr following abandonment; thereafter, the stocks evolve towards a steady-state level. The erosion zones in the study area demonstrate greater potential to increase their SOC stocks when abandoned. Deposition zones have greater SOC values, although their C accumulation rate is lower compared with erosional landscapes in the first 10-50 yr following abandonment. Therefore, full understanding of the C sequestration potential of land use change in areas of complex topography requires knowledge of spatial variability in soil properties and in particular SOC.
Recent studies have highlighted the tight coupling between geomorphic processes and soil carbon (... more Recent studies have highlighted the tight coupling between geomorphic processes and soil carbon (C) turnover and suggested that eroding landscapes can stabilize more C than their non-eroding counterparts. However, large uncertainties remain and a mechanistic understanding of geomorphic effects on C storage in soils is still lacking. Here, we quantified the soil organic carbon (SOC) stock and pool distribution along geomorphic gradients and combined data derived from soil organic matter fractionation and incubation experiments. The size and composition of the SOC pools were strongly related to geomorphic position: 1.6 to 6.2 times more C was stabilized in the subsoils (25-100cm) of depositional profiles than in those of eroding profiles. Subsoil C of depositional profiles is predominantly associated with microaggregates and silt-sized particles which are associated with pools of intermediate stability. We observed a significantly higher mean residence time for the fast and intermediate turnover pools of buried C at depositional positions, relative to non-eroding and eroding positions, resulting from the physical protection of C associated with microaggregates and silt particles. Conversely, significant amounts of C were replaced at eroding positions but the lower degree of decomposition and the lack of physically protected C, resulted in higher respiration rates. By considering C cycling at non-eroding, eroding and depositional positions, we found that the eroding landscapes studied store up to 10% more C due to soil redistribution processes than non-eroding landscapes. This is the result of the stabilization of C in former subsoil at eroding positions and partial preservation of buried C in pools of intermediate turnover at depositional positions. However, the sink strength was limited by significant losses of buried C as only a small fraction of the C was associated with stable pools.
Reliable quantitative data on the extent and rates of soil erosion are needed to understand the g... more Reliable quantitative data on the extent and rates of soil erosion are needed to understand the global significance of soil-erosion induced carbon exchange and to underpin the development of science-based mitigation strategies, but large uncertainties remain. Existing estimates of agricultural soil and soil organic carbon (SOC) erosion are very divergent and span two orders of magnitude. The main objective of this study was to test the assumptions underlying existing assessments and to reduce the uncertainty associated with global estimates of agricultural soil and SOC erosion. We parameterized a simplified erosion model driven by coarse global databases using an empirical database that covers the conterminous USA. The good agreement between our model results and empirical estimates indicate that the approach presented here captures the essence of agricultural erosion at the scales of continents and that it may be used to predict the significance of erosion for the global carbon cycle and its impact on soil functions. We obtained a global soil erosion rate of 10.5 Mg ha -1 y -1 for cropland and 1.7 Mg ha -1 y -1 for pastures. This corresponds to SOC erosion rates of 193 kg C ha -1 y -1 for cropland and 40.4 kg C ha -1 y -1 for eroding pastures and results in a global flux of 20.5 (AE10.3) Pg y -1 of soil and 403.5 (AE201.8) Tg C y -1 . Although it is difficult to accurately assess the uncertainty associated with our estimates of global agricultural erosion, mainly due to the lack of model testing in (sub-)tropical regions, our estimates are significantly lower than former assessments based on the extrapolation of plot experiments or global application of erosion models. Our approach has the potential to quantify the rate and spatial signature of the erosion-induced disturbance at continental and global scales: by linking our model with a global soil profile database, we estimated soil profile modifications induced by agriculture. This showed that erosion-induced changes in topsoil SOC content are significant at a global scale (an average SOC loss of 22% in 50 years) and agricultural soils should therefore be considered as dynamic systems that can change rapidly. Figure 3. Scatter plots of water erosion estimates derived from the Cerdan et al. (2010) study and modelled estimates for European cropland. Data is aggregated on a regular grid, using the mean HUC4 area estimate for the conterminous USA (i.e. 193 km  193 km). 648 S. DOETTERL, K. VAN OOST AND J. SIX
This study addressed long-term land degradation and regeneration effects on soil organic carbon (... more This study addressed long-term land degradation and regeneration effects on soil organic carbon (SOC) composition. This was done in a context of secondary succession following land abandonment in the Mediterranean region of SE Spain. The effects of land use change and soil erosion on SOC composition were studied by using lignin as a biomarker. To get insight into the evolution of SOC composition along a land use and topographical gradient, differences in lignin contribution to SOC were determined at different soil depths (0-0.1 m, 0.1-0.2 m, 0.2-0.3 m). Three deposition locations, three positions on the hillslope and three zones on top of the hillslope (shoulder) were selected on croplands and fields that were abandoned since 10 and 50 years, respectively. Land use change was identified as a driver for the observed gradients in lignin, SOC and N in these semi-arid ecosystems. Abandoned sites were highest in soil lignin, which could be related to the higher lignin input. For deposition and shoulder positions lignin was less degraded at abandoned sites compared to cultivated sites. On croplands lignin was more degraded at hillslope locations compared to deposition zones. Observed differences in soil lignin quantity were highest for the topsoil (0-0.1 m). For deeper soil, differences are less pronounced. However, no differences were evident for lignin contribution to SOC (mg lignin phenols/g SOC). As modern soil erosion rates are very low in the study area, SOC composition on abandoned fields may be more influenced by present day vegetation and its degradation than by soil erosion. Surprisingly, lignin contribution to SOC was not favored by vegetation recovery either. The higher soil N contents for abandoned fields compared to croplands might explain why lignin is not preferentially preserved on recovered sites.
Modeling of biosphere-atmosphere exchange of greenhouse gases -Model-based biospheric greenhouse ... more Modeling of biosphere-atmosphere exchange of greenhouse gases -Model-based biospheric greenhouse gas balance of Hungary. In: Atmospheric Greenhouse Gases: The Hungarian Perspective (Ed.: Haszpra, L.), pp. 295-330 296 Z. Barcza et al.
Soil redistribution on arable land significantly affects lateral and vertical soil carbon (C) flu... more Soil redistribution on arable land significantly affects lateral and vertical soil carbon (C) fluxes (caused by C formation and mineralization) and soil organic carbon (SOC) stocks. Whether this serves as a (C) sink or source to the atmosphere is a controversial issue. In this study, the SPEROS-C model was modified to analyse erosion induced lateral and vertical soil C fluxes and their effects upon SOC stocks in a small agricultural catchment (4Á2 ha). The model was applied for the period between 1950 and 2007 covering 30 years of conventional tillage followed by 28 years of conservation tillage . In general, modelled and measured SOC stocks are in good agreement for three observed soil layers. The overall balance of erosion induced lateral and vertical C fluxes results in a C loss of À4Á4 g C m -2 a -1 at our test site. Land management has a significant impact on the erosion induced C fluxes, leading to a predominance of lateral C export under conventional and of vertical C exchange between soil and atmosphere under conservation agriculture. Overall, the application of the soil conservation practices, with enhanced C inputs by cover crops and decreased erosion, significantly reduced the modelled erosion induced C loss of the test site. Increasing C inputs alone, without a reduction of erosion rates, did not result in a reduction of erosion induced C losses. Moreover, our results show that the potential erosion induced C loss is very sensitive to the representation of erosion rates (long-term steady state versus event driven). A first estimate suggests that C losses are very sensitive to magnitude and frequency of erosion events. If long-term averages are dominated by large magnitude events modelled erosion induced C losses in the catchment were significantly reduced.
Surface runoff and associated erosion processes adversely affect soil and surface water quality. ... more Surface runoff and associated erosion processes adversely affect soil and surface water quality. There is increasing evidence that a sound understanding of spatial-temporal dynamics of land use and management are crucial to understanding surface runoff processes and underpinning mitigation strategies. In this review, we synthesise the effects of (1) temporal patterns of land management of individual fields, and (2) spatio-temporal interaction of several fields within catchments by applying semivariance analysis, which allows the extent and range of the different patterns to be compared. Consistent effects of management on the temporal dynamics of surface runoff of individual fields can be identified, some of which have been incorporated into small-scale hydrological models. In contrast, the effects of patchiness, the spatial organisation of patches with different soil hydrological properties, and the effects of linear landscape structures are less well understood and are rarely incorporated in models. The main challenge for quantifying these effects arises from temporal changes within individual patches, where the largest contrasts usually occur in mid-summer and cause a seasonally varying effect of patchiness on the overall catchment response. Some studies indicate that increasing agricultural patchiness, due to decreasing field sizes, reduces the catchment-scale response to rainfall, especially in cases of Hortonian runoff. Linear structures associated with patchiness of fields (e.g. field borders, ditches, and ephemeral gullies) may either increase or decrease the hydraulic connectivity within a catchment. The largest gap in research relates to the effects and temporal variation of patch interaction, the influence of the spatial organisation of patches and the interaction with linear structures. In view of the substantial changes in the structure of agricultural landscapes occurring throughout the world, it is necessary to improve our knowledge of the influence of patchiness and connectivity, and to implement this knowledge in new modelling tools.
Soil erosion, transport and deposition by water drastically affect the distribution of soil organ... more Soil erosion, transport and deposition by water drastically affect the distribution of soil organic carbon (SOC) within a landscape. Furthermore, soil redistribution is assumed to have a large impact on the exchange of carbon (C) between the pedosphere and the atmosphere. There is, however, significant scientific disagreement concerning the relative importance of the key-mechanisms at play. One of the major uncertainties concerns the fraction of SOC that is mineralized when soil is eroded by water, from the moment when detachment takes place until the moment when the SOC becomes protected by burial. In this study, the changes in C-exchange between soil and atmosphere as affected by soil redistribution processes were experimentally quantified. During a laboratory experiment, three types of erosional events were simulated, each of which was designed to produce a different amount of eroded soil material with a different degree of aggregation. During a 98-day period, CO 2 -efflux was measured in-situ and under field conditions on undisturbed soils with a layer of deposited soil material. Depending on the initial conditions of the soil and the intensity of the erosion process, a significant fraction of eroded SOC was mineralized after deposition. However, results also suggest that deposition produces a dense stratified layer of sediment that caps the soil surface, leading to a decrease in SOC decomposition in deeper soil layers. As a result, the net effect of erosion on SOC can be smaller, depending on the Correspondence to: P. Fiener (peter.fiener@uni-koeln.de) functioning of the whole soil system. In this study, soil redistribution processes contributed an additional emission of 2 to 12% of total C contained in eroded sediment.
Soil erosion, transport and deposition by water drastically affect the distribution of soil organ... more Soil erosion, transport and deposition by water drastically affect the distribution of soil organic carbon (SOC) within a landscape. Moreover, soil redistribution may have a large impact on the exchange of carbon (C) between the pedosphere and the atmosphere. One of the large information gaps within this research domain, concerns the fate of SOC after erosion by water. According to different (mainly laboratory) studies, soil redistribution leads to aggregate breakdown, thereby exposing the contained SOC to mineralization.
An extensive database of short to medium-term erosion rates as measured on erosion plots in Europ... more An extensive database of short to medium-term erosion rates as measured on erosion plots in Europe under natural rainfall was compiled from the literature. Statistical analysis confirmed the dominant influence of land use and cover on soil erosion rates. Sheet and rill erosion rates are highest on bare soil; vineyards show the second highest soil losses, followed by other arable lands (spring crops, orchards and winter crops). A land with a permanent vegetation cover (shrubs, grassland and forest) is characterised by soil losses which are generally more than an order of magnitude lower than those on arable land. Disturbance of permanent vegetation by fire leads to momentarily higher erosion rates but rates are still lower than those measured on arable land. We also noticed important regional differences in erosion rates. Erosion rates are generally much lower in the Mediterranean as compared to other areas in Europe; this is mainly attributed to the high soil stoniness in the Mediterranean. Measured erosion rates on arable and bare land were related to topography (slope steepness and length) and soil texture, while this was not the case for plots with a permanent land cover. We attribute this to a fundamental difference in runoff generation and sediment transfer according to land cover types. On the basis of these results we calculated mean sheet and rill erosion rates for the European area covered by the CORINE database: estimated rill and interrill erosion rates are ca. 1.2 t ha − 1 year − 1 for the whole CORINE area and ca. 3.6 t ha − 1 year − 1 for arable land. These estimates are much lower than some earlier estimates which were based on the erroneous extrapolation of small datasets. High erosion rates occur in areas dominated by vineyards, the hilly loess areas in West and Central Europe and the agricultural areas located in the piedmont areas of the major European mountain ranges.
Large uncertainties still exist on both the rates of soil organic carbon (SOC) mobilization by so... more Large uncertainties still exist on both the rates of soil organic carbon (SOC) mobilization by soil erosion as well as the fate of the eroded C. Using a range of techniques we characterized soil C redistribution by water erosion in two small agricultural catchments in the Belgian Loess Belt. Results from rainfall simulations showed that C enrichment in eroded sediments was much higher than clay enrichment (average enrichment ratios of 2.47 and 1.36 on average respectively). Selectivity was also observed in depositional processes: sediments deposited within the catchments were depleted in C and finer fractions as compared to the source soil. Selectivity was much more pronounced in winter than in summer, which is related to the degree of aggregation of the transported/deposited sediment. The combined selectivity of erosion and depositional processes resulted in a significant C enrichment of the sediment exported from the catchments with the C enrichment ratio (CER) between 1.2 and 3.0. Overall, catchment-scale C enrichment was higher than clay enrichment: enrichment ratios varied both with season and event intensity. The uncertainties on catchmentwide erosion and deposition rates precluded the closure of the sediment-C budgets. However, using a simple model we were able to show that both the magnitude and variation of observed catchment-scale CER was as expected from our understanding of C mobilization and deposition within the catchment. This suggests that most of the mobilized C was not mineralized during the erosion events but either re-deposited within the catchment or exported with the runoff. This was confirmed by the comparison of the elemental and isotopic signatures between exported sediments and source soil. In order to assess the role of erosion in the C cycle, understanding how C is mobilized and re-deposited selectively by erosion appears therefore as important as improving our understanding of the impact of erosion on C mineralization.
We estimated the long-term carbon balance [net biome production (NBP)] of European (EU-25) cropla... more We estimated the long-term carbon balance [net biome production (NBP)] of European (EU-25) croplands and its component fluxes, over the last two decades. Net primary production (NPP) estimates, from different data sources ranged between 490 and 846 gC m À2 yr À1 , and mostly reflect uncertainties in allocation, and in cropland area when using yield statistics. Inventories of soil C change over arable lands may be the most reliable source of information on NBP, but inventories lack full and harmonized coverage of EU-25. From a compilation of inventories we infer a mean loss of soil C amounting to 17 g m À2 yr À1 . In addition, three process-based models, driven by historical climate and evolving agricultural technology, estimate a small sink of 15 g C m À2 yr À1 or a small source of 7.6 g C m À2 yr À1 . Neither the soil C inventory data, nor the process model results support the previous European-scale NBP estimate by Janssens and colleagues of a large soil C loss of 90 AE 50 gC m À2 yr À1 . Discrepancy between measured and modeled NBP is caused by erosion which is not inventoried, and the burning of harvest residues which is not modeled. When correcting the inventory NBP for the erosion flux, and the modeled NBP for agricultural fire losses, the discrepancy is reduced, and cropland NBP ranges between À8.3 AE 13 and À13 AE 33 g C m À2 yr À1 from the mean of the models and inventories, respectively. The mean nitrous oxide (N 2 O) flux estimates ranges between 32 and 37 g C Eq m À2 yr À1 , which nearly doubles the CO 2 losses. European croplands act as small CH 4 sink of 3.3 g C Eq m À2 yr À1 . Considering ecosystem CO 2 , N 2 O and CH 4 fluxes provides for the net greenhouse gas balance a net source of 42-47 g C Eq m À2 yr À1 . Intensifying agriculture in Eastern Europe to the same level Western Europe amounts is expected to result in a near doubling of the N 2 O emissions in Eastern Europe. N 2 O emissions will then become the main source of concern for the impact of European agriculture on climate.
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Papers by kristof vanoost