Sources of Uncertainty in Regional and Global Terrestrial CO2 Exchange Estimates
Bastos, A. ; O'Sullivan, M. ; Ciais, P. ; Makowski, D. ; Sitch, S. ; Friedlingstein, P. ; Chevallier, F. ; Rödenbeck, C. ; Pongratz, J. ; Luijkx, I.T. ; Patra, P.K. ; Peylin, P. ; Canadell, J.G. ; Lauerwald, R. ; Li, W. ; Smith, N.E. ; Peters, W. ; Goll, D.S. ; Jain, A.K. ; Kato, E. ; Lienert, S. ; Lombardozzi, D.L. ; Haverd, V. ; Nabel, J.E.M.S. ; Poulter, B. ; Tian, H. ; Walker, A.P. ; Zaehle, S. - \ 2020
Global Biogeochemical Cycles 34 (2020)2. - ISSN 0886-6236
atmospheric inversions - carbon cycle - dynamic global vegetation models - global carbon budget
The Global Carbon Budget 2018 (GCB2018) estimated by the atmospheric CO2 growth rate, fossil fuel emissions, and modeled (bottom-up) land and ocean fluxes cannot be fully closed, leading to a “budget imbalance,” highlighting uncertainties in GCB components. However, no systematic analysis has been performed on which regions or processes contribute to this term. To obtain deeper insight on the sources of uncertainty in global and regional carbon budgets, we analyzed differences in Net Biome Productivity (NBP) for all possible combinations of bottom-up and top-down data sets in GCB2018: (i) 16 dynamic global vegetation models (DGVMs), and (ii) 5 atmospheric inversions that match the atmospheric CO2 growth rate. We find that the global mismatch between the two ensembles matches well the GCB2018 budget imbalance, with Brazil, Southeast Asia, and Oceania as the largest contributors. Differences between DGVMs dominate global mismatches, while at regional scale differences between inversions contribute the most to uncertainty. At both global and regional scales, disagreement on NBP interannual variability between the two approaches explains a large fraction of differences. We attribute this mismatch to distinct responses to El Niño–Southern Oscillation variability between DGVMs and inversions and to uncertainties in land use change emissions, especially in South America and Southeast Asia. We identify key needs to reduce uncertainty in carbon budgets: reducing uncertainty in atmospheric inversions (e.g., through more observations in the tropics) and in land use change fluxes, including more land use processes and evaluating land use transitions (e.g., using high-resolution remote-sensing), and, finally, improving tropical hydroecological processes and fire representation within DGVMs.
Global 3-D Simulations of the Triple Oxygen Isotope Signature Δ17O in Atmospheric CO2
Koren, Gerbrand ; Schneider, Linda ; Velde, Ivar R. van der; Schaik, Erik van; Gromov, Sergey S. ; Adnew, Getachew A. ; Mrozek Martino, Dorota J. ; Hofmann, Magdalena E.G. ; Liang, Mao Chang ; Mahata, Sasadhar ; Bergamaschi, Peter ; Laan-Luijkx, Ingrid T. van der; Krol, Maarten C. ; Röckmann, Thomas ; Peters, Wouter - \ 2019
Journal of Geophysical Research: Atmospheres 124 (2019)15. - ISSN 2169-897X - p. 8808 - 8836.
O excess (ΔO) - carbon cycle - carbon dioxide (CO) - gross primary production (GPP) - mass-independent fractionation (MIF) - stable isotopes
The triple oxygen isotope signature Δ17O in atmospheric CO2, also known as its “17O excess,” has been proposed as a tracer for gross primary production (the gross uptake of CO2 by vegetation through photosynthesis). We present the first global 3-D model simulations for Δ17O in atmospheric CO2 together with a detailed model description and sensitivity analyses. In our 3-D model framework we include the stratospheric source of Δ17O in CO2 and the surface sinks from vegetation, soils, ocean, biomass burning, and fossil fuel combustion. The effect of oxidation of atmospheric CO on Δ17O in CO2 is also included in our model. We estimate that the global mean Δ17O (defined as Δ17O = ln(δ17O+1)−λRL·ln(δ18O+1) with λRL = 0.5229) of CO2 in the lowest 500 m of the atmosphere is 39.6 per meg, which is ∼20 per meg lower than estimates from existing box models. We compare our model results with a measured stratospheric Δ17O in CO2 profile from Sodankylä (Finland), which shows good agreement. In addition, we compare our model results with tropospheric measurements of Δ17O in CO2 from Göttingen (Germany) and Taipei (Taiwan), which shows some agreement but we also find substantial discrepancies that are subsequently discussed. Finally, we show model results for Zotino (Russia), Mauna Loa (United States), Manaus (Brazil), and South Pole, which we propose as possible locations for future measurements of Δ17O in tropospheric CO2 that can help to further increase our understanding of the global budget of Δ17O in atmospheric CO2.
Data from: Warming enhances sedimentation and decomposition of organic carbon in shallow macrophyte-dominated systems with zero net effect on carbon burial
Velthuis, Mandy ; Kosten, S. ; Aben, Ralf ; Kazanjian, Garabet ; Hilt, Sabine ; Peeters, E.T.H.M. ; Donk, Ellen van; Bakker, Elisabeth S. - \ 2019
carbon cycle - decomposition - global warming - mineralization - phenology - primary production - sedimentation - submerged aquatic plant
Temperatures have been rising throughout recent decades and are predicted to rise further in the coming century. Global warming affects carbon cycling in freshwater ecosystems, which both emit and bury substantial amounts of carbon on a global scale. Currently, most studies focus on the effect of warming on overall carbon emissions from freshwater ecosystems, while net effects on carbon budgets may strongly depend on burial in sediments. Here, we tested whether year‐round warming increases the production, sedimentation, or decomposition of particulate organic carbon and eventually alters the carbon burial in a typical shallow freshwater system. We performed an indoor experiment in eight mesocosms dominated by the common submerged aquatic plant Myriophyllum spicatum testing two temperature treatments: a temperate seasonal temperature control and a warmed (+4°C) treatment (n = 4). During a full experimental year, the carbon stock in plant biomass, dissolved organic carbon in the water column, sedimented organic matter, and decomposition of plant detritus were measured. Our results showed that year‐round warming nearly doubled the final carbon stock in plant biomass from 6.9 ± 1.1 g C in the control treatment to 12.8 ± 0.6 g C (mean ± SE), mainly due to a prolonged growing season in autumn. DOC concentrations did not differ between the treatments, but organic carbon sedimentation increased by 60% from 96 ± 9.6 to 152 ± 16 g C m−2 year−1 (mean ± SE) from control to warm treatments. Enhanced decomposition of plant detritus in the warm treatment, however, compensated for the increased sedimentation. As a result, net carbon burial was 40 ± 5.7 g C m−2 year−1 in both temperature treatments when fluxes were combined into a carbon budget model. These results indicate that warming can increase the turnover of organic carbon in shallow macrophyte‐dominated systems, while not necessarily affecting net carbon burial on a system scale.
Data from: An affordable and reliable assessment of aquatic decomposition: tailoring the Tea Bag Index to surface waters
Seelen, Laura ; Flaim, Giovanna ; Keuskamp, Joost ; Teurlincx, Sven ; Arias Font, Raquel ; Tolunay, Duygu ; Fránková, Markéta ; Šumberová, Kateřina ; Temponeras, Maria ; Lenhardt, Mirjana ; Jennings, Eleanor ; Senerpont Domis, L.N. de - \ 2018
carbon cycle - citizen science - decomposition constant - european lakes - lake management - standardized ecological assay
Litter decomposition is a vital part of the global carbon cycle as it determines not only the amount of carbon to be sequestered, but also how fast carbon re-enters the cycle. Freshwater systems play an active role in the carbon cycle as it receives, and decomposes, terrestrial litter material alongside decomposing aquatic plant litter. Decomposition of organic matter in the aquatic environment is directly controlled by water temperature and nutrient availability, which are continuously affected by global change. We adapted the Tea Bag Index (TBI), a highly standardized methodology for determining soil decomposition, for lakes by incorporating a leaching factor. By placing Lipton pyramid tea bags in the aquatic environment for 3 hours, we quantified the period of intense leaching which usually takes place prior to litter (tea) decomposition. Standard TBI methodology was followed after this step to determine how fast decomposition takes place (decomposition rate, k1) and how much of the material cannot be broken down and is thus sequestered (stabilization factor, S). A Citizen Science project was organized to test the aquatic TBI in 40 European lakes located in four climate zones, ranging from oligotrophic to hypereutrophic systems. We expected that warmer and/or eutrophic lakes would have a higher decomposition rate and a more efficient microbial community resulting in less tea material to be sequestered. The overall high decomposition rates (k1) found confirm the active role lakes play in the global carbon cycle. Across climate regions the lakes in the warmer temperate zone displayed a higher decomposition rate (k1) compared to the colder lakes in the continental and polar zones. Across trophic states, decomposition rates were higher in eutrophic lakes compared to oligotrophic lakes. Additionally, the eutrophic lakes showed a higher stabilization (S), thus a less efficient microbial community, compared to the oligotrophic lakes, although the variation within this group was high. Our results clearly show that the TBI can be used to adequately assess the decomposition process in aquatic systems. Using “alien standard litter” such as tea provides a powerful way to compare decomposition across climates, trophic states and ecosystems. By providing standardized protocols, a website, as well as face to face meetings, we also showed that collecting scientifically relevant data can go hand in hand with increasing scientific and environmental literacy in participants. Gathering process-based information about lake ecosystems gives managers the best tools to anticipate and react to future global change. Furthermore, combining this process-based information with citizen science, thus outreach, is in complete agreement with the Water Framework Directive goals as set in 2010.
Tropical land carbon cycle responses to 2015/16 El Niño as recorded by atmospheric greenhouse gas and remote sensing data
Gloor, Emanuel ; Wilson, Chris ; Chipperfield, Martyn P. ; Chevallier, Frederic ; Buermann, Wolfgang ; Boesch, Hartmut ; Parker, Robert ; Somkuti, Peter ; Gatti, Luciana V. ; Correia, Caio ; Domingues, Lucas G. ; Peters, Wouter ; Miller, John ; Deeter, Merritt N. ; Sullivan, Martin J.P. - \ 2018
Philosophical Transactions of the Royal Society B. Biological sciences 373 (2018)1760. - ISSN 0962-8436 - 12 p.
carbon cycle - fire - global warming - tropical forests
The outstanding tropical land climate characteristic over the past decades is rapid warming, with no significant large-scale precipitation trends. This warming is expected to continue but the effects on tropical vegetation are unknown. El Niño-related heat peaks may provide a test bed for a future hotter world. Here we analyse tropical land carbon cycle responses to the 2015/16 El Niño heat and drought anomalies using an atmospheric transport inversion. Based on the global atmospheric CO2 and fossil fuel emission records, we find no obvious signs of anomalously large carbon release compared with earlier El Niño events, suggesting resilience of tropical vegetation. We find roughly equal net carbon release anomalies from Amazonia and tropical Africa, approximately 0.5 PgC each, and smaller carbon release anomalies from tropical East Asia and southern Africa. Atmospheric CO anomalies reveal substantial fire carbon release from tropical East Asia peaking in October 2015 while fires contribute only a minor amount to the Amazonian carbon flux anomaly. Anomalously large Amazonian carbon flux release is consistent with downregulation of primary productivity during peak negative near-surface water anomaly (October 2015 to March 2016) as diagnosed by solar-induced fluorescence. Finally, we find an unexpected anomalous positive flux to the atmosphere from tropical Africa early in 2016, coincident with substantial CO release.This article is part of a discussion meeting issue 'The impact of the 2015/2016 El Niño on the terrestrial tropical carbon cycle: patterns, mechanisms and implications'.
Warming enhances sedimentation and decomposition of organic carbon in shallow macrophyte-dominated systems with zero net effect on carbon burial
Velthuis, Mandy ; Kosten, Sarian ; Aben, Ralf ; Kazanjian, Garabet ; Hilt, Sabine ; Peeters, Edwin T.H.M. ; Donk, Ellen van; Bakker, Elisabeth S. - \ 2018
Global Change Biology 24 (2018)11. - ISSN 1354-1013 - p. 5231 - 5242.
carbon cycle - decomposition - global warming - mineralization - phenology - primary production - sedimentation - submerged aquatic plant
Temperatures have been rising throughout recent decades and are predicted to rise further in the coming century. Global warming affects carbon cycling in freshwater ecosystems, which both emit and bury substantial amounts of carbon on a global scale. Currently, most studies focus on the effect of warming on overall carbon emissions from freshwater ecosystems, while net effects on carbon budgets may strongly depend on burial in sediments. Here, we tested whether year-round warming increases the production, sedimentation, or decomposition of particulate organic carbon and eventually alters the carbon burial in a typical shallow freshwater system. We performed an indoor experiment in eight mesocosms dominated by the common submerged aquatic plant Myriophyllum spicatum testing two temperature treatments: a temperate seasonal temperature control and a warmed (+4°C) treatment (n = 4). During a full experimental year, the carbon stock in plant biomass, dissolved organic carbon in the water column, sedimented organic matter, and decomposition of plant detritus were measured. Our results showed that year-round warming nearly doubled the final carbon stock in plant biomass from 6.9 ± 1.1 g C in the control treatment to 12.8 ± 0.6 g C (mean ± SE), mainly due to a prolonged growing season in autumn. DOC concentrations did not differ between the treatments, but organic carbon sedimentation increased by 60% from 96 ± 9.6 to 152 ± 16 g C m−2 yaer−1 (mean ± SE) from control to warm treatments. Enhanced decomposition of plant detritus in the warm treatment, however, compensated for the increased sedimentation. As a result, net carbon burial was 40 ± 5.7 g C m−2 year−1 in both temperature treatments when fluxes were combined into a carbon budget model. These results indicate that warming can increase the turnover of organic carbon in shallow macrophyte-dominated systems, while not necessarily affecting net carbon burial on a system scale.
Modeling the coupled exchange of water and CO2 over croplands
Combe, Marie - \ 2016
Wageningen University. Promotor(en): Wouter Peters; Maarten Krol, co-promotor(en): Jordi Vila-Guerau de Arellano. - Wageningen : Wageningen University - ISBN 9789462579255 - 152
carbon cycle - carbon dioxide - modeling - water - energy exchange - crop yield - grain crops - atmosphere - koolstofcyclus - kooldioxide - modelleren - water - energie-uitwisseling - gewasopbrengst - graangewassen - atmosfeer
Croplands are a managed type of vegetation, with a carbon storage that is highly optimized for food production. For instance, their sowing dates are chosen by the farmers, their genetic potential is bred for high grain yields, and their on-field competition with other species is reduced to the minimum. As a result of human intervention, croplands are a major land cover type (roughly one fifth of the land area over Europe) and they experience a short growing season during which they exchange carbon and water intensively with the atmosphere. Their growth significantly affects the seasonal amplitude of CO2 mole fractions over the globe, interact with extreme weather events such as droughts and heat waves, and impact surface hydrology due to their water consumption. However, and in spite of their relevance, terrestrial biosphere models used in carbon cycle and atmospheric research often assume the phenology of croplands to be similar to the one of grasslands, and they also ignore the impact of crop management. This oversimplification is the motivation for this thesis. We focus on understanding and modeling the key surface and atmospheric processes that shape the cropland water and CO2 exchange, and the resulting impact on the CO2 mole fractions of the atmosphere overhead. We study these processes from the daily to the seasonal scale, for croplands of the mid-latitudes. In the end, we come with recommendations and a new modeling framework to represent the cropland CO2 and water exchange in the Earth System, weather and climate models.
Veen kan tegen een klimaatstootje
Kleis, Roelof ; Nijp, J.J. - \ 2015
Resource: weekblad voor Wageningen UR 10 (2015)9. - ISSN 1874-3625 - p. 9 - 9.
klimaatverandering - koolstofvastlegging - koolstofcyclus - veengebieden - climatic change - carbon sequestration - carbon cycle - peatlands
Venen spelen een belangrijke rol in de koolstofcyclus. Een vijfde deel van alle koolstof in de bodem zit in veen. Venen zijn daarmee belangrijke koolstofmagazijnen. Maar blijft die opslagfunctie in stand als het klimaat verandert? Jelmer Nijp promoveerde vorige week op een studie naar het effect van veranderde regenval op venen.
Fine scale ecohydrological processes in northern peatlands and their relevance for the carbon cycle
Nijp, J.J. - \ 2015
Wageningen University. Promotor(en): Frank Berendse; Sjoerd van der Zee, co-promotor(en): Juul Limpens; Klaas Metselaar. - Wageningen : Wageningen University - ISBN 9789462575837 - 202
ecohydrologie - veengebieden - koolstofcyclus - koolstof - klimaat - neerslag - droogte - bodem - ecohydrology - peatlands - carbon cycle - carbon - climate - precipitation - drought - soil
Interpreting plant-sampled ¿14CO2 to study regional anthropogenic CO2 signals in Europe
Bozhinova, D.N. - \ 2015
Wageningen University. Promotor(en): Maarten Krol; Wouter Peters, co-promotor(en): Michiel van der Molen. - Wageningen : Wageningen University - ISBN 9789462574946 - 155
kooldioxide - emissie - planten - atmosfeer - gewassen - plantensamenstelling - koolstofcyclus - methodologie - luchtkwaliteit - carbon dioxide - emission - plants - atmosphere - crops - plant composition - carbon cycle - methodology - air quality
"Interpreting plant-sampled Δ14CO2 to study regional anthropogenic CO2 signals in Europe"
Author: Denica Bozhinova
This thesis investigates the quantitative interpretation of plant-sampled ∆14CO2 as an indicator of fossil fuel CO2 recently added to the atmosphere. We present a methodology to calculate the ∆14CO2 that has accumulated in a plant over its growing period, based on a modeling framework consisting of a plant growth model (SUCROS) and an atmospheric transport model (WRF-Chem). We verify our framework against available atmospheric observations and use it to evaluate the ∆14CO2 budget of Europe, which is influenced by both fossil fuel CO2 and nuclear 14CO2 anthropogenic emissions. Finally, we present the results of the 14C analysis of samples of maize leaves that were obtained from the Netherlands, Germany and France in an experimental campaign conducted during 2010-2012. We use our modeling framework to interpret the ∆14CO2 signals of the samples and evaluate the different type of emission sources that have contributed for their final signatures.
Studying biosphere-atmosphere exchange of CO2 through Carbon-13 stable isotopes
Velde, I.R. van der - \ 2015
Wageningen University. Promotor(en): Maarten Krol; Wouter Peters, co-promotor(en): J.B. Miller. - Wageningen : Wageningen University - ISBN 9789462572935 - 143
kooldioxide - biosfeer - atmosfeer - isotopen - koolstofcyclus - klimaat - voorspellingen - carbon dioxide - biosphere - atmosphere - isotopes - carbon cycle - climate - forecasts
Summary Thesis ‘Studying biosphere-atmosphere exchange of CO2 through
carbon-13 stable isotopes’
Ivar van der Velde
Making predictions of future climate is difficult, mainly due to large uncertainties in the carbon cycle. The rate at which carbon is stored in the oceans and terrestrial biosphere is not keeping pace with the rapid increase in fossil fuel combustion and deforestation, resulting in an increase of atmospheric carbon dioxide (CO2). To gain a better understanding of the global carbon cycle we need to combine multiple sources of data into one consistent analysis, such as, forest and agricultural statistics, satellite data, atmospheric and ecological observations, and mechanistic models. This thesis describes fundamental research on some of the key components of the terrestrial carbon cycle, i.e., gross primary production (GPP) and terrestrial ecosystem respiration (TER) of CO2, which forms the key to improved prediction of net exchange. Droughts have been shown to strongly influence this exchange, and to interpret these responses adequately we have turned to a large collection of new atmospheric observations of CO2, and its 13C isotope (13CO2), to constrain key model components.
In Chapter 2 we studied the global budget of atmospheric CO2 and the ratio of 13CO2/12CO2 (δ13C) and investigated the main terrestrial drivers of interannual variability (IAV) responsible for the observed atmospheric δ13C variations. In this chapter we introduced the SiBCASA biogeochemical model that we provided with a detailed isotopic discrimination scheme (to calculate the natural preference of 12CO2 over 13CO2 in uptake processes), separate 12C and 13C biogeochemical pools, and satellite-observed fire disturbances. This model was able to calculate uptake of 13CO2 and 12CO2 and produced return fluxes from its differently aged carbon pools, contributing to the so-called disequilibrium flux. Our simulated terrestrial isotope processes, plant discrimination and disequilibrium, closely resembled previously published values and similarly suggested that discrimination variations in C3 type plants and year-to-year variations in C3 and C4 productivity are the main drivers of IAV. The year-to-year variability in the terrestrial disequilibrium flux was much lower than required to match variations in atmospheric observations, under the common assumption of low variability in net ocean CO2 exchange, constant discrimination, and a closed CO2 budget. It was unclear how to increase IAV in the terrestrial biosphere, which suggested that SiBCASA missed adequate drought responses resulting in a latent isotope discrimination and variability in C3/C4 plant productivity.
Implementation of carbon isotope cycling, biomass burning, and SiBCASA’s drought response were closely studied in Chapter 3. Our biomass burning emissions were similar as in CASA-GFED; both in magnitude and spatial patterns, and the implementation of isotope exchange gave a global mean discrimination value of approximately 15 ‰, and varied spatially depending on the photosynthetic pathway in the plant. These values compared well (annually and seasonally) with other published results. Similarly, the size of the terrestrial isotopic disequilibrium was close to that of other studies. As plants experience drought stress, they respond by closing their stomata to prevent the loss of water. This process also inhibits the uptake of CO2 and reduces the isotope discrimination against 13CO2 molecules. We found that the amplitude of drought response in SiBCASA was smaller than suggested by the measured isotope signatures. We also found that a slight increase in stomatal closure for large vapor pressure deficits amplified the variations in the respired isotope signature. Finally, we saw the need for modified starch/sugar storage pools to improve the propagation of isotopic discrimination anomalies to respiration on short-term time scales.
In Chapter 4 we developed a multi-tracer inversion system to interpret signals in atmospheric CO2 and δ13C observations simultaneously. We wanted to know whether drought stress in plants can induce changes in atmospheric δ13C and whether they are interpretable. Using inverse modeling we were able to refine the discrimination parameter for plants as it reflected detectable variations in atmospheric δ13C. The results showed that the isotope discrimination values were consistently smaller during large severe droughts in the Northern Hemisphere, exceeding the estimates from SiBCASA (i.e., a larger reduction). Decreased discrimination suggested an increase in the regional intrinsic water use efficiency, which was also recorded at a large number of measurement sites. The IAV in net ecosystem exchange was relatively insensitive as we allowed the variability of the discrimination parameter to increase more than 8-fold, but it also allowed significant correlation between annual net exchange and discrimination. This study suggested a larger effect of droughts on discrimination than previously thought and that the treatment of drought response in biosphere models needs to be improved.
Carbon cycle research is far from complete as many components are still largely uncertain, which prevents us from making better predictions of future climate. This thesis, however, highlights the importance of isotope observations to assess and improve biogeochemical models, especially with regard to the allocation and turnover of carbon, and responses to droughts.
Methaanemissie op het melkveebedrijf : impactanalyse voor reductiemaatregelen en doorrekening daarvan in de Kringloopwijzer
Šebek, L.B. ; Haan, M.H.A. de; Bannink, A. - \ 2014
Wageningen : Wageningen UR Livestock Research (Rapport / Wageningen UR Livestock Research 796) - 38
melkveebedrijven - methaanproductie - methaanremmers - broeikasgassen - koolstofcyclus - melkvee - mest - voer - diervoedering - melkveehouderij - emissiereductie - dairy farms - methane production - methane inhibitors - greenhouse gases - carbon cycle - dairy cattle - manures - feeds - animal feeding - dairy farming - emission reduction
Voor u ligt het rapport ‘Methaanemissie op het melkveebedrijf: Impactanalyse voor reductiemaatregelen en doorrekening daarvan in de KringloopWijzer’. Het rapport geeft antwoord op de vraag van het Nederlandse diervoederbedrijfsleven om inzicht te geven in de relevantie en mogelijkheden voor aanpassing van de rekenregels in de KringloopWijzer. Het betreft de rekenregels voor methaanemissie uit de veestapel met als doel het effect van sturen op voerfactoren volledig in te rekenen. Door volledig inrekenen van voerfactoren wordt, met betrekking tot de vermindering van de methaanemissie, het handelingsperspectief duidelijk van zowel diervoederbedrijfsleven als (melk)veehouder.
The potential of carbon sequestration to mitigate against climate change in forests and agro ecosystems of Zimbabwe
Mujuru, L. - \ 2014
Wageningen University. Promotor(en): Rik Leemans, co-promotor(en): Marcel Hoosbeek. - Wageningen : Wageningen University - ISBN 9789461739285 - 209
koolstofvastlegging - klimaatverandering - bossen - agro-ecosystemen - mitigatie - koolstofvastlegging in de bodem - koolstofcyclus - koolstof - zimbabwe - carbon sequestration - climatic change - forests - agroecosystems - mitigation - soil carbon sequestration - carbon cycle - carbon - zimbabwe
Climate change adversely affects human livelihoods and the environment through alteration of temperatures, rainfall patterns, sea level rise and ecosystem productivity. Developing countries are more vulnerable to climate change because they directly depend on agriculture and natural ecosystem products for their livelihoods. Mitigation of climate change impacts includes practices that can store carbon (C) in soil and biomass thus, reducing concentrations of atmospheric carbon dioxide (CO2) and other greenhouse gasses. In addition, planted and natural forests that store large amounts of C, can become key resources for mitigating and reducing vulnerability to climate change, whilst infertile agricultural soils require large amounts of chemical and/or organic fertilisers to improve productivity. Increasing awareness about climate change mitigation has led to realisation of a need for sustainable land management practices and promoting soil C sequestration to reduce the greenhouse effects.
The C storage potential of agricultural soils is compounded by conventional tillage practices, covering large areas with only small portions of fields dedicated to conservation farming practices. Maintaining soil and crop productivity under these agricultural systems becomes a major challenge especially in rain-fed arid and semi-arid regions, characterised by long annual dry spells. Conservation tillage practices, such as no-till and reduced tillage, have been reported to increase soil organic carbon (SOC) stocks in agricultural systems as they reduce soil disturbance, whereas conventional tillage has been criticised for causing soil C losses, accelerating soil erosion and displacing of soil nutrients, despite benefits, such as reduced soil compaction, weed control and preparation of favourable seedbed, which have been reported under conventional tillage. The identification of appropriate agricultural management practices is critical for realisation of the benefits of Soil C sequestration and reducing emissions from agricultural activities.
This thesis was planned to improve our understanding on how tillage, fertilisation, tree planting or natural forest conservation can enhance C sequestration and thus mitigate climate change. The main goal was to quantify the influence of tillage, fertilisation and plantation forestry practices on C and N dynamics in bulk soil and density separated soil organic matter (SOM) fractions relative natural forest. Tillage treatments under reduced tillage (RP), no tillage (DS) and conventional tillage (CT) were compared with natural forests (NF) in sandy Haplic Arenosols and clayey Rhodic Ferralsols. Impacts of fertilisation were assessed from three fertility treatments; unfertilised control (control), nitrogen fertiliser (N Fert) and nitrogen fertiliser plus cattle manure (N Fert + manure) in conventionally tilled fields on Arenosols (sandy soil) and Luvisols (clayey soil) along two soil fertility gradients. Similarly, C and N storage in tree farming was studied using a Pinus patula chronosequence. Soil sampling followed randomised complete block design with four replications in agricultural systems and two replicates in each plantation age stands and natural forest. Sodium polytungstate (density 1.6 g cm-3) was used to isolate organic matter into free light fraction (fLF), occluded light fraction (oLF) and mineral associated heavy fraction (MaHF). Carbon an N were analysed by dry combustion and C and N stocks calculated using bulk density, depth and C and N concentration. The RothC model was used to match density separated fractions with conceptual model pools for agricultural and natural forest soils.
Findings from tillage studies showed significantly larger C and N stocks in natural forests than tillage systems despite the open access use of the natural forests. The C and N stocks were significantly lower in sandy than clayey soils. At 0–10 cm depth, SOC stocks increased under CT, RP and DS by 0.10, 0.24, 0.36 Mg ha−1yr−1 and 0.76, 0.54, 0.10 Mg ha−1yr−1 on sandy and clayey soils respectively over a four year period while N stocks decreased by 0.55, 0.40, 0.56 Mg ha−1yr−1 and 0.63, 0.65, 0.55 Mg ha−1yr−1 respectively. Under prevailing climatic and management conditions, improvement of residue retention could be a major factor that can distinguish the potential of different management practices for C sequestration.
Among the fertility treatments, there were significantly higher SOC and TON stocks under N Fert and N Fert + manure at 0-10 cm soil depth in Luvisols. Although this effect was not significant at 20-30 cm and 30-50 cm depth. On Arenosols, N Fert had highest C and N at all depths except at 0-10 cm. The storage of C and N on Luvisols, followed: control < N Fert < N Fert + manure whereas Arenosols had control < N Fert + manure < N Fert. Compared with control, N Fert and N Fert + manure enhanced fLF C on homefields and outfields by 19%, 24% and 9%, 22% on Luvisols and 17%, 26% and 26%, 26% respectively on Arenosols. Homefields on Luvisols, under N Fert and N Fert + manure had similar equilibrium levels, which were 2.5 times more than control.
Forests play a major role in regulating the rate of increase of global atmospheric CO2 storing C in soil and biomass although the C storage potential varies with forest type and plant species composition. In this research, storage of C and N were highest in moist forest and lowest in the Miombo woodland. In both natural and planted forests, above ground tree biomass was the major ecosystem C pool followed by forest floor’s humus (H) layer. The mineral soil had 45%, 31% and 24% of SOC stored at the 0–10, 10–30 and 30–60 cm soil depths respectively. Stand age affected C and N storage significantly having an initial decline after establishment recovering rapidly up to 10 years, after which it declined and increased again by 25 years. Average soil C among the Pinus compartments was 12 kg m-2, being highest at 10 years and lowest in the 1 year old stands. Organic N was also highest at 10 years and least at 25 years. The proportional mass of fLF and oLF in Miombo woodlands was similar while the other stands had higher fLF than oLF. The highest LF was in the moist forest. In the Pinus patula stands the fLF C contributed between 22−25%, the oLF C contributed 8−16% and MaHF C contributed between 60−70% to total SOC. Carbon in MaHF and oLF increased with depth while the fLF decreased with depth in all except the 1 and the 10 year old stands. Conversion of depleted Miombo woodlands to pine plantations can yield better C gains in the short and long run whilst moist forests provide both carbon and biodiversity. Where possible moist forests should be conserved and enrichment planting done in degraded areas to sustain them and if possible the forests can be considered as part of future projects on reduced emission from deforestation and degradation (REDD+). It is believed that REDD+ can promote both conservation and socio economic welfare, including poverty alleviation by bringing together the development of the forest and climate change link in African forests and woodlands. The focus on the monetary valuation and payment for environmental services can contribute to the attraction of political support for soil conservation. Developing countries therefore, need to formulate enabling economic and institutional land management policies that have positive impacts on poverty alleviation, food security and environmental sustainability.
Soil C models are used to predict impacts of land management on C storage. The RothC 2.63 model was used for estimating SOC stock under selected land management practices on the clayey and sandy soils of Zimbabwe. There is greater potential to store more C in clayey soils than sandy soils and in practices that receive more organic inputs. Results show that the RothC model pool of HUM + IOM is related to the measured MaHF from density fractionation and that the model can be used to estimate SOC stock changes on Zimbabwean agricultural and forest soils. The relationship between equilibrium levels estimated by the RothC model and those estimated using the Langmuir equation was good. A 1.5˚ C rise in temperature was found to cause the A and B systems on clayey soils to sequester more C. The results also show that, when holding all the other factors constant, the model is sufficiently sensitive to a rise in temperatures with sandy soils reaching an equilibrium much earlier than clayey soils. The modelling approach represents one of the most promising methods for the estimation of SOC stock changes and allowed us to evaluate the changes in SOC in the past period on the basis of measured data. However, since the data were obtained from short term experiments (4−9 years), further ground validation can be hampered by the lack of long-term experimental trials in the southern African region. The deficiency of adequate experimental sites also limits further work on model uncertainties. The understanding soil quality and dynamics however, helps to design sustainable agricultural systems, while achieving the urgently needed win-win situation in enhancing productivity and sequestering C.
Regional atmospheric feedbacks over land and coastal areas
Maat, H.W. ter - \ 2014
Wageningen University. Promotor(en): Bert Holtslag; Pavel Kabat, co-promotor(en): Ronald Hutjes. - Wageningen : Wageningen University - ISBN 9789461737731 - 172
atmosfeer - aardoppervlak - kustgebieden - koolstofcyclus - kooldioxide - landgebruik - neerslag - gematigd klimaat - semi-aride klimaat - modellen - nederland - saoedi-arabië - atmosphere - land surface - coastal areas - carbon cycle - carbon dioxide - land use - precipitation - temperate climate - semiarid climate - models - netherlands - saudi arabia
De afgelopen jaren is er een grotere vraag ontstaan naar klimaat- en weergegevens op lokaal niveau, nu en in de toekomst. Van regionale klimaatmodellen wordt verwacht dat zij dit kunnen geven met verbeterde informatie wat betreft extremen. Heterogeniteit moet daartoe verder uitgewerkt worden. Vier verschillende voorbeelden worden behandeld om het begrip te verbeteren van de processen en de terugkoppelingen op lokaal/regionaal niveau. Terugkoppelingen tussen aardoppervlak en de atmosfeer. Drie voorbeelden stammen uit Nederland (gematigd klimaat), de vierde is afkomstig uit het (semi-)aride Saoedi Arabië. Dit proefschrift doet aanbevelingen om regionale atmosferische modellen te verbeteren.
Climate Change: Global Risks, Challenges and Decisions
Richardson, K. ; Steffen, W. ; Liverman, D. ; Barker, T. ; Jotzo, F. ; Kammen, D.M. ; Leemans, R. ; Lenton, T.M. ; Munasinghe, M. ; Osman-Elasha, B. ; Schellnhuber, H.J. ; Stern, N. ; Vogel, C. ; Waever, O. - \ 2011
Cambridge : Cambridge University Press - ISBN 9780521198363 - 524
klimaatverandering - koolstofcyclus - beleid - mitigatie - risico - klimaat - biofysica - economie - ethiek - climatic change - carbon cycle - policy - mitigation - risk - climate - biophysics - economics - ethics
Providing an up-to-date synthesis of knowledge relevant to the climate change issue, this book ranges from the basic science documenting the need for policy action to the technologies, economic instruments and political strategies that can be employed in response to climate change. Ethical and cultural issues constraining the societal response to climate change are also discussed. This book covers a very wide range of disciplines – core biophysical sciences involved with climate change (geosciences, atmospheric sciences, ocean sciences, ecology/biology) as well as economics, political science, health sciences, institutions and governance, sociology, ethics and philosophy, and engineering.
Quick scan organische stof: kwaliteit, afbraak en trends
Hendriks, C.M.A. - \ 2011
Wageningen : Alterra (Alterra-rapport 2128) - 34
organisch bodemmateriaal - milieufactoren - landgebruik - nederland - koolstofcyclus - soil organic matter - environmental factors - land use - netherlands - carbon cycle
Organische stof is van grote invloed op de bodemstructuur, bodemvruchtbaarheid en gewasopbrengst. Landbouwkundig gebruik en fysieke aanpassingen van het milieu beïnvloeden het organische stofgehalte in de bodem. Om de voorraad organische stof duurzaam te beheren is het van belang om inzicht te hebben in factoren die van invloed zijn op de opbouw en afbraak van organische stof. Met literatuuronderzoek is kennis bijeen gebracht over opbouw, afbraak en trends in het organische stofgehalte. De trendanalyses laten een wisselend beeld zien maar tonen geen eenduidige afname. (Voormalig) bodemgebruik, veranderingen in het fysieke milieu en management zijn belangrijke factoren die het organische stofgehalte bepalen. Gezien de onzekerheden in analyses, experimenten en modelresultaten is het moeilijk om te zeggen of een verandering in het organische stofgehalte zich werkelijk voordoet bij minerale gronden in Nederland. Bij een gebalanceerd beheer zijn er mogelijkheden om het organische stofgehalte in stand te houden of zelfs te verhogen. Aanbevolen wordt om effecten van veranderend landgebruik en landbouwkundig beheer nader te onderzoeken.
Sustainability aspects of biogas and compost production
Zwart, Kor - \ 2010
biobased economy - biogas - composts - energy balance - emission - greenhouse gases - economic aspects - carbon cycle - cycling
Monitoring groene grondstoffen
Meesters, K.P.H. ; Boonekamp, P.M. ; Meeusen, M.J.G. ; Verhoog, D. ; Elbersen, H.W. - \ 2010
Wageningen : WUR-AFSG - 112
biobased economy - biomassa - vervangbare hulpbronnen - monitoren - koolstofcyclus - nederland - economie - kringlopen - biobased economy - biomass - renewable resources - monitors - carbon cycle - netherlands - economics - cycling
Het Platform Groene Grondstoffen heeft een monitoringsmethodiek laten ontwikkelen waarmee het aandeel biomassa dat bijdraagt aan de economie kan worden vastgesteld. Dit rapport beschrijft hoe de monitor is ontwikkeld en waar nog hiaten in de kennis zitten.
Flushing meadows : the influence of management alternatives on the greenhouse gas balance of fen meadow areas
Schrier-Uijl, A.P. - \ 2010
Wageningen University. Promotor(en): Frank Berendse, co-promotor(en): Elmar Veenendaal; Peter Leffelaar. - [S.l. : S.n. - ISBN 9789085857181 - 195
graslandbeheer - grondwaterstand - broeikaseffect - broeikasgassen - kooldioxide - koolstofcyclus - koolstofvastlegging - nederland - veengronden - veenweiden - verdroging (milieu) - grassland management - groundwater level - greenhouse effect - greenhouse gases - carbon dioxide - carbon cycle - carbon sequestration - netherlands - peat soils - peat grasslands - groundwater depletion
The degradation of peatlands is a major and growing source of anthropogenic greenhouse gas (GHG) emissions, and small changes in the management of peatlands can lead to drastic changes in GHG emissions and changes in carbon storage and in the past have indeed done so. GHG emissions from peatlands and the subsidence of peat soils can both probably be decreased by rewetting peatland and by restoring peatland by reducing the intensity of agricultural land use on peat soils. It might even be possible for these agricultural peatlands to revert to being sinks of GHGs. To test whether agricultural peat areas can be turned into GHG sinks and carbon sinks if they are restored and whether GHG emissions can at least be reduced by reducing management intensity and rewetting, a landscape-scale experiment measuring GHG emissions and carbon releases was started in 2005.
Productivity, Respiration, and Light-Response Parameters of World Grassland and Agroecosystems Derived From Flux-Tower Measurements
Gilmanov, T.G. ; Aires, L. ; Barsca, V. ; Baron, S. ; Moors, E.J. ; Jacobs, A. - \ 2010
Rangeland Ecology & Management 63 (2010)1. - ISSN 1550-7424 - p. 16 - 39.
koolstofcyclus - kooldioxide - netto ecosysteem koolstofbalans - graslanden - agro-ecosystemen - meting - carbon cycle - carbon dioxide - net ecosystem carbon balance - grasslands - agroecosystems - measurement - carbon-dioxide exchange - net ecosystem exchange - gross primary productivity - northern great-plains - eddy covariance - co2 exchange - temperate grassland - tallgrass prairie - water-vapor - soil
Grasslands and agroecosystems occupy one-third of the terrestrial area, but their contribution to the global carbon cycle remains uncertain. We used a set of 316 site-years of CO2 exchange measurements to quantify gross primary productivity, respiration, and light-response parameters of grasslands, shrublands/savanna, wetlands, and cropland ecosystems worldwide. We analyzed data from 72 global flux-tower sites partitioned into gross photosynthesis and ecosystem respiration with the use of the light-response method (Gilmanov, T. G., D. A. Johnson, and N. Z. Saliendra. 2003. Growing season CO2 fluxes in a sagebrush-steppe ecosystem in Idaho: Bowen ratio/energy balance measurements and modeling. Basic and Applied Ecology 4:167–183) from the RANGEFLUX and WORLDGRASSAGRIFLUX data sets supplemented by 46 sites from the FLUXNET La Thuile data set partitioned with the use of the temperature-response method (Reichstein, M., E. Falge, D. Baldocchi, D. Papale, R. Valentini, M. Aubinet, P. Berbigier, C. Bernhofer, N. Buchmann, M. Falk, T. Gilmanov, A. Granier, T. Grünwald, K. Havránková, D. Janous, A. Knohl, T. Laurela, A. Lohila, D. Loustau, G. Matteucci, T. Meyers, F. Miglietta, J. M. Ourcival, D. Perrin, J. Pumpanen, S. Rambal, E. Rotenberg, M. Sanz, J. Tenhunen, G. Seufert, F. Vaccari, T. Vesala, and D. Yakir. 2005. On the separation of net ecosystem exchange into assimilation and ecosystem respiration: review and improved algorithm. Global Change Biology 11:1424–1439). Maximum values of the quantum yield (a=75 mmol·mol-1), photosynthetic capacity (Amax=3.4 mg CO2·m-2·s-1), gross photosynthesis (Pg,max=116 g CO2·m-2·d-1), and ecological light-use efficiency (ecol=59 mmol·mol-1) of managed grasslands and high-production croplands exceeded those of most forest ecosystems, indicating the potential of nonforest ecosystems for uptake of atmospheric CO2. Maximum values of gross primary production (8600 g CO2·m-2·yr-1), total ecosystem respiration (7900 g CO2·m-2·yr-1), and net CO2 exchange (2400 g CO2·m-2·yr-1) were observed for intensively managed grasslands and high-yield crops, and are comparable to or higher than those for forest ecosystems, excluding some tropical forests. On average, 80% of the nonforest sites were apparent sinks for atmospheric CO2, with mean net uptake of 700 g CO2·m-2·yr-1 for intensive grasslands and 933 g CO2·m-2·d-1 for croplands. However, part of these apparent sinks is accumulated in crops and forage, which are carbon pools that are harvested, transported, and decomposed off site. Therefore, although agricultural fields may be predominantly sinks for atmospheric CO2, this does not imply that they are necessarily increasing their carbon stock