Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Comparative Assessment of Goods and Services Provided by Grazing Regulation and Reforestation in Degraded Mediterranean Rangelands
Papanastasis, Vasilios P. ; Bautista, Susana ; Chouvardas, Dimitrios ; Mantzanas, Konstantinos ; Papadimitriou, Maria ; Garcia Mayor, Angeles ; Koukioumi, Polina ; Papaioannou, Athanasios ; Vallejo, Ramon V. - \ 2017
Land Degradation and Development 28 (2017)4. - ISSN 1085-3278 - p. 1178 - 1187.
carbon sequestration - ecosystem services - forage - grazing management - landscape functional analysis - plant diversity - restoration actions - soil functions

Several management actions are applied to restore ecosystem services in degraded Mediterranean rangelands, which range from adjusting the grazing pressure to the removal of grazers and pine plantations. Four such actions were assessed in Quercus coccifera L. shrublands in northern Greece: (i) moderate grazing by goats and sheep; (ii) no grazing; (iii) no grazing plus pine (Pinus pinaster Aiton) plantation in forest gaps (gap reforestation); and (iv) no grazing plus full reforestation of shrubland areas, also with P. pinaster. In addition, heavy grazing was also assessed to serve as a control action. We comparatively assessed the impact of these actions on key provisioning, regulating and supporting ecosystem services by using ground-based indicators. Depending on the ecosystem service considered, the management actions were ranked differently. However, the overall provision of services was particularly favoured under moderate and no grazing management options, with moderate grazing outranking any other action in provisioning services and the no grazing action presenting the most balanced provision of services. Pine reforestations largely contributed to water and soil conservation and C sequestration but had a negative impact on plant diversity when implemented at the expense of removing natural vegetation in the area. Heavy grazing had the lowest provision of ecosystem services. It is concluded that degraded rangelands can be restored by moderating the grazing pressure rather than completely banning livestock grazing or converting them into pine plantations.

Veen kan tegen een klimaatstootje
Kleis, Roelof ; Nijp, J.J. - \ 2015
Resource: weekblad voor Wageningen UR 10 (2015)9. - 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.
Low historical nitrogen deposition effect on carbon sequestration in the boreal zone
Fleischer, K. ; Wårlind, D. ; Molen, M.K. Van Der; Rebel, K.T. ; Arneth, A. ; Erisman, J.W. ; Wassen, M.J. ; Smith, B. ; Gough, C.M. ; Margolis, H.A. ; Cescatti, A. ; Montagnani, L. ; Arain, A. ; Dolman, A.J. - \ 2015
Journal of Geophysical Research: Biogeosciences 120 (2015)12. - ISSN 2169-8953 - p. 2542 - 2561.
carbon sequestration - FLUXNET - forests - global dynamic vegetation models - nitrogen deposition

Nitrogen (N) cycle dynamics and N deposition play an important role in determining the terrestrial biosphere's carbon (C) balance. We assess global and biome-specific N deposition effects on C sequestration rates with the dynamic global vegetation model LPJ-GUESS. Modeled CN interactions are evaluated by comparing predictions of the C and CN version of the model with direct observations of C fluxes from 68 forest FLUXNET sites. N limitation on C uptake reduced overestimation of gross primary productivity for boreal evergreen needleleaf forests from 56% to 18%, presenting the greatest improvement among forest types. Relative N deposition effects on C sequestration (dC/dN) in boreal, temperate, and tropical sites ranged from 17 to 26 kg C kg N-1 when modeled at site scale and were reduced to 12-22 kg C kg N-1 at global scale. We find that 19% of the recent (1990-2007) and 24% of the historical global C sink (1900-2006) was driven by N deposition effects. While boreal forests exhibit highest dC/dN, their N deposition-induced C sink was relatively low and is suspected to stay low in the future as no major changes in N deposition rates are expected in the boreal zone. N deposition induced a greater C sink in temperate and tropical forests, while predicted C fluxes and N-induced C sink response in tropical forests were associated with greatest uncertainties. Future work should be directed at improving the ability of LPJ-GUESS and other process-based ecosystem models to reproduce C cycle dynamics in the tropics, facilitated by more benchmarking data sets. Furthermore, efforts should aim to improve understanding and model representations of N availability (e.g., N fixation and organic N uptake), N limitation, P cycle dynamics, and effects of anthropogenic land use and land cover changes.

A new role for forests and the forest sector in the EU post-2020 climate targets
Nabuurs, G.J. ; Delacote, Philippe ; Ellison, David ; Hanewinkel, Marc ; Lindner, Marcus ; Nesbit, Martin ; Ollikainen, Markku ; Savaresi, Annalisa - \ 2015
European Forest Institute (From Science to Policy 2) - ISBN 9789525980202 - 30 p.
forestry - environmental policy - land use - european union - carbon sequestration - forests - biomass production - biobased economy - bosbouw - milieubeleid - landgebruik - europese unie - koolstofvastlegging - bossen - biomassa productie
We are living in a time of accelerated changes and unprecedented global challenges: energy security, natural resource scarcity, biodiversity loss, fossil-resource dependence and climate change. Yet the challenges also demand new solutions and offer new opportunities. The cross-cutting nature of forests and the forest-based sector provides a strong basis to address these interconnected societal challenges, while supporting the development of a European bioeconomy. The |European Forest Institue is an unbiased, science-based international organisation that provides the best forest science knowledge and information for better informed policy making. EFI provides support for decision-takers, policy makers and institutions, bringing together cross-boundery scientific knowledge and expertise to strengthen science-policy dialogue.
A review of blue carbon in the Netherlands
Tamis, J.E. ; Foekema, E.M. - \ 2015
Den Helder : IMARES (Report / IMARES C151/15) - 29
carbon - marine environment - coastal areas - biodiversity - carbon sequestration - climatic change - north sea - wadden sea - netherlands - koolstof - marien milieu - kustgebieden - biodiversiteit - koolstofvastlegging - klimaatverandering - noordzee - waddenzee - nederland
Blue carbon (the carbon stored in marine and coastal ecosystems – in biomass, buried in sediments and sequestered from the atmosphere and ocean) is considered as an issue of interest regarding its potential as a climate change mitigation measure in the OSPAR maritime area (OSPAR, 2015). Because blue carbon has not yet been properly explored in the North East Atlantic, OSPAR requested the Dutch government to provide information about blue carbon in the Netherlands and opportunities to enhance blue carbon in the Netherlands.
Organic matter dynamics in an intensive dairy production system on a Dutch Spodosol
Verloop, J. ; Hilhorst, G.J. ; Pronk, A.A. ; Sebek, L.B. ; Keulen, H. van; Janssen, B.H. ; Ittersum, M.K. van - \ 2015
Geoderma 237-238 (2015). - ISSN 0016-7061 - p. 159 - 167.
different manuring systems - farming systems - carbon sequestration - soil carbon - nitrogen-fertilization - pedotransfer functions - agricultural soils - biogas digestion - cropping systems - sandy soils
In many studies, possibilities are being explored to adjust farm management to increase or maintain soil organic matter (SOM) contents in agricultural soils. Some options may be conflicting with efficient nutrient (N and P) management, i.e. management aiming at maximum conversion of imported nutrients into exported products (milk and meat in the case of dairy farms). This study explored long term effects of efficient nutrient management on SOM dynamics on an experimental dairy farm with three types of land use: permanent grassland, a 3year grass-3year arable crop rotation (ROTI), and a 3year grass-5year arable crop rotation (ROTII). The arable phase in the crop rotations consisted predominantly of maize. The experimental farm, called 'De Marke', is located on a Spodosol with an Anthropic Epipedon in the Netherlands. The study consisted of: i) trend analyses based on data of measured SOM mass percentage (SOM %) from 1989-2010, and ii) simulations of long term (50years) SOM dynamics for four management alternatives. Three alternatives were related to manure digestion: no digestion; 'mild anaerobic digestion' (degrading 35% of organic matter) and; 'strong digestion' (degrading 70% of organic matter). The fourth management alternative was similar to the first (no digestion) but differed in that no catch crop was grown after maize. The trend analyses showed that SOM % of the 0-0.2m layer was approximately stable under permanent grassland. In ROTI, SOM % decreased on average by 0.04y-1 and in ROTII by 0.03y-1. The decline did not slow down over time. SOM decline was more severe on plots with relatively high initial SOM %. Decomposition was described using a mono-component model with a time dependent relative decomposition rate. Decomposition rates in the rotations with arable crops were not higher than those for permanent grassland indicating that tillage did not affect decomposition rate and that SOM dynamics were dominated by the quantity and quality of the substrate input. Simulations indicated that in the long term, decline of SOM must be expected both under arable crop-grassland rotations and under permanent grassland, even in the case of permanent grassland receiving undigested manure. Our results further indicate that strong manure digestion puts pressure on future SOM levels suggesting a trade-off with bio-energy production, and that the contribution of a catch crop to long term SOM is marginal.
Rescue and renewal of legacy soil resource inventories: A case study of the Limpopo National Park, Mozambique.
Cambule, A. ; Rossiter, D.G. ; Stoorvogel, J.J. ; Smaling, E.M.A. - \ 2015
Catena 125 (2015). - ISSN 0341-8162 - p. 169 - 182.
acid sulfate soils - carbon sequestration - resurrection - uncertainty - gambia - maps
Many areas of developing countries are covered by legacy soil surveys, which, however are hardly used, as they are not available in digital form, used outdated standards, and have unknown quality. There have been very few attempts to rescue and renew these surveys, nor are there established criteria for the evaluation of their quality. We therefore decided to test the applicability of the Cornell Adequacy Criteria (CAC) to assess the quality of several renewed soil surveys in or near the Limpopo National Park, Mozambique (centroid: 23° 18' 55.57¿ S, 31° 55' 16.24¿ E), using the concepts of digital soilmapping. The qualitywas assessed formapping andmonitoring soil organic carbon (SOC), in terms of geodetic control, positional accuracy, map scale, and texture and adequacy of map legend. Metadata was attached to the renewed maps. SOC stocks were estimated qualitatively based on the description of themap units and quantitatively by themeasure-and-multiply approach fromlegacy laboratory measurements. The positional accuracy of georegistrationwas 13 to 45% of the square root of aMinimumLegible Area (MLA). Point and area-class layers could be created with high positional accuracy. However the index of maximumreductionwas high, indicating that the original publication scale could be reduced.Map unit definitions and overall information content of the surveyswere adequate. Integration of remotely sensed optical imagery and digital elevation models could be used to derive accurate contours, against which the positional accuracy of contour-basedmap borderswas assessed. Less than 30% of their lengths were within a distance equal to the square root of MLA. These sources could not be used to evaluate internal map borders, due to the subdued topography and major land-use changes since the original survey. Qualitative estimates of SOC are between lowand medium, consistent with other studies in this area. The CAC proved to be a useful framework for determining the fitness for use of legacy surveys.
Plant species richness promotes soil carbon and nitrogen stocks in grasslands without legumes
Cong, W. ; Ruijven, J. van; Mommer, L. ; Deyn, G.B. de; Berendse, F. ; Hoffland, E. - \ 2014
biodiversity - ecosystem function - carbon sequestration - N mineralization - plant productivity - root biomass - decomposition
Data were collected in the 11-year grassland biodiversity experiment in Wageningen, the Netherlands, in 2010 and 2011. Abbreviated headlines are as follows: “”BLK”= block; “PT”= plot; "SR" = plant species richness; “MI” = monoculture identity (Ac = Agrostis capillaris; Ao = Anthoxanthum odoratum; Cj = Centaurea jacea; Fr = Festuca rubra; Hl = Holcus lanatus; Lv = Leucanthemum vulgare; Pl = Plantago lanceolata; Ra = Rumex acetosa); "AAB" = average aboveground biomass from 2000 to 2010 (g m-2); "RB" = standing root biomass (g fresh weight m-2) up to 50 cm depth in June 2010; "CS" = soil carbon stocks (g C m-2) in April 2011; "NS" = soil nitrogen stocks (g N m-2) in April 2011. "CD" = soil organic carbon decomposition (mg CO2-C kg-1 soil) measured in soil collected in April 2011; "NM" = potential net N mineralization rate (µg N kg-1 soil day-1) measured in soil collected in April 2011.
Carbon debt : inzichtelijk maken van maatschappelijke risico's van het opnemen van carbon debt vereisten
Nabuurs, G.J. ; Croezen, H. ; Arets, E.J.M.M. - \ 2014
Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2525)
koolstof - kooldioxide - koolstofvastlegging - schuld - biomassa - hout - bio-energie - risicobeheersing - duurzaamheid (sustainability) - energiecentrales - biobased economy - carbon - carbon dioxide - carbon sequestration - debt - biomass - wood - bioenergy - risk management - sustainability - power industry
In het Energieakkoord is afgesproken dat meestook van biomassa in kolencentrales niet meer wordt dan 25 PetaJoule. Als onderdeel van de totale biomassa is zo’n 3,5 miljoen ton hout nodig. De mee te stoken biomassa zal aanvullend op de NTA8080-eisen moeten voldoen aan ‘duurzaamheidseisen voor koolstofschuld, indirecte landgebruikseffecten (ILUC) en duurzaam bosbeheer (FSC)’. In dit rapport wordt verkend, in hoeverre de duurzaamheidseisen genoemd in het Energieakkoord, risico’s op een carbon debt al uitsluiten en welke biomassa-stromen additioneel uitgesloten worden door een carbon debt eis. Ook zijn mogelijke procesrisico’s geïdentificeerd die discussie over carbon debt kan opleveren voor de verdere uitwerking van de afspraken uit het Energieakkoord.
Development of soil and terrain digital database for major food-growing regions of India for resource planning
Chandran, P. ; Tiwary, P. ; Bhattacharyya, T. ; Mandal, C. ; Prasad, J. ; Ray, S.K. ; Sarkar, D. ; Pal, D.K. ; Dijkshoorn, J.A. ; Batjes, N.H. ; Bindraban, P.S. ; Thakre, S. - \ 2014
Current Science 107 (2014)9. - ISSN 0011-3891 - p. 1420 - 1430.
carbon sequestration - prediction - vertisols - areas
Soil information system in SOTER (soil and terrain digital database) framework is developed for the Indo-Gangetic Plains (IGP) and black soil regions (BSR) of India with the help of information from 842 georeferenced soil profiles including morphological, physical and chemical properties of soils in addition to the site characteristics and climatic information. The database has information from 82 climatic stations that can be linked with the other datasets. The information from this organized database can be easily retrieved for use and is compatible with the global database. The database can be updated with recent and relevant data as and when they are available. The database has many applications such as inputs for refinement of agro-ecological regions and sub-regions, studies on carbon sequestration, land evaluation and land (crop) planning, soil erosion, soil quality, carbon and crop modelling and other climate change related research. This warehouse of information in a structured framework can be used as a data bank for posterity.
Effect of ecosystem services provided by urban greenb infrastructure on indoor environment: a literature review
Wang, Y. ; Bakker, F. ; Groot, R.S. de; Woertche, H. - \ 2014
Building and Environment 77 (2014). - ISSN 0360-1323 - p. 88 - 100.
volatile organic-compounds - air-quality - contingent valuation - carbon sequestration - thermal performance - heat-island - residential buildings - outdoor relationships - particulate matter - biogenic emissions
The influence of urban green infrastructure on the indoor environment and the effects on human comfort and economic consequences are still unclear. This paper gives a systematic overview of the relationship, in terms of so-called ‘ecosystem services’, between urban green infrastructure and the indoor environment through a literature review in different disciplines. Urban green infrastructure (mainly trees, green walls and roofs) was found to contribute, both positively and negatively, to the indoor environment via the influence on the climate, energy use, air quality, sonic environment and aesthetic quality. Four main factors that influence these effects were identified, being vegetation characteristics, building characteristics (including layout and geometry), and geographical conditions. Although the reviewed papers have investigated the different ecosystem services on a wide range of space and time scales, the performance of urban green on the meso- and macro climate has received less attention than on the micro scale. Also direct effects of urban green infrastructure on indoor air quality and sonic environment were rarely studied. Another finding is that, whereas the modelling approach on climate regulation has been widely adopted by researchers throughout the world, empirical studies have mainly been performed in the USA. We also analysed the data found on economic implications. The economic effects of adjoining vegetation and green roofs on climate regulation provided energy savings of up to almost $250/tree/year, while the air quality regulation was valued between $0.12 and $0.6/m2 tree cover/year. Maximum monetary values attributed to noise regulation and aesthetic appreciation of urban green were $20 – $25/person/year, respectively. Of course these values are extremely time- and context-dependent but do give an indication of the potential economic effects of investing in urban green infrastructure. Based on this review, we conclude that new methods, measurement instruments and field experiments are needed to improve empirically supported correlations and develop concrete recommendations for urban planning and design.
Prospects for Agroforestry in REDD+ landscapes in Africa
Minang, P.A. ; Duguma, L.A. ; Bernard, F. ; Metz, O. ; Noordwijk, M. van - \ 2014
Current Opinion in Environmental Sustainability 6 (2014). - ISSN 1877-3435 - p. 78 - 82.
carbon sequestration - forest degradation - intensification - deforestation - conservation - challenges - systems - area
Agroforests and agroforestry can be direct targets of Reduced Emissions from Deforestation and Forest Degradation (REDD+) programs, or indirect parts of the necessary conditions for success. Whether or not it becomes a core element of REDD+ depends on the country's forest definition. We review these dimensions of agroforestry in REDD+, with supporting examples, mostly from Africa, and highlight the implications and challenges for enhancing the contributions of agroforestry to REDD+ and corresponding sustainable benefits. Where carbon stocks in agroforestry cannot be directly targeted in REDD+, agroforestry still can be included in REDD+ strategies, as ways to (1) shift demand for land (land sparing) and (2) provide alternative sources of products otherwise derived from forest over-exploitation or conversion, thereby avoiding leakage from forest protection efforts.
Going underground: root traits as drivers of ecosystem processes
Bardgett, R.D. ; Mommer, L. ; Vries, F.T. de - \ 2014
Trends in Ecology and Evolution 29 (2014)12. - ISSN 0169-5347 - p. 692 - 699.
soil microbial communities - plant functional traits - climate-change - biogeochemical significance - nutrient-acquisition - carbon sequestration - economics spectrum - species richness - water transport - elevated co2
Ecologists are increasingly adopting trait-based approaches to understand how community change influences ecosystem processes. However, most of this research has focussed on aboveground plant traits, whereas it is becoming clear that root traits are important drivers of many ecosystem processes, such as carbon (C) and nutrient cycling, and the formation and structural stability of soil. Here, we synthesise emerging evidence that illustrates how root traits impact ecosystem processes, and propose a pathway to unravel the complex roles of root traits in driving ecosystem processes and their response to global change. Finally, we identify research challenges and novel technologies to address them.
Temperate forest development during secondary succession: effects of soil, dominant species and management
Bose, A.K. ; Schelhaas, M. ; Mazerolle, M.J. ; Bongers, F. - \ 2014
European Journal of Forest Research 133 (2014)3. - ISSN 1612-4669 - p. 511 - 523.
organic-matter accumulation - net primary production - pinus-sylvestris l. - age-related decline - land-use change - scots pine - carbon sequestration - tree height - nitrogen mineralization - practical implications
With the increase in abandoned agricultural lands in Western Europe, knowledge on the successional pathways of newly developing forests becomes urgent. We evaluated the effect of time, soil type and dominant species type (shade tolerant or intolerant) on the development during succession of three stand attributes: above-ground biomass, stand height (HT) and stem density (SD). Additionally, we compared above-ground biomass (AGB) in natural and planted forests, using ten chronosequences (8 from the literature and 2 from this study). Both AGB and HT increased over time, whereas SD decreased. HT, SD and AGB differed among species types. For example, birch had greater HT than alder, willow and ash at a similar age and had higher SD than pine and oak at a similar age. However, birch showed lower AGB than pine. HT and AGB differed among soil types. They were higher in rich soil than in poor soils. Comparative analysis between chronosequences showed an effect of the regeneration method (natural regeneration vs plantation) on above-ground biomass. Planted sites had higher AGB than natural regeneration. Time, soil type, species and regeneration method influenced the mechanism of stand responses during secondary succession. These characteristics could be used to clarify the heterogeneity and potential productivity of such spontaneously growing temperate forest ecosystems.
Integrated Water Management Approaches for Sustainable Food Production
Fraiture, C.M.S. de; Fayrap, A. ; Unver, O. ; Ragab, R. - \ 2014
Irrigation and Drainage 63 (2014)2. - ISSN 1531-0353 - p. 221 - 231.
land-use - carbon sequestration - ecosystem services - climate-change - paddy fields - energy - soils - agriculture - irrigation - catchment
With a growing and increasingly wealthy and urban population, it is likely that the role of agricultural water management in ensuring food security will become more important. Pressure on water resources is high. Adverse environmental impacts as a result of sometimes poor management of irrigation and drainage are well documented, calling into question the sustainability of some of the current water management practices. Water, food, energy and climate are intrinsically connected. Greater pressure on water resources and, hence, stronger interconnectivity between sectors sharing these resources, call for new, integrated approaches to agricultural water management. This paper explores the links between water, food, energy and climate. It then explores the role of irrigation and drainage in food production and in providing other ecosystem services that are essential for the sustainable use of natural resources. The paper argues that looking at water for food production in isolation would miss important developments outside the water sector that determine the sustainability of agricultural water management. Integrated approaches to food production are not only necessary to ensure sustainability. They also lead to higher benefits per unit of water. For example, integrating food production with other ecosystem services provided by irrigation and drainage not only contributes to sustainability, it also leads to much higher economic value of benefits. This implies breaking disciplinary boundaries and encouraging greater cooperation from planning to implementation
Earthworms and the soil greenhouse gas balance
Lubbers, I.M. - \ 2014
Wageningen University. Promotor(en): Lijbert Brussaard, co-promotor(en): Jan-Willem van Groenigen. - Wageningen : Wageningen University - ISBN 9789461739315 - 222
aardwormen - oligochaeta - broeikasgassen - bodem - koolstofvastlegging in de bodem - koolstofvastlegging - emissie - bodembiologie - earthworms - greenhouse gases - soil - soil carbon sequestration - carbon sequestration - emission - soil biology

Earthworms play an essential part in determining the greenhouse gas (GHG) balance of soils worldwide. Their activity affects both biotic and abiotic soil properties, which in turn influence soil GHG emissions, carbon (C) sequestration and plant growth. Yet, the balance of earthworms stimulating C sequestration on the one hand and increasing GHG emissions on the other has not been investigated. Indeed, much is still unclear about how earthworms interact with agricultural land use and soil management practices, making predictions on their effects in agro-ecosystems difficult. In this thesis, I aimed to determine to what extent GHG mitigation by soil C sequestration as affected by earthworms is offset by earthworm-induced GHG emissions from agro-ecosystems under different types of management. To reach this aim, I combined mesocosm and field studies, as well as meta-analytic methods to quantitatively synthesize the literature.

Using meta-analysis, I showed that, on average, earthworm activity leads to a 24% increase in aboveground biomass, a 33% increase in carbon dioxide (CO2) emissions and a 42% increase in nitrous oxide (N2O) emissions. The magnitude of these effects depends on soil factors (e.g., soil organic matter content), experimental factors (e.g., crop residue addition or fertilizer type and rate) and earthworm factors (e.g., earthworm ecological category and -density).

Conducting both a mesocosm and a field study, I showed that earthworm activity results in increased N2O emissions from fertilized grasslands. Under field conditions I found an increase in earthworm-induced N2O emissions in autumn but not in spring, suggesting that earthworm effects in the field depend on soil physicochemical parameters influenced by meteorological and seasonal dynamics.

In a unique two-year experiment with a simulated no-tillage (NT) system and a simulated conventional tillage (CT) system, I found that earthworm presence increases GHG emissions in an NT system to the same level as in a CT system. This suggests that the GHG mitigation potential of NT agro-ecosystems is limited. When considering the C budget in the simulated NT system, I demonstrated that over the course of the experiment earthworms increase cumulative CO2 emissions by at least 25%, indicating a higher C loss compared to the situation without earthworms. Yet, in the presence of earthworms the incorporation of residue-derived C into all measured soil aggregate fractions also increased, indicating that earthworm activity can simultaneously enhance CO2 emissions and C incorporation into aggregate fractions.

In conclusion, the revealed dominance of GHG emissions over C sequestration as affected by earthworms implies that their presence in agro-ecosystems results in a negative impact on the soil greenhouse gas balance.

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

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.

Tracking C and N dynamics and stabilization in soil amended with wheat residue and its correponding bioethanol by-product: a 13C/15C study
Cayuela, M.L. ; Kuikman, P.J. ; Bakker, R.R.C. ; Groenigen, J.W. van - \ 2014
Global change biology Bioenergy 6 (2014)5. - ISSN 1757-1693 - p. 499 - 508.
organic-matter - macroaggregate dynamics - carbon sequestration - microbial biomass - removal - network - quality - impact - inputs
Removing agricultural cellulosic residues from fields for the production of ‘second generation biofuels'has the potential to profoundly alter C and N cycling in soil, increasing the risk of soil organic matter depletion and favoring soil–atmosphere gaseous exchanges. However, these negative impacts could potentially be offset by amending the soil with the solid by-product which is generated during bioethanol production. In a 100 days laboratory study, we investigated the fate of C and N after soil amendment with doubly labeled (13C, 15N) wheat residue (WR) and the corresponding bioethanol by-product (i.e. nonfermentable wheat residue NFWR) with and without extra N addition. Substituting WR with the corresponding amount of recovered bioethanol by-product partially compensated the C losses of full crop residue removal. When the equivalent amount of C was added as WR and NFWR, NFWR-derived C was found in significantly higher proportion in macroaggregates in soil (17.0 vs. 8.9%) after 100 days. Addition of both WR and NFWR reduced soil organic C (SOC) mineralization, i.e. it caused a negative priming effect in soil. However, this pattern was reversed when extra N was added. Both WR and NFWR increased the proportion of soil water-stable macroaggregates from 16% (in control) to 20–24% (in the different treatments). The results suggest that the more recalcitrant compounds derived from bioethanol production may stabilize more strongly and persist within the protected fractions of SOM pools. Our study demonstrates that NFWR, compared with WR application, neither increased N2O emissions nor had a negative impact on aggregate formation in the midterm. This demonstrates that NFWR has potential for replenishing SOC stocks
Plant species identity surpasses species richness as a key driver of N2O emissions from grassland
Abalos, D. ; Deyn, G.B. de; Kuyper, T.W. ; Groenigen, J.W. van - \ 2014
Global Change Biology 20 (2014)1. - ISSN 1354-1013 - p. 265 - 275.
nitrous-oxide - microbial communities - carbon sequestration - n uptake - soil - diversity - productivity - rhizosphere - traits - urine
Grassland ecosystems worldwide not only provide many important ecosystem services but they also function as a major source of the greenhouse gas nitrous oxide (N2O), especially in response to nitrogen deposition by grazing animals. To explore the role of plants as mediators of these emissions, we tested whether and how N2O emissions are dependent on grass species richness and/or specific grass species composition in the absence and presence of urine deposition. We hypothesized that: (i) N2O emissions relate negatively to plant productivity; (ii) four-species mixtures have lower emissions than monocultures (as they are expected to be more productive); (iii) emissions are lowest in combinations of species with diverging root morphology and high root biomass; and (iv) the identity of the key species that reduce N2O emissions is dependent on urine deposition. We established monocultures and two- and four-species mixtures of common grass species with diverging functional traits: Lolium perenne L. (Lp), Festuca arundinacea Schreb. (Fa), Phleum pratense L. (Php) and Poa trivialis L. (Pt), and quantified N2O emissions for 42 days. We found no relation between plant species richness and N2O emissions. However, N2O emissions were significantly reduced in specific plant species combinations. In the absence of urine, plant communities of Fa+Php acted as a sink for N2O, whereas the monocultures of these species constituted a N2O source. With urine application Lp+Pt plant communities reduced (P <0.001) N2O emissions by 44% compared to monocultures of Lp. Reductions in N2O emissions by species mixtures could be explained by total biomass productivity and by complementarity in root morphology. This study shows that plant species composition is a key component underlying N2O emissions from grassland ecosystems. Selection of specific grass species combinations in the context of the expected nitrogen deposition regimes may therefore provide a key for mitigation of N2O emissions.
Biochar and GHG mitigation. Which are the trade-offs?
Zwart, Kor - \ 2013
biochar - greenhouse gases - emission reduction - mitigation - carbon sequestration - soil carbon sequestration - pyrolysis - soil conditioners - soil chemistry - biobased economy
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