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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Data from: A test of the hierarchical model of litter decomposition
Bradford, Mark A. ; Veen, Ciska G.F. ; Bonis, Anne ; Bradford, Ella M. ; Classen, Aimee T. ; Cornelissen, J.H.C. ; Crowther, Thomas W. ; Freschet, Gregoire T. ; Kardol, Paul ; Manrubia Freixa, Marta ; Maynard, Daniel S. ; Newman, Gregory S. ; Logtestijn, Richard S.P. ; Viketoft, Maria ; Wardle, David A. ; Wieder, William R. ; Wood, Stephen A. ; Putten, W.H. van der - \ 2017
carbon cycling - ecological fallacy - ecosystem processes - experimental design - microbial biomass - pattern and scale - scaling theory - soil biogeochemical models - variability
Our basic understanding of plant litter decomposition informs the assumptions underlying widely applied soil biogeochemical models, including those embedded in Earth system models. Confidence in projected carbon cycle-climate feedbacks therefore depends on accurate knowledge about the controls regulating the rate at which plant biomass is decomposed into products such as CO2. Here, we test underlying assumptions of the dominant conceptual model of litter decomposition. The model posits that a primary control on the rate of decomposition at regional to global scales is climate (temperature and moisture), with the controlling effects of decomposers negligible at such broad spatial scales. Using a regional-scale litter decomposition experiment at six sites spanning from northern Sweden to southern France – and capturing both within and among site variation in putative controls – we find that contrary to predictions from the hierarchical model, decomposer (microbial) biomass strongly regulates decomposition at regional scales. Further, the size of the microbial biomass dictates the absolute change in decomposition rates with changing climate variables. Our findings suggest the need for revision of the hierarchical model, with decomposers acting as both local- and broad-scale controls on litter decomposition rates, necessitating their explicit consideration in global biogeochemical models.
Inclusion of ecological, economic, social, and institutional considerations when setting targets and limits for multispecies fisheries
Rindorf, Anna ; Dichmont, Catherine M. ; Thorson, James ; Charles, Anthony ; Clausen, Lotte Worsøe ; Degnbol, Poul ; Garcia, Dorleta ; Hintzen, Niels T. ; Kempf, Alexander ; Levin, Phillip ; Mace, Pamela ; Maravelias, Christos ; Minto, Coilín ; Mumford, John ; Pascoe, Sean ; Prellezo, Raul ; Punt, André E. ; Reid, David G. ; Rockmann, Christine ; Stephenson, Robert L. ; Thebaud, Olivier ; Tserpes, George ; Voss, Rüdiger - \ 2017
ICES Journal of Marine Science 74 (2017)2. - ISSN 1054-3139 - p. 453 - 463.
ecosystem-based fisheries management - multiple objectives - reference points - sustainability - variability
Targets and limits for long-term management are used in fisheries advice to operationalize the way management reflects societal priorities on ecological, economic, social and institutional aspects. This study reflects on the available published literature as well as new research presented at the international ICES/Myfish symposium on targets and limits for long term fisheries management. We examine the inclusion of ecological, economic, social and institutional objectives in fisheries management, with the aim of progressing towards including all four objectives when setting management targets or limits, or both, for multispecies fisheries. The topics covered include ecological, economic, social and governance objectives in fisheries management, consistent approaches to management, uncertainty and variability, and fisheries governance. We end by identifying ten ways to more effectively include multiple objectives in setting targets and limits in ecosystem based fisheries management.
Generation of spectral–temporal response surfaces by combining multispectral satellite and hyperspectral UAV imagery for precision agriculture applications
Gevaert, C. ; Suomalainen, J.M. ; Tang, J. ; Kooistra, L. - \ 2015
IEEE Journal of Selected Topics in Applied Earth Observation and Remote Sensing 8 (2015)6. - ISSN 1939-1404 - p. 3140 - 3149.
leaf chlorophyll concentration - remote-sensing data - vegetation indexes - data fusion - reflectance - variability - prediction - landsat
Precision agriculture requires detailed crop status information at high spatial and temporal resolutions. Remote sensing can provide such information, but single sensor observations are often incapable of meeting all data requirements. Spectral–temporal response surfaces (STRSs) provide continuous reflectance spectra at high temporal intervals. This is the first study to combine multispectral satellite imagery (from Formosat-2) with hyperspectral imagery acquired with an unmanned aerial vehicle (UAV) to construct STRS. This study presents a novel STRS methodology which uses Bayesian theory to impute missing spectral information in the multispectral imagery and introduces observation uncertainties into the interpolations. This new method is compared to two earlier published methods for constructing STRS: a direct interpolation of the original data and a direct interpolation along the temporal dimension after imputation along the spectral dimension. The STRS derived through all three methods are compared to field measured reflectance spectra, leaf area index (LAI), and canopy chlorophyll of potato plants. The results indicate that the proposed Bayesian approach has the highest correlation (r = 0.953) and lowest RMSE (0.032) to field spectral reflectance measurements. Although the optimized soil-adjusted vegetation index (OSAVI) obtained from all methods have similar correlations to field data, the modified chlorophyll absorption in reflectance index (MCARI) obtained from the Bayesian STRS outperform the other two methods. A correlation of 0.83 with LAI and 0.77 with canopy chlorophyll measurements are obtained, compared to correlations of 0.27 and 0.09, respectively, for the directly interpolated STRS.
From environmental nuisance to environmental opportunity: housefly larvae convert waste to livestock feed
Zanten, H.H.E. van; Mollenhorst, H. ; Oonincx, D.G.A.B. ; Bikker, P. ; Meerburg, B.G. ; Boer, I.J.M. de - \ 2015
Journal of Cleaner Production 102 (2015). - ISSN 0959-6526 - p. 362 - 369.
life-cycle perspective - bio-energy - food - consequences - variability - digestion - scenarios - amazon - manure - land
The livestock sector is in urgent need for more sustainable feed sources, because of the increased demand for animal-source food and the already high environmental costs associated with it. Recent developments indicate environmental benefits of rearing insects for livestock feed, suggesting that insect-based feed might become an important alternative feed source in the coming years. So far, however, this potential environmental benefit of waste-fed insects is unknown. This study, therefore, explores the environmental impact of using larvae of the common housefly grown on poultry manure and food waste as livestock feed. Data were provided by a laboratory plant in the Netherlands aiming to design an industrial plant for rearing housefly larvae. Production of 1 ton dry matter of larvae meal directly resulted in a global warming potential of 770 kg CO2 equivalents, an energy use of 9329 MJ and a land use of 32 m2, caused by use of water, electricity, and feed for flies, eggs and larvae. Production of larvae meal, however, also has indirect environmental consequences. Food waste, for example, was originally used for production of bio-energy. Accounting for these indirect consequences implies, e.g., including the environmental impact of production of energy needed to replace the original bio-energy function of food waste. Assuming, furthermore, that 1 ton of larvae meal replaced 0.5 ton of fishmeal and 0.5 ton of soybean meal, the production of 1 ton larvae meal reduced land use (1713 m2), but increased energy use (21,342 MJ) and consequently global warming potential (1959 kg CO2-eq). Results of this study will enhance a transparent societal and political debate about future options and limitations of larvae meal as livestock feed. Results of the indirect environmental impact, however, are situation specific, e.g. in this study food waste was used for anaerobic digestion. In case food waste would have been used for, e.g., composting, the energy use and related emission of greenhouse gases might decrease. Furthermore, the industrial process to acquire housefly larvae meal is still advancing, which also offers potential to reduce energy use and related emissions. Eventually, land scarcity will increase further, whereas opportunities exist to reduce energy use by, e.g., technical innovations or an increased use of solar or wind energy. Larvae meal production, therefore, has potential to reduce the environmental impact of the livestock sector.
Impulsive sounds change European seabass swimming patterns: influence of pulse repetition interval
Neo, Y.Y. ; Ufkes, E. ; Kastelein, R.A. ; Winter, H.V. ; Cate, C. ten; Slabbekoorn, H. - \ 2015
Marine Pollution Bulletin 97 (2015)1-2. - ISSN 0025-326X - p. 111 - 117.
startle-response - trawling vessel - fish - habituation - behavior - noise - variability - avoidance - zebrafish - recovery
Seismic shootings and offshore pile-driving are regularly performed, emitting significant amounts of noise that may negatively affect fish behaviour. The pulse repetition interval (PRI) of these impulsive sounds may vary considerably and influence the behavioural impact and recovery. Here, we tested the effect of four PRIs (0.5–4.0 s) on European seabass swimming patterns in an outdoor basin. At the onset of the sound exposures, the fish swam faster and dived deeper in tighter shoals. PRI affected the immediate and delayed behavioural changes but not the recovery time. Our study highlights that (1) the behavioural changes of captive European seabass were consistent with previous indoor and outdoor studies; (2) PRI could influence behavioural impact differentially, which may have management implications; (3) some acoustic metrics, e.g. SELcum, may have limited predictive power to assess the strength of behavioural impacts of noise. Noise impact assessments need to consider the contribution of sound temporal structure.
Enhancement of soil suppressiveness against Rhizoctonia solani in sugar beet by organic amendments
Postma, J. ; Schilder, M.T. - \ 2015
Applied Soil Ecology 94 (2015). - ISSN 0929-1393 - p. 72 - 79.
bacterial communities - nematode control - diversity - rhizosphere - variability - microflora - pathogens - fusarium - diseases - waste
The efficacy of different organic soil amendments on disease suppression to Rhizoctoniasolani AG 2-2IIIB was tested in a bio-assay with sugar beet as a test plant. Lysobacter populations in soil were quantified as a possible mechanism for disease suppression. Disease spread through the bio-assay tank was significantly reduced up to 86, 83, 52, and 48% after amending the non-sterilized soil with yeast or chitin at a rate of 0.3% (w/w) in consecutive experiments. Inexpensive protein-rich waste products from food industry (i.e., feather, hoof, meat, blood and fish meal) also effectively increased Rhizoctonia-disease suppression. Several plant-derived products (e.g., spent mushroom compost, dried algae, spent brewer’s grain, Brassica seed meal) were not effective. Lysobacter populations naturally present in the soil were increased 3–10 fold (measured by a TaqMan quantitative PCR) in soils amended with organic compounds that stimulated Rhizoctonia-disease suppression. The role of Lysobacter as a key factor in Rhizoctonia-disease suppression, however, could not be confirmed by adding Lysobacter isolates to a sterilized soil amended with yeast or chitin. Hence, we hypothesize that unexplored biological factors were involved in disease suppression, since the tested soil became conducive after gamma-sterilization. The consistent enhancement of Rhizoctonia-disease suppression in sugar beet with yeast and chitin amendments, and the efficacy of inexpensive protein-rich waste products such as feather meal and hoof meal in our bio-assays, warrants further study in field experiments
Climate change impact and adaptation research requires integrated assessment and farming systems analysis: a case study in the Netherlands
Reidsma, P. ; Wolf, J. ; Kanellopoulos, A. ; Schaap, B.F. ; Mandryk, M. ; Verhagen, J. ; Ittersum, M.K. van - \ 2015
Environmental Research Letters 10 (2015)4. - ISSN 1748-9326
european-union - crop yields - agriculture - responses - models - wheat - variability - improvement - strategies - scenarios
Rather than on crop modelling only, climate change impact assessments in agriculture need to be based on integrated assessment and farming systems analysis, and account for adaptation at different levels. With a case study for Flevoland, the Netherlands, we illustrate that (1) crop models cannot account for all relevant climate change impacts and adaptation options, and (2) changes in technology, policy and prices have had and are likely to have larger impacts on farms than climate change. While crop modelling indicates positive impacts of climate change on yields of major crops in 2050, a semiquantitative and participatory method assessing impacts of extreme events shows that there are nevertheless several climate risks. A range of adaptation measures are, however, available to reduce possible negative effects at crop level. In addition, at farm level farmers can change cropping patterns, and adjust inputs and outputs. Also farm structural change will influence impacts and adaptation. While the 5th IPCC report is more negative regarding impacts of climate change on agriculture compared to the previous report, also for temperate regions, our results show that when putting climate change in context of other drivers, and when explicitly accounting for adaptation at crop and farm level, impacts may be less negative in some regions and opportunities are revealed. These results refer to a temperate region, but an integrated assessment may also change perspectives on climate change for other parts of the world.
The contribution of phenotypic plasticity to complementary light capture in plant mixtures
Zhu, J. ; Werf, W. van der; Anten, N.P.R. ; Vos, J. ; Evers, J.B. - \ 2015
New Phytologist 207 (2015)4. - ISSN 0028-646X - p. 1213 - 1222.
functional diversity - current knowledge - biodiversity - productivity - photosynthesis - competition - model - communities - variability - environment
Interspecific differences in functional traits are a key factor for explaining the positive diversity– productivity relationship in plant communities. However, the role of intraspecific variation attributable to phenotypic plasticity in diversity–productivity relationships has largely been overlooked. By taking a wheat (Triticum aestivum)–maize (Zea mays) intercrop as an elementary example of mixed vegetation, we show that plasticity in plant traits is an important factor contributing to complementary light capture in species mixtures. We conceptually separated net biodiversity effect into the effect attributable to interspecific trait differences and species distribution (community structure effect), and the effect attributable to phenotypic plasticity. Using a novel plant architectural modelling approach, whole vegetation light capture was simulated for scenarios with and without plasticity based on empirical plant trait data. Light capture was 23% higher in the intercrop with plasticity than the expected value from monocultures, of which 36% was attributable to community structure and 64% was attributable to plasticity. For wheat, plasticity in tillering was the main reason for increased light capture, whereas for intercropped maize, plasticity induced a major reduction in light capture. The results illustrate the potential of plasticity for enhancing resource acquisition in mixed stands, and indicate the importance of plasticity in the performance of species-diverse plant communities.
Exploring climate change impacts and adaptation options for maize production in the Central Rift Valley of Ethiopia using different climate change scenarios and crop models
Kassie, B.T. ; Asseng, S. ; Rotter, R.P. ; Hengsdijk, H. ; Ruane, A.C. ; Ittersum, M.K. van - \ 2015
Climatic Change 129 (2015)1-2. - ISSN 0165-0009 - p. 145 - 158.
africa - yield - agriculture - risks - opportunities - vulnerability - temperatures - uncertainty - variability - projections
Exploring adaptation strategies for different climate change scenarios to support agricultural production and food security is a major concern to vulnerable regions, including Ethiopia. This study assesses the potential impacts of climate change on maize yield and explores specific adaptation options under climate change scenarios for the Central Rift Valley of Ethiopia by mid-century. Impacts and adaptation options were evaluated using three General Circulation Models (GCMs) in combination with two Representative Concentration Pathways (RCPs) and two crop models. Results indicate that maize yield decreases on average by 20 % in 2050s relative to the baseline (1980–2009) due to climate change. A negative impact on yield is very likely, while the extent of impact is more uncertain. The share in uncertainties of impact projections was higher for the three GCMs than it was for the two RCPs and two crop models used in this study. Increasing nitrogen fertilization and use of irrigation were assessed as potentially effective adaptation options, which would offset negative impacts. However, the response of yields to increased fertilizer and irrigation will be less for climate change scenarios than under the baseline. Changes in planting dates also reduced negative impacts, while changing the maturity type of maize cultivars was not effective in most scenarios. The multi-model based analysis allowed estimating climate change impact and adaptation uncertainties, which can provide valuable insights and guidance for adaptation planning.
Effects of technical interventions on flexibility of farming systems in Burkina Faso: Lessons for the design of innovations in West Africa
Andrieu, N. ; Descheemaeker, K.K.E. ; Sanou, T. ; Chia, E. - \ 2015
Agricultural Systems 136 (2015). - ISSN 0308-521X - p. 125 - 137.
crop-livestock systems - sub-saharan africa - climate-change - smallholder farmers - coping strategies - modeling approach - decision-making - constraints - uncertainty - variability
African farmers have always been exposed to climatic and economic variability and have developed a range of coping strategies. Such strategies form part of flexible farm management, an ability that may prove very valuable in the face of future climate change and market dynamics. The generally low productivity of African smallholder farming systems is usually addressed by research and development institutions by a variety of solutions for improving farm performance. However, changes to the system may affect the flexibility of farms and thus their ability to cope with variability. We quantified the added value of being flexible and how this flexibility is affected by technical changes, such as composting and cattle fattening recurrently proposed and promoted by research and development institutions and projects. The study was conducted in two villages of the agro-pastoral area of Burkina Faso, where livestock, cereals and cotton are the main farming activities. A whole-farm simulation model was developed based on information gathered during focus group meetings with farmers and detailed individual monitoring of farmers' practices. The model simulates farmers' decision rules governing the management of the cropping and livestock farm components, as well as crop and livestock production and farm gross margin. Using the existing decision rules, current farm performance was simulated by assessing the cereal balance, the fodder balance and the whole farm gross margin. Then, by comparing the mean and the coefficient of variation of these indicators resulting from (a) the existing decision rules (baseline scenario) and (b) a set of less flexible rules (rigid scenario), the added value of flexible management was revealed. The adoption of composting practices allowed a slight increase in gross margin associated with a decrease in its between-year variability in comparison with conventional practices. Cattle fattening only led to a higher gross margin in the years with high rainfall and low input prices when no management practices were used to limit dependence on external input. This kind of technical change thus requires increased management agility by farmers to deal with climatic and economic variability. We conclude that assessing the impact of technical interventions not only in terms of productivity but also in terms of changes in flexibility is useful for a better understanding of potential adoption of technical changes
The uncertain climate footprint of wetlands under human pressure
Petrescu, A.J. ; Lohila, A. ; Tuovinen, J.P. ; Baldocchi, D.D. ; Desai, A.R. ; Veenendaal, E.M. ; Schrier-Uijl, A. - \ 2015
Proceedings of the National Academy of Sciences of the United States of America 112 (2015)15. - ISSN 0027-8424 - p. 4594 - 4599.
methane emissions - carbon-dioxide - peatlands - ecosystem - fluxes - variability - dynamics - drainage - balance - cycle
Significant climate risks are associated with a positive carbon–temperature feedback in northern latitude carbon-rich ecosystems, making an accurate analysis of human impacts on the net greenhouse gas balance of wetlands a priority. Here, we provide a coherent assessment of the climate footprint of a network of wetland sites based on simultaneous and quasi-continuous ecosystem observations of CO2 and CH4 fluxes. Experimental areas are located both in natural and in managed wetlands and cover a wide range of climatic regions, ecosystem types, and management practices. Based on direct observations we predict that sustained CH4 emissions in natural ecosystems are in the long term (i.e., several centuries) typically offset by CO2 uptake, although with large spatiotemporal variability. Using a space-for-time analogy across ecological and climatic gradients, we represent the chronosequence from natural to managed conditions to quantify the “cost” of CH4 emissions for the benefit of net carbon sequestration. With a sustained pulse–response radiative forcing model, we found a significant increase in atmospheric forcing due to land management, in particular for wetland converted to cropland. Our results quantify the role of human activities on the climate footprint of northern wetlands and call for development of active mitigation strategies for managed wetlands and new guidelines of the Intergovernmental Panel on Climate Change (IPCC) accounting for both sustained CH4 emissions and cumulative CO2 exchange.
Reconciling spatial and temporal soi moisture effects on aftrnoon rainfall
Guillod, B.P. ; Orlowsky, B. ; Miralles, D.G. ; Teuling, A.J. ; Seneviratne, S.I. - \ 2015
Nature Communications 6 (2015). - ISSN 2041-1723
energy system ceres - stratiform precipitation - atmospheric controls - surface irradiances - land - evaporation - scale - feedback - evapotranspiration - variability
Soil moisture impacts on precipitation have been strongly debated. Recent observational evidence of afternoon rain falling preferentially over land parcels that are drier than the surrounding areas (negative spatial effect), contrasts with previous reports of a predominant positive temporal effect. However, whether spatial effects relating to soil moisture heterogeneity translate into similar temporal effects remains unknown. Here we show that afternoon precipitation events tend to occur during wet and heterogeneous soil moisture conditions, while being located over comparatively drier patches. Using remote-sensing data and a common analysis framework, spatial and temporal correlations with opposite signs are shown to coexist within the same region and data set. Positive temporal coupling might enhance precipitation persistence, while negative spatial coupling tends to regionally homogenize land surface conditions. Although the apparent positive temporal coupling does not necessarily imply a causal relationship, these results reconcile the notions of moisture recycling with local, spatially negative feedbacks.
Joint control of terrestrial gross primary productivity by plant phenology and physiology
Xia, J. ; Niu, S. ; Ciais, P. ; Janssens, I.A. ; Chen, J. ; Ammann, C. ; Arain, A. ; Blanken, P.D. ; Cescatti, A. ; Moors, E.J. - \ 2015
Proceedings of the National Academy of Sciences of the United States of America 112 (2015)9. - ISSN 0027-8424 - p. 2788 - 2793.
climate-change - chlorophyll fluorescence - ecosystem productivity - vegetation phenology - stomatal conductance - forest phenology - carbon uptake - models - photosynthesis - variability
Terrestrial gross primary productivity (GPP) varies greatly over time and space. A better understanding of this variability is necessary for more accurate predictions of the future climate–carbon cycle feedback. Recent studies have suggested that variability in GPP is driven by a broad range of biotic and abiotic factors operating mainly through changes in vegetation phenology and physiological processes. However, it is still unclear how plant phenology and physiology can be integrated to explain the spatiotemporal variability of terrestrial GPP. Based on analyses of eddy–covariance and satellite-derived data, we decomposed annual terrestrial GPP into the length of the CO2 uptake period (CUP) and the seasonal maximal capacity of CO2 uptake (GPPmax). The product of CUP and GPPmax explained >90% of the temporal GPP variability in most areas of North America during 2000–2010 and the spatial GPP variation among globally distributed eddy flux tower sites. It also explained GPP response to the European heatwave in 2003 (r2 = 0.90) and GPP recovery after a fire disturbance in South Dakota (r2 = 0.88). Additional analysis of the eddy–covariance flux data shows that the interbiome variation in annual GPP is better explained by that in GPPmax than CUP. These findings indicate that terrestrial GPP is jointly controlled by ecosystem-level plant phenology and photosynthetic capacity, and greater understanding of GPPmax and CUP responses to environmental and biological variations will, thus, improve predictions of GPP over time and space.
Implications of Climate Change for Rural Tourism in the Nordic Region
Nicholls, S. ; Amelung, B. - \ 2015
Scandinavian Journal of Hospitality and Tourism 15 (2015)1-2. - ISSN 1502-2250 - p. 48 - 72.
vulnerability - weather - index - variability - perspective - businesses - resources
In many rural regions, including those of the Nordic region, a former dependence on primary activities such as fishing, forestry, mining and/or agriculture has been superseded in recent decades by increasing involvement in the tourism sector. The purpose of this paper is to explore the potential implications of climate change for non-winter rural tourism in the Nordic region. Using the Tourism Climatic Index as an analytical tool, the paper highlights the range of potential conditions for outdoor tourism activity for three future time periods (the 2020s, 2050s and 2080s) under two scenarios of climate change (B1A and A1F). Findings suggest the possibility of substantially longer periods of desirable climatic conditions in future decades, particularly in the southern and eastern portions of the region. Implications of the findings are discussed in the context of the adaptive capacity of various tourism actors (tourists, providers and government) and in light of the particular vulnerabilities and assets of rural communities. The need for an integrated and multilevel approach that recognises the importance of the efficient coordination and integration of resources, products and services across multiple actor boundaries and levels is stressed.
Tree-ring d18O in African mahogany (Entandrophragma utile) records regional precipitation and can be used for climate reconstructions
Sleen, J.P. van der; Groenendijk, P. ; Zuidema, P. - \ 2015
Global and Planetary Change 127 (2015). - ISSN 0921-8181 - p. 58 - 66.
oxygen-isotope ratios - tropical atlantic - west-africa - monsoon - growth - forest - chronologies - temperature - variability - salinity
The availability of instrumental climate data in West and Central Africa is very restricted, both in space and time. This limits the understanding of the regional climate system and the monitoring of climate change and causes a need for proxies that allow the reconstruction of paleoclimatic variability. Here we show that oxygen isotope values (d18O) in tree rings of Entandrophragma utile from North-western Cameroon correlate to precipitation on a regional to sub-continental scale (1930–2009). All found correlations were negative, following the proposed recording of the ‘amount effect’ by trees in the tropics. The capacity of E. utile to record the variability of regional precipitation is also confirmed by the significant correlation of tree-ring d18O with river discharge data (1944–1983), outgoing longwave radiation (a proxy for cloud cover; 1974–2011) and sea surface salinity in the Gulf of Guinea (1950–2011). Furthermore, the high values in the d18O chronology from 1970 onwards coincide with the Sahel drought period. Given that E. utile presents clear annual growth rings, has a wide-spread distribution in tropical Africa and is long lived (> 250 years), we argue that the analysis of oxygen isotopes in growth rings of this species is a promising tool for the study of paleoclimatic variability during the last centuries in West and Central Africa.
Institutional constraints for adaptive capacity to climate change in Flevoland’s agriculture
Mandryk, M. ; Reidsma, P. ; Kartikasari, K. ; Ittersum, M.K. van; Arts, B.J.M. - \ 2015
Environmental Science & Policy 48 (2015). - ISSN 1462-9011 - p. 147 - 162.
land-use - adaptation - vulnerability - netherlands - management - variability - framework - barriers - policy - level
Institutional feasibility defined as the ability of institutions to support adaptive capacity, is an important aspect of climate adaptation, through its influence on the implementation of adaptation measures to climate change. The objective of this study is to create a framework for assessing institutional preconditions that enable or constrain climate change adaptation measures in agriculture and to apply the framework to a case study in agriculture. We adopted and modified the Procedure for Institutional Compatibility Assessment (PICA). Institutions in our framework are characterized by a set of crucial institutional preconditions (CIPs) and indicators linked to each CIP. CIPs refer to both institutional incentives and constraints for implementation of adaptation measures (here to climate change). We applied a combination of ranking and scoring techniques based on information from workshops, interviews and a literature review to assess institutional incentives and constraints for adaptation measures, together indicating the institutional feasibility of implementation of adaptation measures. We selected and assessed three adaptation measures relevant to agriculture in Flevoland, a province in the Netherlands: (1) improvement of water management and irrigation facilities; (2) relocation of farms; and (3) development of new crop varieties. The two main constraining CIPs for the implementation of the measures were found to be (1) heterogeneity of actors’ interests and (2) availability of resources. Based on the institutional feasibility analysis, the implementation of water management and improvement of irrigation facilities will potentially face fewer institutional constraints compared to the other two measures. We conclude that our approach proves applicable for institutional analyses of adaptation measures for current and future (climate) challenges at different levels of implementation, but that more applications are needed to test its validity and robustness.
Reconstructing Early Pleistocene (1.3 Ma) terrestrial environmental change in western Anatolia: Did it drive fluvial terrace formation?
Veldkamp, A. ; Candy, I. ; Jongmans, A.G. ; Maddy, D. ; Demir, T. ; Schoorl, J.M. ; Schreve, D. ; Stemerdink, C. ; Schriek, T. van der - \ 2015
Palaeogeography Palaeoclimatology Palaeoecology 417 (2015). - ISSN 0031-0182 - p. 91 - 104.
paleoenvironmental significance - volcanic disruption - gediz river - turkey - climate - paleosols - genesis - record - variability - carbonates
A terrestrial environmental reconstruction of an Early Pleistocene landscape from western Anatolia is presented. The basis of this reconstruction is a sedimentary stack comprising fluvial and colluvial slope deposits. Contained within this stack is a sequence comprising two massive laminar calcretes alternating with three reddish palaeosols. This evolutionary sequence is situated on top of a fluvial terrace staircase capped by a 1.3 Ma (40Ar/39Ar plateau age) lava flow. The micro-morphological properties of the observed calcretes and reddish palaeosols combined with the stable oxygen and carbon isotopic composition of the carbonates suggest the alternation of three stable relatively warm–humid (vegetation rich) and two stable relatively arid–cool (bare surface) cycles. In addition, there is also ample evidence for landscape instability in between these phases causing local soil truncation and slope instability in an open grassland–shrub environment. These landscape instability phases match well with known fluvial incisional phases of the Gediz during this period. This suggests that climate-forced landscape environmental dynamics were of sufficient magnitude to drive fluvial terrace formation of the Early Pleistocene Gediz.
Impact of predicted changes in rainfall and atmospheric carbon dioxide on maize and wheat yeilds in the Central Rift Valley of Ethiopia
Muluneh, A. ; Biazin, B. ; Stroosnijder, L. ; Bewket, W. ; Keesstra, S.D. - \ 2015
Regional Environmental Change 15 (2015)6. - ISSN 1436-3798 - p. 1105 - 1119.
fao crop model - climate-change - risk-assessment - aquacrop model - rainy-season - east-africa - dry spell - variability - drought - trends
This study assesses potential impacts of climate change on maize and wheat yields in the Central Rift Valley (CRV) of Ethiopia. We considered effects of elevated atmospheric carbon dioxide (CO2) and changes in rainfall during the main (Kiremt) and the short (Belg) rainfall cropping seasons during the two future periods (2020–2049 and 2066–2095). The MarkSimGCM daily weather generator was used to generate projected rainfall and temperature data using the outputs from ECHAM5 general circulation model and ensemble mean of six models under A2 (high) and B1 (low) emission scenarios. Crop yield simulations were made with the FAO’s AquaCrop model. The projected rainfall during Kiremt increases by 12–69 % while rainfall during Belg decreases by 20–68 %. The combined effect of elevated CO2 and projected climate factors increases maize yield by up to 59 % in sub-humid/humid areas of the CRV, but could result in a decrease of up to 46 % in the semiarid areas under ECHAM5 model. However, the maize yield increases in all parts of the CRV under the ensemble mean of models. Wheat yield shows no significant response to the projected rainfall changes, but increases by up to 40 % due to elevated CO2. Our results generally suggest that climate change will increase crop yields in the sub-humid/humid regions of the CRV. However, in the semi-arid parts the overall projected climate change will affect crop yields negatively.
Efficient development of highly polymorphic microsatellite markers based on polymorphic repeats in transcriptome sequences of multiple individuals
Vukosavljev, M. ; Esselink, G. ; Westende, W.P.C. van 't; Cox, P. ; Visser, R.G.F. ; Arens, P. ; Smulders, M.J.M. - \ 2015
Molecular Ecology Resources 15 (2015)1. - ISSN 1755-098X - p. 17 - 27.
est-ssr markers - genetic-linkage maps - in-silico - rose - l. - diversity - transferability - construction - variability - identification
The first hurdle in developing microsatellite markers, cloning, has been overcome by next generation sequencing. The second hurdle is testing to differentiate polymorphic from non-polymorphic loci. The third hurdle, somewhat hidden, is that only polymorphic markers with a large effective number of alleles are sufficiently informative to be deployed in multiple studies. Both steps are laborious and still done manually. We have developed a strategy in which we first screen reads from multiple genotypes for repeats that show the most length variants, and only these are subsequently developed into markers. We validated our strategy in tetraploid garden rose using Illumina paired-end transcriptome sequences of 11 roses. Out of 48 tested two markers failed to amplify but all others were polymorphic. Ten loci amplified more than one locus, indicating duplicated genes or gene families. Completely avoiding duplicated loci will be difficult because the range of numbers of predicted alleles of highly polymorphic single- and multi-locus markers largely overlapped. Of the remainder, half were replicate markers (i.e., multiple primer pairs for one locus), indicating the difficulty of correctly filtering short reads containing repeat sequences. We subsequently refined the approach to eliminate multiple primer sets to the same loci. The remaining 18 markers were all highly polymorphic, amplifying on average 11.7 alleles per marker (range = 6 to 20) in 11 tetraploid roses, exceeding the 8.2 alleles per marker of the 24 most polymorphic markers genotyped previously. This strategy, therefore, represents a major step forward in the development of highly polymorphic microsatellite markers.
Quirky patterns in time-series of estimates of recruitment could be artefacts
Dickey-Collas, M. ; Hintzen, N.T. ; Nash, R.D.M. ; Schoen, P.J. ; Payne, M.R. - \ 2015
ICES Journal of Marine Science 72 (2015)1. - ISSN 1054-3139 - p. 111 - 116.
stock-assessment - marine fishes - assessment models - reference points - atlantic - variability - abundance - sea - populations - management
The accessibility of databases of global or regional stock assessment outputs is leading to an increase in meta-analysis of the dynamics of fish stocks. In most of these analyses, each of the time-series is generally assumed to be directly comparable. However, the approach to stock assessment employed, and the associated modelling assumptions, can have an important influence on the characteristics of each time-series. We explore this idea by investigating recruitment time-series with three different recruitment parameterizations: a stock–recruitment model, a random-walk time-series model, and non-parametric “free” estimation of recruitment. We show that the recruitment time-series is sensitive to model assumptions and this can impact reference points in management, the perception of variability in recruitment and thus undermine meta-analyses. The assumption of the direct comparability of recruitment time-series in databases is therefore not consistent across or within species and stocks. Caution is therefore required as perhaps the characteristics of the time-series of stock dynamics may be determined by the model used to generate them, rather than underlying ecological phenomena. This is especially true when information about cohort abundance is noisy or lacking.
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