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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    Effectiveness of soil erosion barriers to reduce sediment connectivity at small basin scale in a fire-affected forest
    López-Vicente, Manuel ; Kramer, Henk ; Keesstra, Saskia - \ 2021
    Journal of Environmental Management 278 (2021). - ISSN 0301-4797
    Drone images - Forest fire - Post-fire practices - Sediment connectivity - Small basin
    Forest fires and post-fire management practices (PFMP) cause changes in the hydrological response of a hillslope. This study evaluates the effect of log erosion barriers (LB) and Easy-Barriers® (EB) on the spatial patterns and values of structural sediment connectivity (SC) in a Mediterranean mountainous pine forest affected by an arson fire in August 2017. A drone flight was done in July 2019 (23 months after the fire and 11 months after the PFMP) to obtain a high-resolution orthomosaic and DEM (at 0.05 m). Two contrasted areas, with and without PFMP, were selected along the same hillslope and 26 small basins were identified: 16 in the treated area (mean area, slope and vegetation recovery of 916 m2, 60% and 25%; with 94 LB and 39 EB) and 10 in the untreated area (1952 m2, 75% and 20%). The aggregated index of sediment connectivity (AIC) was chosen to compute SC in three temporal scenarios: Before and just after the fire and when all PFMP were implemented including the incipient vegetation recovery. Output normalization allowed the comparison of the non-nested basins among them. After accounting the intrinsic differences among the basins and areas, and the temporal changes of SC between the three scenarios, the contribution of the barriers was estimated in 27% from the total decrease of SC in the treated area (−8.5%). The remaining 73% was explained by the vegetation recovery. The effectiveness of the LB (11.3% on average) and EB (13.4%) did not diminish with increasing slope gradients. These percentages become relevant considering the small area affected by the LB (2.8%) and EB (1.3%). Independent metrics (convergence index, flow width, flat areas and LS factor) also reported clear differences between the two areas –higher soil erosive intensity in the untreated area– and in accordance with the AIC results.
    New approach methodologies (NAMs) for human-relevant biokinetics predictions. Meeting the paradigm shift in toxicology towards an animal-free chemical risk assessment
    Punt, Ans ; Bouwmeester, Hans ; Blaauboer, Bas J. ; Coecke, Sandra ; Hakkert, Betty ; Hendriks, Delilah F.G. ; Jennings, Paul ; Kramer, Nynke I. ; Neuhoff, Sibylle ; Masereeuw, Rosalinde ; Paini, Alicia ; Peijnenburg, Ad A.C.M. ; Rooseboom, Martijn ; Shuler, Michael L. ; Sorrell, Ian ; Spee, Bart ; Strikwold, Marije ; Meer, Andries D. Van der; Zande, Meike Van der; Vinken, Mathieu ; Yang, Huan ; Bos, Peter M.J. ; Heringa, Minne B. - \ 2020
    Altex 37 (2020)4. - ISSN 1868-596X - p. 607 - 622.
    biokinetics - in silico - in vitro - next-generation risk evaluations - PB(P)K - QIVIVE

    For almost fifteen years, the availability and regulatory acceptance of new approach methodologies (NAMs) to assess the absorption, distribution, metabolism and excretion (ADME/biokinetics) in chemical risk evaluations are a bottleneck. To enhance the field, a team of 24 experts from science, industry, and regulatory bodies, including new generation toxicologists, met at the Lorentz Centre in Leiden, The Netherlands. A range of possibilities for the use of NAMs for biokinetics in risk evaluations were formulated (for example to define species differences and human variation or to perform quantitative in vitro-in vivo extrapolations). To increase the regulatory use and acceptance of NAMs for biokinetics for these ADME considerations within risk evaluations, the development of test guidelines (protocols) and of overarching guidance documents is considered a critical step. To this end, a need for an expert group on biokinetics within the Organisation of Economic Cooperation and Development (OECD) to supervise this process was formulated. The workshop discussions revealed that method development is still required, particularly to adequately capture transporter mediated processes as well as to obtain cell models that reflect the physiology and kinetic characteristics of relevant organs. Developments in the fields of stem cells, organoids and organ-on-a-chip models provide promising tools to meet these research needs in the future.

    Gregarious behavior, human colonization and social differentiation : An agent-based model
    Fajardo, Sebastian ; Hofstede, Gert Jan ; Vries, Martijn de; Kramer, Mark R. ; Bernal, Andrés - \ 2020
    Journal of Artificial Societies and Social Simulation 23 (2020)4. - ISSN 1460-7425 - p. 1 - 23.
    Archaeology - Caribbean - Gregarious Behavior - Human Colonization - Settlement Patterns - Social Differentiation

    Studies of colonization processes in past human societies often use a standard population model in which population is represented as a single quantity. Real populations in these processes, however, are structured with internal classes or stages, and classes are sometimes created based on social differentiation. In this present work, information about the colonization of Old Providence Island was used to create an agent-based model of the colonization process in a heterogeneous environment for a population with social differentiation. Agents were socially divided into two classes and modeled with dissimilar spatial clustering preferences. The model and simulations assessed the importance of gregarious behavior for colonization processes conducted in heterogeneous environments by socially-differentiated populations. Results suggest that in these conditions, the colonization process starts with an agent cluster in the largest and most suitable area. The spatial distribu-tion of agents maintained a tendency toward randomness as simulation time increased, even when gregariousness values increased. The most conspicuous effects in agent clustering were produced by the initial conditions and behavioral adaptations that increased the agent capacity to access more resources and the likelihood of gregariousness. The approach presented here could be used to analyze past human colonization events or support long-term conceptual design of future human colonization processes with small social formations into unfamiliar and uninhabited environments.

    Annual progress report - ISSD Africa Community of Practice
    Thijssen, M.H. ; Mulerrins, J.L. ; Schagen, B. van; Ouko, W. ; Vernooy, R. ; Spielman, D. ; McEwan, M. ; Borman, G.D. ; Kramer, B. - \ 2020
    WCDI (WCDI-20-124 )
    Simulating emerging coastal tourism vulnerabilities: an agent-based modelling approach
    Student, Jillian ; Kramer, Mark R. ; Steinmann, Patrick - \ 2020
    Annals of Tourism Research 85 (2020). - ISSN 0160-7383
    Agent-based modelling (ABM) - Coastal tourism - Curaçao - Dynamic vulnerability approach - Environmental change - Scenario discovery

    Coastal tourism destinations face a range of climate-related changes. Prevailing challenges include understanding emerging changes and future uncertainties. A dynamic vulnerability approach is a promising way to analyse emerging socio-ecological vulnerabilities. This research presents an innovative coupling of the human-environment system in the agent-based model Coasting, and is applied to Curaçao's coastal tourism. We observe how operator numbers and environmental attractiveness, proxies for socio-ecological vulnerabilities, change over time. Global sensitivity analysis highlights the main interacting factors behind socio-ecological vulnerabilities. Scenario discovery explores the main drivers contributing to undesirable vulnerabilities. The model's findings provide key insights on which factors tourism destinations need to focus on to prevent socio-ecological vulnerabilities.

    Repetitive elements contribute to the diversity and evolution of centromeres in the fungal genus verticillium
    Seidl, Michael F. ; Kramer, H.M. ; Cook, David E. ; Fiorin, Gabriel L. ; Berg, Grardy C.M. van den; Faino, Luigi ; Thomma, Bart P.H.J. - \ 2020
    mBio 11 (2020)5. - ISSN 2161-2129 - p. 1 - 22.
    Centromere - Chromosome evolution - Heterochromatin - Verticillium

    Centromeres are chromosomal regions that are crucial for chromosome segregation during mitosis and meiosis, and failed centromere formation can contribute to chromosomal anomalies. Despite this conserved function, centromeres differ significantly between and even within species. Thus far, systematic studies into the organization and evolution of fungal centromeres remain scarce. In this study, we identified the centromeres in each of the 10 species of the fungal genus Verticillium and characterized their organization and evolution. Chromatin immunoprecipitation of the centromere-specific histone CenH3 (ChIP-seq) and chromatin conformation capture (Hi-C) followed by high-throughput sequencing identified eight conserved, large (~150-kb), AT-, and repeat-rich regional centromeres that are embedded in heterochromatin in the plant pathogen Verticillium dahliae. Using Hi-C, we similarly identified repeat-rich centromeres in the other Verticillium species. Strikingly, a single degenerated long terminal repeat (LTR) retrotransposon is strongly associated with centromeric regions in some but not all Verticillium species. Extensive chromosomal rearrangements occurred during Verticillium evolution, of which some could be linked to centromeres, suggesting that centromeres contributed to chromosomal evolution. The size and organization of centromeres differ considerably between species, and centromere size was found to correlate with the genome-wide repeat content. Overall, our study highlights the contribution of repetitive elements to the diversity and rapid evolution of centromeres within the fungal genus Verticillium. IMPORTANCE The genus Verticillium contains 10 species of plant-associated fungi, some of which are notorious pathogens. Verticillium species evolved by frequent chromosomal rearrangements that contribute to genome plasticity. Centromeres are instrumental for separation of chromosomes during mitosis and meiosis, and failed centromere functionality can lead to chromosomal anomalies. Here, we used a combination of experimental techniques to identify and characterize centromeres in each of the Verticillium species. Intriguingly, we could strongly associate a single repetitive element to the centromeres of some of the Verticillium species. The presence of this element in the centromeres coincides with increased centromere sizes and genome-wide repeat expansions. Collectively, our findings signify a role of repetitive elements in the function, organization, and rapid evolution of centromeres in a set of closely related fungal species.

    Global root traits (GRooT) database
    Guerrero-Ramírez, Nathaly R. ; Mommer, Liesje ; Freschet, Grégoire T. ; Iversen, Colleen M. ; McCormack, M.L. ; Kattge, Jens ; Poorter, Hendrik ; Plas, Fons van der; Bergmann, Joana ; Kuyper, Thom W. ; York, Larry M. ; Bruelheide, Helge ; Laughlin, Daniel C. ; Meier, Ina C. ; Roumet, Catherine ; Semchenko, Marina ; Sweeney, Christopher J. ; Ruijven, Jasper van; Valverde-Barrantes, Oscar J. ; Aubin, Isabelle ; Catford, Jane A. ; Manning, Peter ; Martin, Adam ; Milla, Rubén ; Minden, Vanessa ; Pausas, Juli G. ; Smith, Stuart W. ; Soudzilovskaia, Nadejda A. ; Ammer, Christian ; Butterfield, Bradley ; Craine, Joseph ; Cornelissen, Johannes H.C. ; Vries, Franciska T. de; Isaac, Marney E. ; Kramer, Koen ; König, Christian ; Lamb, Eric G. ; Onipchenko, Vladimir G. ; Peñuelas, Josep ; Reich, Peter B. ; Rillig, Matthias C. ; Sack, Lawren ; Shipley, Bill ; Tedersoo, Leho ; Valladares, Fernando ; Bodegom, Peter van; Weigelt, Patrick ; Wright, Justin P. ; Weigelt, Alexandra - \ 2020
    Global Ecology and Biogeography (2020). - ISSN 1466-822X
    Belowground ecology - functional biogeography - macroecological studies - plant form and function - publicly-available database - root traits

    Motivation: Trait data are fundamental to the quantitative description of plant form and function. Although root traits capture key dimensions related to plant responses to changing environmental conditions and effects on ecosystem processes, they have rarely been included in large-scale comparative studies and global models. For instance, root traits remain absent from nearly all studies that define the global spectrum of plant form and function. Thus, to overcome conceptual and methodological roadblocks preventing a widespread integration of root trait data into large-scale analyses we created the Global Root Trait (GRooT) Database. GRooT provides ready-to-use data by combining the expertise of root ecologists with data mobilization and curation. Specifically, we (a) determined a set of core root traits relevant to the description of plant form and function based on an assessment by experts, (b) maximized species coverage through data standardization within and among traits, and (c) implemented data quality checks. Main types of variables contained: GRooT contains 114,222 trait records on 38 continuous root traits. Spatial location and grain: Global coverage with data from arid, continental, polar, temperate and tropical biomes. Data on root traits were derived from experimental studies and field studies. Time period and grain: Data were recorded between 1911 and 2019. Major taxa and level of measurement: GRooT includes root trait data for which taxonomic information is available. Trait records vary in their taxonomic resolution, with subspecies or varieties being the highest and genera the lowest taxonomic resolution available. It contains information for 184 subspecies or varieties, 6,214 species, 1,967 genera and 254 families. Owing to variation in data sources, trait records in the database include both individual observations and mean values. Software format: GRooT includes two csv files. A GitHub repository contains the csv files and a script in R to query the database.

    Langetermijneffecten van extensieve duinbegrazing in kalkarme kustduinen
    Nijssen, Marijn ; Kuiters, Loek ; Smits, Nina ; Kramer, Henk ; Kuper, Jan ; Brouwer, Julian ; Vogels, Joost - \ 2020
    Driebergen : VBNE, Vereniging van Bos- en Natuurterreineigenaren (Rapport 2020/OBN234-DK) - 112
    Hip Fracture Patients in Geriatric Rehabilitation Show Poor Nutritional Status, Dietary Intake and Muscle Health
    Groenendijk, Inge ; Kramer, Charlotte S. ; Boeft, Laura M. Den; Hobbelen, Hans S.M. ; Putten, Gert-Jan Van Der; Groot, Lisette C.P.G.M. De - \ 2020
    Nutrients 12 (2020)9. - ISSN 2072-6643
    The aim of this study was to gain insight into the nutritional status, dietary intake and muscle health of older Dutch hip fracture patients to prevent recurrent fractures and to underpin rehabilitation programs. This cross-sectional study enrolled 40 hip fracture patients (mean ± SD age 82 ± 8.0 years) from geriatric rehabilitation wards of two nursing homes in the Netherlands. Assessments included nutritional status (Mini Nutritional Assessment), dietary intake on three non-consecutive days which were compared with Dietary Reference Intake values, and handgrip strength. Muscle mass was measured using Bioelectrical Impedance Analysis and ultrasound scans of the rectus femoris. Malnutrition or risk of malnutrition was present in 73% of participants. Mean energy, protein, fibre and polyunsaturated fat intakes were significantly below the recommendations, while saturated fat was significantly above the UL. Protein intake was <0.8 in 46% and <1.2 g/(kg·day) in 92%. Regarding micronutrients, mean intakes of calcium, vitamin D, potassium, magnesium and selenium were significantly below the recommendations. The prevalence of low muscle mass, low handgrip strength and sarcopenia were 35%, 27% and 10%, respectively. In conclusion, a poor nutritional status, dietary intake and muscle health are common in older hip fracture patients in geriatric rehabilitation wards.
    Automated crop plant counting from very high-resolution aerial imagery
    Valente, João ; Sari, Bilal ; Kooistra, Lammert ; Kramer, Henk ; Mücher, Sander - \ 2020
    Precision Agriculture 21 (2020). - ISSN 1385-2256 - p. 1366 - 1384.
    Crop emergence - Machine learning - Plant counting - Transfer learning - UAV RGB imagery

    Knowing before harvesting how many plants have emerged and how they are growing is key in optimizing labour and efficient use of resources. Unmanned aerial vehicles (UAV) are a useful tool for fast and cost efficient data acquisition. However, imagery need to be converted into operational spatial products that can be further used by crop producers to have insight in the spatial distribution of the number of plants in the field. In this research, an automated method for counting plants from very high-resolution UAV imagery is addressed. The proposed method uses machine vision—Excess Green Index and Otsu’s method—and transfer learning using convolutional neural networks to identify and count plants. The integrated methods have been implemented to count 10 weeks old spinach plants in an experimental field with a surface area of 3.2 ha. Validation data of plant counts were available for 1/8 of the surface area. The results showed that the proposed methodology can count plants with an accuracy of 95% for a spatial resolution of 8 mm/pixel in an area up to 172 m2. Moreover, when the spatial resolution decreases with 50%, the maximum additional counting error achieved is 0.7%. Finally, a total amount of 170 000 plants in an area of 3.5 ha with an error of 42.5% was computed. The study shows that it is feasible to count individual plants using UAV-based off-the-shelf products and that via machine vision/learning algorithms it is possible to translate image data in non-expert practical information.

    Storymap Bodemdaling Flevoland; De BRO als basis voor ruimtelijke inrichting Flevoland
    Tol-Leenders, Dorothee van; Gerritsen, Paul ; Okx, Joop ; Massop, Harry ; Kramer, Henk ; Heidema, Nanny - \ 2020

    Kramer, Henk

    Ede klimaatbestendig maken met behulp van de Basisregistratie Ondergrond (BRO)
    Tol-Leenders, Dorothee van; Maas, Gilbert ; Gerritsen, Paul ; Okx, Joop ; Kramer, Henk - \ 2020
    Design Features of Embodied Conversational Agents in eHealth : a Literature Review
    Stal, Silke ter; Kramer, Lean Leonie ; Tabak, Monique ; Akker, Harm op den; Hermens, Hermie - \ 2020
    International Journal of Human-Computer Studies 138 (2020). - ISSN 1071-5819
    design feature - eHealth - Embodied Conversational Agent - review

    Embodied conversational agents (ECAs) are gaining interest to elicit user engagement and stimulate actual use of eHealth applications. In this literature review, we identify the researched design features for ECAs in eHealth, the outcome variables that were used to measure the effect of these design features and what the found effects for each variable were. Searches were performed in Scopus, ACM Digital Library, PsychINFO, Pubmed and IEEE Xplore Digital Library, resulting in 1284 identified articles of which 33 articles were included. The agents speech and/or textual output and its facial and gaze expressions were the most common design features. Little research was performed on the agent's looks. The measured effect of these design features was often on the perception of the agent's and user's characteristics, relation with the agent, system usage, intention to use, usability and behaviour change. Results show that emotion and relational behaviour seem to positively affect the perception of the agents characteristics and that relational behaviour also seems to positively affect the relation with the agent, usability and intention to use. However, these design features do not necessarily lead to behaviour change. This review showed that consensus on design features of ECAs in eHealth is far from established. Follow-up research should include more research on the effects of all design features, especially research on the effects in a long-term, daily life setting, and replication of studies on the effects of design features performed in other contexts than eHealth.

    Greenhouse gas reporting for the LULUCFsector in the Netherlands : methodological background, update 2020
    Arets, E.J.M.M. ; Kolk, J.W.H. van der; Hengeveld, G.M. ; Lesschen, J.P. ; Kramer, H. ; Kuikman, P.J. ; Schelhaas, N.J. - \ 2020
    Wageningen : Statutory Research Tasks Unit for Nature & the Environment (WOt-technical report 168) - 127
    This report provides a complete methodological description and background information of the Dutch National System for Greenhouse gas reporting of the LULUCF sector. It provides detailed description of the methodologies, activity data and emission factors that were used. Each of the reporting categories Forest Land, Cropland, Grassland, Wetlands, Settlements, Other land and Harvested Wood Products are described in a separate chapter. Additionally it gives a table-by-table elaboration of the choices and motivations for filling the CRF tables for KP-LULUCF.
    The use of adverse outcome pathways in the safety evaluation of food additives
    Vinken, Mathieu ; Kramer, Nynke ; Allen, Timothy E.H. ; Hoffmans, Yvette ; Thatcher, Natalie ; Levorato, Sara ; Traussnig, Heinz ; Schulte, Stefan ; Boobis, Alan ; Thiel, Anette ; Rietjens, Ivonne M.C.M. - \ 2020
    Archives of Toxicology 94 (2020). - ISSN 0340-5761
    Adverse outcome pathway - Food additive - Safety evaluation

    In the last decade, adverse outcome pathways have been introduced in the fields of toxicology and risk assessment of chemicals as pragmatic tools with broad application potential. While their use in the pharmaceutical and cosmetics sectors has been well documented, their application in the food area remains largely unexplored. In this respect, an expert group of the International Life Sciences Institute Europe has recently explored the use of adverse outcome pathways in the safety evaluation of food additives. A key activity was the organization of a workshop, gathering delegates from the regulatory, industrial and academic areas, to discuss the potentials and challenges related to the application of adverse outcome pathways in the safety assessment of food additives. The present paper describes the outcome of this workshop followed by a number of critical considerations and perspectives defined by the International Life Sciences Institute Europe expert group.

    Tree rings predict the future
    Kramer, Koen - \ 2020
    Developing Embodied Conversational Agents for Coaching People in a Healthy Lifestyle: Scoping Review
    Kramer, Lean L. ; Stal, Silke Ter; Mulder, Bob C. ; Vet, Emely de; Velsen, Lex van - \ 2020
    Journal of Medical Internet Research 22 (2020)2. - ISSN 1438-8871
    eHealth - embodied conversational agent - health behavior - lifestyle - virtual agent

    BACKGROUND: Embodied conversational agents (ECAs) are animated computer characters that simulate face-to-face counseling. Owing to their capacity to establish and maintain an empathic relationship, they are deemed to be a promising tool for starting and maintaining a healthy lifestyle. OBJECTIVE: This review aimed to identify the current practices in designing and evaluating ECAs for coaching people in a healthy lifestyle and provide an overview of their efficacy (on behavioral, knowledge, and motivational parameters) and use (on usability, usage, and user satisfaction parameters). METHODS: We used the Arksey and O'Malley framework to conduct a scoping review. PsycINFO, Medical Literature Analysis and Retrieval System Online, and Scopus were searched with a combination of terms related to ECA and lifestyle. Initially, 1789 unique studies were identified; 20 studies were included. RESULTS: Most often, ECAs targeted physical activity (n=16) and had the appearance of a middle-aged African American woman (n=13). Multiple behavior change techniques (median=3) and theories or principles (median=3) were applied, but their interpretation and application were usually not reported. ECAs seemed to be designed for the end user rather than with the end user. Stakeholders were usually not involved. A total of 7 out of 15 studies reported better efficacy outcomes for the intervention group, and 5 out of 8 studies reported better use-related outcomes, as compared with the control group. CONCLUSIONS: ECAs are a promising tool for persuasive communication in the health domain. This review provided valuable insights into the current developmental processes, and it recommends the use of human-centered, stakeholder-inclusive design approaches, along with reporting on the design activities in a systematic and comprehensive manner. The gaps in knowledge were identified on the working mechanisms of intervention components and the right timing and frequency of coaching.

    Does the leaf economic spectrum hold within plant functional types? A Bayesian multivariate trait meta-analysis
    Shiklomanov, Alexey N. ; Cowdery, Elizabeth M. ; Bahn, Michael ; Byun, Chaeho ; Jansen, Steven ; Kramer, Koen ; Minden, Vanessa ; Niinemets, Ülo ; Onoda, Yusuke ; Soudzilovskaia, Nadejda A. ; Dietze, Michael C. - \ 2020
    Ecological Applications 30 (2020)3. - ISSN 1051-0761
    ecological modeling - functional trade-off - hierarchical modeling - leaf biochemistry - leaf morphology - trait variation

    The leaf economic spectrum is a widely studied axis of plant trait variability that defines a trade-off between leaf longevity and productivity. While this has been investigated at the global scale, where it is robust, and at local scales, where deviations from it are common, it has received less attention at the intermediate scale of plant functional types (PFTs). We investigated whether global leaf economic relationships are also present within the scale of plant functional types (PFTs) commonly used by Earth System models, and the extent to which this global-PFT hierarchy can be used to constrain trait estimates. We developed a hierarchical multivariate Bayesian model that assumes separate means and covariance structures within and across PFTs and fit this model to seven leaf traits from the TRY database related to leaf longevity, morphology, biochemistry, and photosynthetic metabolism. Although patterns of trait covariation were generally consistent with the leaf economic spectrum, we found three approximate tiers to this consistency. Relationships among morphological and biochemical traits (specific leaf area [SLA], N, P) were the most robust within and across PFTs, suggesting that covariation in these traits is driven by universal leaf construction trade-offs and stoichiometry. Relationships among metabolic traits (dark respiration [Rd], maximum RuBisCo carboxylation rate [Vc,max], maximum electron transport rate [Jmax]) were slightly less consistent, reflecting in part their much sparser sampling (especially for high-latitude PFTs), but also pointing to more flexible plasticity in plant metabolistm. Finally, relationships involving leaf lifespan were the least consistent, indicating that leaf economic relationships related to leaf lifespan are dominated by across-PFT differences and that within-PFT variation in leaf lifespan is more complex and idiosyncratic. Across all traits, this covariance was an important source of information, as evidenced by the improved imputation accuracy and reduced predictive uncertainty in multivariate models compared to univariate models. Ultimately, our study reaffirms the value of studying not just individual traits but the multivariate trait space and the utility of hierarchical modeling for studying the scale dependence of trait relationships.

    Low growth resilience to drought is related to future mortality risk in trees
    DeSoto, Lucía ; Cailleret, Maxime ; Sterck, Frank ; Jansen, Steven ; Kramer, Koen ; Robert, Elisabeth M.R. ; Aakala, Tuomas ; Amoroso, Mariano M. ; Bigler, Christof ; Camarero, J.J. ; Čufar, Katarina ; Gea-Izquierdo, Guillermo ; Gillner, Sten ; Haavik, Laurel J. ; Hereş, Ana Maria ; Kane, Jeffrey M. ; Kharuk, Vyacheslav I. ; Kitzberger, Thomas ; Klein, Tamir ; Levanič, Tom ; Linares, Juan C. ; Mäkinen, Harri ; Oberhuber, Walter ; Papadopoulos, Andreas ; Rohner, Brigitte ; Sangüesa-Barreda, Gabriel ; Stojanovic, Dejan B. ; Suárez, Maria Laura ; Villalba, Ricardo ; Martínez-Vilalta, Jordi - \ 2020
    Nature Communications 11 (2020)1. - ISSN 2041-1723

    Severe droughts have the potential to reduce forest productivity and trigger tree mortality. Most trees face several drought events during their life and therefore resilience to dry conditions may be crucial to long-term survival. We assessed how growth resilience to severe droughts, including its components resistance and recovery, is related to the ability to survive future droughts by using a tree-ring database of surviving and now-dead trees from 118 sites (22 species, >3,500 trees). We found that, across the variety of regions and species sampled, trees that died during water shortages were less resilient to previous non-lethal droughts, relative to coexisting surviving trees of the same species. In angiosperms, drought-related mortality risk is associated with lower resistance (low capacity to reduce impact of the initial drought), while it is related to reduced recovery (low capacity to attain pre-drought growth rates) in gymnosperms. The different resilience strategies in these two taxonomic groups open new avenues to improve our understanding and prediction of drought-induced mortality.

    Reciprocal cybrids reveal how organellar genomes affect plant phenotypes
    Flood, Pádraic J. ; Theeuwen, Tom P.J.M. ; Schneeberger, Korbinian ; Keizer, Paul ; Kruijer, Willem ; Severing, Edouard ; Kouklas, Evangelos ; Hageman, Jos A. ; Wijfjes, Raúl ; Calvo-Baltanas, Vanesa ; Becker, Frank F.M. ; Schnabel, Sabine K. ; Willems, Leo A.J. ; Ligterink, Wilco ; Arkel, Jeroen Van; Mumm, Roland ; Gualberto, José M. ; Savage, Linda ; Kramer, David M. ; Keurentjes, Joost J.B. ; Eeuwijk, Fred Van; Koornneef, Maarten ; Harbinson, Jeremy ; Aarts, Mark G.M. ; Wijnker, Erik - \ 2020
    Nature Plants 6 (2020)1. - ISSN 2055-026X - p. 13 - 21.
    Assessment of the impact of variation in chloroplast and mitochondrial DNA (collectively termed the plasmotype) on plant phenotypes is challenging due to the difficulty in separating their effect from nuclear-derived variation (the nucleotype). Haploid-inducer lines can be used as efficient plasmotype donors to generate new plasmotype–nucleotype combinations (cybrids)1. We generated a panel comprising all possible cybrids of seven Arabidopsis thaliana accessions and extensively phenotyped these lines for 1,859 phenotypes under both stable and fluctuating conditions. We show that natural variation in the plasmotype results in both additive and epistatic effects across all phenotypic categories. Plasmotypes that induce more additive phenotypic changes also cause more epistatic effects, suggesting a possible common basis for both additive and epistatic effects. On average, epistatic interactions explained twice as much of the variance in phenotypes as additive plasmotype effects. The impact of plasmotypic variation was also more pronounced under fluctuating and stressful environmental conditions. Thus, the phenotypic impact of variation in plasmotypes is the outcome of multi-level nucleotype–plasmotype–environment interactions and, as such, the plasmotype is likely to serve as a reservoir of variation that is predominantly exposed under certain conditions. The production of cybrids using haploid inducers is a rapid and precise method for assessment of the phenotypic effects of natural variation in organellar genomes. It will facilitate efficient screening of unique nucleotype–plasmotype combinations to both improve our understanding of natural variation in these combinations and identify favourable combinations to enhance plant performance.
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