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.

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    We will mail you new results for this query: keywords==Connectivity
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Low genetic connectivity in a fouling amphipod among man-made structures in the southern North Sea
Luttikhuizen, P.C. ; Beermann, J. ; Crooijmans, R.P.M.A. ; Jak, R.G. ; Coolen, J.W.P. - \ 2019
Marine Ecology Progress Series 615 (2019). - ISSN 0171-8630 - p. 133 - 142.
Genetic strucutre - Connectivity - Offshore oil platform - Offshore wind farm - Amphipod - Biofouling - Gene flow
Offshore environments are increasingly invaded by man-made structures that form hard-substrate habitats for many marine species. Examples include oil and gas platforms, wind turbines and shipwrecks. One of the hypothesised effects is an increased genetic connectivity among natural populations due to new populations growing on man-made structures that may act as stepping stones. However, few data are available on genetic connectivity among organisms
inhabiting artificial offshore structures. Here, we present a study on the common fouling amphipod Jassa herdmani from offshore structures in the southern North Sea. Partial mitochondrial DNA sequences (cytochrome-c-oxidase 1, N = 514) were obtained from artificial structures at 17 locations in the southern North Sea, including 13 shipwrecks, 2 wind turbines and 2 platforms. Samples from these locations were significantly differentiated, meaning that strong population
structure exists for this species in the area. Levels of intraspecific variation were consistent with stable population sizes. No evidence was found for isolation by distance. Using coalescent simulations, the oldest population subdivision events were estimated to date back to the time the study area was flooded following the Last Glacial Maximum. We therefore tentatively conclude that J. herdmani may have colonised man-made structures from previously existing populations on the
sea floor, and that the increase in offshore installations has not led to an overall increase in genetic connectivity for this species.
Soil-related sustainable development goals : Four concepts to make land degradation neutrality and restoration work
Keesstra, Saskia ; Mol, Gerben ; Leeuw, Jan de; Okx, Joop ; Molenaar, Co ; Cleen, Margot de; Visser, Saskia - \ 2018
Land 7 (2018)4. - ISSN 2073-445X
Connectivity - Land degradation neutrality - Land use planning - Nature-based solutions - Regenerative economy - Soil-water system

In the effort to achieve the Sustainable Development Goals (SDGs) related to food, health, water, and climate, an increase in pressure on land is highly likely. To avoid further land degradation and promote land restoration, multifunctional use of land is needed within the boundaries of the soil-water system. In addition, awareness-raising, a change in stakeholders' attitudes, and a change in economics are essential. The attainment of a balance between the economy, society, and the biosphere calls for a holistic approach. In this paper, we introduce four concepts that we consider to be conducive to realizing LDN in a more integrated way: systems thinking, connectivity, nature-based solutions, and regenerative economics. We illustrate the application of these concepts through three examples in agricultural settings. Systems thinking lies at the base of the three others, stressing feedback loops but also delayed responses. Their simultaneous use will result in more robust solutions, which are sustainable from an environmental, societal, and economic point of view. Solutions also need to take into account the level of scale (global, national, regional, local), stakeholders' interests and culture, and the availability and boundaries of financial and natural capital. Furthermore, sustainable solutions need to embed short-term management in long-term landscape planning. In conclusion, paradigm shifts are needed. First, it is necessary to move from excessive exploitation in combination with environmental protection, to sustainable use and management of the soil-water system. To accomplish this, new business models in robust economic systems are needed based on environmental systems thinking; an approach that integrates environmental, social, and economic interests. Second, it is necessary to shift from a "system follows function" approach towards a "function follows system" one. Only by making the transition towards integrated solutions based on a socio-economical-ecological systems analysis, using concepts such as nature-based solutions, do we stand a chance to achieve Land Degradation Neutrality by 2030. To make these paradigm shifts, awareness-raising in relation to a different type of governance, economy and landscape and land-use planning and management is needed.

The way forward : Can connectivity be useful to design better measuring and modelling schemes for water and sediment dynamics?
Keesstra, Saskia ; Nunes, Joao P. ; Saco, Patricia ; Parsons, Tony ; Poeppl, Ronald ; Masselink, Rens ; Cerdà, Artemi - \ 2018
Science of the Total Environment 644 (2018). - ISSN 0048-9697 - p. 1557 - 1572.
Agricultural impacts - Boundary conditions - Catchment systems - Co-evolution - Connectivity - Fire effects - Management - Measuring and modelling approaches - Pollutant transport

For many years, scientists have tried to understand, describe and quantify water and sediment fluxes, with associated substances like pollutants, at multiple scales. In the past two decades, a new concept called connectivity has been used by Earth Scientists as a means to describe and quantify the influences on the fluxes of water and sediment on different scales: aggregate, pedon, location on the slope, slope, watershed, and basin. A better understanding of connectivity can enhance our comprehension of landscape processes and provide a basis for the development of better measurement and modelling approaches, further leading to a better potential for implementing this concept as a management tool. This paper provides a short review of the State-of-the-Art of the connectivity concept, from which we conclude that scientists have been struggling to find a way to quantify connectivity so far. We adapt the knowledge of connectivity to better understand and quantify water and sediment transfers in catchment systems. First, we introduce a new approach to the concept of connectivity to study water and sediment transfers and the associated substances. In this approach water and sediment dynamics are divided in two parts: the system consists of phases and fluxes, each being separately measurable. This approach enables us to: i) better conceptualize our understanding of system dynamics at different timescales, including long timescales; ii) identify the main parameters driving system dynamics, and devise monitoring strategies which capture them; and, iii) build models with a holistic approach to simulate system dynamics without excessive complexity. Secondly, we discuss the role of system boundaries in designing measurement schemes and models. Natural systems have boundaries within which sediment connectivity varies between phases; in (semi-)arid regions these boundaries can be far apart in time due to extreme events. External disturbances (eg. climate change, changed land management) can change these boundaries. It is therefore important to consider the system state as a whole, including its boundaries and internal dynamics, when designing and implementing comprehensive monitoring and modelling approaches. Connectivity is a useful tool concept for scientists that must be expanded to stakeholder and policymakers.

Connectivity assessment in Mediterranean vineyards using improved stock unearthing method, LiDAR and soil erosion field surveys
Rodrigo Comino, Jesús ; Keesstra, Saskia D. ; Cerdà, Artemi - \ 2018
Earth Surface Processes and Landforms 43 (2018)10. - ISSN 0197-9337 - p. 2193 - 2206.
Connectivity - ISUM - Sediment transport - Slope positions - Vineyards

The interaction between processes and landforms is accelerated in vineyards due to bare tilled soils that enhance splash, runoff, and erosion. Traditionally, in order to assess these processes, the stock unearthing method (SUM) is considered a useful methodology that uses the graft union of the vine plant as passive bio-indicator of the topsoil level changes. However, SUM assumes that the topography between the rows is planar when development of a model of the current micro-topography is performed. Thus, we consider that there is a need to develop a new methodology (ISUM: improved SUM) that, by adding new measurements in the inter-row areas (at least 3), allows inclusion of the absent micro-topographical information of SUM. In this way, the main aim of this research was to estimate the micro-topographical changes and soil transport at three different slope positions (upper, middle and lower parts) in a 25-years-old vineyard in eastern Spain. LiDAR data were used to compare the connectivity processes at the catchment with the pedon scale. We obtained maps that showed topsoil level changes and detected soil depletion and accumulation signals. We estimated soil displacement rates of -1.6Mghayr-1 (depletion), +2.8Mghayr-1 and +13.3Mghayr-1 (accumulation) at upper, middle and lower slope positions, respectively. The total average soil erosion rates in the inter-rows were -5.7Mgha-1 yr-1. In the row areas, deposition of +10.5Mghayr-1 was measured. Field erosion marks surveyed after each rainfall event gave insights to the connectivity at the inter-row and the slope scale. It was found that at the row scale there were sinks of sediments underneath the vines and sources in the inter-row parts, although they are the highest and lowest local topographical terrain, respectively. This is due to tillage erosion that redistributed the sediments. At the slope scale, the lower part of the slope collected sediments from the upper slope positions, which were transported along the middle part of the slope, as the measurement of ISUM and the field survey after intense rainfall events demonstrated. Connectivity of the flows along the whole slope were rare (twice), and along individual slope parts connectivity was found eight times, and 19 at the inter-row scale after 8years of field observations.

Lessons learned from practical approaches to reconcile mismatches between biological population structure and stock units of marine fish
Kerr, Lisa A. ; Hintzen, Niels T. ; Cadrin, Steven X. ; Clausen, Lotte Worsøe ; Dickey-Collas, Mark ; Goethel, Daniel R. ; Hatfield, Emma M.C. ; Kritzer, Jacob P. ; Nash, Richard D.M. - \ 2017
ICES Journal of Marine Science 74 (2017)6. - ISSN 1054-3139 - p. 1708 - 1722.
Biocomplexity - Connectivity - Fisheries management - Population structure - Spatial structure - Stock assessment - Stock identification

Recent advances in the application of stock identification methods have revealed inconsistencies between the spatial structure of biological populations and the definition of stock units used in assessment and management. From a fisheries management perspective, stocks are typically assumed to be discrete units with homogeneous vital rates that can be exploited independently of each other. However, the unit stock assumption is often violated leading to spatial mismatches that can bias stock assessment and impede sustainable fisheries management. The primary ecological concern is the potential for overexploitation of unique spawning components, which can lead to loss of productivity and reduced biodiversity along with destabilization of local and regional stock dynamics. Furthermore, ignoring complex population structure and stock connectivity can lead to misperception of the magnitude of fish productivity, which can translate to suboptimal utilization of the resource. We describe approaches that are currently being applied to improve the assessment and management process for marine fish in situations where complex spatial structure has led to an observed mismatch between the scale of biological populations and spatially-defined stock units. The approaches include: (i) status quo management, (ii) "weakest link" management, (iii) spatial and temporal closures, (iv) stock composition analysis, and (v) alteration of stock boundaries. We highlight case studies in the North Atlantic that illustrate each approach and synthesize the lessons learned from these real-world applications. Alignment of biological and management units requires continual monitoring through the application of stock identification methods in conjunction with responsive management to preserve biocomplexity and the natural stability and resilience of fish species.

Isolation by oceanic distance and spatial genetic structure in an overharvested international fishery
Truelove, Nathan K. ; Box, Stephen J. ; Aiken, Karl A. ; Blythe-Mallett, Azra ; Boman, Erik M. ; Booker, Catherine J. ; Byfield, Tamsen T. ; Cox, Courtney E. ; Davis, Martha H. ; Delgado, Gabriel A. ; Glazer, Bob A. ; Griffiths, Sarah M. ; Kitson-Walters, Kimani ; Kough, Andy S. ; Pérez Enríquez, Ricardo ; Preziosi, Richard F. ; Roy, Marcia E. ; Segura-García, Iris ; Webber, Mona K. ; Stoner, Allan W. - \ 2017
Diversity and Distributions 23 (2017)11. - ISSN 1366-9516 - p. 1292 - 1300.
Connectivity - Conservation - Dispersal - Fisheries - Genetics - Spatial

Aim: A detailed understanding of spatial genetic structure (SGS) and the factors driving contemporary patterns of gene flow and genetic diversity are fundamental for developing conservation and management plans for marine fisheries. We performed a detailed study of SGS and genetic diversity throughout the overharvested queen conch (Lobatus gigas) fishery. Caribbean countries were presented as major populations to examine transboundary patterns of population differentiation. Location: Nineteen locations in the greater Caribbean from Anguilla, the Bahamas, Belize, Caribbean Netherlands, Honduras, Jamaica, Mexico, Turks and Caicos, and the USA. Methods: We genotyped 643 individuals with nine microsatellites. Population genetic and multivariate analyses characterized SGS. We tested the alternate hypotheses: (1) SGS is randomly distributed in space or (2) pairwise genetic structure among sites is correlated with oceanic distance (IBOD). Results: Our study found that L. gigas does not form a single panmictic population in the greater Caribbean. Significant levels of genetic differentiation were identified between Caribbean countries (FCT = 0.011; p = .0001), within Caribbean countries (FSC = 0.003; p = .001), and among sites irrespective of geographic location (FST = 0.013; p = .0001). Gene flow across the greater Caribbean was constrained by oceanic distance (p = .0009; Mantel r = .40), which acted to isolate local populations. Main conclusions: Gene flow over the spatial scale of the entire Caribbean basin is constrained by oceanic distance, which may impede the natural recovery of overfished L. gigas populations. Our results suggest a careful blend of local and international management will be required to ensure long-term sustainability for the species.

Runoff initiation, soil detachment and connectivity are enhanced as a consequence of vineyards plantations
Cerdà, Artemi ; Keesstra, S.D. ; Rodrigo Comino, Jesús ; Novara, A. ; Pereira, P. ; Brevik, E.C. ; Giménez-Morera, A. ; Fernández-Raga, M. ; Mahecha-Pulido, Juan D. ; Prima, Simone Di; Jordán, Antonio - \ 2017
Journal of Environmental Management 202 (2017)1. - ISSN 0301-4797 - p. 268 - 275.
Connectivity - Detachment - Erosion - Rainfall simulation - Sediments - Water
Rainfall-induced soil erosion is a major threat, especially in agricultural soils. In the Mediterranean belt, vineyards are affected by high soil loss rates, leading to land degradation. Plantation of new vines is carried out after deep ploughing, use of heavy machinery, wheel traffic, and trampling. Those works result in soil physical properties changes and contribute to enhanced runoff rates and increased soil erosion rates. The objective of this paper is to assess the impact of the plantation of vineyards on soil hydrological and erosional response under low frequency – high magnitude rainfall events, the ones that under the Mediterranean climatic conditions trigger extreme soil erosion rates. We determined time to ponding, Tp; time to runoff, Tr; time to runoff outlet, Tro; runoff rate, and soil loss under simulated rainfall (55 mm h−1, 1 h) at plot scale (0.25 m2) to characterize the runoff initiation and sediment detachment. In recent vine plantations (<1 year since plantation; R) compared to old ones (>50 years; O). Slope gradient, rock fragment cover, soil surface roughness, bulk density, soil organic matter content, soil water content and plant cover were determined. Plantation of new vineyards largely impacted runoff rates and soil erosion risk at plot scale in the short term. Tp, Tr and Tro were much shorter in R plots. Tr-Tp and Tro-Tr periods were used as connectivity indexes of water flow, and decreased to 77.5 and 33.2% in R plots compared to O plots. Runoff coefficients increased significantly from O (42.94%) to R plots (71.92%) and soil losses were approximately one order of magnitude lower (1.8 and 12.6 Mg ha−1 h−1 for O and R plots respectively). Soil surface roughness and bulk density are two key factors that determine the increase in connectivity of flows and sediments in recently planted vineyards. Our results confirm that plantation of new vineyards strongly contributes to runoff initiation and sediment detachment, and those findings confirms that soil erosion control strategies should be applied immediately after or during the plantation of vines.
A network theory approach for a better understanding of overland flow connectivity
Masselink, Rens J.H. ; Heckmann, Tobias ; Temme, Arnaud J.A.M. ; Anders, Niels S. ; Gooren, Harm P.A. ; Keesstra, Saskia D. - \ 2017
Hydrological Processes 31 (2017)1. - ISSN 0885-6087 - p. 207 - 220.
Connectivity - Graph theory - Networks - Overland flow - Spain

Hydrological connectivity describes the physical coupling (linkages) of different elements within a landscape regarding (sub-) surface flows. A firm understanding of hydrological connectivity is important for catchment management applications, for example, habitat and species protection, and for flood resistance and resilience improvement. Thinking about (geomorphological) systems as networks can lead to new insights, which has also been recognized within the scientific community, seeing the recent increase in the use of network (graph) theory within the geosciences. Network theory supports the analysis and understanding of complex systems by providing data structures for modelling objects and their linkages, and a versatile toolbox to quantitatively appraise network structure and properties. The objective of this study was to characterize and quantify overland flow connectivity dynamics on hillslopes in a humid sub-Mediterranean environment by using a combination of high-resolution digital-terrain models, overland flow sensors and a network approach. Results showed that there are significant differences between overland flow connectivity on agricultural areas and semi-natural shrubs areas. Significant positive correlations between connectivity and precipitation characteristics were found. Significant negative correlations between connectivity and soil moisture were found, most likely because of soil water repellency and/or soil surface crusting. The combination of structural networks and dynamic networks for determining potential connectivity and actual connectivity proved a powerful tool for analysing overland flow connectivity.

Modelling Discharge and Sediment Yield at Catchment Scale Using Connectivity Components
Masselink, Rens J.H. ; Keesstra, Saskia D. ; Temme, Arnaud J.A.M. ; Seeger, Manuel ; Giménez, Rafael ; Casalí, Javier - \ 2016
Land Degradation and Development 27 (2016)4. - ISSN 1085-3278 - p. 933 - 945.
Connectivity - Discharge - Model - N-Spain - Sediment yield

Knowledge about connectivity and what affects it, through space and time, is needed for taking appropriate action at the right place and/or time by stakeholders. Various conceptual frameworks for hydrological and sediment connectivity have been developed in recent years. For most of these frameworks, the objective was to conceptualise connectivity, not necessarily to infer it from measurements. Studies focussing on measurements of connectivity have so far not been done often. Because of lack of data on connectivity, few real-world data have been used in recent connectivity modelling studies. The aim of this study was to demonstrate that existing data can be used to assess governing factors of connectivity, and how these change over time. Data from three catchments in Navarre, Northern Spain, were used to assess factors that influence hydrologic and sediment connectivity. These factors were used as components in a linear model for discharge and suspended-sediment yield. Three components of connectivity were distinguished: topographical, biological and soil. Changes in the topographical component for the studied periods were considered relatively small, and, therefore, kept constant. Changes in the biological component were determined using the Normalised Difference Vegetation Index. Changes in the soil component were assessed using an Antecedent Precipitation Index. Nash-Sutcliffe model efficiency coefficients were between 0·49 through 0·62 for the discharge models and between 0·23 through 0·3 for the sediment-yield models. We recommend applying the model at smaller spatial scales than catchment scale to minimise the lumping of spatial variability in the components.

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