Dick J Brus

Mapping of environmental variables often relies on map accuracy assessment through cross-validation with the data used for calibrating the underlying mapping model. When the data points are spatially clustered, conventional cross-validation leads to optimistically biased estimates of map accuracy. Several papers have promoted spatial cross-validati...

For many decades, soil scientists have produced spatial estimates of soil properties using statistical and non-statistical mapping models. Commonly in soil mapping studies the map quality is assessed through pairwise comparison of observed and predicted values of a soil property, from which statistical indices summarizing the quality of the entire...

A crucial decision in designing a spatial sample for soil survey is the number of sampling locations required to answer, with sufficient accuracy and precision, the questions posed by decision makers at different levels of geographic aggregation. In the Indian Soil Health Card (SHC) scheme, many thousands of locations are sampled per district. In t...

For decades scientists have produced maps of biological, ecological and environmental variables. These studies commonly evaluate the map accuracy through cross-validation with the data used for calibrating the underlying mapping model. Recent studies, however, have argued that cross-validation statistics of most mapping studies are optimistically b...

Spatial soil applications frequently involve binomial variables. If relevant environmental covariates are available, using a Bayesian generalized linear model (BGLM) might be a solution for mapping such discrete soil properties. The geostatistical extension, a Bayesian generalized linear geostatistical model (BGLGM), adds spatial dependence and is...

Knowledge of how many sampling points are needed to estimate the mean content of soil nutrients in agricultural fields, given a precision requirement on the estimated mean, is limited. This paper describes a versatile geo-statistical simulation approach for predicting the variance of the mean nitrate-N (NO3-N) content within an agricultural field e...

This study investigates sampling design for mapping soil classes based on multiple environmental features associated with the soil classes. Two types of sampling design for calibrating the prediction models are compared: conditioned Latin hypercube sampling (CLHS) and feature space coverage sampling (FSCS). Simple random sampling (SRS), which does...

It is commonly accepted that an estimated soil variogram can be transferred to another similar area for deriving the tolerable spacing of a sampling grid or, more generally, the sample size, given a requirement on the quality of the soil property map of the recipient area. The quality of the derived tolerable grid spacing depends on how similar the...

Several misconceptions about the design‐based approach for sampling and statistical inference, based on classical sampling theory, seem to be quite persistent. These misconceptions are the result of confusion about basic statistical concepts such as independence, expectation, and bias and variance of estimators or predictors. These concepts have a...

If a map is constructed through prediction with a statistical or non‐statistical model, the sampling design used for selecting the sample on which the model is fitted plays a key role in the final map accuracy. Several sampling designs are available for selecting these calibration samples. Commonly, sampling designs for mapping are compared in real...

Area-to-point kriging (ATPK) is a geostatistical method for creating high-resolution raster maps using data of the variable of interest with a much lower resolution. The data set of areal means is often considerably smaller (<50 observations) than data sets conventionally dealt with in geostatistical analyses. In contemporary ATPK methods, uncertai...

Machine learning techniques are widely employed to generate digital soil maps. The map accuracy is partly determined by the number and spatial locations of the measurements used to calibrate the machine learning model. However, determining the optimal sampling design for mapping with machine learning techniques has not yet been considered in detail...

Soils are among the most biodiverse and densely inhabited environments on our planet. However, there is little understanding of spatial distribution patterns of belowground biota, and this hampers progress in understanding species interactions in belowground communities. We investigated the spatial distribution of nematodes, which are highly abunda...

In 1992 pedometrics as a concept became Pedometrics in the formal sense, with the establishment of a Working Group of the International Union of Soil Sciences (IUSS) and a first conference in Wageningen, the Netherlands (de Gruijter et al., 1994). To celebrate its 25th anniversary, the pedometrics community therefore convened again in Wageningen in...

In areas with marked differences in accessibility, cost efficiency of design‐based sampling strategies for estimating the population mean or total can be increased by accounting for these differences in the selection of the sampling locations. This can be achieved by stratified random sampling. The question then is how to construct the strata. Exis...

Simple and ordinary kriging assume a constant mean and variance of the soil variable of interest. This assumption is often implausible because the mean and/or variance are linked to terrain attributes, parent material or other soil forming factors. In kriging with external drift (KED) non-stationarity in the mean is accounted for by modelling it as...

In the past decade, substantial progress has been made in model-based optimization of sampling designs for mapping. This paper is an update of the overview of sampling designs for mapping presented by de Gruijter et al. (2006). For model-based estimation of values at unobserved points (mapping), probability sampling is not required, which opens up...

Crop yield data are often available as statistics of areas, such as administrative units, generated by national agricultural surveys and censuses. This paper shows that such areal data can be used in area-to-point kriging (ATP kriging) to estimate the crop yield at the nodes of a fine grid that discretizes the study area, so that a more detailed ma...

Crop yield data are often available as statistics of areas, such as administrative units, generated by national agricultural surveys and censuses. This paper shows that such areal data can be used in area-to-point kriging (ATP kriging) to estimate the crop yield at the nodes of a fine grid that discretizes the study area, so that a more detailed ma...

One of the first soil forming processes in marine and fluviatile clay soils is ripening, the irreversible change of physical and chemical soil properties, especially consistency, under influence of air. We used Bayesian binomial logistic regression (BBLR) to update the map showing unripened subsoils for a reclamation area in the west of The Netherl...

The quality of soil maps can best be estimated by collecting additional data at locations selected by probability sampling. These data can be used in design-based estimation of map quality measures such as the population mean of the squared prediction errors (MSE) for continuous soil maps and overall accuracy for categorical soil maps. In areas wit...

Although soil compaction is widely recognized as a soil threat to soil resources, reliable estimates of the acreage of overcompacted soil and of the level of soil compaction parameters are not available. In the Netherlands data on subsoil compaction were collected at 128 locations selected by stratified random sampling. A map showing the risk of su...

Sequestering organic carbon (C) in soil can help to combat land degradation, improve food security, and mitigate greenhouse gas emissions and climate change. But we need reliable, cost-efficient methods to assess, monitor, and verify the change. Here, we compared two methods for the direct measurement of soil organic C stocks and for monitoring the...

Although soil compaction is widely recognized as a soil threat to soil resources, reliable estimates of the acreage of overcompacted soil and of the level of soil compaction parameters are not available. In the Netherlands data on soil compaction were collected at 128 locations selected by stratified random sampling. A map showing the risk of soil...

The accuracy of spatial predictions of rainfall by merging rain-gauge and radar data is partly determined by the sampling design of the rain-gauge network. Optimising the locations of the rain-gauges may increase the accuracy of the predictions. Existing spatial sampling design optimisation methods are based on minimisation of the spatially average...

This pdf accompanies the following abstract: Heuvelink GBM, Batjes NH, Brus DJ, Gruiter JJD, McBratney AB and Stockmann U 2017. Towards a sampling desing for monitoring global soil organic carbon stocks. In: Wallinga J, G Mol, VL Mulder, AM Zaal and B Jansen (editors), Wageningen Soil Conference, Wageningen, pp 72. Available at: https://www.wur.nl...

Accurate estimation of the global soil organic carbon (SOC) stock and temporal changes therein are of vital importance for climate-change studies. Most current assessments take a model-based approach to predict SOC spatially and aggregate point predictions to a global SOC stock estimate. Estimates of SOC stock dynamics are derived by repeating this...

The analytical determination of microbial biomass carbon is time‐consuming, which limits its use as a reference biochemical property for characterizing soil fertility and soil biodiversity of soil mapping units (SMUs). This paper explores whether the efficiency of sampling strategies for estimating the means of microbial biomass C (MBC) of SMUs can...

The effect of grid-spacing on the quality of species abundance maps is explored for species that show zero-inflation and spatial autocorrelation. Using a zero-inflated Poisson mixture model multiple fields of the prevalence parameter and the intensity parameter were simulated. A selected field was sampled by grid-sampling with 200, 400, 800, 1600,...

For baselining and to assess changes in soil organic carbon (C) we need efficient soil sampling designs and methods for measuring C stocks. Conventional analytical methods are time-consuming, expensive and impractical, particularly for measuring at depth. Here we demonstrate the use of proximal soil sensors for estimating the total soil organic C s...

The objective of the study was to provide a general procedure for mapping species abundance when data are zero-inflated and spatially correlated counts. The bivalve species Macoma balthica was observed on a 500×500 m grid in the Dutch part of the Wadden Sea. In total, 66% of the 3451 counts were zeros. A zero-inflated Poisson mixture model was used...

This book contains papers presented at the 6th Global Workshop on Digital Soil Mapping, held 11-14 November 2014 at the Institute of Soil Science, Chinese Academy of Sciences of Nanjing, China. Digital soil mapping is advancing on different fronts at different paces throughout the world. The researches and applications on DSM are moving from method...

Summary 1. To evaluate progress on political biodiversity objectives, biodiversity monitoring provides information on whether intended results are being achieved. Despite scientific proof that monitoring and evaluation increase the (cost) efficiency of policy measures, cost estimates for monitoring schemes are seldom available, hampering their inc...

There are various methods to design samples for spatial trend estimation. One of the most used in soil science, the so-called conditioned Latin Hypercube Sampling (cLHS), searches for a spatial sample optimal in terms of 1) coverage of the marginal distribution and 2) linear correlation of numeric covariates, and 3) proportional sample sizes for th...

This paper describes three statistical sampling approaches for regional soil monitoring, a design-based, a model-based and a hybrid approach. In the model-based approach a space-time model is exploited to predict global statistical parameters of interest such as the space-time mean. In the hybrid approach this model is a time-series model of the sp...

The aim of a soil survey is to predict soil conditions at unvisited sites. In traditional soil survey, the use of statistics is principally for post hoc evaluation of the quality of the choropleth map in terms of purity and within- and between-map unit variance of soil properties. Probability sampling designs have been proposed for this. Pedometric...

The summary statistics (SS) approach to area-to-point (ATP) kriging is applied to map organic matter concentration in the topsoil of agricultural fields from aggregated soil testing data. The differences between the SS approach and earlier published ATP kriging methods are explained and the behavior of the SS predictions is illustrated with a simul...

Because of their abundance, their trophic diversity and their relatively straightforward extractability, nematodes have a potential as a proxy for the biological condition of soils and sediments. So far the potential of this group is underexploited for technical reasons; the microscopic analysis of nematode assemblages is labour intensive and requi...

Abstract

A prototype of a next-generation Soil Information System (SIS) has been developed in The Netherlands. This SIS consists of a soil profile database, tools for accessing and processing of the soil profile database and computer scripts for data processing, modelling and mapping. The aim of this study was to extend the SIS with new scripts for mapping...

De bodemkaart onderscheidt allerlei bodemtypen met veenlagen ondiep in het profiel. Door oxidatie en klink neemt de veendikte geleidelijk af. Hierdoor treedt er een verschuiving op in bodemtypen; moerige gronden veranderen in minerale gronden en veengronden in moerige gronden. Vanwege deze dynamiek bij gronden met dunne veenlagen dient de bodemkund...

Kaarten kunnen informatie geven over grotere eenheden, bijvoorbeeld postcodegebieden, of nog kleinere, zoals percelen. Met een variant op een interpolatietechniek is het mogelijk informatie te verkrijgen over een kleiner gebied. We illustreren dit aan de hand van organische stofgehalten in de bodem. De methodiek is breed toepasbaar op allerlei vorm...

The quality of ecotope maps of five districts of main water courses in the Netherlands was assessed on the basis of independent validation samples of field observations. The overall proportion of area correctly classified, and user's and producer's accuracy for each map unit were estimated. In four districts, the validation samples were selected pu...

The aim of a soil survey is to predict soil conditions at unvisited sites. In traditional soil survey, the use of statistics is principally for post hoc evaluation of the quality of the choropleth map in terms of purity and within- and between-map unit variance of soil properties. Probability sampling designs have been proposed for this. Pedometric...

Verschillende kaarten geven de diepte tot het freatische grondwater aan. Voorbeelden zijn de kaart van de grondwaterdynamiek, en kaarten die zijn gemaakt met modelinstrumentaria zoals het Nationaal Hydrologisch Instrumentarium en de hydrologische component van Stone. Om hun bruikbaarheid te kunnen beoordelen moeten we weten hoe nauwkeurig deze kaar...

There is growing urgency for integration and coordination of global environmental and ecological data and indicators required to respond to the ‘grand challenges’ the planet is facing, including climate change and biodiversity decline. A consistent stratification of land into relatively homogenous strata provides a valuable spatial framework for co...

We present the generalised linear geostatistical model (GLGM) for soil type mapping and investigate if spatial prediction with this model results in a soil map of greater accuracy than a map obtained using a non-spatial model, i.e. a model that ignores spatial dependence in the soil type variable. The GLGM is central to the framework of model-based...

This study compared the efficiency of geostatistical digital soil mapping (DSM) with conventional soil mapping (CSM) for updating soil class and property maps of a cultivated peatland in the Netherlands. For digital soil class mapping, the generalized linear geostatistical model was used. Digital mapping of the soil organic matter (SOM) content and...

The acquirement of ground control points (GCPs) is a basic and important step in the geometric correction of remotely sensed imagery. In particular, the spatial distribution of GCPs may affect the accuracy and quality of image correction. In this paper, both a simulation experiment and actual-image analyses are carried out to investigate the effect...

Legacy soil point data stored in soil information systems are a valuable resource for digital soil mapping. For dynamic soil properties, however, these data may not represent the actual field conditions, which may hamper their utility for mapping exercises. Because collection of field data is a major cost component in soil mapping, updating legacy...

This paper launches a hybrid sampling approach, entailing a design-based approach in space followed by a model-based approach in time, for estimating temporal trends of spatial means or totals. Sampling locations are selected by probability sampling, whereas this is not required for selecting sampling times. The underlying space-time process that g...

This paper launches a hybrid sampling approach, entailing a design-based approach in space followed by a model-based approach in time, for estimating temporal trends of spatial means or totals. The underlying space-time process that generated the soil data is only partly described, viz, by a linear mixed model for the temporal variation of the spat...

In large parts of the western coastal region of the Netherlands peat soils occur. Historic land use resulted in decomposition of organic matter and compaction of these soils and as a consequence the land surface subsided. Along with sea level rise and tectonic subsidence since the end of the Weichselian ice-age, this resulted in a country where one...

In the new Dutch decision tree for the evaluation of pesticide leaching to groundwater, spatially distributed soil data are used by the GeoPEARL model to calculate the 90th percentile of the spatial cumulative distribution function of the leaching concentration in the area of potential usage (SP90). Until now it was not known to what extent uncerta...

In order to map the spatial distribution of twenty tree species groups over Europe at 1km × 1km resolution, the ICP-Forest Level-I plot data were extended with the National Forest Inventory (NFI) plot data of eighteen countries. The NFI grids have a much smaller spacing than the ICP grid. In areas with NFI plot data, the proportions of the land are...

Stratification, dividing the statistical population into less heterogeneous subgroups before sampling, can help improve sampling efficiency by improving representativeness and reducing sampling error. This report explores the added sampling efficiency that is achieved by using the European Environmental stratification for estimating the area covere...

De kwaliteit en de ontwikkeling van de natuur dient gemonitord geworden volgens een nieuwe landelijke systematiek in het kader van het Subsidie Stelsel Natuur (SNL). Daarnaast speelt de monitoring voor Natura 2000-gebieden en specifiek voor de verdroging van de TOP-gebieden. In dit rapport wordt een ontwerp gegeven van het meetnet met de steekproef...

Rijkswaterstaat voert in het kader van de Europese Kaderrichtlijn Water projecten uit om de ecologische kwaliteit van rivieren te verbeteren. Projectmonitoring heeft tot doel om te onderzoeken of de projecten zinvol zijn voor de verbetering van de ecologische kwaliteit en verklaringen hiervoor te vinden. Het aantal monsters dat nodig is voor projec...

This chapter reviews methods for selecting sampling locations in contaminated soils for three situations. In the first situation a global estimate of the soil contamination in an area is required. The result of the surey is a number or a series of numbers per contaminant, e.g. the estimated mean concentration, median, 90th percentile, or the cumula...

This paper introduces and demonstrates design-based Generalized Least Squares (GLS) estimation of spatial means at selected time points from data collected in repeated soil surveys with partial overlap, such as a rotating and a supplemented panel. The linear time trend of the spatial means can then be obtained as a linear combination of the estimat...

At present, soil quality standards used for agriculture do not consider the influence of pH and CEC on the uptake of pollutants by crops. A database with 750 selected paired samples of cadmium (Cd) in soil and paddy rice was used to calibrate soil to plant transfer models using the soil metal content, pH, and CEC or soil Cd and Zn extracted by 0.01...

The increase in digital soil mapping around the world means that appropriate and efficient sampling strategies are needed for validation. Data used for calibrating a digital soil mapping model typically are non-random samples. In such a case we recommend collection of additional independent data and validation of the soil map by a design-based samp...

In this paper we introduce additional criteria to assess the quality of digital soil property maps. Soil map quality is estimated on the basis of validating both the accuracy of the predictions and their uncertainties (which are expressed as a prediction interval [PI]). Th e fi rst criterion is an accuracy measure that is diff erent in form to the...

This paper proposes a method for mapping depth functions of soil organic matter (SOM) that combines general pedological knowledge with geostatistical modeling. A pedometric soil map that represents soil type at any location with a probability distribution formed the starting-point. For each of the ten soil types depicted on this map a depth functio...

Modellen en modelketens kunnen een krachtig instrument vormen om het overheidsbeleid op gebieden als stikstofdepositie of klimaatverandering te evalueren. Aangezien op modelsimulaties gebaseerde beslissingen grote maatschappelijke gevolgen kunnen hebben, is kennis van de nauwkeurigheid en de mate van onzekerheid van deze simulaties van groot belang...

Door bodemgebruik en ontwatering oxideert er organische stof in de bodem. Ondiepe veenlagen worden hierdoor geleidelijk dunner, waardoor de bodemopbouw verandert. Door deze veranderingen is actualisatie van de Bodemkaart van Nederland, schaal 1 : 50 000 (BvN), noodzakelijk. In dit onderzoek is gekeken of een recente bodemkaart, de Bodemkaart Veenge...

De uitkomsten van het model STONE zijn gevalideerd op gemeten concentraties in drains en grondwater uit LMM (Landelijk Meetnet effecten Mestbeleid) en gemeten fosfaatophoping volgens LSK (Landelijke Steekproef Kaarteenheden). Voor de validatie is gebruik gemaakt van een in 2008 ontwikkeld protocol. Uit de validatie komt naar voren dat op nationale...

Waterretentie- en doorlatendheidskarakteristiek worden gebruikt in simulatiemodellen voor water- en stoftransport in de onverzadigde zone. De gegevens worden gebruikt in studies naar voedsel- en biomassaproductie, het gebruik van bodem en water als grondstoffen, de emissie van broeikasgassen, het risico van uitspoeling van vervuilende stoffen naar...

A sampling strategy for estimating spatially averaged annual element leaching fluxes from forest soils is presented and tested in three Dutch forest monitoring plots. In this method sampling locations and times (days) are selected by probability sampling. Sampling locations were selected by stratified random sampling with five blocks of equal surfa...

Both for mapping and for estimating spatial means of an environmental variable, the accuracy of the result will usually be increased by dispersing the sample locations so that they cover the study area as uniformly as possible. We developed a new R package for designing spatial coverage samples for mapping, and for random sampling from compact geog...

Element fluxes through forest ecosystems are generally based on measurements of concentrations in soil solution at regular time intervals at plot locations sampled in a regular grid. Here we present spatially averaged annual element leaching fluxes in three Dutch forest monitoring plots using a new sampling strategy in which both sampling locations...

A monitoring scheme has been designed to test whether the space-time mean concentration total Nitrogen (N-total) in the surface water in the Northern Frisian Woodlands (NFW, The Netherlands) complies with standards of the European Water Framework directive. Since in statistical testing for compliance monitoring valid estimators for the mean and its...