Lauri Mehtätalo

• Dr. Sc.
• Research professor at Natural Resources Institute Finland (Luke)

In circular plot sampling, trees within a given distance from the sample plot location constitute a sample, which is used to infer characteristics of interest for the forest area. If the sample is collected using a technical device located at the sampling point, e.g. a terrestrial laser scanner, all trees of the sample plot cannot be observed becau...

Individual tree heights are needed in many situations, including estimation of tree volume, dominant height, and simulation of tree growth. However, height measurements are tedious compared to tree diameter measurements, and therefore height–diameter (H–D) models are commonly used for prediction of tree height. Previous studies have fitted H–D mode...

The volume models that have been used in Finland for the last 40 years, while generally well thought-out, exhibit an illogical behaviour for small trees. In recent studies, tree stem form was observed to have changed in time and also involve spatial variation attributable to environmental factors. It is yet unclear how the stem taper has actually c...

Biometry for Forestry and Environmental Data with Examples in R focuses on statistical methods that are widely applicable in forestry and environmental sciences, but it also includes material that is of wider interest. Features: · Describes the theory and applications of selected statistical methods and illustrates their use and basic concepts th...

Aims Climate change‐induced changes in vegetation may be at first subtle and occur only locally within the ecosystem, complicating their reliable detection. We aimed to quantify short‐term changes in species and trait composition in a moss‐dominated ecosystem and to examine the associated uncertainty at the local and study area scales. Location Pr...

Forest planning requires unbiased and sufficient information on current forest resources, their anticipated dynamics under different management scenarios, and the objectives of the decision maker. Forest planning systems need to be adapted to improve their potential to deal with continuous cover forestry (CCF). The current forest planning systems a...

Societal Impact Statement Forests worldwide face significant challenges due to climate change, impacting their health and productivity. In this study, we examined how European beech and Scots pine influence each other's phenology and growth in mixed forests. Our findings indicate that mixing these complementary tree species can increase resource ef...

Here we address the combined impact of multiple stressors that are becoming more common with climate change. To study the combined effects of a lower water table (WT) and increased frequency of drought periods on the resistance and resilience of peatlands, we conducted a mesocosm experiment. This study evaluated how the photosynthesis of lawn Sphag...

A common task in forestry is to determine the value of a forest property, and timber is the most valuable component of that property. Remotely sensed data collected by an unoccupied aerial vehicle (UAV) are suited for this purpose as most forest properties are of a size that permits the efficient collection of UAV data. These UAV data, when linked...

Joint species distribution models (JSDM) are among the most important statistical tools in community ecology. However, existing JSDMs cannot model mutual exclusion between species. We tackle this deficiency in the context of modeling plant percentage cover data, where mutual exclusion arises from limited growing space and competition for light. We...

Highlights • Forest resources maps without uncertainty assessment may lead to false impression of precision. • Suitable tools for visualization of map products are lacking. • Kriging method provided accurate uncertainty assessment for pixel-level predictions. • Quantile random forest algorithm slightly underestimated the pixel-level uncertainties....

Wood production in peatland forests is often associated with management of site hydrology that aims to improve soil moisture status and stand growth. Silvicultural outcomes of ditching activities vary greatly among drained sites, therefore new data and modelling approaches are necessary for better understanding of forest growth dynamics on a tree-l...

During deep snow conditions, wildlife must balance between minimizing movements to conserve energy while seeking high amounts of browse to gain the energy. Knowledge of how snow begins to hinder their movements is therefore vital when predicting their wintertime behavior. We assessed the phenomenon with moose. Movement data from 122 GPS-collared mo...

Characterizing seedling stands with respect to their species proportions and co-occurring vegetation is important for monitoring the desired development of the forest stand. Related inventory information has traditionally been collected with costly field surveys and National Forest Inventory (NFI)-based models. Here, we present a novel fusion appro...

Bush encroachment affects much of the Namibian woodland landscape, causing significant loss of open savannah habitat and farm profits. Thinning of the trees/shrubs is recommended; however,research is required to identify the overall efficacy and effects of this method on the woodland habitat. We aimed to examine the effect of the thinning strategy...

This is a supplementary file of functions in R, which requires to run examples in parameter recovery of Weibull function. For more details, see another supplementary file, "Parameter recovery of Weibull function (public version)". The methodology was originally developed by Jouni Siipilehto and Lauri Mehtätalo. Later, the Rscript of the functions...

Airborne Laser Scanning (ALS) results in point-wise measurements of canopy height, which can further be used for Individual Tree Detection (ITD). However, ITD cannot find all trees because small trees can hide below larger tree crowns. Here we discuss methods where the plot totals and means of tree-level characteristics are estimated in such contex...

This research reviews the factors that are associated with the willingness of forest owners to participate in cross-boundary management of capercaillie (Tetrao urogallus) lekking sites. The data were collected with a double-sampling survey that was targeted at Finnish forest owners. Our findings infer that forest owners are quite often willing to p...

Climate change and the related increases in evapotranspiration threaten to make northern peatlands drier. The carbon sink function in peatlands is based on the delicate balance between the photosynthesis and decomposition. However, little is known about how existing and invading plant species will photosynthesize under drier conditions. The aim of...

My talk on UEF data-driven seminar about "The benefit of subject-matter theory in model building: the case of tree stem volume." We propose a new variable form-factor function for modelling tree stem volume and use it in an extensive data set of three species in data sets where part has been collected manually and part using terrestrial laser scann...

Purpose of Review Growth equations have been widely used in forest research, commonly to assess ecosystem-level behavior and forest management. Nevertheless, the large number of growth equations has obscured the growth-rate behavior of each of these equations and several different terms for referring to common phenomena. This review presents a unif...

Horvitz–Thompson-like stand density estimation is a method for estimating the stand density from tree crown objects extracted from airborne laser scanning data through individual tree detection. The estimator is based on stochastic geometry and mathematical morphology of the (planar) set formed by the detected tree crowns. This set is used to appro...

The increasing availability of wall-to-wall remote sensing datasets in combination with accurate field data enables the mapping of different ecosystem services more accurately and over larger areas than before. The provision of wild berries is an essential ecosystem service, and berries are the most used non-wood forest products in Nordic countries...

Joint species distribution models (JSDM) are among the most important statistical tools in community ecology. However, existing JSDMs cannot model mutual exclusion between species. We tackle this deficiency by developing a novel hierarchical JSDM with Dirichlet-Multinomial observation process for mutually exclusive species groups. We apply non-stat...

The spatial structure of a forest stand is typically modeled by spatial point process models. Motivated by aerial forest inventories and forest dynamics in general, we propose a sequential spatial approach for modeling forest data. Such an approach is better justified than a static point process model in describing the long-term dependence among th...

Remote sensing is increasingly used in collecting data for forest inventories. Especially, aerial and terrestrial laser scanners are used to collect three-dimensional information about the forest. In aerial laser scanning, a laser scanner is installed to airplane or a drone and the device is used to collect information about the forest canopy bel...

Forest management inventories assisted by airborne laser scanning (ALS) can be used to predict different forest attributes. These predictions are utilized in practical forestry, but in the case of timber assortment-specific volumes, the ALS-based predictions can be inaccurate. This causes uncertainty in harvest planning. However, ALS-based predicti...

Nutrition experts know by their experience that people can react very differently to the same nutrition. If we could systematically quantify these differences, it would enable more personal dietary understanding and guidance. This work proposes a mixed-effect Bayesian network as a method for modeling the multivariate system of nutrition effects. Es...

Accumulation of secondary metabolites may exhibit developmentally regulated variation in different plant organs. Moreover, prevailing environmental conditions may interact with development-related variations in plant traits. In this study, we examined developmentally regulated variation in phenolic accumulation in the twigs of dioecious Populus tre...

One of the main rules of subtitling states that subtitles should be formatted and timed so that viewers have enough time to read and understand the text but also to follow the picture. In this paper we examine the factors that influence the time viewers spend looking at subtitles. We concentrate on the lexical and structural properties of subtitles...

McArthur's foliage height diversity (FHD) has been the gold standard in the determination of structural complexity of forests characterized by LiDAR vertical height profiles. It is based on Shannon's entropy index, which was originally designed to describe evenness in abundances among qualitative typologies, and thus the calculation of FHD involves...

Bush encroachment affects ∼45 million ha of Namibia and, without appropriate restoration measures, it negatively affects rangeland productivity and biodiversity. Thinning is a common method to counteract bush encroachment. The thinning strategy applied in north-central Namibia was assessed to examine how effective it has been in reducing bush encro...

Bush encroachment affects ~45 million ha of Namibia and, without appropriate restoration measures, it negatively affects rangeland productivity and biodiversity. Thinning is a common method to counteract bush encroachment. The thinning strategy applied in north-central Namibia was assessed to examine how effective it has been in reducing bush encro...

Objective: Heart rate (HR) monitoring provides a convenient and inexpensive way to predict energy expenditure (EE) during physical activity. However, there is a lot of variation among individuals in the EE-HR relationship, which should be taken into account in predictions. The objective is to develop a model that allows the prediction of EE based...

The behavior of organisms can be subject to human‐induced selection such as that arising from fishing. Angling is expected to induce mortality on fish with bold and explorative behavior, which are behaviors commonly linked to a high standard metabolic rate. We studied the transgenerational response of brown trout (Salmo trutta) to angling‐induced s...

Accumulation of certain phenolics is a well‐known response of plants to enhanced UVB radiation (280–315 nm), but few experiments have compared the relative importance of different phenolic groups for UVB resilience. To study how an altered phenolic profile affects the responses and resilience of silver birch (Betula pendula) to enhanced UVB, we use...

The aim of the study was to evaluate the current level of awareness, implementation and need for knowledge of game-oriented forest management (GOFM) among forest owners and professionals. This information is necessary to understand the grounds for improving awareness and implementation of new forest management guidelines and to evaluate suitable po...

In many countries, airborne laser scanning (ALS) inventories are implemented to produce predictions for stand-level forest attributes. Nevertheless, mature stands are usually field-visited prior to clear-cutting, so some measurements can be conducted on these stands to calibrate the ALS-based predictions. In this paper, we developed a seemingly unr...

Agriculture is considered the backbone of the Namibian economy. However, bush encroachment affects approximately 45 million hectares of Namibian farmland and in the absence of appropriate restoration measures, negatively affects local biodiversity and the national economy. Bush thinning operations on three freehold farms were assessed to examine th...

We quantified the role of spatially varying vegetation composition in seasonal and interannual changes in a boreal bog’s CO2 uptake. We divided the spatially heterogeneous site into six microform classes based on plant species composition and measured their net ecosystem exchange (NEE) using chamber method over the growing seasons in 2012–2014. A n...

A linear model contains two parts, the fixed, or systematic part and the residual error. The formulation of the systematic part is discussed using quantitative and categorical predictors. Using theoretical knowledge of the underlying process is emphasized in the model formulation. In addition, it is pointed out that any curvilinear relationship bet...

The chapter describes such concepts of probability calculus which are needed in later chapters. A total of 26 short examples are included to illustrate the concepts using R-scripts and figures. First, concepts related to univariate random variables are presented, including the distribution and density functions of random variables, and the expected...

The chapter discusses statistical aspects related to taper curves (stem curves), which describe how diameter of tree stem depends on the height. The chapter is not intended as a review of taper curve models. Owing to noncircularity of tree stems, standard ways to measure diameters contain measurement errors. If a taper curve model formulated for di...

Tree size can be described with different variables, such as tree diameter, height, volume, or crown width. Based on the standard probability theory, the chapter discusses approaches that can be used in describing and prediction of the marginal distribution of diameters in an area of interest. Similar presentation has not been published before. The...

Nonlinear models are such regression models where the regression function is nonlinear with respect to the parameters. Benefits from such models over the linear models are discussed. Nonlinear models can be parameterized in many different ways, and the role of parameterization is discussed and demonstrated through examples. With nonlinear model, us...

The chapter discusses the effects of measurement errors of regressor variables on estimating parameters of linear and nonlinear regression equations. Three cases are considered: the measurement error is uncorrelated with the true value (the classical case), or it is uncorrelated with the measured value (the Berkson case), or it is correlated both w...

In multivariate models, models are estimated simultaneously for several y-variables. Seemingly unrelated models are such multivariate regression models which could be estimated separately but with simultaneous estimation one can get more precise estimates in some cases. Multivariate mixed-effects models include also random group effects. In simulta...

Often the expected value of the y-variable of a regression has a restricted range. For example, an expected count is positive and expected probability is within the range (0,1). In generalized linear models, this restriction is implemented with a link function. In addition, a theoretically justified distribution is assumed for the response. This ch...

More advanced topics related to linear mixed-effects models are discussed. Extension of the linear mixed effect model to the multiple levels of grouping with both nested and crossed random effects is described in matrix form and demonstrated through real-data examples. A detailed discussion of between-group and within-group effects is included. Wit...

This chapter discusses basic concepts related statistical modeling, estimation of parameters and prediction of random variables. It is emphasized that statistical reasoning is always based on assumptions made by the modeler. The assumptions can be tested only by making some more general assumptions. The modeling possibilities are dependent on the m...

The chapter discusses some special features of forest and environmental experiments. It is emphasized that the target population should be clearly defined. The generalization of the results of forest experiments is often problematic because there are many nuisance factors related to variation among people involved, heterogeneity of forests and vari...

The chapter gives a more in-depth discussion of various topics related to regression. It is discussed what difference it makes whether predictors are fixed or random. It is demonstrated that the ordinary least squares regression and the best linear predictor lead to the same prediction equation. Examples are given how a nonlinear relation between t...

In grouped data sets, observations are assigned to groups, which constitute a sample from a population of groups. Linear mixed-effects models provide a justified analysis method in such cases through introduction of random group effects. Formulation of this model is conveniently done by exploring and modeling the variability among the individual gr...

Climate change has influenced a range of species across the globe. Yet, to state a noted decline in the abundance of a given species as a consequence of a specific environmental change, for instance, spatially explicit long-term data are a prerequisite. This study assessed the extent to which prolonged snow-free periods in autumn and spring have c...

Secondary succession that occurs on abandoned farmlands is an important source of biomass carbon stocks. Both direct and indirect tree biomass estimation methods are applied on forest lands. Using empirical data from 148 uprooted trees, we developed a seemingly unrelated mixed-effects models system for the young silver birch that grows on post agri...

Despite active research, antiherbivore activity of specific plant phenolics remains largely unresolved. We constructed silver birch (Betula pendula) lines with modified phenolic metabolism to study the effects of foliar flavonoids and condensed tannins on consumption and growth of larvae of a generalist herbivore, the autumnal moth (Epirrita autumn...

The purpose of creating regression equations is often to predict unmeasured features based upon more easily obtainable ones. Species-specific height-diameter (H-D) models of trees are an example of this situation and can be defined as either simple or generalized. Simple H-D models express height as a function of tree diameter at the breast height....

Drone applications are becoming increasingly common in the arena of forest management and forest inventories. In particular, the use of photogrammetrically derived drone-based image point clouds (DIPC) in individual tree detection has become popular. Use of an area-based approach (ABA) in small areas has also been considered. However, in-situ field...

Data assimilation (DA) has a broad category of mathematical procedures for updating and calibrating existing predictions or parameter estimates using new observations. Typical DA procedures such as the Kalman filter require that the observations of a variable of interest used in a forecast of this variable to be collected just prior to the updating...

Tree growth is expected to be responsive to climatic drivers across a spectrum of temporal scales, ranging from yearly growth to daily water use and photosynthesis. Automatic dendrometers offer the potential to provide continuous high-resolution measurements of tree radius changes. The signal recorded contains three components: (1) a long-term seas...

The responses in growth and defense after tissue damage are highly variable in plants depending on species, damaged-tissue type and the intensity of damage. The prevailing abiotic conditions can also influence these responses. In this study, our aim was to examine how the removal of lateral vegetative buds affects the growth and accumulation of phe...

In circular plot sampling, trees within a given distance from the sample plot location constitute a sample, which is used to infer characteristics of interest for the forest area. If the sample is collected using a technical device located at the sampling point, e.g. a terrestrial laser scanner, all trees of the sample plot cannot be observed becau...

We model the spatial dynamics of a forest stand by using a special class of spatio-temporal point processes, the sequential spatial point process, where the spatial dimension is parameterized and the time component is atomic. The sequential spatial point processes differ from spatial point processes in the sense that the realizations are ordered se...

Code reviews are an important practice in software development that increases team productivity and improves product quality. They are also examples of remote, computer-mediated asynchronous communications which are prone to the loss of affective information. Prior research has focused on sentiment analysis in source codes, as positive affect has b...

Individual tree heights are needed in many situations, including the estimation of standingvolume, biomass, or change in them in national forest inventories. However, height measurements are tedious compared to tree diameter measurements, and therefore height–diameter (H–D) models are commonly used for prediction of tree height. National forest inv...

The behavior of organisms can be subject to human induced selection such as that arising from fishing. Angling is expected to induce mortality on fish with bold and explorative behavior, which are behaviors commonly linked to a high standard metabolic rate. We studied the transgenerational response of brown trout (Salmo trutta) to angling-induced s...

Errors in individual tree detection and delineation affect diameter distribution predictions based on crown attributes extracted from the detected trees. We develop a methodology for circumventing these problems. The method is based on matching cumulative distribution functions of field measured tree diameter distributions and crown radii distribut...

In an Area Based Approach (ABA) to forest inventories using Airborne Laser Scanning (ALS) data, the sample plot size may vary or the cell size may differ from the plot size. Although this resolution mismatch may cause bias and increase in prediction error, it has not been thoroughly studied. The aim of this study was to clarify the meaning of resol...

Northern peatlands form a major soil carbon (C) stock. With climate change, peatland C mineralization is expected to increase, which in turn would accelerate climate change. A particularity of peatlands is the importance of soil aeration, which regulates peatland functioning and likely modulates the responses to warming climate. Our aim is to asses...

The mean temperature during the potential growing season (April–September) may increase by 1 °C by 2030, and by 4 °C, or even more, by 2100, accompanied by an increase in atmospheric CO2 concentrations of 536–807 ppm, compared to the current climate of 1981–2010, in which atmospheric CO2 is at about 350 ppm. This may affect both the growth and fros...

Northern wetlands with organic soil i.e., mires are significant carbon storages. This key ecosystem service may be threatened by anthropogenic activities and climate change, yet we still lack a consensus on how these major changes affects their carbon sink capacities. We studied how forestry drainage and restoration combined with experimental warmi...

Tree canopies can be seen as 3-dimensional random sets, and the forest canopy of a certain area is the union of these. Airborne laser scanners provide measurements of the forest canopy, and the parameters of interest for forest managers are the individual trees that form this union. Stochastic geometry analyzes random sets that are unions of random...

In boreal woody plants, concentrations of defensive phenolic compounds are expected to be at a high level during the juvenile phase and decrease in maturity, although there is variation between plant species. Females of dioecious species, like most of the Salicaceae, are expected to invest their resources in defense and reproduction, while males ar...

This study examines the potential of airborne laser scanning (ALS) to predict diameter distributions in an even-aged plantation of Eucalyptus urograndis in Brazil. The single-species plantation conditions allow different modelling alternatives to be compared without the presence of minor tree species or an understory layer affecting the results. Th...

Climate change affects peatlands directly through increased air temperatures and indirectly through changes in water-table level (WL). The interactions of these two still remain poorly known. We determined experimentally the separate and interactive effects of temperature and WL regime on factors of relevance for the inputs to the carbon cycle: pla...

Presentation

A poster based on our 2015 CJFR paper.

According to section 6 of the Constitution of Finland, everyone is equal before the law. In sentencing equality means that, in principle, the same criminal act should be sentenced by the same punishment regardless of where the act has been committed and who gives the judgment. In this multilevel study, we analyze criminal sentencing decisions with...

In trees, the change from juvenile to adult vegetative phase can last for years. In Populus tremula L., this phase change is characterized by a morphological change in leaf shape, as leaves in the seedling phase typically are sharp-tipped, while saplings and trees have round-tipped leaves. In an open-field experiment, we studied the separate and co...

This article introduces a novel methodology for automated classification of forest areas from airborne laser scanning (ALS) datasets based on two direct and simple rules: L-coefficient of variation and L-skewness , thresholds based on descriptors of the mathematical properties of ALS height distributions. We observed that, while may represent fores...

Silver birch (Betula pendula Roth) allocates substantial resources to the production of glandular trichomes. If these trichomes can protect trees from temperature and water stress, their production would be expected to increase under these conditions. We studied how glandular trichome density and number in the leaves of two-year-old silver birch pl...

The European whitefish, Coregonus lavaretus (L.), is a highly polymorphic species consisting of several distinct ecotypes or forms. In the Koitajoki watercourse, southeastern Finland, there exists a pair of indigenous sympatric whitefish ecotypes with distinct gill raker numbers. In the watercourse, supplemental stocking was initiated in the 1960s...

We used national scenario analyses to examine the effects of harvesting intensity on the development of forest resources, timber supply, carbon balance, and biodiversity indicators of Finnish forestry in nine 10-year simulation periods (90-year simulation period) under the current climate. Data from the 11th National Forest Inventory of Finland wer...

Abstract This study explored the effect of training on investigative interviewers’ attitudes and beliefs related to child sexual abuse (CSA). The one-year training provided knowledge about the influence of attitudes and beliefs when investigating alleged crimes against children, guidance for using an interview protocol developed by National Institu...

The growing forest bioeconomy calls for enhancing wood production in Finland. Accordingly, we studied phenotypic differences and correlations for growth and wood density traits in 25 Norway spruce (Picea abies (L.) Karst.) genotypes grown in a field trial established in the 1970s in southeastern Finland. We also studied the effect of the geographic...