Dr. Marielle Fraefel

Efficient forest operations are required for the provision of biodiversity and numerous ecosystem services, such as wood production, carbon sequestration, protection against natural hazards and recreation. In numerous countries, under difficult terrain conditions, the costs of forest management and harvesting are not covered by timber revenue. One possible option to increase the cost-effectiveness of the forestry sector is the application of state-of-the-art harvesting and extraction techniques, so-called best suitable harvesting methods. We present a case study from Switzerland, where a lack of competitiveness in the forestry sector is of particular interest, with the aim of quantifying the efficiency gains if estimated best suitable harvesting methods were to be rigorously applied instead of the currently applied harvesting methods. For this purpose, we developed a spatial decision support system to allocate estimated best suitable harvesting methods to plots, while concurrently considering hauling route limitations, extraction route properties and stand characteristics. Our approach was based on productivity models and supported with expert-defined decision trees. The evaluation of the estimated best suitable harvesting methods and the comparison with the currently applied harvesting methods were completed for all 6500 National Forest Inventory (NFI) plots in Switzerland. We draw the following three major conclusions from our study: First, our modeling approach is an effective method to allocate estimated best suitable harvesting methods to NFI plots. Second, applying estimated best suitable harvesting methods would lead to cost reductions, in particular in the regions that include steep terrain and where harvesting mainly relies on cable- and air based extraction methods. Third, assuming an average timber price of 75 CHF m ^-3, 64 % instead of 52 % of the forest area could be harvested economically over the whole country if estimated best suitable methods were applied. This advantage would mainly be caused by a shift towards more mechanized harvesting methods. Improving the cost-effectiveness of the forestry sector is of high global relevance, as the increased use of domestic timber resources is a cost-efficient way to reduce atmospheric carbon emissions. The methodological framework described here was developed for Switzerland in particular, but it could be applied to Central Europe and other parts of Europe with a large amount of mountain forests.

Eine zeitgemässe Erschliessung mit Waldstrassen ist wichtig für die effiziente Bewirtschaftung des Waldes. Idealerweise sind die Strassen mit 5-Achs-Lastwagen (40 t maximales Gesamtgewicht) befahrbar; häufig ist der Einsatz von solchen Lastwagen aber nicht möglich, zum Beispiel wegen zu kleinen Kurvenradien oder nicht ausreichend tragfähigen Brücken. Um die Erschliessungssituation in der Schweiz flächendeckend beurteilen zu können, wurde der gesamte Schweizer Wald mit einer einheitlichen Methodik (Bont et al. 2018) untersucht. Das Modell erlaubt es, das Holzrücken vom Bestand zur Strasse und den Abtransport auf der Strasse kombiniert zu betrachten. Als Resultat der Analyse stehen zwei schweizweite Karten zur Verfügung: eine Karte der am besten geeigneten Rückemethode und eine generelle Klassierung der Erschliessungsgüte.

Damit der Wald Ökosystemleistungen erbringen kann, sind waldbauliche Lenkungsmassnahmen erforderlich. Für die effiziente Durchführung dieser Lenkungsmassnahmen ist eine gute Erschliessung mit Waldstrassen nötig. In diesem Artikel werden drei neue Produkte des Schweizerischen Landesforstinventars (LFI) vorgestellt, die dazu beitragen, die Holzernte effizienter auszugestalten und die Walderschliessung zu optimieren. Beim ersten Produkt handelt es sich um ein Modell zur Herleitung des wirtschaftlich günstigsten Holzernteverfahrens auf jeder LFI-Probefläche. Dazu wurden räumliche Daten zur Topografie und zum Waldstrassennetz, Bestandesdaten und Informationen zu den auf den LFI-Probeflächen eingesetzten Holzernteverfahren sowie expertenbasierte Entscheidungsbäume verwendet. Die Resultate zeigen, dass unter Anwendung des wirtschaftlich besten Verfahrens allgemein höher mechanisierte Verfahren eingesetzt würden und somit Kosten eingespart werden könnten. Das zweite Produkt beinhaltet eine einheitliche und flächendeckende Beurteilung der Erschliessungsgüte. Dabei wurden unter anderem die Topografie, die Bodeneigenschaften, das Waldstrassennetz und die Hindernisse für die Holzernte berücksichtigt. Die Beurteilung ergab, dass sich die Erschliessung auf rund der Hälfte der Schweizer Waldfläche gut für eine effiziente Waldbewirtschaftung eignet, auf je einem Viertel aber nur bedingt oder gar nicht. Für das dritte Produkt wurde unter Berücksichtigung von Strassen- und Rückekosten die optimale Strassendichte ermittelt. Im Vergleich mit der aktuellen Strassendichte kann nun für grössere Gebiete ein Überblick über die ökonomische Effizienz von Walderschliessungen gewonnen werden. Die drei Produkte schaffen Grundlagen für eine detaillierte und flächendeckende Beurteilung der Erschliessungssituation und der Holzerntesysteme im Schweizer Wald und kamen auch schon in der kantonalen Waldplanung von Bern und Graubünden zur Anwendung.

Le 4e Inventaire forestier national contient les relevés relatifs à la portance et à la géométrie des routes forestières. Ces données révèlent que seule une moitié environ de la surface forestière peut être exploitée avec des moyens techniques modernes.

Dank der Erhebung der Tragfähigkeit und der Geometrie der Waldstrassen im vierten Landesforstinventar kann die Güte der Walderschliessung seit Kurzem flächig beurteilt werden. Nur auf etwa 50% der Schweizer Waldfläche erlaubt die Erschliessung eine Waldbewirtschaftung nach dem heutigen Stand der Technik.

Aim: Red wood ants (Formica rufa group) mitigate invertebrate pest outbreaks, alter invertebrate communities, and contribute to nutrient cycling. The IUCN lists these insects as near threatened. We investigated whether disturbances of Red Wood Ant (RWA) forest habitats related to recreation, infrastructure, and forest management were associated with RWA occurrence. We also investigated the habitat associations of this group.
Location: Switzerland.
Methods: We trained random forest models to predict RWA occurrence using data from 6,341 plots distributed throughout Swiss forests. Our explanatory variables included descriptions of vegetation, terrain, climate and human disturbance of the forest. A model trained using all of these variables (Model 1) was compared to another trained using all of these variables except those describing human disturbance (Model 2). We compared the abilities of these models to differentiate between RWA presences and absences using areas under receiver operator curves (AUC). The nature of the associations between the probability of RWA occurrence predicted by Model 1 and the explanatory variables that made the greatest contributions to the AUC of this model were investigated using individual conditional expectation plots.
Results: No significant difference in AUC was detected between Models 1 and 2. RWA occurrence was positively associated with elevation, conifers, canopy gaps, ground cover vegetation and solar insolation while negatively associated with air temperature and a soil wetness index.
Main conclusions: The distribution of RWA within Swiss forests appeared unassociated with the human disturbances we investigated. To conserve RWA in Switzerland, we recommend the conservation of forests with high proportions of conifers, particularly those at high elevations. We also recommend forest management that promotes ground cover vegetation and open canopy structures. The negative associations between RWA occurrence and temperatures raise concerns for the prospects of RWA in the context of predicted climate warming.

Efficient forest management, and wood production in particular, requires a forest road network of appropriate density and bearing capacity. The road network affects the choice of a suitable extraction method and the length of the transport route from the forest, while the road standard defines the truck type that can be used.
We evaluate the forest road network's economic suitability for harvesting operations in the entire Swiss forest, an area of about 13,000 km² covering a range of topographies, based on the Swiss National Forest Inventory's (NFI) forest road dataset. This dataset is based on information from an interview survey with the local forest services and includes all forest roads in Switzerland capable of carrying trucks. Extraction options and hauling routes are analysed together; thus, the entire logging process is examined.
Model results include maps of the most suitable extraction method; extraction costs; hauling costs; and a suitability map based on a combination of the results. While the larger part of the Swiss forest is classified as "suitable" for economic harvesting operations, significant portions also fall into the "limited suitability" and "not suitable" categories. Our analysis provides an objective, country-wide, spatially explicit assessment of timber accessibility. The resulting suitability map helps identify areas where timber harvesting is economic using the current forest road network, and where it is not. The model results can be used in road network planning and management, for example, by comparing road-network re-design scenarios, and compared to the spatial distribution of available wood volume.

Das Landesforstinventar (LFI) ist eine periodische Erhebung des Bundes über den Zustand und die Entwicklung des Schweizer Waldes. Im vorliegenden Kapitel werden die Geschichte und die Ziele sowie die Methoden der Datenerhebung und -analyse des LFI vorgestellt, soweit sie für das Verständnis und die Interpretation der im Bericht dargestellten Ergebnisse notwendig sind.

L'inventaire forestier national (IFN) est un relevé périodique de l'état et du développement de la forêt suisse conduit par la Confédération. Ce chapitre présente l'historique et les objectifs de l'inventaire ainsi que les méthodes de collecte et d'analyse des données pour faciliter la compréhension des résultats contenus dans ce rapport.

In the Swiss National Forest Inventory (NFI), data on about 6400 sample plots is collected directly in the field, but not all information of interest can be assessed in this way. During NFI1, an interview survey was therefore designed to complement the terrestrial inventory. All local Swiss foresters (about 800) responsible for the forest districts and representatives of the forest authorities (forest service) in Switzerland were interviewed. The interviews were conducted twice in NFI4: the first for the first five NFI annual panels and the second for the remaining four annual panels (Sect. 8.3). This procedure resulted in one interview for each sample plot for every NFI cycle. The interview survey consists of two main parts: interviews to obtain information about the assessed sample plots, conducted twice during NFI4, followed by interviews conducted only once about forest roads throughout the entire country (independent of the sample plots). The interviews in NFI4 covered about 50 different attributes.
 

A high-quality data set for forest truck roads is an important prerequisite for road infrastructure management and transport route selection, as well as for the analysis of the ecological impact and recreational use of these roads. To support management decisions, the data set needs to fulfil various quality requirements, such as accuracy, relevance (fitness for use), consistency and completeness. In this section, we introduce the steps necessary to produce a reliable forest road data set, following a clearly defined procedure to ensure reproducibility, as well as consistency for the entire country and between inventory cycles. Furthermore, we point out potential error sources and how the Swiss National Forest Inventory (NFI) tries to avoid them, choosing appropriate measures for error prevention as well as error detection and adjustment of methods.
 

Support for open science is a highly relevant user requirement for the environmental data portal EnviDat. EnviDat, the institutional data portal and publication data repository of the Swiss Federal Research Institute WSL, actively implements the FAIR (Findability, Accessibility, Interoperability and Reusability) principles and provides a range of services in the area of research data management. Open science, with its requirements for improved knowledge sharing and reproducibility, is driving the adoption of free and open source software for geospatial (FOSS4G) in academic research. Open source software can play a key role in the proper documentation of data sets, processes and methodologies, because it supports the transparency of methods and the precise documentation of all steps needed to achieve the published results. EnviDat actively supports these activities to enhance its support for open science. With EnviDat, WSL contributes to the ongoing cultural evolution in research towards open science and opportunities for distant collaboration.

Despite relatively high road density in the forests of Switzerland, a large percentage of that road network does not fulfill best practice requirements. Before upgrading or rebuilding the road network, harvesting planners must first determine which areas have insufficient access. Traditional assessment methods tend to only report specific values such as road density. However, those values do not identify the exact parcels or areas that are inaccessible. Here, we present a model that assesses the economic suitability of each timbered parcel for wood-harvesting operations, including tree-felling and processing, and off- and on-road transport (hauling), based on the existing road network. The entire wood supply chain from forest (standing trees) to a virtual pile at the border of the planning unit was captured. This method was particularly designed for steep terrain and was tested in the Canton of Grisons in Switzerland. Compared with classical approaches, such as the road density concept, which only deliver average values, this new method enables planners to assess the development of a road network in a spatially explicit manner and to easily identify the reason and the location of shortcomings in the road network. Moreover, while other related spatially explicit approaches focus only on harvesting operations, the assessment method proposed here also includes limitations (road standards) of the road network.

Spatial information on soils and their abilities to fulfil their functions is key to sustainable soil resource use. Maps indicating how soils fulfil their functions, e.g., regulating nutrient and water flows, providing appropriate habitats, and supporting biomass production, have allowed soil information to be embedded in spatial planning programmes. We adapted 10 static soil function assessment (SFA) methods and applied them to agricultural soils in a study area on the Swiss Plateau. Soil function maps were created by applying the SFA methods to maps of eight basic soil properties generated previously using digital soil mapping techniques. The soil function maps were compared with results obtained by applying the SFA methods to data for N7000 soil profiles to determine how reasonable the maps were. Soil in the study area had distinctive spatial patterns for most of the regulation, habitat, and production functions, clearly indicating the multiple roles played by soil in supporting ecosystemservices. The fulfilment of individual soil functions is linked to the inherent soil properties, the terrain, and climatic conditions. The soil function maps agreed well with the SFA results for the profiles in terms of land use, soil type, and drainage class. Four aggregation ruleswere tested to give total assessment values (soil indices). Aggregating the 10 soil functions into an overall soil functionality value gave quite diverse spatial patterns, indicating that merging might average out the spatial characteristics of certain soil functions. We conclude that a quite comprehensive set of soil functions can be assessed using spatial information for eight basic soil properties to a soil depth of at least 1mand approved pedotransfer functions for secondary soil properties. SFA methods for the production function are well established, but methods for assessing habitat and regulation functions need to be developed further. This is also true for forest soils, for which SFA methods are yet to be established.

EnviDat is the institutional research data portal of the Swiss Federal Institute for Forest, Snow and Landscape WSL. The portal is designed to provide solutions for efficient, unified and managed access to the WSL’s comprehensive reservoir of monitoring and research data, in accordance with the WSL data policy. Through EnviDat, WSL is fostering open science, making curated, quality-controlled, publication-ready research data accessible. Data producers can document author contributions for a particular data set through the EnviDat-DataCRediT taxonomy. The publication of research data sets can be complemented with additional digital resources, such as, e.g., supplementary documentation, processing software or detailed descriptions of code (i.e. as Jupyter Notebooks). The EnviDat Team is working towards generic solutions for enhancing open science, in line with WSL’s commitment to accessible research data.

High-resolution maps of soil properties are a prerequisite for assessing soil threats and soil functions and for fostering the sustainable use of soil resources. For many regions in the world, accurate maps of soil properties are missing, but often sparsely sampled (legacy) soil data are available. Soil property data (response) can then be related by digital soil mapping (DSM) to spatially exhaustive environmental data that describe soil-forming factors (covariates) to create spatially continuous maps. With airborne and space-borne remote sensing and multi-scale terrain analysis, large sets of covariates have become common. Building parsimonious models amenable to pedological interpretation is then a challenging task.
We propose a new boosted geoadditive modelling framework (geoGAM) for DSM. The geoGAM models smooth non-linear relations between responses and single covariates and combines these model terms additively. Residual spatial autocorrelation is captured by a smooth function of spatial coordinates, and non-stationary effects are included through interactions between covariates and smooth spatial functions. The core of fully automated model building for geoGAM is component-wise gradient boosting.
We illustrate the application of the geoGAM framework by using soil data from the Canton of Zurich, Switzerland. We modelled effective cation exchange capacity (ECEC) in forest topsoils as a continuous response. For agricultural land we predicted the presence of waterlogged horizons in given soil depths as binary and drainage classes as ordinal responses. For the latter we used proportional odds geoGAM, taking the ordering of the response properly into account. Fitted geoGAM contained only a few covariates (7 to 17) selected from large sets (333 covariates for forests, 498 for agricultural land). Model sparsity allowed for covariate interpretation through partial effects plots. Prediction intervals were computed by model-based bootstrapping for ECEC. The predictive performance of the fitted geoGAM, tested with independent validation data and specific skill scores for continuous, binary and ordinal responses, compared well with other studies that modelled similar soil properties. Skill score (SS) values of 0.23 to 0.53 (with SS = 1 for perfect predictions and SS = 0 for zero explained variance) were achieved depending on the response and type of score. GeoGAM combines efficient model building from large sets of covariates with effects that are easy to interpret and therefore likely raises the acceptance of DSM products by end-users.

Mound-building red wood ants (Formica rufa group) fulfill keystone roles in forest ecosystems, and several species are on the red list of the International Union for Conservation of Nature. Nonetheless, detailed information on their distribution and habitat requirements is lacking, yet needed to evaluate population changes and develop conservation strategies.
To assess their status in Switzerland, we studied red wood ant mounds in a nationwide, systematic survey of forests (Swiss National Forest Inventory). We identified key predictors of mound occurrence and mound size related to forest structure, forest composition, climate, and topography.
Red wood ants were found to be relatively rare across Switzerland (1.4 mounds per ha of forest), especially at lower elevations (0.16 mounds per ha). Formica lugubris and F. paralugubris were common only in mountainous areas. Few F. rufa and F. polyctena mounds were found countrywide, the latter mostly at lower elevations. Formica aquilonia was restricted to the Engadine region of the Alps. Wood ants mainly depended on slope aspect, climate, forest structure, and conifer abundance, but did not depend on forest fragment size, distance to forest edges, or woody vegetation diversity.
Our baseline data will enable population changes of red wood ants to be quantified, to reassess their conservation and protection status. For now, based on their observed rarity, conservation measures for red wood ants seem advisable in Switzerland. Our data suggest that red wood ants are not restricted to large, continuous, or diverse forests. Conservation strategies could thus focus on optimizing the structure of coniferous forests.

Information on forest accessibility is important for forest management. For example, it helps to determine the potential wood supply and identify areas difficult to access. In 2013–2014, a survey was conducted in Switzerland to update the Forest Access Roads geo-dataset within the framework of the Swiss National Forest Inventory (NFI). The resulting nationwide dataset contains valuable information on truck-accessible forest roads that can be used to transport wood. The survey involved interviewing staff from the approximately 800 local forest services in Switzerland and recording the data first on paper maps and then in digitized form. The data in the NFI on the forest roads could thus be updated and additional information regarding their trafficability for specific categories of truck included. The information has now been attached to the geometries of the Roads and Tracks of the swissTLM^3D (release 2012) of the Federal Office of Topography swisstopo. The resulting data are suitable for statistical analyses and modeling, but further (labour-intensive) validation work would be necessary if they are to be used as a basis for applications requiring more spatial accuracy, such as navigation systems. The data are managed at the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) and are available for third parties for non-commercial use provided they have purchased a TLM license. In this article, the dataset, as well as its acquisition and potential uses, are described.