Reconnaître les arbres-habitats grâce à l’application habitat.sylvotheque.ch Découvrir, rechercher et identifier les dendromicrohabitats portés par les arbres grâce à des photos à 360° prises en forêt: habitat.sylvotheque.ch est une plateforme informatique, disponible en français, en allemand et en anglais, pour apprendre à reconnaître les dendromicrohabitats, petits milieux de vie portés par les arbres et qui sont indispensables à des milliers d’organismes spécialisés. A l’aide de nombreux contenus multimédias sous forme d’images, de vidéos et de textes, l’utilisateur est mis au défi par quatre modes d’apprentissage interactifs à difficulté croissante. Le site, riche en informations, s’adresse autant au débutant qu’au fin connaisseur des arbres-habitats.

Marteloscopes as training tools for the retention and conservation of habitat trees in forests Recently several initiatives on the political and practical level have aimed at promoting forest biodiversity and at halting the loss of species in forest ecosystems. Nevertheless numerous species are still threatened. The main reason for this phenomenon is most likely the fact that habitat trees – i.e. trees providing microhabitats for various different species – are rare in managed forests. In the course of the projects Integrate and Integrate+ (carried out at the European Forest Institute between 2011 and 2017) we looked for methods on how to retain habitat trees within the scope of integrative forest management. It became more and more apparent that most foresters very successfully recognize economically valuable trees, but not habitat trees. For that reason we categorized habitat structures occurring on trees and developed a microhabitat catalogue to determine habitat values. Additionally we used marteloscopes as training tools for the retention of habitat trees within integrative forest management. Altogether we established 40 such marteloscopes with a biodiversity focus across Europe. Three of these are located in Switzerland. Using a mobile app on a tablet computer we analyzed effects of different tree selections with respect to habitat and economic value of a stand. Furthermore the marteloscopes are ideal tools to convince decision makers or conservationists that harvesting trees and promoting biodiversity can be achieved in the very same stand.

The search for old-growth forests in Switzerland Old-growth forests and stands have multiple values, such as biological, scientific, socioeconomic, aesthetic, spiritual and cultural ones, but they are very rare in central Europe. Currently, an overview about the existence and size of old-growth forest patches in Switzerland is missing. We propose a definition for old-growth forests worth preserving based on ten criteria: 1) presence of veteran trees, 2) significant biomass, 3) heterogeneous stand structure including senescent and decaying stages, 4) presence of natural processes and disturbances, 5) high dead wood volume (at least 30 m3/ha) and a large diversity of dimensions and decay stages of dead wood pieces, 6) autochthonous tree species, 7) diverse and natural species assemblages, 8) only extensive or no harvesting for the last 50 years, 9) long continuity of forest cover, 10) minimal area of 30 ha for old-growth forests and 1 ha for old-growth stands. When searching for old-growth forests and stands worth preserving, quantitative criteria from the National Forest Inventory and other sources should also be used. We call on all forest specialists to identify old-growth patches, to inform the population and decision makers about their high value, and to protect them in an adequate manner as a unique natural heritage.

How large should old-growth islands be? About 5% of the Swiss forest surface should be protected as natural forest reserves or as old-growth islands until 2030. This goal, which has been formulated by the Federal Office for the Environment and by the cantons, aims to promote the natural development of the forest and to conserve saproxylic species. Beside large-sized natural forest reserves, smaller old-growth islands may also play an important role. A bootstrapping method has been developed to define the minimal size of old-growth islands based on a field inventory in high forests without logging since at least 30 years. Three different indicators for habitat structures have been used to establish the ecological potential of old-growth islands: the total number of habitat structures, the amount of deadwood and the number of woodpecker trees. The threshold has been defined as the average of each indicator minus the standard error for different forest types. The surface of an island is determined at the point where 75% of the modeled surfaces are above the threshold, which guarantees a certain ecological potential. This surface reaches 0.7 ha for floodplain forests, 0.9 ha for beech and fir-beech forests and 1.2 ha for silver spruce-fir forests. The computed values are minimal rather than optimal surfaces for old-growth islands. With an increase of the surface, sustainability, quantity and quality of the habitats will be improved. Therefore, the size of old-growth islands should be larger whenever the local circumstances are favorable.

Identifying habitat hotspots for saproxylic species using NFI data Old wood and deadwood are the most important habitat features for thousands of typical wood-dwelling animal, fungi and plant species. In this paper, we explore the question of whether Swiss National Forest Inventory (NFI) data can be used to identify so-called habitat hotspots in order to promote species nationally and regionally. We therefore used NFI data to analyse old wood, deadwood and habitat trees, which are the three most important habitat indicators for old and deadwood specialists, and developed a structural index based on all three. The results show that national distribution maps of selected saproxylic species differ in how well they correspond with NFI habitat indicators, most probably because field observations are not representative. The indicators were therefore compared with modelled distribution areas of potential hotspots for saproxylic species. It seems that today deadwood in particular is seldom very frequent in those areas where it would most help to maintain biodiversity. Deadwood is especially plentiful in the western edges of the Alps. There are large supplies of old wood in Valais and the Engadine, and hotspots of habitat trees in Ticino, the central Jura and lower Valais. The NFI data on site characteristics, management forms and main forest functions were analysed to find out how much influence these factors have. For example, spruce-silver fir forests contain twice as much deadwood as beech forests (32 vs. 16 m 3 /ha), and old stands in spruce-silver fir forests untended for over 30 years as much as 50 m 3 /ha. Deadwood supplies tend to be greater at higher altitudes, on steep slopes and in forests difficult to access, regardless of the forest function. Protection forests tend to contain the most old stands (27% older than 120 years) and deadwood (26 m 3 /ha), while forests mainly used for recreation and timber production contain 12–13 m 3 /ha of deadwood and 17–20% of old stands. During the past two decades, the amount of old wood and deadwood has greatly increased in forests regardless of their function. The NFI inventories are very suitable for monitoring changes in forest habitats across space and time, and for assessing the influence of site characteristics, forms of management and natural events. Detailed analyses of NFI data can help in deciding on the best nature conservation strategies, for example, the geographical focus for conservation or promotion, the potential of forests that have not been used for a long time or the synergy with protection forests. NFI data should be used more for such purposes in future.

Habitat trees are important elements to maintain forest biodiversity. An effective way to provide habitats for species depending on old growth structures may be the conservation of a certain number of habitat trees integrated in managed forests. It has been suggested to maintain at least five such habitat trees per hectare for this purpose. In order to evaluate the number of existing potential trees as well as the financial consequences for the forest owner, we sampled all trees greater than 40 centimetres at breast height on sample plots of the forest inventory in the forest of Baden, Switzerland. Based on a catalogue of important traits of old trees which are important for the survival of five groups of organisms (insects, birds, bats, lichen, fungi), we assessed the ecological value of all trees. We also estimated their economic value in terms of net wood value for each tree. Results show that the conservation of five currently existing habitat trees per hectare would cause significant financial losses for the owner, amounting to 850 Swiss francs per hectare or 170 francs per tree in our example. Moreover, ecological values of many of these trees would be rather low because there are not enough suitable trees to select from. Ecologically valuable trees most likely were removed during tending of stands. Instead of general demands like for example five trees per hectare it seems more effective to concentrate on the currently existing ecologically valuable trees only. Financial losses may need to be covered by public funding in cases where they are high. Moreover, management of habitat trees needs to be planned on a long-term basis. Conservation and promotion of a certain number of habitat trees need to be integrated in tending concepts from early developmental stages.

Veteran trees and deadwood are key elements to maintain forest biodiversity. Setting aside protected forest areas and old-growth patches is a recent concept intended to favor deadwood dependent species. We compared forest areas where no harvesting occurred for at least 30 years with regularly managed forests, in order to assess the efficiency of such conservation measures. We collected data from 24 sites in Switzerland, where we inventoried dead trees and habitat structures such as cavities, cracks, bark pockets, etc. In unmanaged forests we found deadwood amounts of 98–143 m 3 and 20 snags > 30 cm DBH per hectare, one and half time more large trees (> 60 cm DBH) und twice as many habitat structures as in managed forests. The latter had in average 15–19 m 3 of deadwood and 3 snags > 30 cm DBH per hectare. Deadwood amounts in unmanaged forests were similar to the ones in natural forests of central Europe. However, we found 10–50 times less veteran trees (> 80 cm DBH) than in natural forests (1 vs. 0.2 trees per hectare in unmanaged vs. managed forests). For equal diameter classes, trees had more habitat structures in unmanaged than in managed forests. Forest managers plan to intensify wood harvesting in Swiss forests. Consequently, we recommend to urgently set aside protected forest areas and old-growth patches, to maintain and favor habitat trees in managed forests, and to introduce an efficient sustainable deadwood management in any forest.

One of the main aims of Swiss forestry policy is the conservation of species diversity. In some regions many saproxylic species are nevertheless endangered owing to a dearth of sufficient old and dead wood structures. Consequently, special measures are called for to promote such species. The paper describes various direct measures, for example, the creation of old-growth islands, preservation of habitat trees and the passive accumulation of dead wood, but also lists measures to improve framework conditions such as embedding the themes of old and dead wood and biodiversity in foundation and further training courses for foresters or improving information aimed at the population as a whole. In the second part we present some conflicts concerning the aims together with possible solution approaches. The paper concludes with a series of open questions surrounding the theme of old and dead wood.

The conservation of species diversity has become one of the priorities of Swiss forest policy. Conservation also includes a strategy of promoting saproxylic species. The occurrence of old and dead wood in Switzerland is mostly confined to the alpine regions, and – but only in insufficient quantities – in some areas of the Plateau. A modelling and accumulation of the habitat maps of 55 saproxylic species of various taxonomic groups(birds, mammals, amphibians, reptiles, molluscs, fungi and lichens)show that the greatest potential for promotion for such species exists above all in the Jura and on the Swiss Plateau. Regions where many of the so-called saproxylic hotspots occur and where simultaneous ecological deficits of old and dead wood exist should be the first places where measures are taken to promote old and dead wood dependant species.

Dead wood is of paramount importance for forest biodiversity. For this reason it was adopted as an indicator for sustainable forest management by the Ministerial Conference on the protection of forests in Europe. This paper aims to answer the question of how much dead wood is necessary for the maintenance of biodiversity in sub-alpine spruce forest ecosystems. For this purpose we studied the habitat preferences of the three-toed woodpecker, a bird species that depends heavily on dead trees. Previous ecological studies had already demonstrated that this woodpecker is an indicator of spruce forests with a high degree of naturalness and biodiversity. Our field study in Swiss sub-Alpine spruce and Swedish boreal forests showed that, below a threshold level of about 20 m 3 standing dead trees per ha, the probability of finding these woodpeckers drastically decreases. Similar results were obtained using a bioenergetic model, which calculated the energy requirements of this insectivorous woodpecker. Based on the results, our recommendation is to ensure a scattering of dead-wood rich areas in forest landscapes. Each area should cover about one square kilometre and have a mean of 5% of standing dead trees (≥ 18 m 3 ha –1 ), and a total of approx. 9% of dead wood(≥ 33 m 3 ha –1 standing and fallen).

The three-toed woodpecker (Picoides tridactylus) was first observed in the region of Pays-d'Enhaut ten years ago and is a great specialist of dead wood. This species is a suitable indicator for the quantitative and qualitative evaluation of ecological forest quality. The investigation results originating from five spruce mountain forests where the bird is present and three forests where it is assert are inventoried in the Pays-d'Enhaut region of Switzerland. The results suggest that the emergence of the woodpecker population could be due to under-management of the forest over the last forty years. The dead wood volumes in the forest with the woodpecker are similar to those of other unmanaged European forests. Forests situated above 1400 m above sea-level are recommended to be considered as ‹forest reserves›, whereas in managed forests up to an altitude of 1400 m, all trees with woodpecker's beakmarks and all snags with DBH over 30 cm should be left.