Identifying Conservation and Restoration Priorities for Saproxylic and Old-Growth Forest Species: A Case Study in Switzerland

Saproxylic (dead-wood-associated) and old-growth species are among the most threatened species in European forest ecosystems, as they are susceptible to intensive forest management. Identifying areas with particular relevant features of biodiversity is of prime concern when developing species conservation and habitat restoration strategies and in optimizing resource investments. We present an approach to identify regional conservation and restoration priorities even if knowledge on species distribution is weak, such as for saproxylic and old-growth species in Switzerland. Habitat suitability maps were modeled for an expert-based selection of 55 focal species, using an ecological niche factor analyses (ENFA). All the maps were then overlaid, in order to identify potential species' hotspots for different species groups of the 55 focal species (e.g., birds, fungi, red-listed species). We found that hotspots for various species groups did not correspond. Our results indicate that an approach based on "richness hotspots” may fail to conserve specific species groups. We hence recommend defining a biodiversity conservation strategy prior to implementing conservation/restoration efforts in specific regions. The conservation priority setting of the five biogeographical regions in Switzerland, however, did not differ when different hotspot definitions were applied. This observation emphasizes that the chosen method is robust. Since the ENFA needs only presence data, this species prediction method seems to be useful for any situation where the species distribution is poorly known and/or absence data are lacking. In order to identify priorities for either conservation or restoration efforts, we recommend a method based on presence data only, because absence data may reflect factors unrelated to species presenc

Dead wood in managed forests: how much and how much is enough?:development of a snag-quantification method by remote sensing & GIS and snag targets based on Three-toed woodpeckers' habitat requirements

The aims of this research were twofold: to develop an efficient method for the quantification of large spruce snags (standing dying and dead trees), and to establish snag target values for sustainable forest management. We answer the two basic questions: how much dead wood is currently available in managed forests? And how much dead wood is enough for biodiversity conservation? It is widely accepted that modern forest management has to be sustainable. One generally recognised criterion of sustainability is the maintenance of biodiversity. Since this concept encompasses a large range of scales and features (landscapes, ecosystems, species and genes; components, processes, functions, etc.), biodiversity indicators have been identified for measurement and monitoring purposes. "Dead wood" has been recognised as a key indicator for biodiversity in forest ecosystems. Verifying and assessing progress towards biodiversity maintenance or restoration hence requires the measurement of different kinds of dead wood. Yet cost-efficient and rapid methods are still lacking. That is why we developed in this thesis an efficient method for the quantification of large spruce snags. Being based on infrared Aerial Photos and a Geographic Information System (GIS), it is called the AP-GIS-method. It enables mapping of snags and calculation of the spatial snag-density, i.e. the number of snags per hectare, and can be used to answer the question: How much dead wood is in managed forests? Beside techniques to assess dead-wood quantities, forest managers need quantitative target values, i.e. guidelines in order to know how much dead wood should be maintained in managed forests for biodiversity conservation. Natural forests may be used as reference systems to define such targets. However, since dead-wood amounts in natural forests may be extremely high, up to 30% of dead trunks, the retention of such amounts in managed forests would hardly be compatible with economic objectives. Another possibility for defining guidelines is the translation of the habitat requirements of deadwood- dependent species into management targets. The Three-toed woodpecker Picoides tridactylus has previously been recognised as a potential indicator species of features characteristic for forests with natural dynamics (especially old-growth). Although ecological studies had demonstrated its need of dying and dead trees for foraging, nesting and drumming, the required density of such trees has never been quantified. In this thesis, we analysed the dependence on dead wood for both European subspecies, the Alpine Picoides tridactylus alpinus and the northern P. tr. tridactylus. The study was conducted in sub-Alpine spruce forests in Switzerland and boreal forests in central Sweden. In both countries, we found a significant non-linear response of the probability of woodpecker presence to different amounts of dead trees, and identified critical ecological thresholds for the local presence of this species. Clearly, the Three-toed woodpecker depends on relatively high amounts of dying and dead trees. In Switzerland, the road network density negatively affected the presence of this woodpecker species, since a high road density facilitates forest management intensification and the removal of diseased and dead trees. Based on our results, and since several other links with biodiversity have previously been demonstrated, we suggest that Three-toed woodpeckers be considered indicators of dead wood and habitat quality. This species has therefore been used in this thesis to find an answer to the question: How much dead wood is enough in managed forests? In order to ascertain dead-tree targets, we developed a bioenergetic model for Threetoed woodpeckers, enabling estimation of snag amounts required by this species to satisfy its energy needs. By comparing modelling results with the previously identified critical dead-wood thresholds, we were able to derive reliable targets, since both approaches resulted in similar critical values. We recommend, for both boreal and sub-Alpine spruce forests, aiming for 5% of the standing tree basal area, or volume to be dead. Such snag-retention levels, to be applied over an area of about 100 ha, correspond in sub-Alpine forests to a basal area of ≥ 1.6 m2 ha-1, or a volume of ≥ 18 m3 ha-1, or a minimum of 14 snags with a diameter ≥ 21 cm per hectare. Considered as a pragmatic way to stimulate forest managers' interest in dead wood maintenance or restoration, we analysed the potential usefulness of Three-toed woodpeckers as natural agents against bark beetles. By defining three scenarios for different levels of woodpecker effectiveness, we compared the numbers of bark beetles consumed with those caught in pheromone traps used in forestry. We demonstrate that woodpeckers catch 2-19 times more bark beetles than traps do. This result is true for both cases, when one woodpecker is compared with one trap, and when the whole Swiss woodpecker population is compared to all traps installed in Swiss forests

Long-term dynamics of aboveground fungal communities in a subalpine Norway spruce forest under elevated nitrogen input

As anthropogenic N deposition has been suspected to be the main reason for the decline of macromycetous sporocarp production in forest ecosystems, various N-fertilization experiments were started in the mid 1990s. The dynamics of ectomycorrhizal (root-inhabiting) and terricolous saprobic (litter-inhabiting) fungal communities were studied by exhaustive sporocarp inventories in a substitution Norway spruce (Picea abies) forest in two 256-m2 plots sampled for periods of 1 week at 1-m2 resolution between 1994 and 2007. N was added to the soil twice per year in one plot from the fourth year onwards. The effects of N input and time on aboveground fungal communities were assessed using redundancy analysis, principal response curves and non-parametric multivariate ANOVA. Results of this long-term experiment revealed that both ectomycorrhizal and saprobic fungal communities responded to an increase in soil N input. The ectomycorrhizal community reacted by a fast decrease in sporocarp production and in species richness, whereas the saprobic community was less affected. The response was highly species specific, especially for the saprobic community. The difference in species composition between control and fertilized plots was significant after 1year of N addition for ectomycorrhizal fungi and only after 3years for saprobic fungi. An aging effect affected sporocarp production in the whole area. For both communities, this unidirectional drift in species composition was as important as the treatment effect. This result highlights the importance of considering the respective role of treatment and year effects in long-term field experiments on fungal communitie

Guide de poche des dendro-microhabitats : Description des différents types de microhabitats liés aux arbres et des principales espèces qui y sont associées

Le feuillage des arbres est bien connu pour offrir un abri aux oiseaux, écureuils et autres espèces aisément observables. Mais les arbres recèlent, sur le tronc et les branches, une foule d’autres structures, de taille souvent modeste, qui fournissent abri, nourriture ou lieu de reproduction à une grande diversité d’espèces parmi les animaux, les végétaux ou les champignons. Ces milieux de vie de petite taille portés par les arbres sont appelés «dendro-microhabitats» (fig. 1). Les dendro-microhabitats(en abrégé: «dmh») présentent, selon leur nature (arbre support vivant ou mort, localisation dans l’arbre, forme, degré de décomposition du bois,...), des conditions de vie très différentes les unes des autres. Chaque type de dmh abrite par conséquent des espèces bien spécifiques. Plus on compte de types de dmh dans un peuplement, plus on multiplie les milieux de vie et donc la capacité du peuplement à accueillir un grand nombre d’espèces. Comme les dmh sont des milieux de vie spatialement isolés et évolutifs, les espèces associées sont obligées de se déplacer à travers le peuplement pour trouver un dmh similaire, afin de réduire le parasitisme et le risque de prédation, de rencontrer d’autres individus pour se reproduire ou, bien sûr, pour remplacer le dmh disparu. Ainsi, la fréquence d’un même type de dmh est également très importante pour la survie des espèces associées à ce type. Pour conserver une grande diversité d’espèces en forêt et ainsi renforcer la résistance et la résilience du peuplement, il est donc très utile d’apprendre à reconnaître les dmh. Cela permet d’être à même de repérer les arbres-habitats à conserver lors du martelage ou d’estimer la capacité d’accueil potentielle du peuplement pour les espèces

Catalogue of tree microhabitats : Reference field list

The present catalogue is one of the outputs of the demonstration project ‘Establishing a European network of demonstration sites for the integration of biodiversity conservation into forest management ..

Katalog over mikrohabitater på traeer: Referenceliste til feltbrug

This Integrate+ Technical Paper (in Danish) is one of several translations of the original published in English language (Catalogue of tree microhabitats – Reference field list)