Biodiversity in Dead Wood Stokland, Jogeir N; Siitonen, Juha; Jonsson, Bengt Gunnar
04/2012
eBook, Book
Fossils document the existence of trees and wood-associated organisms from almost 400 million years ago, and today there are between 400,000 and 1 million wood-inhabiting species in the world. This ...is the first book to synthesise the natural history and conservation needs of wood-inhabiting organisms. Presenting a thorough introduction to biodiversity in decaying wood, the book studies the rich diversity of fungi, insects and vertebrates that depend upon dead wood. It describes the functional diversity of these organisms and their specific habitat requirements in terms of host trees, decay phases, tree dimensions, microhabitats and the surrounding environment. Recognising the threats posed by timber extraction and forest management, the authors also present management options for protecting and maintaining the diversity of these species in forests as well as in agricultural landscapes and urban parks.
► We modeled species distribution with alternative pseudo-absence observation sets. ► The ps-absence sampling design strongly influenced model predictive performance. ► The ps-absence sample size ...minimally influenced model predictive performance. ► One should allow ps-absence observations to overlap with presence observations.
We explored the effect of varying pseudo-absence data in species distribution modelling using empirical data for four real species and simulated data for two imaginary species. In all analyses we used a fixed study area, a fixed set of environmental predictors and a fixed set of presence observations. Next, we added pseudo-absence data generated by different sampling designs and in different numbers to assess their relative importance for the output from the species distribution model. The sampling design strongly influenced the predictive performance of the models while the number of pseudo-absences had minimal effect on the predictive performance. We attribute much of these results to the relationship between the environmental range of the pseudo-absences (i.e. the extent of the environmental space being considered) and the environmental range of the presence observations (i.e. under which environmental conditions the species occurs). The number of generated pseudo-absences had a direct effect on the predicted probability, which translated to different distribution areas. Pseudo-absence observations that fell within grid cells with presence observations were purposely included in our analyses. We discourage the practice of excluding certain pseudo-absence data because it involves arbitrary assumptions about what are (un)suitable environments for the species being modelled.
This study documents volume increment and natural mortality in 1379 old boreal forests plots during four consecutive inventory cycles in the Norwegian national forest inventory. The stands age up to ...100 years beyond recommended rotation length (close to economical optimal rotation length) and comprise a wide range of site productivity classes in both pine- and spruce-dominated forests.
The annual gross volume increment was stable and nearly constant up to 50–100 years beyond economically optimal rotation length. In parallel, there was very low natural mortality (0.22–0.66% of standing volume) with minimal risk of stand collapse. Stands with satisfactory stocking had volume increment equal to or higher than the reference volume increment in managed stands harvested at recommended rotation length, while poorly stocked stands had inferior volume increment.
From a climate change mitigation perspective, it seems to be a good strategy to extend the rotation length beyond what is currently recommended, provided that the stands have satisfactory stocking.
► We documented fungi on dead wood in natural and managed boreal forests in SE Norway. ► The species number was 10–55% lower in managed forests compared to natural spruce forest. ► No significant ...difference was found between managed and natural pine forests. ► Substrate specialists declined significantly, but not generalists and common species. ► A continuous supply of dead wood is more important in spruce forests than in pine forests.
The species composition of wood-inhabiting fungi (polypores and corticoids) was investigated on 1138 spruce logs and 992 pine logs in 90 managed and 34 natural or near-natural spruce and pine forests in SE Norway.
Altogether, the study included 290 species of wood-inhabiting fungi. Comparisons of logs with similar properties (standardized tree species, decay class, dimension class) in natural and managed forests showed a significant reduction in species number per log in managed spruce forests, but not in managed pine forests. The species number per log in managed spruce forests was 10–55% lower than on logs from natural spruce forests. The reduction was strongest on logs of large dimensions. A comparison of 200–400 spruce logs from natural and managed forests showed a 25% reduction in species richness corresponding to a conservative loss of ca. 40 species on a regional scale.
A closer inspection revealed that species confined to medium and very decayed spruce logs were disfavored in managed forests, whereas species on early decay classes and decay generalists were unaffected. Similarly, species preferring large spruce logs were disfavored in managed forests. Forest management had strongest impact on low-frequent species in the spruce forests (more than 50% reduction), whereas common species were modestly affected. Corticoid fungi were more adversely affected than polypore fungi.
These results indicate that wood-decaying fungi in pine forests are more adapted to forest disturbances than spruce-associated species. Management measures securing a continuous supply of dead wood are more important in spruce forests than in pine forests.
•The original paper fills a knowledge gap of volume increment in old forests using exploratory empirical analysis.•The non-declining volume increment is not masked by unbalanced stand densities ...across stand age.•Experimental data from even-aged forests are needed to test alternative hypotheses about volume increment in old forests.
This reply clarifies an ambiguity concerning stand structure and representativeness of the results concerning even-aged and uneven-aged boreal forests. The key finding of non-declining volume increment with increasing age in old forest appears to be robust against the critique from Brunner (2021). Two alternative hypotheses concerning volume increment in forest older than standard rotation age are formally proposed.
The woodland key habitat (WKH) concept has become an essential instrument in biodiversity-orientated forest management in northern Europe. The philosophy behind the concept is basically the same in ...all of the countries: to conserve the biodiversity of production landscapes by preserving small habitat patches that are supposed to be particularly valuable. This article reviews the definitions, inventories and implementation processes of WKHs in Sweden, Finland, Norway, Latvia, Estonia and Lithuania. Sweden and the Baltic countries have similar WKH models, while the models in Finland and Norway are clearly deviating. Depending on the country, the definitions emphasize different factors, such as soil and bedrock properties, stand structure and occurrence of indicator species. The mean size of the WKHs varies considerably, from 0.7 ha (Finland) to 4.6 ha (Sweden). The degree of formal protection also differs. Preservation of WKHs is primarily based on forest legislation in Finland, Estonia and Latvia, and on forest certification in the other countries. The implementation of the WKH concept is inconsistent between the countries, resulting in different sets of habitats being included in the WKH networks. This makes direct comparisons between the countries difficult, and may hamper the generalization of research results into other areas.
Deadwood can represent a substantial portion of forest ecosystem carbon stocks and is often reported following good practice guidance associated with national greenhouse gas inventories. In ...high-latitude forest ecosystems, a substantial proportion of downed deadwood is overgrown by ground vegetation and buried in the humus layer. Such burial obfuscates the important process of deadwood carbon transfer to other pools (e.g., litter and soil) and emission to the atmosphere (i.e., rates of decay). Using data from the Swedish National Forest Inventory, we found that the proportion of downed logs that is buried increased from temperate to boreal forests. Several factors affect the probability of burial, including log attributes (e.g., decay class), ground vegetation (e.g., moss dominance, type of moss cover), and edaphic conditions (e.g., soil type, depth of organic layer). Combined assessments suggest that about 24% of the carbon in the aboveground downed deadwood pool was found to be buried in boreal forests. Deadwood burial has important implications for forest carbon dynamics and associated monitoring (e.g., United Nations Framework Convention on Climate Change reporting) as such a pool typically decomposes much slower compared with aboveground deadwood.
Replacement cost refers to the loss incurred if the ideal set of conservation areas cannot be protected due to compulsory inclusion or exclusion of some area candidates. This cost can be defined ...either in terms of loss of conservation value or in terms of extra acquisition cost, and it has a clear mathematical definition as a difference between the value of the unconstrained optimal solution and a constrained suboptimal solution. In this work we for the first time show how replacement cost can be calculated in the context of sequential reserve selection, where a reserve network is developed over a longer time period and ongoing habitat loss influences retention and availability of sites. In case of site exclusion, a question that can be asked is, “if a site belonging to the ideal (optimal) solution cannot be obtained, what expected loss in reserve network value does this entail by the end of the planning period given that the rest of the solution is re-organized in the most advantageous manner?” Heuristically, the proposed method achieves the ambit of combining irreplaceability and vulnerability into one score of site importance. We applied replacement cost analysis to conservation prioritization for wood-inhabiting fungi in Norway, identifying factors that influence replacement cost and urgency of site acquisition. Among other things we find that the reliability of loss rate information is important, because the optimal site acquisition order may be strongly influenced by underestimated loss rates.
Abstract Species distribution modeling (SDM) can be useful for many applied purposes, e.g., mapping and monitoring of rare and endangered species. Sparse presence data are a recurrent, major obstacle ...to precise modeling of species distributions. Thus, knowing the minimum number of presences required to obtain reliable distribution models is of fundamental importance for applied use of SDM. This study uses a novel approach to assess the critical sample size (CSS) sufficient for an accurate prediction of species distributions with Maximum Entropy Modeling (MaxEnt). Large presence datasets for thirty insect species, ranging from generalists to specialists regarding their responses to main bioclimatic gradients, were used to produce reference distribution models. Models based on replicated subsamples of different size drawn randomly from the full dataset were compared to the reference model using the index of vector similarity distribution models. Models based on replicated subsamples of different size drawn randomly from the full dataset were compared to the reference model using the index of vector similarity ( IVS ). Two thresholds for IVS were determined based on comparison of nine reference models to random null models. The threshold values correspond to 0.95 and 0.99 probability that a model outperforms a random null model in terms of similarity to the reference dataset. For 90% of the species, clearly nonrandom models were obtained with less than 10 presence observations, and for 97% of the species with less than 15 presence observations. We conclude that the number of presence observations required to produce nonrandom models is generally low and, accordingly, that even sparse datasets may be useful for distribution modelling.
It is important that measures to maintain biodiversity are taken in a way that is cost-effective for the landowner. We analyzed the cost-effectiveness of silvicultural measures that aim at increasing ...the substrate availability for red-listed (species that are threatened, near threatened or where species probably are threatened but data is deficient) saproxylic (wood-inhabiting) organisms. We modelled stands of Norway spruce (
Picea abies) in three regions of Sweden by using computer simulations and a database with substrate requirements of saproxylic beetles and cryptogams on the Swedish Red-List. Conclusions concerning cost-effectiveness of silvicultural measures depend on the extinction thresholds of the species they are intended to conserve; measures that generate only small amounts of coarse woody debris (CWD) may provide too little substrate to be useful for species with high extinction thresholds. In northern Sweden, forestland is relatively inexpensive, so a cost-effective strategy to increase the amount of spruce CWD was to set aside more forests as reserves. In central and southern Sweden, more emphasis should instead be given to increasing the amount of CWD in the managed forest. The regulations by the Forest Stewardship Council (FSC) could be made more cost-effective by prescribing creation of more high stumps and retention of larger amounts of naturally dying trees. Large-sized CWD, CWD from slow-growing trees, and CWD in late decay stages are substrate types that were particularly rare in managed forest in relation to unmanaged forests. Manual soil scarification and retention of living trees are measures that can increase the proportion of these underrepresented CWD types.
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