Forests provide humans with a range of valuable ecosystem services, but current forest management practices may increase susceptibility to damage from disturbances such as pest insects. One such practise is the harvesting of residue, which decreases the amount of dead wood in the forest. Dead wood has been shown to be of importance for biodiversity and could decrease vulnerability to biotic disturbances. Sustainable forest management and conservation of biological diversity is required to maintain ecologically healthy forests. I aimed to investigate if biodiversity connected to dead wood could contribute to insect pest mitigation. I sampled ground-dwelling arthropods with pitfall traps in monoculture pine stands in Central Sweden on plots where dead wood had been either added or removed. To relate catches from pitfall traps to predation pressure of pest insects, I used plasticine model larvae to measure the attack rate. Contrary to my expectations, total arthropod abundance was higher when dead wood had been removed. Furthermore, the presence of dead wood had no effect on total arthropod diversity and diversity and abundance of predators. There was no relationship between predator catches and attack rates on plasticine model larvae. My results contradict previous findings that dead wood promotes biodiversity and pest mitigation. This highlights the need for studies targeting the more specific effects of different types of dead wood, in different types of forest stands on specific taxonomic groups and ecological processes, as results do not appear to be uniform across studies.

The conversion of natural forests to production land uses has led to huge losses of biodiversity and continues to threaten remaining terrestrial flora and fauna throughout the world. The global demand for wood products and energy, which was partly responsible for the loss of primary native habitat, is now one of the leading drivers of afforestation with significant new areas of plantation replacing former agricultural lands. While plantations do not support the same biodiversity values as natural forests they do provide significant habitat for a range of species. Saproxylic invertebrates (species that are dependent on deadwood) are strongly affected by the temporal and spatial availability of different deadwood resources. Previous research on saproxylic invertebrates has largely been restricted to natural or managed natural forests predominantly in the Northern Hemisphere, where forest management practices have been modified to conserve these species This thesis fills a distinct research gap in New Zealand and is the first large scale study to quantify the effects of deadwood age, wood species, and landscape composition on saproxylic invertebrates in our plantation forests by direct rearing. In this thesis I show that thinning residues, which are currently retained in many plantation forests, provide significant habitat for a range of native invertebrate taxonomic groups, including diverse assemblages of Coleoptera and Hymenoptera. Deadwood age is an important attribute determining taxonomic richness of saproxylic invertebrates. Richness of invertebrate orders/classes and Coleoptera species all increased in older deadwood material, and a stepwise multidimensional analysis procedure indicated that the age of deadwood was the most important factor structuring saproxylic invertebrate community composition in Pinus radiata thinning residues. Deadwood age was a stronger predictor of community composition in thinning residue than measures of landscape composition, such as the proportion of remnant native forest cover. The change in saproxylic invertebrate composition that occurs with deadwood age was related to changes in the feeding guilds, with a transition from primary wood feeding species to predators/parasitoids and fungal feeders with increasing dead wood age. Because thinning’s are carried out at prescribed times throughout the stand rotation, stand age could be adopted as a proxy for deadwood age in these systems allowing forest managers a simple method for monitoring saproxylic beetle habitat availability . My research provides strong empirical evidence that supports the existing conservation paradigm that forest managers should seek to create a mosaic of habitats at the landscape scale to enhance biodiversity opportunities in plantations. In addition to the habitat opportunities provided by P. radiata deadwood that is derived from silvicultural practices there are several sources of native wood in plantations. Native woody resources are found in either the embedded remnant areas of native forest or in the understory of stands as many native woody species colonise this habitat. As yet the importance of native understory deadwood resources for saproxylic species is unknown. In addition it is unclear how the importance of such understory resources is influenced by proximity to remnant native forest patches. I used experimental wood billets of four tree species (3 native and the exotic P. radiata) placed along replicated transects spanning native habitat and adjacent early stage regenerating plantation stands to assess the saproxylic invertebrate assemblages associated with different deadwood species as a function of proximity to native forest. I found that an interaction between wood host specificity (local scale) and proximity to interior native forest (landscape scale) was the most important factor regulating saproxylic invertebrate community structure. Deadwood of the native subcanopy trees Schefflera digitata, Melicytus ramiflorus, Aristotelia serrata and the exotic conifer P. radiata provided habitat for different subsets of the saproxylic fauna. The most pronounced differences in saproxylic community structure were between the native sub-canopy broadleaf species and the exotic P. radiata. Surprisingly the P. radiata supported a greater species richness and abundance of saproxylic Coleoptera in native remnants than the native wood species in the same habitat. In general, species richness was higher in native forest habitats and declined with increasing distance from native habitat. These results suggest that both the diversity of deadwood resources that are available and their proximity to native remnants are important for maintaining saproxylic communities in plantations. However, two of the native wood species (M. ramiflorus and A. serrata) exhibited steep declines in species richness at the plantation native forest boundary, suggesting that the contrasting stand types (native remnant and young regenerating plantation stands) with their different microclimate may have had a significant influence. Future research needs to compare the saproxylic fauna of dead wood in mature plantation stands with adjacent native remnants to ascertain if the effect of native habitat proximity is due to landscape composition or a reflection of microclimatic differences. The large diversity of saproxylic species observed during this study highlights the importance of plantations as habitat for saproxylic species, particularly in heavily fragmented landscapes that retain little original native forest. My research findings provide forest managers with options for improving forest management to enhance opportunities for the conservation of saproxylic invertebrates. In addition my thesis provides one of the most comprehensive multi-taxon data sets of saproxylic species associated with a variety of deadwood resources. This information will be invaluable to future researchers that continue to work on New Zealand’s saproxylic fauna.

Intensive land use with resulting reduction and loss of habitats is one of the reasons behind the loss of biodiversity that the world is currently facing. In Sweden, natural forests are scarce today because of intensive forestry, which has led to a decline in many forest habitats, such as dead wood. One organism that has been heavily affected by loss of habitat is the white-backed woodpecker. This bird prefers deciduous forests rich in dead wood and more than 200 threatened species of insects and other organisms also prefer this habitat. For this reason the white-backed woodpecker is considered an umbrella species. In order to restore deciduous forests rich in dead wood and thereby favor species depending on this, dead deciduous wood is created artificially, often by ring-barking. Studies of artificially created deciduous dead wood are still largely lacking. The aim of this study is to contribute to research in deciduous forests by comparing ring-barked birches to naturally dead birches in terms of density of insect holes and woodpecker foraging activity (in general, not of a certain species). Insect holes were counted up to 2.2 meters and woodpecker foraging activity was scored on a scale from 1 - 5 on 144 ring-barked and 132 naturally dead birches across six sites in Uppland, Västmanland and Gästrikland, Sweden. Ring-barked birches did not have as many insect holes/surface area as did naturally dead trees and this differed between sites. Woodpecker foraging activity, on the other hand, did not differ between the dead wood categories but differed between sites. Further, both density of insect holes and woodpecker foraging activity increased with the diameter of the trees and woodpecker foraging activity also increased with number of insect holes/surface area across both dead wood categories. The results suggest that ring-barked birches do not fully mimic naturally dead birches when it comes to insect abundance but woodpeckers forage on ring-barked birches to a similar extent as on naturally dead birches. Thus, ring-barking of birches does not fully replace naturally dead wood of birch but it can serve as an important complement.

Darbo tikslas: ištirti stambios negyvos medienos pasiskirstymo dėsningumus lapuočių miškuose. Darbo objektas: Tyrimai atlikti Biržų girios lapuočių medynuose. Darbo metodai: Atrankiniai tyrimai atlikti Biržų girios lapuočių miškuose. Darbo rezultatai: Daugiausiai Biržų girioje lapuočių medynuose sausuolių rasta jaunuolynuose – 11 vnt., o virtuolių brandžiuose medynuose – 45 vnt. ir 3 vnt. sausuolių. Jaunuolynuose virtėlių rasta 26 vnt. Pribręstančiuose medynuose virtėlių – 37 vnt., sausuolių – 6 vnt. Pusamžiuose medynuose virtėlių – 41 vnt., o sausuolių – 7 vnt. Apskaičiavus Biržų girios lapuočių medynų stambios negyvos medienos tūrius 0,625 ha didžiausią kiekį sukaupę brandūs medynai – 15,66 m3, o mažiausiai jaunuolynai – 10,78 m3 . Viename hektare jaunuolynuose stambios negyvos medienos. / The aim of the work – To investigate the major spatial patterns of dead wood of deciduous forests. Object of the work – The object of study was carried out Biržų deciduous forest stands. Methods of the work – Selected studies were carried out Biržų forest of deciduous forests. The results of the work – Most deciduous forest stands Biržų dead found in young - 11 pcs., And virtuolių mature stands - 45 pcs. and 3 units. dead. In young logs found in 26 pieces. Mature stands logs - 37 pcs., Dead - 6 pcs. A middle-aged stands logs - 41 pcs., And the dead - 7 units. Calculation Biržų forest hardwood stands of large volumes of dead wood 62.5 reparing maximum amount of accumulated mature stands - 15.66 m3 and the least young stands - 10.78 m3. One hectare of young stands of large dead wood - 17.24 m3, premature -20.86, -24.52 m3 half-life and mature - 25.05 m3.

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Forest management contributes to the changes in forest structure by turning heterogenous forests of varied age into homogenous forests of similar age and thus affect bird species depending on different structures or habitats which are lost during forestry. In this report, a study was made to investigate how the amount of decidious trees, dead wood and variation in tree diameter affect bird diversity. The purpose of this study was to be able to give forest management guidelines to increase bird diversity. This study was conducted by investigating 65 transects in forests of different structure south of Linköping, Sweden. Along the 65 transects, birds were inventoried as well as the vegetation. The trees were measured in 5 circles along each transect. The data from the investigations both on birds and vegetation were analysed by using generalized linear models. The results showed that amount of deadwood and variation in tree diameter had the strongest effects on bird diversity, and to some extent the amount of decidious trees. By applying this knowledge of the positivt effects on birds when increasning the amount of deadwood, decidious trees and variation in tree diameter in the forests, it is possible to create better conditions for maintaining species richness and diversity.

The maintenance of downed woody debris supplies is increasingly being recognized as an integral part of forest management. In order to better manage this resource, it is important to assess its role in supporting biodiversity. In this thesis, I investigate the responses of carabid communities to variation in woody debris availability in an experimental manipulation of woody debris volume in closed canopy forests and following a biomass harvest in a clearcut. Within closed-canopy forests, total carabid abundance and the abundances of eight species increased significantly with increasing volumes of various types of woody debris, particularly large diameter, late-decay conifer wood. Similarly, a strong affinity with woody debris was observed in the clearcut. These findings suggest that reductions in woody debris will have negative consequences for carabids and indicate the need to ensure a diverse and abundant supply of woody debris during stand development.

The maintenance of downed woody debris supplies is increasingly being recognized as an integral part of forest management. In order to better manage this resource, it is important to assess its role in supporting biodiversity. In this thesis, I investigate the responses of carabid communities to variation in woody debris availability in an experimental manipulation of woody debris volume in closed canopy forests and following a biomass harvest in a clearcut. Within closed-canopy forests, total carabid abundance and the abundances of eight species increased significantly with increasing volumes of various types of woody debris, particularly large diameter, late-decay conifer wood. Similarly, a strong affinity with woody debris was observed in the clearcut. These findings suggest that reductions in woody debris will have negative consequences for carabids and indicate the need to ensure a diverse and abundant supply of woody debris during stand development.

This study compared the length, diameter, volume and amount of dead wood in reaches of the Lögde River and its tributaries one year and three years post instream restoration. This was part of a follow up of the ReBorN restoration project. Wood pieces greater than 1 m in length and 0,1 m in diameter was surveyed. The variables were compared between above and below the former highest coastline and between mainstem and tributary. Wood clustering and placement within each reach was also examined. There were no differences in length, diameter, volume and amount dead wood between one year and three years post restoration. However, in some of the reaches individual differences were significant for some of the variables. The result indicates greater difference between one year and three years post restoration in mainstem and above the highest coastline. The clustering of dead wood in the reaches was not coherent, but in a majority of the reaches the dead wood were more clustered year three. It may have been too close in time after restoration to see any effect. It is also possible that the instream restoration is not sufficient to increase the presence of dead wood in the Lögde River. Further follow up is suggested to draw a conclusion.

In many natural forests, forest managers fell and debark spruces (Picea abies) colonised by theEuropean spruce bark beetle (Ips typographus) to prevent the beetle from spreading to other tree stands. The aim of this study was to examine how this method affects the biodiversity of other saproxylic beetle species. Eclector traps were installed on debarked and non-debarked dead spruces of four different ages in four nature reserves to compare the richness and composition of saproxylic beetles. The results indicated that a significantly higher number of species and individuals emerged from standing dead trees with bark compared to debarked logs. The highest emergence of species and individuals occurred in one-year-old standing trees with bark. There was a significant interaction between the type and the age of wood, suggesting thatthe richness declined with the aging of wood with bark, while it remained constantly low in debarked logs. The species composition varied greatly between standing trees with bark and debarked logs, as well as between standing trees with bark of different ages. This study demonstrated that debarking spruces as a pest control method reduces the diversity of nontarget saproxylic beetle species. Potential reasons behind that could be the hardening and drying of consumable parts of the wood, rendering it inhabitable for many saproxylic organisms, as well as the presence of the European spruce bark beetle itself, which is associated with many other species.