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Urban green areas are becoming increasingly recognized for their biodiversity potential. However, little is known about how urbanization shapes cryptic species communities, such as those residing in deadwood. In this study, we investigated downed Norway spruce trunks at intermediate stages of decay, in urban and semi-natural forests in southern Finland. To understand the interconnections between landscape context, deadwood characteristics and wood-inhabiting fungal communities, we studied structural characteristics, surface epiphyte cover and internal moisture and temperature conditions of the tree trunks, and fungal communities residing in the wood. Our findings showed that urban tree trunks had less epiphyte cover and lower moisture than trunks in semi-natural forests. Overall, urban forests provide less favourable habitats for a majority of the dominant wood-inhabiting fungal species and for red-listed species as a group. Yet, 33% of urban trunks hosted at least one red-listed species. While these landscape-scale effects may be driven by local climatic conditions as well as contingencies related to available species pools, our results also highlight the significance of substrate-scale variability of deadwood in shaping wood-inhabiting fungal communities. We show that epiphyte cover is a significant driver or indicator of these small-scale dynamic processes in deadwood.

Urban forests are often remnants of former larger forested areas, and traditionally considered as degraded habitats due to negative effects of urbanization. However, recent studies have shown that urban forests managed for recreational purposes can be structurally close to natural forests and may provide habitat features, such as dead wood, that are scarce in intensively managed forest landscapes. In this study, we assessed how urbanization affects polypore species richness and the number of red-listed polypore species in forest stands, and the occurrences of polypore species on individual units of dead wood. Spruce-inhabiting polypore assemblages and their associations to urbanization, local habitat connectivity and dead-wood abundance were investigated in southern Finland. The effects of urbanization on polypore species richness and individual species were largely negligible when other environmental variability was accounted for. Several red-listed polypore species were found in deadwood hotspots of urban forests, though urbanization had a marginally significant negative effect on their richness. The main driver of total species richness was dead-wood abundance while the number of red-listed species was also strongly dependent on local habitat connectivity, implying that a high degree of fragmentation can decrease their occurrence in urban forests. We conclude that the highest potential for providing habitats for threatened species in the urban context lies in large peri-urban recreational forests which have been preserved for recreational purposes around many cities. On the other hand, overall polypore diversity can be increased simply by increasing dead-wood abundance, irrespective of landscape context.

Urban forests are usually not intensively managed and may provide suitable environments for species threatened by production forestry. Thus, urban forests could have the potential of enhancing biodiversity both within cities and at a larger landscape scale. In this study, we investigated stand structures of boreal urban forests to assess them in terms of naturalness and biodiversity conservation potential. We sampled two types of urban spruce-dominated stands: random urban stands as representatives of average urban forests, and valuable urban stands known to host high polypore richness and assumed to represent urban biodiversity hotspots. Urban forests were compared to rural forests with different levels of naturalness. Living and dead trees and cut stumps were measured from all studied stands. Urban forests had generally diverse living tree structures with abundant large-diameter trees. Random urban forests had more dead wood (median 10.1 m(3) ha(-1)) than production forests (2.7 m(3) ha(-1)) but still considerably less than protected, former production forests (53.9 m(3) ha(-1)) or semi-natural forests (115.6 m(3) ha(-1)). On the other hand, valuable urban forests had relatively high median volume of dead wood (88.2 m(3) ha(-1)). We conclude that the combination of diverse stand composition and the presence of old-growth characteristics in boreal urban forests form a strong baseline from which their biodiversity value can be further developed, e.g. by leaving more fallen or cut trees to form dead wood. We propose that urban forests could become significant habitats for biodiversity conservation in the future.

High performance materials are becoming of great interest in many fields. Understanding the behavior of these materials under stress at micrometer scale is of great importance for this development. To determine local deformations in a material, an optical pattern may be attached on the material surface. A semi-automated device, able to print a suitable optical pattern on metallic surface using microcontact printing, was manufactured. Good precision in placing the stamping head on the surface, in order to avoid smearing of the pattern was reached. Despite posing challenges in handling of the ink and in the consistency of the patterns, this method proved viable for effective and fast creation of optical patterns.

Forests and other natural environments retained in cities and their surroundings provide recreational opportunities for urban residents and refuges for urban wildlife. From the perspective of biodiversity conservation, urban forests offer interesting prospects for creating habitat structures, such as old and dead trees, that are scarce in surrounding rural forest landscapes. Yet, habitat fragmentation and urban environmental stressors may deteriorate habitat quality for species that are not well adapted to living in human-altered landscapes. In this thesis, I investigate how availability of deadwood, forest fragmentation and urbanization together play out to shape wood-inhabiting fungal diversity across a rural-urban gradient. The study was conducted in spruce-dominated forests in southern Finland, mainly in the Helsinki metropolitan area and the surrounding region. This area provides an interesting setting for addressing the relationships between urbanization and wood-inhabiting biodiversity as the region is relatively urbanized but retains high forest cover where deadwood has been retained in variable quantities. The study consists of three interrelated parts. Firstly, urban forests were characterized based on forest stand measurements to outline the current and potential resource availability in urban forests and to evaluate these with respect to corresponding rural forest types. Secondly, fungal fruiting-body survey data was collected and analyzed to identify which landscape-level characteristics and processes are relevant in shaping diversity patterns of wood-inhabiting polypore fungi in urbanized environments. Thirdly, fungal communities of decaying spruce trunks were studied by means of DNA sequencing to identify possible substrate-scale mechanisms, by which wood-inhabiting fungi could be affected by urbanization. The results showed that spruce-dominated urban forests in southern Finland differed from respective rural forests in terms of living and deadwood composition. Quantities of deadwood in typical urban forests were relatively low and close to the levels in production forests, but stands with high amounts of deadwood were also present in the urban forest landscape. Polypore species richness across a rural-urban gradient was driven primarily by local availability of deadwood and forest connectivity. Urbanization had a negligible role in explaining patterns of species occurrences and the overall species richness. However, the species richness of red-listed polypores was negatively associated with urbanization. Downed, intermediately decayed spruce trunks in urban forests were drier, had less epiphyte cover and hosted fewer red-listed fungal species than respective trunks in semi-natural rural forests. Differences in fungal community composition between spruce trunks in urban and semi-natural forests corresponded more with wood-microclimatic variability than with variability in epiphyte cover. Overall, this thesis demonstrates that, despite some negative effects associated with urbanization, urban forests can still host diverse wood-inhabiting fungal assemblages, when deadwood resources are made available. However, if the conservation of threatened spruce-associated species is to be promoted in urban forests, it is necessary to retain adequately large intact forest areas to ensure habitat continuity and to buffer against urban environmental stressors. Kaupunkimetsien hoito antaa monessa suhteessa vapaammat kädet luonnon monimuotoisuuden huomioimiseen kuin vastaavien ensisijaisesti talouskäytössä olevien metsien hoito. Vähäinen tarve puun korjuulle kasvattaa mahdollisuuksia lisätä esimerkiksi vanhojen puiden sekä lahopuun määrää, mikä luo elinmahdollisuuksia monelle sopivien ympäristöjen puutteesta kärsivälle lajille. Toisaalta kaupungistuneisuuden vaikutukset ja metsien pirstoutuneisuus saattavat heikentää erikoituneiden metsälajien elinolosuhteita kaupunkimetsissä. Tässä väitöskirjatyössä tutkin kaupunkimetsien potentiaalia lahopuulla elävän sienilajiston monimuotoisuuden turvaamisessa. Tutkimuksessa keskityttiin eteläisen Suomen kuusivaltaisiin kangasmetsiin, pääasiassa pääkaupunkiseudulla ja sen lähialueilla. Pääkaupunkiseudun asutuskeskusten välillä on säästynyt eurooppalaisittain runsaasti metsäalueita, jotka vaihtelevat koon ja luonnontilaisuuden suhteen. Tutkimus koostuu kolmesta osatyöstä. Ensimmäisessä osatyössä selvitettiin kaupunkimetsien erityispiirteitä suhteessa vastaaviin maaseudun hoidettuihin ja hoitamattomiin metsätyyppeihin puuston rakenteen ja lahopuuston perusteella. Toisessa osatyössä selvitettiin lahoavalla kuusella esiintyvän kääpälajiston yhteyksiä maiseman kaupungistuneisuuteen itiöemäinventointiaineiston pohjalta. Kolmannessa osatyössä tutkittiin kaupungistuneisuuden, lahopuun ominaisuuksien ja lahopuussa elävien sieniyhteisöjen keskinäisiä yhteyksiä yksittäisten lahopuukappaleiden tasolla. Tässä osatyössä kuusimaapuiden sienilajistoa selvitettiin DNA-metaviivakoodaustekniikan avulla. Tulokset osoittivat, että kuusivaltaiset kaupunkimetsät poikkeavat puustorakenteeltaan vastaavista maaseudun talous- ja suojelumetsistä. Lahopuuston osalta kaupunkimetsät olivat yleisesti lähimpänä talousmetsiä, mutta lahopuun määrissä oli laajaa vaihtelua. Kaupunkialueilla esiintyi paikoin myös erittäin runsaslahopuustoisia metsäkohteita. Kuusella esiintyvän kääpälajiston runsautta selittivät ennen kaikkea paikallinen lahopuun määrä ja osin myös vanhan metsän kytkeytyneisyys. Kun edellä mainitut muuttujat otettiin huomioon, kaupungistuneisuudella ei ollut merkittävää yhteyttä yksittäisten kääpälajien esiintymiseen ja kääpälajien kokonaismäärään. Kaupungistuneisuudella havaittiin kuitenkin olevan negatiivinen yhteys uhanalaisten ja silmälläpidettävien kääpien lajirunsauteen. Kuusimaapuiden havaittiin olevan kaupunkimetsissä keskimäärin kuivempia ja vähemmän sammalpeitteisiä kuin vastaavat maapuut luonnonmetsissä, ja niissä esiintyi harvemmin uhanalaista ja silmälläpidettävää sienilajistoa. Vaihtelu puun kosteus- ja lämpöoloissa selitti eroja kaupunki- ja luonnonmetsissä sijaitsevien lahorunkojen sienilajikoostumuksessa paremmin kuin sammalpeitteisyyden vaihtelu. Kaupungistumisen mahdollisista kielteisistä vaikutuksista huolimatta kaupunkimetsissä voidaan ylläpitää runsaslajisia lahopuulla eläviä sieniyhteisöjä, mikäli lahopuun määrä on riittävän suuri. Lahoavalla kuusella elävän uhanalaisen sienilajiston tukeminen edellyttää myös riittävän laajojen yhtenäisten metsäalueiden säilyttämistä lahopuujatkumoiden turvaamiseksi sekä kaupungistuneisuuden vaikutusten puskuroimiseksi.