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Zusammenfassung: Deadwood is gaining greater importance in the context of forestry activities. The forestry sector meanwhile has realized that the promotion and preservation of natural dead-wood occurrences is of immense importance for ecosystem services, since it serves as a reservoir for biological and functional diversity. An important objective of this comprehensive study/ thesis was to explore the impact of different forest management intensities on the microbial diversity in deadwood of the two in Germany silviculturally important tree species 〈i〉Fagus sylvatica〈/i〉 and 〈i〉Picea abies〈/i〉. Furthermore, the relationship be-tween tree species-specific physico-chemical properties and the associated changes of microbial diversity and species composition should be elucidated. A significant methodological focus was on the combination of modern molecular techniques ("Next-generation sequencing") together with classical field (-observation) mycology. This recent thesis comprises three independent but complementary chapters.〈i〉Chapter 2〈/i〉 encompasses a study on the diversity and structure of fungal communities in the deadwood of the two above mentioned tree species 〈i〉Fagus sylvatica〈/i〉 and 〈i〉Picea abies〈/i〉. This study further investigates the relation between physico-chemical properties and fungal diversity and whether an increase in diversity refers to higher lignin-modifying enzyme activities and increased wood decomposition rates, respectively. The study combines 454 pyrosequencing (to identify the fungal community), enzyme assays and chemical elements analyses (mass spectrography). The work presents the first comparison of the deadwood (-ecosystems) of these two economically relevant coniferous and deciduous tree species. The results revealed that the fungal communities strongly correspond to the specific deadwood substrate, which occurred to be independently from the surrounding habitat. This fact clearly relates to the specific substrate properties. The results further revealed that forest management type (age class managed beech and spruce forests versus extensively managed beech forests) significantly impacts the fungal community structure on the according forest plots. Both tree species also displayed distinct fungal successional patterns (dynamics). White-rot causing 〈i〉Resinicium bicolor〈/i〉, for example, occurred to be dominant on 〈i〉Picea abies〈/i〉 deadwood logs of all decay stages, whereas members of the 〈i〉Xylariaceae〈/i〉 were dominating the initially decayed logs of 〈i〉Fagus sylvatica〈/i〉 and then were substituted by 〈i〉Polyporaceae〈/i〉 (e.g. 〈i〉Fomes formentarius〈/i〉).〈i〉Chapter 3〈/i〉 describes the investigations of the distribution of 〈i〉nifH〈/i〉 genes in the same deadwood logs described in chapter 2. N-availability is highly restricted in deadwood and since the 1960s, it is assumed that fungi meet their N requirements for forming fruiting bodies by associating with bacteria which are capable to fix atmospheric dini-trogen and make it biologically available. The investigated 〈i〉nifH〈/i〉 gene which encodes for dinitrogenase reductase hereby serves as the marker gene for diazotrophs and has been detected in various environments and ecosystems. The results of the presented study revealed that the 〈i〉nifH〈/i〉 genes that were detected in deadwood are highly specific to this substrate and have not been found in other substrates (e.g. oceans, rivers, lakes, soils and oil spills). The study further showed that the 〈i〉nifH〈/i〉 OTU community structure significantly varied between deadwood logs of 〈i〉Fagus〈/i〉 and 〈i〉Picea〈/i〉. The results also indicate a significant correlation between 〈i〉nifH〈/i〉 OTU richness and sporocarps on the investigated logs. Network analyses based on non-random species co-occurrence patterns revealed interactions among fungi and N-fixing bacteria in the deadwood and strongly indicate the occurrence of at least commensal relationships between these taxa. 〈i〉Chapter 4〈/i〉 presents the results of the first investigation of the total bacterial diversity in decaying deadwood under natural conditions. 〈i〉Alphaproteobacteria〈/i〉, 〈i〉Acidobacteria〈/i〉 and 〈i〉Actinobacteria〈/i〉 were the dominant taxonomic groups on both tree species. There were no differences in bacterial OTU richness between the tree species but richness tended to increase with progressing wood decay. Interestingly, bacteria from the order 〈i〉Rhizobiales〈/i〉 became more abundant during the intermediate and advanced stages of decay, accounting for up to 25% of the entire diversity in such logs. The most dominant OTU was taxonomically assigned to the genus 〈i〉Methylovirgula〈/i〉, which was before isolated from woodblocks of Fagus sylvatica and has been shown to also possess the 〈i〉nifH〈/i〉 gene. In line to the results on fungi (chapter 2) this study also demonstrates that the bacterial community structure was influenced by a range of deadwood species' physico-chemical properties including decay stage, water content, pH, and C and N availability. Furthermore, intensive forest management also negatively impacted bacterial diversity.Altogether, the results of the three presented chapters of this thesis substantially contribute to the identification of rather unknown fungal and bacterial diversity, that are part of deadwood decomposition processes. The fact that these communities are not independent from each other and rather interact depending on e.g. tree species, decay stage and forest management practices, demonstrates that they have to be considered as an integral and functional part of biodiversity in forest ecosystems. By applying novel molecular sequencing techniques, it is possible to further explore this “blackbox”
Note:
Dissertation Albert-Ludwigs-Universität Freiburg 2015
Language:
English
URN:
urn:nbn:de:bsz:25-freidok-102282
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