Dead wood is an important part of forest ecosystems, especially since so many organisms depend on it for nutrients or as substrate for breeding or foraging. Since forestry intensified in northern Europe during the mid 1900s, the amount of dead wood in Fennoscandian forests has drastically decreased. For wood-inhabiting organisms such as fungi, this has led to changes in the community composition with many species becoming rare and threatened by extinction. To increase the volume of dead wood, restoration actions aim to create dead wood artificially by for example prescribed burning or by ring-barking trees. In coniferous forests, artificially created dead wood is known to be colonized by many wood-inhabiting fungi, indicating that it can work as a substitute of naturally dead wood. There is, however, a shortage for similar studies in deciduous forests and especially birch dominated ones. In this study, we examine the wood-inhabiting fungal community composition on standing dead wood of birches in east central Sweden. Data was collected with single surveys of fruitbody presence on both ringbarked and naturally dead trees during late autumn. We found that there is a difference in the fungal community composition between the dead wood categories, with form groups of Corticoids and Pyrenomycetes being significantly more abundant on ring-barked birches thanon naturally dead birches. This includes species such as Stereum rugosum and Jackrogersella multiformis. A total of 41 fungal species were observed in this study, out of which 30 species were observed on ringbarked trees and 31 species observed on naturally dead trees. The most observed species was Fomes fomentarius, which appeared numerously on trees of both deadwood categories. Our results indicated that the presence of Fomes fomentarius correlate with lower foraging activity of woodpeckers. However, further research is needed to evaluate if fungal species can be used as indicators for successful restoration actions in relation to the activity of insects and foraging woodpeckers. We conclude that ring-barked birches work well as suitable substrate for many fungal species and that ring-barking as a restoration action is useful for the community of wood-inhabiting fungi.

Community ecology is the study of the patterns and processes governing species abundance, distribution, and diversity within and between communities. Likewise, phylogeography is the study of the historic processes controlling genetic diversity across space. Both fields investigate diversity, albeit at different temporal, spatial and taxonomic scales and therefore have varying assumptions. Community ecology typically focuses on contemporary mechanisms whereas phylogeography studies historic ones. However, new research has discovered that both genetic and community diversity can be influenced by contemporary and historic processes in tandem. As such, a growing number of researchers have called for greater integration of phylogeography and ecology to better understand the mechanisms structuring diversity. In this dissertation I attempt to add to this integration by investigating ways that phylogeography and population genetics can enhance studies on community ecology. First, I review traditional studies on freshwater fish community assembly using null model analyses of species co-occurrence, which shows that fish are largely structured by deterministic processes, though the importance of different mechanisms varies across climates, habitats, and spatial scales. Next, I show how phylogeographic data can greatly enhance inferences of community assembly in freshwater fish communities in Costa Rica and Utah respectively. My Costa Rican analyses indicate that historic eustatic sea-level change can be better at predicting community structure within a biogeographic province than contemporary processes. In comparison, my Utah analyses show that historic dispersal between isolated basins in conjunction with contemporary habitat filtering, dispersal limitation, and extinction dynamics both influence community assembly through time. Finally, I adapt a forward-time population genetics stochastic simulation model to work in a metacommunity context and integrate it with Approximate Bayesian Computation to infer the processes that govern observed community composition patterns. Overall, I show that community ecology can be greatly enhanced by including information and methods from different but related fields and encourage future ecologists to further this research to gain a greater understanding of biological diversity.

Increased biodiversity generally enhances terrestrial ecosystem productivity. While niche-use efficiency is thought to drive the biodiversity-productivity relationship, the mechanisms within niche-use efficiency are not well understood. A potential mechanism for niche-use efficiency is nutrient-use efficiency. To measure nutrient-use efficiency, we calculated nitrogen-resorption efficiencies (NRE) because nitrogen is an important growth limiting nutrient for forest productivity. We used a plantation implemented as a full factorial design that included two levels of competition, implemented as different planting densities (one- and two-meter planting densities), and three diversity levels (monocultures, two-, and three-species plantings) that included three hardwood tree species (northern red oak (<i>Quercus rubra</i>), black cherry (<i>Prunus serotin</i><i>a</i>), and American chestnut (<i>Castanea dentata</i>). For our nitrogen-resorption efficiency data, we found that NRE increased as diversity and planting density decreased, but the magnitude of the response varied among species. This outcome suggests that while increased diversity likely provides a release from intra-specific competition, different combinations of species will play a critical role in shaping biodiversity-productivity relationships. Forest nutrient cycling can also be influenced by herbivory. To address the effects of forest diversity on herbivory rates, we monitored rates of foliar damage along with foliar nitrogen content. To measure foliar nitrogen content, we collected spectral data from early, midseason, and late season foliar samples. To assess foliar damage, we collected and imaged leaves from two canopy positions in order to measure late season foliar area and estimate pre damaged foliar area. We found that diversity and foliar nitrogen content have a positive relationship, and diversity does influence canopy damage but the effects vary among species and density. Upon further analysis, we found that foliar nitrogen content and canopy damage are correlated. Meaning individual trees showed a release from intraspecific competition, which lead to an increase in available nutrients and higher canopy quality, showing that stands with higher canopy quality experienced higher levels of damage.<br>

<p> Kudzu (Pueraria montana) is an invasive woody vine widespread throughout the  southeastern United States, with recent studies predicting that its habitat will expand northward.  New occurrences and recent studies using climatic parameters suggest that the Midwestern  region of the United States is at the greatest risk of kudzu invasion. As there have already been  25 reports of kudzu within the Great Lakes basin, and no previous landscape models exist for the  basin, I developed probability models from existing spatial data (land cover, hydrology, geology,  annual precipitation, elevation, aspect, and known kudzu locations) using generalized additive,  bioclimate envelope, and maximum entropy methods. I further expanded each model to include  the basin and a 2.25-degree buffer in order to include 193 reported kudzu sites. For each  predictive model, I determined the area under the curve (AUC) for a receiver operating  characteristic curve (ROC) comparing false positive and false negative rates. I performed field  surveys at eight known sites of kudzu presence in Michigan, Indiana, and Ohio. Each presence  site was paired with a control (known kudzu absence site). I collected environmental data  including canopy cover, volumetric soil moisture, soil pH, litter depth, midstory species diversity  and diameter at breast height (DBH), and overstory basal area. Each environmental measure was  compared between kudzu presence and control survey sites as well as between in-basin and out?of-basin survey sites using a two-way ANOVA. Maximum entropy models produced the highest  AUC in both the basin and buffer models during model development. These models showed that  urban and disturbed habitats resulted in the greatest probability of potential habitat for kudzu. I  found no statistically significant differences in environmental characteristics between kudzu  absent and presence sites or between in- and out-of-basin sites, suggesting kudzu might be  dispersal-limited rather than limited by environmental characteristics. Continuing existing  management and further monitoring of kudzu spread is likely necessary to limit further  introduction and to mitigate spread of kudzu within the Great Lakes region.  </p>

Phylogenetic Community Structure (PCS) metrics are becoming more common in community ecology. PCS metrics estimate the phylogenetic relatedness among members of an ecological community or assemblage. If ecological traits are conserved, then phylogenetic clustering (i.e., taxa are more closely related than expected by chance) indicates habitat filtering as the key process in community assembly. On the other hand, a pattern of phylogenetic overdispersion (i.e., taxa are more distantly related than expected by chance) suggests competition is dominant. Most studies to date have used PCS of unmanipulated ecosystems, but the value of PCS metrics will be best revealed in experiments. This project used PCS for aquatic beetle (Coleoptera) assemblages in experimentally manipulated seasonal wetlands on a cattle ranch in south-central Florida, and compared PCS metrics to standard ecological metrics. Wetlands were experimentally treated with all combinations of pasture management, fencing to exclude cattle, and controlled burning during 2006-2009. Beetle assemblages in fenced wetlands were significantly more overdispersed compared to non-fenced wetlands, suggesting that this treatment decreases habitat filtering, causing competition to become the dominant process in community formation. There was also a significant pasture x fence x burn interaction effect, with assemblages in wetlands differing in PCS depending on what combination of the three treatments were applied. Phylogenetic Diversity (PD – a measure of branch length of a community or assemblage on a phylogenetic tree) was highly correlated with genera richness (number of genera), and these metrics along with the expected number of genera (D – an ecological diversity index) found significant differences among burn treatments and a pasture x iii burn interaction. The results of this study indicate that PCS metrics complement classical ecological methods and should be widely applied.

<p>This study is part of an ongoing project established in 2007 as an emerald ash borer (<em>Agrilus planipennis</em>) trapping study. The primary objective of this thesis was to assess how forests have changed following the loss of ash over a 15-year period, from 2007 to 2022. The study aimed to answer three key questions: 1) How has the loss of ash affected the regeneration and recruitment patterns of ash and other tree species? 2) Which specific species are driving forest regeneration and recruitment in the absence of ash? 3) Can the data be used to predict future changes in forest composition following the loss of ash? To achieve these objectives, I conducted analyses of 44 forests representing 19 different forest types in Indiana, Michigan, and Ohio. Forest composition was examined at the overstory, midstory and understory levels to capture the overall impact of ash loss on forest regeneration and succession. Despite the decline or total loss in overstory ash, ash regeneration continued at most sites from 2017 to 2022. However, ash regeneration was not observed at 15 sites, and competition from established shade-tolerant species, such as red maple and American elm, was identified as a primary factor hindering ash recruitment. The loss of ash did not lead to significant changes in forest types. Forest types at all sites remained stable, with only minor shifts in dominant species. Tree species that were already present in the overstory filled the space left by the lost ash, thereby maintaining the existing forest types. In terms of driving species, my findings demonstrated a rapid increase in red maple dominance across all sites, particularly in the absence of ash. Red maple exhibited vigorous growth, suggesting it plays a crucial role in shaping future forest composition following ash loss. Other species, including black cherry, American elm, and American basswood, also contributed to forest regeneration, with some sites showing a shift toward a higher abundance of these species. Although the loss of ash has led to changes in forest composition, existing species have shown resilience and adaptability in filling the niche left by the lost genus. The long-term effects of emerald ash borer infestation on forest ecosystems are complex and multifaceted. This study provides insights into the regeneration and recruitment patterns of ash and other tree species following ash loss. The data suggest that while forests have experienced loss of ash, the remaining understory and midstory individuals of this species may contribute to future overstory recruitment. Furthermore, the dominance of red maple highlights its potential as a key driver of forest composition in the wake of ash loss. </p>

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