Aims: The soil microbial community plays a critical role in increasing phosphorus (P) availability in low-P, weathered soils by "mining" recalcitrant organic P through the production of phosphatase enzymes. However, there is a lack of data on the fungal and bacterial taxa which are directly involved in P mining, which could also serve as potential microbial bioindicators of low P availability. Methods and Results: Leveraging a 5-year P enrichment experiment on low-P forest soils, high-throughput sequencing was used to profile the microbial community to determine which taxa associate closely with P availability. We hypothesized that there would be a specialized group of soil microorganisms that could access recalcitrant P and whose presence could serve as a bioindicator of P mining. Community profiling revealed several candidate bioindicators of P mining (Russulales, Acidobacteria Subgroup 2, Acidobacteriales, Obscuribacterales and Solibacterales), whose relative abundance declined with elevated P and had a significant, positive association with phosphatase production. In addition, we identified candidate bioindicators of high P availability (Mytilinidales, Sebacinales, Chitinophagales, Cytophagales, Saccharimonadales, Opitulales and Gemmatales). Conclusions: This research provides evidence that mitigating P limitation in this ecosystem may be a specialized trait and is mediated by a few microbial taxa. Significance and Impact of the Study: Here, we characterize Orders of soil microbes associated with manipulated phosphorus availability in forest soils to determine bioindicator candidates for phosphorus. Likewise, we provide evidence that the microbial trait to utilize recalcitrant organic forms of P (e.g. P mining) is likely a specialized trait and not common to all members of the soil microbial community. This work further elucidates the role that a complex microbial community plays in the cycling of P in low-P soils, and provides evidence for future studies on microbial linkages to human-induced ecosystem changes. nutrient in many terrestrial ecosystems (Elser et al. 2007), the use of fossil fuels and fertilizers have increased N inputs in Eastern North American forests, which can shift the balance of nutrients in these ecosystems (Davidson and Howarth 2007

Our work explores how differing mycorrhizal associations of temperate hardwood trees (i.e., arbuscular [AM] versus ectomycorrhizal [ECM] associations) affect soil fungal communities by altering the diversity and relative abundance of saprotrophic and plant-pathogenic fungi along natural gradients of mycorrhizal dominance. Because temperate hardwood forests are predicted to become more AM dominant with climate change, studies examining soil communities along mycorrhizal gradients are necessary to understand how these global changes may alter future soil fungal communities and their functional potential.

1. Plant-soil feedback (PSF) is known to influence plant community composition, and recent work suggests that these effects may be regulated by traits related to mycorrhizal associations and phylogenetic relationships. However, there is a critical need to test the usefulness of these traits in predicting PSF outcomes in natural plant communities. 2. To test for evidence of mycorrhizal and phylogenetic controls over PSF at both the species and community level, we examined the spatial relationship between adult and juvenile trees in stem-mapped hardwood forest plots using point pattern analyses and linear mixed-effect models. 3. We found that spatial patterns of adult and juvenile trees, as well as overall adult tree recruitment, were significantly affected by the dominant mycorrhizal type of our forested communities, but were not influenced by the phylogenetic relationship between adult and juvenile trees. Additionally, PSF experienced by individual species was dependent on the mycorrhizal dominance of the surrounding community. 4. Spatial patterns in communities dominated by arbuscular mycorrhizal trees reflected overdispersion between adult and juvenile trees (suggestive of negative PSF), while communities dominated by ectomycorrhizal trees reflected clustering (suggestive of positive PSF). 5. Our findings indicate that PSFs are driven by the mycorrhizal associations of dominant trees, with effects of dominant community member traits on soil microorganisms and biogeochemistry 'spilling over' onto less abundant individuals in the community. Our research supports the use of whole-community, mycorrhizalbased frameworks for studying PSF in plant communities where multiple mycorrhizal types are present.

Green roof soils are usually engineered for purposes other than urban biodiversity, which may impact their fungal communities, and in turn impact the health of plants in the urban ecosystem. We examined the drivers of fungal diversity and community composition in soil of green roofs and adjacent ground-level green spaces in three Midwestern USA cities-Chicago, Cleveland, and Minneapolis. Overall, fungal communities on green roofs were more diverse than ground-level green spaces and were correlated with plant cover (positively) and roof age (negatively) rather than abiotic soil properties. Fungal community composition was distinct between roof and ground environments, among cities, and between sampling sites, but green roofs and their immediately surrounding ground-level green space showed some similarity. This suggests dispersal limitation may result in geographic structuring at large spatial scales, but dispersal between roofs and their neighbouring sites may be occurring. Different fungal taxonomic and functional groups were better explained when roofs were classified either by depth (extensive or intensive) or functional intent of the roof design (i.e. stormwater/energy, biodiversity, or aesthetics/recreation). Our results demonstrate that green roofs are an important reservoir of fungal diversity in the urban landscape, which should be considered in future green roof design.

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