Weisenhorn Pamela B.

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Weisenhorn
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Pamela B.
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Preprint

Wheat rhizosphere harbors a less complex and more stable microbial co-occurrence pattern than bulk soil

2018-07-25 , Fan, Kunkun , Weisenhorn, Pamela B. , Gilbert, Jack A. , Chu, Haiyan

The rhizosphere harbors complex microbial communities, whose dynamic associations are considered critical for plant growth and health but remain poorly understood. We constructed co-occurrence networks for archaeal, bacterial and fungal communities associated with the rhizosphere and bulk soil of wheat fields on the North China Plain. Rhizosphere co-occurrence networks had fewer nodes, edges, modules and lower density, but maintained more robust structure compared with bulk soil, suggesting that a less complex topology and more stable co-occurrence pattern is a feature for wheat rhizosphere. Bacterial and fungal communities followed a power-law distribution, while the archaeal community did not. Soil pH and microbial diversity were significantly correlated with network size and connectivity in both rhizosphere and bulk soils. Keystone species that played essential roles in network structure were predicted to maintain a flexible generalist metabolism, and had fewer significant correlations with environmental variables, especially in the rhizosphere. These results indicate that distinct microbial co-occurrence patterns exist in wheat rhizosphere, which could be associated with variable agricultural ecosystem properties.

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Soil bacterial diversity is associated with human population density in urban greenspaces

2018-04 , Wang, Haitao , Cheng, Minying , Dsouza, Melissa , Weisenhorn, Pamela B. , Zheng, Tianling , Gilbert, Jack A.

Urban greenspaces provide extensive ecosystem services, including pollutant remediation, water management, carbon maintenance, and nutrient cycling. However, while the urban soil microbiota underpin these services, we still have limited understanding of the factors that influence their distribution. We characterized soil bacterial communities from turf-grasses associated with urban parks, streets and residential sites across a major urban environment, including a gradient of human population density. Bacterial diversity was significantly positively correlated with the population density; and species diversity was greater in park and street soils, compared to residential soils. Population density and greenspace type also led to significant differences in the microbial community composition that was also significantly correlated with soil pH, moisture and texture. Co-occurrence network analysis revealed that microbial guilds in urban soils were well correlated. Abundant soil microbes in high density population areas had fewer interactions, while abundant bacteria in high moisture soils had more interactions. These results indicate the significant influence of changes in urban demographics and land-use on soil microbial communities. As urbanization is rapidly growing across the planet, it is important to improve our understanding of the consequences of urban zoning on the soil microbiota.

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Article

Representing the function and sensitivity of coastal interfaces in earth system models

2020-05-18 , Ward, Nicholas D. , Megonigal, J. Patrick , Bond-Lamberty, Benjamin , Bailey, Vanessa L. , Butman, David , Canuel, Elizabeth A. , Diefenderfer, Heida , Ganju, Neil K. , Goni, Miguel , Graham, Emily B. , Hopkinson, Charles S. , Khangaonkar, Tarang , Langley, J. Adam , McDowell, Nate G. , Myers-Pigg, Allison N. , Neumann, Rebecca B. , Osburn, Christopher L. , Price, René M. , Rowland, Joel , Sengupta, Aditi , Simard, Marc , Thornton, Peter E. , Tzortziou, Maria , Vargas, Rodrigo , Weisenhorn, Pamela B. , Windham-Myers, Lisamarie

Between the land and ocean, diverse coastal ecosystems transform, store, and transport material. Across these interfaces, the dynamic exchange of energy and matter is driven by hydrological and hydrodynamic processes such as river and groundwater discharge, tides, waves, and storms. These dynamics regulate ecosystem functions and Earth’s climate, yet global models lack representation of coastal processes and related feedbacks, impeding their predictions of coastal and global responses to change. Here, we assess existing coastal monitoring networks and regional models, existing challenges in these efforts, and recommend a path towards development of global models that more robustly reflect the coastal interface.

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The response of nematodes to deep-sea CO2 sequestration : a quantile regression approach

2010-01 , Fleeger, John W. , Johnson, David S. , Carman, K. R. , Weisenhorn, Pamela B. , Gabriele, A. , Thistle, D. , Barry, James P.

One proposed approach to ameliorate the effects of global warming is sequestration of the greenhouse gas CO2 in the deep sea. To evaluate the environmental impact of this approach, we exposed the sediment-dwelling fauna at the mouth of the Monterey Submarine Canyon (3262 m) and a site on the nearby continental rise (3607 m) to CO2- rich water. We measured meiobenthic nematode population and community metrics after ~30-day exposures along a distance gradient from the CO2 source and with sediment depth to infer the patterns of mortality. We also compared the nematode response with that of harpacticoid copepods. Nematode abundance, average sediment depth, tail-group composition, and length: width ratio did not vary with distance from the CO2 source. However, quantile regression showed that nematode length and diameter increased in close proximity to the CO2 source in both experiments. Further, the effects of CO2 exposure and sediment depth (nematodes became more slender at one site, but larger at the other, with increasing depth in the sediment) varied with body size. For example, the response of the longest nematodes differed from those of average length. We propose that nematode body length and diameter increases were induced by lethal exposure to CO2-rich water and that nematodes experienced a high rate of mortality in both experiments. In contrast, copepods experienced high mortality rates in only one experiment suggesting that CO2 sequestration effects are taxon specific.

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