<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Kevin M. Geyer</style></author><author><style face="normal" font="default" size="100%">John E. Barrett</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Unimodal productivity–diversity relationships among bacterial communities in a simple polar soil ecosystem</style></title><secondary-title><style face="normal" font="default" size="100%">Environmental Microbiology</style></secondary-title><short-title><style face="normal" font="default" size="100%">Environ Microbiol</style></short-title></titles><dates><year><style  face="normal" font="default" size="100%">2019</style></year><pub-dates><date><style  face="normal" font="default" size="100%">07/2019</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">https://onlinelibrary.wiley.com/doi/full/10.1111/1462-2920.14639</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">21</style></volume><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;Unlike other macroecological principles, relationships between productivity and diversity have not been effectively tested for microbial communities. Here we describe an experiment in which the availability of resources to soil bacterial communities was manipulated in a model system, the McMurdo Dry Valleys of Antarctica. Mannitol additions were used to simulate a productivity gradient such that a response in bacterial biomass production, taxonomic diversity and functioning (e.g., enzyme activity) were induced. Resource amendment induced a positive linear response in microbial productivity (P &amp;lt; 0.001) but a unimodal (hump‐shaped) response in microbial diversity at multiple taxonomic scales (P = 0.035). Putative oligotrophic (e.g., phyla &lt;em&gt;Nitrospirae&lt;/em&gt; and &lt;em&gt;Cyanobacteria&lt;/em&gt;) and copiotrophic (e.g., phylum &lt;em&gt;Proteobacteria&lt;/em&gt;) taxa were apparent through substantial community turnover along the resource gradient. Soil enzyme activity was inversely related to bacterial biomass but positively related to diversity, suggesting the latter may be a stronger control over enzyme‐mediated decomposition. The mechanisms behind this pattern are consistent with macroecological theory of a shift from environmental (e.g., stress tolerance) to biotic (e.g., competition) drivers with increasing resource availability. This evidence is among the first of its kind to document a significant unimodal productivity&amp;ndash;diversity relationship for soil bacteria.&lt;/p&gt;</style></abstract><issue><style face="normal" font="default" size="100%">7</style></issue></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Kevin M. Geyer</style></author><author><style face="normal" font="default" size="100%">Cristina D. Takacs-Vesbach</style></author><author><style face="normal" font="default" size="100%">Michael N. Gooseff</style></author><author><style face="normal" font="default" size="100%">John E. Barrett</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Primary productivity as a control over soil microbial diversity along environmental gradients in a polar desert ecosystem</style></title><secondary-title><style face="normal" font="default" size="100%">PeerJ</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">2017</style></year><pub-dates><date><style  face="normal" font="default" size="100%">07/2017</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">https://peerj.com/articles/3377/</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">5</style></volume><pages><style face="normal" font="default" size="100%">e3377</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;&lt;span style=&quot;font-size: 11pt; font-family: AdvP7627;&quot;&gt;Primary production is the fundamental source of energy to foodwebs and ecosystems, and is thus an important constraint on soil communities. This coupling is particularly evident in polar terrestrial ecosystems where biological diversity and activity is tightly constrained by edaphic gradients of productivity (e.g., soil moisture, organic carbon availability) and geochemical severity (e.g., pH, electrical conductivity). In the McMurdo Dry Valleys of Antarctica, environmental gradients determine numerous properties of soil communities and yet relatively few estimates of gross or net primary productivity (GPP, NPP) exist for this region. Here we describe a survey utilizing pulse amplitude modulation (PAM) fluorometry to estimate rates of GPP across a broad environmental gradient along with belowground microbial diversity and decomposition. PAM estimates of GPP ranged from an average of 0.27 &lt;/span&gt;&lt;span style=&quot;font-size: 11pt; font-family: AdvPS7DA6;&quot;&gt;m&lt;/span&gt;&lt;span style=&quot;font-size: 11pt; font-family: AdvP7627;&quot;&gt;mol O&lt;/span&gt;&lt;span style=&quot;font-size: 8pt; font-family: AdvP7627; vertical-align: -2pt;&quot;&gt;2&lt;/span&gt;&lt;span style=&quot;font-size: 11pt; font-family: AdvP7627;&quot;&gt;/m&lt;/span&gt;&lt;span style=&quot;font-size: 8pt; font-family: AdvP7627; vertical-align: 5pt;&quot;&gt;2&lt;/span&gt;&lt;span style=&quot;font-size: 11pt; font-family: AdvP7627;&quot;&gt;/s in the most arid soils to an average of 6.97 &lt;/span&gt;&lt;span style=&quot;font-size: 11pt; font-family: AdvPS7DA6;&quot;&gt;m&lt;/span&gt;&lt;span style=&quot;font-size: 11pt; font-family: AdvP7627;&quot;&gt;mol O&lt;/span&gt;&lt;span style=&quot;font-size: 8pt; font-family: AdvP7627; vertical-align: -2pt;&quot;&gt;2&lt;/span&gt;&lt;span style=&quot;font-size: 11pt; font-family: AdvP7627;&quot;&gt;/m&lt;/span&gt;&lt;span style=&quot;font-size: 8pt; font-family: AdvP7627; vertical-align: 5pt;&quot;&gt;2&lt;/span&gt;&lt;span style=&quot;font-size: 11pt; font-family: AdvP7627;&quot;&gt;/s in the most productive soils, the latter equivalent to 217 g C/m&lt;/span&gt;&lt;span style=&quot;font-size: 8pt; font-family: AdvP7627; vertical-align: 5pt;&quot;&gt;2&lt;/span&gt;&lt;span style=&quot;font-size: 11pt; font-family: AdvP7627;&quot;&gt;/y in annual NPP assuming a 60 day growing season. A diversity index of four carbon-acquiring enzyme activities also increased with soil productivity, suggesting that the diversity of organic substrates in mesic environments may be an additional driver of microbial diversity. Overall, soil productivity was a stronger predictor of microbial diversity and enzymatic activity than any estimate of geochemical severity. These results highlight the fundamental role of environmental gradients to control community diversity and the dynamics of ecosystem-scale carbon pools in arid systems.&amp;nbsp;&lt;/span&gt;&lt;/p&gt;</style></abstract><issue><style face="normal" font="default" size="100%">10</style></issue></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Kevin M. Geyer</style></author><author><style face="normal" font="default" size="100%">Adam E. Altrichter</style></author><author><style face="normal" font="default" size="100%">Cristina D. Takacs-Vesbach</style></author><author><style face="normal" font="default" size="100%">Michael N. Gooseff</style></author><author><style face="normal" font="default" size="100%">John E. Barrett</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Bacterial community composition of divergent soil habitats from a polar desert.</style></title><secondary-title><style face="normal" font="default" size="100%">FEMS Microbiology Ecology</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">2014</style></year><pub-dates><date><style  face="normal" font="default" size="100%">08/2014</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">89</style></volume><pages><style face="normal" font="default" size="100%">490-494</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Edaphic factors such as pH, organic matter, and salinity are often the most significant drivers of diversity patterns in soil bacterial communities. Desert ecosystems in particular are model locations for examining such relationships as food web complexity is low and the soil environment is biogeochemically heterogeneous. Here, we present the findings from a 16S rRNA gene sequencing approach used to observe the differences in diversity and community composition among three divergent soil habitats of the McMurdo Dry Valleys, Antarctica. Results show that alpha diversity is significantly lowered in high pH soils, which contain higher proportions of the phyla Acidobacteria and Actinobacteria, while mesic soils with higher soil organic carbon (and ammonium) content contain high proportions of Nitrospira, a nitrite-oxidizing bacteria. Taxonomic community resolution also had a significant impact on our conclusions, as pH was the primary predictor of phylum-level diversity, while moisture was the most significant predictor of diversity at the genus level. Predictive power also increased with increasing taxonomic resolution, suggesting a potential increase in nic</style></abstract><issue><style face="normal" font="default" size="100%">2</style></issue><work-type><style face="normal" font="default" size="100%">Short Communication</style></work-type><section><style face="normal" font="default" size="100%">490</style></section></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>32</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Kevin M. Geyer</style></author></authors><secondary-authors><author><style face="normal" font="default" size="100%">John E. Barrett</style></author></secondary-authors></contributors><titles><title><style face="normal" font="default" size="100%">Environmental Controls Over the Distribution and Function of Antarctic Soil Bacterial Communities</style></title><secondary-title><style face="normal" font="default" size="100%">Biological Sciences</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">biogeochemistry</style></keyword><keyword><style  face="normal" font="default" size="100%">biogeography</style></keyword><keyword><style  face="normal" font="default" size="100%">McMurdo Dry Valleys</style></keyword><keyword><style  face="normal" font="default" size="100%">microbial ecology</style></keyword><keyword><style  face="normal" font="default" size="100%">productivity/diversity theory</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2014</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://hdl.handle.net/10919/64417</style></url></web-urls></urls><publisher><style face="normal" font="default" size="100%">Virginia Tech</style></publisher><pub-location><style face="normal" font="default" size="100%">Blacksburg, VA</style></pub-location><volume><style face="normal" font="default" size="100%">Ph.D.</style></volume><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;div title=&quot;Page 2&quot;&gt;&lt;div&gt;&lt;div&gt;&lt;p&gt;Microbial community composition plays a vital role in soil biogeochemical cycling. Information that explains the biogeography of microorganisms is consequently necessary for predicting the timing and magnitude of important ecosystem services mediated by soil biota, such as decomposition and nutrient cycling. Theory developed to explain patterns in plant and animal distributions such as the prevalent relationship between ecosystem productivity and diversity may be successfully extended to microbial systems and accelerate an emerging ecological understanding of the &amp;quot;unseen majority.&amp;quot; These considerations suggest a need to define the important mechanisms which affect microbial biogeography as well as the sensitivity of community structure/function to changing climatic or environmental conditions. To this end, my dissertation covers three data chapters in which I have 1) examined patterns in bacterial biogeography using gradients of environmental severity and productivity to identify changes in community diversity (e.g. taxonomic richness) and structure (e.g. similarity); 2) detected potential bacterial ecotypes associated with distinct soil habitats such as those of high alkalinity or electrical conductivity and; 3) measured environmental controls over the function (e.g. primary production, exoenzyme activity) of soil organisms in an environment of severe environmental limitations. Sampling was performed in the polar desert of Antarctica&amp;#39;s McMurdo Dry Valleys, a model ecosystem which hosts microbially-dominated soil foodwebs and displays heterogeneously distributed soil properties across the landscape. Results for Chapter 2 indicate differential effects of resource availability and geochemical severity on bacterial communities,&amp;nbsp;&lt;span style=&quot;font-size: 0.923em;&quot;&gt;with a significant productivity-diversity relationship that plateaus near the highest observed concentrations of the limiting resource organic carbon (0.30mg C/g soil). Geochemical severity (e.g. pH, electrical conductivity) primarily affected bacterial community similarity and successfully explained the divergent structure of a subset of samples. 16S rRNA amplicon pyrosequencing further revealed in Chapter 3 the identity of specific phyla that preferentially exist within certain habitats (i.e.&amp;nbsp;Acidobacteria&amp;nbsp;in alkaline soils,&amp;nbsp;Nitrospira&amp;nbsp;in mesic soils) suggesting the presence of niche specialists and spatial heterogeneity of taxa-specific functions (i.e. nitrite oxidation). Additionally, environmental parameters had different explanatory power towards predicting bacterial richness at varying taxonomic scales, from 57% of phylum-level richness with pH to 91% of order- and genus-level richness with moisture. Finally, Chapter 4 details a simultaneous sampling of soil communities and their associated ecosystem functions (primary productivity, enzymatic decomposition) and indicates that the overall organic substrate diversity may be greater in mesic soils where bacterial diversity is also highest, thus a potentially unforeseen driver of community dynamics. I also quantified annual rates of soil production which range between 0.7 - 18.1g C/m2/yr from the more arid to productive soils, respectively. In conclusion, the extension of biogeographical theory for macroorganisms has proven successful and both environmental severity and resource availability have obvious (although different) effects on the diversity and composition of soil microbial communities.&lt;/span&gt;&lt;/p&gt;&lt;/div&gt;&lt;/div&gt;&lt;/div&gt;&lt;p&gt;&amp;nbsp;&lt;/p&gt;</style></abstract><work-type><style face="normal" font="default" size="100%">doctoral</style></work-type></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Kevin M. Geyer</style></author><author><style face="normal" font="default" size="100%">Adam E. Altrichter</style></author><author><style face="normal" font="default" size="100%">David J. Van Horn</style></author><author><style face="normal" font="default" size="100%">Cristina D. Takacs-Vesbach</style></author><author><style face="normal" font="default" size="100%">Michael N. Gooseff</style></author><author><style face="normal" font="default" size="100%">John E. Barrett</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Environmental controls over bacterial communities in polar desert soils</style></title><secondary-title><style face="normal" font="default" size="100%">Ecosphere</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">2013</style></year><pub-dates><date><style  face="normal" font="default" size="100%">10/2013</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">4</style></volume><pages><style face="normal" font="default" size="100%">art127</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><issue><style face="normal" font="default" size="100%">10</style></issue></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">David J. Van Horn</style></author><author><style face="normal" font="default" size="100%">Van Horn, M. Lee</style></author><author><style face="normal" font="default" size="100%">John E. Barrett</style></author><author><style face="normal" font="default" size="100%">Michael N. Gooseff</style></author><author><style face="normal" font="default" size="100%">Adam E. Altrichter</style></author><author><style face="normal" font="default" size="100%">Kevin M. Geyer</style></author><author><style face="normal" font="default" size="100%">Lydia H. Zeglin</style></author><author><style face="normal" font="default" size="100%">Cristina D. Takacs-Vesbach</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Factors Controlling Soil Microbial Biomass and Bacterial Diversity and Community Composition in a Cold Desert Ecosystem: Role of Geographic Scale</style></title><secondary-title><style face="normal" font="default" size="100%">PLoS ONE</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">2013</style></year><pub-dates><date><style  face="normal" font="default" size="100%">06/2013</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0066103</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">8</style></volume><pages><style face="normal" font="default" size="100%">e66103</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><issue><style face="normal" font="default" size="100%">6</style></issue></record></records></xml>