A5025358852- Climate change and permafrost
- Soil Carbon and Nitrogen Dynamics
- Peatlands and Wetlands Ecology
- Microbial Community Ecology and Physiology
- Methane Hydrates and Related Phenomena
- Cryospheric studies and observations
- Atmospheric and Environmental Gas Dynamics
- Polar Research and Ecology
- Geology and Paleoclimatology Research
- Plant Water Relations and Carbon Dynamics
- Biocrusts and Microbial Ecology
- Soil and Water Nutrient Dynamics
- Genomics and Phylogenetic Studies
- Legume Nitrogen Fixing Symbiosis
- Indigenous Studies and Ecology
- Ecology and Vegetation Dynamics Studies
- Plant nutrient uptake and metabolism
- Lichen and fungal ecology
- Soil and Unsaturated Flow
- Aquatic Ecosystems and Phytoplankton Dynamics
- Plant responses to elevated CO2
- Arctic and Antarctic ice dynamics
- Gut microbiota and health
- Geological Studies and Exploration
- Plant Ecology and Soil Science
San Diego State University
2016-2025
Savoirs dans l'espace anglophone : représentations, culture, histoire
2020
Foundation Medicine (United States)
2017
Cornell University
2012
University of Colorado Boulder
1996-2006
The finding that microbial communities are active under snow has changed the estimated global rates of biogeochemical processes beneath seasonal packs. We used microbiological and molecular techniques to elucidate phylogenetic composition undersnow in Colorado, United States. Here, we show tundra soil biomass reaches its annual peak snow, fungi account for most biomass. Phylogenetic analysis revealed a high diversity three novel clades constitute major new groups (divergent at subphylum or...
Significance Arctic ecosystems are major global sources of methane. We report that emissions during the cold season (September to May) contribute ≥50% annual methane from Alaskan tundra, based on fluxes obtained eddy covariance sites and regional calculated aircraft data. The largest were observed at driest site (<5% inundation). Emissions in linked extended “zero curtain” period, where soil temperatures poised near 0 °C, indicating total very sensitive climate related factors, such as...
ABSTRACT The period when the snowpack melts in late spring is a dynamic time for alpine ecosystems. large winter microbial community begins to turn over rapidly, releasing nutrients plants. Past studies have shown that soil dry meadows of Colorado Rocky Mountains changes biomass, function, broad-level structure, and fungal diversity between early summer. However, little specific information exists on bacterial or how it during this ecologically important period. We constructed clone...
OPINION article Front. Microbiol., 16 June 2015Sec. Systems Microbiology Volume 6 - 2015 | https://doi.org/10.3389/fmicb.2015.00615
Past studies of plant–microbe interactions in the alpine nitrogen cycle have revealed a seasonal separation N use, with plants absorbing primarily during summer months and microbes immobilizing autumn months. On basis these studies, it has been concluded that competition for between is minimized along this gradient. In study, we examined more deeply links microbial population dynamics plant availability an dry meadow. We conducted year-round field study performed experiments on isolated soil...
Amino acids are released during the decomposition of soil organic matter and have been shown to be utilized as a nitrogen source by some non-mycorrhizal species in family Cyperaceae (the sedge family). Twelve out 13 examined current study were capable absorbing amino state. With two exceptions (two genus Kobresia), from subalpine or alpine habitats exhibited lower rates total uptake compared more temperate habitats, which is possibly explained growth overall demand for nitrogen. The higher...
Much of the 191.8 Pg C in upper 1 m Arctic soil organic mater is, or is at risk of, being released to atmosphere as CO 2 and/or CH 4 . Global warming will further alter rate emission these gases atmosphere. Here we quantify effect major environmental variables affected by global climate change on fluxes Alaskan Arctic. Soil temperature best predicts and explained 89% variability emissions. Water table depth has a nonlinear impact efflux. Increasing water height above surface retards...
Arctic peat soils contain vast reserves of organic C and are largely anaerobic. However, anaerobic respiration, particularly the role Fe(III) humic substances as electron acceptors, is not well understood in such ecosystems. We investigated these processes a drained thaw lake basin on coastal plain near Barrow, Alaska. measured concentrations soluble Fe other potential described microbial community, performed experiments laboratory field to measure net rates reduction relationship this...
Bacteria and fungi, representing two major soil microorganism groups, play an important role in global nutrient biogeochemistry. Biogeographic patterns of bacterial fungal biomass are fundamental importance for mechanistically understanding cycling. We synthesized 1323 data points phospholipid fatty acid-derived C (FBC), (BBC), fungi:bacteria (F:B) ratio topsoil, spanning 11 biomes. The FBC, BBC, F:B display clear biogeographic along latitude environmental gradients including mean annual...
A metagenomic analysis was performed on a soil profile from wet tundra site in northern Alaska. The goal to link existing biogeochemical knowledge of the system with organisms and genes responsible for relevant metabolic pathways. We specifically investigated how importance iron (Fe) oxides humic substances (HS) as terminal electron acceptors this ecosystem is expressed genetically, respiratory fermentative processes varied depth into active layer upper permafrost. Overall, metagenomes...
Abstract Introduction Rapidly advancing technologies and accumulating information about microbial communities across the globe allow quantification of properties functions at a macro‐scale. These emerging biogeographic patterns call for practical macroecological approach to investigate their underlying mechanisms. Aims The primary aims this paper are review advancements macroecology in seeking mechanisms governing patterns, further lay out roadmap 10 years. Methods We reviewed progress...
Abstract Globally, soils store two to three times as much carbon currently resides in the atmosphere, and it is critical understand how soil greenhouse gas (GHG) emissions uptake will respond ongoing climate change. In particular, soil‐to‐atmosphere CO 2 flux, commonly though imprecisely termed respiration ( R S ), one of largest fluxes Earth system. An increasing number high‐frequency measurements (typically, from an automated system with hourly sampling) have been made over last decades;...
In this study, soil bacterial communities and the temperature responses (Q10) of substrate-induced respiration were compared between an alpine dry meadow a subalpine forest in Colorado Rocky Mountains. Bacterial three seasons from each environment described with 16S rRNA gene clone libraries. The main goal comparison was to relate phylogenetic differences among variation respiratory sensitivities along seasonal altitudinal gradients. warmer, lower elevation, exhibited large variations Q10....