Tag Archives: undergraduate

Soil systems – the challenges of complexity and scale

Soils are complex systems, in which physical, geochemical and biological processes interact in aggregate structures situated in dynamically shifting air- and water-filled spaces. It is difficult to adequately sample soil properties and to model processes related to those soil measurements. These challenges were discussed in a stimulating three-day conference on Complex Soils Systems in Berkeley a few weeks ago. Attendees came from an incredible diversity of backgrounds with a common interest in tackling issues in soil science. The need to better understand soils was motivated by the importance of soil processes in climate and for figuring out “How to feed the soil and the planet?” in the anthropocene – a question posed early on by Professor John Crawford. 

Issues of scale were brought up explicitly or were evident implicitly in many of the presentations. Namely, that relevant processes in biogeochemical cycles occur over a wide range of spatial (nano- to mega-meter) and temporal (seconds to millennia) scales, but our observations are typically limited to a much narrower scope given measurement and resource constraints. These issues were elegantly summarized in the recent article “Digging Into the World Beneath Our Feet: Bridging Across Scales in the Age of Global Change” by Hinckley, Wieder, Fierer and Paul in Eos, Transactions American Geophysical Union 95 (11), 96-97. In a real sense, the scale issue presents problems when societal decisions regarding soil sustainability and ecosystem services are made using data and models derived from different (often smaller) spatial scales than are relevant to the policies and issues themselves.

One illustration of the concept of a spatially complex soil system is illustrated with the figure below by California College of the Arts (CCA) student Sakurako Gibo. The image depicts a theoretical assemblage of soil microbes with different morphologies (for instance round spores versus string-like mycelia). In the second figure, the complex system is “pulled apart” into bins that might represent the effect of a sampling strategy that subsamples components of the whole system. The information about the original complex assemblage and connections is not retained, and as a result, data and rules based off of the binned samples may be different from the case in the real intact community.

Spatially complex microbial community

Spatially complex microbial community

Spatial ordering is lost in measurements and models

Spatial ordering pulled apart

What to do? I walked away from the meeting in awe of the amount of unanswered questions on soil complexity and scale. However, with the increasing technical capability in soil and microbial measurements, and efforts at meetings like this one, made it evident that progress will continue in this area.

I’ll end with another neat set of figures produced by CCA student Leslie Greene who illustrated an emergent pattern of predicted H2 consumption (o) based on the availability of H2 (•) from the atmosphere (distributed) and from N2-fixing root nodules (gray filled circles). She created the pattern of H2 consumption based on one rule, soil moisture had to be above 10% and below 50%, as indicated by the concentric rings around water-logged soil sites (red filled circles). From this simple scheme, an irregular pattern emerges of the location where H2 consumption occurs. When faced with the complexity of soil, it is easy to feel paralyzed, and perhaps starting with a simple approach like this will help me embrace the system and its questions.

Emergent H2 system

Emergent patterns of H2 consumption


At a slightly more macro scale

Thank you for the BioDesign course organizers at California College of the Arts (Tobi Lyn Schmidt and Mike Bogan)!

Undergraduate Researcher Shersingh’s SURGE Experience

Congratulations to visiting undergraduate researcher Shersingh Joseph Tumber-Davila on completing and thriving in the demanding eight-week Summer Undergraduate Research in Geoscience and Engineering (SURGE) program! Shersingh came to the Welander lab with a strong background in environmental research (news article) from his home institution of the University of New Hampshire. SURGE is a competitive earth science research and graduate school preparation program, which is specifically designed to recruit students of diverse backgrounds from other universities across the country. I was amazed at the number of activities the program had for the students including GRE test preparation, faculty seminars, career and grad school panels, and field trips. This was all while performing graduate-level research including a oral and poster presentation at the end of the program. Shersingh approached all these demands with amazing energy and attitude, which we’d really like acknowledge!

SURGE student Shersingh

SURGE student Shersingh

In Shersingh’s research, he asked whether microbe-mediated hydrogen (H2) uptake support C mineralization in soils. Soils are a strong sink for atmospheric H2, which is presumably used by soil microorganisms to fuel their energy metabolism. In addition, emissions of H2 have grown since the industrial revolution, so the availability of H2 energy to soil microbes likely also increased. Shersingh tested the influence of excess H2 on the ability of soil microbes to mineralize soil carbon for a variety of carbon substrates, especially those that can be energy intensive (e.g., lignin and lignocellulose). He used Streptomyces ghanaensis as a model organism containing high affinity hydrogenase (H2 uptake) and laccase (lignin breakdown) genes. By measuring carbon dioxide respiration rates and intermediate products involved in the breakdown of lignin and lignocellulose, we found evidence for increased breakdown of lignocellulose (straw) with elevated levels of H2. This may point to a  link between the H2 and C biogeochemical cycles in soils that will be interesting to pursue further. This project is in collaboration with Stanford postdoc Marco Keiluweit who specializes in soil carbon cycling.

BioDesign course – bridging science and art

Biologist/architect team Tobi Lyn Schmidt and Mike Bogan created a course linking artists, designers, architects, and biologists from the California College of the Arts (CCA) and Stanford University. I served as a postdoc mentor to help inspire and guide the process of cross-hybridizing biology and design (some examples) with three really talented undergraduate CCA students: Leslie Greene, Sakurako Gibo, and David Lee.

The students were first charged with creating designs to illustrate scientific concepts in my field of research. I challenged them think about the issue of scale with respect to the biogeochemical cycles I study. The processes I investigate occur over a wide range of spatial and temporal scales, which is a challenge for their measurement and interpretation. David focused on a selection of atmospheric trace gases with a wide range of abundances, and that interact with each other through key reactions. In his image, the hydroxyl radical (OH) is illustrated by the white dot from which orange and blue strings respectively represent the path length to molecules of  hydrogen (H2) and methane (CH4) in the surrounding space. The density of the strings is representative of the concentration of H2 and CH4 relative to OH. I love the sense of competition in this image. These reduced molecules compete for reaction with OH, and with other trace gases not shown, which helps explain the relatively their long lifetimes of H2 (~2 years) and CH4 (~10 years) in the atmosphere.

Concentration Burst, by David Lee

Concentration Burst, by David Lee

The second task for the students was to manipulate a biological system for design or artistic ends. All three students visited the Welander geobiology lab at Stanford and the Berry lab at Carnegie on campus where atmospheric trace gases are measured. For her project, Leslie was interested in manipulating microorganisms to reveal art. Using a combination of strains from the lab and purchased online, Leslie created competitive interactions between organisms and against antibiotics to reveal structures that were both patterned and complex. In the example below, she laid a cross-pattern of Streptomyces ghanaensis and Bacillus subtilis colonies and let them grow and compete. Intriguing features arose, appearing as if the Streptomyces strain grew on top of the Bacillus strain, perhaps antagonistically or not. Leslie overlaid emergent patterns in topology and color from microbial cultures with and without competition to create an amazing image that reveals some very aesthetic order in the systems.

Bio-manipulation of Streptomyces ghanaensis and Bacillus subtilis

Bio-manipulation of Streptomyces ghanaensis and Bacillus subtilis

Emergent patterns from competition

Emergent patterns with and without competition


Finally, the students illustrated various concepts related to my work including artistic renditions of Streptomyces colonies and concepts of complexity (see related post). I really love the feel of the image created by Sakurako Gibo showing the atmospheric H2 concentrations that I measured between the ground and top of a measurement tower (y-axis) over the year-long experiment (x-axis) at Harvard Forest as an ephemeral curtain. Higher concentrations of H2 are represented with a deeper intensity of blue. The impact of the soil sink is illustrated by the lightening of the color near the base of the image caused by high rates of soil microbial H2 consumption in summer and fall.

Curtain of H2 Harvard Forest

Curtain of H2 at Harvard Forest, by Sakurako Gibo


ISME 14 – The power of the small

Last week I attended ISME 14 (International Symposium on Microbial Ecology) in Copenhagen, Denmark. It was a delight to see the city – its juxtaposed giant modern, cool, sterile buildings surrounding the historic old city. More of a delight was unexpectedly running into friends from the MBL Microbial Diversity summer school (2010) and realizing they are now my colleagues.

Presenting a poster that Deepa Rao and I co-authored on the “Physiology of the microbe-mediated soil sink for atmospheric H2” at ISME in Copenhagen, Denmark.

The conference itself was quite good. I appreciated the range of content from very big picture and abstract to focused experimental projects. One message I took away from the community was a sort of -omics backlash, or perhaps whiplash, to the idea that generating more and more -omics data is the sole future for microbial ecology. It seems that presenters coming from both the -omics and experimental side were acknowledging the importance of both tools, and especially of using them together. Those seem to be a lot of tools for any one scientist to master, so I am encouraged that the tone was of collaborative holistic approaches for tackling scientific questions.

Wind turbines and modern architecture outside of Copenhagen

I really enjoyed a somewhat unique session. It was a discussion entitled “Frontiers in microbial ecosystem science: Energizing the research agenda” sponsored at this and other conferences by the US National Science Foundation. All sorts of issues were raised in a discussion of “what needs to be done” – what are the important topics and how should we advance microbial ecology. I was struck by how strong the arguments were that microbial ecology is important for understanding, and possibly mitigating, climate change. This is my main interest, but I often find the microbial ecology literature and research interests so focused on minute points (I think my own project included), that it is difficult to see the link between the microbial and global scales. At this session I learned that it is not only because it is difficult to do, but also because the funding agencies seem to push scientists to write grants in one or the other. It is difficult to be interdisciplinary (falling under more than one NSF department). It has been a (fun) challenge for me to try to get a foot in both atmospheric and microbial ecology science, and it was encouraging to hear from the community that the intersection of the two is valued.

Tuborg beer and the Royal Copenhagen porcelain company

Deepa receives Goetze Prize for Undergraduate Research

At the 2012 EAPS Student Awards Ceremony Deepa Rao received the Christopher Goetze Prize for Undergraduate Research for her thesis entitled : “Exploring the Microbe-mediated Soil H2 sink: A lab-based study of the physiology and related H2 consumption of isolates from the Harvard Forest LTER.” The award recognizes “ innovative experimental design, care in data collection, and sensitive application of results to research problems.”

Click here for a description of her Senior Thesis Presentation 

It has been a pleasure to supervise Deepa’s thesis research and her results will contribute to our research efforts to understand the mechanisms driving the soil sink for atmospheric H2. Professor Ron Prinn acts as the faculty advisor for both Deepa and I.

Deepa Rao accepting the award from her academic advisor Sam Bowring

Feature in EAPS article: Atmospheric chemistry redux

Atmospheric Chemistry Redux

MIT Department of Earth, Atmospheric and Planetary Science article describing the expansion of the atmospheric chemistry program at MIT over the past five years with a short feature on our work to understand the H2 soil sink in the field and in the lab.

DEAPS Extreme Weather and Climate 2011

This week I traveled up to Mt. Washington with this year’s EAPS FPOP (Freshman Pre-Orientation Program) Discover Earth, Atmosphere and Planetary Sciences: Extreme Weather & Climate. It’s the third time I’ve acted as a TA for the program by heading up the flora and fauna section, or what is now more commonly known as “Flora with Laura.”

Describing the link between vegetation and microclimate in the Alpine Garden

The 3 day program is Spotlighted on the PAOC website, which describes it as being “designed to provide incoming freshmen with the opportunity to explore the science of weather and climate through an exciting combination of lectures and fluids experiments, providing a glimpse into some of the most interesting and challenging aspects of research in PAOC.

I’ve always be interested in plants. My father (and now one of my sisters) is a forester in the diverse mixed forests of Southern Oregon. The flora of trails I’ve hiked always interested me, especially the relationships between plant communities and regional climate (and even micro-climates) that were obvious even to my untrained eyes. Shrubby grasslands cover convex faces of the hills in Big Sur, CA, while coastal redwoods thrive in the moist and cool concave recesses. The towering forests of the North Cascades, WA are a world apart from the flowering cacti of the Mojave. However, it wasn’t until I took the Field Course in Arctic Science, held at both the University of Alaska, Fairbanks and the remote Toolik Field Station on the North Slopes of Alaska, that I formally learned about the adaptations of plants (and animals) to climate. We focused on different strategies plants employ for survival in harsh environments, specifically to arctic environments.

The material from that course translates beautifully to Mt. Washington because, just as plants adapt to the harsher climates found at higher latitudes, the plants found at different altitudes on Mt. Washington must adapt to increasingly harsher alpine conditions. Therefore, the altitude gradient on a mountain in Massachusetts reflects the latitudinal gradient from Massachusetts to the northernmost reaches of Alaska. Interestingly, many of the species on the summits of New England are also found in northern most Alaska – the alpine mountain top climes are the last refuge of arctic plants that extended to mid-latitudes during the last ice age.

The DEAPS group ascends the Mt. Washington auto road from the base near Pinkham Notch at 2032 ft to the peak at 6288 ft. The students make temperature, wind speed and pressure measurements to note how the weather varies up the mountain on that day. I teach them how to use the plant ecosystems as the key indicator of the year-long weather experienced at different altitudes on the mountain. The presence of plants that are adapted to cold temperatures, short growing seasons, ice and wind abrasion, high uv light, low water and nutrient retention, and other environmental stresses are visual indicators of the harshness of the year-round weather on Mt. Washington. Students note how these hardy plants increase in prevalence as we ascend the mountain, which confirms their lessons in how weather up the mountain also becomes more extreme.

DEAPS group at the Mt. Washington summit

Beyond the actual instruction, it’s a unique opportunity to interact with incoming MIT freshman; often we are the first group of MIT students and staff that they interact with upon arrival. Students come from all over the country and the world, and they are eager to start their academic and personal lives at MIT.