Hooked! Seductive Details in Soil Science

Abstract

Science literacy requires the target audience to engage with science concepts presented in written, oral, or visual formats. Anecdotes that elicit the personal interest of the audience can be “seductive details” (van den Broek, 37) that increase motivation to connect with the materials being presented. Soil science is a field where we are constantly battling the “it's just dirt” mindset. The seductive detail can be a useful tool in proactively generating interest in our field. The collection above is admittedly unstructured—loosely tied to the topic of cultural aspects of soil. For the lay audience and for students having their first exposure to soil science, that cultural perspective can link soil science to the very fabric of human life—seemingly a key characteristic for a seductive detail in any of the sciences. Commenting on a 2014 SSSA-sponsored Bouyoucos Conference that explored soils and ecosystem services in a societal context, Mary Stromberger of the Department of Soil and Crop Sciences at Colorado State University noted that “the study of soil from a human-centric point of view is key to getting public and ultimately government support for long-term soil conservation and management” (Soil Science Society of America, 33). In both the classroom, and in dealing with the broader community, adding novel human-centric perspectives—ones that moves beyond the now-tired image of cupped hands holding soil and a seedling—can enhance the effectiveness our dialog. Sadly, the systematic assembly and usage of such materials in soil science is rare. The best example that comes to mind is Mary Beth Kirkham's placement of biographical sketches of key historical figures at the end of each chapter in her book Principles of Soil and Plant Water Relations (Kirkham, 16). Leaf-cutting ants in Louisiana excavate soils for the construction of belowground chambers in which they grow fungi on the harvested plant material. Photo courtesy of iStock/Global P. I present below what are, for me, a new cache of seductive details in soil science, with the hope that others will add to them and provide a pool of “stories untold” for classroom, outreach, and other efforts. The story of Selman Waksman and the production of streptomycin by soil actinomycetes in the 1940s is well known. The search for such compounds during this era was based on culturing methods. Over the last two decades, molecular methods have greatly expanded our ability to screen the biological pool within the soil for natural products of use to humans as biocatalysts of industrial interest such as amylases, lipases, and proteases and as bioactive compounds such as drugs and insecticides. With a 30-g soil sample now known to contain more than 500,000 species, soil still represents a largely untapped resource for useful microorganisms (Daniel, 7). Examples of soil-derived natural products from the earlier era include spinosad, a metabolite produced by the actinomycete Saccharopolyspora, which has been shown to be effective against mosquitoes and other insects (Jiang and Mulla, 13). This microorganism was isolated from soil collected in 1982 at an abandoned rum distillery at a sugar mill in the Virgin Islands by a vacationing chemist from the Natural Products Research Group at the Eli Lilly pharmaceutical company (Mertz and Yao, 21; Thompson et al., 36). Coumarins are a class of compounds of widespread occurrence in vascular plants (Neish, 26), and hence, in plant residues in soil. They are responsible for the sweet smell of freshly mowed hay, and synthetic coumarin has been used in perfumes, including Jicky, created in Paris in 1889 (Museum of Arts and Design, 24). Consumption of moldy silage made from sweet clover that has spoiled during storage has been found to produce sometimes fatal bleeding in cattle. The “hemorrhagic factor” responsible for such cases was found to be a substance produced by the degradation by the fungi of the genus Aspergillus, whose primary ecological niche is soil or decaying vegetation (Dagenais and Keller, 6). It is the conversion of the abundant coumarin in the clover to a mycotoxin known as dicoumarol that inhibits coagulation in cattle feeding on it. This same conversion to dicoumarol also occurs as plant residues decompose in the soil, and with its accumulation in soil microenvironments, some toxicity to native bacteria may occur (Smyk and Van, 32). Selman Waksman. Source: Wikipedia. Warfarin is a synthetic derivative of dicoumarol that is widely used today as an anticoagulant in human medicine (best known by the brand name Coumadin) and as a rodenticide. Besides this scientific linkage of soil science to human health, there is also a fiscal linkage. The research that led to the development of warfarin was funded by the Wisconsin Alumni Research Foundation (WARF). The name “warfarin” was derived from WARF, plus the “arin” from coumarin (Pirmohamed, 30). WARF funded the Ph.D. thesis work of my colleague and officemate Del Fanning (personal communication), and undoubtedly that of other University of Wisconsin soil science graduates. Not all of those who study soil science make it their career home. But the skills acquired with soil science training can certainly have carry-over value to other fields; such was the case for three major figures in 20th century science: Vladimir Vernadsky (1863–1945), the acknowledged founder of biogeochemistry, is often claimed by ecologists and geologists as one of their own. But Vernadsky was mentored by Dokuchaev at Saint Petersburg University during his student years (1881–1885) and later research; his intellectual lineage to soil science is clear. Dokuchaev's integrative and interdisciplinary approach to science in general and his view of the importance of organisms in the creation of soils were guiding principles in the development of Vernadsky's concept of the biosphere (Bailes, 2; Ackert, 1; Guegamian 9; Ivan Vtorov, personal communication). Rene Dubos (1901–1982) was born in France and gained international fame as a medical scientist at the Rockefeller Institute in New York City and as an environmental activist; he coined the iconic phrase “Think globally, act locally” (Kingsland, 15). Soon after graduating from the Institut National Agronomique, he began work as a technical editor at the International Institute of Agriculture (IIA; the forerunner of the Food and Agriculture Organization of the United Nations) in Rome. The IIA hosted the founding meeting of the International Society of Soil Science (now International Union of Soil Sciences) in May 1924, and here he met soil scientists Jacob Lipman and Selman Waksman from Rutgers University. The visit spurred him to study bacteriology over the summer and to take on outside translating work in order to earn money for a trip to America. With apparently no firm plans upon departure, he happened to be on the same ship as Waksman, who was returning from Europe in September 1924. Waksman offered him a position at Rutgers and escorted him there upon arrival in New York. Dubos obtained his Ph.D. under Waksman in 1927 for research on the decomposition of cellulose (Note: Hans Jenny was a post-doc with Waksman in 1926–1927—now that was a laboratory lineup!) Vladimir Vernadsky. Source: Wikipedia. Dubos’ work soon shifted from the New Jersey Agricultural Experiment Station to Rockefeller Hospital in New York City, and he was tasked with seeking a cure for bacterial pneumonia. The capsule surrounding the pneumococcus was, like cellulose, a polysaccharide. Using the soil enrichments from a New Jersey cranberry bog, Dubos isolated an enzyme that destroyed the capsule and rendered the pathogen susceptible to phagocytosis by white blood cells (Moberg, 22; Moberg and Cohn, 23). In preparation for a 2010 Earth Day presentation on soils at the Arlington Arts Center in Virginia, I thought about showing the browning reaction—the enzymatic formation of quinones from phenols in fruit such as apples when cut and exposed to air; the quinones polymerize to melanins, a brown pigment. My idea was to then use this browning of a cut apple as a demonstration and an analog to organic matter transformation that occur in the soil. Using “soil science” and “browning” as search terms, I inadvertently came across a memoir by Earl Reece Stadtman (1919–2008), a noted biochemist at the National Institutes of Health, entitled Sixty Years of Research: From Soil Science and the Browning of Dried Apricots to the Biochemistry of Metabolism.” Stadtman graduated from high school in San Bernardino, CA in 1937 and enrolled at the local junior college, hoping to learn the basic science required to set up a soil testing lab (Park, 28). He soon realized that more training was needed and transferred to the University of California at Berkeley, where he earned a B.S. in soil science in 1942: “… this proved to be a rewarding experience because the soil science curriculum included courses in organic, inorganic, and analytical chemistry, physics, bacteriology, human and plant physiology, plant nutrition, soil physics, colloidal chemistry, agronomy, and soil microbiology. The latter course proved critical to my scientific development” (Stadtman, 34, p. 625). The soil microbiology course was taught by biochemist and microbiologist Horace A. Barker; Stadtman's wartime work with Barker on the rapid browning spoilage of dried apricots sent to troops in the South Pacific initiated Stadtman's career shift from soil science to a lifetime of work in enzymology. He was awarded the National Medal of Science in 1979 by President Jimmy Carter and mentored two physicians at the National Institutes of Health who went on to win Nobel Prizes (Goldstein and Brown, 8). Joseph Needham was a biochemist by training but is best known today as the founding author/ encyclopedist of the series Science and Civilisation in China (SCC; 1954–2008). The genius of Needham has been chronicled by popular author Simon Winchester in his 2008 book The Man Who Loved China: The Fantastic Story of the Eccentric Scientist Who Unlocked the Mysteries of the Middle Kingdom. In the volume of SCC focused on botany, Needham goes into considerable detail on the soil forming processes and the geographic distribution of soils in China. Describing podsolization and the translocation of iron and organic matter, Needham's roots in biochemistry and his powers of synthesis come through in a footnote: “Perhaps the method of chromatographic analysis, which has so greatly revolutionised modern biochemistry by making it possible to separate and identify organic chemical compounds, whether pigments or not, in extremely small quantities, adsorbing them differently on columns of solid substances in powder or granular form, or upon strips of filter paper, and then eluting (eluviating) them with different solvents … was one of the greatest indirect contributions of soil science. In view of the outstanding position of Russian scientists in the development of modern pedology, it may be no coincidence that the central figure in chromatographic history was also a Russian, Michael Simeonovitch Tswett (1872–1920)” (Needham, 25, p. 69). Was the botanist M.S. Tswett (Livengood, 19; Tswett's death date is now generally given as 1919) acquainted with and possibly influenced by the earlier soils studies of Dokuchaev and/or his students? Did he see soil profiles as analogs for the laboratory columns that he set up around 1901 for the separation of plant pigments? Expert opinion does not support Needham's speculation (Jonathan Livengood and Ivan Vtorov, personal communications), but it is, nevertheless, thought provoking and can be used to introduce the concept of historical context when considering the path of scientific discovery. The discussion above has focused on text material. But images can also provide powerful seductive details. Such imagery may derive directly from science—for example, the snowflake photomicrographs of Wilson Bentley and Alexander von Humboldt's artistic use of vertical exaggeration in depictions of the biogeography of equatorial plants (Barrow, 4). Morphed images, only loosely tied to scientific reality, such as the Man in the Moon in the 1902 French silent film A Trip to the Moon by Georges Méliès, can also excite the imagination and be sparks for discussion and dialogue. Soil science is rich in captivating imagery—see, for example, the wonderfully illustrated European Atlas of Soil Biodiversity (EASB; Jeffrey, 12), with its micrographs of rock-eating mycorrhiza, mycogenic oxalate minerals (EASB, p. 38-39), and parasitic and carnivorous fungi (EASB, p. 43 and 94). One can rightly be in awe of charismatic megafauna (whales, eagles, elephants, etc.), but claw-legged tardigrades—a new group of soil invertebrates for me (EASB, p. 100)—have both shock value and universal appeal for all ages—a charismatic, microfaunal soil superstar! Soil pore architecture and root distributions being explored with new methods and devices adapted from engineering and medicine (including borescopes and laparoscopic samplers) and advanced, three-dimensional tomographic imaging techniques offer new opportunities to engage audiences. Snowflake photomicrograph of Wilson Bentley, 1890. Source: Wikipedia. Most of us have had this experience. You are at a party and somebody asks what you do. You respond “I'm a soil scientist”; they look confused and ask “social scientist?” Well, saying “pedologist” may not be any safer. At our neighboring university, Bowie State, the use of “pedology” in the curriculum comes from an alternative definition, taken from the medical dictionary, meaning the scientific study of the life and development of children (http://www.merriam-webster.com/dictionary/pedology). Thus, Bowie State University has courses such as Pedology 250: Child and Family Life Skills Development. And at my alma mater, the University of Minnesota, the College of Homeopathic Medicine and Surgery's second year students in the 1887–1888 academic year studied “Paedology”—what today would be termed “Pediatrics”—the diseases of children (Wilson, 38, p. 57). Tardigrade (“water bear”), Hypsibius dujardini; scanning electron micrograph by Bob Goldstein and Vicky Madden, University of North Carolina–Chapel Hill; http://tardigrades.bio.unc.edu/. Having come to soil science from geology in 1970, at the time of the wonderfully mysterious-sounding “7th Approximation,” I knew that soil classification was a complex and evolving scientific endeavor. But an earlier iteration escaped my attention until recently. It came from Cyril Hopkins and a colleague at the University of Illinois in 1908 and employed a variation on the Dewey Decimal System, familiar in library usage, in the classification of soils. The soils of Illinois were divided into 14 great soil areas based upon age or general method of formation; these were assigned numbers in increments of a hundred, from 100 to 1,400. Within each of these units, the soils were assigned to general groups based upon texture, then subdivided into individual soil types based upon color and stratification, with special consideration of peats and mucks. Numerical values at this level ranged from 0 to 99 (with decimals employed as needed for further distinctions) and were attached to the higher-level classification. Thus, a brown silt loam on gravel (26.4), developed in an unglaciated area of Illinois (100), would be designated as 126.4 (Hopkins and Pettit, 11). As Hopkins was a bitter enemy of USDA Bureau of Soils Chief Milton Whitney (Landa, 18), any hope for this Illinois system making it to the national stage was dead on arrival. In the broadest sense, we can consider any account of scientific results to be a story, and indeed, storytelling has a long tradition in the sciences (McCloskey, 20; Phillips, 29). “Surprise stories with unexpected emergences” are just part of that spectrum (Karasti et al., 14). What to tell? This is an area where our instincts are our best guides. If it surprised, entertained, and informed us, it is likely going to do the same for our audience. And how much? There can be too much of a good thing, and we are warned that seductive details can be diverting: “… such anecdotes may indeed attain the desired level of increasing motivation, but they pose a risk if precious attentional resources flow to processing the motivating information and away from the conceptually central information… a phenomenon known as the ‘seductive detail’ effect. This undesired effect can be diminished by limiting and demarcating anecdotes” (van den Broek, 37, p. 455). Again, our instincts are likely our best guides as to when and where to place such stories. Among our colleagues—from students and early career soil scientists to established workers and emeriti—are undoubtedly some gifted storytellers. We need only look to our neighbors in plant pathology for a role model in E.C. (Ernest Charles) Large (1902–1976). His 1940 book The Advance of the Fungi, a history of plant pathology written with “a tone of fiction” for a mass audience, was reprinted on at least three occasions over two decades. This was preceded by a highly imaginative science fiction novel, Sugar in the Air (1936). Large summarized its central storyline as “transmuting the manufacture of colloidal fungicides into that of making carbohydrates from water and carbon dioxide from the chimneys of power stations.” The book was a best seller in the U.K. (Bailey and Kinross 3). Nine decades later, when we are reading about making plastics from air-bound methane emissions from energy facilities (http://www.newlight.com), Sugar in the Air shows the power of scientific imagination and its ability to stimulate dialog about issues in science, technology, and the environment. Sugar in the Air was published by Jonathan Cape (now part of Random House); they published books by Ernest Hemingway [including A Farewell to Arms (1929)] and Sinclair Lewis [including Elmer Gantry (1927)]. Large mingled with the likes of George Orwell, T.S. Elliot, and Pamela Travers (author of Mary Poppins and made famous to modern audiences in the film Saving Mr. Banks), as well the rank and file of the British Mycological Society (Colhoun, 5; Bailey and Kinross, 3). Who will be the E.C. Large of soil science? Soils touch virtually all aspects of the human experience, and we have stories in our heads, hearts, and back pockets that can hook individuals out there. On a daily basis, we are privileged to explore and experience what C.C. Nikiforoff (27) called the “excited skin” of the earth. Let's share the excitement. Sincere thanks to: Jonathan Livengood, Department of Philosophy, University of Illinois, and Ivan Vtorov, Department for the History of Geology, Vernadsky State Geological Museum, Russian Academy of Sciences for discussions on the work of Vernadsky, Tswett and Dokuchaev.