Biopedoturbation

by

David R. Butler, Rachel M. Cavin

• LAST REVIEWED: 13 January 2014
• LAST MODIFIED: 13 January 2014
• DOI: 10.1093/obo/9780199874002-0077

Introduction

Biopedoturbation (spelled “biopedturbation” in British, Canadian, and Australian publications) is soil mixing by biological means (i.e., by animals, plants, and humans). Pedoturbation (or “pedturbation”), the mixing of soils, encompasses all forms of biopedoturbation as well as mixing by air, water, shrinking and swelling of clays, freeze-thaw activity, crystal growth, mass movements, extraterrestrial impacts, and earthquakes. Under the broad umbrella of biopedoturbation, “faunalturbation” (also known as “faunalpedoturbation” or “faunalpedturbation”) is the study of soil mixing by animals. Faunalturbation has been widely studied by geographers, compared to the number of geographic studies examining soil mixing by plants, or “floralturbation” (also known as “floralpedoturbation” or “floralpedturbation”). Human mixing of soils, broadly studied in agriculture and pedology as well as in geography, has been referred to as “anthroturbation” (or “anthropedoturbation,” “anthropedturbation”). Biopedoturbation studies are not restricted to geography, where they typically occur within the fields of soils geography and in biogeomorphology, but are also common in pedology and in the ecological subdiscipline of ecosystem engineering. With the increasing focus of geomorphologists on fine-scale process studies and measurements since the 1970s, studies of biopedoturbation have increased dramatically. However, classic studies of biopedoturbation can be traced back to the last published work by Charles Darwin in the late 1800s, who spent his final years meticulously documenting the soil-mixing effects of earthworms. With the emergence of the subdiscipline of zoogeomorphology in the 1990s within geomorphology, many studies of zoogeomorphic effects on landscapes can be considered to fall under the broad rubric of biopedoturbation. Examples include churning of soil by burrowing animals such as gophers and moles, wallowing actions of animals, trampling and chiseling of soils by animal hooves, and digging for food. Floralpedoturbation is primarily accomplished by tree uprooting, although root growth through soils also accomplishes soil mixing. Anthropedoturbation includes all forms of soil mixing by humans, including agricultural activities, and has been invoked by some authors as a primary indicator of the onset of the Anthropocene epoch.

General Overviews

Scientific studies of biopedoturbation can be traced back to Charles Darwin’s final work (Meysman, et al. 2006), where the burrowing effects of earthworms were subjected to intensive, systematic examination. Biopedoturbation played a key role in the expansion of life on Earth in the Cambrian through burrowing and searching for food in seafloor sediments. The various forms of biopedoturbation were first explicitly defined in Hole 1961, with expansion of terminology provided in Johnson, et al. 1987. Hole 1961 first used the terms “floralturbation” and “faunalturbation,” which collectively were referred to as bioturbation. Biopedoturbational activities of burrowing for food and shelter, trampling and wallowing, mound building, and food caching were examined in detail in Butler 1995, which remains, to date (in 2013), the only book exclusively devoted to the zoogeomorphological effects of animals. Excellent and in-depth examinations both of floralturbation and faunalturbation are provided in the landmark Schaetzl and Anderson 2005, which also includes an expansion on the terms “proisotropic pedoturbation” and “proanisotropic pedoturbation” introduced in Johnson, et al. 1987. Proisotropic pedoturbation encompasses processes that tend toward soil randomness and disorder, disrupting, blending, or destroying soil horizons and causing morphologically simplified soil profiles to form from more-ordered ones. Proanisotropic pedoturbation by plants and animals includes processes that aid or lead to the formation and maintenance of soil horizons or layers and cause an overall increase in soil profile order. Both Gabet, et al. 2003 and Wilkinson, et al. 2009 offer valuable literature reviews and overviews of bioturbation. Gabet, et al. 2003 focuses more strongly on floralturbation via root growth and tree throw, with a more cursory examination of faunalturbation. Wilkinson, et al. 2009 provides a more balanced review that also presents numerous quantitative estimates of the effects of bioturbation, drawn from the literature. A more recent volume, Horwath Burnham and Johnson 2012, focuses exclusively on the unusual landforms known as Mima mounds, believed by many to form from biopedoturbation of burrowing animals, especially gophers. The introductory chapter in that volume provides a particularly insightful overview of the concepts, definitions, and principles of soil mound studies. Numerous color photographs and diagrams, and a map of the distribution of Mima mounds in western North America, make this introductory chapter and the entire volume exceptionally helpful in understanding the Mima mound controversy and the role of biopedoturbation in their origin. In 2013, the volume received the Association of American Geographers’ G. K. Gilbert Award for Excellence in Geomorphological Research, an honor that is well deserved.

• Butler, David R. Zoogeomorphology: Animals as Geomorphic Agents. Cambridge, UK: Cambridge University Press, 1995.

  DOI: 10.1017/CBO9780511529900

  The only book exclusively focused on the geomorphic impacts of animals, including biopedoturbation. Individual chapters examine biopedoturbational activities of trampling and wallowing, mound building, digging for and caching of food, and burrowing and denning. Extensive bibliography covering period prior to 1995. Recipient of Association of American Geographers’ G. K. Gilbert Award in 1998.

• Gabet, Emmanuel J., O. J. Reichman, and Eric W. Seabloom. “The Effects of Bioturbation on Soil Processes and Sediment Transport.” Annual Review of Earth and Planetary Sciences 31 (2003): 249–273.

  DOI: 10.1146/annurev.earth.31.100901.141314

  Thorough review, especially of the two primary forms of floralturbation—root growth and tree throw. Examination of bioturbation by animals is more cursory, focusing on earthworms, ants and termites, and gophers and a discussion of Mima mounds. Completely ignores widespread burrowing effects of, for example, colonial seabirds and burrowing reptiles.

• Hole, Francis D. “A Classification of Pedoturbations and Some Other Processes and Factors of Soil Formation in Relation to Isotropism and Anisotropism.” Soil Science 91.6 (1961): 375–377.

  DOI: 10.1097/00010694-196106000-00005

  Landmark paper that developed the concept of two groups of pedoturbation processes: those that cause a soil to trend toward disorder or randomness (isotropism) and those that trend toward order, sorting, and a nonrandom nature (anisotropism). Identified nine major forms of pedoturbation, including two forms of bioturbation (faunalpedoturbation and floralpedoturbation).

• Horwath Burnham, Jennifer L., and Donald L. Johnson, eds. Mima Mounds: The Case for Polygenesis and Bioturbation. Boulder, CO: Geological Society of America, 2012.

  Originating from a Geological Society of America Symposium in 2008, the editors collected papers providing a comprehensive overview of the controversy associated with Mima mounds, roughly circular, lens-shaped landforms frequently attributed to bioturbation. Volume contains a superb introduction, six overview or site-specific papers, and six useful appendices covering the diverse literature of Mima mounds.

• Johnson, Donald L., Donna Watson-Stegner, Diana N. Johnson, and Randall J. Schaetzl. “Proisotropic and Proanisotropic Processes of Pedoturbation.” Soil Science 143.4 (1987): 278–292.

  DOI: 10.1097/00010694-198704000-00005

  Following the definitions in Hole 1961, the authors provide hypothetic and real examples of how faunalturbation and floralturbation mixing processes, as well as non-bioturbation mixing, affect soil profiles. Both the form of pedoturbation and the texture of the parent material are critical in determining if a soil expresses order or disorder.

• Meysman, Filip J. R., Jack J. Middelburg, and Carlo H. R. Heip. “Bioturbation: A Fresh Look at Darwin’s Last Idea.” Trends in Ecology & Evolution 21.12 (2006): 688–695.

  DOI: 10.1016/j.tree.2006.08.002

  Brief but important review of the nature of bioturbation. Demonstrates how bioturbation is an important form of ecological engineering in modern ecological theory. Also focuses on the evolutionary perspective, illustrating how bioturbation, via burrowing and searching for food in seafloor sediments, played a key role in the Cambrian explosion of life.

• Schaetzl, Randall J., and Sharon Anderson. Soils: Genesis and Geomorphology. Cambridge, UK: Cambridge University Press, 2005.

  DOI: 10.1017/CBO9780511815560

  Mammoth (817 pages) examination of all aspects of soil characteristics, genesis, and geomorphology. Contains full fifty-plus-page chapter on pedoturbation. Follows the work in Hole 1961 and Johnson, et al. 1967 in categorizing pedoturbation into proisotropic and proanisotropic forms. Both faunalturbation (mixing by animals) and floralturbation (by plants) are given thorough examination.

• Wilkinson, Marshall T., Paul J. Richards, and Geoff S. Humphreys. “Breaking Ground: Pedological, Geological, and Ecological Implications of Soil Bioturbation.” Earth-Science Reviews 97.1–4 (2009): 257–272.

  DOI: 10.1016/j.earscirev.2009.09.005

  Excellent review of the effects of bioturbation, going back to works by Darwin and Nathaniel Shaler in the late 19th century. Primary effects of bioturbation are shown to be soil production from saprolite, formation of surface mounds, soil burial, and downslope sediment transport. Presents quantitative rates from the literature.