Pedodiversity

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Pedodiversity can be generally defined as the variation of soil properties (usually characterised by soil classes) within an area.

Pedodiversity studies were first started by analyzing soil series–area relationships (Beckett and Bie, 1978). According to Guo et al (2003) the term pedodiversity was developed by McBratney (1992) who discussed landscape preservation strategies based on pedodiversity. Recently, examinations of pedodiversity using indices commonly used to characterize bio-diversity have been made

(Ibánez et al., 1995). Ibáñez et al. (1995) first introduced ecological diversity indices as measures of pedodiversity. They include Species richness, abundance, and Shannon index. Richness is the number of different soil types, which is the number of soil classes at particular level in a taxonomic system. Abundance is defined as the distribution of the number of soil individuals.

Just as biologists and ecologists talk about biodiversity, geologists on geodiversity, soil scientists can talk about pedodiversity. Pedodiversity has some overlap with biodiversity as soil contains organisms. Pedodiversity is a measure of soil variation, and pedodiversity is a function of soil formation.

Pedodiversity can be thought as a way to preserve, or even reconstruct, the soil cover. Just as biologists argue that organisms need to be maintained, soil scientists can argue that preserving soil will maintain organisms as well as other unique soil materials equally crucial in insuring our future wellbeing. In areas which have been degraded it will become important to reconstruct the variation. A quantitative knowledge of natural pedodiversity will ease the task of the person who attempts to rebuild quasi-natural soil systems.

Soil scientists have pragmatically adapted the concept of biodiversity and used diversity index such as Shannon index using taxa from well-accepted international soil classification systems.

Jonathan Phillips showed that in eastern North Carolina intrinsic variability within homogeneous landscape units is more important in determining the total pedodiversity of the study area than is the extrinsic variability associated with measurable differences in topography, parent material, and vegetation/land use. In another study, they found that soils in Ouachita Mountains of Arkansas vary considerably within small more-or-less homogeneous areas, and richness–area analysis shows that the overall pattern of pedodiversity is dominated by local, intrinsic (within-plot) variability as opposed to between-plot variability. This is consistent with variation controlled mainly by individual trees and local lithological variations. Given the criteria used to distinguish among soil types, biomechanical as opposed to chemical and hydrological effects of trees are indicated. Results also suggest divergent evolution whereby the pedologic effects of trees are large and long-lived relative to the magnitude of the initial effects and lifespan of the plants.


Guo et al recently explored quantitative aspects of pedodiversity for the USA based on the State Soil Geographic database (STATSGO). They found that the West USDA-NRCS geographical region has the highest soil taxa richness, followed by the Northern Plains. The South Central region has the highest taxa evenness, while taxa evenness in the West region is the lowest. The West or the South Central regions have the highest overall soil diversity in the four highest taxonomic categories, while the West or Northern Plains regions have the highest diversity in the two lowest taxonomic levels. The high diversity index in the West region results from high taxa richness while the high diversity index in the South Central region results from an evenness of taxa. As the taxonomic level decreases, the pattern of taxa abundance approaches a lognormal distribution. One of the key findings of this research is that at lower levels of soil taxonomic divisions (especially the series level), soil taxa increase continuously with increasing area, indicating considerable soil endemism in the USA (and likely around the world), a key consideration in conservation and preservation planning.

However conventional diversity measures, only measure the relative abundance of soil classes, and there is no information on the taxonomic similarity or differences between soil classes. New measures of pedodiversity, such as the mean soil taxonomic distance, which considers both information on the relative abundance and the taxonomic differences between soil classes have been developed and shown to be a better measure.

[edit] References

  • Beckett, P.H.T., Bie, S.W., 1978. Use of soil and land-system maps to provide soil information in Australia. Division of soils technical paper, vol. 33. Commonwealth Scientific and Industrial Research Organization, Australia.
  • Guo, Y, Gong, P, Amundson, R., 2003. Pedodiversity in the United States of America. Geoderma 117 (2003) 99–115. [1]
  • McBratney, A.B., 1992. On variation, uncertainty and informatics in environmental soil management. Australian Journal of Soil Research 30, 913–935.
  • McBratney, A.B., Minasny, B., 2007. On measuring pedodiversity. Geoderma 141,149-154. doi:10.1016/j.geoderma.2007.05.012
  • Ibáñez, J.J., De-Alba, S., Bermúdez, F.F., García-Álvarez, A., 1995. Pedodiversity: concepts and measures. Catena 24, 215-232.
  • Jonathan D. Phillips (2001) The Relative Importance of Intrinsic and Extrinsic Factors in Pedodiversity. Annals of the Association of American Geographers 91 (4), 609–621.
  • Jonathan D. Phillips, and Daniel A. Marion (2005) Biomechanical effects, lithological variations, and local pedodiversity in some forest soils of Arkansas Geoderma Volume 124, Issues 1-2, January 2005, Pages 73-89.
  • Robin Thwaites, Brian Slater. 2004. The concept of pedodiversity and its application in diverse geoecological systems.

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