Soil Disturbance by Animals: Soil Genesis and Patch Dynamics
Investigators (most current known information)
Studies of the abundance and diversity of soil disturbance by animals on a topoclimatic gradient in Israel and on degraded (desertified) and relatively undegraded ecosystems in the Chihuahuan and Sonoran Deserts of North America have yielded a number of generalizations about landscape patterns of soil disturbance and the functional role of soil disturbances in arid environments. Both the area and volume of soil disturbed by animals varied with rainfall of the previous winter rain season in the Judean Desert. Soil transported to the surface by ants in the construction of nests accounted for most of the soil movement and the aggregate stability of that soil was lower than undisturbed soil. In the Judean Desert of Israel, soil turnover by ants is an important aspect of pedogenesis.
In the Chihuahuan Desert of North America, the area and volume of soil disturbed by animals was greater in relatively undisturbed grassland than in mesquite coppice dunes on the same soil type. In Chihuahuan Desert landscape units on fine-textured soils at the base of watersheds, there were no significant differences in volume and area of soil disturbance by animals in desertified and undegraded landscape patches. Foraging pits produced by small mammals are concentrated under the canopy of vegetation. There is a higher rate of germination and establishment of herbaceous species in soil disturbances than in undisturbed soil. In areas with find textured soils, soil disturbance pits and digs exhibit higher rates of infiltration than undisturbed soil. Accumulation of organic debris and seeds in animal produced depressions may attract subterranean termites that produce macropores that drain the depressions (M.S. Thesis - Aaron Killgore).
One aspect of continuing process of desertification is the spread of an alien grass species, Lehmann's lovegrass (Eragrostis lehmanniana) in Arizona and New Mexico. The abundance and diversity of animal produced soil disturbances was significantly lower in Lehmann's lovegrass dominated areas compared to native grassland in close geographic proximity on the Santa Rita Experimental Range south of Tucson Arizona. However on the Jornada Experimental Range there were no significant differences in abundance and diversity of biopedturbation in Lehmann's lovegrass dominated patches and adjacent native grassland It was concluded that the Lehmann's lovegrass must be a dominant from several decades before there are significant reductions in the fauna that are responsible for biopedturbation (Kulas et al., In Press).
Pocket gophers (Geomyidae) are patchily distributed in arid ecosystems. In mesic grasslands, pocket gophers create nutrient rich patches and contribute to plant biodiversity. We (Kerley et. Al., 2003) studied the geographic distribution and functional role of pocket gopher mounds in Chihuahuan and Sonoran Desert grasslands. In the Chihuahuan Desert grasslands, pocket gopher mounds had lower bulk density, higher nitrate, and higher annual plant cover than undisturbed soils. In the Sonoran Desert there were no differences in these parameters between pocket gopher mounds and undisturbed soil. We concluded that the effects of pocket gopher burrowing on soils and vegetation are dependent upon the properties of the undisturbed soils.
The hypothesis that abundance and diversity of biopedturbation on piosphere (decreasing rings of impact by livestock centered on water points) was not supported by data. There were no significant differences in abundance of soil disturbances, volume of soil moved and/or area of soil disturbed by animals on the piosopheres studied. The primary impact of biopedturbation on piospheres is the readily eroded materials ejected by animals in nest construction or from foragina pits (Callan et al., 2003).
Articles in Journals
Kulas, C.M. and W.G. Whitford. 2003. "The effect of Lehmann lovegrass (eragrostis lehmannian) on semiarid
ecosystems of southwestern North America: Faunalpedturbation as an ecosystem indicator." Journal of Arid Environments (in press).
Killgore, A., W.G. Whitford and E. Jackson. 2003. "Fire in a Chihuahuan Desert grassland: Effects on plant community composition and recovery, small mammal populations and patterns of biopedturbation." (in review).
Steinberger, Y. and W.G. Whitford. 2003. "Faunalpedturbation on a topoclimatic gradient in Israel." Journal of Arid Environments (in review).
Kerley, G.I.H., W.G. Whitford and F.R. Kay. 2003. "Effects of pocket gophers on soils and vegetation in the Chihuahuan and Sonoran Deserts." Journal of Arid Environments (in press).
Callan, R., E. Jackson, A. Killgore and W.G. Whitford. 2003. "Patterns of biopedturbation on piospheres in a Chihuahuan Desert grassland." Journal of Arid Environments.
Whitford, W.G. 2003. "The functional significance of cemented nest caps of the harvester ant, Pogonomyrmex maricopa." Journal of Arid Environments 53:281-284.
Roth, Gur. The role of animals in desertification herbivory patterns, processes and consequences in degraded ecosystems. M.S. Thesis. Bar-Ilan University. Israel.
Roth, G.A., W. G. Whitford and Y. Steinberger. 2003. "The role of animals in landscape shaping in desertified ecosystems." Presented, Zoological Society of Israel 40th annual meeting, December. Sede Boker, Israel.
Roth, G.A., W. G. Whitford and Y. Steinberger. 2004. "The role of animals in desertification herbivory patterns in degraded grassland." Presented, Ecological Society of America 89th annual meeting, August. Portland OR.
Roth, G.A., W.G. Whitford and Y. Steinberger. 2004. "The role of animals in desertification herbivore-induced vegetation change." Presented, Wildlife Society 9th annual meeting, September. Calgary, Alberta, Canada.
Roth, G.A., W. G. Whitford and Y. Steinberger. 2004. "Desertification in historical perspective of man and other ecosystem engineers in the arid Southwestern USA." Presented, Ecological Society of Israel 41st annual meeting, December. Haifa, Israel.
Mathis, V. L., W.G. Whitford, F.R. Kay and P.U. Alkon. 2004. "Effects of grazing and shrub removal on small mammal populations in southern New Mexico." Presented, Sixth symposium on resources of the Chihuahuan Desert region, October. Alpine TX.
Killgore, A., E. Jackson and W.G. Whitford. 2004. "Fire in Chihuahuan Desert grassland effects on vegetation, small mammal populations and biopedoturbation." Presented, Sixth symposium on resources of the Chihuahuan Desert region, October. Alpine TX.
Duval, B., E. Jackson W.G. Whitford. 2004. "Mesquite (Prosopis glandulosa) germination and survival in black-grama (Bouteloua eriopoda) grassland relations between microsite and Heteromyid rodent (Dipodomys spp.) impact on establishment." Presented, Sixth symposium on resources of the Chihuahuan Desert region, October. Alpine TX.