Implications of Longer Term Grazing Rest in the Sagebrush Steppe

Kirk W. Davies, Martin Vavra, Brad W. Schultz, Neil R. Rimbey

Abstract


Longer term grazing rest has occurred or been proposed in large portions of the sagebrush steppe based on the assumption that it will improve ecosystem properties. However, information regarding the influence of longer term rest from grazing is limited and has not been summarized. We synthesized the scientific literature on long-term rest in the sagebrush steppe to evaluate the potential ecosystem effects and identify factors that influence those effects. Longer term rest is clearly advantageous compared to detrimental grazing practices (i.e., repeated defoliation during the growing season without periodic deferment or short-term rest). Changing grazing management from detrimental use to modern recommended grazing practices or dormant season use will likely convey the same benefits as long-term grazing rest in most situations. In general, long-term rest and modern properly managed grazing produce few significant differences. However, some topic areas have not been adequately studied to accurately predict the influence of long-term rest compared to managed grazing. In some situations, long-term rest may cause negative ecological effects. Not grazing can cause an accumulation of fine fuels that increase fire risk and severity and, subsequently, the probability of sagebrush steppe rangelands converting to exotic annual grasslands. One common theme we found was that shifts in plant communities (i.e., exotic annual grass invasion and western juniper encroachment), caused in part from historical improper grazing, cannot be reversed by long-term rest. This synthesis suggests that land managers should carefully consider if long-term rest will actually achieve their management goals and if a change in grazing management would achieve similar results


Keywords


dormant season grazing; exclosures; grazing interactions; herbivory; proper management;

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References


Anderson, E. W., & Scherzinger, R. J. (1975). Improving quality of winter forage for elk by cattle grazing. Journal of Range Management, 28(2), 120-125. doi:10.2307/3897442

Anderson, J. E., & Holte, K. E. (1981). Vegetation development over 25 years without grazing on sagebrush-dominated rangeland in southeastern Idaho. Journal of Range Management, 34(1), 25-29. doi:10.2307/3898446

Anderson, J. E., & Inouye, R. S. (2001). Landscape-scale changes in plant species abundance and biodiversity of a sagebrush steppe over 45 years. Ecological Monographs, 71(4), 531-556. doi:10.1890/0012-9615(2001)071[0531:LSCIPS]2.0.CO;2

Austin, D. D., & Urness, P. J. (1998). Vegetal change on a northern Utah foothill range in the absence of livestock grazing between 1948 and 1982. Western North American Naturalist, 58(2), 188-191.

Baker, W. L. (2006). Fire and restoration of sagebrush ecosystems. Wildlife Society Bulletin, 34(1), 177-185. doi:10.2193/0091-7648(2006)34[177:FAROSE]2.0.CO;2

Balch, J. K., Bradley, B. A., D'Antonio, C. M., & Gómez‐Dans, J. (2013). Introduced annual grass increases regional fire activity across the arid western USA (1980–2009). Global Change Biology, 19(1), 173-183. doi:10.1111/gcb.12046

Bates, J. D., Miller, R. F., & Svejcar, T. (2005). Long-term successional trends following western juniper cutting. Rangeland Ecology & Management, 58(5), 533-541. doi:10.2111/1551-5028(2005)58[533:LSTFWJ]2.0.CO;2

Blackmore, M., & Vitousek, P. M. (2000). Cattle grazing, forest loss, and fuel loading in a dry forest ecosystem at Pu'u Wa'aWa'a Ranch, Hawai'i. Biotropica, 32(4a), 625-632. doi:10.1111/j.1744-7429.2000.tb00509.x

Beschta, R. L., Donahue, D. L., DellaSala, D. A., Rhodes, J. J., Karr, J. R., O’Brien, M. H., Fleischner, T. L., & Williams, C. D. (2013). Adapting to climate change on western public lands: Addressing the ecological effects of domestic, wild, and feral ungulates. Environmental Management, 51(2), 474-491. doi:10.1007/s00267-012-9964-9

Borman, M. M. (2005). Forest stand dynamics and livestock grazing in historical context. Conservation Biology, 19(5), 1658-1662. doi:10.1111/j.1523-1739.2005.00115.x

Boyd, C. S., & Svejcar, T. J. (2011). The influence of plant removal on succession in Wyoming big sagebrush. Journal of Arid Environments, 75(8), 734-741. doi:10.1016/j.jaridenv.2011.03.008

Bradstock, R. A., & Gill, A. M. (1993). Fire in semiarid, mallee shrublands-size of flames from discrete fuel arrays and their role in the spread of fire. International Journal of Wildland Fire, 3(1), 3-12. doi:10.1071/WF9930003

Briggs, J. M., Hoch, G. A., & Johnson, L. C. (2002). Assessing the rate, mechanisms, and consequences of the conversion of tallgrass prairie to Juniperus virginiana forest. Ecosystems, 5(6), 578-586. doi:10.1007/s10021-002-0187-4

Brown, J. H., & McDonald, W. (1995). Livestock grazing and conservation on southwestern rangelands. Conservation Biology, 9(6), 1644-1647. doi:10.1046/j.1523-1739.1995.09061644.x

Brussard, P. F., Murphy, D. D., & Tracy, C. R. (1994). Cattle and conservation biology--another view. Conservation Biology, 8(4), 919-921. doi:10.1046/j.1523-1739.1994.08040919.x

Burkhardt, J. W., & Tisdale, E. W. (1969). Nature and successional status of western juniper vegetation in Idaho. Journal of Range Management, 22(4), 264-270. doi:10.2307/3895930

Caldwell, M. M. (1984). Plant requirements for prudent grazing. In National Research Council, & National Academy of Sciences, Developing strategies for rangeland management (pp. 117-152). Boulder, CO: Westview Press.

Caldwell, M. M., Richards, J. H., Manwaring, J. H., & Eissenstat, D. M. (1987). Rapid shifts in phosphate acquisition show direct competition between neighboring plants. Nature, 327(6123), 615-616. doi:10.1038/327615a0

Calkin, D. E., Gebert, K. M., Jones, J. G., & Neilson, R. P. (2005). Forest Service large fire area burned and suppression expenditure trends, 1970-2002. Journal of Forestry, 103(4), 179-183.

Chambers, J. C., Roundy, B. A., Blank, R. R., Meyer, S. E., & Whittaker, A. (2007). What makes Great Basin sagebrush ecosystems invasible by Bromus tectorum?. Ecological Monographs, 77(1), 117-145. doi:10.1890/05-1991

Clausnitzer, D. W., Borman, M. M., & Johnson, D. E. (1999). Competition between Elymus elymoides and Taeniatherum caput-medusae. Weed Science, 47(6), 720-728.

Courtois, D. R., Perryman, B. L., & Hussein, H. S. (2004). Vegetation change after 65 years of grazing and grazing exclusion. Journal of Range Management, 57(6), 574-582. doi:10.2307/4004011

Curtin, C. G., Fleischner, T. L., Haas, C. A., Fraser, J. D., Noss, R., Wuerthner, G., Belsky, J., Willers, B., Brussard, P. f., Murphy, D. D., & Tracy, C. R. (1995). Grazing and advocacy. Conservation Biology, 9(2), 233-239. doi: 10.1046/j.1523-1739.1995.9020233.x

Curtin, C. G. (2002). Livestock grazing, rest, and restoration in arid landscapes. Conservation Biology, 16(3), 840-842. doi:10.1046/j.1523-1739.2002.01212.x

D'Antonio, C. M., & Vitousek, P. M. (1992). Biological invasions by exotic grasses, the grass/fire cycle, and global change. Annual Review of Ecology and Systematics, 23, 63-87. doi:10.1146/annurev.es.23.110192.000431

Daubenmire, R. (1970). Steppe vegetation of Washington (Technical Bulletin No. 62). Pullman, WA: Washington State University, Washington Agricultural Experiment Station.

Davies, K. W. (2008). Medusahead dispersal and establishment in sagebrush steppe plant communities. Rangeland Ecology & Management, 61(1), 110-115. doi:10.2111/07-041R2.1

Davies, K. W., Bates, J. D., & Nafus, A. M. (2012). Mowing Wyoming big sagebrush communities with degraded herbaceous understories: has a threshold been crossed? Rangeland Ecology & Management, 65(5):498-505. doi:10.2111/REM-D-12-00026.1

Davies, K. W., Bates, J. D., Svejcar, T. J., & Boyd, C. S. (2010). Effects of long-term livestock grazing on fuel characteristics in rangelands: an example from the sagebrush steppe. Rangeland Ecology & Management, 63(6), 662-669. doi:10.2111/REM-D-10-00006.1

Davies, K. W., Boyd, C. S., Beck, J. L., Bates, J. D., Svejcar, T. J., & Gregg, M. A. (2011). Saving the sagebrush sea: an ecosystem conservation plan for big sagebrush plant communities. Biological Conservation, 144(11), 2573-2584. doi:10.1016/j.biocon.2011.07.016

Davies, K. W., & Nafus, A. M. (2013). Exotic annual grass invasion alters fuel amounts, continuity and moisture content. International Journal of Wildland Fire, 22(3), 353-358. doi:10.1071/WF11161

Davies, K. W., Svejcar, T. J., & Bates, J. D. (2009). Interaction of historical and nonhistorical disturbances maintains native plant communities. Ecological Applications, 19(6), 1536-1545. doi:10.1890/09-0111.1

Diamond, J. M., Call, C. A., & Devoe, N. (2010). Effects of targeted cattle grazing on fire behavior of cheatgrass-dominated rangeland in the northern Great Basin, USA. International Journal of Wildland Fire, 18(8), 944-950. doi:10.1071/WF08075

Diamond, J. M., Call, C. A., and Devoe, N. (2012). Effects of targeted grazing and prescribed burning on community and seed dynamics of downy brome (Bromus tectorum)-dominated landscapes. Invasive Plant Science and Management, 5(2), 259-269.

Donahue, D.L. 1999. The western range revisited: removing livestock from public lands to conserve native biodiversity (Vol 5). Norman, OK: University of Oklahoma Press.

Eckert Jr, R. E., & Spencer, J. S. (1986). Vegetation response on allotments grazed under rest-rotation management. Journal of Range Management, 39(2), 166-174. doi:10.2307/3899292

Eckert Jr, R. E., & Spencer, J. S. (1987). Growth and reproduction of grasses heavily grazed under rest-rotation management. Journal of Range Management, 40(2), 156-159. doi:10.2307/3899210

Evans, C. C. (1986). The relationship of cattle grazing to sage-grouse use of meadow habitat on the Sheldon National Wildlife Refuge (Master’s thesis). University of Nevada, Reno, NV, USA.

Fleischner, T. L. (1994). Ecological costs of livestock grazing in western North America. Conservation Biology, 8(3), 629-644. doi:10.1046/j.1523-1739.1994.08030629.x

Fox, M. A., & Eddleman, L. E. (2003). A time comparison study of vegetation on the Island Research Natural Area in central Oregon. Northwest Science, 77(3), 246-254.

Fuhlendorf, S. D., & Engle D. M. (2004). Application of the fire-grazing interaction to restore a shifting mosaic on tallgrass prairie. Journal of Applied Ecology, 41(4), 604-614. doi:10.1111/j.0021-8901.2004.00937.x

Ganskopp, D., Svejcar, T., Taylor, F., Farstvedt, J., & Paintner, K. (1999). Seasonal cattle management in 3 to 5 year old bitterbrush stands. Journal of Range Management, 52(2), 166-173. doi:10.2307/4003512

Harris, G. A. (1967). Some competitive relationships between Agropyron spicatum and Bromus tectorum. Ecological Monographs, 37(2), 89-111. doi:10.2307/2937337

Hartnett, D. C. (1989). Density-and growth stage-dependent responses to defoliation in two rhizomatous grasses. Oecologia, 80(3), 414-420. doi:10.1007/BF00379045

Hilty, J. E., Eldridge, D. J., Rosentreter, R., Wicklow-Howard, M. C., & Pellant, P. (2004). Recovery of biological soil crust following wildfire in Idaho. Journal of Range Management, 57(1) 89-96.

Holechek, J. L., & Stephenson, T. (1983). Comparison of big sagebrush vegetation in northcentral New Mexico under moderately grazed and grazing excluded conditions. Journal of Range Management, 36(4), 455-456.

Holechek, J. L., Pieper, R. D., & Herbel, C. H. (1998). Range management: principles and practices. Upper Saddle River, NJ: Prentice-Hall.

Hormay, A.L. 1970. Principles of rest-rotation grazing and multiple use land management (Training Text No. 4[2200]). Washington, D.C.: USDA, Forest Service.

Hyder, D. N., & Sneva, F. A. (1963). Morphological and physiological factors affecting the grazing management of crested wheatgrass. Crop Science, 3(26), 267-271.

James, J. J., Davies, K. W., Sheley, R. L., & Aanderud, Z. T. (2008). Linking nitrogen partitioning and species abundance to invasion resistance in the Great Basin. Oecologia, 156(3), 637-648. doi:10.1007/s00442-008-1015-0

Johansen, J. R. (2001). Impacts of fire on biologicalsoil crusts. pp. 385 -400. In: J. Belnapand O. Lange (eds.) Biological soil crusts:structure, management and function. Ecological studies 150. Springer Verlag, Berlin.

Johnson, T. N., Kennedy, P. L., DelCurto, T., & Taylor, R. V. (2011). Bird community responses to cattle stocking rates in a Pacific Northwest bunchgrass prairie. Agriculture, Ecosystems & Environment, 144(1), 338-346. doi:10.1016/j.agee.2011.10.003

Jones, A. (2000). Effects of cattle grazing on North American arid ecosystems: a quantitative review. Western North American Naturalist, 60(2), 155-164.

Jones, A. L., & Longland, W. S. (1999). Effects of cattle grazing on salt desert rodent communities. The American Midland Naturalist, 141(1), 1-11. doi:10.1674/0003-0031(1999)141[0001:EOCGOS]2.0.CO;2

Knapp, P. A. (1996). Cheatgrass (Bromus tectorum L.) dominance in the Great Basin Desert: History, persistence, and influences to human activities. Global Environmental Change, 6(1), 37-52. doi:10.1016/0959-3780(95)00112-3

Knapp, P., & Soulé, P. T. (1998). Recent Juniperus occidentalis (western juniper) expansion on a protected site in central Oregon. Global Change Biology, 4(3), 347-357. doi:10.1046/j.1365-2486.1998.00160.x

Knight, R. L., Wallace, G. N., & Riebsame, W. E. (1995). Ranching the view: subdivisions versus agriculture. Conservation Biology, 9(2), 459-461. doi:10.1046/j.1523-1739.1995.9020459.x

Knopf, F. L. (1996). Perspectives on grazing nongame bird habitats. In P. R. Krausman, (Ed.), Rangeland wildlife (pp. 51-58). Denver, CO: Society for Range Management.

Laycock, W. A. (1967). How heavy grazing and protection affect sagebrush-grass ranges. Journal of Range Management, 20(4), 206-213. doi:10.2307/3896253

Lesperance, A. L., Tueller, P. T., & Bohman, V. R. (1970). Symposium on pasture methods for maximum production in beef cattle: Competitive use of the range forage resource. Journal of Animal Science, 30(1), 115-121.

Liang, J., Calkin, D. E., Gebert, K. M., Venn, T. J., & Silverstein, R. P. (2008). Factors influencing large wildland fire suppression expenditures. International Journal of Wildland Fire, 17(5), 650-659. doi:10.1071/WF07010

Mack, R. N. (1981). Invasion of Bromus tectorum L. into Western North America: An ecological chronicle. Agro-ecosystems, 7(2), 145-165. doi:10.1016/0304-3746(81)90027-5

Mack, R. N., & Thompson, J. N. (1982). Evolution in steppe with few large, hooved mammals. American Naturalist, 119(6), 757-773.

Maestas, J. D., Knight, R. L., & Gilgert, W. C. (2003). Biodiversity across a rural land‐use gradient. Conservation Biology, 17(5), 1425-1434. doi:10.1046/j.1523-1739.2003.02371.x

Manier, D. J., & Hobbs, N. T. (2006). Large herbivores influence the composition and diversity of shrub-steppe communities in the Rocky Mountains, USA. Oecologia, 146(4), 641-651. doi:10.1007/s00442-005-0065-9

Manier, D. J., & Hobbs, N. T. (2007). Large herbivores in sagebrush steppe ecosystems: livestock and wild ungulates influence structure and function. Oecologia, 152(4), 739-750. doi:10.1007/s00442-007-0689-z

Mata-Gonzalez, R. R. G. H., Hunter, R. G., Coldren, C. L., McLendon, T., & Paschke, M. W. (2007). Modelling plant growth dynamics in sagebrush steppe communities affected by fire. Journal of Arid Environments, 69(1), 144-157. doi:10.1016/j.jaridenv.2006.09.010

McAdoo, J. K., Schultz, B. W., & Swanson, S. R. (2013). Aboriginal precedent for active management of sagebrush-perennial grass communities in the Great Basin. Rangeland Ecology & Management, 66(3), 241-253. doi:10.2111/REM-D-11-00231.1

Melgoza, G., Nowak, R. S., & Tausch, R. J. (1990). Soil water exploitation after fire: competition between Bromus tectorum (cheatgrass) and two native species. Oecologia, 83(1), 7-13. doi:10.1007/BF00324626

Milchunas, D. G., & Lauenroth, W. K. (1993). Quantitative effects of grazing on vegetation and soils over a global range of environments. Ecological Monographs, 63(4), 327-366. doi:10.2307/2937150

Miller, R. F. & Rose, J. R. (1995). Historic expansion of Juniperus occidentalis southeastern Oregon. Great Basin Naturalist, 55(1), 37-45.

Miller, R. F., & Rose, J. A. (1999). Fire history and western juniper encroachment in sagebrush steppe. Journal of Range Management, 52(6), 550-559. doi:10.2307/4003623

Miller, R. F., & Wigand, P. E. (1994). Holocene changes in semiarid pinyon-juniper woodlands. BioScience, 44(7), 465-474. doi:10.2307/1312298

Miller, R. F., Svejcar, T. J., & Rose, J. A. (2000). Impacts of western juniper on plant community composition and structure. Journal of Range Management, 53(6), 574-585. doi:10.2307/4003150

Miller, R. F., Bates, J. D., Svejcar, A. J., Pierson Jr, F. B., & Eddleman, L. E. (2005). Biology, ecology, and management of western juniper (Juniperus occidentalis) (Bulletin No. 152). Corvallis, OR: Oregon State University Agricultural Experiment Station.

Morrow, M. E., Adamcik, R. S., Friday, J. D., & McKinney, L. B. (1996). Factors affecting Attwater's prairie-chicken decline on the Attwater Prairie Chicken National Wildlife Refuge. Wildlife Society Bulletin, 24(4), 593-601.

Mueggler, W. F. (1975). Rate and pattern of vigor recovery in Idaho fescue and bluebunch wheatgrass. Journal of Range Management, 28(3), 198-204. doi:10.2307/3897525

Muscha, J. M., & Hild, A. L. (2006). Biological soil crusts in grazed and ungrazed Wyoming sagebrush steppe. Journal of Arid Environments, 67(2), 195-207. doi:10.1016/j.jaridenv.2006.02.010

NIFC [National Interagency Fire Center] (2013) Fire information –wildland fire statistics. http://www.nifc.gov/fireInfo/fireInfo_documents

Payne, N. F., & Bryant, F. C. (1994). Techniques for wildlife habitat management of uplands. New York, NY: McGraw-Hill, Inc.

Pierson, F. B., Bates, J. D., Svejcar, T. J., & Hardegree, S. P. (2007). Runoff and erosion after cutting western juniper. Rangeland Ecology & Management, 60(3), 285-292. doi:10.2111/1551-5028(2007)60[285:RAEACW]2.0.CO;2

Ponzetti, J. M., & McCune, B. P. (2001). Biotic soil crusts of Oregon's shrub steppe: community composition in relation to soil chemistry, climate, and livestock activity. The Bryologist, 104(2), 212-225. doi:10.1639/0007-2745(2001)104[0212:BSCOOS]2.0.CO;2

Ponzetti, J. M., McCune, B., & Pyke, D. A. (2007). Biotic soil crusts in relation to topography, cheatgrass and fire in the Columbia Basin, Washington. The Bryologist, 110(4), 706-722. doi:10.1639/0007-2745(2007)110[706:BSCIRT]2.0.CO;2

Provencher, L., Forbis, T. A., Frid, L., & Medlyn, G. (2007). Comparing alternative management strategies of fire, grazing, and weed control using spatial modeling. Ecological Modelling, 209(2), 249-263. doi:10.1016/j.ecolmodel.2007.06.030

Pyke, C. R., & Marty, J. (2005). Cattle grazing mediates climate change impacts on ephemeral wetlands. Conservation Biology, 19(5), 1619-1625. doi:10.1111/j.1523-1739.2005.00233.x

Rice, B., & Westoby, M. (1978). Vegetative responses of some Great Basin shrub communities protected against jackrabbits or domestic stock. Journal of Range Management, 31(1), 28–34. doi:10.2307/3897627

Rickard, W. H. (1985). Experimental cattle grazing in a relatively undisturbed shrubsteppe community. Northwest Science, 59(1), 66-72.

Rimbey, N. R., Torell, L. A., & Tanaka, J. A. (2007). Why grazing permits have economic value. Journal of Agricultural and Resource Economics, 32(1), 20-40.

Rimbey, N.R. & Torell, L.A. 2011. Grazing costs: What’s the current situation? Univ. of Idaho. Dept. of Ag. Econ. & Rural Soc. AEE series 2011-02. Available online at: http://web.cals.uidaho.edu/idahoagbiz/files/2013/01/GrazingCost2011.pdf

Robertson, J. H. (1971). Changes on a Sagebrush-Grass Range in Nevada Ungrazed for 30 Years. Journal of Range Management, 24(5), 397–400. doi:10.2307/3896614

Rosenstock, S. S. (1996). Shrub-grassland small mammal and vegetation responses to rest from grazing. Journal of Range Management, 49(3), 199-203. doi:10.2307/4002878

Schultz, B. 2010. A Review of Nest Trampling by Livestock and the Implications for Nesting Birds on Shrub-Grass Rangelands in the Western States. In: Proceedings – Fourth National Conference on Grazing Lands. Grazing Lands Conservation Initiative and Society for Range Management. December 13-16, 2009. Sparks, NV Pages 540-550.

Severson, K. E., & Urness, P. J. (1994). Livestock grazing: A tool to improve wildlife habitat. In: M. Vavra, W. A. Laycock, and R. D. Pieper (Eds.), Ecological implications of livestock herbivory in the west (pp. 232-249). Denver, CO: Society for Range Management.

Shrestha, G., & Stahl, P. D. (2008). Carbon accumulation and storage in semi-arid sagebrush steppe: Effects of long-term grazing exclusion. Agriculture, Ecosystems & Environment, 125(1), 173-181. doi:10.1016/j.agee.2007.12.007

Sneva, F. A., Rittenhouse, L. R. & Tueller, P. T. (1980). Forty years - inside and out. In Research in rangeland management (Special Report No. 586; pp. 10-12). Corvallis, OR: Oregon State University, Oregon Agricultural Experiment Station.

Svejcar, T., & Tausch, R. (1991). Anaho Island, Nevada: a relict area dominated by annual invader species. Rangelands, 13(5), 233-236.

Teague, W. R., & Dowhower, S. L. (2003). Patch dynamics under rotational and continuous grazing management in large, heterogeneous paddocks. Journal of Arid Environments, 53(2), 211-229. doi:10.1006/jare.2002.1036

Torell, L.A., VanTassell, L.W., Rimbey, N.R., Bartlett, E.T., Bagwell, T., Burgener, P., & Coen, J. (1993) New Mexico State Univ. Ag. Exp. Sta. Bull. 767.

Torell, L.A., Rimbey, N.R., Tanaka, J.A., Taylor, D.T., & Wulfhorst, J.D. In Review Process. Ranch Level Economic Impact Analysis for Public Lands: A Guide to Methods, Issues, and Applications. J. Rangeland Applications.

Torell, L.A., Torell, G. L., Tanaka, J.A., & Rimbey, N.R. (2013) The potential for valuing ecosystem services on public rangelands. Western Economics Forum XII (1): 40-46. Available on-line at: http://www.waeaonline.org/UserFiles/file/WEFSpring2013.pdf

Van Tassell, L. W., & Richardson, J. W. (1998). Impact of federal grazing reductions on Wyoming ranches. In Stubble height and utilization measurements : uses and misuses (Research Bulletin No. 682; pp. 50-56). Corvallis, OR: Oregon State University, Agricultural Experiment Station.

Vavra, M. (2005). Livestock grazing and wildlife: Developing compatibilities. Rangeland Ecology & Management, 58(2), 128-134. doi:10.2111/1551-5028(2005)58<128:LGAWDC>2.0.CO;2

Waldram, M. S., Bond, W. J., & Stock, W. D. (2008). Ecological engineering by a mega-grazer: white rhino impacts on a South African savanna. Ecosystems, 11(1), 101-112. doi:10.1007/s10021-007-9109-9

West, N. E., Provenza, F. D., Johnson, P. S., & Owens, M. K. (1984). Vegetation change after 13 years of livestock grazing exclusion on sagebrush semidesert in west central Utah. Journal of Range Management, 37(3), 262–264. doi:10.2307/3899152

Wilkins, N., Hays, A., Kubenka, D., Steinbach, D., Grant, W., Gonzalez, E., Kjelland, M. & Shackelford, J. (2003). Texas rural lands: Trends and conservation implications for the 21st century. College Station, TX: Texas A&M University, Texas Agricultural Experiment Station.

Yeo, J. J. (2005). Effects of grazing exclusions on rangeland vegetation and soils, east central Idaho. Western North American Naturalist, 65(1), 91–102.

Yorks, T. P., West, N. E., & Capels, K. M. (1992). Vegetation differences in desert shrublands of western Utah’s Pine Valley between 1933 and 1989. Journal of Range Management, 45(6), 569–578. doi:10.2307/4002574.

Young, K. R., & Mangold, J. M. (2008). Medusahead outperforms squirreltail through interference and growth rate. Journal of Invasive Plant Science and Management, 1, 73-81.

Ziegenhagen, L. L., & Miller, R. F. (2009). Postfire recovery of two shrubs in the interiors of large burns in the Intermountain West, USA. Western North American Naturalist, 69(2), 195-205. doi:10.3398/064.069.0208.