Abstract
Improving understanding of the connections between vegetation, herbivory, and ecosystem function offers a fundamental challenge in contemporary terrestrial ecology. Using exclosures constructed during the late 1950s, we examined effects of grazing by wild and domestic herbivores on plant community structure, aboveground herbaceous primary production, and nutrient cycling at six sites in semi-arid, sagebrush rangelands during 2001–2002 in Colorado, USA. Enclosures provided three treatments: no grazing, grazing by wild ungulates only, and grazing by wild and domestic ungulates. Excluding all grazing caused an increase in shrub cover (F = 4.97, P = 0.033) and decrease in bare ground (F = 4.74, P = 0.037), but also a decrease in plant species richness (F = 6.19, P = 0.018) and plant diversity (F = 7.93, P = 0.008). Effects of wild ungulate grazing on plant cover and diversity were intermediate to the effects of combined domestic and wild grazing. Aboveground net primary production was higher in both grazed treatments than in the ungrazed one (F wild + domestic = 2.98, P = 0.0936 and F wild only = 3.55, P = 0.0684). We were unable to detect significant effects of grazing on other ecosystem states and processes including C:N ratios of standing crops, N mineralization potential, or nitrification potential. Best approximating models revealed positive correlation between N availability and herbaceous cover and a negative correlation between herbaceous primary production and the ratio of shrub–herb cover and plant diversity. We conclude that ungulate herbivory, including both wild and domestic ungulates, had significant effects on plant community structure and ecosystem function during this 42-year span. Responses to the wild ungulate treatment were consistently intermediate to responses to the no grazing and wild + domestic grazing treatments. However, we were unable to detect statistical difference between effects of wild ungulates alone and wild ungulates in combination with livestock.
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Notes
We likely encountered Seriphidium arbusculum on four, or more, of the sites. However, we did not distinguish this species from S. vasyanum, because we did not witness the phenology necessary for the distinction (Weber and Wittmann 2001).
We use the term “graze” to include feeding on grasses, forbs, and shrubs.
References
Aguiar MR, Paruelo JM, Sala OE, Lauenroth WK (1996) Ecosystem responses to changes in plant functional type composition: an example from the Patagonian steppe. J Veg Sci 7:381–390
Augustine DJ, McNaughton SJ (1998) Ungulate effects on the functional species composition of plant communities: herbivore selectivity and plant tolerance. J Wildl Manage 62(4):1165–1183
Augustine DJ, McNaughton SJ, Frank DA (2003) Feedbacks between soil nutrients and large herbivores in a managed savanna ecosystem. Ecol Appl 13(5):1325–1337
Bailey RG, Avers PE, King T, McNab WH (eds) (1994) Ecoregions and subregions of the United States (map with supplementary table of map unit descriptions, 1:7,500,000). USDA Forest Service, Washington, D.C.
Beeskow AM, Ellisalde NO, Rostagno CM (1995) Ecosystem changes associated with grazing intensity on the Punta Ninfas rangelands of Patagonia, Argentina. J Range Manage 48(6):517–522
Belsky AJ, Blumenthal DM (1997) Effects of livestock grazing on stand dynamics and soils in upland forests of the interior. West Conserv Biol 11(2):315–327
Bolton H, Smith JL, Wildung RE (1990) Nitrogen mineralization potentials of shrub-steppe soils with different disturbance histories. Soil Sci Soc Am J 54(3):887–891
Burke IC, Lauenroth WK, Vinton MA, Hook PB, Kelly RH (1998) Plant–soil interactions in temperate grasslands. Biogeochemistry 42(1–2):121–143
Burnam KP, Anderson DR (1998) Model selection and inference. A practical information-theoretic approach. Springer, Berlin Heidelberg New York
Chew RM (1982) Changes in herbaceous and suffrutescent perennials in grazed and ungrazed desertified grassland in southeastern Arizona, 1958–1978. Am Midl Nat 108:159–169
Coughenour MB (1991) Biomass and nitrogen responses to grazing of upland steppe on Yellowstone northern winter range. J Appl Ecol 28(1):71–82
Frank DA (1998) Ungulate regulation of ecosystem processes in Yellowstone National Park: direct and feedback effects. Wildl Soc Bull 26(3):410–418
Frank DA, PM Groffman (1998) Ungulate vs landscape control of soil C and N processes in grasslands of Yellowstone National Park. Ecology 79(7):2229–2241
Frank DA, McNaughton SJ (1990) Aboveground biomass estimation with the canopy intercept method: a plant growth form caveat. Oikos 57:57–60
Frank DA, McNaughton SJ (1992) The ecology of plants, large mammalian herbivores, and drought in Yellowstone National Park. Ecology 73(6):2043–2058
Frank D, McNaughton SJ (1993) Evidence for the promotion of above ground grassland production by native large herbivores in Yellowstone National Park. Oecologia 96:157–161
Frank DA, Inouye RS, Huntly N, Minshall GW, Anderson JE (1994) The biogeochemistry of a north-temperate grassland with native ungulates—nitrogen dynamics in Yellowstone National Park. Biogeochemistry 26(3):163–188
Garcia-Montiel DC, Binkley D (1998) Effect of Eucalyptus saligna and Albizia falcataria on soil processes and nitrogen supply in Hawaii. Oecologia 113(4):547–556
Gill RB, Beck TDI, Bishop CJ, Freddy DJ, Hobbs NT, Kahn RH, Miller MW, Pojar TM, White GC (1999) Declining mule deer populations in Colorado: reasons and responses: a report to the Colorado Legislature. Unpublished wildlife report. Project number CO W-15. Colorado Division of Wildlife, Colo.
Green RA, Detling JK (2000) Defoliation-induced enhancement of total aboveground nitrogen yield of grasses. Oikos 91(2):280–284
Hillebrand H (2003) Opposing effects of grazing and nutrients on diversity. Oikos 100(3):592–600
Heisler JL, Knapp AK, Briggs JM (2003) Long-term patterns of shrub expansion in a C4-dominated grassland: fire frequency and the dynamics of shrub cover and abundance. Am J Bot 90(3):423–428
Hobbs NT (1996) Modification of ecosystems by ungulates. J Wildl Manage 60(4):695–713
Hobbs NT (2006) Large herbivores as sources of disturbance in ecosystems. In: Danell K, Pastor J, Bergström R, Duncan P (eds) Large herbivore ecology and ecosystem dynamics. Cambridge University Press, Cambridge, pp 261–288
Hobbs NT, Baker DL, Gill RB (1983) Comparative nutritional ecology of montane ungulates during winter. J Wildl Manage 47:1–16
Hobbs NT, Baker DL, Bear GD, Bowden DC (1996) Ungulate grazing in sagebrush grassland: effects of resource competition on secondary production. Ecol Appl 6(1):218–227
Huenneke LF, Anderson JP, Remmenga M, Schlesinger WH (2002) Desertification alters patterns of aboveground net primary production in Chihuahuan ecosystems. Global Change Biol 8:247–264
Jones A (2000) Effects of cattle grazing on North American arid ecosystems: a quantitative review. West N Am Nat 60(2):155–164
Kufeld RC, Walmo OC, Feddema C (1973) Foods of the Rocky Mountain mule deer. Research paper RM-111. USDA Forest Service
Laycock WA (1991) Stable states and thresholds of range condition on North American Rangelands—a viewpoint. J Range Manage 44(5):427–433
Lecain DR, Morgan JA, Schuman GE, Reeder JD, Hart RH (2000) Carbon exchange rates in grazed and ungrazed pastures of Wyoming. J Range Manage 53(2):199–206
Leriche H, Le Roux X, Desnoyers F, Benest D, Simioni G, Abbadie L (2003) Grass response to clipping in an African savanna: testing the grazing optimization hypothesis. Ecol Appl 13(5):1346–1354
Lett MS, Knapp AK (2006) Woody plant encroachment and removal in mesic grassland: production and composition responses of herbaceous vegetation. Am Midl Nat 153:217–231
Lubchenco J (1978) Plant species diversity in a marine intertidal community: importance of herbivore food preference and algal competitive abilities. Am Nat 112:23–39
Mack RN, Thompson JN (1982) Evolution in steppe with few large, hoofed mammals. Am Nat 119(6):757–773
Madany MH, West NE (1983) Livestock grazing-fire regime interactions within montane forests of Zion National Park, Utah. Ecology 64(4):661–667
Manier DJ, Hobbs NT (2006) Large herbivores influence the composition and diversity of shrub steppe communities in the Rocky Mountains, USA. Oecologia 146(4):641–651
McNaughton SJ, Milchunas DG, Frank DA (1996) How can net primary productivity be measured in grazing ecosystems? Ecology 77(3):974–977
Milchunas DG, Lauenroth WK (1993) Quantitative effects of grazing on vegetation and soils over a global range of environments. Ecol Monogr 63(4):327–366
Rabe MJ, Rosenstock SS, deVos JC (2002) Review of big-game survey methods used by wildlife agencies of the western United States Source. Wildl Soc Bull 30(1):46–52
Reynolds RT, Trost CH (1980) The response of native vertebrate populations to crested wheatgrass planting and grazing by sheep. J Range Manage 33:122–125
Rueth HM, Baron JS (2002) Differences in Englemann spruce forest biogeochemistry east and west of the Continental Divide in Colorado, USA. Ecosystems 5(1):45–57
Schlesinger WH, Raikes JA, Hartley AE, Cross AF (1996) On the spatial pattern of soil nutrients in desert ecosystems. Ecology 77(2):364–374
Schultz TT, Leininger WC (1990) Differences in riparian vegetation structure between grazing areas and exclosures. J Range Manage 43:295–299
Singer FJ (1995) Effects of ungulate herbivory and fire on the grasses and shrubs of Yellowstone’s Northern Winter Range. Dissertation, Colorado State University, Fort Collins, Colo.
Singer, FJ (1996) Differences between willow communities browsed by elk and communities protected for 32 years in Yellowstone National Park. In: FJ Singer (ed) Effects of grazing by wild ungulates. Yellowstone National Park technical report. USDI, National Park Service, Natural Resource Information Division
Smith JL, Halvorson JJ, Bolton H (1994) Spatial relationships of soil microbial biomass and C and N mineralization in a semi-arid shrub-steppe ecosystem. Soil Biol Biochem 26(9):1151–1159
Sommer U (1999) The impact of herbivore type and grazing pressure on benthic microalgal diversity. Ecol Lett 2:65–69
Stark S, Wardle DA, Ohtonen R, Helle T, Yeates GW (2002) The effect of reindeer grazing on decomposition, mineralization and soil biota in a dry oligotrophic Scots pine forest. Oikos 90(2):301–310
Stohlgren TJ, Falkner MB, Schell LD (1995) A modified-Whittaker nested vegetation sampling method. Vegetation 117:113–121
Stohlgren TJ, Schell LD, Vanden Heuvel B (1999) How grazing and soil quality affect native and exotic plant diversity in Rocky Mountain grasslands. Ecol Appl 9(1):45–64
Tausch RJ, Wigand PE, Burkhardt JW (1993) Viewpoint: plant community thresholds, multiple steady states, and multiple successional pathways: legacy of the quaternary? J Range Manage 46:439–447
Valentine SC, Bartsch BD (1990) Milk-production by dairy-cows fed legume grains or barley-grain with or without urea as supplements to a cereal hay based diet Australian. J Exp Agric 30(1):7–10
Weber WA, Wittmann RC (2001) Colorado flora, vol. eastern slope and western slope, 3rd edn. University Press of Colorado, Boulder, Colo.
West NE (1988) Intermountain deserts, shrub steppes and woodlands. In: Barbour MG, Billings WD (eds) North American terrestrial vegetation. Cambridge University Press, New York, pp 209–230
Willms WD, Dormaar JF, Adams BW, Douwes HE (2002) Response of the mixed prairie to protection from grazing. J Range Manage 55(3):210–216
Zimmerman GT, Neuenschwander LF (1984) Livestock grazing influences on community structure, fire intensity, and fire frequency within the Douglas-fir Ninebark habitat type. J Range Manage 37(2):104–110
Acknowledgements
The authors are grateful to the Colorado Division of Wildlife, Habitat Division for funding this project, providing logistical support for the research, and preserving the old data and records that enabled re-discovery of these sites. We are also grateful to several diligent crews of seasonal, student employees who helped provide the labor of estimating primary production over two growing seasons, sorting vegetation and soils in the laboratory, assisting in N extractions and running the combustion auto-analyzer. Without their skills, effort, and persistence, this project could not have been completed. We are also grateful to multiple, anonymous reviewers, and the editor, who provided thoughtful comments to improve this manuscript.
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Communicated by Jim Ehleringer.
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Manier, D.J., Hobbs, N.T. Large herbivores in sagebrush steppe ecosystems: livestock and wild ungulates influence structure and function . Oecologia 152, 739–750 (2007). https://doi.org/10.1007/s00442-007-0689-z
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DOI: https://doi.org/10.1007/s00442-007-0689-z