Abstract
Increased resource availability can facilitate establishment of exotic plant species, especially when coincident with propagule supply. Following establishment, increased resource availability may also facilitate the spread of exotic plant species if it enhances their competitive abilities relative to native species. Exotic Canada geese (Branta canadensis) introduce both exotic grass seed and nutrients to an endangered plant community on the Gulf Islands of southwestern British Columbia, Canada. I used greenhouse experiments to assess the competitive advantage of the exotic grasses relative to native and exotic forbs in this community and to test the impacts of nutrient addition from goose feces on competitive outcomes. I grew experimental communities varying in their proportion of forbs versus exotic grasses, and added goose feces as a nutrient source. I found that both native and exotic forbs produced significantly more biomass in competition with conspecifics than in competition with the grasses, and that the proportional abundance of two out of three native forbs was lowest in the combined presence of exotic grasses and nutrient addition. In a second experiment, I found that in monoculture all species of forbs and grasses showed equal growth responses to nutrients. The exotic species did not convert additional nutrients into additional biomass at a higher rate, but did germinate earlier and grow larger than the native species regardless of nutrient availability. This suggests that the exotic species may have achieved their competitive advantage partly by pre-empting resources in community mixtures. Small and late-germinating native forbs may be particularly vulnerable to competitive suppression from exotic grasses and forbs and may be at an even greater disadvantage if their competitors are benefiting from early access to additional nutrients. In combination, the input of exotic propagules and additional nutrients by nesting geese may compromise efforts to maintain native community composition in this system.
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References
Allcock KG (2002) Effects of phosphorus on growth and competitive interactions of native and introduced species found in white box woodlands. Austral Ecol 27:638–646
Baruch Z, Goldstein G (1999) Leaf construction cost, nutrient concentration, and net CO2 assimilation of native and invasive species in Hawaii. Oecologia 121:183–192
Bazely DR, Jefferies RL (1985) Goose feces: a source of nitrogen for plant-growth in a grazed salt-marsh. J Appl Ecol 22:693–703
Blossey B, Notzold R (1995) Evolution of increased competitive ability in invasive nonindigenous plants: a hypothesis. J Ecol 83:887–889
Busey P (2003) Cultural management of weeds in turfgrass: a review. Crop Sci 43:1899–1911
Cochran VL, Pugin JA, Sparrow SD (2000) Effects of migratory geese on nitrogen availability and primary productivity in subarctic barley fields. Biol Fertil Soils 32:340–346
Corbin JD, D’Antonio CM (2004) Effects of exotic species on soil nitrogen cycling: implications for restoration. Weed Tech 18:1464–1467
D’Antonio CM (1993) Mechanisms controlling invasion of coastal plant-communities by the alien succulent Carpobrotus edulis. Ecology 74:83–95
Daehler CC (2001) Darwin’s naturalization hypothesis revisited. Am Nat 158:324–330
Daehler CC (2003) Performance comparisons of co-occurring native and alien invasive plants: implications for conservation and restoration. Annu Rev Ecol Evol S 34:183–211
Davis MA, Grime JP, Thompson K (2000) Fluctuating resources in plant communities: a general theory of invasibility. J Ecol 88:528–534
di Castri F (1973) Climatographical comparisons between Chile and the Western Coast of North America. In: di Castri F, Mooney HA (eds) Mediterranean type ecosystems, vol 7. Springer, Berlin, pp 21–36
Dietz H, Edwards PJ (2006) Recognition that causal processes change during plant invasion helps explain conflicts in evidence. Ecology 87:1359–1367
Fargione JE, Tilman D (2005) Diversity decreases invasion via both sampling and complementarity effects. Ecol Lett 8:604–611
Fox BJ (1987) Species assembly and the evolution of community structure. Evol Ecol 1:201–213
Fuchs MA (2001) Towards a recovery strategy for garry oak and associated ecosystems in Canada: ecological assessment and literature review. Technical report GBEI/EC–00-030. Environment Canada, Canadian Wildlife Service, Ladner
Griffin JR (1977) Oak woodland. In: Barbour MG, Major J (eds) Terrestrial vegetation of California. Wiley, New York, pp 383–416
Gross KL, Mittelbach GG, Reynolds HL (2005) Grassland invasibility and diversity: responses to nutrients, seed input, and disturbance. Ecology 86:476–486
Groves RH, Austin MP, Kaye PE (2003) Competition between Australian native and introduced grasses along a nutrient gradient. Austral Ecol 28:491–498
Hobbs RJ, Huenneke LF (1992) Disturbance, diversity, and invasion: implications for conservation. Conserv Biol 6:324–337
Hobbs RJ, Humphries SE (1995) An integrated approach to the ecology and management of plant invasions. Conserv Biol 9:761–770
Huenneke LF, Hamburg SP, Koide R, Mooney HA, Vitousek PM (1990) Effects of soil resources on plant invasion and community structure in Californian serpentine grassland. Ecology 71:478–491
Huntly N (1991) Herbivores and the dynamics of communities and ecosystems. Annu Rev Ecol Syst 22:477–503
Jackson RB, Caldwell MM (1992) Shading and the capture of localized soil nutrients: nutrient contents, carbohydrates, and root uptake kinetics of a perennial tussock grass. Oecologia 91:457–462
Kolb A, Alpert P, Enters D, Holzapfel C (2002) Patterns of invasion within a grassland community. J Ecol 90:871–881
Lake JC, Leishman MR (2004) Invasion success of exotic in natural ecosystems: the role of disturbance, plant attributes and freedom from herbivores. Biol Conserv 117:215–226
Leishman MR, Thomson VP (2005) Experimental evidence for the effects of additional water, nutrients and physical disturbance on invasive plants in low fertility Hawkesbury Sandstone soils, Sydney, Australia. J Ecol 93:38–49
Levine JM, Adler PB, Yelenik SG (2004) A meta-analysis of biotic resistance to exotic plant invasions. Ecol Lett 7:975–989
MacDougall AS, Turkington R (2005) Are invasive species the drivers or passengers of change in degraded ecosystems? Ecology 86:42–55
MacDougall AS, Boucher J, Turkington R, Bradfield GE (2006) Patterns of plant invasion along an environmental stress gradient. J Veg Sci 17:47–56
Maron JL, Jeffries RL (2001) Restoring enriched grasslands: effects of mowing on species richness, productivity, and nitrogen retention. Ecol Appl 11:1088–1100
Mitchell CE et al (2006) Biotic interactions and plant invasions. Ecol Lett 9:726–740
Ostertag R, Verville JH (2002) Fertilization with nitrogen and phosphorus increases abundance of non-native species in Hawaiian montane forests. Plant Ecol 162:77–90
Perry LG, Galatowitsch SM, Rosen CJ (2004) Competitive control of invasive vegetation: a native wetland sedge suppresses Phalaris arundinacea in carbon-enriched soil. J Appl Ecol 41:151–162
Rice KJ, Nagy ES (2000) Oak canopy effects on the distribution patterns of two annual grasses: the role of competition and soil nutrients. Am J Bot 87:1699–1706
Roemer HL (1972) Forest vegetation and environments on the Saanich Peninsula. Ph.D. thesis, University of Victoria, Victoria
SAS Institute (2003) SAS for Windows 9.1.3 Service Pack 4
Sauer JR, Hines JE, Fallon J (2005) The North American breeding bird survey, results and analysis 1966–2005. Version 6.2.2006. USGS Patuxent Wildlife Research Center, Laurel
Schippers P, Joenje W (2002) Modelling the effect of fertiliser, mowing, disturbance and width on the biodiversity of plant communities of field boundaries. Agric Ecosyst Environ 93:351–365
Tilman D (1988) Plant strategies and the dynamics and structure of plant communities. Princeton University Press, Princeton
Titman D (1976) Ecological competition between algae: experimental confirmation of resource-based competition theory. Science 192:463–465
Van Vliet LJP, Kenney EA, Green AJ (1991) Soils of the Gulf Islands of British Columbia: soils of Sidney, James, Moresby, Portland, and lesser islands. Report no. 43, vol 5. British Columbia Soil Survey. Research Branch, Agriculture Canada, Ottawa
Ward P, Radcliffe G, Kirkby J, Illingworth J, Cadrin C (1998) Sensitive ecosystems inventory: East Vancouver Island and Gulf Islands, 1993–1997, vol 1. Methodology, ecological descriptions and results. Canadian Wildlife Service, Pacific and Yukon Region, Victoria
Wilson SD, Tilman D (1993) Plant competition and resource availability in response to disturbance and fertilization. Ecology 74:599–611
Acknowledgements
I thank P. Arcese, D. S. Srivastava, R. Turkington, A. S. MacDougall, M. Vellend, J. R. McLaren, R. L. Jefferies, R. D. Guy, and two anonymous reviewers for helpful comments on methodology and the manuscript. I thank D. Kaplan, N. Diner, M. Flint, and J. Muir for assistance in the greenhouse, and M. Flint for assistance in the field. I thank the Gulf Islands National Park Reserve for seed collection permits and, especially, A. J. Brumbaum, W. Hesse and H. Hesse for their very generous contributions to this research. I received funding support from an NSERC Research Scholarship and the UBC Faculty of Forestry. All research described here is in compliance with Canadian law.
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Communicated by Miguel Franco.
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Best, R.J. Exotic grasses and feces deposition by an exotic herbivore combine to reduce the relative abundance of native forbs. Oecologia 158, 319–327 (2008). https://doi.org/10.1007/s00442-008-1137-4
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DOI: https://doi.org/10.1007/s00442-008-1137-4