Abstract
We examined how water and nitrogen addition and water–nitrogen interactions affect root and shoot competition intensity and competition–productivity relationships in a native rough fescue grassland in central Alberta, Canada. Water and nitrogen were added in a factorial design to plots and root exclusion tubes and netting were used to isolate root and shoot competition on two focal species (Artemisia frigida and Chenopodium leptophyllum). Both water and nitrogen were limiting to plant growth, and focal plant survival rates increased with nitrogen but not water addition. Relative allocation to root biomass increased with water addition. Competition was almost entirely belowground, with focal plants larger when released from root but not shoot competition. There were no significant relationships between productivity and root, shoot, or total competition intensity, likely because in this system shoot biomass was too low to cause strong shoot competition and root biomass was above the levels at which root competition saturates. Water addition had few effects on the intensity of root competition suggesting that root competition intensity is invariant along soil moisture gradients. Contrary to general expectation, the strength of root competition increased with nitrogen addition demonstrating that the relationship between root competition intensity and nitrogen is more complex than a simple monotonic decline as nitrogen increases. Finally, there were few interactions between nitrogen and water affecting competition. Together these results indicate that the mechanisms of competition for water and nitrogen likely differ.
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References
Arii K, Turkington R (2001) Assessing competition intensity along productivity gradients using a simple model. Can J Bot 79:1486–1491
Belcher JW, Keddy PA, Twolan-Strutt L (1995) Root and shoot competition intensity along a soil depth gradient. J Ecol 83:673–682
Bertiller MB, Zaixso P, Irisarri MD, Brevedan ER (1996) Establishment of Festuca pallescens in arid grasslands in Patagonia (Argentina): the effect of soil water stress. J Arid Environ 32:161–171
Booth MS, Stark JM, Rastetter E (2005) Controls on nitrogen cycling in terrestrial ecosystems: a synthetic analysis of literature data. Ecol Monogr 75:139–157
Brewer JS (2003) Nitrogen addition does not reduce belowground competition in a salt marsh clonal plant community in Mississippi (USA) . Plant Ecol 168:93–106
Briones O, Montańa C, Ezcurra E (1998) Competition intensity as a function of resource availability in a semiarid ecosystem. Oecologia 116:365–372
Burger JC, Louda SM (1995) Interaction of diffuse competition and insect herbivory in limiting brittle prickly pear cactus, Opuntia fragilis (Cactaceae). Am J Bot 82:1558–1566
Cahill JF (1999) Fertilization effects on interactions between above- and belowground competition in an old field. Ecology 80:466–480
Cahill JF (2002a) Interactions between root and shoot competition vary among species. Oikos 99:101–112
Cahill JF (2002b) What evidence is necessary in studies which separate root and shoot competition along productivity gradients. J Ecol 90:201–205
Cahill JF (2003a) Lack of relationship between below-ground competition and allocation to roots in 10 grassland species. J Ecol 91:532–540
Cahill JF (2003b) Neighbourhood-scale diversity, composition and root crowding do not alter competition during drought in a native grassland. Ecol Lett 6:599–603
Cahill JF, Casper BB (2000) Investigating the relationship between neighbor root biomass and belowground competition: field evidence for symmetric competition belowground. Oikos 90:311–320
Casper BB, Jackson RB (1997) Plant competition underground. Ann Rev Ecol Syst 28:545–570
Corcket E, Liancourt P, Callaway RM, Michalet R (2003) The relative importance of competition for two dominant grass species as affected by environmental manipulations in the field. Écoscience 10:186–194
Craine JM (2005) Reconciling plant strategy theories of Grime and Tilman. J Ecol 93:1041–1052
Davis MA, Wrage KJ, Reich PB (1998) Competition between tree seedlings and herbaceous vegetation: support for a theory of resource supply and demand. J Ecol 86:652–661
Davis MA, Wrage KJ, Reich PB, Tjoelker MG, Schaeffer T, Muermann C (1999) Survival, growth, and photosynthesis of tree seedlings competing with herbaceous vegetation along a water-light-nitrogen gradient. Plant Ecol 145:341–350
Dell CJ, Rice CW (2005) Short-term competition for ammonium and nitrate in tallgrass prairie. Soil Sci Soc Am J 69:371–377
Engqvist L (2005) The mistreatment of covariate interaction terms in linear model analyses of behavioural and evolutionary ecology studies. Anim Behav 70:967–971
Fitter AH, Hay RKM (2002) Environmental physiology of plants. Academic Press, London
Fynn RWS, Morris CD, Kirkman KP (2005) Plant strategies and trade-offs influence trends in competitive ability along gradients of soil fertility and disturbance. J Ecol 93:384–394
Gersani M, Brown JS, O’Brien EE, Mania GM, Abramsky Z (2001) Tragedy of the commons as a result of root competition. J Ecol 89:660–669
Goldberg DE, Barton AM (1992) Patterns and consequences of interspecific competition in natural communities: a review of field experiments with plants. Am Nat 139:771–801
Goldberg D, Novoplansky A (1997) On the relative importance of competition in unproductive environments. J Ecol 85:409–418
Grime JP (1973) Competitive exclusion in herbaceous vegetation. Nature 242:344–347
Grime JP (2001) Plant strategies, vegetation processes, and ecosystem properties. John Wiley and Sons, Chichester
Haugland E, Froud-Williams RJ (1999) Improving grasslands: the influence of soil moisture and nitrogen fertilization on the establishment of seedlings. J Appl Ecol 36:263–270
Hedges LV, Gurevitch J, Curtis PS (1999) The meta-analysis of response ratios in experimental ecology. Ecology 80:1150–1156
Howitt RW (1988) Soil survey or the county of Beaver, Alberta. Terrain Sciences Department, Alberta Research Council, Edmonton Alberta Canada
Jackson LE, Schimel JP, Firestone MK (1989) Short-term partitioning of ammonium and nitrate between plants and microbes in an annual grassland. Soil Biol Biochem 21:409–415
James JJ, Richards JH (2005) Plant N capture from pulses: effects of pulse size, growth rate, and other soil resources. Oecologia 145:113–122
Kadmon R (1995) Plant competition along soil moisture gradients: a field experiment with the desert annual Stipa capensis. J Ecol 83:253–262
Keddy PA (2001) Competition. Kluwer, Dordrecht
Lamb EG, Cahill JF, Dale MRT (2006) A nonlinear regression approach to test for size-dependence of competitive ability. Ecology 87:1452–1457
Liancourt P, Corcket E, Michalet R (2005) Stress tolerance abilities and competitive responses in a watering and fertilization field experiment. J Veg Sci 16:713–722
Newman EI (1973) Competition and diversity in herbaceous vegetation. Nature 244:310
Novoplansky A, Goldberg DE (2001) Effects of water pulsing on individual performance and competitive hierarchies in plants. J Veg Sci 12:199–208
Peltzer DA, Wilson SD, Gerry AK (1998) Competition intensity along a productivity gradient in a low-diversity grassland. Am Nat 151:465–476
Poorter H, Nagel O (2000) The role of biomass allocation in the growth response of plants to different levels of light, CO2, nutrients, and water: a quantitative review. Aust J Plant Phys 27:595–607
Pregitzer KS, Hendrick RL, Fogel R (1993) The demography of fine roots in response to patches of water and nitrogen. New Phytol 125:575–580
Pucheta E, Bonamici I, Cabido M, Diaz S (2004) Below-ground biomass and productivity of a grazed site and a neighbouring ungrazed exclosure in a grassland in central Argentina. Austral Ecol 29:201–208
Reynolds HL, D’Antonio C (1996) The ecological significance of plasticity in root weight ratio in response to nitrogen: opinion. Plant Soil 185:75–97
Sammul M, Oksanen L, Mägi M. (2006) Regional effects on competition-productivity relationship: a set of field experiments in two distant regions. Oikos 112:138–148
Santos BM, Dusky JA, Stall WM, Bewick TA, Shilling DG (2004) Mechanisms of interference of smooth pigweed (Amaranthus hybridus) and common purslane (Portulaca oleracea) on lettuce as influenced by phosphorus fertility. Weed Sci 52:78–82
SAS (2004) SAS/STAT 9.1 Users guide. SAS Institute Inc., Cary NC USA
Schenk HJ (2006) Root competition: beyond resource depletion. J Ecol 94:725–739
Schwinning S, Weiner J (1998) Mechanisms determining the degree of size asymmetry in competition among plants. Oecologia 113:447–455
Semere T, Froud-Williams RJ (2001) The effect of pea cultivar and water stress on root and shoot competition between vegetative plants of maize and pea. J Appl Ecol 38:137–145
Sims PL, Risser PG (2000) Grasslands. In: Barbour MG, Billings WD (eds) North American terrestrial vegetation. Cambridge University Press, Cambridge UK, pp 324–356
Taylor DR, Aarssen LW, Loehle C (1990) On the relationship between r/K selection and environmental carrying-capacity – a new habitat templet for plant life-history strategies. Oikos 58:239–250
Tilman D (1988) Plant strategies and the dynamics and structure of plant communities. Princeton University Press, Princeton New Jersey
Twolan-Strutt L, Keddy PA (1996) Above- and belowground competition intensity in two contrasting wetland plant communities. Ecology 77:259–270
Weigelt A, Jolliffe P (2003) Indices of plant competition. J Ecol 91:707–720
Weigelt A, Röttgermann M, Steinlein T, Beyschlag W (2000) Influence of water availability on competitive interactions between plant species on sandy soils. Folia Geobot 35:169–178
Weigelt A, Steinlein T, Beyschlag W (2005) Competition among three dune species: the impact of water availability on below-ground processes. Plant Ecol 176:57–68
Wetzel PR, van der Valk AG (1998) Effects of nutrient and soil moisture on competition between Carex stricta, Phalaris arundinacea, and Typha latifolia. Plant Ecol 138:179–190
Wilson SD, Tilman D (1991) Components of plant competition along an experimental gradient of nitrogen availability. Ecology 72:1050–1065
Wilson SD, Tilman D (1993) Plant competition and resource availability in response to disturbance and fertilization. Ecology 74:599–611
Wilson SD, Tilman D (1995) Competitive responses of eight old-field plant species in four environments. Ecology 76:1169–1180
Acknowledgements
We thank D. Gabruck, S. Roehr, A. Pfeiffer, and N. Fernando for assistance in the field, the Cahill lab group, K. Ketilson, and an anonymous reviewer for helpful suggestions. Financial support came from an Alberta Ingenuity studentship to E.G.L., an NSERC PGS-M scholarship to B.H.S., an Alberta Conservation Association Biodiversity grant to E.G.L. and J.F.C., and an NSERC Discovery grant to J.F.C.
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Lamb, E.G., Shore, B.H. & Cahill, J.F. Water and nitrogen addition differentially impact plant competition in a native rough fescue grassland. Plant Ecol 192, 21–33 (2007). https://doi.org/10.1007/s11258-006-9222-4
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DOI: https://doi.org/10.1007/s11258-006-9222-4