Advertisement

Oecologia

, Volume 156, Issue 4, pp 825–834 | Cite as

Spatial heterogeneity and plant species richness at different spatial scales under rabbit grazing

  • J. Olofsson
  • C. de Mazancourt
  • M. J. Crawley
Plant-Animal Interactions - Original Paper

Abstract

Herbivores influence spatial heterogeneity in soil resources and vegetation in ecosystems. Despite increasing recognition that spatial heterogeneity can drive species richness at different spatial scales, few studies have quantified the effect of grazing on spatial heterogeneity and species richness simultaneously. Here we document both these variables in a rabbit-grazed grassland. We measured mean values and spatial patterns of grazing intensity, rabbit droppings, plant height, plant biomass, soil water content, ammonia and nitrate in sites grazed by rabbits and in matched, ungrazed exclosures in a grassland in southern England. Plant species richness was recorded at spatial scales ranging between 0.0001 and 150 m2. Grazing reduced plant height and plant biomass but increased levels of ammonia and nitrate in the soil. Spatial statistics revealed that rabbit-grazed sites consisted of a mixture of heavily grazed patches with low vegetation and nutrient-rich soils (lawns) surrounded by patches of high vegetation with nutrient-poor soils (tussocks). The mean patch size (range) in the grazed controls was 2.1 ± 0.3 m for vegetation height, 3.8 ± 1.8 m for soil water content and 2.8 ± 0.9 m for ammonia. This is in line with the patch sizes of grazing (2.4 ± 0.5 m) and dropping deposition (3.7 ± 0.6 m) by rabbits. In contrast, patchiness in the ungrazed exclosures had a larger patch size and was not present for all variables. Rabbit grazing increased plant species richness at all spatial scales. Species richness was negatively correlated with plant height, but positively correlated to the coefficient of variation of plant height at all plot sizes. Species richness in large plots (<25 m2) was also correlated to patch size. This study indicates that the abundance of strong competitors and the nutrient availability in the soil, as well as the heterogeneity and spatial pattern of these factors may influence species richness, but the importance of these factors can differ across spatial scales.

Keywords

Spatial heterogeneity Species richness Herbivory Rabbit grazing 

Notes

Acknowledgements

The work was funded by The Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning and the Swedish Foundation for International Cooperation in Research and Higher Education. The rabbit exclosures are part of a network of long-term field studies in Silwood Park maintained by the Division of Biology, Imperial College London.

References

  1. Adler PB, Raff DA, Lauenroth WK (2001) The effect of grazing on the spatial heterogeneity of vegetation. Oecologia 128:465–479CrossRefGoogle Scholar
  2. Anderson TM, McNaughton SJ, Ritchie ME (2004) Scale-dependent relationships between the spatial distribution of a limiting resource and plant species diversity in an African grassland ecosystem. Oecologia 139:277–287PubMedCrossRefGoogle Scholar
  3. Augustine DJ (2004) Spatial heterogeneity in the herbaceous layer of a semi-arid savanna ecosystem. Plant Ecol 167:319–332CrossRefGoogle Scholar
  4. Augustine DJ, Frank DA (2001) Effects of migratory grazers on spatial heterogeneity of soil nitrogen properties in a grassland ecosystem. Ecology 82:3149–3162Google Scholar
  5. Bakker ES, Reiffers RC, Olff H, Gleichman JM (2005) Experimental manipulation of predation risk and food quality: effect on grazing behaviour in a central-place foraging herbivore. Oecologia 146:157–167PubMedCrossRefGoogle Scholar
  6. Bakker ES, Ritchie ME, Olff H, Milchunas DG, Knops JHM (2006) Herbivore impact on grassland plant diversity depends on habitat productivity and herbivore size. Ecol Lett 9:780–788PubMedCrossRefGoogle Scholar
  7. Burrough PA (1983) Multiscale sources of spatial variation in soil. II. A non-Brownian fractal model and its application in soil survey. J Soil Sci 43:599–620CrossRefGoogle Scholar
  8. Chaneton EJ, Facelli JM (1991) Disturbance effects on plant community diversity: spatial scales and dominance hierarchies. Vegetatio 93:143–156CrossRefGoogle Scholar
  9. Chesson P (1994) Multispecies competition in variable environments. Theor Popul Biol 45:227–276CrossRefGoogle Scholar
  10. Chesson P (2000) Mechanisms of maintenance of species diversity. Annu Rev Ecol Evol Syst 31:343–366CrossRefGoogle Scholar
  11. Cid MS, Brizuela MA (1998) Heterogeneity in tall festuce pastures created and sustained by cattle grazing. J Range Manage 51:644–649CrossRefGoogle Scholar
  12. Connolly SR, Roughgarden J (1999) Theory of marine communities: competition, predation, and recruitment-dependent interaction strength. Ecol Monogr 69:277–296Google Scholar
  13. Crawley MJ (1983) Herbivory: the dynamics of animal–plant interactions. Blackwell, OxfordGoogle Scholar
  14. Crawley MJ (1990) Rabbit grazing, plant competition and seedling recruitment in acid grasslands. J Appl Ecol 27:803–820CrossRefGoogle Scholar
  15. Crawley MJ (2002) Statistical computing: an introduction to data analysis using S-plus. Wiley, ChichesterGoogle Scholar
  16. Crawley MJ (2005) The flora of berkshire. Brambleby Books, HarpendenGoogle Scholar
  17. Crawley MJ, Harral JE (2001) Scale dependence in plant biodiversity. Science 291:864–868PubMedCrossRefGoogle Scholar
  18. Gibson CWD, Brown VK (1991) The effects of grazing on local colonization and extinction during early succession. J Veg Sci 2:291–300CrossRefGoogle Scholar
  19. Glenn SM, Collins SL (1992) Effects of scale and disturbance on rates of immigration and extinction of species in praries. Oikos 63:273–280CrossRefGoogle Scholar
  20. Harper JL (1969) The role of predation in vegetational diversity. In: Brookhaven symposium in biology n0. 22: diversity and stability in ecological systems. Brookhaven National Laboratory, Upton, pp 48–62Google Scholar
  21. Hope-Simpson J (1940) Studies of the vegetation of the English chalk. VI. Late stages in succession leading to chalk grassland. J Ecol 28:386–402CrossRefGoogle Scholar
  22. Huston M (1980) Soil nutrients and tree species richness in Costa Rican forests. J Biogeogr 7:147–157CrossRefGoogle Scholar
  23. Iason GR, Manso T, Sim DA, Hartley FG (2002) The functional response does not predict the local distribution of European rabbits (Oryctolagus cuniculus) on grass swards: experimental evidence. Funct Ecol 16:394–402CrossRefGoogle Scholar
  24. Kohn DD, Walsh DM (1994) Plant species richness: the effects of island size and habitat diversity. J Ecol 82:367–377CrossRefGoogle Scholar
  25. McNaughton SJ (1984) Grazing lawns: animals in herds, plant form, and coevolution. Am Nat 124:863–886CrossRefGoogle Scholar
  26. McNaughton SJ, Banyinkwa FF, McNaughton MM (1997) Promotion of the cycling of diet-enhancing nutrients by African grazers. Science 278:1798–2000PubMedCrossRefGoogle Scholar
  27. Olff H, Ritchie ME (1998) Effects of herbivores on grassland plant diversity. Trends Ecol Evol 13:261–265CrossRefGoogle Scholar
  28. Olofsson J, de Mazancourt C, Crawley MJ (2007) Contrasting effects of rabbit exclusion on nutrient availability and primary production in grasslands at different time scales. Oecologia 150:582–589PubMedCrossRefGoogle Scholar
  29. Pacala SW, Tilman D (1994) Limiting similarity in mechanistic and spatial models of plant competition in heterogeneous environments. Am Nat 143:222–257CrossRefGoogle Scholar
  30. Palmer MW (1988) Fractal geometry—a tool for describing spatial patterns of plant communities. Vegetatio 75:91–102CrossRefGoogle Scholar
  31. Pastor J, Dewey B, Moen R, Mladenoff DJ, White M, Cohen Y (1998) Spatial patterns in the moose-forest-soil ecosystem on Isle Royale, Michigan, USA. Ecol Appl 8:411–424Google Scholar
  32. Posse G, Anchorena J, Collantes MB (2000) Spatial micro-patterns in the steppe of Tierra del Fuego induced by sheep grazing. J Veg Sci 11:43–50CrossRefGoogle Scholar
  33. Proulx M, Mazumder A (1998) Reversal of grazing impact on plant species richness in nutrient-poor vs. nutrient-rich ecosystems. Ecology 79:2581–2592CrossRefGoogle Scholar
  34. R development Core Team (2006) R: a language and environment for statistical computing. R foundation for statistical computing, Vienna, Austria. ISBN 3-900051-07-0. http://www.R-project.org
  35. Ribeiro PJ Jr, Diggle PJ (2001) geoR: a package for geostatistical analysis. R News 1:15–18Google Scholar
  36. Ring CB, Nicholson RA, Launchbaugh JL (1985) Vegetational traits of patch grazed rangelands in west-central Kansas. J Range Manage 38:51–55CrossRefGoogle Scholar
  37. Ritchie ME, Olff H (1999) Spatial scaling laws yield a synthetic theory of biodiversity. Nature 400:557–560PubMedCrossRefGoogle Scholar
  38. Robertson GP, Gross KL (1994) Assessing the heterogeneity of belowground resources: quantifying pattern and scale. In: Cladwell MM, Pearcy RW (eds) Exploitation of environmental heterogeneity by plants: ecophysiological processes above- and belowground. Academic Press, San DiegoGoogle Scholar
  39. Robinson M, Dean TJ (1993) Measurement of near surface soil water content using a capacity probe. Hydrol Proc 7:77–86CrossRefGoogle Scholar
  40. Rosenzweig ML (1995) Species diversity in space and time. Cambridge University Press, CambridgeGoogle Scholar
  41. Starr DA, Hibbs DE, Huston MA (2005) A hierarchical perspective of plant diversity. Q Rev Biol 80:187–212CrossRefGoogle Scholar
  42. Stohlgren TJ, Schell LD, Heuvel BV (1999) How grazing and soil quality affect native and exotic plant diversity in Rocky Mountain grasslands. Ecol Appl 9:45–65CrossRefGoogle Scholar
  43. Sugihara G, May RM (1990) Applications of fractals in ecology. Trends Ecol Evol 5:79–86CrossRefGoogle Scholar
  44. Tansley AG, Adamson RS (1925) Studies of the vegetation of the English chalk. II. The chalk grasslands of Hampshire–Sussex border. J Ecol 13:177–223CrossRefGoogle Scholar
  45. Thomas AS (1960) Changes in the vegetation since the advent of myxomatosis. J Ecol 48:287–306CrossRefGoogle Scholar
  46. Zar JH (1996) Biostatistical analysis. Prentice Hall, New JerseyGoogle Scholar

Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  • J. Olofsson
    • 1
    • 2
  • C. de Mazancourt
    • 1
    • 3
  • M. J. Crawley
    • 1
  1. 1.Division of BiologyImperial College LondonAscotUK
  2. 2.Department of Ecology and Environmental ScienceUmeå UniversityUmeåSweden
  3. 3.Redpath MuseumMcGill UniversityMontrealCanada

Personalised recommendations