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Positive interactions among alpine plants increase with stress


Plants can have positive effects on each other1. For example, the accumulation of nutrients, provision of shade, amelioration of disturbance, or protection from herbivores by some species can enhance the performance of neighbouring species. Thus the notion that the distributions and abundances of plant species are independent of other species may be inadequate as a theoretical underpinning for understanding species coexistence and diversity2. But there have been no large-scale experiments designed to examine the generality of positive interactions in plant communities and their importance relative to competition. Here we show that the biomass, growth and reproduction of alpine plant species are higher when other plants are nearby. In an experiment conducted in subalpine and alpine plant communities with 115 species in 11 different mountain ranges, we find that competition generally, but not exclusively, dominates interactions at lower elevations where conditions are less physically stressful. In contrast, at high elevations where abiotic stress is high the interactions among plants are predominantly positive. Furthermore, across all high and low sites positive interactions are more important at sites with low temperatures in the early summer, but competition prevails at warmer sites.

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Figure 1: Relative neighbour effect (RNE) at the 11 experimental sites.
Figure 2: Proportion of surviving target species in controls and neighbour removal treatments at high and low elevation experimental sites for all 11 locations combined.
Figure 3: Proportion of flowering or fruiting target species in controls and neighbour removal treatments at high and low elevation experimental sites for all 11 locations combined.
Figure 4: The relationship between relative neighbour effect (RNE) and the estimated maximum temperature in early summer (June in the Northern Hemisphere and December in the Southern Hemisphere) at each of the 22 experimental sites.


  1. 1

    Callaway, R. M. Positive interactions among plants. Bot. Rev. 61, 306–349 (1995)

    Article  Google Scholar 

  2. 2

    Callaway, R. M. Positive interactions in plant communities and the individualistic-continuum concept. Oecologia 112, 143–149 (1997)

    ADS  Article  Google Scholar 

  3. 3

    Berlow, E. L. Strong effects of weak interactions in ecological communities. Nature 398, 330–334 (1999)

    ADS  CAS  Article  Google Scholar 

  4. 4

    Miller, T. E. Direct and indirect species interactions in an early old-field plant community. Am. Nat. 143, 1007–1025 (1994)

    Article  Google Scholar 

  5. 5

    Grime, J. P. Evidence for the existence of three primary strategies in plants and its relevance to ecological and evolutionary theory. Am. Nat. 111, 1169–1194 (1977)

    Article  Google Scholar 

  6. 6

    Connell, J. H. On the prevalence and relative importance of interspecific competition: evidence from field experiments. Am. Nat. 122, 661–696 (1983)

    Article  Google Scholar 

  7. 7

    Pugnaire, F. I. & Luque, M. T. Changes in plant interactions along a gradient of environmental stress. Oikos 93, 42–49 (2000)

    Article  Google Scholar 

  8. 8

    Brooker, R. W. & Callaghan, T. V. The balance between positive and negative plant interactions and its relationship to environmental gradients: a model. Oikos 81, 196–207 (1998)

    Article  Google Scholar 

  9. 9

    Bertness, M. D. & Callaway, R. M. Positive interactions in communities. Trends Ecol. Evol. 9, 191–193 (1995)

    Article  Google Scholar 

  10. 10

    Markham, J. H. & Chanway, C. P. Measuring plant neighbor effects. Funct. Ecol. 10, 548–549 (1996)

    Google Scholar 

  11. 11

    Grime, J. P. Plant Strategies and Vegetation Processes (Wiley, Chichester, 1979)

    Google Scholar 

  12. 12

    Dodds, W. K. Interspecific interactions: constructing a general neutral model for interaction type. Oikos 78, 377–383 (1997)

    Article  Google Scholar 

  13. 13

    Woodward, F. I., Smith, T. M. & Emanuel, W. R. A global primary productivity and phytogeography model. Glob. Biogeochem. Cycles 9, 471–490 (1995)

    ADS  CAS  Article  Google Scholar 

  14. 14

    Shaver, G. R. & Jonasson, S. Response of arctic ecosystems to climate change: result of long-term field experiments in Sweden and Alaska. Polar Res. 18, 245–256 (1999)

    Article  Google Scholar 

  15. 15

    Prentice, C. I. et al. A global biome model based on plant physiology and dominance, soil properties, and climate. J. Biogeogr. 19, 117–134 (1992)

    Article  Google Scholar 

  16. 16

    Gleason, H. A. The individualist concept of the plant association. Bull. Torrey Bot. Club 53, 7–27 (1926)

    Article  Google Scholar 

  17. 17

    Whittaker, R. H. Communities and Ecosystems (Macmillan, New York, 1975)

    Google Scholar 

  18. 18

    Begon, M., Harper, J. L. & Townsend, C. R. Ecology 2nd edn 626–628 (Blackwell, London, 1990)

    Google Scholar 

  19. 19

    Johnson, H. B. & Mayeux, H. S. Viewpoint: a view on species additions and deletions and the balance of nature. J. Range Manag. 45, 322–333 (1992)

    Article  Google Scholar 

  20. 20

    Curtis, J. T. The Vegetation of Wisconsin (Univ. Wisconsin Press, Madison, 1959)

    Google Scholar 

  21. 21

    Whittaker, R. H. A consideration of climax theory: the climax as population and pattern. Ecol. Monogr. 23, 41–78 (1953)

    Article  Google Scholar 

  22. 22

    Austin, M. P. Continuum concept, ordination methods, and niche theory. Annu. Rev. Ecol. Syst. 16, 39–61 (1985)

    Article  Google Scholar 

  23. 23

    Callaway, R. M. Are positive interactions species-specific? Oikos 82, 202–209 (1998)

    Article  Google Scholar 

  24. 24

    Choler, P., Michalet, R. & Callaway, R. M. Facilitation and competition on gradients in alpine plant communities. Ecology 82, 3295–3308 (2001)

    Article  Google Scholar 

  25. 25

    Archibold, O. W. Ecology of World Vegetation 280–318 (Chapman and Hall, London, 1995)

    Google Scholar 

  26. 26

    JMPin 4.0.2 (SAS Institute Inc., Duxbury Press, Cary, North Carolina, 2000)

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We thank the National Center for Ecological Synthesis and Analysis, The National Geographic Society, the Civilian Research and Development Foundation, and the Andrew W. Mellon Foundation for financial support.

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Correspondence to Ragan M. Callaway.

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The authors declare that they have no competing financial interests.

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Callaway, R., Brooker, R., Choler, P. et al. Positive interactions among alpine plants increase with stress. Nature 417, 844–848 (2002).

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