Journal of Mountain Science

, Volume 13, Issue 7, pp 1154–1161 | Cite as

A size-gradient hypothesis for alpine treeline ecotones

Article

Abstract

Research on the stress gradient hypothesis recognizes that positive (i.e. facilitative) and negative (i.e. competitive) plant interactions change in intensity and effect relative to abiotic stress experienced on a gradient. Motivated by observations of alpine treeline ecotones, we suggest that this switch in interaction could operate along a gradient of relative size of individual plants. We propose that as neighbors increase in size relative to a focal plant they improve the environment for that plant up to a critical point. After this critical point is surpassed, however, increasing relative size of neighbors will degrade the environment such that the net interaction intensity becomes negative. We developed a conceptual (not site or species specific) individual based model to simulate a single species with recruitment, growth, and mortality dependent on the environment mediated by the relative size of neighbors. Growth and size form a feedback. Simulation results show that the size gradient model produces metrics similar to that of a stress gradient model. Visualizations reveal that the size gradient model produces spatial patterns that are similar to the complex ones observed at alpine treelines. Size-mediated interaction could be a mechanism of the stress gradient hypothesis or it could operate independent of abiotic stress.

Keywords

Competition Ecotone Environmental gradient Plant interaction Stress gradient Facilitation 

References

  1. Berger U, Piou C, Schiffers K, Grimm V (2008) Competition among plants: Concepts, individual-based modelling approaches, and a proposal for a future research strategy. Perspectives in Plant Ecology Evolution and Systematics 9: 121–135. DOI: 10.1016/j.ppees.2007.11.002CrossRefGoogle Scholar
  2. Bertness MD, Callaway R (1994) Positive interactions in communities. Trends in Ecology and Evolution 9: 191–193. DOI: 10.1016/0169-5347(94)90088-4CrossRefGoogle Scholar
  3. Bittebierea AK, Monya C, Clémenta B, et al. (2012) Modeling competition between plants using an Individual Based Model: Methods and effects on the growth of two species with contrasted growth forms. Ecological Modelling 234(10): 38–50. DOI: 10.1016/j.ecolmodel.2011.05.028CrossRefGoogle Scholar
  4. Brathen KA, Lortie C (2016) A portfolio effect of shrub canopy height on species richness in both stressful and competitive environments. Functional Ecology 30: 60–69. DOI: 10.1111/1365-2435.12458CrossRefGoogle Scholar
  5. Buenau KE, Price NN, Nisbet RM (2012) Size dependence facilitation and microhabitats mediate space competition between coral and crustose coralline algae in a spatially explicit model. Ecological Modelling 237: 23–33. DOI: 10.1016/j.ecolmodel.2012.04.013CrossRefGoogle Scholar
  6. Butterfield BJ, Callaway RM (2013) A functional comparative approach to facilitation and its context dependence. Functional Ecology 27: 907–917. DOI: 10.1111/1365-2435.12019CrossRefGoogle Scholar
  7. Cairns DM (2005) Simulating carbon balance at treeline for krummholz and dwarf tree growth forms. Ecological Modelling 187: 314–328. DOI: 10.1016/j.ecolmodel.2005.01.041CrossRefGoogle Scholar
  8. Callaway RM (2007) Positive interactions and interdependence in plant communities. Dordrecht: Springer. p 404. DOI: 10.1007/978-1-4020-6224-7Google Scholar
  9. Chen JG, Yang Y, Stocklin J, et al. (2015) Soil nutrient availability determines the facilitative effects of cushion plants on other plant species at high elevations in the southeastern Himalayas. Plant Ecology and Diversity 8: 199–210. DOI: 10.1080/17550874.2013.872206CrossRefGoogle Scholar
  10. Cowles JM, Wragg PD, Wright AJ, et al. (2016) Shifting grassland plant community structure drives positive interactive effects of warming and diversity on aboveground net primary productivity. Global Change Biology 22: 741–749. DOI: 10.1111/gcb.13111CrossRefGoogle Scholar
  11. Germino MJ, Smith WK (1999) Sky exposure, crown architecture, and low-temperature photoinhibition in conifer seedlings at alpine treeline. Plant Cell and Environment 22: 407–415. DOI: 10.1046/j.1365-3040.1999.00426.xCrossRefGoogle Scholar
  12. Holtmeier FK, Broll G (2010) Wind as an ecological agent at treelines in North Americathe Alps and the European subarctic. Physical Geography 31: 203–233. DOI: 10.2747/0272-3646.31.3.203CrossRefGoogle Scholar
  13. Korner C (1998) A re-assessment of high elevation treeline positions and their explanation. Oecologia 115: 445–459. DOI: 10.1007/s004420050540CrossRefGoogle Scholar
  14. Korner C (2016) When it gets cold, plant size matters - a comment on treeline. Journal of Vegetation Science 27: 6–7. DOI: 10.1111/jvs.12366CrossRefGoogle Scholar
  15. Jia X, Dai XF, Shen ZX, et al. (2011) Facilitation can maintain clustered spatial pattern of plant populations during densitydependent mortality: insights from a zone-of-influence model. Oikos 120: 472–480. DOI: 10.1111/j.1600-0706.2010.18674.xCrossRefGoogle Scholar
  16. Le Roux PC, McGeoch MA (2008) Spatial variation in plant interactions across a severity gradient in the sub-Antarctic. Oecologia 155: 831–844. DOI: 10.1007/s00442-007-0954-1CrossRefGoogle Scholar
  17. Le Roux PC, Shaw JD, Chown SL (2013) Ontogenetic shifts in plant interactions vary with environmental severity and affect population structure. New Phytologist 200: 241–250. DOI: 10.1111/nph.12349CrossRefGoogle Scholar
  18. Lin Y, Berger U, Grimm V, Ji QR (2011) Differences between symmetric and asymmetric facilitation matter: exploring the interplay between modes of positive and negative interactions. Journal of Ecology 100: 1482–1491. DOI: 10.1111/j.1365-2745.2012.02019.xCrossRefGoogle Scholar
  19. Luo Y, Chen HYH (2011) Competition, species interaction and ageing control tree mortality in boreal forests. Journal of Ecology 99: 1470–1480.DOI:10.1111/j.1365-2745.2011.01882.xCrossRefGoogle Scholar
  20. Mack RN, Harper JL (1977) Interference in dune annuals: spatial pattern and neighbourhood effects. Journal of Ecology 65: 345–363. DOI: 10.2307/2259487CrossRefGoogle Scholar
  21. Maestre FT, Callaway RM, Valladares F, Lortie CJ (2009) Refining the stress-gradient hypothesis for competition and facilitation in plant communities. Journal of Ecology 97: 199–205. DOI: 10.1111/j.1365-2745.2008.01476.xCrossRefGoogle Scholar
  22. Malanson GP (2015) Diversity differs among three variations of the stress gradients hypothesis in two representations of niche space. Journal of Theoretical Biology 384: 121–130. DOI: 10.1016/j.jtbi.2015.08.012CrossRefGoogle Scholar
  23. Malanson GP, Resler LM (2015) Neighborhood functions alter unbalanced facilitation on a stress gradient. Journal of Theoretical Biology 365: 76–83. DOI: 10.1016/j.jtbi.2014.10.005CrossRefGoogle Scholar
  24. Malanson GP, Resler LM, Bader MY, et al. (2011) Mountain treelines: a roadmap for research orientation. Arctic Antarctic Alpine Research 43: 167–177. DOI: 10.1657/1938-4246-43.2.167CrossRefGoogle Scholar
  25. McAuliffe JR (1984) Sahuaro-nurse tree associations in the Sonoran Desert: competitive effects of sahuaros. Oecologia 64: 319–321. DOI: 10.1007/BF00379128CrossRefGoogle Scholar
  26. Michalet R, Pugnaire FI (2016) Facilitation in communities: underlying mechanisms, community and ecosystem implications. Functional Ecology 30: 3–9. DOI: 10.1111/1365-2435.12602CrossRefGoogle Scholar
  27. Michalet R, Le Bagousse-Pinguet Y, Maalouf JP, Lortie CJ (2014) Two alternatives to the stress-gradient hypothesis at the edge of life: the collapse of facilitation and the switch from facilitation to competition. Journal Vegetation Science 25: 609–613. DOI: 10.1111/jvs.12123CrossRefGoogle Scholar
  28. Miriti MN (2006) Ontogenetic shift from facilitation to competition in a desert shrub. Journal of Ecology 94: 973–979. DOI: 10.1111/j.1365-2745.2006.01138.xCrossRefGoogle Scholar
  29. Nakagawa Y, Yokozawa M, Hara T (2015) Competition among plants can lead to an increase in aggregation of smaller plants around larger ones. Ecological Modelling 301: 41–53. DOI: 10.1016/j.ecolmodel.2015.01.014CrossRefGoogle Scholar
  30. Rietkerk M, Boerlijst MC, van Langevelde F, et al. (2002) Selforganization of vegetation in arid ecosystems. American Naturalist 160: 524–530. DOI: 10.1086/342078CrossRefGoogle Scholar
  31. Resler LM, Butler DR, Malanson GP (2005) Topographic shelter and conifer establishment and mortality in an alpine environment, Glacier National Park, Montana. Physical Geography 26: 112–125. DOI: 10.2747/0272-3646.26.2.112CrossRefGoogle Scholar
  32. Schob C, Callaway RM, Anthelme F, et al. (2014) The context dependence of beneficiary feedback effects on benefactors in plant facilitation. New Phytologist 204: 386–396. DOI: 10.1111/nph.12908CrossRefGoogle Scholar
  33. Schweiger AH, Otieno DO, Kulunge SR, et al. (2015) The Afroalpine dwarf shrub Helichrysum citrispinum favours understorey plants through microclimate amelioration. Plant Ecology and Diversity 8: 293–303. DOI: 10.1080/17550874.2015.1014207CrossRefGoogle Scholar
  34. Schwinning S, Weiner J (1998) Mechanisms determining the degree of size asymmetry in competition among plants. Oecologia 113: 447–455. DOI: 10.1007/s004420050397CrossRefGoogle Scholar
  35. Smith TB, Wayne RK, Girman DJ, et al. (1997) A role for ecotones in generating rainforest biodiversity. Science 276: 1855–1857CrossRefGoogle Scholar
  36. Soliveres S, Smit C, Maestre FT (2014) Moving forward on facilitation research: response to changing environments and effects on the diversity, functioning and evolution of plant communities. Biological Reviews 90: 297–313. DOI: 10.1111/brv.12110CrossRefGoogle Scholar
  37. Sthultz CM, Gehring CA, Whitham TG (2007) Shifts from competition to facilitation between a foundation tree and a pioneer shrub across spatial and temporal scales in a semiarid woodland. New Phytologist 173: 135–145. DOI: 10.1111/j.1469-8137.2006.01915.xCrossRefGoogle Scholar
  38. Weiner J, Stoll P, Muller-Landau H, Jasentuliyana A (2001) The effects of density, spatial pattern, and competitive symmetry on size variation in simulated plant populations. American Naturalist 158: 438–450. DOI: 10.1086/321988CrossRefGoogle Scholar
  39. White JW, Rassweiler A, Samhouri JF, et al. (2014) Ecologists should not use statistical significance tests to interpret simulation model results. Oikos 123: 385–388. DOI: 10.1111/j.1600-0706.2013.01073.xCrossRefGoogle Scholar
  40. Wilensky U (1999) NetLogo. http://ccl.northwestern.edu/netlogo/. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL USA.Google Scholar
  41. Wilson JB, Agnew ADQ (1992) Positive feedback switches in plant communities. Advances in Ecological Research 23: 263–336 DOI: 10.1016/S0065-2504(08)60149-XCrossRefGoogle Scholar
  42. Wisz MS, Pottier J, Kissling WD, et al. (2013) The role of biotic interactions in shaping distributions and realised assemblages of species: implications for species distribution modelling. Biological Reviews 88: 15–30. DOI: 10.1111/j.1469-185X.2012.00235.xCrossRefGoogle Scholar
  43. Wright A, Schnitzer SA, Reich PB (2014) Living close to your neighbors: the importance of both competition and facilitation in plant communities. Ecology 95: 2213–2223. DOI: 10.1890/13-1855.1CrossRefGoogle Scholar
  44. Xiao S, Chen SY, Wang G (2006) An ESS for the height of a plant population, or an optimal height for an individual? Rethinking game-theoretic models for plant height. Bulletin of Mathematical Biology 68: 957–967. DOI: 10.1007/s11538-006-9073-0CrossRefGoogle Scholar
  45. Xiao S, Michalet R, Wang G, Chen SY (2009) The interplay between species' positive and negative interactions shapes the community biomass-species richness relationship. Oikos 118: 1342–1348. DOI: 10.1111/j.1600-0706.2009.17588.xCrossRefGoogle Scholar

Copyright information

© Science Press, Institute of Mountain Hazards and Environment, CAS and Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  1. 1.Department of Geographical & Sustainability SciencesUniversity of IowaIowa CityUSA
  2. 2.Department of GeographyVirginia TechBlacksburgUSA

Personalised recommendations