Advertisement

Primary Succession on Mount St. Helens: Rates, Determinism, and Alternative States

  • Roger del Moral
  • Jonathan H. Titus
Chapter

Abstract

We explored vegetation recovery on primary surfaces after the 1980 eruption including whether different communities might exist under similar conditions. Data were from repeat sampling of permanent plots, grids and depressions that formed during the eruption (potholes). We assessed succession rates using turnover, community similarity and trajectory complexity. We estimated turnover from community type change, while information theory described trajectory complexity. Similarity between repeat samples assessed succession rate. Succession vectors defined by detrended correspondence analysis (DCA) of repeatedly measured plots assessed floristic change. We determined the degree to which habitat variables predicted species composition using redundancy analysis. We tested the hypothesis that only one CT could occupy a particular habitat type (HT) by comparing species composition within CTs and HTs.

Successional rates declined with increasing elevation, proximity to colonists accelerated succession and succession may be arrested when strong dominants establish quickly. Biotic effects from Lupinus strongly alter successional rates by changing the rules for subsequent invasion. Environmental stress affects seedling establishment (drought) and biomass accumulation (infertility).

We explored the effects of determinant factors. The correspondence between vegetation and predictive factors was initially weak, but sometimes increased, limited by stochastic, transient and contingent effects. Contingent events also limited floristic convergence. Dispersal limitations and priority effects may have limited potential convergence. Unexplained variance in studies of plant to environment relations is largely due to contingent events, unmeasured variables and suboptimal statistical models.

We conducted a search for alternative states. While multiple communities may exist in some habitats, these may converge. Where indications that alternative states exist, more detailed habitat analysis may reveal differences that support alternative communities. Our data suggests that often there is a reasonable correlation between a community and a habitat, thus supporting the single state hypothesis. This long term study on Mount St. Helens provided significant insights into ecosystem recovery processes and has improved restoration methods.

Keywords

Facilitation Floristics Lahar Lupinus lepidus Pyroclastic surfaces safe-sites Stochastic effects Successional trajectories Turnover 

Notes

Acknowledgments

We thank the US National Science Foundation for funding (BSR8906544; DEB9406987, DEB0087040, DEB0541972, and OPUS grant DEB1118593) and the Mount St. Helens NVM for permission to investigate succession. Beth Brosseau, Lars Walker, and Fred Swanson made substantive comments to improve this paper, which is contribution No. 77 to the Mount St. Helens Succession Project. We dedicate this paper to the memory of David M. Wood, friend, colleague, and major contributor to the story of vegetation recovery on Mount St. Helens.

Glossary

Alternative states

Two or more community types found in the same habitat.

Alternative stable states

Two or more community types seeming to persist in the same habitat.

CCA

Canonical correspondence analysis, constrained ordination based on DCA.

Colonization

The process of arrival and establishment, both are selective of species.

Competition

Negative impacts of one species on another due to use of limited resources.

Constrained ordination

Method of describing species patterns in terms of environmental factors.

Convergence

Occurs when two communities become increasingly similar as they mature.

DCA

Detrended correspondence analysis, a method to summarize vegetation change and forming trajectories based on nonlinear assumptions.

Dispersal

The process by which an organism or its reproductive units are transferred between habitats.

Divergent communities

Communities that become increasingly distinct as they mature.

Facilitation

Effects that promote establishment and growth of one species by another.

Euclidean distance, d

A measure of relationship between two samples based on DCA scores: dij = square root [Σ(xik – xjk)2], i and j are values in two samples, and k = number of species over which the comparison is made.

Habitat complexity

A measure of the number of CTs and their residence time calculated by the Shannon information statistic H′ = –Σ pi log pi; pi is the proportion of time occupied by each CT.

Habitat type

Environmental unit based on available habitat values.

Lahar

A slurry of mud and debris, here resulting from melting ice during an eruption.

Microsite

Small-scale habitat (see safe-sites).

Mosaic

A patchwork of vegetation on the landscape.

Mycorrhizae

Fungi that form mutualistic interactions with roots.

PCA

Principal components analysis, a linear method to assess matrix variation.

Percent similarity (PS)

A measure of relationship between two samples based on species cover: PSij = 200 Σmin(xik, xjk)/Σ(xik+xjk), where min = minimum of two values xik, xjk, remaining terms as in Euclidean distance, d.

Permanent plots

Marked sites that are repeatedly sampled.

Primary succession

Ecosystem development on barren surfaces initially lacking in soil or biota.

Priority effects

The consequences of establishment sequence that condition later compositional changes.

Pumice

A silica-rich volcanic rock usually ejected during explosive eruptions.

Pyroclastic flow

Rapidly descending current of superheated gas and tephra hugging the ground; deposits are often of very fine texture and easily eroded.

RDA

Redundancy analysis, a constrained ordination based on PCA.

Relict site (vegetation)

Sites protected by topography and snow that supported surviving vegetation.

Safe-site

Any location that provides suitable conditions for establishment.

Stochastic

Referring to a random, chance-driven process; opposed to deterministic.

Stresses

Any factors that limit production.

Successional rate

The change in species composition through time.

Tephrafall

A rain of volcanic particles to the ground following ejection into the atmosphere by an explosive eruption. Tephra is a collective term for particles of any size, shape, or composition ejected in an explosive eruption.

Trajectory

The temporal path traveled by vegetation communities, often determined by DCA.

Trajectory complexity

A measure of community turnover measured by Hˈ. See habitat complexity.

References

  1. Alvarez-Molina, L.L., M.L. Martinez, O. Perez-Maqueo, J.B. Gallego-Fernandez, and P. Flores. 2012. Richness, diversity, and rate of primary succession over 20 years in a tropical coastal dunes. Plant Ecology 213: 1597–1608.CrossRefGoogle Scholar
  2. Analytical Software. 2013. Statistix 10. Tallahassee: Analytical Software.Google Scholar
  3. Anthelme, F., J.-C. Villaret, and J.-J. Brun. 2007. Shrub encroachment in the Alps gives rise to the convergence of sub-alpine communities on a regional scale. Journal of Vegetation Science 18: 355–362.CrossRefGoogle Scholar
  4. Baasch, A., A. Kirmer, and S. Tischew. 2012. Nine years of vegetation development in a post-mining site: Effects of spontaneous and assisted site recovery. Journal of Applied Ecology 49: 251–260.CrossRefGoogle Scholar
  5. Baeten, L., M. Hermy, S. Van Dael, and K. Verhyen. 2010. Unexpected understorey community development after 30 years in ancient and post-agricultural forests. Journal of Ecology 98: 1447–1453.CrossRefGoogle Scholar
  6. Baniya, C.B., T. Solhoy, and O.R. Vetaas. 2009. Temporal changes in species diversity and composition in abandoned fields in a trans-Himalayan landscape, Nepal. Plant Ecology 201: 383–399.CrossRefGoogle Scholar
  7. Beisner, B., D. Haydon, and K. Cuddington. 2003. Alternative states in ecology. Frontiers in Ecology 1: 376–382.CrossRefGoogle Scholar
  8. Bischoff, A., G. Warthemann, and S. Klotz. 2009. Succession of floodplain grasslands following reduction in land use intensity: The importance of environmental conditions, management, and dispersal. Journal of Applied Ecology 46: 241–249.CrossRefGoogle Scholar
  9. Bishop, J.G. 2002. Early primary succession on Mount St. Helens: Impact of insect herbivores on colonizing lupines. Ecology 83: 191–202.CrossRefGoogle Scholar
  10. Bishop, J.G., W.F. Fagan, J.D. Schade, and C.M. Crisafulli. 2005. Causes and consequences of herbivory on prairie lupine (Lupinus lepidus) in early primary succession. In Ecological responses to the 1980 eruption of Mount St. Helens, ed. V.H. Dale, F.J. Swanson, and C.M. Crisafulli, 151–162. New York: Springer.CrossRefGoogle Scholar
  11. Bossuyt, B., O. Honnay, and M. Hermy. 2005. Evidence for community assembly constraints during succession in dune slack plant communities. Plant Ecology 178: 201–209.CrossRefGoogle Scholar
  12. Boyes, L.J., R.M. Gunton, M.E. Griffiths, and M.J. Lawes. 2011. Causes of arrested succession in coastal dune forest. Plant Ecology 212: 21–32.CrossRefGoogle Scholar
  13. Brownstein, G., J.B. Steel, S. Porter, A. Gray, C. Wilson, P.G. Wilson, and J.B. Wilson. 2012. Chance in plant communities: A new approach to its measurement using the nugget from spatial autocorrelation. Journal of Ecology 100: 987–996.CrossRefGoogle Scholar
  14. Burt, J.W., and J.J. Clary. 2016. Initial disturbance intensity affects recovery rates and successional divergence on abandoned ski slopes. Journal of Applied Ecology 53: 607–615.CrossRefGoogle Scholar
  15. Butterfield, B.J., and R.M. Callaway. 2013. A functional comparative approach to facilitation and its context dependence. Functional Ecology 27: 907–917.CrossRefGoogle Scholar
  16. Chaideftou, E., A.S. Kallimanis, E. Bergmeier, and P. Dimopoulos. 2012. How does plant species composition change from year to year? A cases study from the herbaceous layer of a sub-Mediterranean oak woodland. Community Ecology 13: 88–96.CrossRefGoogle Scholar
  17. Chapman, J.L., and R.W. McEwan. 2013. Spatio-temporal dynamics of alpha- and beta-diversity across topographic gradients in the herbaceous layer of an old-growth deciduous forest. Oikos 122: 1679–1686.CrossRefGoogle Scholar
  18. Clements, F.E. 1936. Nature and structure of the climax. Journal of Ecology 24: 252–284.CrossRefGoogle Scholar
  19. Connell, J.H. 1980. Diversity and the coevolution of competitors, or the ghost of competition past. Oikos 35: 131–138.CrossRefGoogle Scholar
  20. Daniels, F.J.A., J.G. de Molenaar, M. Chytrý, and L. Tichy. 2011. Vegetation change in Southeast Greenland: Tasiilaq revisited after 40 years. Applied Vegetation Science 14: 230–241.CrossRefGoogle Scholar
  21. del Moral, R. 1979. High elevation vegetation of the Enchantment Lakes Basin. Canadian Journal of Botany 57: 1111–1130.CrossRefGoogle Scholar
  22. ———. 1998. Early succession on lahars spawned by Mount St. Helens. American Journal of Botany 85: 820–828.CrossRefGoogle Scholar
  23. ———. 1999a. Plant succession on pumice at Mount St. Helens, Washington. American Midland Naturalist 141: 101–114.CrossRefGoogle Scholar
  24. ———. 1999b. Predictability of primary successional wetlands on pumice, Mount St. Helens. Madroño 46: 177–186.Google Scholar
  25. ———. 2007. Vegetation dynamics in space and time: an example from Mount St. Helens. Journal of Vegetation Science 18: 479–488.CrossRefGoogle Scholar
  26. ———. 2009. Increasing deterministic control of primary succession on Mount St. Helens, Washington. Journal of Vegetation Science 20: 1145–1154.CrossRefGoogle Scholar
  27. ———. 2010. Thirty years of permanent vegetation plots, Mount St. Helens, Washington. Ecology 91: 2185.CrossRefGoogle Scholar
  28. del Moral, R., and C.C. Chang. 2015. Multiple assessments of succession rates on Mount St. Helens. Plant Ecology 216: 165–176.CrossRefGoogle Scholar
  29. del Moral, R., and A.J. Eckert. 2005. Colonization of volcanic deserts from productive patches. American Journal of Botany 92: 27–36.CrossRefGoogle Scholar
  30. del Moral, R., and E.E. Ellis. 2004. Gradients in heterogeneity and structure on lahars, Mount St. Helens, Washington, USA. Plant Ecology 175: 273–286.CrossRefGoogle Scholar
  31. del Moral, R., and C.C. Jones. 2002. Early spatial development of vegetation on pumice at Mount St. Helens. Plant Ecology 162: 9–22.CrossRefGoogle Scholar
  32. del Moral, R., and I.L. Lacher. 2005. Vegetation patterns 25 years after the eruption of Mount St. Helens, Washington. American Journal of Botany 92: 1948–1956.CrossRefGoogle Scholar
  33. del Moral, R., and B. Magnússon. 2014. Surtsey and Mount St. Helens: A comparison of early succession rates. Biogeosciences 11: 2099–2111.CrossRefGoogle Scholar
  34. del Moral, R., and L.R. Rozzell. 2005. Effects of lupines on community structure and species association. Plant Ecology 180: 203–215.CrossRefGoogle Scholar
  35. del Moral, R., and D.M. Wood. 1988. Dynamics of herbaceous vegetation recovery on Mount St. Helens, Washington, USA, after a volcanic eruption. Vegetatio 47: 11–27.CrossRefGoogle Scholar
  36. del Moral, R., and D.M. Wood. 1993. Understanding dynamics of early succession on Mount St. Helens. Journal of Vegetation Science 4: 223–234.CrossRefGoogle Scholar
  37. del Moral, R., and D.M. Wood. 2012. Vegetation development on permanently established grids, Mount St. Helens (1986–2010). Ecology 93: 2125.CrossRefGoogle Scholar
  38. del Moral, R., J.H. Titus, and A.M. Cook. 1995. Early primary succession on Mount St. Helens, Washington, USA. Journal of Vegetation Science 6: 107–120.CrossRefGoogle Scholar
  39. del Moral, R., D.M. Wood, and J.H. Titus. 2005. How landscape factors affect recovery of vegetation on barren surfaces. In Ecological responses to the 1980 eruption of Mount St. Helens, ed. V.H. Dale, F.J. Swanson, and C.M. Crisafulli, 93–109. New York: Springer.CrossRefGoogle Scholar
  40. del Moral, R., L.R. Walker, and J.P. Bakker. 2007. Insights gained from succession for the restoration of landscape structure and function. In Linking restoration and succession in theory and in practice, ed. L.R. Walker, J. Walker, and R.J. Hobbs, 19–44. New York: Springer.Google Scholar
  41. del Moral, R., J.E. Sandler, and C.P. Muerdter. 2009. Spatial factors affect primary succession on the Muddy River Lahar, Mount St. Helens, Washington. Plant Ecology 202: 177–190.CrossRefGoogle Scholar
  42. del Moral, R., J.M. Saura, and J.N. Emenegger. 2010. Primary succession trajectories on a barren plain, Mount St. Helens, Washington. Journal of Vegetation Science 21: 857–867.CrossRefGoogle Scholar
  43. del Moral, R., L.A. Thomason, A.C. Wenke, N. Lozanoff, and M.D. Abata. 2012. Primary succession trajectories on pumice at Mount St. Helens, Washington. Journal of Vegetation Science 23: 73–85.CrossRefGoogle Scholar
  44. Dona, A.J., and C. Galen. 2006. Sources of spatial and temporal heterogeneity in the colonization of an alpine krummholz environment by the weedy subalpine plant Chamerion angustifolium (fireweed). Canadian Journal of Botany 84: 933–939.CrossRefGoogle Scholar
  45. Efford, J.T., B.D. Clarkson, and R.J. Bylsma. 2014. Persistent effects of a tephra eruption (AD 1655) on tree line composition and structure, Mt Taranaki, New Zealand. New Zealand Journal of Botany 52: 245–261.CrossRefGoogle Scholar
  46. Favier, C., J. Aleman, L. Bremond, M.A. Dubois, V. Freycon, and J.M. Yangakola. 2012. Abrupt shifts in African savanna tree cover along a climatic gradient. Global Ecology and Biogeography 21: 787–797.CrossRefGoogle Scholar
  47. Freeman, J.E., and L.N. Kobziar. 2011. Tracking post-fire successional trajectories in a plant community adapted to high-severity fire. Ecological Applications 21: 61–74.CrossRefGoogle Scholar
  48. Fuller, R.N., and R. del Moral. 2003. The role of refugia and dispersal in primary succession on Mount St. Helens, Washington. Journal of Vegetation Science 14: 637–644.CrossRefGoogle Scholar
  49. Gerla, D.J., and W.M. Mooij. 2014. Alternative stable states and alternative end states of community assembly through intra- and interspecific positive and negative interactions. Theoretical Population Biology 96: 8–18.CrossRefGoogle Scholar
  50. Granzow-de la Cerda, I.G. Arellano, M. Brugeus, and A. Sola-Lopez. 2016. The role of distance and habitat specificity in bryophyte and perennial seed plant metacommunities in arid scrubland fragments. Journal of Vegetation Science 27: 414–426.CrossRefGoogle Scholar
  51. Grime, J.P., and S. Pierce. 2012. The evolutionary strategies that shape ecosystems. Chichester: Wiley/Blackwell.CrossRefGoogle Scholar
  52. Halpern, C.B., and M.E. Harmon. 1983. Early plant succession on the Muddy River mudflow, Mount St. Helens, Washington. American Midland Naturalist 110: 97–106.CrossRefGoogle Scholar
  53. Kamijo, T., K. Kitayama, A. Sugawara, S. Urushimichi, and K. Sasai. 2002. Warm temperate forest on volcano lava and ejecta. Folia Geobotanica 37: 71–91.CrossRefGoogle Scholar
  54. Kardol, P., D.E. Todd, P.J. Hanson, and J. Mulholland. 2010. Long-term successional forest dynamics: Species and community responses to climatic variability. Journal of Vegetation Science 21: 627–642.Google Scholar
  55. Kayes, L.J., P.D. Anderson, and K.J. Puettmann. 2010. Vegetation succession among and within structural layers following wildfire in managed forests. Journal of Vegetation Science 21: 233–247.CrossRefGoogle Scholar
  56. Kefi, S., M. Holmgren, and M. Scheffer. 2016. When can positive interactions cause alternative stable states in ecosystems? Functional Ecology 30: 88–97.CrossRefGoogle Scholar
  57. Kovach, W.L. 1999. MVSP, a multivariate statistics package for Windows, version 3.0. Pentraeth: Kovach Computer Consulting Services.Google Scholar
  58. Laborde, J., and K. Thompson. 2013. Colonization of limestone grasslands by woody plants: The role of seed limitation and herbivory by vertebrates. Journal of Vegetation Science 24: 307–319.CrossRefGoogle Scholar
  59. Lindig-Cisneros, R., S.L. Galindo-Vallejo, and S. Lara-Cabrera. 2006. Vegetation of tephra deposits 50 years after the end of the eruption of the Paricutin volcano, Mexico. Southwestern Naturalist 51: 455–461.CrossRefGoogle Scholar
  60. Long, W.X., X.B. Yang, and D.H. Li. 2012. Patterns of species diversity and soil nutrients along a chronosequence of vegetation recovery in Hainan Island, South China. Ecological Restoration 27: 561–568.CrossRefGoogle Scholar
  61. Magnússon, B., S.H. Magnússon, and S. Fridriksson. 2009. Development in plant colonization and succession on Surtsey during 1999–2008. Surtsey Research 12: 57–76.Google Scholar
  62. Marteinsdottir, B., K. Svavarsdóttir, and T.E. Thorhallsdottir. 2010. Development of vegetation patterns in early primary succession. Journal of Vegetation Science 21: 531–540.CrossRefGoogle Scholar
  63. Matthews, J.W., and A.G. Endress. 2010. Rate of succession in restored wetlands and the role of site context. Applied Vegetation Science 13: 346–355.Google Scholar
  64. McCune, B., and T.F.H. Allen. 1985. Will similar forests develop on similar sites? Canadian Journal of Botany 63: 367–376.CrossRefGoogle Scholar
  65. McCune, B., and D. Keon. 2002. Equations for potential annual direct incident radiation and heat load. Journal of Vegetation Science 13: 603–606.CrossRefGoogle Scholar
  66. McCune, B., and M.J. Mefford. 2006. PC-ORD, multivariate analysis of ecological data, version 5.0. Gleneden Beach: MjM Software Design.Google Scholar
  67. Økland, R. 1999. On the variation explained by ordination and constrained ordination axes. Journal of Vegetation Science 10: 131–136.CrossRefGoogle Scholar
  68. Platt, W.J., and J.H. Connell. 2003. Natural disturbances and directional replacement of species. Ecological Monographs 73: 507–522.CrossRefGoogle Scholar
  69. Prach, K., P. Pyšek, and V. Jaroŝik. 2007. Climate and pH as determinants of vegetation succession in Central European man-made habitats. Journal of Vegetation Science 18: 701–710.CrossRefGoogle Scholar
  70. Rebele, F. 2013. Differential succession towards woodland along a nutrient gradient. Applied Vegetation Science 16: 365–378.CrossRefGoogle Scholar
  71. Saccone, P., T. Pyykkonen, A. Eskelinen, and R. Virtanen. 2014. Environmental perturbation, grazing pressure, and soil wetness jointly drive mountain tundra toward divergent alternative states. Journal of Ecology 102: 1661–1672.CrossRefGoogle Scholar
  72. Schröder, A., L. Persson, and A.M. De Roos. 2005. Direct experimental evidence for alternative stable states: A review. Oikos 110: 3–19.CrossRefGoogle Scholar
  73. Scott, A.J., and J.W. Morgan. 2012. Early life-history stages drive community reassembly in Australian old-fields. Journal of Vegetation Science 23: 721–731.CrossRefGoogle Scholar
  74. Sparrius, L.B., A.M. Kooijman, M.P.J.M. Riksen, and J. Sevink. 2013. Effect of geomorphology and nitrogen deposition on rate of vegetation succession in inland drift sands. Applied Vegetation Science 16: 379–389.CrossRefGoogle Scholar
  75. Suding, K.N., and R.J. Hobbs. 2009. Threshold models in restoration and conservation: A developing framework. Trends in Ecology and Evolution 24: 271–279.CrossRefGoogle Scholar
  76. Swanson, F.J., and J.J. Major. 2005. Physical events, environments, and geological-ecological interactions at Mount St. Helens: March 1980–2004. In Ecological responses to the 1980 eruption of Mount St. Helens, ed. V.H. Dale, F.J. Swanson, and C.M. Crisafulli, 27–44. New York: Springer.CrossRefGoogle Scholar
  77. ter Braak, C.J.F., and P. Šmilauer. 2007. CANOCO—A FORTRAN program for canonical community ordination (version 4.5). Wageningen, The Netherlands: DLO-Agricultural Mathematics Group.Google Scholar
  78. Titus, J.H., and J.G. Bishop. 2014. Propagule limitation and competition with nitrogen fixers limit conifer colonization during primary succession. Journal of Vegetation Science 25: 990–1003.CrossRefGoogle Scholar
  79. Titus, J.H., and R. del Moral. 1998. The role of mycorrhizal fungi and microsites in primary succession on Mount St. Helens. American Journal of Botany 85: 370–375.CrossRefGoogle Scholar
  80. Titus, J.H., S. Whitcomb, and H.J. Pioniak. 2007. Distribution of arbuscular mycorrhizae in relation to microsites on primary successional substrates on Mount St. Helens. Canadian Journal of Botany 85: 941–948.CrossRefGoogle Scholar
  81. Tsuyuzaki, S., J.H. Titus, and R. del Moral. 1997. Seedling establishment patterns on the Pumice Plain, Mount St. Helens, Washington. Journal of Vegetation Science 8: 727–734.CrossRefGoogle Scholar
  82. Turner, M.G., W.L. Baker, C.J. Peterson, and R.K. Peet. 1998. Factors influencing succession: Lessons from large, infrequent natural disturbances. Ecosystems 1: 511–523.CrossRefGoogle Scholar
  83. Ujházy, K., J. Fanta, and K. Prach. 2011. Two centuries of vegetation succession in an inland sand dune area, central Netherlands. Applied Vegetation Science 14: 316–325.CrossRefGoogle Scholar
  84. Walker, L.R., and R. del Moral. 2003. Primary succession and ecosystem rehabilitation. Cambridge: Cambridge University Press.CrossRefGoogle Scholar
  85. Walker, L.R., B.D. Clarkson, W.B. Silvester, and B.R. Clarkson. 2003. Colonization dynamics and facilitative impacts of a nitrogen-fixing shrub in primary succession. Journal of Vegetation Science 14: 277–290.CrossRefGoogle Scholar
  86. Walker, L.R., P.F. Bellingham, and D.A. Peltzer. 2006. Plant characteristics are poor predictors of microsite colonization during the first two years of primary succession. Journal of Vegetation Science 17: 397–406.CrossRefGoogle Scholar
  87. Walker, L.R., N. Hölzel, R. Marrs, R. del Moral, and K. Prach. 2014. Optimization of intervention levels in ecological restoration. Applied Vegetation Science 17: 187–192.CrossRefGoogle Scholar
  88. Whittaker, R.H. 1967. Gradient analysis of vegetation. Biological Reviews 42: 207–264.CrossRefGoogle Scholar
  89. Williamson, G.B., T.V. Bentos, J. Longworth, and R.C.G. Mesquita. 2014. Convergence and divergence in alternative successional pathways in Central Amazonia. Plant Ecology & Diversity 7: 341–348.CrossRefGoogle Scholar
  90. Wood, D.M., and R. del Moral. 1987. Mechanisms of early primary succession in subalpine habitats on Mount St. Helens. Ecology 68: 780–790.CrossRefGoogle Scholar
  91. ———. 2000. Seed rain during early primary succession on Mount St. Helens, Washington. Madroño 47: 1–9.Google Scholar
  92. Wood, D.M., and W.F. Morris. 1990. Ecological constrains to seedling establishment on the Pumice Plain, Mount St. Helens, Washington. American Journal of Botany 77: 1411–1418.CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media LLC 2018

Authors and Affiliations

  1. 1.Department of BiologyUniversity of WashingtonSeattleUSA
  2. 2.Department of BiologyState University of New York at FredoniaFredoniaUSA

Personalised recommendations