GERMINATION ECOLOGY OF NEOTROPICAL PIONEERS: INTERACTING EFFECTS OF ENVIRONMENTAL CONDITIONS AND SEED SIZE

EcologyVolume 83, Issue 10 p. 2798-2807 Regular Article GERMINATION ECOLOGY OF NEOTROPICAL PIONEERS: INTERACTING EFFECTS OF ENVIRONMENTAL CONDITIONS AND SEED SIZE T. R. H. Pearson, T. R. H. Pearson Department of Plant and Soil Science, University of Aberdeen, Cruickshank Building, St. Machar Drive, Aberdeen AB24 3UU, UKSearch for more papers by this authorD. F. R. P. Burslem, D. F. R. P. Burslem Department of Plant and Soil Science, University of Aberdeen, Cruickshank Building, St. Machar Drive, Aberdeen AB24 3UU, UKSearch for more papers by this authorC. E. Mullins, C. E. Mullins Department of Plant and Soil Science, University of Aberdeen, Cruickshank Building, St. Machar Drive, Aberdeen AB24 3UU, UKSearch for more papers by this authorJ. W. Dalling, J. W. Dalling Department of Plant Biology, University of Illinois, Urbana, Illinois 61801 USA Smithsonian Tropical Research Institute, Unit 0948, APO AA 34002 USASearch for more papers by this author T. R. H. Pearson, T. R. H. Pearson Department of Plant and Soil Science, University of Aberdeen, Cruickshank Building, St. Machar Drive, Aberdeen AB24 3UU, UKSearch for more papers by this authorD. F. R. P. Burslem, D. F. R. P. Burslem Department of Plant and Soil Science, University of Aberdeen, Cruickshank Building, St. Machar Drive, Aberdeen AB24 3UU, UKSearch for more papers by this authorC. E. Mullins, C. E. Mullins Department of Plant and Soil Science, University of Aberdeen, Cruickshank Building, St. Machar Drive, Aberdeen AB24 3UU, UKSearch for more papers by this authorJ. W. Dalling, J. W. Dalling Department of Plant Biology, University of Illinois, Urbana, Illinois 61801 USA Smithsonian Tropical Research Institute, Unit 0948, APO AA 34002 USASearch for more papers by this author First published: 01 October 2002 https://doi.org/10.1890/0012-9658(2002)083[2798:GEONPI]2.0.CO;2Citations: 209Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Abstract Germination provides many potentially unrecognized sources of variation in the regeneration niche. In this study we relate germination requirements and seed size for 16 species of pioneer trees to microclimatic conditions present in gaps in semi-deciduous rain forest in Panama. We found that, whereas increased duration of direct irradiance can be an effective indicator of the presence of a canopy gap across all scales of canopy openness, diel fluctuations in soil temperature effectively discriminate both understory sites and small gaps (25 m2) from larger gaps. Germination response was significantly related to seed size. Small-seeded species (seed mass <2 mg) showed significantly greater germination in response to irradiance of 22.3 μmol·m−2·s−1 than in complete darkness. Their germination was unaffected by an increasing magnitude of diel temperature fluctuation up to a species-specific threshold, above which it declined. Large-seeded species (seed mass >2 mg) germinated equally in light and darkness (with one exception) and either showed a positive germination response to an increasing magnitude of temperature fluctuation (four species) or no significant response (four species). The maximum seed burial depth from which seedlings could emerge successfully was strongly positively associated with seed mass. We conclude that photoblastic germination of tropical pioneer trees results in small-seeded species germinating in gaps only when seeds are located in microsites that are suitable for seedling emergence. A positive germination response to increasing temperature fluctuation can stimulate germination of larger-seeded species in larger gaps and when they are buried beneath an opaque soil or litter layer. Therefore, seed size differences constrain the physiological mechanisms of canopy gap detection in tropical pioneer trees and might contribute to observed differences in the distribution of adult plants in relation to canopy gap size. Supporting Information Filename Description https://dx.doi.org/10.6084/m9.figshare.c.3297683 Research data pertaining to this article is located at figshare.com: Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. Literature Cited Acuña, P., and N. C. Garwood . 1987. Efecto de la luz y de la escarificación en la germinación de las semillas de cinco especies de arboles tropicales secundarios. Revista de Biologia Tropical 35: 203–207. Web of Science®Google Scholar Baskin, C. C., and J. M. Baskin . 1998. Seeds. Academic Press, San Diego, California, USA. Google Scholar Baskin, J. M., C. C. Baskin, and L. Xiaojie . 2000. Taxonomy, anatomy and evolution of physical dormancy in seeds. Plant Species Biology 15: 139–152. 10.1046/j.1442-1984.2000.00034.x Google Scholar Bond, W. J., M. Honig, and K. E. Maze . 1999. Seed size and seedling emergence: an allometric relationship and some ecological implications. Oecologia 120: 132–136. 10.1007/s004420050841 CASPubMedWeb of Science®Google Scholar Brokaw, N. V. L. 1982. Treefalls: frequency, timing, and consequences. Pages 101–108 in E. Leigh, A. Rand, and D. Windsor, editors. The ecology of a tropical forest. Smithsonian Institution Press, Washington, D.C., USA. Google Scholar Brokaw, N. V. L. 1987. Gap-phase regeneration of three pioneer tree species in a tropical forest. Journal of Ecology 75: 9–19. 10.2307/2260533 Web of Science®Google Scholar Chazdon, R. L., and N. Fetcher . 1984. Light environments of tropical forests. Pages 27–36 in E. Medina, H. A. Mooney, and C. Vázquez-Yanes, editors. Physiological ecology of plants of the wet tropics. Junk, Dordrecht, The Netherlands. Google Scholar Crawley, M. J. 1993. GLIM for ecologists. Blackwell Scientific, Oxford, UK. Google Scholar Croat, T. B. 1978. Flora of Barro Colorado Island. Stanford University Press, Stanford, California, USA. Google Scholar Dalling, J. W., S. P. Hubbell, and K. Silvera . 1998a.. Seed dispersal, seedling establishment and gap partitioning among tropical pioneer trees. Journal of Ecology 86: 674–689. 10.1046/j.1365-2745.1998.00298.x Web of Science®Google Scholar Dalling, J. W., M. D. Swaine, and N. C. Garwood . 1997. Soil seed bank community dynamics in seasonally moist lowland tropical forest, Panama. Journal of Tropical Ecology 13: 659–680. 10.1017/S0266467400010853 Web of Science®Google Scholar Dalling, J. W., M. D. Swaine, and N. C. Garwood . 1998b.. Dispersal patterns and seed bank dynamics of pioneer trees in moist tropical forest. Ecology 79: 564–578. 10.1890/0012-9658(1998)079[0564:DPASBD]2.0.CO;2 Web of Science®Google Scholar Dalling, J. W., K. Winter, J. D. Nason, S. P. Hubbell, D. A. Murawski, and J. L. Hamrick . 2001. The unusual life history of Alseis blackiana: a shade-persistent pioneer tree? Ecology 82: 933–945. 10.1890/0012-9658(2001)082[0933:TULHOA]2.0.CO;2 Web of Science®Google Scholar Engelbrecht, B. M. J., J. W. Dalling, T. R. H. Pearson, R. L. Wolf, D. A. Galvez, T. Koehler, M. C. Ruiz, and T. A. Kursar . 2001. Short dry spells in the wet season increase mortality of tropical pioneer seedlings. Pages 665–669 in K. N. Ganeshaiah, R. Uma Shaanker, and K. S. Bawa, editors. Tropical ecosystems: structure, diversity and human welfare. Proceedings of the International Conference on Tropical Ecosystems: structure, diversity and human welfare. Oxford and IBH Publishing Company, New Delhi, India. Google Scholar Foster, R. B., and N. V. L. Brokaw . 1982. Structure and history of the vegetation of Barro Colorado Island. Pages 67–81 in E. Leigh, A. Rand, and D. Windsor, editors. The ecology of a tropical forest. Smithsonian Institution Press, Washington, D.C., USA. Google Scholar Frankland, B. 1976. Phytochrome control of seed germination in relation to the light environment. Pages 477–491 in H. Smith, editor. Light and plant development. Butterworths, London, UK. Google Scholar Garwood, N. C. 1982. Seasonal rhythm of seed germination in a semi-deciduous tropical forest. Pages 173–185 in E. G. Leigh Jr., A. S. Rand, and D. M. Windsor, editors. The ecology of a tropical forest: seasonal changes and long-term changes. Smithsonian Institution Press, Washington, D.C., USA. Google Scholar Grubb, P. J. 1996. Rainforest dynamics: the need for new paradigms. Pages 215–233 in D. S. Edwards, S. C. Choy, and W. E. Booth, editors. Tropical rainforest research—current issues. Kluwer, The Hague, The Netherlands. Google Scholar Harms, K. E., S. J. Wright, O. Calderon, A. Hernandez, and E. A. Herre . 2000. Pervasive density dependent recruitment enhances seedling diversity in a tropical forest. Nature 404: 493–495. 10.1038/35006630 CASPubMedWeb of Science®Google Scholar Hubbell, S. P., R. B. Foster, S. T. O'Brien, K. E. Harms, R. Condit, B. Wechsler, S. J. Wright, and L. Loo de Lao . 1999. Light-gap disturbances, recruitment limitation, and tree diversity in a Neotropical forest. Science 283: 554–557. 10.1126/science.283.5401.554 CASPubMedWeb of Science®Google Scholar McCullagh, P., and J. A. Nelder . 1989. Generalized linear models. Chapman and Hall, London, UK. Google Scholar Metcalfe, D. J., and P. J. Grubb . 1996. Seed mass and light requirements for regeneration in South-east Asian rain forest. Canadian Journal of Botany 73: 817–826. 10.1139/b95-090 Web of Science®Google Scholar Metcalfe, D. J., and P. J. Grubb . 1997. The responses to shade of seedlings of very small-seeded tree and shrub species from tropical rain forest in Singapore. Functional Ecology 11: 215–221. 10.1046/j.1365-2435.1997.00070.x Web of Science®Google Scholar Milberg, P., L. Andersson, and K. Thompson . 2000. Large-seeded spp. are less dependent on light for germination than small-seeded ones. Seed Science Research 10: 99–104. 10.1017/S0960258500000118 Web of Science®Google Scholar Molofsky, J., and C. K. Augspurger . 1992. The effect of leaf litter on early seedling establishment in a tropical forest. Ecology 73: 68–77. 10.2307/1938721 Web of Science®Google Scholar Paz, L., and C. Vázquez-Yanes . 1998. Comparative seed ecophysiology of wild and cultivated Carica papaya trees from a tropical rain forest region in Mexico. Tree Physiology 18: 277–280. 10.1093/treephys/18.4.277 PubMedWeb of Science®Google Scholar Putz, F. E. 1983. Treefall pits and mounds, buried seeds, and the importance of soil disturbance to pioneer trees on Barro Colorado Island. Ecology 64: 1069–1074. 10.2307/1937815 Web of Science®Google Scholar Raich, J. W., and W. K. Gong . 1990. Effects of canopy openings on tree seed germination in a Malaysian dipterocarp forest. Journal of Tropical Ecology 6: 203–217. 10.1017/S0266467400004326 Web of Science®Google Scholar Rand, A. S., and W. M. Rand . 1982. Variation in rainfall on Barro Colorado Island. Pages 47–59 in E. Leigh, A. Rand, and D. Windsor, editors. The ecology of a tropical forest. Smithsonian Institution Press, Washington, D.C., USA. Google Scholar Rees, M., and M. Westoby . 1996. Game-theoretical evolution of seed mass in multi-species ecological models. Oikos 78: 116–126. 10.2307/3545807 Web of Science®Google Scholar Smith, H. 2000. Phytochromes and light signal perception by plants—an emerging synthesis. Nature 407: 585–591. PubMedGoogle Scholar Sokal, R. R., and F. J. Rohlf . 1995. Biometry. W. H. Freeman, New York, New York, USA. Google Scholar Swaine, M. D., and T. C. Whitmore . 1988. On the definition of ecological species groups in tropical rain forest. Vegetatio 75: 81–86. 10.1007/BF00044629 Google Scholar Tester, M., and C. Morris . 1987. The penetration of light through soil. Plant, Cell and Environment 10: 281–286. 10.1111/j.1365-3040.1987.tb01607.x Web of Science®Google Scholar Thompson, K., and J. P. Grime . 1983. A comparative study of germination responses to diurnally-fluctuating temperatures. Journal of Applied Ecology 20: 141–156. 10.2307/2403382 Web of Science®Google Scholar Vázquez-Yanes, C., and A. Orozco-Segovia . 1982. Seed germination of a tropical rain forest tree Heliocarpus donnell-smithii in response to diurnal fluctuations in temperature. Physiologia Plantarum 56: 295–298. 10.1111/j.1399-3054.1982.tb00341.x Web of Science®Google Scholar Vázquez-Yanes, C., and A. Orozco-Segovia . 1990. Seed dormancy in the tropical rain forest. Pages 247–259 in K. S. Bawa and M. Hadley, editors. Reproductive ecology of tropical forest plants. UNESCO, Paris, France. Google Scholar Vázquez-Yanes, C., and A. Orozco-Segovia . 1992. Effects of litter from a tropical rain forest on tree seed germination and establishment under controlled conditions. Tree Physiology 11: 391–400. 10.1093/treephys/11.4.391 PubMedGoogle Scholar Vázquez-Yanes, C., and A. Orozco-Segovia . 1993. Patterns of seed longevity and germination in the tropical rainforest. Annual Review of Ecology and Systematics 24: 69–87. 10.1146/annurev.es.24.110193.000441 Web of Science®Google Scholar Vázquez-Yanes, C., A. Orozco-Segovia, E. Rincon, M. E. Sanchez-Coronado, R. Huante, J. R. Toledo, and U. L. Barradas . 1990. Light beneath the litter in a tropical forest: effect on seed germination. Ecology 71: 1952–1958. 10.2307/1937603 Web of Science®Google Scholar Vazquez-Yanes, C., and B. Pérez-García . 1976. Notas sobre la morfología y la anatomía de la testa de las semillas de Ochroma lagopus Sw. Turrialba 26: 310–311. Google Scholar Weiner, J. 1990. Asymmetric competition in plant populations. Trends in Ecology and Evolution 5: 360–364. 10.1111/j.1469-8137.2005.01520.x CASPubMedWeb of Science®Google Scholar Citing Literature Volume83, Issue10October 2002Pages 2798-2807 ReferencesRelatedInformation