Crown shyness

Canopy of D. aromatica at the Forest Research Institute Malaysia displaying crown shyness
Trees at Plaza San Martín (Buenos Aires), Argentina

Crown shyness is a phenomenon observed in some tree species, in which the crowns of fully stocked trees do not touch each other, forming a canopy with channel-like gaps.[1][2] It is also known as canopy disengagement,[3] canopy shyness,[4] or intercrown spacing.[5] The phenomenon is most prevalent among trees of the same species, but also occurs between trees of different species.[6][7]

Causes

The exact cause of crown shyness is not certain.[6] The phenomenon has been discussed in scientific literature since the 1920s.[8]

One theory is that the tall and slender trees in windy areas may suffer physical damage, as they collide with each other during winds. To prevent abrasions and collisions, they respond with crown shyness. Experiments show that if the crowns are artificially prevented from colliding in the winds, they gradually fill the canopy gaps.[9]

Australian forester M.R. Jacobs, who studied the crown shyness patterns in eucalyptus in 1955, believed that the trees' growing tips were sensitive to abrasion, resulting in canopy gaps.[10] Miguel Franco (1986) observed that the branches of Picea sitchensis (Sitka spruce) and Larix kaempferi (Japanese larch) suffered physical damage due to abrasion, which killed the leading shoots.[11][12]

However, Malaysian scholar Francis S.P. Ng, who studied Dryobalanops aromatica in 1977, found no evidence of abrasions due to contact in that tree. He suggested that the growing tips were sensitive to light levels and stopped growing when nearing the adjacent foliage.[13][6] In Betula pendula (silver birch), fewer buds develop in parts of the crown that are already dense or where the crowns of different trees start meeting, possibly because of less light.[14]

Another explanation is that the crown shyness inhibits spread of leaf-eating insect larvae.[15]

Species

Trees that display crown shyness patterns include:

References

  1. ↑ Norsiha A. and Shamsudin (2015-04-25). "Shorea resinosa : Another jigsaw puzzle in the sky". Forest Research Institute Malaysia.
  2. ↑ H Fish, VJ Lieffers, U Silins, RJ Hall (2006). "Crown shyness in lodgepole pine stands of varying stand height, density and site index in the upper foothills of Alberta". Canadian Journal of Forest Research 36 (9): 2104–2111. doi:10.1139/x06-107.
  3. 1 2 James W. Goudie, Kenneth R. Polsson, Peter K. Ott (2008). "An empirical model of crown shyness for lodgepole pine (Pinus contorta var. latifolia [Engl.] Critch.) in British Columbia". Forest Ecology and Management 257 (1): 321–331. doi:10.1016/j.foreco.2008.09.005.
  4. ↑ Peter Thomas; John Packham (26 July 2007). Ecology of Woodlands and Forests: Description, Dynamics and Diversity. Cambridge University Press. p. 12. ISBN 978-0-521-83452-0.
  5. 1 2 Francis E. Putz, Geoffrey G. Parker and Ruth M. Archibald (1984). "Mechanical Abrasion and Intercrown Spacing" (PDF). American Midland Naturalist 112 (1): 24–28. doi:10.2307/2425452.
  6. 1 2 3 4 5 Alan J Rebertus (1988). Crown Shyness in a Tropical Cloud Forest "Crown shyness in a tropical cloud forest" Check |url= value (help) (PDF). Biotropica 20 (4): 338–339. doi:10.2307/2388326. ISSN 0006-3606.
  7. 1 2 K. Paijmans (1973). "Plant Succession on Pago and Witori Volcanoes, New Britain" (PDF). Pacific Science (University of Hawaii Press) 27 (3): 60–268. ISSN 0030-8870.
  8. ↑ TASS III: Simulating the management, growth and yield of complex stands
  9. ↑ Victor Lieffers. "Crown shyness in maturing boreal forest stands". SFM Network Research Note Series 36. ISSN 1715-0981.
  10. ↑ Maxwell Ralph Jacobs (1955). Growth Habits of the Eucalypts. Forestry and Timber Bureau.
  11. ↑ M. Franco (14 August 1986). "The Influences of Neighbours on the Growth of Modular Organisms with an Example from Trees". Philosophical Transactions of the Royal Society, Series B 313 (1159): 209–225. doi:10.1098/rstb.1986.0034.
  12. ↑ J. Bastow Wilson and Andrew D.Q. Agnew. "2: Interactions between species". The nature of the plant community: a reductionist view. University of North Carolina at Chapel Hill.
  13. ↑ F.S.P. Ng (1997). "Shyness in trees". Nature Malaysiana 2: 34–37.
  14. ↑ Peter A. Thomas (17 April 2014). Trees: Their Natural History. Cambridge University Press. p. 197. ISBN 978-0-521-13358-6.
  15. ↑ "Tropical Rain Forest". Woodland Park Zoo. p. 37.
  16. ↑ Margaret Lowman; Soubadra Devy; T. Ganesh (22 June 2013). Treetops at Risk: Challenges of Global Canopy Ecology and Conservation. Springer Science & Business Media. p. 34. ISBN 978-1-4614-7161-5.
  17. ↑ R. G. Florence (January 2004). Ecology and Silviculture of Eucalypt Forests. Csiro Publishing. pp. 182–. ISBN 978-0-643-09064-4.
  18. 1 2 RO Lawton and Francis E Putz. "The vegetation of the Monteverde Cloud Forest Reserve". Brenesia 18: 101–116.
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