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皇冠害羞
Crown shyness

原始链接: https://en.wikipedia.org/wiki/Crown_shyness

树冠羞怯，也称为树冠间隙综合症，是森林生态系统中常见的自然现象。 某些树种表现出树冠不对称性，树冠顶部的垂直投影往往会避免相互对齐。 即使在物理上相邻位置的同种群体或个人中，这种模式也很明显。 树冠羞怯似乎是针对高光强度的一种反应机制，使个体树木能够最大限度地减少暴露于破坏性的强化 UV-B 辐射、过度蒸腾速率和潜在的阳光引起的压力。 虽然其确切起源仍有争议，但已经确定了多种机制，从基因型变异和环境敏感性到分支结构和自我修剪等内在结构特征。 光敏调节，特别是通过向下反射感知不同的蓝光传输，似乎会触发定向芽发育。 此外，某些鸟类已经适应专门在远离太阳盘的分支末端周围的首选进食地点附近捕猎猎物，从而加强了树冠顶部的距离。 不同的物种表现出不同程度的树冠羞怯表达，有时甚至完全不表达。 尽管光线在到达地面后迅速衰减，但其在树冠覆盖高度以下的减少会放大光线差异，加剧林线上方的辐照度差异。 此外，树冠羞怯不仅限于温带阔叶落叶树种，而且在多个科、属、甚至裸子树中也观察到。

然而，研究被称为“树冠羞怯”的现象可以揭示树木如何相互作用以及如何潜在地影响它们的环境。 除了减少对资源的竞争和保护自己免受传播疾病之外，树冠羞怯还可能在减轻风暴期间的风害方面发挥作用。 虽然关于这种行为仍有许多未解答的问题，但研究人员继续研究它并探索林业实践中的潜在应用，例如模仿自然树冠羞怯形成的种植模式，以改善树木的健康和恢复力。 尽管如此，了解树冠羞怯仍然是一个令人着迷的研究领域，它扩展了我们对生态系统的了解，并为可持续管理提供了实用的见解。
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原文

Phenomenon in which the crowns of fully stocked trees do not touch each other

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

Crown shyness (also canopy disengagement,[1] canopy shyness,[2] or inter-crown spacing[3]) is a feature observed in some tree species, in which the crowns of fully stocked trees do not touch each other, instead forming a canopy with channel-like gaps.[4][5] This is most prevalent among trees of the same species, but also occurs between trees of different species.[6][7] There exist many hypotheses as to why crown shyness is an adaptive behavior, and research suggests that it might inhibit spread of leaf-eating insect larvae.[8]

Possible physiological explanations[edit]

The exact physiological basis of crown shyness is uncertain.[6] It has been discussed in scientific literature since the 1920s.[9] The variety of hypotheses and experimental results might suggest that there are multiple mechanisms across different species, an example of convergent evolution.[citation needed]

Some hypotheses contend that the interdigitation of canopy branches leads to "reciprocal pruning" of adjacent trees. Trees in windy areas suffer physical damage as they collide with each other during winds. The abrasions and collisions induce a crown shyness response. Studies suggest that lateral branch growth is largely uninfluenced by neighbours until disturbed by mechanical abrasion.[10] If the crowns are artificially prevented from colliding in the winds, they gradually fill the canopy gaps.[11] This explains instances of crown shyness between branches of the same organism. Proponents of this idea cite that shyness is particularly seen in conditions conducive to this pruning, including windy forests, stands of flexible trees, and early succession forests where branches are flexible and limited in lateral movement.[6][12] According to this theory, variable flexibility in lateral branches greatly influences the degree of crown shyness.

Similarly, some research suggests that constant abrasion at growth nodules disrupts bud tissue such that it is unable to continue with lateral growth. 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.[13] 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.[14][15]

A prominent hypothesis is that canopy shyness has to do with mutual light sensing by adjacent plants. The photoreceptor-mediated shade avoidance response is a well-documented behavior in a variety of plant species.[16] Neighbor detection is thought to be a function of several unique photoreceptors. Plants can sense the proximity of neighbors by sensing backscattered far-red light, a task widely thought to be accomplished by the activity of the phytochrome photoreceptors.[17] Many species of plant respond to an increase in far-red light (and, by extension, encroaching neighbors) by directing growth away from the far-red stimulus and by increasing the rate of elongation.[18] Similarly, plants use blue light to induce the shade-avoidance response, likely playing a role in the recognition of neighboring plants,[19] though this was just starting to be recognised in 1988.[20]

The characterization of these behaviors might suggest that crown shyness is simply the result of mutual shading based on well-understood shade avoidance responses.[6][21] Malaysian scholar Francis S.P. Ng, who studied Dryobalanops aromatica, suggested that the growing tips were sensitive to light levels and stopped growing when nearing the adjacent foliage due to the induced shade.[6][21]

A 2015 study has suggested that Arabidopsis thaliana shows different leaf placement strategies when grown amongst kin and unrelated conspecifics, shading dissimilar neighbors and avoiding kin. This response was shown to be contingent on the proper functioning of multiple photosensory modalities.[22] A 1998 study proposed similar systems of photoreceptor-mediated inhibition of growth as explanations of crown shyness,[6][21] though a causal link between photoreceptors and crown asymmetry had yet to be experimentally proven. This might explain instances of intercrown spacing that are only exhibited between conspecifics.[6][7]

Species[edit]

Trees that display crown shyness patterns include:

References[edit]

  1. ^ a b Goudie, James W.; Polsson, Kenneth R.; Ott, Peter K. (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. ISBN 9781437926163.
  2. ^ 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.
  3. ^ a b Putz, Francis E.; Parker, Geoffrey G.; Archibald, Ruth M. (1984). "Mechanical Abrasion and Intercrown Spacing" (PDF). American Midland Naturalist. 112 (1): 24–28. doi:10.2307/2425452. JSTOR 2425452.
  4. ^ Norsiha A. and Shamsudin (2015-04-25). "Shorea resinosa : Another jigsaw puzzle in the sky". Forest Research Institute Malaysia.
  5. ^
  6. ^ a b c d e f g h i Rebertus, Alan J (1988). "Crown shyness in a tropical cloud forest" (PDF). Biotropica. 20 (4): 338–339. doi:10.2307/2388326. ISSN 0006-3606. JSTOR 2388326.[permanent dead link]
  7. ^ a b c 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. ^ "Tropical Rain Forest". Woodland Park Zoo. p. 37.
  9. ^ "TASS III: Simulating the management, growth and yield of complex stands" (PDF).
  10. ^ Franco, M (14 August 1986). "The influences of neighbours on the growth of modular organisms with an example from trees". Philosophical Transactions of the Royal Society of London. B, Biological Sciences. 313 (1159): 313, 209–225. Bibcode:1986RSPTB.313..209F. doi:10.1098/rstb.1986.0034.
  11. ^ Victor Lieffers. "Crown shyness in maturing boreal forest stands". SFM Network Research Note Series. 36. ISSN 1715-0981. Archived from the original on 2015-09-25. Retrieved 2015-08-23.
  12. ^ a b c Lawton, RO; Putz, Francis E. "The vegetation of the Monteverde Cloud Forest Reserve". Brenesia. 18: 101–116.
  13. ^ Maxwell Ralph Jacobs (1955). Growth Habits of the Eucalypts. Forestry and Timber Bureau.
  14. ^ 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 B. 313 (1159): 209–225. Bibcode:1986RSPTB.313..209F. doi:10.1098/rstb.1986.0034.
  15. ^ Wilson, J. Bastow; Agnew, Andrew D.Q.; Roxburgh, Stephen H. (2019). "2: Interactions between Species". The Nature of Plant Communities. Cambridge: Cambridge University Press. pp. 24–65. doi:10.1017/9781108612265.004. ISBN 9781108612265.
  16. ^ Ballaré, CL; Scopel, AL; Sánchez, RA (19 January 1990). "Far-red radiation reflected from adjacent leaves: an early signal of competition in plant canopies". Science. 247 (4940): 329–32. Bibcode:1990Sci...247..329B. doi:10.1126/science.247.4940.329. PMID 17735851. S2CID 39622241.
  17. ^ Ballare, C. L.; Sanchez, R. A.; Scopel, Ana L.; Casal, J. J.; Ghersa, C. M. (September 1987). "Early detection of neighbour plants by phytochrome perception of spectral changes in reflected sunlight". Plant, Cell and Environment. 10 (7): 551–557. doi:10.1111/1365-3040.ep11604091.
  18. ^ Ballaré, CL; Scopel, AL; Sánchez, RA (June 1997). "Foraging for light: photosensory ecology and agricultural implications". Plant, Cell and Environment. 20 (6): 820–825. doi:10.1046/j.1365-3040.1997.d01-112.x.
  19. ^ Jansen, Marcel AK; Gaba, Victor; Greenberg, Bruce M (April 1998). "Higher plants and UV-B radiation: balancing damage, repair and acclimation". Trends in Plant Science. 3 (4): 131–135. doi:10.1016/S1360-1385(98)01215-1.
  20. ^ Christie, JM; Reymond, P; Powell, GK; Bernasconi, P; Raibekas, AA; Liscum, E; Briggs, WR (27 November 1998). "Arabidopsis NPH1: a flavoprotein with the properties of a photoreceptor for phototropism". Science. 282 (5394): 1698–701. Bibcode:1998Sci...282.1698C. doi:10.1126/science.282.5394.1698. PMID 9831559.
  21. ^ a b c F.S.P. Ng (1997). "Shyness in trees". Nature Malaysiana. 2: 34–37.
  22. ^ Crepy, María A.; Casal, Jorge J. (January 2015). "Photoreceptor-mediated kin recognition in plants". New Phytologist. 205 (1): 329–338. doi:10.1111/nph.13040. hdl:11336/37860. PMID 25264216. S2CID 28093742.
  23. ^ 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.
  24. ^ R. G. Florence (January 2004). Ecology and Silviculture of Eucalypt Forests. Csiro Publishing. pp. 182–. ISBN 978-0-643-09064-4.

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