ぎょーむ日誌 2007-05-22

2007 年 05 月 22 日 (火)

• 0710 起床． コーヒー． 朝飯． 0810 自宅発． 晴． 0825 研究室着．
• セミナー予習．
• 1030 より 研究室セミナー， 本日は矢澤さんで熱帯林論文紹介．
  • Falster, D. S., and M. Westoby. 2005. Alternative height strategies among 45 dicot rain forest species from tropical Queensland, Australia. Journal of Ecology 93:521-535.

  1. Potential height, which spans at least an order of magnitude across species, is considered an important indicator of light capture strategy. Still it remaines unclear how potential height is coordinated with other traits that influence height growth rate, stem persistence and performance in low light. We proposed that contrasting correlation between potential height and other plant attributes would be observed for sets of species selected to span two hypothetical axes of light availability within mature forest and time since disturbance.

  2. We selected 45 perenial rain forest species in Australita's wet tropice to span gradients of light availability and successional status and measured potential height together with traits inlucencing light capture and regeneratrion strategy on mature individuals. The traits included leaf mass per area, leaf nitrogen, wood density, stem mass per length, branch mass fraction and seed mass.

  3. Potential height was significantly correlated with numerous traits among species selected to span each of the two gradients. Height was positively correlated with leaf mass area, leaf nitrogen and seed mass and negatively correlated with leaf area ratio at the branch tip along both light and successional gradients. Height was positively correlated with wood density along the successional axis, with the opposite relationship along the light gradient.

  4.The relationships differed in either slope or intercept between two gradients, reflecting different strategic trade-offs. At a given height, shorter species in the succesional gradient were chracterized by lower leaf mass area, lighter wood, smaller seeds, lower leaf nitrogen and lower leaf area ratio at the branch tip than similar sized species along the light gradient.

  The results of this study support the idea of two distinct, trait-mediated axes of coexistence among short and tall plant species within vegetation. In several cases, trait relationships were weak or non-significant when species groupings were merged, indicating the importance of separating out the two sets for comparison studies.

  • Kohyama, T., E. Suzuki, T. Partomihardjo, T. Yamada, and T. Kubo. 2003. Tree species differentiation in growth, recruitment and allometry in relation to maximum height in a Bornean mixed dipterocarp forest. Journal of Ecology 91:797-806.
  • Poorter, L., F. Bongers, F. J. Sterck, and H. Woll. 2003. Architecture of 53 rain forest tree species differing in adult stature and shade tolerance. Ecology 84:602-608.

  The architecture determines a tree's light capture stability, and efficiency of crown growth. The hypothesis that light demand and adult stature fo tree species within a community, independently of each other, determine species's architectural traits was tested by comparing 53 Liberian rain forest tres species. We evaluated whether species differed in there tree height, crown depth, and crown diameter, whne compared at a standarized size of 15-cm diameter at breast height, and how their architecture changed early during ontogeny.

  Tree height was positively correlated with adult stature and light demand. By producing a relattively slender stem, large stature species area able to rapidly reach their reproductive size, at a low cost for construction and support. Light-demanding species need a slender diameter were negatively correlated with adult stature, but not with light demand. This is in cotrast with the hypothesis that shade-tolerant species should have a shallow crown to reduce self-shading in a light-limited environment. Investigating energy in height growth rather than lateral crown growth allows a rapid vertical stem extension, but crown diameter has to be sufficiently small to reduce the risk of mechanical failure. All architectural patterns were maintained during ontogeny. The key factors driving interspecific differences in tree architecture are the costs of height extension and mechanical stability. In general, light demand and adult stature represent independent axes of architectural differentiation, affecting tree architecture in different ways.

  • Sterck, F. J., and F. Bongers. 2001. Crown development in tropical rain forest trees: patterns with tree height and light availability. Journal of Ecology 89:1-13.

  1. Monitoring of two canopy species Dicorynia guianensis and Vouacapoua americana (Casesalpiniaceae) in tropica rain forest in French Guiana was used to investigate vegetative crown development at five organizational levels: leaf, metamer, extension unit, sympoidal unit and whole crown. The effects of light availability and tree height on different traits were evaluated in trees < 25 m in height and compared with taller individuals (25-37 m). Path analysis is used to illustrate the consequences of traits changes at multiple levels of organization for the whole crown level.

  2. Tree height and canopy openness influenced crown development at each organizational level. Crowns in higher light levels had lower specific leaf area, greater leaf spacing, greater extension of all branches, and greater extension of the leader shoot. With increasing tree height, crowns had a lower specific leaf area, greater leaf area index and greater relative crowth depth.

  3. Vouacapoua showed some responses to light not seen in Dicorynia. In particular, Vouacapoua increased meristem activity with light, but the lack of reponse in Dicorynia may be due to moderate light levels rather than iablity to repond.

  4. Low leaf-diplay costs at low light availability may enable trees to survive light suppressions.

  5. Light availability cannot explain trait changes with tree height. Alternative explanations for trait changes with tre height are discussed.

  6. Several of the relationships between plant traits adn tree height or canopy openness became non-linear when taller trees (25-37 m) were included. In these taller trees, vegetative growth was reduced at all organizational levels, particularly in Vouacapoua, which does not grow as Dicorynia.

  7. Qualitatively, plant responses to light did not differ between trees of different height, and were similar to seedling and sapling data in the literature. Responses were, however, qunatitatively different, suggesting that small saplings cannot serve as model organisms for crown development in taller trees.

  • Thomas, S. C. 1996. Asymptotic height as a predictor of growth and allometric characteristics in Malaysian rain forest trees (vol 83, pg 556, 1996). American Journal of Botany 83:1570-1570.

  うーむ， どれもわざわざ熱帯まで行ってやる必要のない研究ばかり， という気もするんだけど．
• 1220 終了． 1230 昼飯調達のため北大構内の旅にでる． 今日もいい天気． 中央ローンは戸外で昼飯たべてるヒトたち多数． 北大生協うろうろしてから研究室もどって昼飯 …… 食おうとしたんだけど， お茶部屋の院生密度が高くてなかなか近づけない．
• などとうだうだしてるうちに， 7F 実験室の雑用 PC につけてる CRT ディスプレイ壊れ連絡が …… うーむ， 私が D3 のときに買った X 端末専用機 (というのが当時あった) についてたやつじゃないか． そりゃ壊れますわな． 新たなる粗大ゴミ一個をまた一時ゴミ置場 (つまり私のいる部屋) に． JCC 製． 驚くべきことに， この したたかな 計算機会社は過去 10 年間の激動の時代を生きのびてしまって， いまだに存続している， とわかった． 何だか感慨ありますねえ ……
• ということで 1400 ごろ昼飯．
• 昼飯後にしばらくうだうだとしてから， また地衣類子器数 の階層ベイズモデルの説明かきつづき．
• しかしつくづく「わーぷろ」 (おうぷんおひすのらいたー) にはいらいらさせられる， というほどでもないけど楽しくない …… LaTeX はあんなに楽しいのに．
• 1700 すぎ， ひととーりモデル説明とか書けたかしらん， などと思ってると …… 後藤さんから改定原稿一式がおくられてきてトドマツ世界にひきもどされる．
• 1850 研究室発． 1905 帰宅． 晩飯．
• 2210 自宅発北大構内走． ゆっくり走って 2300 帰宅．
• [今日の運動]
  • 北大構内走 50 分間．
  • ストレッチ
• [今日の食卓]
  • 朝 (0730): 米麦 0.6 合． タマネギ・ジャガイモ・ニンジンの味噌汁．
  • 昼 (1400): 研究室お茶部屋． 食パン． チーズ．
  • 晩 (1920): 米麦 0.8 合． 寄せ豆腐． タマネギ・ジャガイモ・ニンジンの味噌汁．