Analysis and simulation of dynamic forest architecture of tropical rain forests in southeast Asia.

Takashi Kohyama, Bullard Fellow in 1998-1999


I started my Bullard fellowship in mid September for 10 month in Harvard University. Main laboratory was in Harvard University Herbaria under Professor Peter Ashton, while I also frequently joined seminars in plant ecology at laboratory of Professor Fakhri Bazzaz, and participated in some seminars in Harvard Forest. I also made a seminar in Princeton University, and presented a paper in a symposium held in Japan, which commemorated Professor Otto Solbrig to win the International Prize of Biology for 1998. I am attending a workshop of forest dynamics modeling in mid July in Colorado State University.

My main focus as a Bullard fellow was on the functional understanding of species-rich mixed dipterocarp forests in southeast Asia. I mainly analyzed in earlier phase of the stay the data from two 1-ha permanent forest plots established in the basin of Landak River in West Kalimantan, Indonesian Borneo. Using three-year interval inventory, I estimated the demographic parameters, and simulated the dynamics of tree-size structure in gap-mosaic landscape. The steady state obtained by the simulation agreed well with the observed forest structure, suggesting that the forests were around an equilibrium. At the level of component tree species, I found that species differentiation in terms of trunk allometry, tree growth rate and recruitment rate was strongly related to observed maximum size, for 27 abundant tree species. This suggests that the attainable-size differentiation is one of important mechanisms of species coexistence. Along this line in latter phase, I started to examine the 50-ha plot data of Pasoh Nature Reserve, Peninsular Malaysia, with Peter Ashton and Matthew Potts (research student with Peter Ashton), finding that tradeoff relationships among vegetative growth, recruitment rate and maximum size were also well established for hundreds of tree species. Rare species tended to have smaller per-capita recruitment rate. Global scale gradient of tree species diversity was examined along forest architecture hypothesis (Kohyama 1993). I am discussing further collaboration in southeast Asian forest study with Peter Ashton and Stuart Davies. I am also planning with Fakhri Bazzaz possible collaborative study in two east-coast northern forest ecosystems, i.e. in New England and Hokkaido.


Expected Publications (exclusively under the Bullard Fellowship)

In press

Kohyama, T., Suzuki, E., Aiba, S. and Seino, T. 1999.
Functional differentiation and positive feedback enhancing plant biodiversity. In: M. Kato, ed., Biology of Biodiversity. Springer Verlag, Tokyo

Drafts

Kohyama, T., Suzuki, E., Partomihardjo, T. and Yamada, T.
Dynamic steady-state of patch-mosaic tree-size structure of a mixed dipterocarp forest regulated by local-crowding dependence. First Draft, June 7, 1999

Kohyama, T., Suzuki, E., Partomihardjo, T. and Yamada, T.
Maximum-size-related differentiation in architecture and demography among tree species in a mixed dipterocarp forest of West Kalimantan. First Draft, June 17, 1999

Kubo, T., Kohyama, T., Potts, M.D. and Ashton, P.S.
Mortality rate estimation, when inter-census intervals vary. Revised Draft, 7 May, 1999

Under preparation

Kohyama, T. with Potts, M.D., Ashton, P.S. and J. LaFrankie
Tradeoffs in demographic parameters among co-occurring tree species in Pasoh Nature Reserve.


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