þÿ<HTML> <HEAD> <TITLE>Takashi Kohyama ____ Paper abstracts </TITLE> </HEAD> <BODY bgcolor="#FFFFFF"> <P> <P><FONT COLOR=darkblue SIZE=+2><b> <DIV ALIGN=center><i>Paper Abstracts </b></i></FONT></div></P> </font> <HR WIDTH="100%"></P> <P> <P><A NAME="20"></A></P> <P><B><FONT COLOR="#800000" SIZE=+1> Density-Size Dynamics of Trees Simulated by a One-Sided Competition Model of Rain Forest Stands </FONT></B></P> </P> <B>Takashi Kohyama</B><BR> Ann. Bot. 70, 451-460 (1992) </P> Stand development processes from various initial densities were simulated employing a one-sided competition model of the size structure dynamics of trees in which the size, growth rate and the probability of survival of a tree are linearly depressed by the cumulative basal area of trees in larger size classes. All model functions and parameters were derived from permanent plot censuses in a warm-temperate rain forest in southern Japan. The simulated tree density-mean tree size trajectories using species-averaged parameters were similar to those previously reported for even-aged monocultures. An upper boundary of the density-size trajectories or the self-thinning line did not change when the recruitment of seedlings was taken into account. The observed variance of growth rate at a given size hardly affected the results of simulation. A simulation of a multi-species system composed of abundant three species showed the same density-size dynamics in terms of total yield as a species-averaged system, while not in terms of each species cohort. It was concluded that the established rules of competition-density effect and self-thinning in higher plants are due to one-sided competition among co-occurring plant individuals of similar life forms irrespective of species, thus rules are not at the level of individual species within communities.</P> Key words: Competition, yield, density effect, mixed stand, population, self-thinning, simulation, size distribution, warm-temperate rain forest.<BR> <P><IMG SRC="./image/green1.gif" ><A HREF="index.html#list"><I>Return </I></A></P></DIV> <HR WIDTH="100%"></P> <P> <P><A NAME="22"></A></P> <P><B><FONT COLOR="#800000" SIZE=+1> Size-structured tree populations in gap-dynamic forest: the forest architecture hypothesis for the stable coexistence of species </FONT></B></P> </P> <B>Takashi Kohyama</B><BR> J. Ecol. 81, 131-143. (1993) </P> 1. The forest architecture hypothesis of tree species coexistence proposed here was developed from a general model of size-structured tree populations in gap-dynamic rain forest. The model consists of a submodel describing the dynamics of the age distribution of local stands, which reflects gap-dynamic processes in a whole forest, and another describing the change in size distribution of trees in stands of each age. The model expresses the dynamics of both species-averaged systems and multi-species systems. </p> 2. In the model, the intensity of suppression of tree size growth, survival and seedling recruitment is a function of local crowding. Crowding is measured in each stand in terms of the cumulative basal area of trees of all species that are larger than the subject individual, while the potential rate of seedling recruitment is proportional to the basal area of mother trees in a whole forest. Tree mortality results either from thinning due to local crowding or from gap formation. Trees surviving gap formation contribute to regeneration in a newborn gap. </p> 3. Simulation was carried out using permanent plot data from a warm-temperate rain forest. The simulation for a whole tree population converged to a unique equilibrium state with a stationary stand age distribution and a stationary size distribution in each stand. Simulated size distributions matched observed distributions in gaps and closed stands.</p> 4. The dynamics of a multi-species system composed of representative canopy, subcanopy and understorey species (all non-pioneer but with different tolerance levels) was also simulated. Results showed convergence to a stable equilibrium coexistence within a limited range of species parameters. Although stable coexistence also resulted from the model without stand mosaic by means of the trade-off between potential maximum size and potential recruitment rate, inclusion of gap dynamics in the model widened the range of coexistence in this trade-off space and reduced the time for convergence to equilibrium. Gap dynamics provided further possibilities for coexistence by various trade-offs, e.g. between potential size growth rate and susceptibility to suppression of size growth rate. Results suggested the importance of vertical and horizontal structure of forest in maintaining tree species diversity. </P> Key words: community, multi-species model, one-sided competition, rain forest, stratification.<BR> <P><IMG SRC="./image/green1.gif" ><A HREF="index.html#list"><I>Return </I></A></P></DIV> <HR WIDTH="100%"></P> <P> <P><A NAME="23"></A></P> <P><B><FONT COLOR="#800000" SIZE=+1> Size-structure-based models of forest dynamics to interpret population- and community-level mechanisms </FONT></B></P> </P> <B>Takashi Kohyama</B><BR> J. Plant Res., 107, 107-116 (1994) </P> Functional size-structure-based models of forest tree population dynamics present a unifying explanation for population-level patterns and tree community organization. Density-dependent regulation can be explicitly replaced by the effect of size-structure-dependent suppression on demographic processes in functional size-structure models. This suppression effect sufficiently explains various patterns reported for crowded even-aged populations. Further, it stabilizes natural forest populations of overlapping generations at a stationary state with balanced recruitment and mortality. The spatial heterogeneity of light resources created by tree size structure offers an opportunity for multiple species to coexist by means of trade-offs between demographic parameters. The energy correlation of tree species diversity at a geographic scale is also attributable to the architectural feature of forests. </p> Key Words: coexistence, density dependence, gap dynamics, metapopulation, one-sided competition, tree community, tree population, size structure, species diversity<BR> <P><IMG SRC="./image/green1.gif" ><A HREF="index.html#list"><I>Return </I></A></P></DIV> <HR WIDTH="100%"></P> <P> <P><A NAME="24"></A></P> <P><B><FONT COLOR="#800000" SIZE=+1> Below- and above-ground allometries of shade-tolerant seedlings in a Japanese warm-temperate rain forest </FONT></B></P> </P> <B>Takashi Kohyama and Peter J. Grubb</B><BR> Funct. Ecol., 8, 229-236 (1994) </P> 1. A comparative study has been made of the allometric relationships among below-ground and above-ground dimensions of seedlings (6.5-27 cm tall) of 14 abundant shade-tolerant species taken from the forest floor in a warm-temperate rain forest on Yakushima Island, southern Japan. </p> 2. The allometric lines between below-ground dimensions are significantly different between species, which reflects the differentiation between the species developing tap-roots and those developing horizontal fine roots in the same forest. The difference correlates with a difference in seed size, but not with height at maturity or habitat (ridge versus slope or gully). It is hypothesized that the differences in root architecture are related to ÿ”choicesÿ• in micro-site for establishment, the large-seeded tap-rooted species being better suited to soft soil and deep litter, and the small-seeded lateral-rooters to rocky soil and a lack of litter. </p> 3. The allometric relationship relating below- and above-ground dry mass is not sufficient to characterize a speciesÿ• architecture; a species may have a large ratio of root mass to shoot mass but a low ratio of fine-root length to leaf area. </p> 4. Interspecific differentiation in below-ground allometries at the seedling stage is not correlated with that in above-ground allometries at the seedling stage or with that in above-ground allometries at the sapling stage with developed branching architecture. Allometric ÿ”designÿ• in architecture at the sapling stage (related to earlier or later canopy-gap formation) is variously combined with that at the seedling stage (related to the micro-site of establishment).</p> Key words: architecture, fine roots, micro-site, sapling, seed size, seedling, tap-root<br> <P><IMG SRC="./image/green1.gif" ><A HREF="index.html#list"><I>Return </I></A></P></DIV> <HR WIDTH="100%"></P> <P> <P><A NAME="25"></A></P> <P><B><FONT COLOR="#800000" SIZE=+1> Spatial distribution pattern of representative tree species in a foothill rain forest in West Sumatra </FONT></B></P> </P> <B>Takashi Kohyama, Eizi Suzuki and Mitsuru Hotta</B><BR> Tropics, 4, 1-15 (1994) </P> Spatial distribution was analysed for all plot trees and representative tree species in two duplicate 1-ha plots established in a foothill rain forest 16 km west from Padang, West Sumatra, Indonesia. All tree trunks of which dbh >= 8 cm distributed randomly. Spatial correlation between dead trees and recruited trees for the 8-year period was locally negative while broadly positive, suggesting that the random spatial pattern is dynamically maintained through mechanisms of density-dependent regulation. </p> All of five abundant canopy/subcanopy non-pioneer species, i.e. <i>Hopea dryobalanoides</i>, <i>Gonystylus forbesii</i>, <i>Cleistanthus glandulosus</i>, <i>Mastixia trichotoma</i>, and <i>Grewia florida</i>, and typical pioneer <i>Macaranga</i> spp., including <i>M. gigantea</i>, <i>M. hypoleuca</i>, <i>M. pruinosa</i> and <i>M. triloba</i>, showed more clumped distribution particularly for smaller size classes. Two subcanopy non-pioneer species, <i>Mastixia</i> and <i>Grewia</i> showed a shift from monotonous-decreasing density with height in one over-mature plot with larger gap area to bimodal height distribution in the other mature plot with smaller gap area. They also showed similar tendency in spatial pattern that the negative spatial correlation shifted from nearby size classes to seedling (< 1 m high) versus tall tree (>= 10 m high) classes. Such pattern was also observed for gap-demanding <i>Macaranga</i> spp., and they were concluded to be less-tolerant species as compared with <i>Hopea</i>, <i>Gonystylus</i> and <i>Cleistanthus</i>, in which no height distribution difference nor spatial pattern difference was observed between two plots. These more-tolerant species showed positive correlation between tall trees and seedlings, while no correlation between tall trees and poles (1-10 m high). Results reflect the dynamic species alternation of tree species within a limited area of forest.</p> Key Words: <i>Cleistanthus glandulosus </i>/ <i>Gonystylus forbesii</i> / <i>Grewia florida</i> / <i>Hopea dryobalanoides</i> / Indonesia / <i>Macaranga</i> spp. / <i>Mastixia trichotoma</i> /spatial pattern / tropical rain forest<BR> <P><IMG SRC="./image/green1.gif" ><A HREF="index.html#list"><I>Return </I></A></P></DIV> <HR WIDTH="100%"></P> <P> <P><A NAME="29"></A></P> <P><B><FONT COLOR="#800000" SIZE=+1> A size-distribution-based model of forest dynamics along a latitudinal environmental gradient </FONT></B></P> </P> <B>Takashi Kohyama and Nanako Shigesada</B><BR> Vegetatio, 121, 117-126 (1995) </P> A geographically extended model of the dynamics of tree size structure of forests is proposed to simulate the change of forest zonation along latitude in response to global environmental change. To predict the response of forests to global change, it is necessary to construct functional models of forest tree populations. The size-structure-based model requires far less memory and steps of calculation compared with individual-based models, and it is easy to incorporate the dimension of geographic locations into the model to describe large-scale dynamics of forest-type distributions. The effect of increasing size growth rate, expected from increasing atmospheric carbon dioxide, was diminished at the stand-level basal area density, because of regulation by one-sided competition. Model simulations of a century-long global warming at around 3C predicted that (1) biomass changed in resident forests rather simultaneously in response to warming, and that (2) there was a considerable time lag in movement at the boundaries of different forest types, particularly under the existence of resident forest types that would be finally replaced. It required several thousand years after a century-long warming spell for forest types to attain new steady-state distributions after shifting. As a consequence, global warming created a zigzag pattern of biomass distribution along a latitudinal gradient, i.e., an increase in the cooler-side boundary of forest types and a decrease in the warmer-side boundary. <HR WIDTH="100%"></P> <P> <P><A NAME="33"></A></P> <P><B><FONT COLOR="#800000" SIZE=+1> The role of architecture in enhancing plant species diversity </FONT></B></P> </P> <B>Takashi Kohyama</B><BR> Biodiversity: an ecological perspective (ed. by T. Abe, S.A. Levin and M. Higashi), pp. 21-33. Springer, NY (1996) </P> Recent studies on terrestrial plant systems show that canopy architecture of vegetation can promote a state of stable coexistence between plant species. The vertical gradient of light resources and its horizontal variation, reflecting a shifting gap mosaic, play key roles. Trade-offs between demographic parameters required among species for coexistence can be explained on a physiological basis. Above-ground architecture is more persistent in forest systems than other plant systems, thus its role in community organization is different among systems. Forest architecture effectively explains the prevailing global-scale correlation between available energy and tree species diversity. In architectural systems, biomass and productivity contribute multiplicatively to increase the number of species that can coexist. A high gap formation rate alone has an effect of reducing both architectural development and species diversity. For plants other than trees, less persistent above-ground architecture results in less clear global patterns of species diversity. The time scale of responses of plant systems to current global climatic change and to far longer evolution processes are dependent on their architectural properties.</p> Key Words: coexistence, competition, ecosystem, latitudinal gradient, primary production, resource structure, size structure, tree community.<BR> <P><IMG SRC="./image/green1.gif" ><A HREF="index.html#list"><I>Return </I></A></P></DIV> <HR WIDTH="100%"></P> <P> <P><A NAME="35"></A></P> <P><B><FONT COLOR="#800000" SIZE=+1> Dynamics of primary and secondary warm-temperate rain forests in Yakushima Island </FONT></B></P> </P> <B>Takashi Kohyama and Shin-ichiro Aiba</B><BR> Tropics, 6, 383-392 (1997) </P> We describe the structural and dynamic feature of warm-temperate rain forests in foothill and lower montane zones of Yakushima Island, with particular reference to their potential of self-restoration. Forest-canopy dominant is Distylium racemosum of Hamamelidaceae. Codominant species belong to Fagaceae, Lauraceae, Symplocaceae, and Theaceae. Typical primary forest stand is characterized by high biomass stock (ca. 330 t/ha) relative to short canopy stature (ca. 20 m). Though the forest is repeatedly disturbed by typhoons, the gap-area ratio in primary stands is less than 10%. Mortality amounted ca. 0.02 per year suggesting 50-year turnover of trees. ÿŠOn the basis of dynamic data from permanent plots for more than 10 years (mortality, recruitment rate and size growth rate), observed size structure was sufficiently reconstructed as a steady state. Allometric and architectural differentiation among the 14 abundant species were changed along their life history. Secondary stands of warm-temperate rain forest are distributed near inhabited land. Majorities of secondary stand trees are coppice-origin primary stand species, while accompanied by deciduous pioneer trees. Tree growth rate of secondary stands is so high that the biomass-level recovery to the primary-stand state takes only 50 years after clear felling. Quick recovery of stands after clear-felling is also owing to the diversified traits among component tree species.</P> Key words: allometry / biomass / species diversity / simulation / steady state / typhoon / warm-temperate rain forest<BR> <P><IMG SRC="./image/green1.gif" ><A HREF="index.html#list"><I>Return </I></A></P></DIV> <HR WIDTH="100%"></P> <P> <P><A NAME="38"></A></P> <P><B><FONT COLOR="#800000" SIZE=+1> Recruitment rates in forest plots: Gf estimates using growth rates and size distributions. </FONT></B></P> </P> <B>Takashi Kohyama and Takenori Takada</B><BR> J. Ecol., 86, 633-639 (1998) </P> 1 In censuses of tree populations in permanent plots, short census intervals and small population size lead to uncertainty in the observed recruitment rate of a minimum size. Increasing the census interval however underestimates the rate because of unrecorded 'recruit and die' events.</p> 2 We propose a new Gf procedure for estimation of recruitment rates. Recruitment rate per area is obtained by multiplication of the density in the smallest size class (f) and the average size growth rate in that class (G) divided by the width of the class. This procedure is valid when the size distribution of the population examined is continuous with size.</p> 3 When tree size structure is negative-exponentially distributed, as is often the case in natural rain forest populations, the Gf estimate of the recruitment rate for a given size class is least biased close to the midpoint size of this class.</p> 4 Gf estimates agreed well with census estimates of recruitment rate from permanent plots in rain forests. A tendency for Gf estimates to be larger than census estimates disappeared when census estimates were corrected for mortality after recruitment.</p> 5 The effects of plot size, census interval, and variation in growth rate on estimates of recruitment rate were simulated using model populations. Small plot size caused substantially more among-plot deviation for the census count of recruitment events than for the Gf estimate. The census recruitment rate also showed larger variation among plots for shorter intervals, than the Gf estimate which was independent of census interval. The Gf estimates are therefore more accurate than census counts in many situations. More than several tens of trees were needed in a size class to allow a reliable Gf estimates.</p> Key Words: demography, model population, rain forests, recruitment rate, size structure, transition rate, tree population.<br> <P><IMG SRC="./image/green1.gif" ><A HREF="index.html#list"><I>Return </I></A></P></DIV> <HR WIDTH="100%"></P> <P><A NAME="42"></A></P> <P><B><FONT COLOR="#800000" SIZE=+1> Dynamic steady state of patch-mosaic tree-size structure of a mixed dipterocarp forest regulated by local crowding. </FONT></B></P> </P> <B>Takashi Kohyama , Eizi Suzuki, Tukirin Partomihardjo, and Toshihiro Yamada</B><BR> Ecological Research, 16, 85-98 (2000) </P> A patch-age- and tree-size-structured simulator was applied to demonstrate the landscape dynamics of a lowland mixed dipterocarp forest, using census data over a three-year interval from two 1-ha plots in northern West Kalimantan, Indonesia (Western Borneo). Tree growth rate and recruitment rate were estimated as functions of tree size and local crowding. The effect of local crowding was assumed to be one-sided through light competition, where the basal area for larger trees than a target tree inside the circle of 10-m radius around the target was employed as the index of crowding. Estimated parameters were similar between the two plots. Tree mortality was expressed by descending function of tree size with asymptotic mortality for large trees corresponding to the gap formation rate. One parameter specifying the survival of trees at gap formation, required for the landscape-level simulation of a shifting-gap mosaic, was left undetermined from plot census data. Through simulation, this parameter was estimated so as to best fit the observed among-patch variation in terms of local basal area. The overall time course of simulation and tree size structure were not sensitive to this parameter, suggesting that one-sided competition along vertical forest profile is stronger determinant of average forest structure than among-patch horizontal heterogeneity in this forest. Simulated dynamic steady state successfully reproduced the observed forest architecture in the gap-dynamic landscape. It took about 400 years for a vacant landscape to be replaced by a steady-state architecture of forest. Sensitivity analysis suggested that steady-state basal area and biomass were most sensitive to changing gap-formation rate and intrinsic size growth rate.</p> Keywords: Advance regeneration; Landscape; Model; Patch age; Gap mosaic; Tropical rain forest.<br> <P><IMG SRC="./image/green1.gif" ><A HREF="index.html#list"><I>Return </I></A></P></DIV> <HR WIDTH="100%"></P> <P><A NAME="48"></A></P> <P><B><FONT COLOR="#800000" SIZE=+1> Tree species differentiation in growth, recruitment and allometry in relation to maximum height in a Bornean mixed dipterocarp forest. </FONT></B></P> </P> <B>Takashi Kohyama , Eizi Suzuki, Tukirin Partomihardjo, Toshihiro Yamada, and Takuya Kubo</B><BR> J. Ecol., in press (2003) </P> <p><b>1</b> Maximum attainable height varies greatly between tree species in tropical rain forests and covaries with demographic and allometric traits. We examined these relationships in 27 abundant tree species in a mixed dipterocarp forest. These species were monitored over three years in two 1-ha plots in western Borneo. A 95-percentile upper height limit was used to represent maximum height, to avoid sample size differences among populations.</p> <p><b>2</b> Average growth rate in trunk diameter was regressed against trunk diameter using a maximum likelihood model and assuming that growth rates were exponentially distributed around the average. Estimated average growth rate at small trunk diameters (up to 11 cm) was independent of maximum height among the 27 species, while the degree of growth reduction at larger diameters was larger for species with smaller maximum height.</p> <p><b>3</b> The recruitment rate efficiency of saplings was negatively correlated with maximum height, regardless of the measure used to assess species abundance. In particular, sapling recruitment per unit basal area declined greatly with increasing maximum height, consistent with model predictions of the traits required for the stable coexistence of species at different heights within the canopy. </p> <p><b>4</b> allometric analyses showed that understorey species had shorter heights at the same trunk diameter, and deeper crowns at the same tree height, than canopy species. Therefore, understorey species showed adaptive morphology to deep shade.</p> <p><b>5</b> The regressed size-dependent pattern of average growth rate and an assumption that the population was in a steady state readily explained the observed trunk diameter distributions for 21 species among 27 examined. These species, for which the projected size distribution hardly changed when the natural increase or decrease of the population was set at ³ = +0.005 year 1, had mortality rates of more than four times the value of ³. </p> Key words: coexistence, equilibrium, demography, forest architecture hypothesis, upper height limit, size distribution, tropical rain forest.<br> <P><IMG SRC="./image/green1.gif" ><A HREF="index.html#list"><I>Return </I></A></P></DIV> <HR WIDTH="100%"></P> <P><IMG SRC="./image/green1.gif" ><A HREF="index.html"><I>To Kohyama page </I></A></P></DIV> <P><IMG SRC="./image/green1.gif"><I><A HREF="http://hosho.ees.hokudai.ac.jp/index-e.htm">To Lab. Regional Ecosystems page</A></I> <BR> </P> </td></tr></table></center> </BODY> </HTML>