Takeshi Toma

Mixed-power scaling of whole-plant respiration from seedlings to giant trees

The scaling of respiratory metabolism with body mass is one of the most pervasive phenomena in biology. Using a single allometric equation to characterize empirical scaling relationships and to evaluate alternative hypotheses about mechanisms has been controversial. We developed a method to directly measure respiration of 271 whole plants, spanning nine orders of magnitude in body mass, from small seedlings to large trees, and from tropical to boreal ecosystems. Our measurements include the roots, which have often been ignored. Rather than a single power-law relationship, our data are fit by a biphasic, mixed-power function. The allometric exponent varies continuously from 1 in the smallest plants to 3/4 in larger saplings and trees. Therefore, our findings support the recent findings of Reich et al. [Reich PB, Tjoelker MG, Machado JL, Oleksyn J (2006) Universal scaling of respiratory metabolism, size, and nitrogen in plants. Nature 439:457–461] and West, Brown, and Enquist [West GB, Brown JH, Enquist BJ (1997) A general model for the origin of allometric scaling laws in biology. Science 276:122 -126.]. The transition from linear to 3/4-power scaling may indicate fundamental physical and physiological constraints on the allocation of plant biomass between photosynthetic and nonphotosynthetic organs over the course of ontogenetic plant growth.

Dynamics of Burned Lowland Dipterocarp Forest Stands in Bukit Soeharto, East Kalimantan

Two of the world’s largest forest fires burned the lowland dipterocarp forests in East Kalimantan within a 15-year period. During the dry spell in 1982–83, wildfires in the Indonesian province of East Kalimantan affected about 3.6 million hectares of primary and secondary rainforest (Goldammer and Seibert 1990). From 1997 to 1998, severe droughts linked to another strong El Nino-Southern Oscillation (ENSO) event occurred, and resulted in a second immense forest fire in East Kalimantan (Chapter 3, this volume).

Tree Species Composition of a Burned Lowland Dipterocarp Forest in Bukit Soeharto, East Kalimantan

Tropical lowland evergreen rainforests on the Malay Peninsula and islands of the Sunda Shelf are distinguishable from similar types of vegetation of this class found on other continents by their abundance of dipterocarp species (Whitmore 1984). The floristic composition in lowland dipterocarp forests is distinctive because of the very large numbers of tree species represented by a small number of mature individuals, and the general ‘family dominance’ of Dipterocarpaceae, especially in terms of basal area (Richards 1996). The species richness of lowland dipterocarp forest in Borneo Island, for instance, is illustrated by the species-area curve for a forest at Wanariset in East Kalimantan (Kartawinata 1981a).

Leaf Gas Exchange and Canopy Structure in Wet and Drought Years in Macaranga conè;fera, a Tropical Pioneer Tree

Despite a high annual rainfall in the rainforest region, unusually prolonged and severe droughts occurred in eastern Borneo from June 1982 to May 1983 (Goldammer and Seibert 1990) and from June 1997 to April 1998 (Toma et al., Chapter 2, this volume). The prolonged droughts were linked to particularly strong El Nino-Southern Oscillation (ENSO) events. In the 1997-98 ENSO, there was no precipitation period from January 2 to April 15 (for 104 days), 1998 Figure 12.1. Although soil water potential was 0–45 kPa at a soil depth of 10 to 60 cm from May 1989 to April 1990 (normally wet years), it was 60–66 kPa from January to February 1998. When the soil water potential decreased (within 2 months of a period of no precipitation), both net photosynthetic rate (Pn)and water vapor stomatal conductance(g,)decreased in the uppermost canopy leaves of a climax tree,Dipterocarpus cornutusDyer Figure 12.1. Similar data were also found in the top canopy leaves of pioneer tree species,Macaranga conifera(Zoll.) Muell. Arg. andMacaranga gigantea(Reichb. f. & Zoll.) Muell. Arg.

In Situ Study of the Effects of Elevated Temperature on Photoinhibition in Climax and Pioneer Species

Understanding the abiotic and biotic factors for seedling growth and the ecophysiological responses against physiological stresses has been of great interest to ecologists, biologists, and foresters. Interactions of multiple environmental factors are relevant to the physiological performance of plants in nature (Ludlow 1987, Gamon and Pearcy 1989, 1990; Ishida et al. 1999a,b). For example, the inhibitory effects of strong light on photochemical capacity in leaves can be exacerbated by other stress conditions, such as cold (e.g., van Kijk and van Hasselt 1993, Leitsch et al. 1994), limited nitrogen supply (e.g., Ferrar and Osmond 1986), and water stress (e.g., Bjorkman and Powles 1984, Kao and Forseth 1992). In contrast to the large number of studies on the interactive effects of cold and high light intensity, there have been only a few studies on photoinhibition caused by a combination of high light intensity and high temperature (Ludlow 1987, Gamon and Pearcy 1990, Mulkey and Pearcy 1992, Koniger et al. 1998)

Biomass of a man-made forest of timber tree species in the humid tropics of West Java, Indonesia

Biomass of a mature man-made forest in West Java, Indonesia, was estimated to evaluate the carbon sequestration potential of plantation forest in the humid tropics. Twenty plots, each 0.25 ha in area and containing one to six planted species over 40 years of age and with closed canopies, were selected. Trunk dry mass was estimated from trunk diameter, tree height, and bulk density. Maximum trunk diameter (122 cm) was observed in a 46-year-old Khaya grandifoliola C. DC. tree, and the tallest tree (51 m) was a 46-year-old Shorea selanica (DC.) Blume. The largest trunk biomass (911 Mg ha−1) was achieved in the plot composed of two Khaya spp. Among the plots composed of indigeneous Dipterocarpaceae species, the largest trunk biomass was 635 Mg ha−1. These trunk biomasses were larger than those reported from primary rainforests in Southeast Asia (e.g., 403 Mg ha−1 in East Kalimantan, 522 and 368 Mg ha−1 in Peninsular Malaysia). The large biomass in this forest suggests that, given favorable conditions, man-made forests can accumulate the quantities of atmospheric carbon that were lost by the logging of primary forests in the humid tropics.

Overview of the Changing Forest Ecosystems in East Kalimantan

Increasingly, attention is being focused on tropical forests. This interest has been motivated by three main concerns: 1) Tropical forests harbor the greatest biological diversity on Earth; 2) they are a major component of the global carbon cycle; and 3) they provide forest goods and services to all sectors, from the local to the global scale. These three concerns often cause conflicting problems in forest management, and forest scientists and administrators are seeking a harmonious solution. Despite recent advances in the understanding of tropical forest ecosystems, knowledge is still insignificant in relation to the three concerns mentioned above. To establish verifiable forest management methods that are ecologically sound, economically viable, socially responsible, and environmentally acceptable, both administrators and scientists including those in the fields of socio-economics, plant ecology, eco-physiology, soil science, animal ecology, entomology, mycology, pathology, silviculture, and forestry have collected accurate and detailed information about the changing forest ecosystems in the tropics.