Interactive effects of leaf age and self-shading on leaf structure,photosynthetic capacity and chlorophyll fluorescence in the rain forest tree,Dryobalanops aromatica

In the tropical canopy tree, Dryobalanops aromatica Gaertn. f., upper-canopy leaves (UL) develop under sunlit conditions but are subjected to self-shading within the crown as they age. In contrast, lower-canopy leaves (LL) are exposed to uniform dim light conditions throughout their life span. By comparing leaf morphology and physiology of UL and LL, variations in leaf characteristics were related to leaf age and self-shading. Mass-based chlorophyll (chl) concentration and the chlorophyll/nitrogen (chl/N) ratio were lower and the chl a/b ratio was higher in UL than in LL. In UL, the chl/N ratio gradually increased and the chl a/b ratio gradually decreased with leaf aging, whereas these ratios remained unchanged with leaf age in LL. The effective quantum yield of photosystem II (PSII) (DeltaF/F(m)') at a given irradiance remained unchanged with leaf age in LL, whereas DeltaF/F(m)' changed with leaf age in UL. These data indicate N reallocation within the leaves from carbon fixation components to light harvesting components and a dynamic regulation of photochemical processes of PSII in response to increased self-shading of UL. Despite the difference in light environment with leaf age between UL and LL, maximum photosynthetic rates and nitrogen-use efficiency decreased with leaf aging in both UL and LL. Constancy in the chl/N ratio with leaf age in LL indicated that the decrease in photosynthetic capacity was caused by effects other than shading, such as leaf aging. We conclude that N reallocation and acclimation of PSII to self-shading occurred even in mature leaves, whereas the change in photosynthetic capacity with leaf age was more conservative.     

Protective effect of floor cover against soil erosion on steep slopes forested with <Emphasis Type="Italic">Chamaecyparis obtusa</Emphasis> (hinoki) and other species

 We evaluated the protective effects of floor cover against soil erosion in three types of forest located on steep slopes under a humid climate: 22- and 34-year-old Chamaecyparis obtusa (hinoki), 34-year-old Cryptomeria japonica (sugi), and 62-year-old Pinus densiflora (red pine) stands. We measured sediment transport rates (sediment mass passing through one meter of contour width per millimeter of rainfall), using sediment traps, before and after removing floor cover. Raindrop splash erosion was dominant in the experimental stands. Floor cover percentage (FCP) during the preremoval stage varied from 50% to 100% among the four stands, and sediment transport rates ranged from 0.0079 to 1.7 g m⁻¹ mm⁻¹. The rates increased to 1.5–5.6 g m⁻¹ mm⁻¹ immediately after removing floor cover, and remained high throughout the experiment. The presence of physical cover near the ground has a crucial effect on sediment transport on forested slopes. The protective effect ratio (the ratio of the sediment transport rate in a control plot to that in the removal plot) in a young hinoki stand, in which the FCP decreased markedly, was 0.3 at most, which is close to the rate for bare ground. The protective effect ratio in the red pine stand was ≤0.003. We concluded that the protective effect of floor cover in undisturbed forests in Japan differs by over two orders of magnitude, based on comparisons with previous studies. Received: March 11, 2002 / Accepted: August 16, 2002 Present address: Department of Forest Site Environment, Forestry and Forest Products Research Institute, Ibaraki 305-8687 Japan Tel. +81-298-73-3211; Fax +81-298-74-3720 e-mail: miura@affrc.go.jp Present address: Department of Forest Site Environment, Forestry and Forest Products Research Institute, Ibaraki 305-8687 Japan Tel. +81-298-73-3211; Fax +81-298-74-3720 e-mail: miura@affrc.go.jp Acknowledgments This study was supported by the Research Council of the Ministry of Agriculture, Forestry, and Fisheries, of Japan. We thank H. Ujihara, S. Ujihara, and M. Ogasawara in Otoyo, Kochi, who provided the experimental stands used in this study. We also thank K. Hirai, S. Kuramoto, E. Kodani, and the rest of the staff at the Shikoku Research Center, Forestry and Forest Products Research Institute, for their help in conducting the experiments. Correspondence to:S. Miura     

The process of decline of an endangered tree species,Pinus armandii Franch. var.amamiana (Koidz.) Hatusima, on the southern slope of Mt. Hasa-dake in Yaku-shima Island

The process of decline of an endangered tree species,Pinus armandii var.amamiana, was monitored on the southern slope of Mt. Hasa-dake in Yaku-shima Island from 1994 to 1998. There are 163 trees ofP. armandii var.amamiana over 1.3 m in height. They are distributed on steep ridges and rocks with a thin soil layer mostly consisting of friable granite. During the monitoring period, 21 trees ofP. armandii var.amamiana died and the mortality rate was 12.9%. Dead trees were categorized into three types: standing, uprooted and landslide. The uprooted- and landslide-typed dead trees were found only after a severe typhoon struck Yaku-shima Island. This suggests that the combination of fragile site conditions and severe typhoons play an important role in the process of decline ofP. armandii var.amamiana. The standing-typed dead trees were presumed to have been killed by pine wilt disease, accounting for 71.4% of the dead trees. However,Bursaphelenchus xylophilus, the cause of pine wilt disease, was not detected from any of the wood chips or branch samples from the standing-typed dead trees ofP. armandii var.amamiana. This might indicate that some factor(s) other than pine wilt disease could be responsible for the standing-typed death ofP. armandii var.amamiana in natural habitats. A part of this paper was presented at the 109th Meeting of the Japanese Forestry Society.     

Atmospheric lead and cadmium deposition within forests in the Kanto district, Japan

Atmospheric lead and cadmium deposition in bulk precipitation and throughfall was investigated at four forests in the Kanto district, Japan, to assess the impact of human activities on the environmental health of forests. Annual lead and cadmium depositions in bulk precipitation ranged from 8.9 to 25.7 g ha⁻¹ year⁻¹ and from 0.77 to 1.30 g ha⁻¹ year⁻¹, respectively. Lead and cadmium deposition increased in the summer at every forest due to large amounts of rainfall. At one of the forests, the depositions were also high in the winter due to heavy snowfall. These depositions were similar to recent depositions observed at other rural and urban sites in Japan and several forests in Europe and North America after 1990. These results indicate that although anthropogenic lead and cadmium are deposited at these rates over wide areas, depositions are still higher than in remote areas.     

Quantification and Understanding of Above and Belowground Biomass in Medium Saline Zone of the Sundarbans,Bangladesh: The Relationships with Forest Attributes

ABSTRACT

The relationship between stand attributes and biomass accumulation pattern in a mangrove forest has been intensively studied in this study. We assessed above (AGM) and belowground mass (BGM) and examined the relationship between forest attributes and aboveground mass in the Sundarbans, Bangladesh. The study was conducted with 18 plots having total area of 1.08 ha. The mean AGM and BGM of the study sites were 234.08 and 132.85 Mg ha^?1 respectively. H. fomes contributed the highest amount (82.9% of total AGM and 80.53% of total BGM) of above (193.56 Mg ha^?1) and belowground mass (107.09 Mg ha^?1) at the study site. Our study revealed structural attributes (tree diameter, height, and basal area) positively correlated with AGM. In contrast, species richness and species diversity negatively correlated with AGM. Our study indicated that lack of positive relationship between species diversity and AGM which may be attributable to high AGM of the dominant species (H. fomes) and may have a considerable consequence in AGM of the study area. Thus, maintaining large trees (DBH and height) rather than species diversity in the Sundarbans mangrove forest might be an effective approach for increasing aboveground mass.     

Differential overstory leaf flushing contributes to the formation of a patchy understory

Understory individuals were found to form patches in a 100-year-old deciduous broad-leaved forest. The closed forest canopy was uniform, and so the light conditions at various locations across the forest floor differed little after the leaf flush of the overstory. To explain the distribution pattern in the understory, a hypothesis was proposed: in spring, the forest floor is divided into patches according to the timing of leaf flush of the overstory individuals, and the light conditions are more favorable for understory plants under the crowns of trees with later-flushing leaves. In the plot, three groups of early, intermediate, and late, were recognized in the overstory concerning the timing of leaf flush. As for the start of leaf flush, a difference of 31.6 days was recognized among tree species, and for the end of leaf flush, a difference of 40.3 days. In the spring of 1998, the relative photosynthetic-photon-flux density under an intensively studiedCastanea crenata tree (late-flushing species) usually showed higher values than that under a similarly studiedAcer mono tree (early-flushing species). Analysis of the spatial-distribution pattern using Morisita’s1δ index revealed that the understory community had an aggregated distribution. In the overstory, the late- and the intermediate-flushing-species groups showed aggregated distributions, while the early-flushing-species group showed random distribution. Spatial correlation between the understory and the overstory was analyzed by using Morisita’sRδ index. The distribution of whole understory community spatially co-occurred with that of the late-flushing-species group of the overstory. In contrast, the understory community was less developed below the members of the early-flushing-species group of the overstory. We consider that the data presented here support our hypothesis, and we suggest that the growth and survival of understory individuals were promoted in the places receiving light for long periods in spring.     

Termiticidal activity of wood vinegar, its components and their homologues

The termiticidal activity of wood vinegar, its components, and their homologues have been studied. Three kinds of wood vinegar made from the mixed chips ofCryptomeria japonlca andPseudotsga menziesii (wood vinegar A),Quercus serrata (wood vinegar B), andPinus densiflora (wood vinegar C) exhibited high termiticidal activities againstReticulitermes speratus. Acetic acid, which is the largest content of wood vinegar, exhibited high termiticidal acitivity. The contents of organic fraction of wood vinegars and acetic acid might be responsible for the differences in termiticidal activities among these wood vinegars. The structure and termiticidal activity relations of phenols were studied. Phenol with some substituents revealed higher termiticidal activity than benzene derivatives, which have no hydroxyl group; an ortho substituent of phenol plays an important role in termiticidal activity. It has become apparent that high termiticidal activity cannot be obtained by a phenolic hydroxyl group alone; it can be obtained, however, by some substituents, especially an ortho substituent in addition to a phenolic hydroxyl group. The bulkiness of the substituent at the ortho position participates in termiticidal activity; activity decreases as the size of an ortho substituent increases. It is thought that the interaction at the receptor site of termites is affected by the increased size of the ortho substituent.     

Chemical structures of the condensed tannins in the fruits of Diospyros species

The structural variety of the condensed tannins (proanthocyanidins) in the fruits of 16Diospyros species are reported. Eleven species contained condensed tannins mostly consisting of a mixture of catechin (CA) and gallocatechin (GCA) repeating units; the other five species did not. The GCA content in the CA-GCA total varied from 0.3% to 84.6%. The number of esterified gallic acid per one flavan repeating unit (degree of galloylation, DG) ranged from 0.01 to 0.89. The GCA content was found to be proportional to the DG values. Thus, 16Diospyros species tested may be classified into five groups by the analytical data of their condensed tannins. It may be interesting to compare their structural characteristics with those of the condensed tannins in other fruits, leaves, woods, and barks from the viewpoint of their biosynthesis and function in the plants.Part of this paper was presented at the 46th Annual Meeting of the Japan Wood Research Society, Tokyo, April 1995