Fumito Koike

Foliage-crown development and interaction in Quercus gilva and Q. acuta

In many natural forests, crown interactions occur among trees of various sizes (ages) and various species. Competition is greatly affected by size and species of interacting trees. Thus, an analysis should be made of interactions between trees of different species and different sizes. Interactions in a monospecific even-aged stand represent a special case, and can be inclused in this general situation. In this study, an interaction between trees of different species and sizes is examined by foliage-crown development, and a basic mechanism of foliage-crown interaction is presented

Reconstruction of two-dimensional tree and forest canopy profiles using photographs

(1) A point-quadrat method and computed tomography were used to reconstruct two-dimensional foliage density distributions in tree and forest canopies using many photographs taken from various positions in a canopy section. (2) The reconstructed canopy profile (the graphical representation of the foliage density distribution in a canopy section) obtained by computed tomography was similar to the pattern of leaf area density distribution obtained by the clipping method. The calculated foliage density was in direct proportion to the actual leaf area density. (3) Canopy profiles could be reconstructed with photographs taken from the ground level alone. (4) The method was applied to a warm-temperate, evergreen, broad-leaved forest, and a two-dimensional forest canopy structure was obtained quantitatively and nondestructively.

Plant traits as predictors of woody species dominance in climax forest communities

The dominance of a given tree or shrub species in a particular forest community may be determined by many ecological traits of the target species, as well as those of the surrounding species as its potential competitors. The present study was conducted to evaluate the possibility of predicting community status (species composition and dominance) on the basis of traits of local flora using statistical methods, and to visualize the mathematical function which determines species dominance. A general linear model and logistic regression were used for the statistical analysis. Dependent variables were designated as dominance and presence/absence of species in climax forest, with independent variables as vegetative and reproductive traits. Subalpine, cool-temperate, warm-temper- ate and subtropical climax rain forests in East Asia were studied. Quantitative prediction of climax community status could readily be made based on easily measured traits of local flora. Species composition and 74.6% of the total variance of species dominance were predicted based on two traits; maximum height and shade tolerance. Through applica- tion of this method, the capacity of an alien species to invade a climax forest community could possibly be pre- dicted prior to introduction of the alien species.

Canopy structure of a tropical rain forest and the nature of an unstratified upper layer

The two-dimensional distribution of foliage density was investigated in a vertical canopy section of forest in West Sumatra, using analysis of variance. No significant continuous upper canopy layer could be found. However, there was significant stratification with a dense foliage layer below 15 m. The structure of the upper canopy (higher than 15 m) had an erect structure rather than being stratified. Two hypotheses were examined to explain the unstratified upper canopy structure: it was due to incomplete growth in height of the trees, leading to an unstratified forest canopy even in mono-specific forest, or it was caused by a mixture of species with different potential for height growth. The latter hypothesis was supported by the observations on tree growth (...)

COLONIZATION BY WOODY PLANTS IN FRAGMENTED HABITATS OF A SUBURBAN LANDSCAPE

Many studies have estimated the parameters of metapopulation dynamics by assuming a steady-state habitat-oeeupation pattern by organisms. However, metapopulations of woody plants in suburban landseapes rarely attain a steady state owing to the long life spans of individuals. We eonstrueted a eolonization model for woody plants based on the distanee from a seed-souree patch containing mother trees. It is easy to determine colo- nization parameters with this method, which makes the method useful for eonservation planning. Distance from the seed source was the most important faetor for predieting the presence of juveniles in a destination patch. The probability of colonization was estimated as a logistie funetion of the distance from the nearest seed source. Patch-level simulations using actual eolonization parameters and forest distributions (based on field measurements) showed that about half the speeies studied in Yokohama (Japan) would fail to reeolonize the studied region for at least 20 generations. Moreover, pateh density was too sparse for 30% of the studied species, whieh will thus be unable to expand their distributions and reverse loeal extinetions. Dominant species of the regions elimax forest will not reaeh vaeant patehes, and normal vegetation sueeession will be obstructed.

Forecasting the range expansion of a recolonising wild boar Sus scrofa population

Recolonising native mammals have the potential to cause environmental and agricultural damage. However, if their future distribution can be predicted, effective control measures can be scheduled beforehand to prevent the onset of damage. In this study, we predicted the future range expansion of recolonising wild boar Sus scrofa populations in the Chiba Prefecture, Japan, using simulations. Wild boars were extinct in the Chiba Prefecture until the 1970s, but since then, a new naturalised population has spread, probably due to release for hunting. Recently a small, isolated, naturalised population was found in the northern part of the prefecture, which was considered to be a new release. We divided the Chiba Prefecture (5,156 km2) into 3-km grids and, based on nuisance control records, we examined the ‘presence’ of wild boar populations from 2002 to 2007 and in 2010. We simultaneously estimated habitat suitability and dispersal probability of the source population via range-expasion modelling. We predicted the future distribution by the use of stochastic simulations for 20 years after 2010. According to the simulations, the wild boar populations will expand into the southern and northern regions of the Chiba Prefecture at a rate of 2,153 km/year, and crop damage should be expected in these areas in the future. Range expansion into the northern region of the prefecture will be completed by around 2025. If the northern isolated population is removed, it will be possible to delay the range expansion for about five years. The eradication of a small isolated population in the northern Chiba Prefecture may have significant economic benefits because the crop production in this area is relatively large.

Predicting future invasion of an invasive alien tree in a Japanese oceanic island by process-based statistical models using recent distribution maps

Modelling and predicting the potential habitat and future range expansion of invasive species can help managers to mitigate the impact of such species. Because habitat suitability and the colonization process are key determinants of range expansion, inferences drawn from invasion patterns should be based on both attributes. To predict the potential habitat and expansion rate of the invasive tree Bischofia javanica on Hahajima Island, we used simultaneous models of habitat and dispersal to estimate the effect of environment and dispersal from the source population on the current distribution. We compared the fit and the estimated magnitudes of the environment and dispersal effects in the simultaneous models with those in habitat suitability and colonization kernel models. The values of Akaike’s information criterion for the simultaneous models were better than those of the habitat suitability and colonization kernel models, indicating that the current distribution of Bischofia was determined by both environment and dispersal. The simultaneous models predicted that the potential habitat of Bischofia would be larger than that predicted by the habitat suitability model. The potential habitat distribution and future invasion predicted by the simultaneous models will contribute to the development of specific landscape-scale management plans to control this invasive species.

Canopy structures and its effect on shoot growth and flowering in subalpine forests

Changes in foliage density distribution with altitude and its effect on shoot growth and flowering were studied in forest section planes (profiles) of subalpine forests and scrubs (Krummholz) in Nepal and Japan. Patterns of foliage in forest canopy were evaluated by an analysis of variance. Foliage densities were very high at high altitude canopies, but the change in spatial patterns along altitude differs in both areas. The spatial pattern of new shoot production was similar to that of current foliage density and was affected by the amount of foliage above the sample probably through light condition. Flowering of tall trees occurred in the surface of the upper canopy, but a shrub species flowered even under tree canopies.

Canopy dynamics estimated from shoot morphology in an evergreen broad-leaved forest

SummaryA forest canopy structure may be defined as the spatial distribution pattern of foliage density, and dynamics of canopy can be considered as changes of spatial distribution of foliage density. To study this process, the annual intrinsic growth factor (r) of foliage and the speed with which foliage shifts its position were estimated from shoot branching and shoot length. The spatial distributions of these parameters were obtained from a profile of evergreen broad-leaved forest. r was large in the upper canopy layer and canopy gap; this indicated the active development of foliage. This phenomenon may be a major reason for the existence of dense foliage in the upper canopy. The speed with which foliage shifts its position was high in the canopy gap. For dominant species, light conditions affected positively on the distribution of r.

BIRDS TRANSPORT NUTRIENTS TO FRAGMENTED FORESTS IN AN URBAN LANDSCAPE

The influence of urbanization on nutrient cycling is vaguely known. Here we document that birds, especially those increasing in urban areas (such as crows, Corvus macrorhynchos and C. corone), affect nutrient cycles. Using fecal traps, we measured phosphorus (P) and nitrogen (N) input from the excrement of birds in fragmented forests in an urban landscape. Sources of avian feces were examined on the basis of carbon (C), N, and P percentages and stable isotopes of delta15N and delta13C. Nitrogen and P input was aggregated in the urban landscape, being especially high at the forest where crows roosted during winter. The annual P input due to bird droppings (range 0.068-0.460 kg x ha(-1) x yr(-1); mean 0.167 kg x ha(-1) x yr(-1)) was 12.4% of the total of other pathways in typical forests and 52.9% in the evergreen forest where crows roosted. The annual N input due to bird droppings (range 0.44-3.49 kg x ha(-1) x yr(-1); mean 1.15 kg x ha(-1) x yr(-1)) was 5.2% of the total of other pathways in typical forests and 27.0% in the evergreen forest used by roosting crows. Expected sources of nutrients in feces included insects in the breeding season, fruits in autumn, and mammals and birds in winter. Stable isotopes suggested that the source of nutrients in forests used by roosting crows was from outside the forest. Therefore, birds played a significant role as transporters of nutrients from garbage (including fish, livestock, and/or C4 plants such as corn, with high delta15N and delta13C) in residential and business areas to fragmented evergreen forests, especially near their winter roosts.