Japanese Temperate Forest Research Articles

Effects of rhizospheres on the community composition of Collembola in a temperate forest

Influence of living roots on the community composition of Collembola was investigated in a coniferous forest of Chamaecyparis obtusa. We conducted a buried pot experiment that constructed two different systems for carbon (C) availability. We used two types of pots with or without a C. obtusa seedling. The former pots were used to make a system with soil including living roots (i.e. a system based on root-derived and litter-derived C), while the latter was equivalent to soil system without living roots (i.e. a system based on litter-derived C). After 8 months, we harvested the pots and examined the collembolan community and environmental factors. The presence of living roots affected collembolan abundance and species-specific responses. These changes could be explained in terms of leaf biomass of the seedlings, indicating a possible linkage between above-ground productivity and collembolan community. Given the possibility that root-derived C is associated with aboveground plant mass, we speculate that collembolan community responds to root-derived C. The three dominant species, which are widespread in Japanese temperate forests, were more abundant in the presence of living roots. Moreover they were positively correlated with leaf biomass in the system with a seedling, again suggesting the fundamental importance of living roots for the organisation of the collembolan community.

Calibration of tipping‐bucket flow meters and rain gauges to measure gross rainfall, throughfall, and stemflow applied to data from a Japanese temperate coniferous forest and a Cambodian tropical deciduous forest

AbstractTipping‐bucket flow meter and rain gauge (TBFM/TBRG) are widely used for the measurement of gross rainfall (GR), throughfall (TF), and stemflow (SF) to evaluate the amount of interception loss (I). However, TBFM/TBRG cannot measure the inflow rate during tipping and underestimates the inflow rate. To correct this systematic bias, 33 total calibrations were conducted for five types of TBFM/TBRG in the laboratory. The tipping time increased with the bucket volume, and the underestimation during one tip was higher for TBFM/TBRG of larger capacity. With the use of the scaled actual inflow rate and the actual volume of a single tip from the measured static volume of a single tip when the inflow rate is zero, the common calibration curves were obtained as quadratic equations for each of the five types within an error range of ±3%. We measured GR and TF by using TBRG and TBFM with a resolution of 0.2 mm and measured SF by TBRG with a single‐tip static volume of 15.7 cm3 in a Japanese temperate coniferous forest (TCF) and a Cambodian tropical deciduous forest (TDF). At both sites, the calibration curves needed to be applied to obtain GR, TF, and SF on an event scale with an underestimation degree of less than 3%. Without applying any calibrations, the higher rainfall intensities in TDF caused larger underestimations of GR, TF, and SF and larger overestimations of I compared with results for TCF. On an annual scale, the degree of overestimation of I relative to GR (ΔI/GR) was 1.2% in TCF and 3.5% in TDF, and ΔI/I was at least 10% at both sites. Copyright © 2012 John Wiley & Sons, Ltd.

Fleshy fruit characteristics in a temperate deciduous forest of Japan: how unique are they?

This study investigated the fleshy fruit characteristics of 28 woody species in a Japanese temperate forest where large sedentary seed-dispersing mammals are present. We tested whether the findings in previous studies in temperate forests of Europe and North America are universal or not. Results have suggested that fruits of all species were eaten both by birds and mammals except for four species with larger fruits, which were eaten only by mammals. A gradient was found from a syndrome characterized by small, oily, and large-seeded fruits to a syndrome characterized by large, succulent, non-oily, and small-seeded fruits. The sizes and colors of the fruits were not conspicuously different from previous findings in Europe and North America. On the other hand, nitrogen and lipids in the fleshy part did not show seasonally increasing trends, or even seasonally decreasing trends in terms of dry weight. This result, suggesting the absence of community-level adaptation of fruit traits to migratory bird dispersers, contrasted with findings in Europe and North America. Large sedentary arboreal or tree-climbing mammals may have a greater effect on the evolution of fruit-disperser relations than opportunistic migratory birds.

Seasonal difference in the effects of fragmentation on seed dispersal by birds in Japanese temperate forests

AbstractMany studies have demonstrated that forest fragmentation reduces populations of animal species and causes local extinction, triggering many cascading effects. The effect of fragmentation on animals can be exerted through various processes, but such effects have been understudied. In this study, we posed the possibility of differences in the seasonal effects of fragmentation on frugivorous birds and their dispersal of seeds belonging to five tree species. We hypothesized that these effects may be caused by birds and their habitat selection for suitable breeding forests. We compared the abundance and species richness of frugivorous birds and the number of bird‐removed fruits between a well‐preserved and a fragmented temperate forest for two consecutive years. The abundance of birds was lower in the fragmented compared to the well‐preserved forest during the breeding season, although no clear differences in species richness were observed. In contrast, similar decreases in bird abundance were not observed during the migratory season. After controlling for variation in crop size, the number of bird‐removed fruits was lower in the fragmented forest compared to the well‐preserved forest during the breeding season, but there was no such tendency during the migratory season. These results indicate that evaluations regarding the effects of fragmentation on seed dispersal that do not consider seasonal factors may lead to erroneous conclusions. This study suggests that the effects of fragmentation can be exerted though various processes, many of which remain poorly studied and warrant further examination.

Early-stage impacts of sika deer on structure and function of the soil microbial food webs in a temperate forest: A large-scale experiment

Modification of forest vegetation caused by an overabundance of mammalian herbivores has been reported in temperate and subarctic regions all over the world. However, the indirect effects of these herbivores on the structure and functions of soil decomposer systems are not fully understood, especially in temperate forests. We investigated the early effects of sika deer invasion on soil decomposer systems in a Japanese temperate forest using two large-scale experimental enclosures with low and high densities of deer (LD: 25ha, 4deerkm−2; HD: 6.25ha, 16deerkm−2) including control plots without deer (WD). Three years after deer introduction the understory cover of dwarf bamboo (Sasa nipponica) declined due to deer browsing in both enclosures. At the same time, measurements were made of the soil microbial community, soil nematode community, soil nitrogen (N) mineralization rate, and carbon (C) and N content in dwarf bamboo leaves. In LD, soil microbial biomass was lower from WD, probably due to the decrease of fresh aboveground litter from dwarf bamboo. Surprisingly, there were no cascading effects on total abundance of soil nematodes and soil total N mineralization potential which were unaffected by deer in the LD treatment, while soil NH4+-N content was lower and soil nematode community structure was different (abundance of 4 families was higher and that of 3 families was lower, but the functional structure was not different) from WD. Specifically, the responses to deer introduction varied between microbes and nematodes, and the change of balance in the microbial food webs may have altered N mineralization processes. In contrast, in the HD treatment, all the variables measured were not significantly different from those of WD treatment. Intensive browsing by deer may have cancelled out the effects of the decrease in aboveground litter input on the soil decomposer systems through other pathways, such as a transitory increase in belowground litter input caused by induced changes in allocation patterns of bamboo. No changes in total N mineralization potential, leaf N, and composition of understory vegetation in both enclosures indicated that deer introduction did not facilitate nor retard N cycling regardless of deer density. This study showed that sika deer browsing can affect soil decomposer systems at an early stage of invasion even at low density, which contrasts with previous studies on the subject. Linking our findings of early-stage effects of deer on soil decomposer systems to longer-term dynamics of understory vegetation and tree regeneration will be needed to evaluate the adequacy of deer management practices with respect to the sustainability of soil nutrient supplies.

Fern–spore‐feeder interaction in temperate forests in Japan: Sporing phenology and spore‐feeding insect community

Angiosperms are widely appreciated to have flowering schedules, but far less attention has been paid to the timing of spore production by ferns. Although a range of abiotic factors are likely responsible for the timing of fern sporing, spore predation by specialist spore-feeding insects may also exert selective forces on timing. As a step toward understanding ecological factors that affect the evolution of fern sporing phenology, we tracked annual sporing patterns and examined associations with spore-feeding insects in 38 ferns species in two Japanese temperate forests. Most sporing occurred during June through August, the period of highest temperature and precipitation at the study sites, but some species produced spores during a limited period in spring or very late autumn. Over 70% of all species examined were attacked by spore-feeders, which consisted of seven polyphagous and five oligophagous species. Spore feeders occurred predominantly during June through September, and stathmopodid moth larvae consumed up to 70% of the mature sporangia. Thus, although the warm and humid conditions in the summer is likely favored for prothallial growth and fertilization, spring or late-autumn sporing in some species may have evolved as an adaptation to escape spore predation by spore feeders.

A neural network approach to simple prediction of soil nitrification potential: A case study in Japanese temperate forests

The nitrogen status of forest ecosystems can be represented by the net nitrification potential (NNP) of the forest soils. Prediction of NNP using a small number of soil properties is a practically useful tool for forest management planning. Artificial neural networks (ANN) have recently become popular tools in forest modeling because they eliminate certain difficulties in handling forest data, such as the nonlinear relationships and non-normality. This study aimed to develop an ANN model to predict NNP that required a few soil properties as possible for input data. The ANN model was fitted to field data using the ridge-stabilized Gauss–Newton method, with a subset of methods to prevent excessively high weights that are likely to cause over-fitting. We collected surface mineral soil samples from 56 locations in temperate forest ecosystems of central Japan. We measured NNPs on a per area basis (Mg N km −2) using aerobic laboratory incubation at 30 °C for 4 weeks. The ANN-based model using data on only two soil properties (the C:N ratio and the maximum water-holding capacity) provided the best prediction of NNP. The ANN-based model’s success results from its incorporation of (1) the nonlinear relationship between the C:N ratio and NNP and (2) the hierarchical control of NNP, which is governed primarily by the C:N ratio and secondarily by soil moisture conditions. The simplicity of the model greatly enhances its practical value in forest management planning.

Geographical variation in climatic cues for mast seeding of Fagus crenata

AbstractGeographical variation in climatic cues for masting of Fagus crenata Blume, which is the most dominant tree species in Japanese temperate forests, was investigated in the northern part of Japan, i.e., the Tohoku district of Honshu Island and the Oshima Peninsula of Hokkaido Island. The data obtained after an 18‐year assessment (1989–2006) of 163 stands, covering an area of ca. 200 × 500 km2 area, were used in this study. In all stands, mast seeding occurred three times (1995, 2000 and 2005) during the study period and the coefficient of annual variation (CV) in seedfall density was 0.94. Based on cluster analysis, the stands were classified into each of the seven groups, in which the seedfall density was temporally synchronized among the stands and showed higher values of CV (1.04–1.79). These groups were distributed spatially exclusively at the scale of 80–200 km. By selecting the tree model based on AIC values, lower temperature in spring, higher temperature in summer and seedfall density in a year were proved to have a decisive influence on the seedfall density in the subsequent year. The effects of the first two climatic cues overwhelm that of the seedfall density. Lower temperature in spring served as a cue mostly for the population in the Oshima Peninsula, while higher temperature in summer served as a cue for the populations in the Tohoku district. If this suggests a genetic variation in relation to cues, climatic changes (e.g., global warming) will have different impacts on seed production of different F. crenata populations. However, it remains to be tested in future studies whether multiple climatic cues simply reflect regionally variable climatic conditions or not.

Effects of deer and mice on seedling survival in a temperate mixed forest of Japan

To detect the magnitude of indirect positive effects of deer and mice on seedling survival of some woody species in a Japanese temperate forest, we analyzed the data from an earlier field experiment using a hierarchical Bayesian approach. The forest studied was inhabited by sika deer ( Cervus nippon) and mice ( Apodemus spp.), and the floor was covered with dwarf bamboo, Sasa nipponica, which negatively affected tree seedlings and was in turn negatively affected by deer and mice. The field experiment was designed as the combination of exclusion or removal of these factors: deer, mice and dwarf bamboo. A hierarchical Bayesian model was constructed and the parameters were estimated by the Markov chain Monte Carlo method. The model successfully showed the indirect positive effects of deer and mice, which improved the survival rate of five cohorts of the seedlings of three tree species by ameliorating the direct negative effect of dwarf bamboo. The cohorts studied were formed by the seedlings of Abies homolepis that emerged in 1997 and 2002, those of Fraxinus lanuginosa f. serrata that emerged in 1998 and 2002, and those of Fagus crenata that emerged in 1999. The positive indirect effect was especially large in F. crenata, which is known to be severely affected by dwarf bamboo. The total effect of deer was shown to be positive for all cohorts except the A. homolepis cohort that emerged in 1997, at which time the dwarf bamboo had not yet fully recovered from the browsing pressure of deer. The total effect of mice was shown to be positive for all of the cohorts. We conclude that these positive effects were due to the large negative effect of dwarf bamboo on the seedlings.

Methane uptake and nitrous oxide emission in Japanese forest soils and their relationship to soil and vegetation types

To determine the means and variations in CH4 uptake and N2O emission in the dominant soil and vegetation types to enable estimation of annual gases fluxes in the forest land of Japan, we measured monthly fluxes of both gases using a closed-chamber technique at 26 sites throughout Japan over 2 years. No clear seasonal changes in CH4 uptake rates were observed at most sites. N2O emission was mostly low throughout the year, but was higher in summer at most sites. The annual mean rates of CH4 uptake and N2O emission (all sites combined) were 66 (2.9–175) µg CH4-C m−2 h−1 and 1.88 (0.17–12.5) µg N2O-N m−2 h−1, respectively. Annual changes in these fluxes over the 2 years were small. Significant differences in CH4 uptake were found among soil types (P < 0.05). The mean CH4 uptake rates (µg CH4-C m−2 h−1) were as follows: Black soil (95 ± 39, mean ± standard deviation [SD]) > Brown forest soil (60 ± 27) ≥ other soils (20 ± 24). N2O emission rates differed significantly among vegetation types (P < 0.05). The mean N2O emission rates (µg N2O-N m−2 h−1) were as follows: Japanese cedar (4.0 ± 2.3) ≥ Japanese cypress (2.6 ± 3.4) > hardwoods (0.8 ± 2.2) = other conifers (0.7 ± 1.4). The CH4 uptake rates in Japanese temperate forests were relatively higher than those in Europe and the USA (11–43 µg CH4-C m−2 h−1), and the N2O emission rates in Japan were lower than those reported for temperate forests (0.23–252 µg N2O-N m−2 h−1). Using land area data of vegetation cover and soil distribution, the amount of annual CH4 uptake and N2O emission in the Japanese forest land was estimated to be 124 Gg CH4-C year−1 with 39% uncertainty and 3.3 Gg N2O-N year−1 with 76% uncertainty, respectively.

Beta‐diversity of lepidopteran larval communities in a Japanese temperate forest: effects of phenology and tree species

AbstractThe specialization of herbivores among tree species is poorly understood despite its fundamental importance as a factor regulating diversity. To examine the effect of tree species on larval community structure, the larval communities in 10 temperate deciduous tree species that differed in leaf emergence pattern (flush‐ vs. intermediate‐type) were seasonally surveyed. The newly developed soft, nitrogen‐rich leaves of all species became tough and nitrogen‐poor as the season progressed. Following the changes in leaf quality, two distinct seasonal lepidopteran larval communities emerged, with a marked turnover in early July. The beta diversity, or dissimilarity, of species composition in the larval communities among tree species was higher in summer than in spring. These results imply that the lepidopteran larval communities as a whole were supported by alpha diversity in spring and by beta diversity in summer, demonstrating that the plant diversity of this forest could support a caterpillar community. We examined the importance of spatio‐temporal variations in leaf quality within and among tree species in promoting herbivore diversity, although other factors, such as tree species phylogeny and predators, may also have a large effect on lepidopteran larval communities.

Microsatellite loci for a sparsely distributed species, Kalopanax pictus (Araliaceae) in Japanese temperate forests

AbstractWe identified seven polymorphic microsatellite loci that can be used to evaluate distances of pollen movement and seed dispersal in a sparsely distributed tree species, Kalopanax pictus (Araliaceae), in Japanese temperate forests. The leaves of K. pictus are damaged by a fungal disease, Mycosphaerella acanthopanacis, and the intensity and frequency of the infections are positively correlated with adult tree density. In order to infer the optimal density of K. pictus and the processes of regeneration in the presence of the fungal disease, we developed microsatellite markers. The numbers of alleles per locus ranged from seven to 17 with an average of 10.6. Expected heterozygosity ranged from 0.63 to 0.94 with an average of 0.79. Total exclusion probabilities from the seven loci for the first and second parents of seedlings were 0.9880 and 0.9999, respectively. Our results indicate that these loci will be useful for the analysis of gene flow.

Species Diversity of Japanese Clusiidae (Diptera: Acalyptrata) with description of 12 new species

The Japanese Clusiidae are revised and 23 species, including 12 species new to science, are recognized and keyed. Clusiodes angulosus n. sp., Clusiodes discostylus n. sp., Clusiodes tobi n. sp., Clusiodes usikumuri n. sp., Craspedochaeta varicolor n. sp., Heteromeringia crenulata n. sp., Heteromeringia quadrispinosa n. sp., Heteromeringia sexramifera n. sp., Heteromeringia yamata n. sp., Phylloclusia quadrivittata n. sp., Sobarocephala uncinata n. sp., and Tetrameringia borealis n. sp. were described as new. Distribution records were compiled and mapped. Transitional climatic zone between the warm and cool temperate zones is possibly suggested as one of the most richest temperate area in terms of Japanese clusiid species richness. Hendelia beckeri Czerny 1903, Paraclusia japonica Sasakawa 1957, and Clusiodes plumosus Sasakawa 1964 are broadly distributed over all the Japanese temperate forests, but these are not always most abundant species. The clusiid assemblage was heterogeneous in the species composition among various forest types. The femalebiased sample caught by Malaise traps and distinction of clusiid species composition between temperate and subtropical zones are also pointed out.

Analytical estimation of the vertical distribution of CO 2 production within soil: application to a Japanese temperate forest

We present methods, based on an analytical solution to a diffusion equation, for estimating the vertical distribution of the rate of CO 2 production within soil. The first method assumes an a priori equation that represents the profile of CO 2 production. The second method divides the soil into four layers, from the ground surface to a depth of 80 cm; within each layer, constant CO 2 production is assumed. These methods were applied to a secondary deciduous temperate forest in Japan. Soil respiration and CO 2 concentrations within the soil pores were measured in the forest from March to December of 1998. The value of Q 10, the factor by which metabolic processes increase for each 10 °C increase in temperature, was estimated to be 2.55, using the soil temperature at a depth of 10 cm. The annual soil respiration was estimated to be 642 ± 91 g C m −2 y −1. The CO 2 concentration within soil pores increased with soil depth in every season, and showed temperature dependency at all depths, which was similar to the relationship between soil respiration and soil temperature. By applying the proposed methods, the profiles of the actual CO 2 concentrations within soil pores were well reproduced. Within soil, the amplitude of the seasonal variation in the CO 2 production rate was larger in the shallow soil layers than in the deep layers. The CO 2 production rate in the shallow soil layers was highly correlated with soil temperature, and its response to soil temperature was more sensitive than that estimated from the CO 2 efflux from the soil surface. It was found that the temperature sensitivity of the CO 2 production rate differed between the shallow and deep soil layers; this would affect the estimated value of Q 10. Adding to the necessity of distinguishing heterotrophic and autotrophic respiration, it is suggested that the way in which they are distributed vertically within soil is critical for predicting soil respiration, and should be included in the parameterization of soil respiration.

Influence of micro‐landforms on forest structure, tree death and recruitment in a Japanese temperate mixed forest

The micro‐landform unit system offers an effective way of analyzing vegetation–geomorphology relationships at a 10‐m scale in areas such as the hilly regions of Japan. We analyzed relationships between micro‐landforms and tree population parameters over a 9‐year interval to elucidate the influence of geomorphic processes on vegetation dynamics. A 2.16‐ha permanent plot was established in a temperate mixed forest. Each 5 m × 5 m quadrat within this plot was classified according to six types of micro‐landform units: (i) crest slope (CS); (ii) upper sideslope (US); (iii) head hollow (HH); (iv) lower sideslope (LS); (v) foot slope (FS); and (vi) river bed (RB). All living trees larger than 10 cm in diameter at breast height (d.b.h.) were identified, mapped and marked in 1989 and resurveyed in 1998. Almost all of the 23 common tree species persisted in their own core habitats (i.e. the micro‐landforms) between the two surveys. The species distribution in both surveys showed that the six micro‐landforms could be combined into two larger groups: upper and lower hillslope areas. The upper hillslope area had higher tree densities and larger basal areas than the lower hillslope area. It is possible that these differences result from the longer lifespans of trees on the upper hillslope area rather than from differences in mortality and recruitment rates. In addition, the different ways in which trees die in the different micro‐landform units may affect the regeneration process in hilly regions through different gap formation. The effects of different geomorphic processes are reflected in the lifespans of the trees and may result in different forest structure and dynamics among micro‐landform units.

The influence of leaf thickness on the CO2 transfer conductance and leaf stable carbon isotope ratio for some evergreen tree species in Japanese warm‐temperate forests

1. The influence of leaf thickness on internal conductance for CO2 transfer from substomatal cavity to chloroplast stroma (gi) and carbon isotope ratio (δ13C) of leaf dry matter was investigated for some evergreen tree species from Japanese temperate forests. gi was estimated based on the combined measurements of gas exchange and concurrent carbon isotope discrimination. 2. Leaves with thicker mesophyll tended to have larger leaf dry mass per area (LMA), larger surface area of mesophyll cells exposed to intercellular air spaces per unit leaf area (Smes) and smaller volume ratio of intercellular spaces to the whole mesophyll (mesophyll porosity). 3. g i of these leaves was correlated positively to Smes but negatively to mesophyll porosity. The variation in gi among these species would be therefore primarily determined by variation of the conductance in liquid phase rather than that in gas phase. 4.δ13C was positively correlated to mesophyll thickness and leaf nitrogen content on an area basis. However, gi values did not correlate to δ13C. These results suggest that difference in δ13C among the species was not caused by the variation in gi, but mainly by the difference in long‐term photosynthetic capacity. 5. Comparison of our results with those of previous studies showed that the correlation between leaf thickness and gi differed depending on leaf functional types (evergreen, deciduous or annual). Differences in leaf properties among these functional types were discussed.

Effects of potential PAR on shoot extension in juveniles of the main tree species in a Japanese temperate forest

We studied the relationship between potential photosynthetically active radiation (PAR), estimated from hemispherical photographs, and shoot extension rates of juveniles of 12 seral tree species. We distinguished between direct light site factor (DIR), diffuse light site factor (DIF), and gap light index (GLI). We used a log‐linear model to relate growth to DIR, DIF and GLI. Potential PAR explained shoot growth rates significantly in 33 cases out of 36 (12 species × 3 PAR). DIF explained the shoot extension rates better than DIR and GLI for 10 of the 12 species. The mean values of maximum shoot extension rates of the tolerant, the intermediate and the intolerant species were 52.4 cm year–1, 64.3 cm year–1 and 87.7 cm year–1, respectively. The maximum shoot extension rates of the tolerant and the intolerant species were recorded in about 50% DIF and more than 70% DIF, respectively. The minimum light level for seedling establishment of the intermediate and intolerant species was more than 20% DIF. We explained distribution characteristics and shoot extension of the species in relation to light in terms of shade tolerance. Predictions based on light‐growth curves and maximum growth curves were similar to field observations made elsewhere, suggesting that these models may be useful to predict extension growth of juvenile trees in mixed species stands.

The seed bank dynamics ofCornus controversaand their rote in regeneration

AbstractSeed-bank dynamics ofC. controversa, a common tree in Japanese temperate forests, were investigated at Ogawa Forest Reserve by direct measurement of seed input, soil seed density, and seedling output (germination of soil seeds), together with two field experiments on postdispersal seed mortality. Soil seed density varied from 4 to 233 m−2in the site near conspecific adults (&lt;5 m horizontally from crown edge), and 0 to 18 m−2in far sites (≥5 m) during the 1988–92 period. Seed input occurred only in 1988 and 1990: 190–740 m−2at the sites near conspecific adults, and 4–20 m−2at the far sites. Seedling output was observed every year and accounted for 0–15% of the loss from the seed bank, occasionally 30–60%. Seeds buried at 5-cm depth suffered moderate mortality (c.0.2 year−1) by fungal pathogens. In contrast, seeds experimentally placed on the ground suffered higher mortality (0.5–1 year−1) through predation by ground mammals, probably wood mice. In the experiment, seeds whose mesocarp was removed survived much better. On the other hand, distance itself did not appear to affect post-dispersal mortality of seeds. Seeds in canopy gaps also tended to suffer higher mortality. Current spatial pattern and mode of seed dispersal should decrease the potential ability of the seed bank of this species to colonize safe sites. Rare and unpredictable events might increase the contribution of the seed-bank strategy to regeneration in this forest.

Density-dependent demography in a Japanese temperate broad-leaved forest

A method of detecting the density-dependent dynamics of a size-structured population is developed. The method is applied to a Japanese broad-leaved forest and the density-dependent and-independent projection matrix models are constructed based on the data of the forest. Then, the difference between the density-independent and density-dependent dynamics is compared in terms of several statistical quantities obtained from the matrices. Three kinds of sensitivity matrices are proposed for the density-dependent matrix model. At earlier stages, the sensitivity when the population density is low are higher than at the equilibrium. On the other hand, the inverse result is obtained at later stages. Moreover, the responses of the forest is analyzed to a decrease in survival rate and to an increase in the probability of gap formation. The decrease in survival rate leads to an extreme decrease in the density of the forest. However, the decrease in recruitment rate gives little effect on it because the effect of density-dependence in recruitment of new individuals is strong. The forest has the optimal rate of gap formation such that leads to the maximum population density.

Phenological Comparison of the Onset of Vessel Formation Between Ring-Porous and Diffuse-Porous Deciduous Trees in a Japanese Temperate Forest

Initiation of vessel formation and vessel maturation indicated by secondary wall deposition have been compared in eleven deciduous broadleaved tree species. In ring-porous species the first vessel element formation in the current growth ring was initiated two to six weeks prior to the onset of leaf expansion, and secondary wall deposition on the vessel elements was completed from one week before to three weeks after leaf expansion. In diffuse-porous species, the first vessel element formation was initiated two to seven weeks after the onset of leaf expansion, and secondary wall deposition was completed four to nine weeks after leaf expansion. These results suggest that early maturation of the first vessel elements in the ring-porous species will serve for water conduction in early spring. On the contrary, the late maturation of the first vessel elements in the diffuse-porous species indicates that no new functional vessels exist at the time of the leaf expansion.