Tree Competition and Species Coexistence in a Sub-boreal Forest, Northern Japan

The growth and mortality patterns and the mode of competitionof six tree species forming a sub-boreal climax forest in Hokkaido,northern Japan, were investigated based on the diffusion modelat the level of the individual tree 2 m height in a 2·3-hastudy site. Picea jezoensis, Picea glehnii, Betula ermanii andAbies sachalinensis were dominant species, occupying approx.94% of the total basal area. Sorbus commixta and Acer ukurunduensewere subordinate species occupying approx. 6% of the total basalarea. A model for individual growth was developed, consideringboth intra- and inter-specific competition and the degree ofcompetitive asymmetry. Asymmetry was found in intraspecificcompetition of Sorbus commixta and Acer ukurunduense. Piceajezoensis, Betula ermanii and Abies sachalinensis showed symmetricintraspecific competition. There was little interspecific competitionamongst Picea jezoensis, Picea glehnii and Betula ermanii. Abiessachalinensis competed symmetrically with Picea jezoensis (onlyvery weakly, P < 0·1) and Betula ermanii (P < 0·01).Picea glehnii gave no indication of inter- or intra-specificcompetition. The growth of the four dominant species was neveraffected by the two subordinate species; the growth of the twosubordinate species was governed by the abundances of the fourdominant species, the sum of which almost amounted to standcrowdedness (i.e. symmetric competitive effect and one-sidedcompetitive direction). On the scale of 2·3 ha of thesub-boreal forest, symmetric competition prevailed over one-sidedor asymmetric competition although statistical evidence forany competitive effects was rather weak. This was probably dueto the relatively low tree density and stand crowdedness ofthis climax forest. Little competition between the dominantspecies suggested by relatively low proportions of r²-valuesattributable to competitive effects indicates weak organizationamongst the component species (i.e. species were more or lessindependent of each other) at the level of the individual tree 2 m height on the 2·3-ha scale.Copyright 1995, 1999Academic Press Climax forest, diffusion model, individual growth, one-sided competition, size structure, symmetric competition     

Differential photosynthetic characteristics between seedlings and saplings of Abies sachalinensis and Picea glehnii, in the field

Abies sachalinensis and Picea glehnii are co-dominant tree species and major components of the forests of Hokkaido, Japan. Recent work suggests that a reversal in potential competitive superiority at different developmental stages could be important to explain their coexistence. Such shifts in competitive advantage can be mechanistically understood by studying the corresponding physiological differences between distinct life stages. Accordingly, our objective was to investigate in the field the photosynthesis of shade-growing juveniles of these species from two different size-classes, seedlings and saplings. Our results show that seedlings of both species had higher concentrations of photoprotective xanthophylls than saplings, especially in spring, and suggest that seedlings have a lower threshold of stress tolerance than saplings. Photosynthetic capacity per needle area and lateral shoot extension rate decreased from the seedling to the sapling stage in A. sachalinensis, while in P. glehnii, both increased from the seedling to the sapling stage. Abies sachalinensis had higher photosynthetic rates at the seedling stage but lower rates at the sapling stage than P. glehnii. Nevertheless, A. sachalinensis had a higher lateral shoot extension rate than P. glehnii at both stages. Our physiological results support previous ecological observations that A. sachalinensis is a superior competitor to P. glehnii in the understory, and show that its competitive advantage is higher at the seedling stage than at the sapling stage.     

Recruitment Processes and Species Coexistence in a Sub-boreal Forest in Northern Japan

We investigated the recruitment of saplings (across the 2 m-heightthreshold) of six species,Picea jezoensis, Abies sachalinensis,Betula ermanii, Picea glehnii, Acer ukurunduense andSorbus commixta,in a sub-boreal forest, northern Japan. Data were collectedin a 2.48-ha plot over six growing seasons (1989–1994).We used path analysis to analyse the relationships between therecruitment rates of saplings and the stand structural attributessuch as mother tree abundance, stand crowdedness, stand stratification,Sasabamboo density on the forest floor, and fallen log abundance.The combination of stand structural attributes affecting recruitmentrates of the six sub-boreal forest tree species differed markedlyamong the species and corresponded to species composition. Itis suggested that the size-structure dynamics of adult treesof the sub-boreal forest are regulated largely by differentregeneration processes among the species and only slightly byinterspecific competition between adult trees because interspecificcompetition between adult trees was not evident. The dynamicsof species coexistence of the sub-boreal forest should be describedas a process combining the diversity of recruitment processesof saplings of the component species and the diversity of interspecificcompetition between adult trees. We propose the boundary conditionhypothesis for species coexistence in the sub-boreal forest,that the persistence of each component species is ascribed largelyto the different recruitment processes of saplings (boundaryconditions for adult tree growth dynamics) and only a littleto interspecific adult tree competition. Climax forest; safe site; regeneration niche; mode of competition; species diversity     

Nuclear and chloroplast microsatellite analysis of Abies sachalinensis regeneration on fallen logs in a subboreal forest in Hokkaido, Japan

Fallen logs are the main regeneration sites for Abies sachalinensis (Sachalin fir) in subboreal forests in Japan. We surveyed the spatial genetic structure of different demographic stages in a 4.29-ha natural population of A. sachalinensis . Genetic structure was significant at short distances throughout all stages in this wind-dispersed conifer. To evaluate the effects of fallen-log-dependent recruitment on demography and spatial genetic structure, we conducted parentage analysis of offspring with highly polymorphic nuclear simple sequence repeat and chloroplast simple sequence repeat markers, and developed a new hierarchical Bayesian model to estimate the effects of mother trees and fallen logs on seed dispersal and offspring recruitment. Combined application of nuclear and chloroplast simple sequence repeat markers allowed us to unambiguously identify mother trees of most offspring (> 90%). Female reproductive success was extremely skewed; a few adults produced most of the offspring on fallen logs. Limited distance of effective dispersal and recruitment was seen in the parentage analysis and modelling estimation. These recruitment characters of A. sachalinensis , with a fallen-log-dependent recruitment process, may result in significant genetic structure in early demographic stages.     

Regeneration process of coniferous forests in northern Hokkaido I.Abies sachalinensis forest andPicea glehnii forest

Regeneration of natural forests was studied in the Nakagawa Experiment Forest of Hokkaido University using age distribution surveys made by the clear felling method. In Plot 1 (30 m × 65 m),Abies sachalinensis dominated the canopy layer but there were also a fewBetula ermanii trees.Sasa senanensis densely covered the forest floor. Most of the canopy trees were from 122 to 195 years old. Seedlings younger than 50 years old ofA. sachalinensis were found on fallen logs and root bases. There were, however, few trees from 50 to 120 years old. The present canopy trees seemed to have regenerated after competitive pressure from old canopy andSasa disappeared 180 years ago. Plot 2 (50 m × 100 m) on serpentinite soil was dominated byPicea glehnii. Sasa kulirensis covered the floor but not as densely asS. senanensis in Plot 1. The ages ofP. glehnii ranged from 1 to 586 years old, and the age distribution ofA. sachalinensis was L-shaped. A small gap in the canopy formed about 290 years ago, and it gradually extended. Conifers regenerated continuously in the extending gap butB. ermanii did not. One hundred thirty years ago, part of Plot 2 was again destroyed andA. sachalinensis andB. ermanii regenerated. Thus, two types of regeneration were found. One regenerated both conifers andBetula after a sudden disturbance of canopy layer or death ofSasa, and the other, under an extending gap, regenerated only conifers.     

The positional distribution of cell death of ray parenchyma in a conifer, Abies sachalinensis

We monitored the distribution of death of secondary xylem cells in a conifer, Abies sachalinensis. The cell death of tracheids, which are tracheary elements, occurred successively and was related to the distance from cambium. Thus, it resembled programmed cell death. By contrast, the death of long-lived ray parenchyma cells had the following features: (1) ray parenchyma cells remained alive for several years or more; (2) in many cases, no successive cell death occurred even within a given radial cell line of a ray; and (3) the timing of cell death differed among upper and lower radial cell lines and other lines of cells within a ray. These results indicate that the death of long-lived ray parenchyma cells involves a different process from the death of tracheids. The initiation of secondary wall formation and the lignification of ray parenchyma cells in the current year's annual ring were delayed in the upper and lower radial cell lines of a ray. In addition, the density of distribution and orientation of cortical microtubules in such cells were different from those in cells in other radial lines. Ray parenchyma cells in the previous year's annual ring within the upper and lower radial cell lines of a ray contained many starch grains. Our results indicate that positional information is an important factor in the control of the pattern of differentiation and, thus, of the functions of ray parenchyma cells that are derived from the same cambial ray cells.     

Micro-distribution of Soil Inhabiting Tardigrades (Tardigrada) in a Sub-alpine Coniferous Forest of Japan

Micro-distribution of soil inhabiting tardigrades was studied in a sub-alpine coniferous forest (alt. 1,840 m a. s. l.) on the eastern slope of Mt. Yatsugatake, Central Japan. Eight cylindrical soil samples were taken from the forest floor. Each sample was divided into 10 slice samples of 1 cm thick. Tardigrades were extracted from samples by Baermann funnels, identified to specific level and counted. The average number of tardigrades in the study site is 74,058/m². High densities sometimes occurred at depths greater than 5 cm. Consequently for investigating tardigrade populations, 5cm depth core sampling is insufficient in this type of habitat. Composition of the main groups of species reveals that shallow layers (1, 2 or 3 cm depth) are frequently dominated by the Diphascon-group. Macrobiotus-group species generally occurred in higher abundance in the deeper layers. It is very interesting that there are some different patterns of soil micro-distribution in tardigrade species.     

Stand development and regeneration during a 33-year period in a seral Picea glehnii forest, northern Japan

Stand development and regeneration were studied during a 33-year period (1965-1998) in a 1-ha plot in a seral Picea glehnii forest in northern Japan. P. glehnii was mono-dominant in the upper canopy layer, but its understory trees were rarely found in 1965. Other species were scarcely observed in 1965. Many recruited saplings of Abies sachalinensis which had grown to > 5 cm diameter at breast height (DBH) by 1998 had become dominant in the understory layer. Mortality of P. glehnii canopy trees was low. Therefore, the stand basal area increased during the census period due to the growth of surviving canopy trees. Stand development brought about intense competition among trees by increasing local crowding for each tree, and promoted dominance of larger trees and suppression of smaller trees. Although growth rates of understory trees of the two conifers decreased with the increase in local crowding, the growth rate of A. sachalinensis was consistently higher than that of P. glehnii at all extents of local crowding. The recruitment rate (growing to 5 cm DBH) of the two conifers was less affected by local crowding. However, the number of recruits of P. glehnii was only about a quarter of that of A. sachalinensis during the census period because the regeneration of P. glehnii was largely restricted to fallen logs and within 1 m of the base of any live tree > 20 cm DBH. Therefore, our long-term study suggests that A. sachalinensis will dominate over P. glehnii in the seral forest because of higher recruitment and growth rates of the former than the latter in the understory.An erratum to this article can be found at     

Sclerochronological study of the gigantic inoceramids Sphenoceramus schmidti and S. sachalinensis from Hokkaido,northern Japan

Here, we present the first sclerochronological investigation of shells of the gigantic inoceramids Sphenoceramus schmidti and S. sachalinensis from the middle Campanian cold seep carbonate‐bearing strata of the Yezo Basin in Hokkaido (northern Japan). Stable carbon (δ¹³C) and oxygen (δ¹⁸O) isotope values were measured in the aragonitic and calcitic shell layers of both species and compared to those of other co‐occurring benthic (mainly bivalves and gastropods) and demersal molluscs (ammonites). Sedimentological and stable isotope data suggest that these bivalves lived near cold seeps and were exposed to high H₂S level in the seawater. The inoceramid shells exhibited higher δ¹³C and lower δ¹⁸O values than the coeval non‐cold seep molluscs. We ascribed the anomalous isotopic pattern to a combination of vital and environmental effects determined by the hosting of chemosymbionts and the exposure to warm interstitial waters. Inoceramid δ¹³C minima coincided with growth lines and likely reflect changes in nutrient supply by the chemosymbionts. Absolute temperatures estimated from δ¹⁸O values of Sphenoceramus schmidti and S. sachalinensis were, on average, ca. 4–5°C warmer than those reconstructed for the non‐seepage environment (19.3 ± 0.7°C). Short‐term δ¹⁸O fluctuations of the inoceramid material indicate local temperature ranges of up to 5.2°C, that is four times larger than those reconstructed from the benthic and demersal fauna (1.3°C). In general, our data suggest that the stable carbon and oxygen isotope values of the studied Sphenoceramus spp. were strongly affected by short‐term fluctuations in seepage activity and do not reflect seasonal fluctuations.     

Difference in microhabitat-related regeneration patterns between two subalpine conifers, Tsuga diversifolia and Abies mariesii, on Mount Hayachine, northern Honshu, Japan

Seedling and tree-establishment microhabitats of Tsuga diversifolia and Abies mariesii were examined on the herb- and dwarf bamboo-dominated forest floor on Mount Hayachine, a mountain under intermediate snow conditions in northern Honshu, Japan. The four microsite types were fallen logs, buttresses, rocks and ground. The ground substratum was further divided into four subtypes by dominant undergrowth species: Lycopodium, Pteridophyllum, Carex and dwarf bamboo. The establishment of T. diversifolia seedlings on the ground was scarce, and depended mostly on non-ground microsites (i.e. fallen logs, buttresses and rocks). The seedling establishment of A. mariesii was not dependent on specific substrata, although on the ground, establishment sites were limited to the Lycopodium subtype situated on convex sites. Among the microhabitats for seedling establishment, larger trees of A. mariesii rarely occurred on higher portions of the non-ground microsites. In contrast, T. diversifolia could grow up to the height of canopy-layer trees in such microsites. Thus, non-ground microsites seem to be unsuitable for tree establishment in A. mariesii, and are probably useful microhabitats for regenerating T. diversifolia to avoid competition with A. mariesii. We also compared seedling-establishment microhabitats for the two conifers between Mount Hayachine and two other mountain regions under different undergrowth conditions (moss-dominated and dense dwarf bamboo-dominated). Our findings suggested that seedling recruitment in non-ground microsites was primarily determined by undergrowth conditions; T. diversifolia preferred such microsites where the moss-covered area was low, and A. mariesii preferred where dwarf bamboo-covered area was high.     

Phylogeography of a northeast Asian spruce, Picea jezoensis, inferred from genetic variation observed in organelle DNA markers

Range-wide genetic variation of the widespread cold-temperate spruce Picea jezoensis was studied throughout northeast Asia using maternally inherited mitochondrial DNA and paternally inherited chloroplast DNA markers. This study assessed 33 natural populations including three varieties of the species in Japan, Russia, China, and South Korea. We depicted sharp suture zones in straits around Japan in the geographical distribution pattern of mitochondrial haplotypes (GST=0.901; NST=0.934). In contrast, we detected possible extensive pollen flow without seed flow across the straits around Japan during the past population history in the distribution pattern of chloroplast haplotypes (GST=0.233; NST=0.333). The analysis of isolation by distance of the species implied that by acting as a barrier for the movement of seeds and pollen, the sharp suture zones contributed considerably to the level of genetic differentiation between populations. Constructed networks of mitochondrial haplotypes allowed inference of the phylogeographical history of the species. We deduced that the disjunction with Kamchatka populations reflects range expansion and contraction to the north of the current distribution. Within Japan, we detected phylogeographically different types of P. jezoensis between Hokkaido and Honshu islands; P. jezoensis in Honshu Island may have colonized this region from the Asian continent via the Korean peninsula and the species in Hokkaido Island is likely to have spread from the Asian continent via Sakhalin through land bridges. Japanese endemism of mitochondrial haplotypes in Hokkaido and Honshu islands might have been promoted by separation of these islands from each other and from the Asian continent by the straits during the late Quaternary.     

Forest biomass and volume estimation using airborne LiDAR in a cool-temperate forest of northern Hokkaido,Japan

Trees are recognized as a carbon reservoir, and precise and convenient methods for forest biomass estimation are required for adequate carbon management. Airborne light detection and ranging (LiDAR) is considered to be one of the solutions for large-scale forest biomass evaluation. To clarify the relationship between mean canopy height determined by airborne LiDAR and forest timber volume and biomass of cool-temperate forests in northern Hokkaido, Japan, we conducted LiDAR observations covering the total area of the Teshio Experimental Forest (225 km²) of Hokkaido University and compared the results with ground surveys and previous studies. Timber volume and aboveground tree carbon content of the studied forest stands ranged from 101.43 to 480.40 m³ ha^–1 and from 30.78 to 180.54 MgC ha^–1, respectively. The LiDAR mean canopy height explained the variation among stands well (volume: r² = 0.80, RMSE = 55.04 m³ ha^–1; aboveground tree carbon content: r² = 0.78, RMSE = 19.10 MgC ha^–1) when one simple linear regression equation was used for all types (hardwood, coniferous, and mixed) of forest stands. The determination of a regression equation for each forest type did not improve the prediction power for hardwood (volume: r² = 0.84, RMSE = 62.66 m³ ha^–1; aboveground tree carbon content: r² = 0.76, RMSE = 27.05 MgC ha^–1) or coniferous forests (volume: r² = 0.75, RMSE = 51.07 m³ ha^–1; aboveground tree carbon content: r² = 0.58, RMSE = 19.00 MgC ha^–1). Thus, the combined regression equation that includes three forest types appears to be adequate for practical application to large-scale forest biomass estimation.     

Monilinia jezoensis sp. nov. in the Sclerotiniaceae, causing leaf blight and mummy fruit disease of Rhododendron kaempferi in Hokkaido, northern Japan

A new leaf blight and mummy fruit disease caused by a species of Monilinia was first found on Rhododendron kaempferi at the lakeside of Shikotsu-ko, Hokkaido, northern Japan, in 2002. Studies on morphology, life cycle, cultural characters, and gene analyses of the causal fungus enabled us to conclude that it is a new species of the genus. It is named M. jezoensis. Rhododendron is a new host genus for Monilinia fungi in Japan.     

Some observations of phenology and ecophysiology ofDaphne kamtschatica Maxim.var.jezoensis (Maxim.) Ohwi, a shade deciduous shrub, in the forest of northern Japan

The phenology and leaf traits ofDaphne kamtschatica Maxim. var.jezoensis (Maxim.) Ohwi, the only summer deciduous shrub (20–40 cm) in the temperate forest of northern Japan, are examined. This plant carries through the winter mature leaves and well formed flower buds. It flowers in early spring during snowmelt and begins photosynthesis under relatively high irradiance under an open forest canopy. Our results show that there is significant carbon gain during the period when new leaves and fruit maturation also take place. Beginning in June, as the forest canopy closes, leaves onDaphne shoots senesce acropetally and the plants become completely bare in mid-July. After a period of 20-day dormancy, the shoots begin to resprout. Leaves become mature in early October and remain on the stem over winter. Leaf traits and photosynthesis measurements suggest as follows. 1) By becoming summer deciduous,D. kamtschatica avoids the cost of maintaining leaves inefficient under deep shade. 2) The onset and breaking of the summer dormancy is triggered by photoperiod since plants at the forest edge also become dormant even when light remained relatively high. However, the decreased duration of dormancy with higher light levels suggests that there is a tendency towards shorter dormancy where summer shade is absent and this could eventually lead to an evergreen habit such as that found in the alpine speciesDaphne miyabeana.     

Decomposition and nitrogen release from the foliage litter of fir (Abies sachalinensis) and oak (Quercus crispula) under different forest canopies in Hokkaido, Japan

When two tree species co-occur, decomposition and nitrogen (N) release from the foliage litter depend on two factors: the forest floor conditions under each canopy type and the species composition of the litter. We conducted an experiment using fir and oak to answer several questions regarding decomposition beneath canopies of the two species and the effects of litter species composition on decomposition. We compared the rates of decomposition and N release from three different litters (fir needle, oak leaf, and a mixture of the two) in 1-mm-mesh litterbags on the forest floor under three different canopies (a 40-year-old fir plantation, large oak trees, and mixed fir and oak trees) in Hokkaido, Japan, over a 2-year period. Beneath each of these canopy types, the litter decomposition rate and percentage of N remaining in the litterbags containing a mixture of fir and oak litter were not significantly different from the expected values calculated for litterbags containing litter from a single tree species. Oak leaf litter decomposed significantly faster than fir needle litter beneath each canopy type. The litter decomposition rate was significantly higher beneath the fir canopy than under the oak canopy, and was intermediate under the mixed canopy of fir and oak. No net N release, that is, a decrease in the total N compared to the original amount, was detected from fir litter under each canopy type or from oak leaf litter beneath the oak canopy. N increased over the original amount in the fir litter beneath the oak canopy and the mixed canopy of fir and oak, but N was released from the oak litter under the fir canopy and the mixed canopy of fir and oak. These results suggest that oak leaf litter blown onto fir forest floor enhances nutrient cycling, and this might be a positive effect of a mixed stand of conifer and broad-leaved trees.     

Selection and microculture of single embryogenic cell clusters in japanese conifers: Picea jezoensis, Larix leptolepis and Cryptomeria japonica

Summary A microculture method for single embryogenic cell clusters was established for several Japanese conifer species, namely Picea jezoensis, Larix leptolepis and Cryptomeria japonica. Individual small, dense cell clusters were identified and picked up by a micromanipulator and cultured in 50 μl liquid medium in a 96-well culture plate. In all three species studied, a majority of the cell clusters actively proliferated within the wells. Maturation of somatic embryos was successful when the newly proliferated cell clusters were transferred to solid abscisic acid-containing medium. Thus, the small, dense cell clusters could be a useful morphological marker for cells capable of proliferation and differentiation.     

Description of Cydia piceicola,sp. nov. (Lepidoptera,Tortricidae), feeding on Picea jezoensis in Korea

The adult and the early stages of Cydia piceicola, sp. nov., are described and illustrated from Korea. Larvae of the new species feed on Picea jezoensis (Siebold et Zucc.) Carrière, The life history and larval feeding habits are briefly discussed.     

长白山落叶松与鱼鳞云杉生长-气候关系的种间差异

为阐明不同树种间树木径向生长对气候变化的响应及其时间稳定性,本研究以长白山北坡高海拔处(1600～1750 m)落叶松和鱼鳞云杉为研究对象,运用年轮年代学方法探究树木径向生长与气候的关系.结果表明: 研究区落叶松生长与当年6月最高气温呈显著正相关,与当年6月降水呈负相关;鱼鳞云杉与当年5月最高温度呈显著正相关.冗余分析进一步表明,落叶松生长主要受夏季温度的影响,鱼鳞云杉生长主要受春季温度的制约.在1959—2014年,落叶松生长-夏季温度关系相对稳定;对于鱼鳞云杉,自1986年以来其与春季温度的相关性减弱,可能由于最高温度降低导致树木生长减慢.本研究结果可以为预测气候变化情景下长白山针叶树种生长的响应趋势提供数据支持和理论参考.     

Diet of a Japanese Macaque Troop in the Coniferous Forest of Yakushima

I studied the diet of a troop of Japanese macaques in the coniferous forest of Yakushima over one year via focal animal sampling. Fiber-rich foods constituted 45% of annual feeding time, and mature leaves constituted 38% of total feeding time. Feeding time on fruits and seeds was only 13% and 4%, respectively. Flowers and fungi contributed a considerable amount of annual feeding time: 15% and 14%, respectively. Their diet changed seasonally. They fed on more fruits and seeds in response to increased availability, and when these foods were not available, they ate mature leaves. When the temperature was low, they ate more herbs, possibly to save energy by not climbing trees and staying in sunny places. The results imply two dietary characteristics of the species that might relate to adaptations in temperate regions, where fruit is available during a limited season and fiber-rich foods are the only candidate of fallback food. They are capable of digesting a large amount of fiber-rich food, but at the same time they preferentially select high-quality fruits or seeds when they are available.