Gap formation, microsite variation and the conifer seedling occurrence in a subalpine old-growth forest, central Japan

To evaluate the effects of canopy gaps and forest floor microsites (soil, fallen logs, root-mounds, buttresses and stumps) on regeneration of subalpine forests, the gap regeneration and seedling occurrence of conifers (Abies mariesii, Abies veitchii, Picea jezoensis var. hondoensis and Tsuga diversifolia) were studied in two stands of a subalpine old-growth forest, central Japan. The percentage of gap area to total surveyed area was 11.2–11.3% in the stands. Gap regeneration was not common for P. jezoensis var. hondoensis and T. diversifolia. In contrast, gap regeneration by advanced regeneration was relatively common for Abies. Seedling occurrence of P. jezoensis var. hondoensis and T. diversifolia was restricted on elevated surfaces such as stumps and root-mounds, while Abies seedlings could occur on soil as well as on elevated surfaces. Rotten stumps were the most favorable microsites for conifer seedling occurrence, which covered small area in the forest floor. Although canopy gaps were not always favorable for seedling occurrence, all conifer seedlings were larger under canopy gaps than under closed canopy. Canopy gaps and forest floor microsites clearly affected seedling occurrence and growth of conifers. This suggests that regeneration of conifers is related to the difference of growth advantage under canopy gaps and favorable microsites for seedling occurrence.     

Seed size,establishment sites and species coexistence in a Chilean rain forest

Abstract. Seedling densities on the forest floor and on elevated microsites (logs and stumps) were compared for eight woody species in a temperate rain forest in southern Chile. Degree of association with elevated microsites varied significantly between species, showed no systematic relationship with reported shade tolerance, but was significantly negatively correlated with seed mass. Large-seeded Podocarpus nubigena established preferentially on undisturbed forest floor sites, whereas seedlings of small-seeded species such as Nothofagus nitida and Laurelia philippiana were found mainly on fallen logs and stumps. The abundance of large seedlings and saplings of N. nitida on logs/stumps, and the growth forms of canopy trees, confirm that recruitment of this species occurs mainly on decaying wood. The relationship between seed size and microsite preferences may be caused by effects of seed size on (1) ability to establish in forest floor litter and (2) retention of seeds on logs. Seedling occupancy of logs and stumps varied with state of decay. Few seedlings of any species were present on logs in the early stages of decay. N. nitida established earlier than the other species, attaining maximum abundance on wood in the middle decay classes. Species richness and overall seedling abundance were highest on wood in advanced stages of decay. Seed size differences are suggested as a determinant of differential utilization of forest floor heterogeneity, and hence of plant species coexistence.     

川西亚高山暗针叶林恢复过程中岷江冷杉天然更新状况及其影响因子

在川西亚高山米亚罗林区海拔3 100~3 600 m阴坡、半阴坡, 以立地条件基本一致的箭竹和藓类林型不同恢复阶段(20~40 a生的箭竹阔叶林、50 a生的箭竹针阔混交林、160~200 a生的箭竹原始暗针叶老龄林; 20~40 a生的藓类阔叶林、50 a生的藓类针阔混交林、160~200 a生的藓类原始暗针叶老龄林)的群落为研究对象, 共设置了50个样方(20 m×20 m), 采用空间代时间的方法分析了岷江冷杉(Abies faxoniana)的天然更新状况, 并采用通径分析法对其影响因子进行分析。结果表明: 箭竹和藓类两种森林类型岷江冷杉幼苗、幼树和小树的密度偏低。对于箭竹林型不同恢复阶段, 岷江冷杉幼苗密度＜幼树密度＜小树密度; 对于藓类林型不同恢复阶段, 藓类阔叶林幼树密度大于幼苗和小树密度, 藓类针阔混交林小树密度大于幼苗和幼树密度, 而藓类原始暗针叶老龄林幼苗密度大于幼树和小树密度。藓类林型岷江冷杉天然更新状况好于箭竹林型。对箭竹林型而言, 影响岷江冷杉天然更新的关键因子为母树密度、倒木蓄积量、箭竹盖度和苔藓层厚度, 其中母树密度和倒木蓄积量对岷江冷杉天然更新起着促进作用, 箭竹盖度和苔藓层厚度对岷江冷杉天然更新起着阻碍作用; 对于藓类林型而言, 影响岷江冷杉天然更新的关键因子为灌木盖度和苔藓层厚度。灌木和苔藓有利于幼苗的发生, 但不利于幼苗向幼树、小树的过渡。     

Natural regeneration of Pinus resinosa on burned and unburned sites in Newfoundland

Abstract. Natural regeneration of Pinus resinosa (red pine) seedlings around mature trees was studied in burned and unburned stands. Growth inhibitory effects of the forest organic matter on red pine seedlings was tested by a stair-step experiment using leachate of forest soil monoliths and also by a seed germination bio-assay using forest floor substrates. To test if higher burning temperatures can remove the allelopathic effects of red pine-Kalmia organic matter, a laboratory bio-assay was conducted by germinating red pine seeds on the organic matter burned at 200, 400, 600 and 800°C. Deposition of dry needles and a thick duff layer under red pine stands affected seedling establishment. Red pine seedling establishment increased with the decreasing thickness of duff layer away from the stump of the seed-bearing trees. Wildfire helped in removing the duff layer and increased seedling establishment. A high fuel load within a 0 - 1 m radius around the tree stump caused a deep burn of the organic matter including part of the soil seed reserve. On a burned-over surface, more seedlings established in a band between 1 and 2 m around the stump than inside and outside the band. Primary root growth of red pine was severely inhibited when the seedlings were grown in unburned forest floor organic matter where Kalmia was the principal understory species. Water leachate of a Pinus resinosa-Kalmia soil monolith was inhibitory to red pine seedling growth. In greenhouse conditions, the seedlings grew well in burned-over soil from a Pinus resinosa stand. Burned organic matter from a red pine forest showed an increase in pH with a burning temperature of 600°C. Primary root growth of red pine seedlings was similarly increased with increasing temperature up to 600°C; at higher temperatures the root length of seedlings did not increase any further.     

When does dead wood turn into a substrate for spruce replacement?

Question: How many years must elapse for freshly fallen Picea abies stems to be transformed into a substrate for P. abies recruitment? Location: Natural sub‐alpine spruce forest, 1200–1300 m a.s.l., western Carpathians, Poland. Methods: Coarse woody debris (CWD) was measured on nine plots with a total area of 4.3 ha. All individuals of P. abies regeneration growing on dead wood were counted and their age was estimated. Decay rate of logs was determined using dendrochronological cross‐dating of samples from logs in different decay stages. Results: Although CWD covered only 4% of the forest floor, 43% of the saplings were growing on decaying logs and stumps. The highest abundance of P. abies recruitment occurs on logs 30–60 years after tree death, when wood is in decay stages no. 4–7 (on an 8 degree decay scale). However, much earlier colonization is possible. The first seedlings may germinate on a log during the second decade after tree death and survive for decades. Their slow growth is possibly due to the gradual progressive decomposition of wood. Conclusions: This study confirms the importance of decaying wood for P. abies recruitment. The decaying logs exhibit continuous and favourable conditions for the germination of P. abies seeds throughout their decay process. Logs, irrespective of their decay stage and age, are colonized by young seedlings. This recruitment bank is constantly renewed.     

The herb and dwarf shrubs colonization of decaying logs in subalpine forest in the Polish Tatra Mountains

This is a study of the colonization pattern of herbs and dwarf shrubs on rotten logs in subalpine spruce forests (Plagiothecio Piceetum) in the Tatra Mountains. On four study plots (total area 1.43 ha.) all dead logs were measured and the decomposition stage was estimated using the 8-degree scale. For each log the cover of all vascular species, bryophytes and lichens was determined according to the methods of classical phytosociology. Constancy and an index of coverage were calculated for all vascular species growing on logs. The total volume of logs was relatively high (93 m³ ha^–1) and constituted 22% of the volume of living trees. Logs and stumps covered 411 m² ha^–1. These values are similar to those known from natural spruce forest from Carpathians and Scandinavia. The 8 stages of decomposition were equally represented, which indicates a constant supply of dead wood to the forest floor over time. The colonization of dead wood starts with lichens, followed by bryophytes and finally herbs and tree saplings. The first vascular plant colonists of dead logs appear at decay stage nr. 3 at least 20 years after tree death. The most suitable condition for most of the herb species corresponds to decay stage nr. 6 ca. 50 years after tree death. The herb cover is distinctively dominated by Vaccinium myrtillus. Simultaneously with herb species, tree seedlings colonize the logs. Constancy and abundance of Norway spruce saplings increases with advanced decomposition. It seems that the herb cover of logs does not hinder the regeneration of spruce.     

Regeneration and coexistence of two Abies species dominating subalpine forests in central Japan

Summary The mechanism of coexistence of the dominant firs Abies veitchii and A. mariesii is described in relation to regeneration patterns for climax subalpine forests of the northern Yatsugatake Mountains, central Honshu, Japan. Two mature stand types, pure conifer stands of Abies spp., and mixed stands of Abies spp. and hardwoods (mainly the birch Betula ermanii), are distinguished. Pure stands are likely to show simultaneous decay, followed by evenaged regeneration of stand-floor seedlings (<20 cm tall), Rapidly growing A. veitchii dominates over A. mariesii in this type of regeneration, which is occasionally invaded by light-demanding Betula. In constrast, mixed stands degenerate rather slowly, followed by the regeneration of Abies from the bank of suppressed saplings (>20 cm tall), which persist only in mixed stands. The more shade-tolerant A. mariesii is supeior in this type of regeneration, while Betula does not succeed, and mixed stands change to pure stands with time. The fact that two patterns of Abies regeneration occur in a certain ratio in the forest is what enables the two Abies species to coexist. A simple dynamical system model supports this conclusion.     

Tree regeneration on rotten wood and on soil in old-growth stand

Forest regeneration on soil and on decaying wood was studied in natural mixed stand of Facus sylvatica L., Abies alba Mill. and Picea abies Karst. in Babia Góra National Park, Western Carpathians.Downed wood, divided into five decay classes covered around 6% of the forest floor. Among seedlings, Fagus and Abies codominated, while Picea was less numerous. The average seedling density on the soil with herb layer (240 ind./100 m²) was higher than on the logs, even on the strongly decayed ones (177 ind./100 m²). However, the density of Abies and Picea seedlings was higher on the rotten wood than on soil. Seedling survival of all species was better on the logs, especially in conifers. Because of the total dominance of Fagus among saplings, the presence of Abies and Picea in the next generation of canopy trees can strongly depend upon their regeneration on decaying wood.     

Seedling stage of two subalpineAbies species in distinction from sapling stage: A matter-economic analysis

A growth analytical study is made on the seedlings ofAbies mariesii Mast. andAbies veitchii Lindl. in the subalpine climaxAbies forests of the northern Yatsugatake Mountains, central Japan. Seedlings are distinguished from saplings by the absence of the fully expanded lateral branch system. The high dependence of assimilation on new needles characterizes the lives of seedlings. Leader shoots of seedlings, resembling not leader shoots but lateral branch shoots of saplings, have shoot characters adaptive for assimilation. Seedlings grow into saplings at 20 cm in height and 5 g in dry weight. The matter-economic analysis suggests the existence of a boundary growth rate below which an individual cannot maintain the needle amount requisite for its survival (called the critical growth rate) and that above which an individual can easily enter the sapling stage due to higher allocation of assimilate to roots and aged trunk stem (the capacity growth rate). Forest floor seedlings suffer, a high mortality during their initial several years and scarcely grow to enter the sapling stage, because of the scantiness of their matter production. In the regeneration patterns of subalpineAbies forests, both the seedling bank type and the sapling bank type are recognized.     

Wood-inhabiting fungi on fallen logs of Norway spruce: relations to forest management and substrate quality

A survey of the patterns of wood decaying fungi as to occurrence of sporocarps on naturally fallen logs of Norway spruce ( Picea abies ) was undertaken in two nearby forest stands with different histories of management. One stand was an old-growth forest with few signs of logging, and the other stand was selectively logged 60–80 years ago. Altogether 118 species were found. Forest management had a negative impact on the species diversity. Newly fallen and weakly decayed logs in a natural forest had a higher species richness, more red-listed species, as well as more indicator species compared to similar logs in a managed forest. The importance of dead wood for species diversity of wood inhabiting fungi was clearly demonstrated. Presence of logs in later stages of decomposition increased the total species number in a natural forest stand with 42 (63 %), compared to a survey of only newly fallen and weakly decayed logs. Presence of logs in later stages of decomposition also increased the diversity of the species pool colonising newly fallen and weakly decayed logs. The highest number of fruiting species was found on intermediately decayed logs and on logs lying in contact with the ground. The fungal gradient as revealed in a DCA ordination was primarily related to decay. A successional pathway based on the primary decayer Fomitopsis pinicola was not detected.     

Germination as a determinant of seedling distributions among natural substrates in Picea engelmannii (Pinaceae) and Abies lasiocarpa (Pinaceae)

In Rocky Mountain (USA) subalpine forests, seedlings of Picea engelmannii (Engelmann spruce) colonize logs more frequently than seedlings of its codominant associate Abies lasiocarpa (subalpine fir). We hypothesized that spruce germinates more readily on logs than fir, perhaps because small spruce seeds are more likely to lodge in log crevices than larger fir seeds. Our objectives were to test this hypothesis and compare both species' germination among several substrates to assess germination influences on natural seedling distributions. Spruce and fir seeds were sown on field-collected logs, litter, and soil in the greenhouse and monitored for 36 d. To test the crevice hypothesis, seeds were either scattered on logs or wedged into crevices, assuming that if both species were placed in crevices, interspecific germination differences on logs would decrease. Spruce mean germination percentages were significantly greater than fir's in all substrate treatments except when seeds were wedged in log crevices. The difference in means between the two log treatments was greater for fir (68%) than spruce (21%). Spruce germinated more rapidly than fir on all substrates. We suggest that large seed size reduces fir's success in colonizing logs, and that germination and establishment factors interact to determine natural seedling distributions for these subalpine conifers.     

兴安落叶松老龄林落叶松林木死亡格局以及倒木对更新的影响

对兴安落叶松老龄林落叶松林木死亡格局和死亡木对更新的影响进行了研究 .结果表明 ,丛桦落叶松林和杜香落叶松林的枯立木以中径木占多数 ,赤杨落叶松林主要为中、大径木 ,草类落叶松林主要是中、小径木 .落叶松枯立木主要因火烧、受压和老死而形成 .丛桦落叶松林和赤杨落叶松林掘根倒木较多 .杜香落叶松林和草类落叶松林的倒木以风折为主 .地形、山体走向和盛行风向对树倒方向影响很大 .丛桦落叶松林倒木方向杂乱 ,赤杨落叶松林林木均向东倒下 ,杜香落叶松林和草类落叶松林的掘根木分别向南、东北方倒下 ,两者的风折木倒向随机性较大 .草类落叶松和赤杨落叶松老龄林内 ,倒木更新为 1 8和 40株·m- 2 ,远远高于矿物土基质上 2株·m- 2 的水平 .丛桦落叶松林内倒木和林地上更新均相当好 ,约为 2 8株·m- 2 .杜香落叶松林倒木更新效果不突出 .     

Effect of bryophytes on survival of conifer seedlings in subalpine forests of central Japan

Bryophytes form the major seedbed for coniferous trees in the subalpine forests of central Japan. Field experiments were conducted on the floor of a closed stand dominated byTsuga on Mt Fuji to examine the seedling survival ofAbies veitchii andTsuga diversifolia in seven substrate types in relation to the morphological characteristics of the seeds and seedlings. NeitherAbies norTsuga seedlings could survive on dwarf-bamboo litter beyond 2 years after the seed rain.Abies seedlings survived not only in all types of bryophyte communities but also in larch litter. In contrast, the survival ofTsuga seedlings was restricted to communities of smaller-statured bryophytes found on logs. The seeds and 1st year seedlings ofA. veitchii were larger than those ofT. diversifolia. Abies seedlings produced hypocotyls taller than any bryophyte community and radicles which were long enough to penetrate into the moist humus layer, whereasTsuga seedling radicles presumably penetrate into humus only in bryophyte communities forming a thin mat on logs. The effect of bryophytes on survival of tree seedlings therefore depends on the relationships between the morphology of seeds and seedlings and the structure of bryophyte communities.     

Gnawing damage by rodents to the seedlings ofFagus crenata andQuercus mongolica var.grosseserrata in a temperateSasa grassland-deciduous forest series in southwestern Japan

The effects of dwarf bamboo,Sasa, cover on the initial morrality of hardwood seedlings were investigated by transplanting 1-year-old beech (Fagus crenata) and current-year oak (Quercus mongolica var.grosseserrata) seedling to three different stands; old-growth beech and secondary oak forests withSasa undergrowth, and aSasa grassland in a grassland-forest series near the top of Mt Jippo, southwestern Japan. The most frequent cause of seedling morrality was gnawing of the stems by rodents. In the beech forest, the gnawing was more likely to occur underSasa cover, suggesting that it provides a good habitat for rodents on the beech forest floor. TheSasa under growth may thus play an imporrant role in regeneration of beech forest. In the oak floor, mortality of both species was low and only a little gnawing occurred during a year. However, no natural oak seedling were found in the forest even after a mast year. This may be because most of the acorns disappeated before establishment. The early-stage demography of hardwood seedling as oak may thus play an imporrant role in regeneration of oak forest. In theSasa grassland where the seed supply is small, almost all of the seedlings died fromo gnawing regardless of the presence ofSasa cover. These factors prevent the recruitment of a sizable seedling bank. Rodents may thus play an imporrant role in maintenance of theSasa grassland.     

Interactive effects of wood decomposer fungal activities and bryophytes on spruce seedling regeneration on coarse woody debris

Decaying logs are important seedbeds in boreal and subalpine forests. However, biotic and abiotic factors and their interactions related to seedling colonization patterns on logs remain unclear. In the present study, we evaluated the influence of bryophyte communities, wood decay type (white-, brown-, and soft-rot) owing to decomposer fungal activities, and environmental abiotic factors on seedling establishment in an old-growth subalpine coniferous forest in Japan. Among the tree species recorded on the conifer logs, Picea jezoensis var. hondoensis was the most dominant. Log surfaces were covered with distinctive patches of liverwort Scapania bolanderi and moss Pleurozium schreberi (approximately 33% cover for each). Redundancy analysis showed that brown-rot in sapwood significantly affects the bryophyte and seedling community on the logs. Generalized linear models suggested that the total bryophyte cover, Scapania cover, and white-rot in heartwood positively associate with Picea seedling density, whereas Pleurozium cover and basal area of adjacent Picea adults negatively associate with Picea seedling density. Results of structural equation modeling suggested that the brown-rot of sapwood positively associates with Scapania cover that has a positive effect on Picea seedling density. Furthermore, brown-rot of sapwood inhibited the Pleurozium cover, thus contributing to the Scapania dominance on the logs. These results suggest that fungal wood decomposer activities affect colonization of Picea seedlings in an indirect way via structuring bryophyte community on the logs.     

Subalpine forest development following a blowdown in the Mount Zirkel Wilderness,Colorado

Abstract. We documented the occurrence of a 1934 blowdown in a subalpine forest in northwestern Colorado, USA. Prior to the blowdown, the stand was dominated by old‐growth Picea engelmannii ‐ Abies lasiocarpa forests. Although blowdowns are believed to trigger outbreaks of Dendroctonus rufipennis (spruce beetle), we found no detectable increase in beetle caused mortality. Forest recovery was by both release of the previously suppressed regeneration and by new seedling establishment. Both recovery pathways were dominated by Abies. The blowdown thus caused a shift in species dominance from Picea to Abies; 65 yr after the blowdown, the fallen logs and tip up mounds continue to provide favourable habitat for seedling establishment of both species. The present study shows that the legacy of blowdowns can influence forest dynamics for decades following the disturbance event.     

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.     

Soil inoculation of lodgepole pine seedlings alters root-associated fungal communities but does not improve seedling performance in beetle-killed pine stands

Extensive tree mortality in forests can change the community composition of soil fungi altering seedling establishment, a process critical to forest restoration. Disturbances that result in the loss of ectomycorrhizal fungi, in particular, may impede the establishment of tree species reliant on these symbionts for their survival. Inoculation of seedlings with soil from intact forests may improve the establishment of seedlings in such disturbances but the method has rarely been tested in the field. Here, we assess whether soil inoculation improves lodgepole pine (Pinus contorta var. latifolia) seedling performance in conspecific stands with high levels of tree mortality caused by a mountain pine beetle (Dendroctonus ponderosae) outbreak and whether underlying soil type modifies inoculation effects. We first inoculated seedlings in a growth chamber with small amounts of soils (5% volume) originating from either intact (<10%) or “beetle-killed” (>70% pine basal area killed) conspecific stands or added no soil inoculum and, after 4 months, transplanted them into 15 beetle-killed stands. After two growing seasons, root-associated fungal communities of seedlings receiving inoculum from intact stands differed in composition from those receiving inoculum from beetle-killed stands or no inoculum. However, inoculation had no effect on seedling survival, height, or biomass. Site properties, including soil texture and the resident fungal community composition, overwhelmed the effect of soil inoculation on seedling performance. Seedling survival and shoot mass was higher in sandy than loamy soils. Restoration to improve seedling performance in beetle-killed stands should consider stand-level treatments as soil inoculation at the level evaluated was ineffective.     

Conifer seedling recruitment in a southeastern Canadian boreal forest: the importance of substrate

Abstract. In order to explain conifer species recruitment in Canada's southeastern boreal forest, we characterized conifer regeneration microsites and determined how these microsites vary in abundance during succession. Microsite abundance was evaluated in deciduous, mixed and coniferous stands along a 234-yr postfire chronosequence. Conifers were most often found in relatively well-illuminated microsites, devoid of litter, especially broad-leaf litter, and with a reduced cover of lower vegetation (< 50 cm tall). Although associated with moss-rich forest floor substrates, Abies balsamea was the most ubiquitously distributed species. Picea glauca and especially Thuja occidentalis seedlings were frequently found on rotten logs. Light measurements did not show differences among seedling species nor between stand types. The percentage cover of broad-leaf litter decreased significantly during succession. Also, rotten logs covered with moss occupied a significantly larger area in the mid-successionnal stands than in early successional deciduous or late successional coniferous stands. The results suggest that the presence of specific forest floor substrate types is a factor explaining low conifer recruitment under deciduous stands, conifer codominance in the mid-successional stage, and delayed Thuja recolonization after fire. Results also suggest that some facilitation mechanism is responsible for the observed directional succession.     

Microsites for seedling establishment of subalpine conifers in a forest with moss-type undergrowth on Mt. Fuji, central Honshu, Japan

We examined microsites for the seedling establishment of Tsuga diversifolia, Abies veitchii and Abies mariesii in a subalpine coniferous forest with moss-type undergrowth dominated by Hylocomium splendens and Pleurozium schreberi on Mt. Fuji, a less-snowy mountain located on the Pacific Ocean side of the central part of Honshu Island, Japan, and compared these microsites with cases in other regions of Japan with different undergrowth vegetation (herb type, dwarf-bamboo type) under snowier conditions. L-shaped size structures with abundant seedlings and small trees were identified for all three species. Established seedlings of T. diversifolia showed remarkable preference for elevated microsites such as fallen logs and convex ground (i.e. ground raised around trunk bases), while A. veitchii and A. mariesii indicated no significant bias toward such elevated microsites in the large seedling stage. However, the relative frequency of T. diversifolia seedlings established on flat ground reached high values of 54–77%, since the relative occupation area of the flat ground was large (85–89%). Such a large share suggests that flat ground should be regarded as the most important microsite for the seedling establishment of T. diversifolia in forests with moss-type undergrowth. This preference trait for T. diversifolia observed with moss-type undergrowth has not been reported in previous studies examining forests with herb- and dwarf bamboo-type undergrowth, where T. diversifolia seedlings are scarce on the ground and restricted to elevated microsites. We conclude that the major microsite for T. diversifolia seedling establishment changes according to the undergrowth vegetation type: a large ground share for moss-type undergrowth and a small ground share for herb- and dwarf bamboo-type undergrowth.