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.     

Regeneration in subalpine coniferous forests

The regeneration process of a subalpine coniferous forest, a mixed forest ofTsuga diversifolia (dominant species),Abies veitchii, Abies mariessi, andPicea jezoensis var.hondoensis, was studied on the basis of annual ring data. The age class distribution was discontinuous and four age groups occurred in the study plot (30m×30m). The canopy layer was a mosaic of patches (83.8–133.7 m² patch area), which had different mean ages. The recruitment of canopy trees was carried out only by advance regeneration in the plot. The diameter growth ofAbies andPicea exceeded diameter growth ofTsuga in the gap.Abies lived for 200–300 years and their trunks were susceptible to heart rot.Picea lived for 300–400 years andTsuga for more than 400 years. The regeneration process derived from the analysis of the plot consisted of three phases leading to the development of a even-aged patch; (1) the establishment of saplings before a gap opening, (2) the opening of a gap in the canopy and repair of the canopy by advance regenerated saplings dominated by rapid growth species,Abies andPicea, and (3) the dying off of canopy trees as each species reached the end of its life-span, resulting in pure patches of long-livedTsuga.     

Gap characteristics and gap regeneration in subalpine old-growth coniferous forests,central Japan

Gap characteristics and gap regeneration were studied in three old-growth stands of subalpine coniferous forests in the northern Yatsugatake and the northern Akaishi mountains, central Japan. With the results of the present study and those of a previous study conducted in another locality, general features of gap characteristics and gap regeneration behavior of major tree species in subalpine coniferous forests of central Japan were summarized and discussed. Of the total 237 gaps investigated in the 14.48 ha of forested area, the percentage gap area to surveyed area, gap density and mean gap size were 7.3%, 17.2 ha⁻¹, and 43.3 m², respectively. The gap size distributions were similar among stands and showed a strong positive skewness with a few large and many small gaps; gaps <40m² were most frequent and those >200 m² were rare. Gaps due to the death of multiple canopy trees comprised 44.7% of the total ones. Canopy trees died in various states; standing dead (42.6%) or trunk broken (43.7%) were common and uprooted (12.2%) was an uncommon type of death of canopy trees. These figures indicate that general features of gap characteristics in this forest type are the low proportion of gap area and the high proportions of small gap size and multiple-tree gap formation. In general, shade-tolerantAbies frequently, andTsuga, infrequently, regenerate in gaps from advance regenerations recruited before gap formation, whilePicea and shade-intolerantBetula possibly regenerate in gaps from new individuals recruited after gap formation. Gap successors of conifers occurred in a wide range of gap size and did not show the clear preference to species specific gap size. In old-growth stands without large-scale disturbance (≥0.1 ha in area) of subalpine coniferous forests of central Japan, major tree species may coexist with their different gap-regeneration behaviors and, probably, different life history traits.     

State of fallen logs and the occurrence of conifer seedlings and saplings in boreal and subalpine old-growth forests in Japan

Fallen logs on the forest floor play an important role in tree seedling establishment in boreal and subalpine old-growth forests. We examined the abundance and state (degree of decay, moss coverage on their surfaces) of fallen logs on the forest floor and compared the occurrence of conifer seedlings and saplings on soil and fallen logs in old-growth evergreen boreal (Taisetsu) and subalpine (Yatsugatake) coniferous forest stands in Japan. The forest floors of both stands were covered mostly by soil, and fallen logs covered only a small proportion (4.5% in Taisetsu and 2.5% in Yatsugatake) of the forest floor. In both stands, no seedlings were found on freshly fallen logs. Both moss coverage and the occurrence of seedlings or saplings on fallen logs increased with decay in both stands. In Taisetsu, the occurrence of all conifer seedlings and saplings was, in general, restricted to fallen logs. In contrast, in Yatsugatake, Picea and Tsuga seedlings occurred much more frequently on fallen logs than on soil, whereas Abies seedlings and saplings became established on both soil and fallen logs. Seedlings were taller on decayed fallen logs, but taller saplings were rare on fallen logs in Yatsugatake. Results indicate that species characteristics, the condition of the fallen logs and environmental factors determine the preponderance of seedling and sapling establishment on fallen logs. The condition of fallen logs varies with the degree of decay, and fallen logs that function as seedling establishment sites on the forest floor are thought to be limited by time and space.     

三种不同类型亚高山森林凋落物输入对土壤腐殖化的影响

森林凋落物既是土壤腐殖质的主要来源,也可以通过新鲜凋落物中易降解组分的输入激发土壤原有腐殖质的降解,导致其相互关系并不明确。以王朗国家级自然保护区内的典型亚高山针叶林、针阔混交林以及阔叶林为研究对象,开展土壤原位培养试验,设置允许凋落物正常输入和去除凋落物两种处理,分析2017年-2019年期间不同凋落物处理下森林土壤可提取腐殖物质的光密度特征,研究土壤腐殖化程度与凋落物的关系。结果表明,在2年的试验过程中,3种森林土壤的腐殖化程度整体表现为针叶林>混交林>阔叶林,均展现出在冬季降低,生长季增加的动态规律;凋落物对3个森林的土壤腐殖化程度均无显著影响,但凋落物输入明显改变了土壤腐殖化程度的季节性变化趋势,且在冬季的阔叶林和混交林中表现更为突出。冬季凋落物的输入使得阔叶林和混交林土壤的腐殖化程度明显降低,而生长季凋落物输入对3种森林土壤腐殖化程度无显著影响。这些结果表明气候变暖情景下冬季温度的上升可能导致土壤的腐殖化程度增加,但凋落物的存在可以减缓增加的趋势。这些结果对于具有明显季节性冻融且对气候变化敏感的亚高山森林土壤肥力管理及可持续经营具有一定的科学意义。     

Comparative study of the mass loss rate of moss litter in boreal and subalpine forests in relation to temperature

The mossHylocomium splendens shows a very wide distribution in the Northern Hemisphere and may be useful as an indicator of climatic change on a global scale. We aimed to establish a convenient method to estimate the annual rate of litter mass loss of this species. The rate was calculated from the annual litter production rate and the amount of litter accumulated in the field. The litter production rate was estimated by analysis of the moss shoot growth. The rates calculated by this method tended to be larger than estimates obtained by the litter bag method. Using this method, we examined the difference in the litter mass loss rate along the altitudinal and latitudinal temperature gradients. The moss samples were collected from three boreal forests in Canada and four subalpine forests in Japan. At the subalpine sites, the annual rate of litter mass loss was within the range of 10–24% and tended to be smaller with increasing altitude. The rates in the boreal sites were similar to those in the subalpine sites despite lower mean annual temperatures. A significant log-linear relationship was observed between the annual mass loss rate and the cumulative value of monthly mean air temperatures higher than 0°C (CMT). Nitrogen concentration of the litter was positively correlated with mean annual air temperature. Site to site variation in the annual mass loss rate was largely explained by CMT and nitrogen concentration of the litter.     

Forest succession in the subalpine region of Mt. Fuji,Japan

Subalpine forest succession was studied on Mt. Fuji, Japan, where various types of forests in different successional phases occur owing to volcanic action. Ninety stands were subjected to ordination using an index (SI) defined by the relative basal area and the life span of component woody species, and the cover of canopy layer of the sample stands. Two different sequences of sample stands were found. One was from deciduous scrubs, through Larix kaempferi forests and Abies forests, to Tsuga diversifolia forests, and the other from Abies-Tsuga thickets to Abies forests. Through analyses of the forest structure and composition, soil survey and identification of fallen logs, the former sequence was recognized as the primary sere and the latter as a regeneration sere following gap formation. During forest succession, basal area reached a maximum in the seral phase with a multi-layered structure. The Tsuga forests, whose understory is restricted to a moss layer, were regarded as the climax. The death or fall of Tsuga stems resulted in gaps, which were subsequently occupied by Abies-Tsuga thickets. The second Abies forests were distinguished from the ones in the primary sere by the occurrence of Dryopteris and Cacalia and the lack of Rhododendron in the understorey. Both Abies forest types included Tsuga saplings. Thus, a cyclic relation is supposed between Abies and Tsuga.Nomenclature follows Ohwi (1975) and Nakaike (1982) for vascular plants, Iwatsuki & Noguchi (1973) for mosses, Inoue (1981) for hepaticae, Kashiwadani (1981) for lichens, respectively. Abies veitchii, A. mariesii were lumped as Abies spp.I wish to express my sincere gratitude to Prof. Toshio Hamaya, Tokyo, for the cordial guidance and encouragement. I also thank Prof. M. Numata and Dr. M. Ohsawa, Chiba, Prof. K. Okutomi, Tokyo, Dr. K. Suzuki, Tokyo, Dr. M. Suzuki, Kanazawa, and Mr. H. Taoda, Kumamoto, for their valuable advice and discussions.     

短期夜间增温对亚高山针叶林云杉幼苗根系分泌物速率和化学成分的影响

以连续7a红外辐射增温处理下的云杉幼苗为对象,定量分析了增温对植物根系碳(C)、氮(N)分泌速率以及主要挥发性化学成分的影响。结果表明:(1)增温显著增加了云杉幼苗根系C分泌速率,而对N分泌速率无显著影响,并伴随着根系分泌物C∶N化学计量比显著增加;(2)不同化学组分输入含量变化对增温的响应具有明显差异,其响应幅度和方向与化学组分种类有关。其中糖类、氨基酸和酚类化合物的含量在增温处理下均显著增加,而酯类、醚类相对含量显著降低;(3)进一步分析表明,同组分中不同化合物成分含量对增温的响应也有所差异。例如,增温仅导致酚类化合物中2,6-二叔丁基-4-甲基苯酚和4-叔丁基杯[4]芳烃含量显著增加(分别比对照增加了88.9%和375.7%),而对其余酚类化合物成分含量无显著影响。结果表明增温可导致植物根系分泌物各组分相对含量发生深刻地变化,这对于进一步认识不同环境变化下根系分泌物输入及其所诱导的特异性土壤微生物养分过程具有重要的理论意义。     

季节性冻融期间亚高山森林凋落物的质量变化

凋落物质量是影响凋落物分解的重要生物因子,其在季节性冻融期间的变化可能对亚高山森林生态系统过程产生显著的影响。因此,采用凋落物分解袋法,研究了岷江冷杉(Abies faxoniana)和白桦(Betula platyphylla)凋落物质量在一个季节性冻融期间(2006年10月至2007年4月)的变化。季节性冻融期间,岷江冷杉和白桦凋落物的木质素(L)和纤维素的降解率为全年降解的70%-75%,岷江冷杉和白桦凋落物的C/N、L/N和纤维素/N均显著增加,而纤维素/P均有所降低。岷江冷杉凋落物的C/P和L/P有所增加,但白桦凋落物的C/P和L/P有所降低。可见,季节性冻融期间,亚高山森林凋落物的质量发生了较为显著的变化,其显著影响了亚高山凋落物分解过程。     

Gap characteristics and gap regeneration in a subalpine coniferous forest on Mt Ontake,central Honshu,Japan

Gap characteristics and gap regeneration were studied in three mature stands belonging to different community types in a subalpine coniferous forest on Mt Ontake, central Honshu, Japan. Gap disturbance regimes were remarkably similar among stands studied; percentage gap area to surveyed area, gap density and mean gap size were 7.3–8.5%, 17.8–20.0 ha⁻¹ and 40.8–42.5 m², respectively. The gap size class distributions were also similar and showed a strong positive skewness with a few large and many small gaps; gaps <40m² were most frequent and gaps >200m² were rare. Forty-five to 66% of gaps were due to the death of single canopy trees. Canopy trees more often died leaving standing dead wood (40–5.7%) or broken trunks (43–49%). Shade tolerantAbies mariesii andAbies veitchii, frequently, andTsuga diversifolia, less frequently, regenerated in gaps, from advance regenerations recruited before gap formation.Picea jezoensis var.hondoensis may regenerate in gaps, from new individuals recruited after gap formation. The breakage of denseSasa coverage and the mineral soils exposed by the uprooted plants that form gaps might provide regeneration opportunities for shade intolerantBetula. Of the important species limited to the ridge site,Chamaecyparis obtusa, frequently, andThuja standishii, infrequently, regenerated from plants alreadyin situ. Regeneration ofPinus parviflora was not seen. Based on the gap characteristics and gap regeneration behaviour of each species described, stand dynamics in each stand are discussed.     

Structure and regeneration ofFraxinus spaethiana-Pterocarya rhoifolia forests in unstable valleys in the Chichibu Mountains,central Japan

The structure of temperate deciduous forests dominated byFraxinus spaethiana andPterocarya rhoifolia in V-shaped valleys in the Chichibu Mountains, central Japan was studied to clarify their dynamics, with special reference to disturbance. Forest structure and annual ring analysis revealed that the forests have been subjected to mass movement (mud flow) in the past. The size and age structure, and diameter growth curves, indicated thatF. spaethiana is relatively shade tolerant, long living and slow-growing, whileP. rhoifolia is less shade tolerant, short living, but fast growing.Pterocarya rhoifolia appears to depend on large-scale but rare disturbances.Fraxinus spaethiana establishes its seedlings on relatively unstable substrate in V-shaped valleys, but once established, they survive a long time with high shade tolerance. The dominance and coexistence of the two species may primarily depend on the intensity and frequency of geomorphological processes.     

林窗对岷江冷杉幼苗生存过程的影响

岷江冷杉林是我国西南亚高山暗针叶林的主体之一,其健康的种群动态和更新策略在维持长江上游生态安全方面具有重要意义。为了解岷江冷杉更新过程中林窗对幼苗种群动态的影响,通过调查林窗内和林下岷江冷杉更新幼苗的存活情况,采用数量分析方法研究了幼苗的年龄结构和动态特征。结果表明:林窗内和林下岷江冷杉幼苗的年龄结构金字塔均为两头小中间大的纺锤型,存活曲线均为DeeveyⅡ,生命期望以1龄级的最高、林下种群的高于林窗种群。幼苗的死亡率、消失率、累计死亡率和危险率均随龄级的增加而增大,生存率和死亡密度随龄级的增加而减小;岷江冷杉幼苗种群的数量化动态指数Vpi=0.1059,为增长型种群,在外界随机事件干扰时也可持续增长,尤以林窗种群抵御随机干扰、持续增长的特点更为突出;岷江冷杉幼苗种群的周期波动主要受基波控制,林窗种群在9龄级和11龄级处的波动还受谐波的影响。林窗扩大了岷江冷杉更新幼苗的数量规模、提高了种群抵御外界随机干扰的能力。因此,在岷江冷杉林更新管理中,应高度重视林窗的作用。     

The regeneration process in a mixed forest in central Hokkaido,Japan

The regeneration process in a mixed forest was investigated in Nopporo National Forest, Hokkaido. The analysis of age structure in an 80 m×80 m plot revealed that almost all of the species regenerated intermittently. In eleven gaps observed in the plot, the regeneration of a boreal conifer (Abies sachalinensis) was seldom observed. Temperate hardwoods, even climax species (Acer mono, Quercus mongolica var. grosseserrata, Tilia japonica), regenerated vigorously in the gaps. The age structure in ten additional plots scattered all over the forest showed that Abies tended to regenerate synchronously. From previous records, regeneration of Abies could be ascribed to catastrophic storms causing serious windfalls. On the other hand, regeneration of the temperate hardwoods was not synchronous but independent in different places within the forest. They could regenerate not only after those catastrophic storms but also after less severe disturbances which caused the death and fall of one or several trees. It is concluded that the coexistence of boreal coniferous species and temperate deciduous broad-leaved species in mixed forests may be maintained not only by the difference in habitat but also by the balance between the less frequent large disturbances, and the more frequent smaller ones.     

川西亚高山针叶林土壤颗粒的分形特征

分形理论为土壤等复杂体系的定量化研究提供了一种有效工具。本文以12个川西亚高山针叶林土壤颗粒组成数据为基础,运用分形模型研究了亚高山针叶林土壤颗粒的分形维数。结果表明,12个川西亚高山针叶林表层土壤颗粒的分形维数D为2.5209~2.7978。通过逐步多元回归分析,土壤颗粒分形维数仅与<0.001 mm颗粒含量的相关系数达极显著。土壤颗粒分形维数与土壤有机质含量、全氮含量和pH相关性不显著,然而土壤有机质含量与全氮含量呈极显著正相关。本研究探讨了利用土壤颗粒粒径分布的分形维数来定量表征川西亚高山针叶林土壤的特征。     

Picea-Abies forests in the highlands of Northern Alberta

Summary Thirty stands of Picea-Abies dominated forest in highland areas of northern Alberta were studied quantitatively. The highlands are cooler and receive more precipitation than the adjacent lowlands in summer. Orthic Grey Luvisols are the most common soil type.Based on morphological criteria the Picea was basically P. glauca, the Abies mostly A. balsamea, and the Pinus nearly all P. contorta var. latifolia. The boreal floristic element in stands increases from west to east and from high to low altitude.Four Picea-Abies community types were recognized using ordination and cluster analysis: Rubus pedatus/Ptilium crista-castrensis, Cornus canadensis-Linnaea borealis, Viburnum edule/Hylocomium splendens, Calamagrostis canadensis. The 4 community types are well correlated with altitude, soil nutrient status, and 2 groups of correlated floristic and structural variables.The floristic and structural affinities of the 4 community types to those of adjacent regions are discussed.The Picea-Abies stands studied are considered to belong to a group of climax community types, with Abies dominance indicated at higher altitudes, shifting to Picea dominance at lower altitudes.Nomenclature follows Moss (1959) for vascular plants, with the exception of Dryopteris (Britton 1972) and Betula (Dugle 1966); Lawton (1971) for mosses; Schofield (1968) for hepatics; and Hale & Culberson (1970) for lichens.We thank E. M. Achuff and T. P. Achuff for field assistance; D. M. Britton, M. Dumais, M. Ostafichuk, W. Peterson and D. H. Vitt for taxonomic assistance; the Dept of Soil Science, University of Alberta and the Research Branch, Agriculture Canada for the use of laboratory equipment, Financial support was received from the Boreal Institute for Northern Studies and the National Research Council of Canada (A-2570 La Roi).     

Association between bryophytes and seedlings in Nothofagus sub-Antarctic forests

Bryophytes, which include mosses, liverworts and hornworts, indeed play a significant role in the natural dynamics of native forests. They contribute to fundamental ecological processes such as tree regeneration. In this context, the objective was to analyse the association of bryophytes with Nothofagus seedlings, as well as whether the substrates where bryophytes grew influenced bryophyte-tree seedling association, in sub-Antarctic forests at two contrasting landscapes (coastal and mountain) of Tierra del Fuego (Argentina), to better understand their impacts on the natural regeneration processes. We hypothesized that bryophytes act as a substrate for seed germination and initial regeneration growth in pure and mixed forests of N. pumilio and N. betuloides, resulting in widespread tree seedlings–bryophyte associations in all landscapes. In each forest and landscape location, 60 transects were established (10 m in length) to evaluate bryophyte cover (by point intercept method) and substrate type (bare soil, decaying wood and litter cover) where they were growing. An adaptation of the relative interaction index (RII) based on tree seedling cover associated with bryophyte species (%) and tree seedling cover in the absence of bryophytes (%) was calculated and analysed to assess competition or facilitation between bryophytes and tree seedlings. Nothofagus pumilio seedlings were less abundant in bryophytes compared to other substrates, suggesting an inhibitory effect on the germination and/or survival of N. pumilio. In contrast, the seedlings of N. betuloides, in both pure and mixed forests, exhibited higher abundance on bryophyte substrates, particularly in mosses at mountain landscape (RII = 0.83 ± 0.08 in litter and 0.62 ± 0.11 in decaying wood). These findings suggest that bryophytes play a facilitating role for N. betuloides seedlings during germination and initial phases of growth, mainly in the mountain. Therefore, their conservation promotes N. betuloides forest continuity, both in pure and mixed structures.     

土壤动物对川西高山/亚高山森林凋落物分解的贡献

采用凋落物分解袋法,研究了土壤动物对川西高山/亚高山森林代表性植物康定柳、方枝柏、红桦和岷江冷杉凋落物在分解第一年(2011年11月-2012年10月)不同关键时期质量损失的贡献.结果表明: 在凋落物第一年的分解过程中, 不同物种凋落物的分解速率大小依次为康定柳＞红桦＞岷江冷杉＞方枝柏,且均为生长季节大于冻融季节.土壤动物对凋落物分解的贡献率(P_fau)为方枝柏(26.7%)＞岷江冷杉(18.8%)＞红桦(15.7%)＞康定柳(13.2%),其中康定柳和方枝柏的P_fau在生长季节大于冻融季节,而红桦和岷江冷杉的P_fau为冻融季节大于生长季节.冻融季节土壤动物的作用与凋落物初始C、P和N/P显著相关,而生长季节则与N、C/N、木质素、木质素/纤维素显著相关.     

Effects of night warming on the uptake of inorganic nitrogen by two dominant species in subalpine coniferous forests

Aims Plant roots play a critical role in the uptake of nutrients, and nitrogen (N) absorption is considered as the first step and a pivotal process in N metabolism of plants. Our objective was to better understand the absorption of two major inorganic N forms (NH₄⁺ and NO₃^-) in subalpine coniferous forests under global warming Methods Experimental warming using infrared heater was applied to two dominant species in subalpine coniferous forests of Sichuan, China, Picea asperata and Abies fargesiivar. faxoniana. The non-invasive micromeasurement technology was used to investigate the effects of warming on the uptake rates of NH₄⁺ and NO₃^- and the potential interactions between these two ions.Important findings Results showed that the maximal net root uptake of NH₄⁺ and NO₃^-occurred at a distance of 17-18 mm and 17 mm from root tips, respectively for P. asperata. and at a distance of 11 mm and 11.5 mm from root tips respectively for A. fargesiivar. faxoniana. Experimental warming elevated the uptake rates of NH₄⁺ and NO₃^- in both species, but the interactions between NH₄⁺ and NO₃^- differed between the two species. While NO₃^- uptake was inhibited in the presence of NH₄⁺ for both P. asperataand A. fargesiivar. faxoniana, net NH₄⁺ uptake was promoted by NO₃^- supply only in P. asperata roots under experimental warming.     

A comparative phytosociological study of the subalpine coniferous forests in northeastern Asia

Previous classification systems of the subalpine coniferous forests, belonging to the class Vaccinio-Piceetea Br.-Bl. 1939, in northeastern Asia were reviewed based on phytosociological data of Korea and Japan. A new order, the Abieti nephrolepidis-Piceetalia jezoensis was proposed for the subalpine coniferous forests in the continental part of northeastern Asia. Its distribution range and subordinate vegetation units are as follows:Order Abieti nephrolepidis-Piceetalia jezoensis ordo nov.In Korea:Alliance Abieti nephrolepidis-Piceion jezoensis Song 1991Association Taxo-Pinetum pumilae Song et Nakanishi 1985Association Thujo-Abietetum nephrolepidis Song 1991Association Abieti koreanae-Piceetum jezoensis Song 1991Alliance Abietion koreanae Song 1991Association Saso-Abietetum koreanae Song et Nakanishi 1985Association Betulo saitoanae-Abietetum koreanae (Song et Nakanishi 1985) em. Song 1991In northeast China and Maritime Province of Siberia, U.S.S.R.: (one separate alliance level or the same alliance as Abieti nephrolepidis-Piceion jezoensis)Formation Abies nephrolepis form. (Wu 1980)Formation Picea jezoensis-Abies nephrolepis form. (Wu 1980)Generally the Abieti nephrolepidis-Piceetalia jezoensis develops under the dry and cool continental climate and on the monophylogenic Dark Brown Conifer Soil Group derived mostly from granite and granitic gneiss. The subalpine or subarctic coniferous forests in Hokkaido, Sakhalin and Southern Kuriles may also belong to the Abieti nephrolepidis-Piceetalia jezoensis because of their floristic composition and the historical relevance of plant geography. The subordinate vegetation units are as follows:Alliance Piceion jezoensis Suz.-Tok. ex Jinno et Suzuki 1973Association Piceo-Abietetum sachalinensis Ohba 1967Association Piceetum glehnii Suz.-Tok. ex Miyawaki 1988The Abieti veitchii-Piceetalia jezoensis hondoensis Miyawaki et al. 1968 seems to fit only to the subalpine coniferous forests of Honshu and Shikoku of the Japanese Archipelago.     

Effects of herbivore-bearing adult trees of the oak Quercus crispula on the survival of their seedlings

The acorn-producing oak Quercus crispula Blume is shade-tolerant and its seedlings were found to be underdispersed on the forest floor, forming seedling aggregations near fertile canopy trees. However, 84.4% of the seedlings were dead within 2 years, with the highest mortality near the adult canopy trees of Q. crispula. This was mostly due to the high levels of herbivory by lepidopteran larvae. The most serious damage was caused by spring consumers, which fed on the leaves of canopy trees in June and, when the food quality of the leaves declined, fell down to the forest floor to consume the juveniles, including the seedlings. Contrary to the expectation of the herbivore–host arms race theory, most of the herbivores were polyphagous. The most dominant spring consumer Telorta edentata (Leech) was also polyphagous, and its distribution on the forest floor showed a high level of association with the distribution of dead oak seedlings.