Cm In Diameter At Breast Height Research Articles

Floristic composition, structure and regeneration status of woody plant species in Northwest Ethiopia

Most of the natural forests in Awi Zone of Northwest Ethiopia exist as patches due to increasing human disturbance. The Bradi forest in this zone was assessed for its floristic composition, structure and regeneration status of woody plant species to better understand the natural dynamics and suggest appropriate conservation strategies. A total of 60 quadrats (20mx20m) were established along transect lines running parallel to each other using systematic sampling for vegetation sampling. Height and diameter at breast height (DBH) were measured for those woody plant species >2 m in height and >2 cm in DBH. Seventy-one woody plant species that belong to 64 genera and 40 families were identified, of which 36 (50.7%), 13 (18.3%), 13 (18.3%) and 9 (12.7%) were trees, lianas, shrubs and trees/shrubs, respectively. A total of 1838 stems ha−1 with DBH >2 cm and height >2 m were recorded. Albizia shimperiana, Paveta abyssinica, Croton macrostachyus, Discopodium penninervium, Teclea nobilis were the most abundant and frequently-occurrring species in the forest. The forest had a Shannon species diversity index score of 3.84 and an evenness of 0.89. Furthermore, the forest had an average basal area of 90.03m2/ha. Woody species with high basal area value such as Ekebergia capensis, A. shimperiana, Prunus africana, and C. macrostachyus were found to have greater importance value index (IVI). According to the DBH and height class distribution, the forest had an inverted J-shaped distribution pattern. However, analysis of regeneration status at species level revealed that 27.5%, 10%, 40% and 22.5% of the woody plants had good, fair, poor regeneration and not regenerating, respectively. This calls for enrichment planting and area exclosures of the study forest.

Forest regeneration inhibition in a mixed broadleaf-conifer forest under sika deer pressure

ABSTRACT To examine the tree regeneration and forest structure under sika deer pressure, we established a 1.08 ha plot, including a 0.0176 ha fenced area, and measured DBH (diameter at breast height) and/or height of trees in 2005–2006 and 2015–2016 in a mixed forest in the Ohmine Mountains, Central Japan. Small trees (<10 cm in DBH) were few or none for most species, but for Pieris japonica. Densities of sapling trees (50 cm ≤ height < 130 cm) were not significantly different between fenced and non-fenced areas in 2005, and were significantly different in 2015. Owing to the treefalls of large trees by wind disturbances, the total basal area decreased by 1.6% from 53.3 m2/ha in 2005 to 52.5 m2/ha in 2015. In the non-fenced area, the annual mortality of the other trees (11.7%/year) than P. japonica was significantly greater than that of P. japonica (5.7%/year). The annual recruitment densities of saplings showed a great difference between fenced (1,670.5 stems/ha/year) and non-fenced areas (56.5 stems/ha/year). Although the light condition was improved by wind disturbance, sapling tree survival and growth, except for non-preferred P. japonica, had been inhibited through effects of sika deer pressure, resulting in the decrease in the saplings of preferred tree species and an increase in the saplings of non-preferred P. japonica at this study site.

Flowering and fruiting of the dioecious canopy tree Cercidiphyllum japonicum over an 8-year period in central Japan

ABSTRACT To investigate the reproductive traits of the dioecious canopy tree Cercidiphyllum japonicum, we performed visual surveys from 2000 to 2007 to assess the flowering and fruiting of 59 individuals in a riparian forest in central Japan. Flowering and fruiting were assigned to ranked categories, where 1 indicated none and 5 indicated abundant production throughout the canopy. In addition, we used conical seed traps to assess the seed production of this species at the center of the forest. Of the 59 study individuals, 20 female and 26 male trees were >26 cm in diameter at breast height (DBH) and classified into the canopy layer. The remaining smaller individuals were non-reproductive and, excluding one, were classified into the sub-canopy layer. We estimated that C. japonicum may require 100 years of growth to reach 26 cm in DBH in a riparian forest. Both sexes produced abundant flowers in all years, and males exhibited slightly higher flowering and lower variation than females. Individuals with a DBH > 50 cm tended to flower very abundantly, and this pattern was consistent with trees over 1 m in DBH. Seed-trap surveys indicated that C. japonicum seeds were dispersed annually, with inter-annual variation. We conclude that C. japonicum is quite slow to reach sexual maturity, but can produce very abundant flowers, fruits, and seeds annually throughout its long lifespan.

DORMANCY OVERCOMING OF Schizolobium amazonicum Huber ex Ducke. (CAESALPINOIDEAE) SEEDS

&lt;p&gt;Paricá is a large tree, reaching between 15 and 40 m in height and 50 to 100 cm in DBH (diameter at breast height), when measured at distance of 1.3 m from the ground. Most leguminous species, such as paricá, have exogenous integument-type dormancy. Therefore, the aim of this work was to evaluate the germination of Schizolobium amazonicum seeds collected in the northeastern region of the state of Pará. Treatments to overcome dormancy were: (T0) control (without treatment); (T1) - immersion in water at 100 °C during 10 m; (T2) manual scarification with # 40 sandpaper at the top of the seed, opposite to the embryo; and (T3) mannual topping. For the germination of S. amazonicum seeds, tegument scarification with sandpaper showed to be the most effective pre-germinative treatment, with higher germination and normal seedlings percentage. This technique has low cost and is easy to be applied by nurserymen.&lt;/p&gt;

Shifts in tree allometry in a tropical dry forest: implications for above-ground biomass estimation

Background: Accurate estimations of aboveground biomass (AGB) based on allometric models are needed to implement climate-change mitigation strategies. However, allometry can change with tree size.Questions: Does allometry in a tropical dry forest change with tree size? Does combining different allometric equations provide better AGB estimates than using a single equation?Study site and dates: San Agustín Ejido, Yucatán, México, 2016.Methods: Forty-seven trees of 18 species with 2.5 to 41.5 cm in diameter at breast height (DBH) were sampled. Stems and branches were sectioned, and samples were dried and weighed to estimate tree AGB. Segmented linear regression was used to evaluate changes in allometry between DBH, height and AGB. Different equations were tested for each size category identified, and the best models and model-combinations selected.Results: A shift in the AGB-height relationship was found, defining two tree-size categories (2.5-9.9 cm and ? 10 cm in DBH), with the inflection point corresponding to the average canopy height (12.2 m). The best models were AGB = exp(-2.769+0.937ln(D2HPw)) for trees &lt; 10 cm DBH and AGB = exp(-9.171+1.591lnD+3.902lnH+0.496lnPw) for trees ? 10 cm DBH ( R 2 = 0.85 and R 2 = 0.92, respectively). The combination of these models produced more accurate AGB estimates than a single model or combinations involving regional models with larger sample sizes.Conclusions: These results highlight the importance of locally-developed models and suggest changes in allometry and resource allocation: towards height growth for small trees, thereby reducing the risk of suppression, versus towards AGB growth for larger trees, thereby maximizing stability and resource acquisition.

대관령 지역 경제림에 대한 내풍 안정성 분석 및 임업적 적용

본 연구는 대관령 특수조림지에 식재된 주요 경제수종인 잣나무, 전나무, 일본잎갈나무의 내풍 안정성을 비교 분석하여 조림지의 풍해관리에 대한 이해와 인식을 높이고자 수행되었다. 각 수종별로 5개씩 총 15개의 임시 방형구(<TEX>$20m{\times}20m$</TEX>)를 설치하였으며, 흉고직경 10cm 이상의 수목에 대하여 수고 및 흉고직경을 측정하였다. 수종별 수고/흉고직경 비율(h/d 비율)을 분석한 결과 잣나무와 전나무가 일본잎갈나무에 비해 비교적 낮은 h/d 비율을 나타내어 내풍성이 상대적으로 높은 것으로 보인다. 약 9%의 일본잎갈나무가 내풍 임계치(80) 이상의 h/d 비율을 나타낸 것으로 조사되었으며 이들 수목들은 풍해에 매우 취약하여 다음 간벌 기간 동안 제거되어야 할 것으로 판단된다. 분산분석 결과 수종별 h/d 비율과 흉고직경의 지니계수에서 각각 유의한 차이가 나타났다. 수종별 흉고직경의 지니계수는 전나무 16.4%, 잣나무 14%, 일본잎갈나무 14%로 나타났다. 낮은 h/d 비율은 수종별 형태학적 차이와 간벌 시업에 기인한 것으로 판단된다. 수목의 내풍성을 향상시키기 위해서는 h/d 비율이 80 이상인 수목에 대한 하층간벌이 초기 혹은 임분 분화기(stand distinction phase)에 집중되어야 한다. 산림관리자와 시업자는 수목의 h/d 비율을 측정하고 임분 밀도를 관리하여 비율을 내풍 임계치인 80 이하 수준으로 유지하여야 한다. 따라서 동령림에서 수목의 흉고직경을 증가시키기 위해서는 h/d 비율이 높은 수목에 대한 택벌이 수행되어야 할 것으로 판단된다. This study compares the wind stability of Larix kaempferi (Lamb.) Carr., Pinus koraiensis Sie. & Zucc. and Abies holophylla Maxim. to understand and inform wind risk management of these plantation trees at Daegwallyeong, Korea. Temporary square plots of <TEX>$20m{\times}20m$</TEX> (<TEX>$400m^2$</TEX>) were laid out, and DBH (Diameter at Breast Height) and height for trees greater than 10 cm in DBH were measured by species. A total of 15 plots with 5 plots each in L. kaempferi, P. koraiensis and A. holophylla stands were sampled at random. Among the species, A. holophylla and P. koraiensis have comparatively lower h/d (Height/DBH) ratios than L. kaempferi. These results indicate that the former two species are more wind firm than the latter species. About 9% of the L. kaempferi trees have higher h/d ratios than the critical threshold limit 80. These trees are vulnerable to wind damage and should be removed in the next thinning regime. The analysis of variance detected a significant difference (p < 0.05) in the h/d ratios and Gini coefficient indicating species differences and DBH size variation, respectively. Gini coefficient was 16.4% in A. holophylla, 15.9% in P. koraiensis and 14% in L. kaempferi stands indicating limited DBH size variation. Lower h/d ratios are attributed to thinning in these stands and tree morphological differences. To increase wind firmness, low thinning should concentrate to remove trees with the h/d ratio above 80 coinciding at the time of stand distinction phase. Forest managers and practitioners should measure and maintain h/d ratios of trees below the critical threshold limit of 80 through stand density management. Variable density thinning approach should be tested to increase tree DBH sizes of the even-aged stands.

Stand structure and height-diameter relationship of a degraded Populus euphratica forest in the lower reaches of the Tarim River, Northwest China

Understanding stand structure and height-diameter relationship of trees provides very useful information to establish appropriate countermeasures for sustainable management of endangered forests. Populus euphratica, a dominant tree species along the Tarim River watershed, plays an irreplaceable role in the sustainable development of regional ecology, economy and society. However, as the result of climate changes and human activities, the natural riparian ecosystems within the whole river basin were degraded enormously, particularly in the lower reaches of the river where about 320 km of the riparian forests were either highly degraded or dead. In this study, we presented one of the main criteria for the assessment of vitality of P. euphratica forests by estimating the defoliation level, and analyzed forest structure and determined the height-diameter (height means the height of a tree and diameter means the diameter at breast height (DBH) of a tree) relationship of trees in different vitality classes (i.e. healthy, good, medium, senesced, dying, dead and fallen). Trees classified as healthy and good accounted for approximately 40% of all sample trees, while slightly and highly degraded trees took up nearly 60% of total sample trees. The values of TH (tree height) and DBH ranged from 0–19 m and 0–125 cm, respectively. Trees more than 15 m in TH and 60 cm in DBH appeared sporadically. Trees in different vitality classes had different distribution patterns. Healthy trees were mainly composed more of relatively younger trees than of degraded tress. The height-diameter relationships differed greatly among tress in different vitality classes, with the coefficients ranging from 0.1653 to 0.6942. Correlation coefficients of TH and DBH in healthy and good trees were higher than those in trees of other vitality classes. The correlation between TH and DBH decreased with the decline of tree vitality. Our results suggested that it might be able to differentiate degraded P. euphratica trees from healthy trees by determining the height-diameter correlation coefficient, and the coefficient would be a new parameter for detecting degradation and assessing sustainable management of floodplain forests in arid regions. In addition, tree vitality should be taken into account to make an accurate height-diameter model for tree height prediction.

Growth, recruitment and attrition of Eucalyptus tree species in semi-arid temperate woodland

Conservation planning for many fauna relies on an ability to predict length of time lags to production of habitat requirements in restoration plantings or with natural regeneration. One key consideration is the growth rate of dominant trees, as tree age and size are linked to characteristics that provide fauna habitat, such as canopy cover, tree hollows and coarse woody debris. In this study we examined growth rate and mortality of Eucalyptus species for all individuals with diameter at breast height (DBH)⩾15cm on forty one-ha sites in temperate semi-arid woodland in eastern Australia. Over five years (2008–2013) encompassing drought and flood, mean growth was <2.5cm in DBH. Mixed effects models indicated that growth rate differed among species, and decreased with increasing senescence and greater initial foliage projective cover on the site. There was no link between initial tree DBH and growth rate for most species. Growth in DBH was similarly variable in large and small trees. Consequently increases in cross-sectional area, and hence biomass accumulation, are likely to be faster in larger trees. Growth of E. microcarpa, E. camaldulensis, E. blakelyi and E. conica did not significantly differ but was faster than that of E. populnea and E. melliodora. The random factors site and tree identity (for multi-stemmed trees) explained around 10% and 30% of the overall variability in growth rate respectively. Twelve trees (∼1%) died and 4 live trees were cut down and removed. Five (6.5%) of the 75 standing dead trees present in 2008 collapsed, and a further eight (10.5%) were cut down and removed by people. Forty saplings of four species with DBH<15cm in 2008 grew to DBH⩾15cm by 2013, equating to a recruitment rate of <4%, but this occurred on only nine of the 40 sites. Our study suggests mortality rate is being met by recruitment rate at the regional scale, but recruitment was extremely patchy and may result in site scale extinctions. The growth rates measured indicate that trees planted to create fauna habitat may take centuries to reach sizes that would contain large nesting or roosting hollows for fauna.

湘中丘陵区南酸枣阔叶林群落特征及群落更新

Broad-leaved forest community dominated by Choerospondias axillaries is one of the main forest community types in the hilly area of central Hunan province,which plays a very important role in forest succession processes in subtropical region. In this study,a large permanent plot with an area of 1 hectares was established in the typical forest community of C.axillaries at the Dashanchong forest farm,Changsha county in the hilly region. The large plot was divided into 100 smaller sample plots of 100 square meters( 10m×10m). The characteristics of the C. axillaries community were investigated in detail to analyze biodiversity and regeneration dynamics of the community. In order to investigate the plant diversity of shrub and herb in the smaller plots,16 small samples were set up and distributed evenly in the sample plots,each small sample with area of 2m×2m. Plant diversity and succession dynamics were analyzed based on these field data. The results showed:( 1) in the arborous layer,there were 59 species in total which were more than 1 cm in diameter at breast height( DBH),belonging to 25 families and 42 genera in the community;( 2) the dominant species is C. axillaries with the largest important value( IV) of 23. 57 in the community. It was characterized with normal distribution in tree heights and DBH for the tree species of C. axillaries,with only 6 saplings of 1. 0cm to 1. 5 cm in DBH.( 3) The IV was 10. 46 for Symplocos setchuensis,7. 98 for Eurya muricata,5. 39 for Vernicia montana,and 4. 17 for Litsea coreana,respectively. The ratio of saplings,with less than 1. 5 cm in DBH,varied with different tree species,which was 22. 0% of saplings for the S.setchuensis population,16. 8% for E. muricata,11. 7% for A. montana,and 11. 0% L. coreana,respectively. The diameter structures of the 4 tree species showed an inverted J curve type.( 4) Considering the stratified structure of forest stands,the overstory were mainly occupied by C. axillaries,the understorey by S. setchuensis,E. muricata,V. montana and L. coreana.( 5) Forest seedlings were mainly dominated by evergreen broad-leaved tree species which regenerated well,with exception of C. axillaries saplings. These results indicated that the advantage of C. axillaries in the community was diminishing,whileas the importance of S. setchuensis,E. muricata,V. montana and L. coreana was increasing. Those evergreen broad-leaved tree species should be the dominate species in next succession stages,suggesting the C. axillaries broad-leaved community in hilly region of central Hunan province was developing toward the evergreen broad-leaved forest community succession.( 6) There were a total of 37 species in shrub and herb layer. The species with the largest five important values are Oropetalum chinensis,Rhododendron mariesii,Vaccinium bracteatum,Gardenia jasminoides and Rhododendron simsii,with an IV of 54. 59,21. 85,4. 98,4. 63 and 4. 53,respectively. The Loropetalum chinensis and Rhododendron mariesii were both dominant species in the shrub layer.

Application of the 3PG forest growth model to a Eucalyptus globulus plantation in Northwest Spain

This paper presents an assessment of the ability of the 3PG process-based model to simulate height (h) and diameter at breast height (DBH) growth in three plots located in a Eucalyptus globulus plantation on the Atlantic coast of Galicia (Northwest Spain). The obtained results show how this model estimates adequately height (h) and DBH growth, and determination coefficients (R 2) between observed data and data predicted by the model are always higher than 0.97, root mean square error (RMSE) of 0.45–1.05 cm in DBH and 0.46–0.85 in h, and a model efficiency (EF) close to 1 (0.98–0.99). In order to improve the results predicted by the model, we propose modifying the nS and fullCanAge parameter values given by default so as to adjust growth rates in the plantation to the weather conditions in the site. The ability of the model to discriminate growth rates in the three plots must be noted, even when plots are located in the same plantation and they only show differences in aspects related to site factors. Given the obtained results in the three plots used in this study, its simplicity and the small number of parameters needed as input data, the 3PG model stands out as a very useful tool for forest plantation management.

Initial establishment and regeneration processes of an outlying isolated Fagus crenata Blume forest stand in the northernmost boundary of its range in Hokkaido, northern Japan

We investigated initial establishment and regeneration of an outlying isolated Fagus crenata forest stand at the northernmost boundary of its range in Hokkaido, northern Japan. The study site was located in the Sannosuke beech forest (42°46′48″N, 140°23′43″E), a representative outlying beech stand beyond its continuous range. A rectangular 0.75 ha plot was established on a southwest-facing slope and divided into 300 square sub-plots of 25 m2. Within each sub-plot, stems over 5 cm in diameter at breast height (DBH) were identified and measured. Furthermore, the location of stems over 10 cm in DBH (canopy stem) was recorded within each sub-plot, and their increment core samples were extracted. Wood from fallen logs was sampled to estimate the species composition of the coarse woody debris. Micro-relief of the plot was investigated by leveling with compasses for a 2.5 m × 2.5 m grid system. In the plot, the population of F. crenata was divided into three sub-populations by their frequency distribution of age. The oldest sub-population, over 121 years old, had been established in small-localized gap in the plot. The sub-population between 81 and 120 years old and the sub-population less than 80 years old were regenerated after a landslide and windthrow in a 1954 typhoon, respectively. Furthermore, dominant species in the plot shifted from Quercusmongolica var. grosseserrata to F. crenata. Consequently, regeneration of F. crenata, i.e., expansion of forest stands, at the northernmost boundary of its range was primarily dependent on episodic natural disturbance, which may be responsible for the reduction of their migration rate in Hokkaido, northern Japan.

Tree competition and species coexistence in a warm-temperate old-growth evergreen broad-leaved forest in Japan

The growth dynamics and mode of competition between adult trees ≥ 5.0cm in diameter at breast height (DBH) of nine abundant treespeciesoccupying ca. 85% of the total basal area were investigated in a 4ha study plot (200 m × 200 m) of awarm-temperate old-growth evergreen broad-leaved forest in the Tatera ForestReserve of Tsushima Island, southwestern Japan. In the plot, adult trees ≥5.0 cm DBH co-occurred with 35 woody plant species (except forwoody vine species). The most dominant and largest species,Castanopsis cuspidata var. sieboldiiexhibited a bimodal DBH distribution; it was found in both the upper and lowervertical layers. Other tree species had unimodal DBH distributionscorrespondingmostly to the lower vertical layer. We developed a model for individual growthincorporating both intra- and interspecific competition and degree ofcompetitive asymmetry. One-sided interspecific competition was detected in 17cases out of the 66 possible combinations on the scale of the 4 hastudy plot. The direction of interspecific competition was generally one-sidedfrom layer-I species to layer-II and III ones. The effects of two-sidedcompetition were detected only in layer-II and III species. OnlyDistylium racemosum exhibited one-sided intraspecificcompetition. We also found 11 cases of positive interspecific relationships.Generally, competitive relationships prevailed over positive relationshipsbetween adult trees in this warm-temperate evergreen broad-leaved forest.Competition between adult trees ≥ 5.0 cm in DBH did not occurinthe same vertical layer, but occurred only between trees in different verticallayers. This suggests that competition between adult trees ≥ 5.0cm in DBH plays a key role in the variation in species coexistencebetween different vertical layers on the 4 ha scale of thewarm-temperate evergreen broad-leaved forests. Moreover, it was found bycomparing with three different forest types that interspecific competition ismore intense in warm-temperate forests than in cool-temperate or sub-borealforests. We conclude that, compared to cool-temperate or sub-boreal forests(which have little interspecific competition), warm-temperate forests supportmore complex interspecific relationships and species-specific habitatpreferences that result in higher species diversity.

Effect of selective logging on canopy and stand structure and tree species composition in a lowland dipterocarp forest in peninsular Malaysia

The authors compared tropical rain forest canopy structure and tree species composition in two forests southeast of Kuala Lumpur, Malaysia: a primary forest and a regenerating forest that was selectively logged in 1958. For each of the forests, the study plots were set out and all trees of ≥1 cm in DBH (diameter at breast height) were mapped and measured. Canopy heights were measured in the two study plots based upon aerial triangulation using aerial photographs taken over the forests in 1997. Using this data, digital elevation models of the canopy were then constructed. The mean canopy height was greater in the primary forest (27.4 m versus 24.8 m), as was the variance in height and the number of emergent canopy trees >40 m height. The mean canopy surface area in the primary forest was nearly 1.5 times the value in the regenerating forest, and the mean crown size of canopy layer trees in the primary forest was more than twice that in the regenerating forest. The species diversity index (Fisher’s α) differed for the two forests, indicating that tree species diversity had been affected by the logging. Both forests had the same five families with the greatest stem density (stems ha −1), but the 50 most abundant species, in terms of both stem density and basal area, differed greatly between the two forests. Stem densities and basal areas were similar, but the number of stems per hectare and the basal areas of medium-sized trees (10–30 cm in DBH) were distinctly higher in the regenerating forest. These results suggest that average basal area and stem density in the regenerating forest that had been selectively logged 41 years earlier had recovered to levels similar to those in the primary forest; however, the regenerating forest had a more monotonic canopy structure comprised of medium-sized trees growing at high density. These findings also imply that structural development takes a long time to manifest in a regenerating forest as a result of the time taken for the development of emergent and canopy trees and the formation of gaps; structural development might also be delayed by the high density of medium-sized trees in the canopy layer.

Breeding Habitats of Dendrocopos major and D. minor in Urban and Rural Areas

Characteristics of breeding sites, nest trees and holes of two woodpecker species, Dendrocopos major and D. minor, were investigated in woods and parks in the urban and rural areas of Obihiro, eastern Hokkaido from April to September 1993. In D. major the numbers of nest and birds counted per 30 minutes census increased with area size, but those of D. minor did not vary. Fledging date ranged from June 23 to July 25 with an average of July 2 for D. major and from July 3 to 20 with an average of July 11 for D. minor. Neither D. major nor D. minor showed any preference in vegetation types of nesting site. Of 42 D. major nests including those found out of study areas, 22 were in woods and 20 out of woods. On the other hand, of 9 D. minor nests, 8 were found in woods and only one nest out of woods. Nest tree height, nest height, DBH (diameter at breast height) and DNH (diameter at nest height) were 13.6m, 3.7m, 35.7cm and 28.2cm respectively for D. major, and 8.0m, 3.0m, 11.0cm and 26.6cm respectively for D. minor. D. major used both live and dead trees for nesting, while D. minor used only dead trees with several holes. The minimum DNH was 19cm for D. major and 17cm for D. minor respectively. Values indicating nest sizes and volumes of D. major were larger than those of D. minor. Conditions required for nesting of two Dendrocopos species are 1)minimum area of 1.5ha where they nested, 2)live and dead trees of more than 21 cm in DBH for D. major and 3) dead trees of more than 18cm in DBH for D. minor.

Tree competition and species coexistence in a cool‐temperate old‐growth forest in southwestern Japan

Abstract. The growth dynamics and mode of competition between adult trees ≥ 4 cm in DBH (stem diameter at breast height 1.3 m) of eight abundant species occupying ca. 90 % of the total basal area were investigated in a 4‐ha study plot (200 m × 200 m) of a cool‐temperate, old‐growth forest on Mount Daisen, southwestern Japan. In the study plot, 30 tree species with individuals ≥ 4.0 cm DBH co‐occurred. A bimodal DBH distribution showing upper and lower‐canopy layers was found for the most dominant and largest species, Fagus crenata (ca. 78 % of the total basal area), whilst other tree species showed unimodal DBH distributions corresponding mostly to the lower‐canopy layer. We developed a model for individual growth incorporating both intra and interspecific competition and the degree of competitive asymmetry. Onesided interspecific competition was detected only from Fagus crenata (upper‐canopy species) to Acer japonicum and Acanthopanax sciadophylloides (lower‐canopy species) on the scale of the 4‐ha study plot. Only Acanthopanax sciadophylloides showed symmetric intraspecific competition. However, a positive (non‐competitive) interspecific relationship between adult trees prevailed over a competitive relationship; for example, individual DBH growth rate of Fagus crenata (especially lower‐canopy trees) was correlated with the abundance of Acer mono. The positive relationship represented a group of species with similar habitat preference [soil type (mature or immature) caused by landslide disturbance and the presence/absence of Sasa dwarf bamboos in the understorey], where tree densities were not so high as to bring about competition. Competitive interactions between adult trees ≥ 4 cm in DBH occurred only locally between a few specific species and were suggested to be almost irrelevant to the variation in species coexistence on the 4‐ha scale of cool‐temperate forest. Rather, the coexistence of 30 tree species (species diversity) on this large scale was suggested to be governed by the regeneration pattern of each component species (habitat preference, seedling establishment, sapling competition) with respect to landslide disturbance.

Comparison of variability in wild Camellia sasanqua Thunberg in connection with possible origin of cultivated variety.

A comparative study of variability in the wild Camellia sasanqua was conducted in 69 study sites covered the majority of the natural populations of the species in Japan. Less-disturbed broad-leaved evergreen forests within the study sites exhibited canopy trees of C.sasanqua up to 1Om in height, up to 46cm in DBH (trunk diameter a.t breast height) and average 125 years in age, while well-disturbed forests of either coppice forests or afforested plantations exhibited mostly sapling trees of C. sasanqua up to 2m in height, up to 2cm in DBH and average 10 years in age, which had large stumps up to 75 cm in diameter. All of the plants from the study sites had the same chromosome number of 2n=90 (hexaploid). The burried seeds of the seed bank have never been long-lived and stored for more than a year. Seed germination, recruitment and plant growth of more open habitats, plentifully supplied with light were expected to allow many more modules to develop. However, the seedlings appeared in low relative light intensity of 12.1% br less suffered a constant probability of death within the frst two years. Signficant correlations were seen between mean leaf length and mean petal length, between mean leaf width and mean petal width, between mean leaf area and mean petal area, between mean leaf length and mean leaf width, and between mean petal length and mean petal width. Nevertheless, those quantitative variations in leaf and flower-petal could not be correlated with differences in habitats. Only four variant forms found were as follows: (1) semi-double flower form of a bud variation in the study site No.6, (2) pinkish-white flower form in the study site No.20, (3) larger petal form in the study site No. 64, and (4) deeply crenate-margin leaf form in the study site No.69. No hybrid was seen in cross-combination between the wild C.sasanqua and its cultivars or other sympatric species which were not seasonally isolated. Since the present wild C.sasanqua was highly adapted to morphological uniformity and quantitative constancy and showed no segregation of morphological and quantitative characteristics, it could involve rarely with cultivar occurrence.