The response of forest floor vegetation and tree regeneration to deer exclusion and disturbance in a riparian deciduous forest,central Japan

The response of forest floor vegetation and regeneration of major treespecies to deer exclusion in a riparian forest were studied for 3 years withtheinteractive effects of natural disturbances. At the start of this study, deerdensity had quickly increased to a fairly high level (29–31 individualskm^–2) during the last decade and had severely reduced theamount of forest floor vegetation in the study area. Dwarf bamboos, which weredominant before, had almost diminished from the forest floor. During the studyperiod, aboveground biomass increased steadily but species diversity did notchange much in the exclosures. Outside the exclosures, the seedlings of alltreespecies were damaged greatly by deer browsing, especially the taller ones. Deerbrowsing had little effect on the emergence of tree seedlings, but deertrampling might have accelerated emergence indirectly by disturbing the soilsurface for some species. Differences in plant responses were also observed fordeer browsing and the presence of dwarf bamboo that strongly inhibits therecruitment of tree seedlings. The nine major species were classified intothreegroups according to the response of seedlings to deer browsing and disturbance.Group 1 consists of the species whose seedling survival is affected bybrowsing,but seldom by disturbances (Phellodendron amurense,Kalopanax pictus, Quercus crispulaandMalus toringo). Groups 2 and 3 consist of species adaptedto tree-fall disturbance (Betula spp.) and ripariandisturbance (Alnus hirsuta var.sibirica, Ulmus davidiana var.japonica, Populus maximowiczii andSalix sachalinensis), respectively, and seedling survivalof these two groups is principally affected by light conditions. The effect ofdeer browsing on seedling survival and growth was greater for Group 2 than forGroup 3.     

Differences in beech (Fagus crenata) regeneration between two types of Japanese beech forest and along a snow gradient

Differences in beech (Fagus crenata) regeneration were quantitatively investigated using power function analysis for the size–class (diameter at breast height, DBH) distribution and juvenile-to-canopy tree (J/C) ratio along a snow gradient throughout Japan. In snowy areas, all species combined, as well as F. crenata alone, showed constant regeneration, with parameter b≈−1.6 for the power function y=ax ^b (x=DBH, y=density), which is related to the DBH–class distribution. The good fit of the data to the function suggests that beech regenerates constantly with self-thinning patch dynamics. Parameter a, which indicates the abundance of small trunks, was high. Furthermore, the mean J/C ratio was ≈8, i.e., each parent beech tree produced eight juveniles. These results suggest that beech regenerates constantly with gap dynamics in snowy beech forests on the Japan Sea side of Japan (snowy). However, the fit of F. crenata was lower and nonsignificant in some forests in less snowy areas, despite the high fit of all species combined. In these areas, the mean of a was low, and b was often near zero for F. crenata regressions. These results suggest that the abundance of beech was low, and self-thinning was not evident because of the initial low abundance. Moreover, the mean J/C ratio was <1.0, suggesting that juvenile density was lower than that of canopy trees. Thus, the regeneration of F. crenata on the Pacific Ocean side of Japan (less snowy) is rather sporadic. Less snowy conditions may promote seed desiccation, predation of beechnuts and seedlings, and water stress. Lower F. crenata density may also reduce predator satiation and wind pollination.     

Structure and dynamics of Japanese beech (Fagus japonica Maxim.) stools and sprouts in the regeneration of the natural forests

Structure and spatial distribution of stools and root-collar sprouts of Japanese beech (Fagus japonica) were studied to clarify the regeneration processes of the stool and the population, and the ecological importance of this stool formation in five quadrats of the natural forests with different forest floor vegetation on the Pacific side of Japan. F. japonica dominates in the canopy of each quadrat. Most of sprouts formed a circle around the root-collar and lowest parts of the parent stems of the stool with the youngest sprouts at the periphery. The regeneration by seedlings was slight especially on the forest floor vegetation of the dwarf bamboo Sasa. The variety of size structure of stems and the existence of dead traces and/or dead center in each stool, the apparent difference in stool size, and the aggregations of stools in the forests suggest that stool expansion and long persistence of the stool at a given location may contribute to compensate for the scarcity of regeneration by seedlings inhibited by dwarf bamboo, and by the other shrubs and herbs.     

Separating forest continuity from tree age effects on plant diversity in the ground and epiphyte vegetation of a Central European mountain spruce forest

Forest continuity has been identified as an important factor influencing the structure and diversity of forest vegetation. Primary forests with centuries of continuity are usually more diverse than young secondary forests as forest are colonized only slowly and because the former are richer in old tree individuals. In the present study, performed in unmanaged high-elevation spruce forests of the Harz Mountains, Germany, we had the unique opportunity to separate the effects of forest continuity and tree age on plant diversity. We compared an old-growth spruce forest with century-long habitat continuity with an adjacent secondary spruce forest, which had naturally established on a former bog after 1796 when peat exploitation halted. Comparative analysis of the ground and epiphyte vegetation showed that the plant diversity of the old-growth forest was not higher than that of the secondary forest with a similar tree age of >200 years. Our results suggest that a period of >200 years was sufficient for the secondary forest to be colonized by the whole regional species pool of herbaceous and cryptogam forest plants and epiphytes. Therefore, it is likely that habitat structure, including the presence of old and decaying trees, was more important for determining plant diversity than the independent effect of forest continuity. Our results are probably not transferrable to spruce forests younger than 200 years and highly fragmented woodlands with long distances between new stands and old-growth forests that serve as diaspore sources. In addition, our results might be not transferable to remote areas without notable air pollution, as the epiphyte vegetation of the study area was influenced by SO₂ pollution in the second half of the 20th century.     

Altitudinal and seasonal variation of frost resistance of Fagus crenata and Betula ermanii along the Pacific slope of Mt. Fuji, Japan

1 Frost resistance of Fagus crenata (Siebold's beech) and Betula ermanii (Japanese mountain birch) was investigated with respect to the species' altitudinal distribution on the Pacific slope of Mt. Fuji from 1996 to 1997. Flint's Index of Injury, which is based on electrolyte leakage from freeze-injured tissue, was used to assess frost hardiness of shoots produced in the previous growing season.
2 Fagus crenata is found on the lower slopes (700–1600 m a.s.l.). Mid- to late November hardening of shoots was enhanced, midwinter damage below −30 °C reduced and dehardening delayed nearer the upper limit. To here temperatures began to rise at least 3 weeks before dehardening began. Shade crown shoots were more susceptible to deep-freeze damage than light crown shoots. If the ultimate upper distribution limit was determined by frost hardiness, F. crenata would be expected to occur up to 1800 m altitude.
3 Betula ermanii is found between 1600 m and 2800 m, and intensive hardening occurred at all altitudes during the second half of October. Frost hardiness increased considerably with altitude up to the forest limit, where frost acclimation preceded the temperature decline by 2 weeks. Once maximum frost resistance had been attained freezing to −47 °C failed to cause tissue injury. Dehardening began slightly later at the tree line, but the time–course was the same at all altitudes. Main and lateral shoots did not differ in frost hardiness.
4 Comparison of monthly air temperature minima over the past 66 years with the course of frost resistance showed that F. crenata and B. ermanii found on the Pacific slope of Mt. Fuji were unlikely to suffer damage by frost.
5 The observed uppermost distribution limit for B. ermanii at 2800 m altitude on Mt. Fuji is considered both with our observations and with previous hypotheses.     

Comparisons of soil‐water content between a Moso bamboo (Phyllostachys pubescens) forest and an evergreen broadleaved forest in western Japan

In Japan, forests of Moso bamboo (Phyllostachys pubescens, an exotic invasive giant bamboo) have naturalized and expanded rapidly, replacing surrounding broadleaved and coniferous forests. To evaluate impacts caused by these forest‐type replacements on the hydrological cycle, soil‐water content and its spatial variability in a Moso bamboo forest were compared with those in an adjacent evergreen broadleaved forest, in a case study of a stand in western Japan (northern Kyushu). The volumetric soil‐water content averaged over depths between 0 and 60 cm was consistently higher in the bamboo stand than that in the broadleaved stand. These results contrast with previous studies comparing the soil‐water content in Moso bamboo forests with that in other forest types. The sum of canopy transpiration and soil evaporation (E) in the bamboo stand tended to be larger than that in the broadleaved stand. Small canopy interception loss was reported in the bamboo forest. Therefore, the large amount of E would counterbalance the small canopy interception loss in the bamboo forest. Differences in soil characteristics between the two stands may be the main factor causing differences in soil‐water content. Spatial variation in soil‐water content in the bamboo stand was larger than that in the broadleaved stand, confirming findings in a previous series of our study. This could happen because the well‐developed root‐system in the bamboo forest enhances preferential flow in the soil. To evaluate the effects of aggressive invasion of alien giant bamboo on the ecosystem functions, we recommend further studies measuring various hydrological components in various Moso bamboo forests.     

Effects of Sika deer on the regeneration of aFagus crenata forest on Kinkazan Island,northern Japan

Kinkazan Island, a sanctuary island that has been conserved for over 100 years, is inhabited by a Sika deer population of high density (60 km⁻²). AFagus crenata forest, a climax forest of this region, was composed of only large sized trees (30–60 cm diameter breast height) and lacked young trees. However, many saplings were found inside a deer proof fence, indicating this forest had a potential to produce seedlings. They were tentatively protected by shrubs ofLeucothoe grayana var.glabra, an upalatable ericaceous shrub, but did not exceed the shrub height. Heavy browsing by the deer suppressed recruitment of saplings ofF. crenata. The forest will be reduced without population control of the deer.     

Structure and regeneration of canopy species in an old-growth evergreen broad-leaved forest in Aya district,southwestern Japan

The population structure and regeneration of canopy species were studied in a 4 ha plot in an old-growth evergreen broad-leaved forest in the Aya district of southwestern Japan. The 200 m × 200 m plot contained 50 tree species, including 22 canopy species, 3,904 trees (dbh5 cm) and a total basal area of 48.3 m²/ha. Forty one gaps occurred within the plot, and both the average gap size (67.3 m²) and the total area of gap to plot area (6.9%) were small. Species found in the canopy in the plot were divided into three groups (A, B, C) based on size and spatial distribution patterns, and density in each tree size. Group A (typical species: Distylium racemosum, Persea japonica) showed a high density, nearly random distribution and an inverse J-shaped size distribution. Species in group B (Quercus salicina, Quercus acuta, Quercus gilva) were distributed contagiously with conspicuous concentration of small trees (<5 cm dbh) around gaps. However, the species in this group included few trees likely to reach the canopy in the near future. Group C included fast-growing pioneer and shade intolerant species (e.g. Cornus controversa, Carpinus tschonoskii, Fagara ailanthoides), which formed large clumps. Most gaps were not characterized by successful regeneration of group B and C but did appear to accelerate the growth of group A. Group B species appear to require long-lived or large gaps while group C species require large, catastrophic disturbances, such as landslides, for regeneration.     

Disturbance and regeneration dynamics of a mixed Korean pine dominated forest on Changbai Mountain,North-Eastern China

We used dendrochronological methods to study disturbance history of a mixed Korean pine (Pinus koraiensis Siebold et Zuccarini) dominated forest on the northern slope of Changbai Mountain, North Eastern China, over 1770–2000. Frequent small-scale canopy gaps and infrequent medium-scale canopy disturbances dominated natural disturbance regime in the forest, which did not experience stand-replacing disturbances over the studied period. Percentages of growth releases in subcanopy trees were below 6% in most decades, suggesting that disturbances initiating these releases were of low intensity. Strong winds were likely cause of moderate disturbance events. Two episodes with increased disturbance rates (19% and 13%) were dated to the 1920s and 1980s, timing of the 1980s event was consistent with a hurricane occurred in 1986 on the western slope of the Changbai Mountain. Age structure and growth release analyses revealed species-specific regeneration strategies of canopy dominants. Shade-intolerant Olga bay larch (Larix olgensis Henry) recruited mainly before the 1860s. Recruitment of moderately shade-tolerant P. koraiensis occurred as several regeneration waves (1820s, 1850s, 1870–1880s, 1930s, and 1990–2000s) of moderate intensity. Shade-tolerant Jezo spruce (Picea jezoensis Carr. var. komarovii (V. Vassil.) Cheng et L.K.Fu) and Manchurian fir (Abies nephrolepis (Trautv.) Maxim.) regenerated continuously over the last 220 and 130 years, respectively. Enhanced recruitment of P. koraiensis, P. jezoensis, and A. nephrolepis was observed during the 1930s and 1990s, coinciding with increased growth release frequency in the 1920s and 1980s, and suggesting disturbance events of moderate intensity. Our results indicate that the current disturbance regime of the mixed Korean pine dominated forest maintains coexistence of light-demanding and shade-tolerant species and that change in wind climate may be particularly important for future forest composition.     

Spatial pattern of trees in kerangas forest,Sarawak

The 64 most abundant species (10 cm dbh) in a 400×480 m plot of predominantly kerangas forest in Sarawak were individually investigated for two-dimensional pattern by spectral analysis using the basal areas of trees in 20×20 m contiguous quadrats. All species had individuals in the upper canopy.30 species showed pattern with clumps. The most frequent scales of clump size were between 35 and 55 m across. Patterned species were less abundant in the plot, had a greater proportion of smaller (10–20 cm dbh) trees and had a lower ratio of upper to lower canopy trees than species without pattern.Trend across the plot between dipterocarp and kerangas forest types matched the change in soil from red-yellow podzol (oxisol and ultisol) to medium gleyic and bleached sand podzols (spodosol). However, soil differences and small scale (ca. 50 m) changes in topography did not account for patterns.The scale of pattern matches the size of gaps produced by windthrow. It is suggested that patterned species are light-demanding and grow from seeds in gaps, whereas non-patterned species are shade tolerant, growing within closed forest to sapling size and eventually maturing by filling smaller single tree gaps.D. McC. N. thanks the Deutsche Akademische Austauschdienst for a scholarship and the British Council for travel funds to work at Hamburg. We are grateful to A. Weiscke for entry of the 1963 field records on the computer, T. W. Schneider for helpful discussions and T. C. Whitmore for commenting on earlier drafts.Nomenclature for three species follows Whitmore (1972, 1973), Ng (1978) and Ashton (1982).     

Suppression and release during canopy recruitment in Fagus crenata and Acer mono in two old-growth beech forests in Japan

Beech forests occur widely in the mountains on the main island of Japan. Wind storm is the major regime that causes canopy disturbances in these forests. Fagus crenata Blume is a dominant, and Acer mono Maxim., also a canopy species, co-occurs in these forests. It has been suggested that A. mono is less shade-tolerant than F. crenata. Using dendrochronological data, this study describes suppression and release histories during canopy recruitment for these two species in two old-growth beech forests (at Takahara and Kaname) and provides support for the shade tolerance suggestion given above. In addition, disturbance histories over the past 130 or 160 yr in the two forests have been reconstructed. At Takahara, the forest experienced more frequent wind storms, was about 10–15 m shorter and less dense than that at Kaname. Kaname is in a heavy snow region. On average, F. crenata experienced 1.4 and 2.5 definable episodes of suppression during canopy recruitment at Takahara and Kaname, respectively. At Kaname, the average length of total suppression was 66 yr, and 34 yr at Takahara. On average, at final release, the beech trees had a diameter of 25 cm and an age of about 125 yr old, which were twice as large and twice as old as those at Takahara. In contrast, at the two sites, A. mono experienced similar average numbers of episodes (1.6 episodes at Takahara and 1.8 episodes at Kaname) and similar average length of total suppression (37 yr at Takahara and 30 yr at Kaname) during canopy recruitment. At both sites, at final release, the maple had an average diameter of about 18 cm and an average age of some 70 yr. Our results have revealed that F. crenata is able to be tolerant of a longer shade suppression than A. mono. At Kaname, the canopy disturbances deduced from tree-ring data were more intense or frequent than those at Takahara, This contrasted with occurrences of wind storms at the two sites.     

Regeneration dynamics, causal factors, and characteristics of pacific ocean-type beech (Fagus crenata) forests in Japan: A review

This paper reviews the differences in the distribution and regeneration ofFagus crenata between two types of Japanese beech forests, the Japan Sea (JS)-type and the Pacific Ocean (PO)-type, and discusses the causal factors and characteristics of these forests, particularly the PO-type.F. crenata in PO-type forests regenerates sporadically rather than constantly, whereas regeneration in the JS-type forests is relatively constant with gap dynamics.F. crenata has dominated in snowy areas both in the past, after the last glacial age, when there was less human disturbance, and in the present. Snow accumulation facilitates beech regeneration in snowy JS-type forests, but not in the less snowy PO-type. Snow protects beechnuts from damage caused by rodents, desiccation, and freezing. In addition, snow suppresses dwarf bamboo in the spring, thus increasing the amount of sunlight available for beech seedlings on the forest floor. Snow also supplies melt water during the growing season and limits the distribution of herbivores. Moreover, snow reduces the number of forest fires during the dry winter and early spring seasons. The low densities ofF. crenata impede its regeneration, because disturbed wind pollination lowers seed fertility and predators are less effectively satiated. In snowy JS-type beech forests,F. crenata dominates both at the adult and the juvenile stages because it regenerates well, while other species are eliminated by heavy snow pressure. On the less snowy PO-side, deciduous broad-leaved forests with various species are a primary feature, althoughF. crenata dominates because of its large size and long lifespan.     

Distribution of chloroplast DNA haplotypes in the contact zone of Fagus crenata in the southwest of Kanto District, Japan

We have investigated cpDNA haplotype distribution in 24 populations of Fagus crenata in the southwest of Kanto District, Japan, and clarified the extent of intermixing of haplotypes in the contact zone by additional fine-scale analysis of two areas. Two cpDNA haplotypes belonging to different lineages were detected, and their distribution had geographical structure. Intermixed populations with the two haplotypes were limited to a narrow area. The geographical boundary between the haplotypes extended from Hakone to the west of the Kanto Mountains through the northern foot of Mt Fuji. No relationship was observed between the boundary location and the current topography of the southwest of Kanto District.     

Effects of grazing and cultivation on forest plant communities in Mount Elgon National Park, Uganda

Plant communities in the montane forest of Mount Elgon National Park were studied in order to assess the impact of grazing and cultivation on species composition. Present and former land uses, tree, shrub and herb species, soil properties and the percentage cover and height of trees, shrubs and herbs were determined in 40 plots. An indirect ordination of these plots showed that species composition was primarily determined by successional stage and agricultural disturbance. In forest plots (ordinated separately) where the widest range of former and current grazing intensities had occurred, evidence of grazing history, soil phosphorus and vegetation height correlated negatively with the strongest ordination axis. Least grazed forest plots had fewer tree seedlings and saplings than more intensively grazed plots. This may be due to the increase in Mimulopsis alpina (Acanthaceae) in less grazed forest where tree regeneration might otherwise be more advanced. Tree seedlings and saplings were uncommon in the forest, rarely exceeding 30cm in height and there was no tree understorey. Although grazing is important for preserving species diversity in Mount Elgon National Park through the maintenance of species-rich grasslands, long-term effects on montane forest communities must be considered in future park management.     

Woody vegetation structure of xeric forest stands under different edaphic site conditions and disturbance histories in the Biosphere Reserve 'Parque Costero del Sur', Argentina

We studied stand structures and soil properties in an old-growth forest and two 30-yr-old second-growth stands. In the old-growth forest, the total density and basal area average 1566 trees > 1.25 m height ha^-1 and 46.73 m² ha^-1. The dominant trees are Scutia buxifolia and Celtis tala. Using multivariate techniques we distinguished three stands: PS1, dominated by S. buxifolia, is 1000 m far from the river. Its soil is shallow and loamy. PS2 and PS3, co-dominated by S. buxifolia and C. tala, are over 1200 m distant from the river. There the soil is deeper and has thicker texture and higher phosphorus and calcium concentrations than the near-the-river forest soil. Scutia buxifolia shows reverse J-shaped size-distributions and has morphological features of stress-tolerant species. Celtis tala shows oscillating decay size-curves that suggest recruitment pulses related to small gaps and it has morphological features of competitive species. Celtis tala was selectively cut in the past in the second-growth stands SNRD and SRD. The stand SNRD, 1000 m far from the river, is dominated by S. buxifolia. The second species is Schinus polygamus which presents the bell-shaped size-structure of the pioneer species. SNRD does not differ from its old-growth counterpart PS1 in total tree density, basal area and tree branching. The stand SRD, over 1200 m distant from the river, is co-dominated by S. buxifolia and by C. tala trees regenerated from stumps. SRD does not differ from its old-growth counterparts PS2 and PS3 in total tree density and basal area. As to tree branching, it does not differ from PS3, but differs from PS2. All the stands are being invaded by the exotic tree Ligustrum lucidum.The differences between the old-growth stands seem to be related to the gradients of soil texture and nutrient concentrations raising edaphic stress towards the river. In SNRD, the stress, the stress-tolerance of S. buxifolia, and the aptitude of S. polygamus to recruit in disturbed habitats seem to have prevented the post-logging recruitment of C. tala. In SRD, C. tala regenerated possibly due to a better competitive performance in a more favorable site. Under protection the second-growth stands recovered the old-growth quantitative features. We recommend the restoration of the qualitative features and the control of L. lucidum.     

Landscape patterns and plant species diversity of forest reserves in the Kanto region, Japan

Plant species richness of twenty old-growth forest reserves in the cool-temperate zone in the Kanto region, Japan were investigated to detect the effect of forest fragmentation. The species richness of trees and forest floor plants were analyzed by multiple regression models relating to nine variables on the characteristics of landscape, local habitat and forest stand. The total species diversity did not have a significant correlation with any variables of landscape patterns. In this study, single large reserve in the SLOSS discussion did not seem very effective to preserve more species. However, forest reserves in large patches tend to have relatively infrequent species. Large patches of natural forests were regarded as one of the important factors to preserve infrequent species.     

Structure and productivity along a tree height gradient in a Kandelia obovata mangrove forest in the Manko Wetland, Okinawa Island, Japan

Tree height (H) of Kandelia obovata trees decreased sharply from 5 m at the forest interior behind the terrestrial forest to 1.5 m at the forest edge near the river bank according to an increase in the yearly waterlogged period along a belt transect. The decreasing tree stature was attributed to a decrease in the asymptote of H in the D _0.1 (stem diameter at H/10)-H relationship toward the edge. The K. obovata trees were well classified into interior and edge types using a discriminant function based on the habitat-specific D _0.1–H relationships. Allometric equations, as a function of D _0.1² H, differed significantly between the interior and edge types in the estimation of the phytomasses of stems and leaves, and the leaf area per tree. On the other hand, common allometric equations were successfully established in the estimation of respective phytomasses of aboveground parts and branches. Biomass and leaf area index decreased toward the forest edge. The biomass allocation to stems decreased toward the edge, whereas those to branches and leaves increased. A dramatic change in stem diameter increment resulted in differences in the D _0.1–H relationship along the tree height gradient. Relative growth rate of biomass and light-saturated net photosynthesis, which paralleled net assimilation rate from the interior to the edge, showed their maximum peaks in the middle of the belt transect. This indicates that there exists an optimal environmental condition for growth of K. obovata trees. Leaf nitrogen content tended to increase to the edge with increasing waterlogged period.     

Internal transcribed spacer haplotype diversity and their geographical distribution in Dasyscyphella longistipitata (Hyaloscyphaceae, Helotiales) occurring on Fagus crenata cupules in Japan

Phylogeographic analysis of Dasyscyphella longistipitata (Hyaloscyphaceae, Helotiales), which occurs on decaying Fagus crenata cupules, was carried out. The ITS-5.8S regions of the 120 isolates from 12 sites in areas across Japan revealed 38 haplotypes, the majority of which comprised the haplotype designated H12 (42.5%). H12 was found in isolates from all sites, followed by H28 and H10, which were detected in isolates from 10 and 7 sites, respectively. Thirty-two haplotypes were obtained in single isolates. In the haplotype network, H12 was the root, and it formed interior clades with H28 and H10. Genetic diversity was higher in northern and southern Japan, but genetic distance was not correlated with geographical distance, nor with the phylogenetic clades of F. crenata. Therefore, it was concluded that D. longistipitata forms a genetic continuum that covers all of the areas in which it is distributed in Japan, with variations being generated in local populations from the major haplotypes.