Tukasa Hukusima

Phytosociology ofFagus hayatae forests in Taiwan

We aimed to clarify the floristic composition and phytosociological characteristics of beech (Fagus hayatae) forests in Taiwan. An attempt was also made to compare the flora of theF. hayatae forest and adjacent evergreen forests and/or Japanese beech (F. crenata) forests using information from previous phytosociological studies.F. hayatae forests are confined to a small part of north-eastern Taiwan. Thus, sampling sites were designed to cover all the knownF. hayatae forests. A total of 23 relevés were sampled and 163 species were recorded. The number of common species betweenF. hayatae forests and other forest ecosystems such as lower evergreen forests and Japanese forests were compared. Adjacent evergreen, broad-leaved forests in Taiwan consist of 29 common species withF. hayatae forests, while 57 component species ofF. hayatae forest were found common with the Japanese forests. A vegetation table was developed and one association (Yushanio-Fagetum hayatae Suzuki T. 1954, ex Hukusimaet al. 2004), with two subassociations and four variants were identified. In addition, a higher phytosociological unit was defined, in which the alliance Fagion hayatae Suzuki T. ex Hukusimaet al., the order Fagetalia hayatae nov.; and the class Fagetea crenatae Miyawaki, Ohba et Murase, 1964 were identified and/or proposed.F. hayatae forests in Taiwan distribute mainly on the summit and ridge part of the north-eastern mountains and were considered relict forest.RiassuntoLa presente ricerca ha lo scopo di chiarire i problemi riguardanti composizione floristica e caratteristiche fitosociologiche delle foreste di faggio (Fagus hayatae) a Taiwan. Viene inoltre presenta la comparazione di questa foresta con le foreste sempreverdi adiacenti e/o con le foreste del faggio giapponese (F. crenata), sulla base di informazioni derivanti da studi precedenti. Le foreste diF. hayatae sono confinate in un’area ristretta nel nordest di Taiwan. Pertanto, i siti campionati sono stati distribuiti in modo da rappresentare tutti i boschi diF. hayatae conosciuti. Sono stati eseguiti 23 rilievi, nei quali sono state identificate 163 specie. Nella comparazione viene indicato il numero di specie in comune tra la foresta diF. hayatae ed altri ecosistemi forestali, come foreste di bassa quota dell’isola e foreste di faggio del Giappone. La vegetazione adiacente in Taiwan è formata da foreste sempreverdi, che presentano 29 specie in comune con la foresta diF. hayatae; 57 specie della foresta diF. hayatae sono presenti anche nelle faggete del Giappone. I rilievi sono riuniti in tabella e sulla base di questa viene descritta un’associazione (Yushanio-Fagetum hayatae Suzuki T. 1954, ex Hukusimaet al. 2004), nella quale sono distinte due subassociazioni e quattro varianti. Inoltre, viene definito lo schema delle unità superiori, nel quale viene proposto che l’alleanza Fagion hayatae Suzuki T. ex Hukusimaet al., e l’ordine Fagetalia hayatae nov. siano inclusi nella classe Fagetea crenatae Miyawaki, Ohba et Murase, 1964. Le foreste diF. hayatae sono distribuite nella fascia sommitale e sulla cresta dell’area montana di nordest, ed hanno caratteristiche di vegetazione relitta.

Phytosociology of the Beech ( Fagus ) Forests in East Asia

Speciation of beech (genus Fagus) in East Asia has been intensive and beech forests are widely, though disjunctly, distributed within Japan, Korea, China and Taiwan. Beech forests lie between the evergreen broad-leaved forests in the south (lower limit) and the evergreen coniferous trees in the north (upper limit), making them a key vegetation type in East Asia. In this study, to better distinguish the features of beech forests in East Asia, we compared species composition of beech forests based on the known releves and on new releves we carried out in the field. As a result of that comparison, we were able to divide the beech forests of East Asia into three classes. Classes I and II are characterized by the abundance of deciduous flora. These 2 classes contain 4 orders, 8 alliances, 20 associations and 48 subassociations. Class III is composed of evergreen broad-leaved forest with the presence of Fagus. There are few common species among the classes, especially in China. Because of that, it is hard to describe the similarities and differences of plant communities only considering the species level. For that reason, we further compared also the genus and family composition, which were considered to have larger distribution between the different vegetation types. East Asian beech forests are characterized by genera endemic to East Asia, as well as by genera common to beech forests of the northern hemisphere. Classes I and II show a large overlapping in genus composition. Within each order, there are many characteristic genera, a fact that confirms the independence of each order. In contrast, few characteristic genera are found at the alliance level, although the frequency of genera within each alliance varies. That is not the case, however, in the association and the subassociation levels. We also compared life form composition for each vegetation unit. We found the following: (1) beech forests in East Asia always contain scrub bamboo species; (2) classes I and II contain evergreen conifers of PEN and NPEN life forms. Class I contains proportionally more deciduous flora, classified as life forms of PD, NPD, H scap and H rosul. Class III, in contrast, contains proportionally more evergreen flora, classified as life forms of PE, NPE and G rhiz. Class II contains an intermediate proportion of deciduous and evergreen floras. At the order level, the frequency of life forms for shrub and herb species is characteristic. At the alliance level there is much less difference in life form composition within each alliance. At both the alliance level and the order level, when the proportion of life forms indicative of broad-leaved forests is higher, the proportion of herbaceous life forms is lower. There are no significant differences in life form composition within each association and subassociation; a comparison of life form compositions within the lower vegetation units would not, therefore, be useful.

The impact of extreme run-off events from the Sakasagawa river on the Senjogahara ecosystem, Nikko National Park. V. The importance of adventitious root systems for burial tolerance of different tree species

We surveyed the morphological responses of tree species buried by alluvial deposits, and measured the physicochemical properties of alluvial materials which buried each of the individual trees, on Senjogahara moor, Nikko National Park, Japan. The results showed that these species had a different capcity to form adventitious roots.Malus toringo Sieb. individuals, which had survived in spite of heavy deposits over the past 10 years, developed many adventitious roots from the buried parts of their trunks. However,Larix kaempferi Carr. andBetula platyphylla Sukatchev var.japonica Hara, which both died in heavy deposit areas, were inferior toM. toringo in the formation of adventitious roots. From these facts, we presumed that the ability to develop adventitious roots contributed to the survival of trees and resulted in the difference in burial tolerance among each species. Adventitious roots tended to form in the depositional layers which consisted of fine particle size materials. It is thought that these layers prevent gas exchange between soil and air, causing a lack of oxygen to the rhizosphere. Thus, we concluded that adventitious roots have a physiological importance in reducing the obstruction, and in the survival of buried trees.

The impact on the senjogahara ecosystem of extreme run-off events from the river Sakasagawa, Nikko National Park

During high run-off events the river Sakasagawa carries extremely large quantities of alluvial materials which are deposited in the north east corner of the Senjogahara moor.This study was initiated to examine the effects, both recent and historic, that this periodic and catastrophic inundation has had on the ecology of this area. It also questions the potential importance of alluvial deposition on the conservation of the moor as a whole. From the data presented it is clear that the present day vegetation of the north east corner of the moor represents a mosaic of vegetation reflecting differential levels of damage to the plants, deposition of alluvial material and the establishment of erosion channels in a space-time continum. The results indicate thatMalus Toringo andSalix integra can survive in the areas outside the heaviest flood damage, whereasUlmus Davidiana var.japonica, Betula platyphylla var.japonica andLarix Kaempferi are quite sensitive to flooding. SimilarlySasa nipponica var.nana is intolerant of even light alluvial deposition in contrast toLonicera caerulea var.emphyllocalyx andSpiraea salicifolia which are also still dominant beyond the zone of major alluvial deposition.

The impact of extreme run-off events from the Sakasagawa river on the Senjogahara ecosystem, Nikko National Park. IV. Changes in tree and understory vegetation distribution patterns from 1982 to 1992

In this study, a survey was made of a sample area adjacent to Senjogahara moor, Nikko National Park, in central Japan, to discover the change of vegetation over the 10 years from 1982 to 1992. The sample area, which is dominated byMalus toringo, has often suffered alluvial deposition from flooding of the river. The accumulation depth of alluvial materials deposited for 1984–1987 were measured at 266 points in the area, and for 1987–1992 at 347 points. Each tree species showed its own changing pattern of distribution area in relation to the accumulation depth of alluvial deposits. For example,M. toringo showed an increase in the number of trunks, and extended its distribution area in spite of heavy deposition, whereasBetula platyphylla var.japonica andLarix kaempferi shifted their distribution to the area that suffered only light deposition. The distribution area of shrubby and herbaceous species of understory vegetation also showed different patterns of change. In addition, the recovery of bare ground by understory vegetation was by different species in heavily and in lightly deposited areas. These facts show that there is a difference in the tolerance of different species to burial by alluvial deposits, and this difference is an important factor in successional change and mosaic formation of vegetation in a repeatedly disturbed area.

Impact of extreme run-off events from the River Sakasagawa on the Senjogahara ecosystem, Nikko National Park III. Pattern of alluvial deposition and effects on the growth ofMalus Toringo andBetula platyphylla var.japonica

In the study area at Senjogahara, there are 13 vegetational groups forming a space-time continuum in response to alluvial deposition from the River Sakasagawa. The pattern of deposition changes markedly from time to time, and the vegetation is thus a mosaic of recovery phases in different stages of development.There is marked zonation of layers of gravel, silt and organic matter in the soil profile, running sequentially from the mouth of the river back to the moor. Furthermore, there is a decrease in the depth of the water table with distance from the river mouth. The growth increment ofMalus Toringo is poor under the canopy ofUlmus Davidiana var.japonica forest, with maximum growth occurring in the areas of active alluvial deposition. The changing patterns ofMalus growth have been used to approximate the dates of major changes in the erosion channels and areas of alluvial deposition.There were five main channels in the study area. The oldest was on the west side and active ca. 35–40 yr prior to 1984, the year of sampling. Subsequently, adjacent areas further east became major drainage and erosion channels about 25–30 yr before 1984. However, after 1985 the erosion channels again showed a marked change in pattern, and currently flow into an entirely different sector, being responsible for the continuous dynamic patterns of vegetational change in this area.

The impact on the Senjogahara ecosystem of extreme run-off events from the River Sakasagawa, Nikko National Park. II: The correlation of vegetation and environmental disturbance using TWINSPAN and DCA ordination techniques

Vegetational data from Senjogahara moor, Nikko National Park, Japan have been analysed using two contrasting but parallel multivariate approaches as a basis for future studies. The plant communities objectively defined using a divisive polythetic classificatory approach (TWINSPAN) have been successfully overlayed on an ordination of the same data using detrended correspondence analysis (DCA). The results reveal a vegetational mosaic reflecting differential levels of flood damage to the vegetation and its subsequent rates of recovery, in a space-time continuum. The results from the TWINSPAN classification show that 13 plant communities are present in the sample area and these correlate closely with complete absence, slight, or extremely heavy disturbance. The form of the disturbance as either channel erosion or alluvial depositional features is shown to also correspond quite closely with the vegetational types and is reflected in the ordination axes derived from DCA.

The ecology of a beech forest on Mt. Sanpoiwadake, Hakusan National Park, Japan I. Braun-Blanquet, TWINSPAN and DCA analysis

The Lindero membranaceae-Fagetum crenatae association on Mt. Sanpoiwadake, Hakusan National Park, Japan, has been classified using traditional Braun-Blanquet methods. The association was floristically sub-divided into six communities, all of which had been included as four subassociations by Hukusima (1982). The resulting table was compared with an analogous community table derived using computer-based TWINSPAN analysis. This dual approach was shown to provide a fully objective classification by method, the subjective element in the Braun-Blanquet method thus being substantiated TWINSPAN. Subsequent ordination of the data using DCA then provided a further degree of objective evaluation allowing any misclassified stand or species to be re-examined, and at the same time displaying the detailed inter-relationships between all species or stands.

The ecology of a beech forest on Mt. Sanpoiwadake, Hakusan National Park, Japan II. The correlation of the subassociation within the Lindero membranaceae-fagetum crenatae association and environmental parameters

Detailed examination of a sample plot covered by the Lindero membranaceae-Fagetum crenatae association on Mt. Sanpoiwadake, Hakusan National Park, revealed a number of correlations between the distribution of subassociations and environmental factors.The subassociations on the south-facing slopes receive deep snow cover in winter with rapid melting in the spring. They occur on porous, freely draining soils, typical of the general range of brown forest soils. Conversely, on the north-eastern slopes there are widespread late-snow patches which delay leaf development and expansion and which provide an abundant water supply well into early summer. Under these conditions, bleached soil horizons have developed with iron pan formation, resulting in poor soil drainage, strongly correlated with quite different plant communities.

Syntaxonomy of the East Asiatic Fagus) Forests

Table 3.1 is a synoptic table of the forests dominated by the genus Fagus in East Asia. According to Table 3.1, the phytosociological system of beech forests in East Asia was classified as in Table 3.9 and the distribution map of the classified classes, orders, alliances and associations was depicted as Fig. 2.1. In Table 3.1, 68 species categorized as the species group 49 are the common species occurring in the beech forests in East Asia, although there is a regional bias. Many of the 68 species are character species of beech forests in each region.