Landscape Ecol Eng (2005) 1: 135–147 DOI 10.1007/s11355-005-0015-z

O R I GI N A L P A P E R

Ikuyo Saeki

Ecological occurrence of the endangered Japanese red maple, Acer pycnanthum : base line for ecosystem conservation

Received: 7 December 2004 / Accepted: 8 April 2005 / Published online: 14 July 2005
International Consortium of Landscape and Ecological Engineering and Springer-Verlag Tokyo 2005

Abstract Japanese red maple, Acer pycnanthum K. Koch, is an endangered maple species with a very restricted natural range in the wetlands of central Honshu, Japan. In spite of its endangered status, systematic conservation action is lacking. My objective was to develop a comprehensive database and ecological description of ecosystems supporting the species to stimulate its conservation. I employed literature searches, interviews with local residents, and aerial and ground survey to determine their locations. Also, ecological characteristics and conservation status for each site were analyzed. Fifty-two main sites were identified in four prefectures. More than half of the sites were either unknown or not widely known. Aerial survey was most important in locating new and large populations. Ecosystems dominated by Japanese red maple are concentrated in the elevational range from 300 m to 600 m along three major river valleys where natural forests have been markedly altered. The populations are highly diverse in their ecological setting, geographic location, dbh distribution, and management history. The total number of clones recorded, 1,603, is over three times that of the last estimate. However, the size of wetland ecosystems supporting Japanese red maple is very small, usually £ 0.5 ha. Seedling regeneration is limited to open wetlands where human disturbances associated with agriculture prevail. Sixteen sites have been designated natural monuments where management focuses on Japanese red maple and typically simplifies the ecosystem composition and structure. Alternatively, an ecosystem approach, conserving entire wetland ecosystems, should be emphasized, and the base-line data obtained in this study will encourage various new conservation initiatives. I. Saeki Laboratory of Landscape Ecology, Faculty of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509, Japan E-mail: [email protected] Tel.: +81-42-3675749 Fax: +81-42-3675748

Keywords Endangered species Æ Wetlands Æ Ecological database Æ Aerial survey Æ Ecosystem approach Æ Biogeography

Introduction Japanese red maple, Acer pycnanthum K. Koch, is an indigenous maple species growing in central Honshu Island, Japan. It is a disjunct relative of the American red maple (A. rubrum L.), which is widely distributed in eastern North America. Unlike its counterpart species, Japanese red maple is an endangered species. It is listed as ‘‘vulnerable’’: the possibility of extinction is increasing (Environment Agency of Japan 2000), and it has a very limited natural distribution (van Gelderen et al. 1994). Rarely are the deciduous, overstory-layer tree species of the Northern Hemisphere listed as endangered species. For example, in Japan, of 1665 endangered vascular plants, there are only seven overstory deciduous taxa, including two varieties (Environment Agency of Japan 2000). Among 425 endangered and threatened species in the conterminous United States, only one canopy deciduous tree species is listed (US Fish and Wildlife Service 2004). Despite its rarity, Japanese red maple has been deeply involved with local Japanese culture. Trees become large, occasionally >30 m tall, and their wide-spreading crowns exhibit brilliant red flowers in spring and beautiful reddish–orange foliage in fall. Many large trees, even single isolated trees, have been designated as ‘‘natural monuments’’ by national and local governments to respect its rarity and scientific importance (Miyoshi 1925, 1926; Hanai et al. 2003). Large trees are often preserved at shrines and temples near natural populations. In 1835, the large gate of Tennyuuji Temple in Gifu prefecture was constructed with the wood from Japanese red maple growing near the temple (Miyoshi 1926). Ena high school, located at a center of its natural distribution, and two other schools have

136

adopted Japanese red maple as their symbol. In 1911, a seedling of Japanese red maple was presented to the prince of Japan (Miyoshi 1926) because he showed great interest in Japanese red maple during his visit to Shiga prefecture (Nomura 1914) where a large individual still grows at the Hachiman shrine. There are many interesting stories that Japanese red maple similarly has received great public attention. Japanese red maple is a relic species of geologic time. Ancestral fossil species, Acer tricuspidatum Bronn and A. tigilense Chelebaeva, were widely distributed in the Northern Hemisphere in Miocene time (Tanai 1983; Walther 1972; Wolfe and Tanai 1987). European populations became extinct in the early Pliocene due to climatic deterioration (Tanai 2001), and today red maple species only occur in central Japan and eastern North America (van Gelderen et al. 1994). Morphologically, A. pycnanthum and A. rubrum are nearly indistinguishable (van Gelderen et al. 1994), the difference being mainly in leaf lobing and other leaf characteristics (Barnes et al. 2004). Hybridization between these species produced viable seed; vigorous seedlings were verified as interspecific hybrids (Shimizu and Uchida 1993). Both species grow in wetlands such as palustrine and riverine swamps (Barnes et al. 2004; Gleason and Cronquist 1991; Hirabayashi and Takahashi 1969). Although the two maples are similar in most characteristics, the extent of their respective geographic distribution is remarkably different. American red maple is among the most widely distributed and abundant tree species in eastern North America (Walters and Yawney 1990), whereas Japanese red maple occurs only in a very limited geographic range in central Japan (Barnes et al. 2004). In addition to its limited distribution, Japanese red maple is reported becoming even rarer due to habitat deterioration by human land-use change (Environment Agency of Japan 2000). In wetlands, Japanese red maple is the dominant canopy tree species with few tree associates, e.g., Alnus and Fraxinus (Barnes et al. 2004). Despite recognition of its endangered status, no systematic conservation action has been taken except for voluntary work by the Japanese red maple conservation group in selected populations of Nagano prefecture. Thus, it is time to develop comprehensive and practical strategies to conserve ecosystems supporting Japanese red maple, not only because of their rarity but also due to this species’ intimate association with Japanese culture and its unique paleobotanical history. Furthermore, the wetland ecosystems dominated by Japanese red maple are known to have a high species diversity, including other endangered species such as Magnolia stellata (Sieb. et Zucc.) Maxim. and Clematis patens Morr. et Decne. (Barnes et al. 2004; Japanese red maple conservation group 2003). Any given ecosystem is defined as a geographic and volumetric unit of nature, a segment of Earth space including atmosphere, landforms, soil, and biota in dynamic interaction (Bailey 1996; Rowe 1961). Such site-specific, topographic units of the Earth, termed landscape ecosystems, have long

been distinguished and mapped (see pp 1–17 in Barnes et al. 1998) and those supporting Japanese red maple were classified and described by Barnes et al. (2004). Endangered plants do not stand on their own, they exist only in the context of such ecosystems (Rowe 1989; Rowe and Barnes 1994). Therefore, we should conserve and manage the composition, structure, and function of entire ecosystems in a given landscape upon which these species depend (Barnes 1993; Christensen et al. 1996; Franklin 1993; Rowe 2002). An initial step for conservation is to determine the location of existing populations and the ecosystems which support them. However, this first step, locating all occurrences of a given endangered species, is very difficult (Fujii 2002), primarily because we seldom encounter it. Searching for populations of an endangered species typically requires substantial time and effort, even for experts. I am unaware of any comprehensive documentation of occurrences of an endangered plant species except that for M. stellata (Japan association for star magnolia conservation 1996) and species that have very few populations. What is likely as a consequence of this lack of knowledge about species occurrence is that many habitats of rare and endangered species have been unwittingly altered or destroyed because land managers did not realize that the species was present. In Japan, and probably in many other countries in the world, people have repeatedly made unnecessary impacts (e.g., agricultural and urban development, timber harvest, and planting) on habitats of endangered species due to lack of the basic information about the occurrence of the species. This logic is simple, but the problem is serious. Some of the main sites of Japanese red maple populations have been described by scientists and organizations (Japanese red maple conservation group 2003; Ministry of the Environment in Japan 2004; Ogata 1965a, b). Nevertheless, a comprehensive database of main sites has not been developed and therefore the base-line data required for conservation planning are lacking. Given this situation, my general objectives were to develop a comprehensive database and ecological description of the occurrences of Japanese red maple as the basis for conservation. The specific objectives were to: (1) identify the sites now occupied by natural populations or planted individuals, (2) describe the geographical and ecological characteristics of these sites and ecosystems, (3) compare demographic features of representative populations, (4) report previous management history and conservation efforts, and (5) discuss challenges and new approaches for conservation.

Methods The occurrence of known Japanese red maple populations was addressed by studying articles, reports, books, and web sites. Publications and web sites include

137

Koidzumi (1912), Nakura (1915), Miyoshi (1926), Yokouchi (1962), Ogata (1965a, b), Hirabayashi and Takahashi (1969), and the official web site of Ministry of the Environment in Japan (2004). In addition, Mrs. A. Kitazawa (Japanese red maple conservation group) and Mr. S. Yamaguchi (Japan association for star magnolia conservation) provided information on known sites, based upon their previous work with Japanese red maple and star magnolia (M. stellata), which is often an associate of Japanese red maple. Perceiving that many more as yet undetected populations might exist, an intensive search for new populations seemed appropriate and timely. New populations are defined as ones that are not described in major publications or are described only in obscure local sources and are therefore generally unknown to the public or government officials. During the course of research on the known populations (Barnes et al. 2004), new populations were occasionally discovered. Encouraged by these findings, several additional search methods were employed to locate new populations in 2003 and 2004. This integrated survey was conducted using a four-part approach. First, I searched for Japanese red maple individuals by car and on foot near or around known populations, assuming that new individuals, in close proximity to known populations, could be found by this approach. Second, I collected information from local residents and governmental officials. Because of its striking beauty in spring and fall, knowledgeable individuals often knew the sites of Japanese red maple trees in their vicinity. Then I confirmed potential new populations by site visits. Third, aerial search was conducted by flying over the potential range of Japanese red maple on April 9, 2003, and April 1, 2004 in a fixed-wing aircraft. In these flights, maple trees with brilliant red flowers were easily spotted from the air. When any individual or group of trees was observed, the population and the surrounding landscape were videotaped. The flight altitude was about 300 m above the crown canopy, and each flight lasted 2–3 h. Finally, following each flight, the videotape was reviewed, locations of new populations were marked on topographic maps, and these sites were visited in the field. For all populations, latitude, longitude, and elevation were determined primarily from 1:50,000 topographic maps, but 1:25,000 maps were occasionally used when site locations were unclear in the smaller-scale maps. Japanese red maple populations are typically composed of a mixture of multiple-stem and single-stem clones (Barnes et al. 2004). A clone is defined as an assemblage of plants derived by asexual or vegetative multiplication from a single, sexually produced individual, generally assumed to be genetically identical. The origin of each population or single clone was determined by field observation, literature review, and information from local residents. Ecosystem components of physiography, soil, hydrology, and vegetation were used to classify wetlands dominated by Japanese red maple into four

general landforms: bog, seepage, floodplain, and boulder field, following the classification protocol by Barnes et al. (2004). The area of each population was determined and assigned to one of five categories ( £ 0.1, 0.1– 0.5, 0.5–1.0, 1.0–2.0, >2.0 ha). For the occurrence of each single-clone or group of clones (i.e., population), the number of clones, stems per clone, clone sex (female, male, non-flowering), and diameter at breast height (dbh) of all stems ‡1.5 cm were recorded. The sex ratio was determined for all clones in the natural populations. The number of overstory (>9.0 cm) and understory (1.5–9.0 cm) stems was determined for each population. The occurrence of tall seedlings (>50 cm tall, <1.5 cm dbh) and saplings of the understory size (1.5–9.0 cm) was recorded at each site to determine the amount of natural regeneration and conditions of the sites where regeneration commonly occurs. Japanese red maple trees sprout vigorously, and often two or more genetically identical stems arise from the base when an individual is severely damaged (i.e., cut) or stressed. Thus, I recorded both the number of clones and the number of stems to characterize Japanese red maple populations. If the population exceeded ca. 100 clones, data on each clone were not recorded. For example, at Sendanbayashi, data were taken just for clones in three, 10·20 m sample plots representative of the stand that included >300 clones. For the sites of Hakogawa and Niino, I used data published by the Japanese red maple conservation group (2003). For eight representative populations, I prepared dbh histograms to illustrate the demographic patterns of representative stand-development stages (Franklin et al. 2002). Conservation designation (natural monument, preserve, etc.), land ownership, management history (mowing, cutting, planting, etc.), and human-related disturbance (planting, logging practice, road construction, etc.) were recorded for all sites through field observations and interviews with landowners or individuals of the local government. All the data taken by the above procedures were organized into a database in table format and analyzed.

Results Sites and their geographic characteristics Fifty-two main sites of Japanese red maple-dominated ecosystems with three or more clones were located and described in Nagano, Gifu, Aichi, and Shiga prefectures. Most sites (23) were determined by interviews with local residents, followed by aerial survey (16), literature or government sources (10), and ground search (3) (Table 1). Sites with the most clones and stems were discovered by aerial survey (median number, 25.5 and 50, respectively), followed by literature sources (20 and 22, respectively), interviews with individuals (12 and 32, respectively), and ground search (11 and 26,

138 Table 1 Comparison of survey methods used in identifying the 52 main sites of Japanese red maple (A. pycnanthum) Survey method

Sites identified (no.)

New sites (no.)

Clones identified (median no.)

Stems identified (median no.)

Interview Aerial search Literature Ground search Total

23 16 10 3 52

8 15 0 3 26

12 25.5 20 11 –

32 50 22 26 –

respectively). In addition, I located at least 11 more populations by aerial survey that have not been visited mainly due to inaccessible terrain. Overall, 26 (50%) sites were either unknown or not widely known until this survey was conducted (Table 1). The 52 sites of Japanese red maple are remarkably diverse in their ecological setting, geographic location, and management history; 14 representative sites are presented in Table 2. The major landforms for all sites are seepage (42 sites) and floodplain (five sites). Minor landforms are boulder field–talus slope (three sites) and bog (one site). A given site, characterized by a given landform, may have several different kinds of finer-scale ecosystem types within it. For example, the Matsunoko floodplain (site 10, Table 2), a floodplain landform, has both fine-scale floodplain ecosystem types and seepage ecosystem types within it. Therefore, the ecological diversity of a site may be much greater than it appears in Table 2. The marked range in area, number of clones, and cultural treatment for a given site are illustrated by the subsample of sites in Table 2. Most of the 52 main sites are natural populations. Three populations are known or suspected to be plantings and two others are also likely of human origin. Two of the three populations known or suspected to have originated by planting are located at or near shrines: Kawaure (Nakura 1915) and Kitahanazawa (Miyoshi 1926), shown in Table 2. People living 100–300 years ago probably planted Japanese red maple trees around shrines because of their brilliant red crowns in spring and fall. At Kitahanazawa, there was a long-standing belief that Japanese red maple was respected for its religious or spiritual significance (Shiga prefectural government 2004). Also, two populations, Iyari (site 1, Table 2) and Oppara, appear to have originated by human activity because of their geographical isolation and the active human land-use in these areas. Japanese red maple is restricted geographically to a very small area in central Honshu (Fig. 1). The total area that the 47 natural sites occupy is only about 34 ha. The natural distribution lies between 35 22.1¢ N to 35 40.4¢ N latitude and 137 7.6¢ E to 137 46.5¢ E longitude. Geographically, there are two main groups of populations. The more extensive group is situated in the valleys of the Kiso and Toki rivers, which includes Tono district, southeastern Gifu prefecture. It includes approximately 67% of the sites and 72% of the clones. The second area is the Shimoina district, located in southern Nagano prefecture along

the Tenryu river. These two areas are separated by a high mountain range dominated by Mt. Ena (2,190 m; Fig. 1). The average elevation of the 47 natural populations is 469 m, with a range of 240–740 m (Fig. 2). Including single-clone sites, the lowest absolute elevation of a natural site is 160 m, and the highest is 820 m. Most clones (i.e., approximately 79%) are concentrated in the elevational range 300–600 m, although clones are notably lacking in the 400–500 m range (Fig. 3). Areas with clones that were planted or suspected of being planted are located at low or high elevations outside this elevational range (Figs. 2, 3). The area occupied by individual natural populations is very small, typically £ 0.5 ha (Fig. 4). A compact spatial arrangement characterizes Japanese red maple clones at a given site—the trees are concentrated in a small area with a high water table (e.g., Ueno and Hananoko; sites 3 and 4, Table 2). A major exception is Gotomaki (5.6 ha; site 12, Table 2) where 50 clones grow along small floodplains that drain the long, gentle slopes and seepages. Generally, however, Japanese red maple-dominated wetland ecosystems are small and have a mosaic pattern of distribution in the landscape. Demographic characteristics of populations At the 52 sites, 1,603 Japanese red maple clones and 2,741 stems were recorded. The number of clones per population was typically small (median, 19), and the majority of populations had £ 20 clones (Fig. 5). The largest population, Sendanbayashi, was estimated to have >300 clones. The markedly higher number of stems than clones reflects the vigorous sprouting ability of Japanese red maple, which is closely related to the history of cutting and light climate of the stand (Barnes et al. 2004). The average dbh of understory and overstory stems of all populations was 28.3 cm; its distribution ranged widely, from 7.6 cm to 64.5 cm (Fig. 6). The largest tree of the 52 main sites was 110.3 cm dbh, and the largest tree at a one-clone site was 155.0 cm. Striking differences among populations occurred in the pattern of dbh distribution (Fig. 7). An inverse J-shape curve at Iyari, a relatively young stand, illustrates the concentration of stems in the dbh classes <20 cm (Fig. 7a). A second pattern, with a peak in the middle of the distribution, is evident at Sendanbayashi,

Iyari

Bicchuubara Ueno Hananoko

Magome Sendanbayashi

Tsujihara Sakamoto Kamegasawa Matsunoko floodplain Noimitsuya Gotomaki Kawaure shrine

Kitahanazawa

1

2 3 4

5 6

7 8 9 10

14

Shiga

Gifu Gifu Aichi

Gifu Gifu Gifu Gifu

Gifu Gifu

Nagano Gifu Gifu

Nagano

Prefecture

Yodo

Kiso Toki Tenryu

Kiso Kiso Toki Kiso

Kiso Kiso

Tenryu Kiso Kiso

Sai

Watershed

357.8¢

3524.2¢ 3523.3¢ 3512.7¢

3529.4¢ 3528.5¢ 3524.8¢ 3524.4¢

3532.0¢ 3529.5¢

3525.6¢ 3535.2¢ 3535.1¢

3632.7¢

Latitude

13715.7¢

13724.6¢ 1379.5¢ 13740.7¢

13726.3¢ 13727.2¢ 13722.6¢ 13712.4¢

13733.7¢ 13727.5¢

13745.2¢ 13730.0¢ 13730.1¢

13751.3¢

Longitude

160

580 250 900

320 320 400 320

600 330

580 560 550

840

Elevation (m) Swamp-bog Seepage Seepage Seepage Boulder field Seepage Seepage Seepage Floodplain Floodplain Seepage Floodplain Seepage Unknown

£1 £1 £ 0.5 £2 >2 0.5 0.5 0.5 0.5

£ £ £ £ £ 0.5 >2 £ 0.5 £ 0.1

Landform

>2

Areab (ha)

5/17

22/31 50/155 17/19

24/53 >300/>300f (46/61)g 89/101 23/25 32/37 43/123

35/64 47/85 64/81

55/113

Number of clones/stemsc

b

Ordered by latitude (N–S) by prefecture Area: £ 0.1, equal or smaller than 0.1 ha; £ 0.5, 0.1–0.5 ha; £ 1, 0.5–1 ha; £ 2, 1–2 ha; >2, larger than 2 ha c Number of clones and stems whose dbh is 1.5 cm or larger d Nat. mon., natural monument e Site not widely known until research was conducted f Estimate based on field observations g Basis: three 10·20 m sample plots

a

11 12 13

Site

Site no.a

Nat. mon.

Nat. mon.

Nat. mon.

Nat. mon. Nat. mon.

Nat. mon., Preserve Bot. garden

Nat. mon.

Conservation statusd

Natural Natural Suspected human origin, understory removed, seedlings underplanted Human origin

Natural Natural, mowed Natural Natural

Possibly human origin, mowed Natural, landfill planned Natural Natural, understory removed Natural Natural

Origin, management history

Literature

Interview Plane flighte Literature

Plane flighte Literature Interview Interviewe

Literature Interview

Interview Interviewe Literature

Literature

Survey method

Table 2 Representative sites of occurrence of Japanese red maple (A. pycnanthum) and their ecological characteristics, in Aichi, Gifu, Nagano, and Shiga prefectures, central Honshu Island, Japan

139

140 Fig. 1 Map of Japan and inset of central Honshu Island showing the 52 main sites of Japanese red maple (A. pycnanthum)

Hananoko, and Noimitsuya (Fig. 7b–d). Notice that the Matsunoko floodplain population (Fig. 7e) also illustrates a similar pattern, but it includes a higher proportion of sprout stems of relatively smaller diameter than that of the other populations. This pattern is probably due to its cutting history and high light irradiance, which was caused by human disturbance (Barnes et al. 2004). A third pattern, Ueno and

Kamegasawa, (Fig. 7f, g), illustrates the occurrence of more large-dbh clones than at other sites, as well as many smaller clones. Another characteristic of this pattern is that these populations exhibit a wide range of stem size. Finally, Sakamoto (Fig. 7h) also illustrates the wide range of stem size, but the peak of the distribution is located in the large dbh range (40–50 cm) of relatively old trees.

Fig. 2 Elevational distribution of the 52 main sites of Japanese red maple (A. pycnanthum) in Aichi, Gifu, Nagano, and Shiga prefectures, central Honshu Island, Japan

Fig. 3 Elevational distribution of clones at the 52 main sites of Japanese red maple (A. pycnanthum) in Aichi, Gifu, Nagano, and Shiga prefectures, central Honshu Island, Japan

141

Fig. 4 Distribution of the areal size of the 47 natural Japanese red maple (A. pycnanthum) sites in Aichi, Gifu, Nagano, and Shiga prefectures, central Honshu Island, Japan

Fig. 6 Distribution of the average stem dbh of populations of the 52 main sites of Japanese red maple (A. pycnanthum) populations in Aichi, Gifu, Nagano, and Shiga prefectures, central Honshu Island, Japan

In general, regeneration of seedlings and saplings was rare at the 52 main sites. However, such regeneration occurred in varying amounts at 16 sites due mainly to human disturbances (Table 3). These young trees grew predominantly in open, disturbed patches with high light irradiance. Such areas occurred at the edge of newly created seepages, the edge of agricultural ponds, abandoned rice paddies, and human-built causeways. For example, at Gotomaki (site 12, Table 2), abundant saplings and seedlings were observed at the edge of seepages created by natural disturbances, whereas at Sendanbayashi (site 6, Table 2), saplings dominated the open, human-built causeways adjacent to the main population. The sites where openings were created by human disturbance (11 sites) markedly outnumbered those (five sites) where openings were formed by natural disturbance (Table 3). The sex ratio for all natural populations was 35% male, 32% female, and 33% non-flowering. Thirty-seven

populations (71%) had at least two pairs of male and female clones of dominant overstory size (>20.0 cm dbh). Fifteen of 16 populations (94%) with understory and tall-seedling regeneration were associated with populations having more than two pairs of males and females.

Fig. 5 Distribution of the number of clones per population for the 52 main sites of Japanese red maple (A. pycnanthum) in Aichi, Gifu, Nagano, and Shiga prefectures, central Honshu Island, Japan

Conservation efforts and management history Nineteen of the 52 sites have been targeted for conservation. Sixteen of them are natural monuments (seven shown in Table 2) with a history dating back to 1920 when Sakamoto (site 8, Table 2) was established. Even a site with few clones (Kitahanazawa; site 14, Table 2) may be designated as a natural monument, illustrating the importance accorded this species. The natural monuments are monitored by local community groups and government agencies. At 11 of these sites, Japanese red maple is the focus of proactive conservation activities and various types of management, such as planting, cutting, and mowing the ground cover (Table 2). At some sites, the presence of this endangered species was ignored or overlooked with negative consequences. For example, at Yamamoto, most of Japanese red maple trees were cut in winter, 2001, by the landowner to enhance the growth of planted conifers. In the Bicchuubara valley (site 2, Table 2), a large landfill was planned without due consideration of its effects on the large population of Japanese red maples. Most of the known and new sites are privately owned. At many of these sites, Japanese red mapledominated ecosystems are part of or adjacent to a conifer plantation. Such privately owned lands, e.g., Sendanbayashi (site 6, Table 2), are dominated by two widely planted conifers, Cryptomeria japonica (L. fil.) D. Don and Chamaecyparis obtusa (Sieb. et Zucc.) Endl.

142

In addition to the 52 sites, I observed many Japanese red maple trees in urban areas. These trees were planted, often symbolically or ornamentally, in public places and

private gardens. In Aichi prefecture, Japanese red maple is designated as the ‘‘Prefecture Tree,’’ which means that the species is venerated as the symbol of the prefecture.

143 b

Fig. 7 Pattern of dbh distribution for Japanese red maple (A. pycnanthum) stems in populations at eight representative sites in Gifu and Nagano prefectures, central Honshu Island, Japan. Black bars represent the distribution of the single largest stem of a given clone for all clones of the populations. White bars represent the distribution of all the other stems of a given clone for all clones of the population. a Iyari, b Sendanbayashi. Basis:3, 10·20-m plots, c Hananoko, d Noimitsuya, e Matsunoko floodplain, f Ueno, g Kamegasawa, h Sakamoto

Discussion Development and use of base-line data The base-line data of Japanese red maple occurrence were developed using several methods, all of which were useful. However, aerial search played the most important role in locating new and large populations (Table 1). Interviews with local residents were also a rewarding way to find new populations. I found that, in each local area, certain key people have intimate knowledge of the vegetation in their vicinity. Such individuals include members of conservation groups and botanical clubs, gardeners, government officers, and even ordinary citizens who happen to live near a particular Japanese red maple population. The information they provided was excellent and usually pertained to a site-specific population otherwise unknown to the general public. Therefore, a main achievement of this study was systematically gathering and integrating the pieces of information, some of which was previously either not recognized or only privately known by citizens. These base-line data for 52 main sites represent a significant starting point, but the search for new sites should be continued and the database should be revised periodically. Although the list of 52 sites appears to include most of the main populations, there are still some populations discovered by aerial search which have not been included yet due to the difficulty of access. Also, there is a possibility that some new populations were overlooked or will be established at new sites in the Table 3 Comparison of site condition and disturbance type where tall ground-cover (>50 cm tall, <1.5 cm dbh) and understory (1.5–9.0 cm dbh) regeneration of Japanese red maple (A. pycnanthum) occurred Type of disturbance

Site condition

Number of sites

Natural Human Human Human Total

Edge of naturally created seepages Edge of agricultural ponds Abandoned rice paddies Other human-caused disturbancesa

5 3 3 5 16

a

Human-constructed causeways, ponds, and open patches caused by thinning, road construction, etc.

future. Overall, we need to take additional time and effort to make the database as complete as possible for the long run. The base-line data are applicable to current conservation activities and will encourage many new initiatives. Examples of such activities include: ecological analysis of the site factors and vegetation of Japanese red maple ecosystems, monitoring the current status and future change in these ecosystems, identifying and planning specific conservation initiatives, choosing the best ecosystems as ecological models for restoration, and selecting appropriate sites for future research on vegetation composition and structure, biodiversity of flora and fauna, and the reproductive biology, regeneration, and genetics of Japanese red maple itself. Also, the ecological data provide the basis for locating sites to establish new Japanese red maple populations. Understanding the history and landscape context of the target species and the ecosystems that support it is critical for all facets of conservation and natural area preservation. Thus, this integrated survey approach is also applicable to other rare and endangered plants. Ecological and land-use characteristics of Japanese red maple ecosystems The results presented above summarize well the landscape-level characteristics of Japanese red maple ecosystems. The geographical distribution of natural populations is densely concentrated along major river valleys in central Japan, which confirms previous reports (e.g., Kurata 1973; Ogata 1965a, b). No geographical expansion of distribution was observed because of the lack of wetlands in high mountain ranges to the north and east and urbanization to the southwest. The main elevation range, 300–600 m, falls within the range of the major occurrences of wetlands in the Tono district (Ueda 1994). Spatial occurrences of Japanese red maple clones are concentrated in discrete wetland areas. This pattern is distinctive especially of seepage landforms where favorable site conditions occur on relatively flat valley bottoms that are adjacent to steep slopes. In contrast, on floodplain ecosystems, trees tend to be linearly distributed along the drainage, sometimes >30 m apart. This spatial concentration of populations is a key feature of the survey approach because the groups can be relatively easily located and mapped. The results also emphasize the geographic and ecological diversity of Japanese red maple ecosystems. There are four types of landforms that were created by different geomorphic processes. Each landform can be classified into finer-level ecosystems (Barnes et al. 2004), thereby illustrating the great diversity of wetland habitats for Japanese red maple and associated organisms. Existing populations are also variable in demographic structure, such as dbh distribution and number of sprouting stems. This diversity is probably caused by differences in the position of the ecosystem in the

144

landscape, topography, stand age, land-use history, and human disturbance, including tree cutting. When developers plan to alter habitats of endangered species, they often justify their actions by citing the presence of a nearby similar habitat. However, each Japanese red maple ecosystem is the consequence of the long natural history of the land, and it is typically unique compared to others. Thus, each occurrence should be respected, and the alternative habitat concept should be avoided. The number of individuals per population and the size of wetland ecosystems tend to be so small that careful monitoring of each one is required. They may be sensitive to the impacts of surrounding environmental changes such as road construction, which may change significantly the hydrology of wetland ecosystems. The three representative patterns of stand development stages correspond well to similar stages described by Franklin et al. (2002). The stage of regeneration initiation (Iyari, Fig. 7a) matches their cohort establishment stage. After disturbances create open wet sites near abundant seed sources, Japanese red maple regenerates in high concentrations. Sendanbayashi, Hananoko, Noimitsuya, and Matsunoko floodplain (Fig. 7b–e) fit the stages of late-canopy closure to biomass accumulation due to narrow dbh range and a concentration of small to middle-size stems. The existence of dead stems and rapid growth is also observed in these stages. The typical maturation stage following the biomass accumulation stage can be seen in Ueno and Kamegasawa (Fig. 7f,g). In this stage, Japanese red maple reaches the maximum height and re-establishment of understory trees occurs when canopy gaps providing sufficient light to the forest floor are created. This process results in a wide dbh distribution. Of the 52 sites, the late successional or old-growth stage, characterized by vertical diversification and large amounts of coarse woody debris, was notably lacking. However, Sakamoto (Fig. 7h), with trees of old-growth size, might have developed into this stage had not the site been annually mowed and woody debris apparently removed. An important restoration challenge, therefore, is to see that maturation-stage stands develop into the old-growth stage. The number of clones, 1,603, was much greater than that of the last estimate, 500 (Environment Agency of Japan 2000), indicating that Japanese red maple is not at risk of immediate extinction. Nevertheless, the remnant populations and ecosystems supporting them are probably very different from those that existed thousands to millions of years ago. In modern time, both former and potential habitats of Japanese red maple have been converted into rice paddies, agricultural ponds, conifer plantations, residential areas, and even golf courses (Environment Agency of Japan 2000). Japanese red maple ecosystems are located in landscape positions (i.e., low and flat terrain, high water table) which have been intensively altered. In addition, the Tono district, where about 70% of the populations are located, is close geographically to Nagoya, the third largest metropolitan

area of Japan. Therefore, this district has experienced enormous pressure to meet city and suburban needs through food production and the development of residential and industrial areas. The remnant populations I identified have narrowly escaped destruction by intensive land development so that most of them are fragmented into small pieces (Figs. 4, 5), which are isolated from natural forests. Small population size (Fig. 5) may be a serious problem because of the likelihood of decreased genetic diversity and reproductive potential caused by an unbalanced male–female ratio. An important challenge for the conservation is to consider practical ways to preserve these existing Japanese red maple ecosystems. Fortunately, as a result of this research, many undisturbed sites (i.e., lacking human development) are included in the database. They were unknown or overlooked in the past but are now available for conservation. In particular, Ueno, Matsunoko floodplain, and Gotomaki (sites 3, 10, 12, Table 2) exhibit near-natural conditions over a relatively large area. Japanese red maple is a dioecious species (Inoue 1996; Shimizu 1989), rarely bisexual (Kurata 1973). Dominant trees produce abundant seed crops almost every year (Barnes et al. 2004). At least two pairs of dominant female and male clones were detected in 37 of the 52 populations. I observed that seeds produced by two dominant females often result in a large amount of seedling regeneration, provided that open wetland habitat for seedling establishment is available. Seedlings require high light irradiance in order to establish and be recruited into the understory and overstory layers (Barnes et al. 2004; Goto 2002). That is why young seedlings were concentrated in open, disturbed wetlands. However, most of these areas were associated with major human disturbances, including the edges of agricultural ponds and abandoned rice paddies (Table 3). The occurrence of Japanese red maple in the Tono district, Gifu prefecture, has been reported from the late Miocene of 11–12 million years ago (Makinouchi 2001; Ozaki 1991). The continuous presence of naturally occurring wetland seepages, together with periodically flooded stream bottomlands, has enabled the species to persist. According to Ueda (1994), such seepages appeared repeatedly on a time-scale of 100–1,000 years. Geomorphic processes created small landslides, which were responsible for the formation of seepages. Substrates deposited in the Pliocene (i.e., Toki Sand and Gravel Formation) at moderate elevations contained impermeable silt and clay layers, which when excessively wet led to landslides in steep terrain. Japanese red maple is recognized as one of the members of a plant group termed ‘‘Tokai hilly land element’’ (Ueda 1989), which was favored by the repeated creation of such seepage wetlands. Today however, in the highly urbanized landscape of this region, hydrology is strongly controlled and such landslides are less likely (Ueda 1994). Therefore, lacking such naturally formed wetlands for Japanese red maple establishment, another challenge for

145

conservationists is the creation of new wetland ecosystems together with the expansion of existing wetlands already supporting the species. Implications for conservation Let us now examine several current management practices that are applied in Japanese red maple stands. Cutting understory-size stems and mowing ground cover to create park-like scenery to please visitors are popular practices. However, they change the composition, structure, and function of the ecosystems. Cutting understory stems decreases understory diversity, creates a simplified vertical stand structure, and sometimes increases the coverage of dwarf bamboo, due to increased light availability. In turn, the highly competitive bamboo tends to shade out the existing ground-cover species and prevents not only their establishment but also that of Japanese red maple seedlings. At Iyari, a well known bog and swamp in northern Nagano prefecture, managers cut understory trees and annually mow the bog and swamp to maintain a high water table as well as to create a favorable aesthetic experience for visitors. Because of these activities, however, many Japanese red maple seedlings and saplings were cut (Barnes et al. 2004). In other cases, managers believe that cutting understory trees and mowing the ground cover enhances the opportunity for regeneration of Japanese red maple seedlings in the stand. However, this practice is not ecologically sound because regeneration primarily occurs in open sites (Table 3) and not within a closed stand. Furthermore, planting seedlings under the Japanese red maple canopy at Kawaure (site 13, Table 2) was not successful because light was insufficient (personal observation). Such examples of unsuccessful management often occur at natural monuments. Japanese red maple is not only rare but is so attractive for public viewing that conscientious managers tend to think that they ‘‘must do something’’ to enhance the beauty of the stand. Also, the prevailing culture in Japan is that people should take the responsibility to shape their forests and surrounding natural environments and keep them tidy. Forests with dying trees, dead wood, and a brushy understory of shrubs and vines tend to be disliked, and so the offending elements are removed. Because of these various factors, Japanese red maple ecosystems, which naturally have a high richness of understory and ground cover (Barnes et al. 2004), have unwittingly been the focus of well meant but ecologically unsound management when designated as natural monuments. Several authors have already pointed out this ironic situation (Hiroki 2002; Ueda 1993), but it is as yet unchanged. Historically, in some secondary forests, such as traditional coppices in Japan, plant species diversity has been maintained by intensive silvicultural management (Iida and Nakashizuka 1995; Kobayashi et al. 1999; Okada 1999). However, this practice is not applicable in Japanese red maple-domi-

nated wetlands, which already exhibit high species diversity without human-caused disturbances. Thus, proactive management including cutting, mowing, and planting should be either discontinued or only undertaken with special consideration of their effects on ecosystem composition, structure, and function. The purpose of my argument is not to criticize managers of natural monuments but to examine ways that an ecological approach can increase the scope and effectiveness of their efforts. The institution of natural monuments has resulted in the preservation of many Japanese red maple populations and the education of people visiting the sites. I propose that we establish a new relationship with Japanese red maple—an attitude of sympathy and care for the endangered wetland ecosystems of which this organism is a notable part. When Japanese red maple monuments are established, individuals and the general public naturally direct their attention and management on the species itself rather than the ecosystem that supports it. Therefore, conservation is sharply focused on the species, and conservation of entire wetland ecosystems is typically overlooked or neglected. As Rowe (1989, 2002) reminds us, organisms are parts of ecosystems: the panda is a part of the mountain bamboo forest, and ducks are creatures born of marshes. Similarly, the Japanese red maple is part of mountain wetland ecosystems and can only be preserved as such. The ecosystem approach focuses on conservation of entire ecosystems or ecological ‘‘spaces’’ rather than just increasing the number of individuals and populations of a target species (Rowe 1989, 1992; Barnes 1993; Franklin 1993; Christensen et al. 1996). Therefore, the ecosystem approach can conserve processes and habitats of all constituent species, including the smaller and poorly known organisms such as invertebrates (Franklin 1993). In contrast, I perceive from my experience that the basic subconscious belief of managers of natural monuments is essentially that ‘‘everything is done for the sake of Japanese red maple.’’ The ultimate goal of management is often to maintain the Japanese red maple organism, and other components of the ecosystem, such as other plants, animals, soil, air, and water, are not high priorities. Rather than continuing this line of thought and action, I suggest that we recognize Japanese red maple as the key sign or signal of unique and endangered ecosystems, which may be in danger of alteration or destruction by human development. Thus, our conservation target should not be the Japanese red maple per se but the entire ecosystems that support it. The disappearance of such a unique mosaic of wetland landscapes contributes to a lack of total ecosystem diversity, and therefore, the biodiversity of this region at the interface of nature and civilization. Unless natural ecological systems are conserved, the native plants and animals will not be perpetuated. It is timely that another conservation approach, in addition to natural monument management, should be considered for the unprotected sites of the Japanese red maple database. More than half of the 52 main sites are

146

not legally preserved or otherwise officially recognized. Private family ownership of wetland ecosystems is dominant; these land holdings are typically small (Fig. 4). Most of the populations are located in or near urban areas. Given these conditions, urban and residential development plans are likely already underway or will emerge in the near future. Possible ways to preserve areas dominated by Japanese red maple are to designate them as community or local preserves, develop a special agreement or contract with land owners and conservation groups, and purchase the site and appropriate surrounding areas. The base-line data of occurrences can also contribute to initiating communications with land owners and negotiating how we can preserve the lands with their support. To facilitate this process, sufficient scientific information on each ecosystem dominated by Japanese red maple should be given to all the stakeholders in appropriate ways for decision-making. Overall, this comprehensive base-line data provides an opportunity to engage in a new and exciting initiative—preserving entire endangered ecosystems and their embedded flora and fauna. Acknowledgements I sincerely thank all the land owners, managers, and government officials who gave me permission to conduct research on their lands. I also thank Mrs. A. Kitazawa, Mr. S. Yamaguchi, Mr. K. Horio, Mr. H. Hara, Mr. J. Hara, Mr. K. Soga, Mr. Y. Miyashita, Mr. M. Kato, Mrs. F. Sonohara, Mr. S. Sonohara, Mr. M. Yoshizawa, Mr. Y. Sawada, Dr. T. Yoshida, Ms. T. Mori, and the late Dr. K. Inoue for their great assistance in identifying localities and other aspects of my research. Dr. J. Itoigawa and Dr. T. Tanai provided me with clear geological and paleoecological interpretations, respectively. The field assistance and comments on earlier drafts by Dr. A. Kameyama and Dr. B. V. Barnes were very helpful. Two anonymous reviewers provided valuable critiques for revisions. This research was funded in part by the Sumitomo Foundation. This paper is submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Tokyo University of Agriculture and Technology.

References Barnes BV (1993) The landscape ecosystem approach and conservation of endangered spaces. Endangered Species Update 10:13–19 Barnes BV, Zak DR, Denton SR, Spurr SH (1998) Forest ecology. Wiley, New York Barnes BV, Saeki I, Kitazawa A (2004) Occurrence and landscape ecology of a rare disjunct maple species, Acer pycnanthum, and comparison with Acer rubrum. Environ Rev 12:163–196 Bailey RG (1996) Ecosystem geography. Springer, Berlin Heidelberg New York Christensen NL, Bartuska AM, Brown JH, Carpenter S, D’Antonio C, Francis R, Franklin JF, MacMahon JA, Noss RF, Parsons DJ, Peterson CH, Turner MG, Woodmansee RG (1996) The report of the Ecological Society of America Committee on the scientific basis for ecosystem management. Ecol Appl 6:665–691 Environment Agency of Japan (2000) Threatened wildlife of Japan, red data book, 2nd edn., vol 8, vascular plants (in Japanese). Japan Wildlife Research Center, Tokyo Franklin JF (1993) Preserving biodiversity: species, ecosystems, or landscapes? Ecol Appl 3:202–205 Franklin JF, Spies TA, Van Pelt R, Carey AB, Thornburgh DA, Rae Berg D, Lindenmayer DB, Harmon ME, Keeton WS,

Shaw DC, Bible K, Chen J (2002) Disturbances and structural development of natural forest ecosystems with silvicultural implications, using Douglas-fir forests as an example. For Ecol Manage 155:399–423 Fujii S (2002) Achievements and problems of regional red data books. In: Yahara T, Kawakubo N, The Society for the Study of Species Biology (eds) Biology of conservation and restoration (in Japanese). Bun-ichi Sogo, Tokyo, pp 95–107 Gleason HA, Cronquist A (1991) Manual of vascular plants of northeastern United States and adjacent Canada, 2nd edn. New York Botanical Gardens, Bronx, New York Goto T (2002) Oone bog and regeneration of Japanese red maple. In: Hiroki S (ed) Ecology of Satoyama (suburban forest in Japan) (in Japanese). Nagoya University Press, Nagoya, pp 97–103 Hanai M, Katsura Y, Honma A (eds) (2003) Natural monuments of Japan (in Japanese). Kodansha, Tokyo Hirabayashi K, Takahashi H (1969) Ecological studies on Acer pycnanthum: flora and vegetation in the spontaneous places (in Japanese). Bull Bot Soc Nagano 2:1–16 Hiroki S (2002) Development of ecological studies and the ecology of Satoyama (suburban forests in Japan). In: Hiroki S (ed) Ecology of Satoyama (suburban forest in Japan) (in Japanese). Nagoya University Press, Nagoya, pp 1–7 Iida S, Nakashizuka T (1995) Forest fragmentation and its effect on species diversity in suburban coppice forests in Japan. For Ecol Manag 73:197–210 Inoue K (1996) Reproductive biology of Acer pycnanthum (Aceraceae). Bull Bot Soc Nagano 29:29–32 Japan association for star magnolia conservation (1996) Wild stand of shidekobushi (star magnolia) in Japan (in Japanese). Japan association for star magnolia conservation, Gifu Japanese red maple conservation group (2003) Report of the Japanese red maple conservation group activities in Nagano Prefecture, 1991–2002 (in Japanese). Japanese red maple conservation group, Iida Kobayashi T, Saito A, Hori Y (1999) Species diversity of the understory dominated by dwarf-bamboo Pleioblastus chino Makino in a secondary forest with different numbers of years after the last mowing. J Jpn Soc Reveget Tech 24:201–207 Koidzumi G (1912) On Acer pycnanthum K. Koch (in Japanese). Bot Mag 26:263–264 Kurata S (1973) Illustrated important forest trees of Japan, vol 4. Japan Forest Technical Association (ed), Chikyusha, Tokyo Makinouchi T (2001) Stratigraphy of the Tokai Group and evolutional process of the Lake Tokai sedimentary basin (in Japanese with English summary). Sci Rep Toyohashi Mus Nat Hist 11:33–39 Ministry of the Environment in Japan (2004) Red data book species information. Ministry of the Environment in Japan. Available via http://www.biodic.go.jp/rdb/rdb_f.html. Cited 5 July, 2004 Miyoshi M (1925) Plants in the three prefectures Gifu, Shiga, and Mie (in Japanese). In: Department of the Interior, natural monuments investigation report (in Japanese). Tokyo, pp 53–54 Miyoshi M (1926) Explanation of natural monuments (in Japanese). Toyamabo, Tokyo Nakura G (1915) Japanese red maple. Aichi For Rep 12, Appendix, Plants in Aichi 2:10–15 Nomura K (ed) (1914) Japanese red maple and its origin (in Japanese). Hananokikai, Shiga Ogata K (1965a) A dendrological study on the Japanese Aceraceae, with special reference to the geographical distribution. Bull Tokyo Univ For 60:1–99 Ogata K (1965b) On Acer pycnanthum K. Koch (in Japanese with English summary). J Geobot 13:102–109 Okada I (1999) Restoration and management of coppices in Japan. Ecol Restor 17(1&2):31–38 Ozaki K (1991) Late Miocene floras from the Seto group in Aichi and Gifu Prefectures. In: Bull Kanagawa Prefectural Museum, Natural Science, special issue: Late Miocene and Pliocene floras in central Honshu, Japan. Kanagawa Prefectural Museum, Yokohama, pp 83–100

147 Rowe JS (1961) The level-of-integration concept and ecology. Ecology 42:420–427 Rowe JS (1989) The importance of conserving systems. In: Hummel M (ed) Endangered spaces: the future for Canada’s wilderness. Key Porter Books, Toronto, pp 228–235 Rowe JS (1992) The ecosystem approach to forestland management. For Chron 68:222–224 Rowe JS (2002) Home place, essays on ecology. NeWest, Edmonton Rowe JS, Barnes BV (1994) Geo-ecosystems and bio-ecosystems. Ecol Soc Am Bull 75:40–41 Shiga Prefectural Government (2004) Scenery of Shiga, Japanese red maple (in Japanese). Available via http://www.pref.shiga.jp/ minwa/39/39-06.html. Cited 23 June, 2004 Shimizu T (1989) Aceraceae. In: Satake Y, Hara H, Watari S, Tominari T (eds) Wild flowers of Japan, woody plants II (in Japanese). Heibonsha, Tokyo, pp 7–18 Shimizu T, Uchida T (1993) Hybridization between North American Acer rubrum L., and Japanese A. pycnanthum K. Koch (Aceraceae). J Phytogeogr Taxon 41:63–69 Tanai T (1983) Revisions of tertiary Acer from East Asia. J Fac Sci, Hokkaido Univ, Ser IV 20:291–390 Tanai T (2001) Evolution of genus Acer. In: Kawano S (ed) World of plants, woody plants (in Japanese). Newton, Tokyo, pp 136–143 Ueda K (1989) Phytogeography of Tokai hilly land element I. Definition (in Japanese with English summary). Acta Phytotaxonom Geobot 40:190–202

Ueda K (1993) Low wetlands and plants growing in them. In: Ishii M, Ueda K, Shigematsu T (eds) Conserving nature in Satoyama (suburban forests in Japan) (in Japanese). Tsukiji-Shokan, Tokyo, pp 69–102 Ueda K (1994) The origin and evolution of the Tokai hilly land element. In: Okada H, Ueda K, Kadono Y (eds) Natural history of plants: evolutionary studies of diversity (in Japanese). Hokkaido University Press, Sapporo, pp 3–18 US Fish and Wildlife Service (2004) Threatened and endangered species system (TESS). Available via http://ecos.fws.gov/ tess_public/TeSSSpeciesReport. Cited 6 Sept, 2004 van Gelderen DM, de Jong PC, Oterdoom HJ (1994) Maples of the world. Timber, Portland, OR Walther H (1972) Studien u¨ber tertia¨re Acer Mitteleuropas. Abh des Staatl Museums fu¨r Mineral und Geol zu Dres 19:1– 309 Wolfe JA, Tanai T (1987) Systematics, phylogeny, and distribution of Acer (maples) in the Cenozoic of western North America. J Fac Sci, Hokkaido Univ, Ser IV 22:1–246 Walters RS, Yawney HW (1990) Acer rubrum L. Red maple. In: Burns RM, Honkala BH (eds) Silvics of North America, vol 2, hardwoods. USDA, Forest service of agriculture handbook 654, Washington, D.C., pp 60–69 Yokouchi I (1962) Distribution of Japanese red maple in the Shinano district (in Japanese). Nagano-rinyuu Nov–Dec:22– 24