TROPICS Vol. 16 (3) Issued May 31, 2007

Effects of an alien shrub species, Leucaena leucocephala, on establishment of native mid-successional tree species after disturbance in the national park in the Chichijima island, a subtropical oceanic island

＊ Kenji HATA , Jun-Ichirou SUZUKI and Naoki KACHI

Department of Biological Sciences, Graduate School of Science, Tokyo Metropolitan University, Minami-Osawa 1−1, Hachioji, Tokyo, 192−0397, Japan ＊Corresponding author: Kenji HATA. Tel; +81−426−77−2585, Fax; +81−426−77−2559, E-mail: [email protected]

ABSTRACT Effects of an invasion of an alien & Duggin, 1997), which would change successional shrub species, Leucaena leucocephala , were pathways of native plants in an invaded habitat. The investigated on subsequent establishment of a successional pathways of native species in some tropical native mid-successional wooden species, Schima and subtropical oceanic islands were affected by an mertensiana at early-successional stages after alien shrub species, Leucaena leucocephala (L.) de disturbance in a subtropical oceanic island, Wit (Leguminosae). The species invaded and formed Chichijima in Japan. Changes in basal areas, dense monotypic thickets in disturbed areas in many densities and size distribution of forests at a site oceanic islands, which should have prevented seedlings dominated by L. leucocephala were compared with of woody species and understory herbaceous species those at a site dominated by native shrub species, from germination and/or growth under canopies of L. Trema orientalis at early-successional stages. leucocephala (e.g. Decker 1992, Mueller-Dombois and Effects of L. leucocephala on germination of seeds Fosberg 1998, Yamamura et al. 1999). and growth of seedlings of S. mertensiana were Germination or growth of some plant species in a quantified at the sites. There were few recruited subtropical region were inhibited by aqueous extracts seedlings of S. mertensiana and they did not grow of plant tissues of L. leucocephala under experimental at the site dominated by L. leucocephala. On the conditions (Chou & Kuo, 1986). These allelopathic effects other hand, there were a few recruited seedlings of L. leucocephala could prevent seedlings of endemic and within a 1 m x 1 m area and they positively grew other native plants from establishment in oceanic islands, at the site dominated by T. orientalis. Germination which inevitably influences the native successional rates of seeds and growth rates of seedlings pathway. This process should be quantitatively described of S. mertensiana at the site dominated by L. for conservation of endemic plants in oceanic islands. leucocephala were lower than those at the site Effects of invasion of L. leucocephala on native dominated by T. orientalis. Germination of seeds successional pathways were described by comparison and growth of seedlings of S. mertensiana were of structure of the secondary forests between forests inhibited by L. leucocephala at the disturbed site, dominated by L. leucocephala and those by native species which potentially changed an early successional in the Bonin Islands. In addition, histories of vegetation pathway of the plant community. types of the forests were also analyzed based on aerial photographs (Yoshida & Oka, 2000). There were Key words: invasive plants, Schima mertensiana, differences in the structures and successional pathways Bonin Islands, seed germination, seedling growth, of the forests (Yoshida & Oka, 2000). However, we still Trema orientalis do not know quantitative effects of the invasion of L. leucocephala on establishment of native plants at mid- or late-successional stages. For this purpose, it is necessary INTRODUCTION to compare establishment and growth of native plants at Invasion of an alien plant species often prevents native sites at which L. leucocephala invaded or not. plant species (Myers & Bazely, 2003) from establishment It is hypothesized that native plants of mid- or late- due to shading (Weihe & Neely, 1997), litter accumulation successional species in subtropical oceanic islands would (Walker & Vitousek, 1991) and allelopathy (Gentle be prevented from establishment in a forest dominated 284 Kenji HATA, Jun-Ichirou SUZUKI and Naoki KACHI by L. leucocephala at early successional stages because at the both sites. Forest floors of the study sites were of allelopathic effects of L. leucocephala (Chou & Kuo, covered with herbaceous species, and the most dominant 1986). Based on the hypothesis, we tested the prediction species was Stachytarpheta jamaicensis (L.) Vahl that germination of seeds and growth of seedlings (Verbenaceae). of native mid-successional species under plants of L. leucocephala are lower than those under plants of native Measurements of forests dominated by L. species. leucocephala or T. orientalis In order to test the prediction, firstly, we compared A 10 m × 10 m plot was established at each site in July changes in biomass, densities and size distribution of 2001. The areas from which the broadcasting towers dominant species in a forest dominated by L. leucocephala were removed were so limited that only one plot was with those in a forest dominated by native species at established at the site. All the individuals of woody early-successional stages for three years in the Bonin species in the plots were tagged, and their diameters at (Ogasawara) Islands, subtropical islands in the northern ground level were measured. Subsequent measurements Pacific. Secondly, we compared germination rates of a were carried out in July 2002 and September 2003. mid-successional species of a native tree and growth rates of its seedlings in the forest dominated by L. Field experiments leucocephala with those in the forest dominated by a A field experiment was carried out in order to test native species appeared at early-successional stages by whether established plants of L. leucocephala prevented field experiments. plants of S. mertensiana from germination and growth. Five 1 m × 1 m plots were established under canopies of L. leucocephala outside of the 10 m × 10 m plot at the site MATERIALS AND METHODS dominated by L. leucocephala and other five 1 m × 1 m Plant species plots under canopies of T. orientalis outside of the 10 m × A shrub species, L. leucocephala, was introduced to the 10 m plot at the site dominated by T. orientalis. Each 1 m Bonin Islands in 1862 (Funakoshi, 1989) and spread into × 1 m plot was located at least 1 m away each other. abandoned areas (Shimizu, 1989). A native shrub species, These five 1 m × 1 m plots were divided into three Trema orientalis Blume (Ulmaceae) appears at early categories: three 1 m × 1 m plots of the five 1 m × 1 m stages in a secondary succession in the Bonin Islands plots were allocated to a seedling transplant experiment. (Shimizu, 1989). A wooden species, Schima mertensiana In one of the rest two 1 m × 1 m plots, germinated (Sieb. et Zucc.) Koidez (Theaceae), is endemic to seedlings were counted. Total canopy openness was the Bonin Islands, and dominates at middle stages in measured in the rest 1 m × 1 m plots. secondary succession (Shimizu, 1989). In May 2002, the seedling transplant experiment was conducted. Sixty seedlings of S. mertensiana with Study site ca. 10 cm in height and ca. 0.2 cm in diameter at ground This study was conducted at two sites in secondary level were collected near the 10 m × 10 m plots but forests at Yoakedaira (27˚05 ′ N, 142˚12 ′ E, 220 m above outside of the 1 m × 1 m plots. Ten of the seedlings were sea level) in the national park in the largest island of the transplanted into each of the 1 m × 1 m plots after their Bonin Islands, Chichijima. The ground at the study sites diameters at ground level and heights were measured. (ca. 400 m2) were bared by the removal of broadcasting Each of the seedlings was planted 20 cm away from the towers in 1999. Surface soils and vegetation around the others. All transplanted seedlings were harvested and towers were cleared. One of the study sites was invaded dried at 70 ˚C for 72 h for weighting at the end of the and dominated by an alien species, L. leucocephala, and transplant experiment in May 2003. another site by a native species, T. orientalis after 1999. The initial biomass of the transplanted seedlings was The study sites were surrounded by the secondary estimated based on the relationship between diameters at forest dominated by S. mertensiana (Appendix 1). Many ground level, heights, and dry weights. The relationship mature trees of S. mertensiana could be homogeneously was determined by the 24 seedlings of S. mertensiana dispersed in the secondary forests. Indeed, dispersed collected near the 10 m × 10 m plots but outside of the 1 seeds of S. mertensiana were often observed at the m × 1 m plots. The regression equation was; study sites (personal observation). Therefore, sufficient the initial dry weight (g) = 0.23116 + 1.2608 (diameter numbers of seeds of S. mertensiana could be dispersed at ground level (cm))2 x height (cm), r2 = 0.667, p < 0.0001. Effects of L. leucocephala on S. mertensiana in an oceanic island 285

One of the six 1 m × 1 m plots was abandoned openness of each point. because nine transplanted seedlings died by June 2002. A 1 m × 1 m plot, therefore, was newly established and ten Data analysis seedlings of S. mertensiana were transplanted in the plot Effects of existences of S. jamaicensis on germination of in June 2002. seeds and growth of seedlings of S. mertensiana were not Two hundred seeds that were collected in a detected (data not shown). Therefore, the effects were secondary forest around the study sites were sown in not considered in the further analyses. November 2002 into a pot with 21 cm in diameter and All statistical analyses were carried out using the 17 cm in depth. Three of the pots with seeds were set in software, R 2.0.1 (http://www.r-project.org/). Differences the 1 m × 1 m plot at each of the study sites. Soil for the in size increments of the seedlings in the transplant germination experiment was taken at the site at which the experiment were analyzed by a nested one-way analysis pots were set and seeds in the soil were eliminated before of variance (ANOVA) (Zar, 1999). The independent the experiment. Numbers of seedlings were counted in variables were sites (L. leucocephala-dominated site and T. May 2003. The ungerminated seeds were collected and orientalis-dominated site) and blocks (three replicates of checked whether they were alive or dead in May 2003. a 1 m × 1 m plot). The sites were fixed factors. The blocks The seed germination experiment was conducted in pots were random factors and nested with the fixed factors. because there could be seeds of S. mertensiana in the soil Differences in the results of the germination experiment at the sites. were analyzed by t-test. The germination rates of seeds Total canopy openness was determined based on were arcsine transformed. T-test was also conducted to hemispherical photographs in order to estimate light detect differences in values of the total canopy openness exposure in a 1 m × 1 m plot. Hemispherical photographs after arcsine-transformed. were taken at 0.1 m above ground in the 1 m × 1 m plot. The photographs were taken in five points in each plot at around noon on cloudy days in July 2004 (Fisheye RESULTS Converter FC-E8 0.21x, Nikon, Tokyo, Japan and Nikon Changes in basal areas and densities of forests Coolpix 880, Nikon, Tokyo, Japan). HemiView 2.1 Canopy dominated by L. leucocephala or T. orientalis Analysis Software (Delta-T Devices, Burwell, Cambridge, Basal areas of all woody species increased at the two sites UK) was used to calculate the values of total canopy during three years of this study (Table 1). The basal area

‒ ‒ Table 1. (a) Basal areas (cm2 100 m 2) and (b) numbers (100 m 2) of woody species in the 10 m x 10 m plots. (a) Basal areas＊ Site dominated by Leucaena leucocephala Site dominated by Trema orientalis Species 2001 2002 2003 2001 2002 2003 Leucaena lecocephala 352.3 746.3 815.0 3.7 6.7 10.4 Trema orientalis 82.1 197.3 316.0 140.0 239.0 208.6 Schima mertensiana < 0.1 0.1 0.4 21.1 85.0 268.7 Other species 5.5 27.9 98.5 6.7 43.9 316.2 Total 439.9 971.6 1229.9 171.5 374.6 803.9

(b) Numbers Site dominated by Leucaena leucocephala Site dominated by Trema orientalis Species 2001 2002 2003 2001 2002 2003 Leucaena lecocephala 312 322 324 4 13 24 Trema orientalis 28 14 10 108 72 43 Schima mertensiana 1 3 3 381 767 822 Other speices 21 19 21 37 91 114 Total 362 358 358 530 943 1003 ＊Basal areas of woody species were calculated from diameters at above ground of woody species. Fig. 1 286 Kenji HATA, Jun-Ichirou SUZUKI and Naoki KACHI

(a) Leucaena leucocephala at the site dominated by L. leucocephala 150 2001 2002 2003 100

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1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 Diameter at ground level (cm) Fig. 1. Frequency distributions of diameters at ground level in the 10 m × 10 m plots for (a) Leucaena leucocephala, (b) Schima mertensiana, (c) Trema orientalis and (d) S. mertensiana for three years. (a), (b): the site dominated by L. leucocephala; (c), (d): the site dominated by T. orientalis. Open bars indicated alive plants in the current year. Shaded bars indicated recruited plants in the current year. Closed bars indicated that plants died in the current year. Effects of L. leucocephala on S. mertensiana in an oceanic island 287 of L. leucocephala at the site dominated by L. leucocephala in 2003 was about 2.8 times as large as that in 2001, while Field experiments percentages of relative dominance of L. leucocephala In total, 20 transplanted seedlings of S. mertensiana under decreased from 80.0% to 66.3% in three years. Densities canopies of L. leucocephala survived and 26 transplanted of all woody species hardly changed for three years at seedlings under canopies of T. orientalis survived at the the site dominated by L. leucocephala (Table 1). The end of the experiment. There was a significant difference percentages of number of plants of L. leucocephala in size increments of the transplanted seedlings of S. against number of all woody species at the site were mertensiana between two sites (nested One-way ANOVA, approximately 90% throughout three years. Few plants of F(1, 2) = 9.39, p < 0.001). A mean of size increments of the S. mertensiana were observed at the site for three years. seedlings at the site dominated by L. leucocephala was Basal area of T. orientalis increased between 2001 0.08 g year−1 (± 0.07 s.e.) and that at the site dominated and 2002 and slightly decreased from 2002 to 2003 at the by T. orientalis 0.87 g year−1 (± 0.19 s.e.). There were no site dominated by T. orientalis (Table 1). Percentages of significant effects of blocks (F(2, 42) = 1.41, p = 0.25). basal areas of T. orientalis decreased from 81.6% to 26.0% There was a marginal difference in germination of in three years. Number of all woody species increased for seeds of S. mertensiana between sites (t-test, p = 0.057) three years at the site dominated by T. orientalis (Table and ungerminated seeds in the experimental period had 1), while number of plants of T. orientalis decreased for died in May 2003. The rate of germination at the site three years. The percentages of relative dominance of T. dominated by L. leucocephala was 1.3% ( ± 0.9 s.e.) and orientalis also decreased from 20.4% to 4.3% in the same that at the site dominated by T. orientalis 20.9% (± 5.2 s.e). period. In spite of the decrease of T. orientalis, substantial A mean of total canopy openness in the 1 m x 1 m increases in basal areas and in number of trees of S. plots under canopies of L. leucocephala was 0.24 (± 0.003 mertensiana were observed and percentages of basal s.e.) and that under canopies of T. orientalis was 0.22 (± area and relative dominance of S. mertensiana increased 0.015 s.e.). There was not significant difference in the from 12.3% to 33.4% and from 71.9% to 82.0% at the site total canopy openness between the sites (t-test, p = 0.18). dominated by T. orientalis in three years.

Changes in size distributions of forests dominated DISCUSSION by L. leucocephala or T. orientalis Lack of replacement by middle- or late-successional Size distribution of L. leucocephala always exhibited native woody species after invasion of L. leucocephala L-shaped distribution at the site dominated by L. (Yoshida & Oka, 2000) could be due to the prevention leucocephala. Shape of the size distribution changed for of establishment of seedlings of native species. Actually, three years (Two-sample Kolmogorov-Smirnov test, D establishment of seedlings of S. mertensiana hardly = 0.16, p < 0.001) due to frequent recruitment and high occurred at the sites dominated by L. leucocephala and mortality of small-sized plants (Fig. 1a). Few plants of S. there were, therefore, a very few plants of S. mertensiana mertensiana recruited and grew at the site dominated by at the site. L. leucocephala for three years (Fig. 1b). Establishment and growth of the seedlings of S. Size distribution of T. orientalis was weakly skewed mertensiana were observed at the site dominated by T. in 2001, and it was bell-shaped one in 2003 at the site orientalis. Basal areas and densities of S. mertensiana dominated by T. orientalis (Two-sample Kolmogorov- increased at the site dominated by T. orientalis, which Smirnov test, D = 0.56, p < 0.0001) due to few recruited indicated that the T. orientalis could be replaced by S. plants of T. orientalis for three years (Fig. 1c). Diameters mertensiana. Changes in size distribution of T. orientalis at ground level of all plants of S. mertensiana were at the site dominated by T. orientalis also suggested smaller than 0.5 cm in 2001 (Fig. 1d). In 2002, diameters the replacement. This result was consistent with the at ground level of 147 plants of S. mertensiana were results of secondary succession in the Chichijima island larger than 0.5 cm and there were 401 recruited plants. (Shimizu, 2005). Diameters at ground level of 103 plants were larger than There were differences in establishment and 1 cm and there were 94 recruited plants in 2003. As the growth of S. mertensiana between the two sites although results, shape of size distribution of S. mertensiana was there could be sufficient seed rains of S. mertensiana weakly L-shaped one in 2003 (Two-sample Kolmogorov- at the sites. The lack of establishment and growth of S. Smirnov test, D = 0.47, p < 0.0001). mertensiana at the site dominated by L. leucocephala 288 Kenji HATA, Jun-Ichirou SUZUKI and Naoki KACHI might change the successional pathways in the forests Yoshikazu Shimizu kindly provided useful information because S. mertensiana is one of the most dominant about the disturbance at our study sites. Takaya Yasui, species in secondary forests at mid- or late-successional Fumiko Yumura, Atsushi Tanaka, Hajime Tomimatsu, stages in the Chichijima island (Shimizu & Tabata, 1991). Yuriko Ichikawa, Ryoji Nakamura, Akihiro Nojima, The lack of establishment of S. mertensiana would Kenta Watanabe and Hoho Yamamoto helped us in the be caused by inhibition of seed germination and seedling field research. Elizabeth Zielinska edited the English growth of S. mertensiana by existence of L. leucocephala. of the manuscript. Two anonymous referees made There were no differences in the total canopy openness numerous valuable comments that improved our original of understory between two sites, which suggested that manuscript. The study was financially supported by a light conditions of the two sites were comparable. At the Grand-in-Aid for Scientific Research of Japan Society both sites, the amounts of available light in the 1 m x 1 for Science Promotion and the Fund for the Global m plots would be large enough for germination of seeds Environmental Research Program of the Ministry of the and growth of seedlings of S. mertensiana, because Environment of Japan (Grand No. F-51). values of the total canopy openness in the 1 m x 1 m plots dominated by plants of L. leucocephala were equivalent to those under forest gaps (e.g. Silbernagel & Moeur, 2001). REFERENCES Seed germination and seedling growth of S. Chou, C-H. & Kuo, Y−L. 1986. Allelopathic research of mertensiana would be inhibited by the allelopathic subtropical vegetation in Taiwan III. Allelopathic effects of L leucocephala. Indeed, there are few exclusion of understory by Leucaena leucocephala understorey plants under L. leucocephala, which is (Lam.) de Wit. Journal of Chemical Ecology, 12: caused by phytotoxic chemicals including fresh leaves, 1431−1448. litter and seeds of L. leucocephala (Chou & Kuo, 1986). Decker, B.G. 1992. Secondary plant cover on upland The allelopathic effects of L. leucocephala may play an slopes, Marquesas Islands, French Polynesia. Atoll important role to prevent plants of native species from a Research Bulletin, 363: 1−36. subsequent establishment. Funakoshi, M. 1989. Formation of Leucaena leucocephala Our results demonstrated that invasions of alien forests in the Ogasawara (Bonin) Islands [in plants at early successional stages after disturbance by Japanese]. Annual Report of Ogasawara Research, human activities could prevent from establishment of 13: 59−72. native plants of mid- or late-successional species. Forests Gentle, C.B. & Duggin, J.A. 1997. Allelopathy as a in the Ogasawara National Park in the Chichijima island competitive strategy in persistent thickets of are often subject to disturbances, which would bring Lantana camara L. in three Australian forest about an invasion of L. leucocephala. The invasion of L. communities. Plant Ecology, 132: 85−95. leucocephala could be crucial problems for conservation Mueller−Dombois, D. & Fosberg, F.D. 1998. Vegetation of of endemic species in the island. Unfortunately, the tropical pacific islands. Springer, New York. there were no replications of our study because the Myers, J.H. & Bazely, D.R. 2003. Ecology and Control forests including the study sites were situated within of Introduced Plants. Cambridge University press, the protected area in the Ogasawara National Park. Cambridge, United Kingdom. Therefore, we could not disturb the forests in order to Shimizu, Y. 1989. Ecological characteristics of forest create additional bare ground. The results, however, can vegetation on oceanic islands, Ogasawara [in provide useful information to restore native forests of the Japanese]. In: Vegetation of Japan: Okinawa and Bonin Islands after disturbances. Ogasawara (ed. Miyawaki, A.), pp. 159−203. Shibundo, Tokyo, Japan. ACKNOWLEGEMENTS The Environmental Shimizu, Y. 2005. A vegetation change during a 20-year Agency and the Department of National Forests in the period following two continuous disturbances Ogasawara Islands allowed us to conduct this study at (mass−dieback of pine trees and typhoon damage) Chichijima Island. The study plots were established in the Pinus-Schima secondary forest on Chichijima by Takaya Yasui, the president of Ogasawara Wildlife in the Ogasawara (Bonin) Islands: which won, Research Society, who kindly gave us to use these advanced saplings or new seedlings? Ecological plots. We are grateful to Keiichiro Yoshida for valuable Research, 20: 708−725. discussion of the manuscript. Fuyuo Nobushima and Shimizu, Y. & Tabata, H. 1991. Forest structures, Effects of L. leucocephala on S. mertensiana in an oceanic island 289

composition, and distribution on a pacific island, with reference to ecological release and speciation. Pacific Science, 45: 28−49 Silbernagel, J. & Moeur, M. 2001. Modeling canopy openness and understory gap patterns based on image analysis and mapped tree data. Forest Ecology and Management, 149: 217−233. Walker, L.R. & Vitousek, P.M. 1991. An invader alters germination and growth of a native dominant tree in , Hawai i. Ecology, 72: 1449−1455. Weihe, P.E. & Neely, R.K. 1997. The effects of shading on competition between purple loosestrife and broad− leaved cattail. Aquatic Botany, 59: 127−138. Yamamura, Y., Fujita K., Sudo, S., Kimura, W., Honma, S., Takahashi, T., Ishida, A., Nakano, T., Funakoshi, M. & Kimura, M. 1999. Regeneration of Leucaena leucocephala forests in Ogasawara (Bonin) Islands [in Japanese]. Japanese Journal of Conservation Ecology, 4: 152−166. Yoshida, K. & Oka, S. 2000. Impact of biological invasion of Leucaena leucocephala on successional pathway and species diversity of secondary forest on Hahajima Island, Ogasawara (Bonin) Island, northwestern Pacific [in Japanese with English abstract]. Japanese Journal of Ecology, 50: 111−119. Zar, J.H. 1999. Biostatistical Analysis, 4th edn. Prentice Hall, New Jersey.

Received 31st Oct. 2006 Accepted 25th Dec. 2006 290 Kenji HATA, Jun-Ichirou SUZUKI and Naoki KACHI 0 . 3 0 . 8 6 . 7 4 . 2 0 . 1 9 . 3 . 4 3 . 2 0 . 2 0 . 3 2 . 0 . 1 7 . 8 3 . 8 2 . 5 < 0 . 1 < 0 . 1 < 0 . 1 < 0 . 1 < 0 . 1 < 0 . 1 (%) 54 . 5 ＊ 0 . 2 0 . 5 4 . 2 . 8 0 . 1 6 . 2 . 3 2 . 0 . 1 0 . 2 1 . 5 0 . 1 5 . 2 2 . 5 1 . 7 ) < 0 . 1 < 0 . 1 < 0 . 1 < 0 . 1 < 0 . 1 < 0 . 1 66 . 6 ‒ 1 36 . 3 ha 2 (m Basal area 5 . 0 . 1 0 . 7 3 . 7 0 . 8 0 . 1 5 . 1 1 . 9 2 . 7 1 . 0 2 . 4 2 . 1 . 2 0 . 5 4 . 1 1 . 4 5 . 4 0 . 1 0 . 1 10 . 0 13 . 5 (%) 37 . 4 8 . 3 8 . 3 8 . 3 8 . 3 Trema orientalis Trema ) 50 . 0 58 . 3 75 . 0 83 . 3 33 . 3 ‒ 1 391 . 7 266 . 7 366 . 7 133 . 3 191 . 7 716 . 7 966 . 7 175 . 0 158 . 3 291 . 7 100 . 0 383 . 3 by 7150 . 0 (ha 2675 . 0 Density ) 1 . 0 6 . 0 7 . 0 1 . 0 9 . 0 4 . 0 1 . 0 1 . 0 ‒ 1 Secondary forest around the site dominated 47 . 0 32 . 0 44 . 0 16 . 0 23 . 0 86 . 0 21 . 0 19 . 0 10 . 0 35 . 0 12 . 0 46 . 0 116 . 0 858 . 0 321 . 0 ( 0 . 12 ha No. of trees 5 . 0 0 . 3 2 . 4 0 . 2 2 . 4 2 . 7 0 . 1 1 . 3 0 . 5 0 . 1 9 . 7 3 . 7 1 . 2 0 . 2 0 . 4 1 . 2 . 6 3 . 4 2 . 3 0 . 2 1 . 0 < 0 . 1 < 0 . 1 < 0 . 1 < 0 . 1 < 0 . 1 < 0 . 1 (%) 59 . 1 ＊ 3 . 0 . 2 1 . 6 0 . 1 1 . 6 1 . 8 0 . 8 0 . 3 0 . 1 6 . 3 2 . 4 0 . 8 0 . 1 0 . 3 0 . 7 1 . 7 2 . 1 . 5 0 . 2 0 . 7 ) < 0 . 1 < 0 . 1 < 0 . 1 < 0 . 1 < 0 . 1 < 0 . 1 < 0 . 1 65 . 5 ‒ 1 38 . 7 ha 2 (m Basal area 1 . 0 0 . 1 0 . 1 2 . 4 0 . 4 0 . 5 1 . 0 0 . 4 0 . 1 0 . 5 2 . 5 1 . 2 . 3 1 . 9 7 . 4 7 . 4 0 . 5 3 . 9 0 . 9 0 . 4 3 . 6 0 . 5 5 . 0 0 . 5 0 . 8 0 . 5 (%) 13 . 6 40 . 7 8 . 3 8 . 3 8 . 3 66 . 7 25 . 0 33 . 3 66 . 7 25 . 0 33 . 3 75 . 0 33 . 3 58 . 3 25 . 0 33 . 3 33 . 3 50 . 0 33 . 3 891 . 7 158 . 3 166 . 7 150 . 0 125 . 0 483 . 3 483 . 3 258 . 3 233 . 3 325 . 0 6558 . 3 Leucaena leucocephala ) ‒ 1 2666 . 7 by Density (ha ) 8 . 0 1 . 0 1 . 0 3 . 0 4 . 0 8 . 0 3 . 0 1 . 0 4 . 0 9 . 0 4 . 0 7 . 0 3 . 0 4 . 0 4 . 0 6 . 0 4 . 0 ‒ 1 Secondary forest around the site dominated 19 . 0 20 . 0 18 . 0 15 . 0 58 . 0 58 . 0 31 . 0 28 . 0 39 . 0 107 . 0 787 . 0 320 . 0 ( 0 . 12 ha No. of trees spp. Basal areas were calculated from diameters at breast height. Appendix 1 . Plant species composition of secondary forests around the study sites in which 10 m x plots were established. Species Ardesia sieboldii Bischofia javanica Callicarpa subpubescens Casuarina equisetifolia Cinnamomum japonicum Cinnamomum pseudo-pedunculatum Cyathea mertensiana Drypetes integerrima Elaeocarpus photiniifolius Ficus nishimurae Ficus Freycinetia boninensis Hernandia nympheaeifolia Hibiscus glaber Ilex mertensii Ligustrum micranthum Livistona chinensis Machilus kobu Neolitsea aurata Ochrosia nakaiana Osmanthus insularis Pandanus boninensis Photinia wrightiana Pinus luchuensis Porteria obovata Psidium cattleianum Rhaphiolepis wrightiana Schima mertensiana Syzygium cleyeraefolium orienrtalisTrema Zanthoxylum ailanthoides unknown total ＊