Broad-leaf species composition in Cryptomeria japonica plantations with respect to distance from natural forest

Forest Ecology and Management 259 (2010) 2133–2140

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Broad-leaf species composition in Cryptomeria japonica plantations with respect to distance from natural forest Regielene S. Gonzales ∗ , Tohru Nakashizuka Graduate School of Life Sciences, Tohoku University, Aobayama, Aoba-ku, Sendai 980-8578, Japan

a r t i c l e

i n f o

Article history: Received 21 December 2009 Received in revised form 18 February 2010 Accepted 26 February 2010 Keywords: Conifer plantation Functional traits Recruitment limitation Seed size Species diversity

a b s t r a c t To address the pressing need to evaluate how conifer plantations can serve biodiversity functions in addition to other economic and social roles they play, we assessed the diversity of broad-leaf seedlings and saplings in Cryptomeria japonica plantations in Ogawa, Ibaraki Prefecture, Japan at increasing distances (0–1000 m) from old growth natural forest edge. For saplings, there was no overall significant trend in the frequency, species richness, and Shannon index with respect to distance. Seedlings on the other hand showed a decrease in frequency and species richness with increasing distance from the old growth forest, implying that should recruitment limitation occur in the plantations, it will be stronger at the seed-toseedling transition than at the seedling-to-sapling transition. Assigning species into groups based on functional traits that are associated with recruitment and regeneration was more revealing. Relative frequency of species that are moderately shade-tolerant, are shrubs, have small seeds, and are frugivoredispersed increased in the plantations. In comparison, species that are tall trees, have large seeds and are gravity-dispersed decreased in the plantations. Multi-trait analysis showed that propagule size was the trait that could best explain the difference in the distribution of broad-leaf species in the plantations. Based on our results, we suggest to policy-makers that plantation sizes be kept to within a few hundred meters wide, and should ideally be within dispersal distance of species from natural forests that could potentially be seed sources of broad-leaf species. Otherwise, steps must be taken to drive succession such that potentially recruitment-limited species may be able to overcome barriers to regeneration. © 2010 Elsevier B.V. All rights reserved.

1. Introduction In light of the global increase of plantation areas against the decrease of natural forest cover, the biodiversity conservation value of plantations has become an increasingly important topic of discussion recently (Brockerhoff et al., 2008). Plantations are mainly for timber production, but the need to manage them in an ecologically sustainable way so they can also serve other functions has been recognized (Brockerhoff et al., 2008; Franklin et al., 1986; Hansen et al., 1991). In Japan, approximately 40% of total forest cover is plantations (Japan Forestry Agency, 2004). Many plantations are even-aged monocultures that have low value for wildlife (Hansen et al., 1991; Nagaike, 2000) and present problems such as soil surface runoff (Kajihara et al., 1999), snow damage (Masaki et al., 2004), high soil acidity (Yamashita et al., 2004), and susceptibility to pests (Kamata, 2002). As such, although different plantation management approaches have been undertaken, the consensus is that they should evaluate, conserve, and enhance species diversity and composition (Kodani, 2006; Masaki et al.,

∗ Corresponding author. Tel.: +81 22 7956698; fax: +81 22 7956699. E-mail address: [email protected] (R.S. Gonzales). 0378-1127/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.foreco.2010.02.028

2004; Nagaike, 2000; Sakai et al., 2006; Utsugi et al., 2006; Yoshida et al., 2005). Studies have shown that plant species diversity in conifer plantations is affected by stand age, management practices, and distance from natural forest that acts as seed source (Battles et al., 2001; Kodani, 2006; Sakai et al., 2006; Utsugi et al., 2006). Distance from the edge of a natural forest affects dispersal of seeds in a way that typically follows a smooth concave decline, and this in turn impacts the resulting diversity of the communities that the seeds reach (Cousens et al., 2008). However, it is not as simple as stating that species diversity in plantations increases or decreases with respect to distance, as distance can affect different species in different ways. In the Tohoku region of Japan for example, although hardwood species abundance and diversity decreased with increasing distance into unthinned Cryptomeria japonica plantation interior, exceptions were observed for certain small, wind-dispersed species (Utsugi et al., 2006). In another study, broad-leaf shrub species density decreased with increasing distance into maturing plantation gap stands, but other life forms such as small and tall trees did not show any significant trend (Kodani, 2006). It is clear that functional traits of species can determine the composition of a habitat (Meers et al., 2008). There is therefore a need to define the functional traits of species to get a more

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meaningful insight as to how the diversity of species in plantations changes with respect to distance from natural forest (Ito et al., 2003; Kodani, 2006; McIntyre et al., 1999). In order to achieve the goal of enhancing hardwood diversity in conifer plantations, understanding the factors that affect recruitment and regeneration is necessary (Götmark et al., 2005; Senbeta et al., 2002; Utsugi et al., 2006; Yamagawa and Ito, 2006; Zerbe, 2002). Traits that influence the recruitment or regeneration of species, particularly at earlier stages, are of interest. Species experience the most drastic demographic changes during early seedling stages, hence these stages disproportionately affect community composition (Nakashizuka, 2001). Traits that are associated with recruitment and regeneration include seed size, dispersal agent, shade tolerance, and maximum plant height. Seed size affects the seed production, dispersal and germination probabilities and seedling survival of species (Gross, 1984; Haig and Westoby, 1990; Jackson, 1981; Tanaka and Kominami, 2002); the type of dispersal agent dictates the distance that seeds reach and the seed rain patterns they produce (Cousens et al., 2008; McEuen and Curran, 2004); interspecific shade tolerance of species drives forest succession and affects seedling and sapling growth and survival rates (Grubb et al., 1996; Kobe et al., 1995; Walters et al., 1993); and plant height is related to shade tolerance and growth rates (Lei and Lechowicz, 1990; Thomas, 1996). We set out to study conifer plantations to answer the following questions: (1) How are broad-leaf species composition and diversity affected in plantations with respect to distance from natural forest? (2) What are the functional traits of species that may be potentially recruitment-limited in plantations? 2. Materials and methods

Fig. 1. Location map of transects taken at sites B (squares) and C (circles). The dark line from north to south is a narrow dirt road. About 20 m to the left of this road runs a strip of old growth broad-leaf forest while to the right are C. japonica plantations. The gray areas are fragments of natural broad-leaf forests.

areas of these plantations, but many of these were cleared due to human activities such as cattle-grazing and charcoal production. After World War II, pastures and meadows were converted into conifer plantations or were abandoned and developed into secondary forests (Suzuki, 2002).

2.1. Study site 2.2. Floral census The study sites, located in Ibaraki Prefecture, central Japan, are within the vicinity of the Ogawa Forest Reserve (OFR) (36◦ 56 N, 140◦ 35 E, 610–660 m a.s.l.), an area that is part of a national forest and has been a protected zone since 1987 (Nakashizuka and Matsumoto, 2002). The mean annual air temperature is 10.7 ◦ C and the mean annual precipitation is 1910 mm. The forests around OFR are a mosaic of different vegetation types, with only a handful of old growth or secondary deciduous broad-leaf forests remaining that are mainly dominated by Fagus crenata, F. japonica, Carpinus laxiflora, and Quercus serrata. Large plantations of Chamaecyparis obtusa and Cryptomeria japonica are sprawled all over the landscape. We chose three study sites (A, B and C), each having an old growth broad-leaf forest adjacent to C. japonica plantations, and all occurring on gently sloping topography (Fig. 1). We sampled transects at four distances in each study site: 0 m (inside natural forest), and 10–15 m, 100–200 m, and 300–1000 m from the edge of the old growth forest (designated as ‘old growth’, ‘near plantation’, ‘intermediate plantation’, and ‘far plantation’, respectively). The old growth forests had a mean DBH of 46.5 cm, while the conifer plantations had 76.0 cm, 66.4 cm, and 59.3 cm, respectively (including C. japonica trees). Average stem density of adult trees was 1376 stems ha−1 in the old growth forests, 1000 stems ha−1 in the near, 1300 stems ha−1 in the intermediate, and 1473 stems ha−1 in the far plantations. About 96% of the basal area of mature trees in the plantations studied was made up of C. japonica, while the remaining percentage consisted of C. crenata, Q. serrata, Prunus spp., and a few other broad-leaf species. Mean light intensity was measured in April–May 2009 in sites B and C using a pendant type light data logger. The average light intensity in the old growth forest during this time was 18,038 lx compared to only 9115 in the plantations. The conifer plantations studied ranged from about 30 to 40 years old. As of 100 years ago, natural broad-leaf forests still covered the

The transects we sampled in each plot was 100 m long and 10 m wide, and was divided into 5 m × 5 m quadrats, for a total of 40 quadrats per transect. In each quadrat we recorded the presence of saplings (<2 m high) of species of woody trees and shrubs. For the seedlings of these species, the presence was sampled from a 1 m × 1 m sub-quadrat at the center of each quadrat. Current year seedlings were excluded from the sampling. 2.3. Data analyses The frequency, species richness, and Shannon’s index (H ) of the seedlings and saplings in the 12 transects were subjected to linear regression to test the changes in the species abundance and composition with increasing distance from the old growth forest. Shannon’s index was computed using the following formula: H = −pi ln pi , where pi is the number of individuals of species i divided by the total number of all individuals. To see how the transects grouped together based on similarity, Jaccard’s similarity index (J) was calculated for the seedling and sapling species in each transect and was then subjected to group average cluster analysis on PC-ORD for Widows v.5.10. The formula used for calculating J between two plots was: J = rab /(ra + rb + rab ), where ra is the number of species occurring only in plot a; rb is the number of species occurring only in plot b; rab is the number of species occurring in both plots. Seedling and sapling species were classified into types based on the following functional traits: seed-dispersal type, propagule size, shade tolerance, and maximum plant size. Disperser types were classified into frugivore, gravity, wind, or others; propagule sizes were small (length ≤ 3.2 mm), medium (>3.2 but <10 mm), or large (≥10 mm); shade tolerance types were intolerant, mod-

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Fig. 2. Change in the mean (a) frequency, (b) species richness, and (c) diversity (H ) of seedlings (dotted line), saplings (dashed line), and combined seedlings and saplings (solid line) of broad-leaf species in Cryptomeria plantations with distance from natural forest. Asterisks indicate significant decreasing trend (P ≤ 0.05). Vertical bars represent ±S.E.

erately tolerant, or tolerant; and maximum plant sizes were tall tree (≥15 m), small tree (8–15 m), or shrub/shrubby tree (≤8 m). To assign the species in these respective trait categories, we followed the descriptions in various existing literature (including Masaki, 2002; Nagaike, 2002; Satake et al., 1989; Takahashi and Katsuyama, 2000, 2001). The changes in the species’ relative frequency with distance from old growth forest based on functional traits were tested using linear regression. To find out which of the functional traits would best explain the difference in the distribution of broad-leaf species between the old growth forest-near plantation and intermediate-far plantations, generalized linear model (GLM) stepwise regression analysis was performed using the software R v.2.9.1. We grouped data from the old growth forest and near plantation separately from intermediate and far plantation based on similarity. Correlations between functional traits were tested using crosstabulation analysis with Pearson Chi-square test. The software SPSS v.16.0 was used for all linear regression, ANOVA and cross-tabulation analyses.

commonly encountered species in each distance). Fig. 2 shows that seedling frequency and species richness decreased with distance from the broad-leaf forest (linear regression, P = 0.004 and P = 0.022, respectively), whereas there were no visible trends with sapling species (linear regression, P = 0.510 and P = 0.427, respectively). Combining the seedling and sapling populations only gave a marginally significant distance effect on frequency (linear regression, P = 0.066). H did not exhibit significant changes with respect to distance (linear regression, P = 0.137 for seedlings and P = 0.350 for saplings). Cluster analysis showed that intermediate and far plantations are very similar to each other based on species composition. They formed a group that is distinct from the old growth forest/near plantation cluster based on seedling species and seedling and sapling species combined (Fig. 3a and c). When only the sapling species were considered, all three plantation types clustered away from the old growth forest (Fig. 3b).

3. Results

Analysis of species by individual functional traits revealed that the relative frequency of small-seeded species increased with increasing distance from the old growth forest (linear regression, seedlings: P = 0.001; saplings: P = 0.019; combined: P = 0.000) (Fig. 4a). In comparison, large-seeded species decreased (linear regression, seedlings: P = 0.001; saplings: P = 0.010; com-

3.1. Broad-leaf species diversity A total of 76 broad-leaf species were recorded (33 tall trees, 9 small trees, and 34 shrubs) (see Appendix A for the list of most

3.2. Functional trait analysis

Fig. 3. Cluster results of Jaccard similarity indices (similarity in broad-leaf species composition) of the old growth forest, near, intermediate, and far plantations. (a) Seedlings; (b) saplings; and (c) combined seedlings and saplings. Scales represent objective function of distance.

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Fig. 4. Change in the mean relative frequency percentage of seedlings (first column), saplings (second column) and combined seedlings and saplings (third column) of broad-leaf species in Cryptomeria plantations with respect to distance from old growth forest based on different functional traits that are associated with recruitment and regeneration. (a) Propagule size (circle, small; triangle, medium; square, large); (b) disperser type (diamond, frugivore; circle, gravity; triangle, wind; square, other); (c) shade tolerance (circle, intolerant; triangle, moderately tolerant; square, tolerant); and (d) maximum plant height (circle, tall tree; triangle, small tree; square, shrub). Asterisks indicate significant increasing or decreasing trend (P ≤ 0.05). Vertical bars represent ±S.E.

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Table 1 Results of general linear model stepwise analysis to test functional traits that could explain the occurrence of broad-leaf species in the intermediate and far plantations. Functional trait

Seedling z

P

z

P

z

P

Propagule size Disperser type Shade tolerance

−9.026 −3.886 –a

<2 × 10−16 0.000102 –

−8.926 −4.428 4.674

<2 × 10−16 9.52 × 10−6 2.95 × 10−6

−13.794 −7.793 4.811

<2 × 10−16 6.54 × 10−15 1.50 × 10−6

a

Sapling

Seedling and sapling

Dash indicates that the trait was not selected in the stepwise modeling procedure.

bined: P = 0.000). Medium-seeded species were not affected by distance. Separately, seedlings and saplings did not show any distancedependent trend in terms of disperser type (Fig. 4b). But combined seedling and sapling data showed that frugivoredispersed species increased in relative frequency with increasing distance from old growth forest (linear regression, P = 0.035), and this increase was largely dictated by Callicarpa japonica. Gravity-dispersed species, on the other hand, decreased (linear regression, P = 0.031) in the plantations. Species dispersed by wind or other modes did not have any significant trend. Linear regression also showed that among the shade tolerance types, only the moderately shade-tolerant species were affected by distance from old growth forest, increasing significantly in the plantations for seedlings (P = 0.012) and combined seedlings and saplings (P = 0.016), but not for saplings alone (P = 0.154) (Fig. 4c). Their increase in the plantations was largely dictated by Rhododendron obtusum, a small-seeded shrub. Shade-tolerant and intolerant species did not show any significant trend. Seedlings showed significant distance-dependent trends in terms of maximum plant height: tall tree species decreased while shrub species increased with increasing distance into the plantations (linear regression, P = 0.001 and P = 0.034, respectively) (Fig. 4d). Combined seedling and sapling data showed a decrease in tall tree species and an increase in small tree species with increasing distance into the plantations (linear regression, P = 0.006, P = 0.047, respectively). Saplings alone did not show distance-dependent trends based on species height. Analysis of the species using all traits together showed similar results to the single-trait analysis, but with some minor difference. Among all the functional traits studied, propagule size was the one that could best explain the difference in the distribution of broadleaf species between the old growth forest-near plantation and the intermediate-far plantations (GLM, seedlings: z = −9.026, saplings: z = −8.926, combined: z = − 13.794; P < 2 × 10−16 ) (Table 1.). Disperser type was also significant for seedlings, saplings and combined seedling and sapling, while shade tolerance was significant only for saplings and combined seedling and sapling (GLM, P < 0.01 for all factors). Maximum tree height was not a significant factor in explaining the distribution of the species studied in the multi-trait analysis. Since propagule size was the most important factor, we checked if it correlated with other traits. Cross-tab analysis showed that seed size and disperser type correlated (P < 0.000): 48% of winddispersed seeds are small, 80% of frugivore-dispersed seeds are medium and 100% of gravity-dispersed seeds are large. Seed size marginally correlated with shade tolerance (P = 0.054): 75% of moderately shade-tolerant species have small seeds, 52.2% of shade-intolerant species have medium-sized seeds, and 73% of shade-tolerant species have medium to large seeds. Seed size also marginally correlated with maximum plant height (P = 0.057): 48.8% of tall trees have medium-sized seeds, 44% of small trees have small seeds, and 55.9% of shrubs have medium-sized seeds.

4. Discussion 4.1. Community-level difference between old growth forest and plantations The frequency and species richness of broad-leaf species seedlings significantly decreased with increasing distance from old growth forest. This might mean that the old growth forest has better germination conditions than plantations (more safe sites) or that not enough seeds reach the plantations (seed limitation). Sapling diversity, on the other hand, did not show any significant trend. Species diversity in forest plantations has been shown to be affected by several factors such as stand age, herbivory, soil moisture, insolation, gap formation/size, and community assemblage (Battles et al., 2001; Kodani, 2006; Sakai et al., 2006; Utsugi et al., 2006; Yoshida et al., 2005). Sapling diversity in the sites we studied may be more dependent on one or more of these factors and not just simply distance from source. However, if only distance from seed source is taken into consideration, our results might imply that if recruitment limitation occurs in the plantations, it will be stronger at the seed-to-seedling transition than at the seedling-to-sapling transition. 4.2. Distance effect on species occurrence based on species functional traits Studies comparing diversity in plantations and other forest types have shown that broad-leaf species can have either higher, lower, or no difference in diversity between natural forest and plantation, depending on different factors (Nagaike, 2002; Nagaike and Hayashi, 2004; Kodani, 2006; Utsugi et al., 2006). In our study, Shannon diversity index did not reveal any significant distancedependent changes in the diversity of broad-leaf seedling and sapling species in the plantations. Defining the functional traits of the species in each forest type was much more enlightening however, and it revealed changes in species composition with respect to distance from old growth forest. The most evident change with respect to distance was with the propagule size of species. Small-seeded species increased in the plantations while large-seeded species decreased. This was not unexpected since the inverse relationship of seed size and dispersal probability has been demonstrated before (Jackson, 1981; Ingle, 2003). However, as observed by Ingle (2003), the effect of seed size on dispersal probability has largely been ignored by communitylevel dispersal studies, which group together species that differ in seed size, an assumption that she says may be inappropriate given the relationship of seed size with seed production and seedling establishment. Our study therefore is another proof of just how important seed size is in determining community composition. Disperser type was another factor that showed marked distant-dependent changes. The increase in relative frequency of frugivore-dispersed species in the plantations might seem to be in contrast to other studies that showed a general decrease in frugivore-dispersed species in plantations relative to broad-leaf forests (Nagaike, 2002; Kodani, 2006). However, the frugivore-

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dispersed species that occurred more in the plantations we studied were mostly small to medium-seeded species that are associated with disturbed vegetation, like Callicarpa japonica and Meliosma myriantha (Nagamatsu and Miura, 1997), and hence their increase in plantations may not be surprising. The sources of these seeds probably were parents that have already established and reached reproductive age in the plantations themselves, hence the old growth forest need not be the main source of their propagules. Gravity-dispersed species, on the other hand, decreased with increasing distance into the plantations. Although some of these gravity-dispersed species like Quercus spp. are secondarily dispersed by small mammals, they rarely reach distances more than 30 m from the parent plant (Miyaki and Kikuzawa, 1988; Dow and Ashley, 1996). In addition, disperser type correlated with propagule size, with all gravity-dispersed species having large seeds. Propagule size has been shown to affect dispersal and recruitment of tree species, and large-seeded species tend to be more seed-limited (Dalling and Hubbell, 2002) and have slower growth rates (Walters and Reich, 2000). Therefore, if recruitment limitation (seed limitation in particular) does occur in plantations, largeseeded, gravity-dispersed species would be more vulnerable than their other counterparts. Among the shade tolerance types, only moderately shadetolerant species showed distance-dependent changes in relative frequency. It is interesting to note that the relative frequency of shade-tolerant and shade-intolerant species showed marginal significance for saplings, but not for seedlings (data not shown). This may indicate that sapling occurrence may be more strongly influenced by shade tolerance than seedling occurrence. This is actually affirmed by GLM analysis, which showed that sapling occurrence in the intermediate and far plantations, but not seedling occurrence, could partly be explained by the species’ shade tolerance characteristics. Since the canopy trees of plantations are evergreen, light conditions in plantations are usually darker than old growth forests all year round. In natural old growth forests on the other hand, light conditions change with the season, and early spring and late autumn are particularly important for some species with longer leaf longevity than the broad-leaf canopy trees. The seedlings of tall tree species decreased with increasing distance from old growth forest, while shrub species increased. Saplings did not show any significant distance-dependent trend based on maximum height. This implies that should recruitment limitation occur in the plantations studied, tall tree species would be more susceptible to it, and it would be stronger at the seed-

to-seedling than at the seedling-to-sapling transition. However, maximum plant height was not a significant factor in the multitrait analyses, and this is probably because majority of both tall tree and shrub species have medium-sized seeds in the correlation analyses, and these correlations may have offset the importance of maximum plant height in the multi-trait analysis. Unsurprisingly, propagule size emerged as the trait that best explained the occurrence pattern of broad-leaf species in the plantations. And since propagule size has been shown to significantly affect dispersal distance and germination (Jackson, 1981; Ingle, 2003), our speculation is further affirmed that if recruitment limitation occurs in the plantations, the seed-to-seedling transition will be under greater pressures than the seedling-to-sapling transition. 4.3. Implications for management These conclusions are applicable for conifer plantations of similar age, climate, and management practices in Japan. Our study has shown that the frequency of broad-leaf species with certain functional traits decreases significantly in the plantations within a few meters away from the natural forest. We then suggest to forest policy-makers that to enhance biodiversity in such plantations, they must see to it that they maintain plantation sizes to within a few hundred meters wide, so they are within dispersal distances from forests that could potentially be natural seed sources of broad-leaf species. This would minimize the possible recruitment limitation to which certain species are vulnerable. If this is not possible, like in kilometer-wide plantations that have already been established in the past, management practices should take steps to drive succession such that potentially recruitment-limited species, like large-seeded gravity-dispersed tall tree species, may be able to overcome barriers to regeneration. Acknowledgements We would like to thank Bin Ishida for the invaluable assistance provided during field work and data encoding. This study was funded by the Ministry of Education, Culture, Sports, Science and Technology, Government of Japan. Appendix A. Propagule size, disperser, shade tolerance and maximum plant height categories of the 20 most frequently encountered species in the old growth forest and plantations.

Species name

Relative frequencya

Propagule sizeb

Disperserc

Shade toleranced

Maximum heighte

Old growth Acer amoenum Quercus serrata Acer rufinerve Ilex macropoda Acer crataegifolium Fraxinus lanuginosa Viburnum dilatatum Prunus grayana Kalopanax sciadophylloides Euonymus oxyphyllus Styrax japonica Styrax obassia Carpinus laxiflora Acer sieboldianum Carpinus cordata Sorbus alnifolia Acer mono Clethra barbinervis Viburnum phlebotrichum Rhododendron obtusum

56 39 36 28 26 25 24 23 22 20 18 18 17 15 14 14 13 13 12 11

L L L M L S M M M M L L S L M M L S M S

W G W F W W F F F F G G W W W F W W F W

Tol Intol Intol Tol Tol Tol Tol Tol Tol Tol Tol Tol Tol Tol Tol Tol Tol Tol N/A Mod Tol

Tall Tall Small Small Shrub Tall Shrub Tall Tall Shrub Shrub Tall Tall Tall Tall Tall Tall Small Shrub Shrub

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Appendix A (Continued Species name

Relative frequencya

Propagule sizeb

Disperserc

Shade toleranced

Maximum heighte

Near plantation Callicarpa japonica Prunus grayana Corylus sieboldiana Kalopanax sciadophylloides Hydrangea paniculata Styrax japonica Acer rufinerve Acer amoenum Carpinus laxiflora Carpinus cordata Cornus controversa Styrax obassia Acer crataegifolium Ilex macropoda Fraxinus lanuginosa Viburnum dilatatum Morus bombycis Symplocos chinensis Carpinus tchonoskii Euonymus oxyphyllus

26 26 25 25 24 23 22 18 17 16 15 15 13 13 13 13 12 12 11 11

S M M M S L L L S M M L L M S M S M S M

F F F F W G W W W W F G W F W F F F W F

Intol Tol Intol Tol Tol Tol Intol Tol Tol Tol Intol Tol Tol Tol Tol Tol Mod Tol N/A Intol Tol

Shrub Tall Shrub Tall Shrub Shrub Small Tall Tall Tall Tall Tall Shrub Small Tall Shrub Small Shrub Tall Shrub

Intermediate plantation Callicarpa japonica Pieris japonica Clethra barbinervis Styrax japonica Ilex macropoda Corylus sieboldiana Cornus controversa Kalopanax sciadophylloides Meliosma myriantha Morus bombycis Styrax obassia Prunus verecunda Sorbus alnifolia Acer amoenum Viburnum dilatatum Sorbus japonica Acer crataegifolium Acer rufinerve Pourthiaea villosa Prunus grayana

41 23 22 16 14 13 12 12 12 12 9 8 8 8 8 7 6 6 6 6

S S S L M M M M S S L M M L M M L L M M

F W W G F F F F F F G F F W F F W W F F

Intol Tol Tol Tol Tol Intol Intol Tol Tol Mod Tol Tol Intol Tol Tol Tol Intol Tol Intol N/A Tol

Shrub Shrub Small Shrub Small Shrub Tall Tall Small Small Tall Tall Tall Tall Shrub Tall Shrub Small Shrub Tall

Far plantation Ilex macropoda Clethra barbinervis Rhododendron obtusum Kalopanax sciadophylloides Callicarpa japonica Fraxinus lanuginosa Prunus verecunda Meliosma myriantha Styrax obassia Viburnum dilatatum Prunus grayana Rhus trichocarpa Clerodendrum trichotomum Hydrangea paniculata Morus bombycis Sorbus japonica Styrax japonica Acer mono Cornus controversa Pieris japonica

41 31 30 23 19 19 19 17 13 13 12 12 10 9 9 9 9 8 7 7

M S S M S S M S L M M M M S S M L L M S

F W W F F W F F G F F F F W F F G W F W

Tol Tol Mod Tol Tol Intol Tol Intol Tol Tol Tol Tol N/A Intol Tol Mod Tol Intol Tol Tol Intol Tol

Small Small Shrub Tall Shrub Tall Tall Small Tall Shrub Tall Shrub Shrub Shrub Small Tall Shrub Tall Tall Shrub

a b c d e

Relative frequency = (number of quadrats in which species occurs/total number of quadrats) × 100. Propagule size: S, small; M, medium; L, large. Disperser: G, gravity; F, frugivore; W, wind. Shade tolerance: intol, shade-intolerant; mod tol, moderately shade-tolerant; tol, shade-tolerant; N/A, no data. Maximum plant height: tall, tall tree; small, small tree; shrub, shrub or shrubby tree.

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