Population Structure and Substrates of Taiwan Yellow False
Cypress (Chamaecyparis obtusa var. formosana) in Yuanyang
Lake Nature Reserve and Nearby Szumakuszu, Taiwan
Chi-ChengLiao(1), Chang-Hung Chou(2), Jiunn-Tzong Wu(1,3,4)
(Manuscript received 7 November, 2002; accepted 20 December, 2002)
ABSTRACT: Chamaecyparis obtusa Sieb. & Zucc. var. formosana (Hayata) Rehder (Taiwan yellow false cypress) is one of the most important sources of timber in Taiwan. For sustainable use of this species, basic information about its regeneration under natural conditions is required, but this has been few until now. In this paper, the composition, population structure, growing substrates, and recruitment of Taiwan yellow false cypress were studied in Yuanyang Lake Nature Researve (YYL) and nearby Szumakuszu (SMKS) area, Taiwan. Two study sites in YYL were selected for comparison: one near a lakeshore (LS) and another at a mountain ridge top (MR). A site also was studied at SMKS, located 2 km west of the lake. Within each site, all woody plants with basal diameters larger than 1 cm, and population structures were recorded and analyzed in order to elucidate the recruitment pattern of Taiwan yellow false cypress. It was documented that floristic composition and canopy structure differed among the sites. An inverse J-shaped size distribution pattern for plants growing on down logs at the LS and MR sites suggests a stable and continuous recruitment of Taiwan yellow false cypress at both YYL locations. In contrast, the Taiwan yellow false cypress at SMKS had a discontinuous size distribution, independent of inhabited substrate type. For regeneration of Taiwan yellow false cypress in SMKS, a large-scale disturbance, instead of single uprooted trees, may be necessary. The results indicate that down log is important substrate for regeneration of Taiwan yellow false cypress, particularly in forests at the YYL, LS and MR. Based on the findings in YYL, some down logs are suggested to leave in clear cutting plantation, because they might provide suitable space for regeneration of Taiwan yellow false cypress. This suggestion is expected to reduce the cost and work frequency of management.
KEY WORDS: Chamaecyparis obtusa var. formosana, Down log, Growing substrate, Population structure, Regeneration.
INTRODUCTION
Temperate coniferous forests is one of the vegetation types in Taiwan. Distributed between evergreen broadleaf forests and cool temperate coniferous forests, their elevation ranges from 1,500 to 2,500 m above sea level (a.s.l.) (Su, 1984), and accounted for 48,500 ha (2.3%) of natural forests (Taiwan Forest Burean, 1995). The dominant species,
Chamaecyparis formosensis Matsum. (Taiwan red false cypress) and Chamaecyparis obtusa
Sieb. & Zucc. var. formosana (Hayata) Rehder (Taiwan yellow false cypress), are important for wood production. Therefore, they have suffered from timber harvesting (Su, 1984; Jen, 1995). Although deforestation ceased in 1985, large portions of the virgin false cypress forests were fragmented and had been transformed into man-made plantations. In view of this situation, investigations on compositional and distribution patterns of false cypress forest vegetation are important.
___________________________________________________________________________
1. Department of Botany, National Taiwan University, Taipei 106, Taiwan.
2. Graduate Institute of Tropical Agriculture, National Pingtung University of Science and Technology, Pintung 912, Taiwan.
3. Institute of Botany, Academia Sinica, Taipei 115, Taiwan.
The Yuanyang Lake Natural Reserve Area (YYL), located in northern Taiwan, is the only site declared to protect the lake and Taiwan yellow false cypress forest ecosystem (Liu and Hsu, 1973; Hwang et al., 1996; Chou et al., 2000). Though the floristic composition and population structure of Taiwan yellow false cypress in YYL have previously been described (Liu and Hsu, 1973; Chou et al., 2000), there is a controversy over regeneration of the species. Evidences from the fossil pollen (Chen and Wu, 1999) and population structure (Chou et al., 2000) within YYL determined that Taiwan yellow false cypress could regenerate without anthropogenic disturbance. On the contrary, the species regenerate well in the plantation after clear cutting and removing down logs and standing snags (Hung, 1984; Lo-Cho et al., 1999). In order to provide critical information for management of the remaining natural forests, the major objective of this research was to expand our knowledge about this ecosystem, by considering community composition, population structure, and, importantly, characteristics on the regeneration of Taiwan yellow false cypress.
MATERIALS AND METHODS
Site description
The Yuanyang Lake Nature Reserve (YYL) is located near the windward slope of Hsehshan Mountain Range in northern Taiwan, with elevation ranging between 1650 to 2432 m (24°35′ N and 121°24′ E). The windward slope of Hsehshan Mountain Range accepts heavy precipitation from northeast monsoon and typhoon (Su, 1984; Wang and Li, 2000). From the data of precipitation stations around YYL, a steep precipitation gradient from 4000 to 2000 mm were found from the east to the west slope of Hsehshan Mountain Range (Figs. 1 and 2) (modified from Wang & Li, 2000). Heavy cloud and fog are so frequent that solar radiation is considerably reduced. Heavy moisture resulted in abundant growth of mosses on the forest floor, tree trunks, and down logs in the YYL (Hwang et al., 1996; Chang et al., 2002). The average annual air temperature is 13 °C; the highest monthly mean is 27 °C in June, and the lowest temperature is 10 °C in January (Hwang et al., 1996). The temperature is rarely lower than 0 °C, and snowfall is rare in winter.
Taiwan yellow false cypress generally dominates the forest within the YYL, which is characterized by simple and open canopy structure that mostly composed by Taiwan yellow false cypress. The broadleaf species densely occupied the shrub layer, and few can reach the canopy. The undergrowth was different along the elevation. It was dominated by Plagiogyria
euphlebia at lower elevation as compared to higher elevation where dense bamboo, Yushania niitakayamensis (Hayata) Keng, typically occupies the forest floor (Liu and Hsu, 1973; Chou et al., 2000). Two major vegetation types were recognized by different undergrowth in YYL.
In contrast, the forest which sits on the mountain saddle of west side area about 2 km away from the lake is different from the forest in YYL. By preliminary observation, the forest near SMKS has relatively lower density of shrubs, less coverage of mosses and herb layer. Most importantly, the canopy structure is complex, closed and formed by broadleaf trees. Taiwan yellow false cypress emerged from the canopy.
Field study and data analysis 1. Forest analysis in YYL
The forests at lakeshore area (LS) and mountain ridge top (MR) are recognized as homogeneous. The locations of study sites were selected to avoid visitor’s interference. Two
Fig. 1: Map of Chi-lan-shan area with the isohyet showing the locations of study sites in Yuanyang Lake Nature Reserve. (LS and MR sites) and Szumakuszu (SMKS site).
Average precipitation ( m m yr -1 ) 0 1000 2000 3000 4000 5000 Paishih ( 1636 m ) Anpu ( 1457 m ) H siuluan ( 870 m ) Yuf eng ( 770 m ) Chenshipao ( 1550 m ) Sankuang ( 638 m ) N anshan ( 1150 m ) Paling ( 1220 m ) K alaho ( 1150 m ) Sz uchi ( 788 m ) Lium aoan ( 585 m ) YYL ( 1650 m ) Mingchih ( 1150 m ) Chilan ( 1490 m ) Taipinshan ( 2000 m ) west <---> east
Fig. 2: The average precipitations at various stations (with elevation in brackets) around the area of Yuanyang Lake Nature Reserve (YYL) with respect to their relative position.
Study sites in the YYL, one near the lakeshore (LS) at elevation 1,650 m, and another at the mountain ridge top (MR) at elevation ca. 2,000 m were selected for this study (Fig. 1). The 0.25 ha square LS site was divided into 25 plots by compass determining the WE and NS lines. Each plot in the three sites measured 10 x 10 m2. The slope was averaged 8.5°. Because
of the restriction of steep slope, the MR site had only 0.17 ha and was divided into 17 plots. It was established along the mountain ridge, and the slope was averaged 30°. A third site, located near the vicinity of Szumakuszu (SMKS), at an elevation of ca. 1,800 m, also was 0.25 ha and was divided into 25 plots. The slope of the SMKS site was averaged 18.6°. All trees with basal diameter larger than 1 cm were measured. Basal diameter measured the trunk base at 30 cm above ground. The type of substrate on which Taiwan yellow false cypress occurred was also recorded. The sums of relative density and relative basal area of each plant species at the study sites were calculated and designated as the dominance value (DV). 2. Growing substrate of Taiwan yellow false cypress
For a stable and continuously regenerating population, its size class distribution should approach an inversed J-shaped curve (Daubenmire, 1968; Veblen et al., 1979). Size class distributions of broadleaf trees and Taiwan yellow false cypress that presented the dynamics of the population from seedlings to adults were obtained from the census data of the three sites. Growing substrates of Taiwan yellow false cypress that included soil and down logs were recorded to analyze its regeneration characteristics in different forest types. The use of size-class analysis to assess the regeneration status of a population requires an assumption of significant positive correlation between tree diameter and age (Veblen et al., 1979; Pederson
et al., 1997). The annual ring vs. basal diameter of Taiwan yellow false cypress were
analyzed 118 individuals and formulated as annual ring = 37.62 + 6.04 ×diameter (r2 = 0.72;
Fig. 3: Correlation between annual ring and basal diameter of Taiwan yellow false cypress.
RESULTS
Characteristics of the YYL Taiwan yellow false cypress forest
A total of 66 plant species was recorded in the YYL. Of these plants, 42, 39, and 31 species were found at the LS, MR, and SMKS sites, respectively (Table 1). Densities of Taiwan yellow false cypress at the three sites differed, although floristic composition at the LS site was quite similar to that at MR (Table 2). The densities of plants at LS and MR were higher, with 848 and 1271 individuals/ha-1
, respectively, than at SMKS, where only 48 individuals ha-1 were recorded (Table 1). The densities of broadleaf trees were: 5,840 stems ha-1
, 8,823 stems ha-1
, and 4,392 stems ha-1
at LS, MR and SMKS, respectively. Most of the dominant broadleaf species at LS and MR were shrubs, whereas at SMKS the giant tree was dominant (Table 2). Differences in floristic composition among these three study sites reflected the diversity of forest structures within them.
Table 1. Summary of forest characteristics at each study sites.
LS site MC site SMKS site
Area of site (ha-1
) 0.25 0.17 0.25
Number of plant species 42 39 31
Number of individual recorded 1807 1761 1148
Total basal area (m2 ha-1
) 58.55 72.55 133.18
Density of false cypress (individuals ha-1) 848 1271 48
Density of broadleaf trees (individuals ha-1
) 5840 8823 4392
The canopy structures at LS and MR were significantly different from that at SMKS. Over 98% of broadleaf trees were <10 m tall at the LS and MR sites. Only a few broadleaf trees reached the canopy layer. Consequently, the first canopy layer consisted almost entirely of Taiwan yellow false cypress, forming a discontinuous canopy layer. The broadleaf species in the dense shrub layer were Illicium philippinense, Rhododendron formosanum, Dendropanax
There were 147 individuals of broadleaf trees higher than 10 m at SMKS. They formed a continuous canopy layer. In contrast to the other two sites, the major components of canopy broadleaf species at SMKS were Cyclobalanopsis sessilifolia, Cyclobalanopsis glauca, and
Daphniphyllum glaucescens subsp. oldhamii. Taiwan yellow false cypress occurred only as
emergent trees in the canopy layer. Plants such as I. philippinense, Neolitsea acuminatissima,
Camelia tenuifolia, Ilex uraiensis, Eurya acuminata, and Schefflera actinophylla were the
dominant species in the shrub layer. Among these plants, I. philippinense, N. acuminatissima, and S. actinophylla were evenly distributed at all three study sites, while C. tenuifolia, I.
uraiensis, and E. acuminata were only found at SMKS site (Table 2). In comparing with LS
and MR sites, the density of shrubs was lower at SMKS.
The components of undergrowth of the forests were quite different between the study sites. Plentiful mosses covered the under-layers at sites in YYL, whereas they were seldom observed in SMKS. A substantial amount of bamboo (about 116 ± 10 culms/m2) was found at the MR, but not at the other two sites.
Size structure of Taiwan yellow false cypress on different substrates in YYL
The number and the size of Taiwan yellow false cypress plants growing on various substrates within the study sites were recorded. A majority of young Taiwan yellow false cypress was found to inhabit down logs rather than soil (Fig. 4). On soil, there were only 28 and 3 individuals, respectively, at LS and MR. This indicates that soil plays a less important role than down logs for regeneration of Taiwan yellow false cypress at these locations.
At the SMKS site, there were 2 seedlings and 10 amture trees of Taiwan yellow false cypress, respectively, on down logs and soil. This suggests that down logs are less important than soil for regeneration at this location.
Size structure of dominant broadleaf species
The sizes of dominant broadleaf trees varied among the study sites. However, the pattern of size distribution always was an inverse J-shape (Fig. 5). There was a difference in tree size between sites. At SMKS, there were 71 individuals with BD larger than 20 cm, whereas only 15 and 0 individuals, respectively, had such sizes at LS and MR. At LS, all dominant broadleaf trees exhibited an inverse J-shape pattern in size distribution (Fig. 6). At MR, five of the dominant species, N. acuminatissima, R. formosanum, D. pellucidopunctata,
Rhododendron kawakamii var. flaviflorum, and Neolitsea variabillima, had many more plants
with basal diameters between 4 and 7 cm than any other size, while other plants had inverse J-shape patterns in their size distribution, similar to that observed at LS (Fig. 7). At SMKS, the size distribution patterns were somewhat different from those observed at other sites. Both the L-shape and inverse J-shape distribution patterns were observed for all of the dominant plant species except Cyclobalanopsis glauca, which displayed an irregularly distributed pattern (Fig. 8).
DISCUSSION
The forests in YYL and SMKS are both free from anthropogenic disturbance. The differences in floristic composition, tree density, canopy structure, and undergrowth among the three sites must be contributed by variations in natural environmental factors. According to Su (1984), there are two major factors that influence vegetation type in Taiwan: elevation
0 10 20 30 40 50 60 2 4 6 8 10 20 40 60 80 >90 Down log n = 184 0 20 40 60 80 2 4 6 8 10 20 40 60 80 >90 n = 213 Down log 0 10 20 30 40 50 60 2 4 6 8 10 20 40 60 80 >90 Down log n = 2 0 10 20 30 40 50 60 2 4 6 8 10 20 40 60 80 >90 Soil n = 28 0 10 20 30 40 50 60 2 4 6 8 10 20 40 60 80 >90 Soil n = 3 0 10 20 30 40 50 60 2 4 6 8 10 20 40 60 80 >90 Soil n = 10 LS site MR site SMKS site Basal diameter (cm) Number of individuals
Fig. 4: Comparisons of size class (basal diameter) compositions of yellow cypress plants grown on down logs and with that on soil at three study sites.
and precipitation. Any general explanation of Chamaecyparis forest distribution must emphasize limitation by water (Zobel, 1998). Thus, precipitation is considered to play a more important role in affecting vegetations of the three sites. Though SMKS is very close to YYL, their precipitation regime is different (Fig. 1). In YYL, monsoon brings in a significant amount of precipitation every year, but that is not the case for SMKS area. SMKS located at the leeward side of the mountain slope, and in general is drier than YYL. This makes a steep precipitation gradient from YYL to SMKS even within a short distance (about 10 km), and thus the differences in vegetation composition and structures.
LS site
0 100 200 300 400 2 4 6 8 10 12 14 16 18 20 >20 n = 1460MR site
0 100 200 300 400 2 4 6 8 10 12 14 16 18 20 >20 n = 1500SMKS site
0 100 200 300 400 2 4 6 8 10 12 14 16 18 20 >20 n = 1098Basal diameter class (cm)
Number of individuals
Fig. 5: Comparisons of size (basal diameter) distribution of broadleaf plants between three study sites.
The inversed J-shaped pattern of size distribution of a tree species is considered to be stable and continuously regenerating (Hett and Loucks, 1976; Veblen et al., 1979; Read and Hill, 1988; Ohsawa, 1991). At both study sites in YYL, Taiwan yellow false cypress exhibited such a size distribution pattern, whereas at SMKS the size distribution was irregular. Although the detailed mechanism is remain investigated, size class distribution revealed a well regeneration of Taiwan yellow false cypress on down logs in YYL.
The regeneration of a forest is affected by a number of factors. Light factor is investigated in some researches. Light intensity over 40% of full sunlight was favorable for the growth of
Illicium philippinense 0 10 20 30 40 50 5 10 15 20 >20 n = 197 Schefflera taiwaniana 0 40 80 120 160 5 10 15 20 >20 n = 197 Neolitsea acuminatissima 0 2 4 6 8 10 12 5 10 15 20 >20 n = 20 Adinandra formosana 0 30 60 90 120 150 180 5 10 15 20 >20 n = 281 Barthea formosana 0 40 80 120 160 5 10 15 20 >20 n = 186 Rhododendron formosanum 0 10 20 30 40 50 60 5 10 15 20 >20 n = 370 Dendropanax pellucidopunctata 0 2 4 6 8 10 12 14 5 10 15 20 >20 n = 38 Viburnum sympodiale 0 10 20 30 40 50 60 5 10 15 20 >20 n = 77 Skimmia arisanensis 0 10 20 30 40 50 60 5 10 15 20 >20 n = 57
Basal diameter (cm)
Number of individuals
Rhododendron formosanum 0 3 6 9 12 15 5 10 15 20 >20 n = 65 Illicium philippinense 0 5 10 15 20 25 30 35 5 10 15 20 >20 n = 104
Rhododendron kawakamii var. flaviflorum
0 5 10 15 20 25 5 10 15 20 >20 n = 94 Adinandra formosana 0 5 10 15 20 25 30 35 5 10 15 20 >20 n = 83 Barthea formosana 0 20 40 60 80 100 120 5 10 15 20 >20 n = 193 Neolitsea acuminatissima 0 5 10 15 20 25 30 35 5 10 15 20 >20 n = 178 Dendropanax pellucidopunctata 0 4 8 12 16 20 5 10 15 20 >20 n = 126 Schefflera taiwaniana 0 10 20 30 40 5 10 15 20 >20 n = 79 Neolitsea variabillima 0 5 10 15 20 25 30 5 10 15 20 >20 n = 172
Basal diameter (cm)
Number of individuals
Illicium philippinense 0 10 20 30 40 50 60 5 10 15 20 >20 n = 156
Daphniphyllum glaucescens var. oldhamii
0 5 10 15 20 5 10 15 20 >20 n = 82 Cyclobalanopsis glauca 0 2 4 6 8 5 10 15 20 >20 n = 35 Ilex uraiensis 0 10 20 30 40 50 60 5 10 15 20 >20 n = 110 Neolitsea acuminatissima 0 20 40 60 80 5 10 15 20 >20 n = 125 Camelia tenuifolia 0 5 10 15 20 25 30 5 10 15 20 >20 n = 87 Eurya acuminata 0 4 8 12 16 20 5 10 15 20 >20 n = 58 Schefflera taiwaniana 0 5 10 15 20 25 30 5 10 15 20 >20 n = 35 Cyclobalanopsis sessilifolia 0 10 20 30 40 50 5 10 15 20 >20 n = 103
Basal diameter (cm)
Number of individuals
Taiwan yellow false cypress seedlings (Lin et al., 1958; Fang et al., 1991). Thinning and pruning could also promote growth of the species (Hung, 1984; Chiu et al., 1993; Lo-Cho et
al., 1999). Consequently, Taiwan yellow false cypress is inferred to be a shade-intolerant
species. At the SMKS site, Taiwan yellow false cypress seedlings might be stressed by a low light regime, because the canopy structure is closed. Thus, three hypotheses are proposed in regard to the regeneration of Taiwan yellow false cypress. First, species without suppressed saplings and gap successors cannot regenerate in gaps under current gap-disturbance regime; thus large scales disturbances may be needed for their regeneration (Yamamoto, 1992). In this case, extensive open areas caused by massive disturbance might be necessary for Taiwan yellow false cypress regeneration under multiple canopy coverage (Liu, 1975). Second, most conifers have a very long life span, so that one generation can dominate at a site for a long period of time without regeneration (Liu, 1975). In this case, few seedlings are necessary to maintain the populations within a community (Read and Hill, 1988). Because two saplings were found, Taiwan yellow false cypress is considered to use this kind of regeneration strategy in SMKS. Third, the discontinuous population structure of Taiwan yellow false cypress was sustained on the upslope of the SMKS site by tiny seeds that can disperse from the upslope forests and become established on the rare suitable regeneration sites in SMKS. Small seedlings on down logs might avoid competition and suppression from undergrowth, such as bamboo, in temperate beech and mixed hardwood-conifer forests in Japan (Nakashizuka, 1989; Abe et al., 2001). A similar situation seems to occur in the YYL forest. Dense bamboo on the ground of MR site was supposed to suppress seedlings of woody species. However, there are numerous Taiwan yellow false cypress seedlings on down logs, giving rise to an avoidance of suppression from bamboo. Apparently, down logs provide substrate that ensures the regeneration of young Taiwan yellow false cypress.
Disturbance could promote establishment of Chamaecyparis lawsoniana in Oregon, USA (Hawk, 1977; Zobel, 1980; Zobel and Hawk, 1980) and Chamaecyparis obtusa in Japan (Yamamoto, 1988). It is also necessary for Taiwan yellow false cypress in Taiwan (Hung, 1984). One of the former management strategies for Taiwan yellow false cypress plantations was to remove down logs, to thin the broadleaf trees, and to disturb the herb layers in order to promote establishment of seedlings on the forest floor (Hung, 1984; Chiu et al., 1995; Lo-Cho
et al., 1999). This management strategy has successfully established Taiwan yellow false
cypress forests, and provides sustainable use of the species. However, forest managed in this manner requires frequent work with a high cost. In the present study, down logs occupied 1.33 % of the forest floor area at LS site (unpublished data) provided suitable space for regeneration of young Taiwan yellow false cypress, as well as reduced suppression from bamboo. Without anthropogenic disturbance, down log was not removed and might affect on the regeneration of Taiwan yellow false cypress. This finding might be helpful on improving management strategy. If some down logs were leaved in clear cutting area, seedlings might recruit on the down logs and avoid inter-species competition. This suggestion is expected to reduce the frequency of disturbance work and the cost in plantation management.
ACKNOWLEDGMENTS
We would like to thank the Forest Conservation and Management Administration, Veterans, Affairs Commision, Executive Yuan, Taiwan for permission to conduct research in the Yuanyang Lake Nature Reserve. We are grateful to Dr. Chang-Fu Hsieh in the Department of Botany, National Taiwan University, Taipei, Taiwan for his critical reading of
our manuscript. We also thank Dr. Shih-Chieh Chang in the Institute of Natural Resources, National Dong Hwa University, Hualien, Taiwan for his useful discussions. We would like to appreciate Ms. Hui-Chen Peng, Shu-Ling Wu and Mr. Po-Chun Chen, Ming-Yong Chang, Chong-Ming Liu for their help in field experiments.
LITERATURE CITED
Abe, M., H. Miguchi and T. Nakashizuka. 2001. An interactive effect of simultaneous death of dwarf bamboo, canopy gap, and predatory rodents on beech regeneration. Oecologia 127: 281-286.
Chang, S.-C., I.-L. Lai and J.-T. Wu. 2002. Estimation of fog deposition on epiphytic bryophytes in a subtropical montane forest ecosystem in northeastern Taiwan. Atmospheric Res. 64: 159-167.
Chen, S.-H. and J.-T. Wu. 1999. Paleolimnological environment indicated by the diatom and pollen assemblages in an alpine lake of Taiwan. J. Paleolimnol. 22: 149-159.
Chiu, C.-M., C.-N. Lo-Cho and H.-H. Chung. 1995. The stem form and crown structure of natural regeneration stands of Chamaecyparis taiwanensis in Chi-Lan-Shan Area. Bull. Taiwan For. Res. Inst. (New Series) 10: 121-130.
Chou, C.-H., T.-Y. Chen, C.-C. Liao and C.-I. Peng. 2000. Long-term ecological research in the Yuanyang Lake forest ecosystem I. Vegetation composition and analysis. Bot. Bull. Acad. Sin. 41: 61-72.
Daubenmire, R. 1968. Plant communities: a textbook of synecology. Harper & Row, New York.
Fang, Y.-K., T.-S. Liao, L.-Y. Chiu and H.-C. Lin. 1991. Effects of various light intensities on the growth of seedlings of three coniferous tree species. Bull. Exp. For. Nat. Chung Hsing Univ. 13: 29-56.
Hawk, G. M. 1977. Comparative study of temperate Chamaecyparis forests. Ph.D. Diss., Oregon State Univ., Corvallis.
Hett, J. M. and O. L. Loucks. 1976. Age structure models of balsam fir and eastern hemlock. J. Ecology 64: 1029-1044.
Hung, L. P. 1984. The effect of improvement by selective cutting methods for the natural forest of cypress on high mountain area in Taiwan. Quar. J. Chin. For. 17: 47-56.
Hwang, Y.-H., C.-W. Fang and M.-H. Yin. 1996. Primary production and chemical composition of emergent aquatic macrophytes, Schoenoplectus mucronatus ssp. robustus and Sparganium fallax, in Lake Yuan-yang, Taiwan. Bot. Bull. Acad. Sin. 37: 265-273. Jen, I.-A. 1995. Expectation and historical review of cypress (Chamaecyparis spp.) timber
production in Taiwan. Bull. Taiwan For. Res. Inst. (New Series) 10: 227-234.
Lin, W.-F., W.-C. Lin and J.-L. Lu. 1958. Studies on the light intensities required for growth of seedlings of Taiwan red cypress (Chamaecyparis formosensis Matsum.). Bull. Taiwan For. Res. Inst. No. 55. Taipei, Taiwan.
Liu, T. and K.-S. Hsu. 1973. Ecological study on Yuan-yang Lake Natural Area Reserve. Bull. Taiwan For. Res. Inst. No. 237. Taipei, Taiwan.
Liu, V.-T. 1975. Ecological study on Chamaecyparis forests in Taiwan. J. Agr. Asso. China New Series 92: 143-178.
Lo-Cho, C.-N., C.-M. Chiu and Y.-C. Chen. 1999. Effects of cleaning and pruning on natural-regenerated cypress stands. Bull. Taiwan For. Res. Inst. (New Series) 14: 315-321.
Nakashizuka, T. 1989. Role of uprooting in composition and dynamics of an old-growth forest in Japan. Ecology 70: 1273-1278.
Ohsawa, M. 1991. Structural comparison of tropical montane rain forests along latitudinal and altitudinal gradients in south and east Asia. Vegetatio 97: 1-10.
Pederson, N. A., R. H. Jones and R. R. Sharitz. 1997. Age structure and possible origins of old Pinus taeda stands in a floodplain forest. J. Torrey Bot. Soc. 124: 111-123.
Read, J. and R. S. Hill. 1988. The dynamics of some rainforest associations in Tasmania. J. Ecology 76: 558-584.
Su, H.-J. 1984. Studies on the climate and vegetation types of the natural forests in Taiwan (II) Altitudinal vegetation zones in relation to temperature gradient. Quar. J. Chin. For. 17: 57-73.
Taiwan Forest Burean. 1995. The third forest resource and land use inventory in Taiwan. Council of Agriculture.
Veblen, T. T., D. H. Ashton and F. M. Schlegel. 1979. Tree regeneration strategies in a lowland Nothofagus dominated forests in south-central Chile. J. Biogeogr. 6: 329-340. Wang, H. and C.-T. Li. 2000. Studies on the geological and topographical resources of
Chamaecyparis forest in Chi-lan Shan area. Chinese National Park Society, Taipei,
Taiwan.
Yamamoto, S. 1988. Seedling recruitment of Chamaecyparis obtusa and Sciadopitys
verticillata in different microenvironments in an old-growth Sciadopitys verticillata
forest. Bot. Mag. Tokyo 101: 61-71.
Yamamoto, S. 1992. Gap characteristics and gap regeneration in primary evergreen broad-leaved forests of Western Japan. Bot. Mag. Tokyo 105: 29-45.
Zobel, D. B. 1980. Effect of forest floor disturbance on seedling establishment of
Chamaecyparis lawsoniana. Can. J. For. Res. 10: 441-446.
Zobel, D. B. 1998. Chamaecyparis forest: a comparative analysis. In: Laderman, A. D. (Ed.), Coastally Restricted Forests. Oxford University Press, Oxford, pp. 39-53.
Zobel, D. B. and G. M. Hawk. 1980. The environment of Chamaecyparis lawsoniana. Am. Midl. Nat. 103: 280-297.
