Bot. Bull. Acad. Sin. (2000) 41: 61-72

Chou et al. — Vegetation composition of Yuanyang Lake

Long-term ecological research in the Yuanyang Lake forest ecosystem I. Vegetation composition and analysis⁴

Chang-Hung Chou^1,3, Tze-Ying Chen², Chi-Cheng Liao¹ and Ching-I Peng¹

¹Institute of Botany, Academia Sinica, Taipei, Taiwan 115, ROC

²Ilan Institute of Technology, Ilan, Taiwan, ROC

(Received April 26, 1999; Accepted July 30, 1999)

Abstract. The Yuanyang Lake Nature Preserve is located in the northeastern part of Hsinchu County, Taiwan. It is the uppermost head water of the Tahan River watershed at 1,650-2,432 m altitude. The total area of the natural preserve is about 374 ha, of which the lake occupies about 3.6 ha and the marshy area encircling the lake about 2.2 ha. The surrounding hillsides are dominated by cypress forests. Floristic analyses by means of Two-Way Indicator Species Analysis (TWINSPAN) and Detrend Correspondence Analysis (DCA) were conducted at the site. The findings of the former analysis concluded that the forest could be divided into two communities, namely a coniferous-hardwood community, and a swamp or early succession community. The former comprises (a) Chamaecyparis formosensis, C. obtusa var. formosana, Tsuga chinesis and (b) Rhododendron mariseii-Rhamus cranata. The swamp or early succession community comprises (a) Potamogeton octandrus, Sparganium fallax and Schaenoplectus mucronatus, (b) Miscanthus transmorrisonesis and Schoenoplectus morrisonensis. In total, there are 185 species of vascular plants, in 115 genera and 71 families. The cypress community has reached its stable stage, and Chamaecyparis species are capable of self regeneration. A successional trend of vegetation in the nature preserve area was proposed; however, the mechanism of the successional trend on the aquatic communities needs further investigation.

Keywords: Chamaecyparis; Community formation; Florisitc analysis; Miscanthus transmorrisonesis; Potamogeton octandrus; Rhododendron mariseii; Sparganium fallex; Successional trend; Yuanyang Lake.

Introduction

The Long-Term Ecological Research (LTER) program is one of the core projects of the Global Change and Terrestrial Ecosystem program (GCTE), which is under the umbrella of the International Geosphere-Biosphere Programme (IGBP). The Taiwan LTER project was initiated by the senior author in 1992 under the auspices of the Academia Sinica and the National Science Council of Taiwan. The main objectives of the Taiwan LTER are: (1) to understand long-term ecological changes in Taiwan, (2) to elucidate the mechanisms involved in ecological processes, (3) to provide suitable ecological information for social and economic development, and (4) to merit membership in an international LTER network in order to provide ecological information of regional and global interest. Taiwan LTER studies put emphasis upon the structure and function of the forest ecosystem as well as the hydrological and nutrient flux of the ecosystem in Taiwan. The database will also be made available in the global change research program. Such information is valuable for ecological and environmental education, as it will call upon people’s awareness of the importance of natural conservancy and

the impact of environmental change on the terrestrial ecosystem. Studying the structure and function of forest ecosystems is particularly important for Taiwan because forests cover 52% of the island and forest management and conservation are extremely important for the survivors of all living organisms in Taiwan. Forests are also the fundamental basis for water, timber and clean air for all organisms, and the forest composition and vegetation pattern are particularly important for biogeochemical and hydrological cycles in the forest ecosystems.

The Yuanyang Lake (YYL) Nature Preserve is one of the five Taiwan LTER sites. Located in the northeastern part of Hsinchu County, it consists of coniferous forest, hardwood forest, pteridophytes, epiphytes, such as mosses and liverworts, grassland species and several aquatic plants. The vegetation of the YYL was previously studied by Liu (1966) and Kuo and Tsian (1993), who reported that the predominant Chamaecyparis formosensis and C. obtusa var. formosana are distributed mainly in a fog zone. Lin and Chiu (1994) also reported that six plant communities and 252 species were found. Subsequent studies conducted much emphasized the cypress forest (Chang, 1963; Liu and Ying, 1973; Liu and Hsu, 1973; Chen, 1996; Lin and Chiu, 1994) and pollen analysis of associated species, e.g., Quercus and Alnus (Chen and Yang, 1996). Nevertheless, a detailed analysis of the vegetation pattern and composition at the YYL is not available. The present study thus aims to describe not only floristic com

³Corresponding author.

⁴This study was supported by series of grants to CHC and CIP from a five-year (1992-1997) Research Plan of the Institute of Botany, Academia Sinica, Taipei.

Botanical Bulletin of Academia Sinica, Vol. 41, 2000

position but also the vegetation pattern of the YYL forest ecosystem.

Study Site

The Yuanyang Lake Forest Ecosystem Research (called YYLFER) is conducted at the Yuanyang Lake Nature Preserve, which is located at N24°35’, E121°24’ in the northeastern part of Hsinchu County, Taiwan, at the uppermost head water of the Tahan River watershed with an elevation of 1,650-2,432 m. The total area of the natural preserve is about 374 ha, of which the lake is about 3.6 ha and the marsh area encircling the lake is about 2.2 ha. (Figure 1A). The surrounding hillsides are dominated by cypress forest. Supported by Taiwan’s Central Weather Bureau, a weather station was established near the site in 1992. Weather data, including monthly rainfall and air temperature, have been collected since 1992 and 1993,

respectively. Daily solar radiation data at the YYL, collected from October 1992 to September 1995, ranged from 0 to 25 MJ/m²/day (Hwang et al., 1966). The maximum air temperature was in the summer, ranging from 16 to 27°C; the minimum air temperatures ranged from -5 to 13.5°C, and the mean air temperatures ranged from 5 to 17.5°C. Thus, YYL has a temperate, heavy moist climate.

Materials and Methods

Sampling and Measuring Techniques

Regarding the sampling, sixteen plots were selected in the YYL forest area for the vegetation composition study. Of them, 10 quadrats, 10×10 m² or 5×5 m² each were employed for detailed forest analysis (Figure 1A). For aquatic community study, on the other hand, 36 plots were selected around the lake area. Of them, 10 quadrates, 5×5 m² or 3×3 m² each, were selected for detailed analysis (Figure 1B). In the forest community DBH (diameter at breast height) was measured for all plants above 1 meter tall. The number of plants of each species per plot and coverage of basal area at breast height of each plant was measured. Dominance value (DV) of each species is the sum of relative density and relative coverage of each species in the community (Curtis and McIntosh, 1951). By using an Octave scale (Gauch, 1982), the data were divided into 10 scale indexes from 0 to 9 and were analyzed by a Two-Way Indicator Species Analysis (TWINSPAN) (Hill, 1979) and by a Detrend Correspondence Analysis (DCA) (Hill and Gauch, 1980).

For environmental factor analysis, information of altitude, slope, orientation, geographical position, and elevation above lake surface was analyzed to obtain a correlation between the environmental parameters and sampling plots. These environmental parameters are as follows:

Altitude. The data of altitude is important for environmental analysis and is ranked high in the hierarchy of environmental factors (Billings, 1952).

Slope. The slope recorded by using a slope meter is thought to be associated with soil development, water drainage, and water content.

Orientation. Different orientation may affect temperature, radiation, humidity, and soil moisture. The orientation was based on the major facing side. The degree of slope is associated with water gradient and is designated as 1(=southwest), 2(=south), 3(=west), 4(=southeast), 5(=northwest), 6(=east), 7(=north), and 8(=northeast).

Geographic position. The geographic position is defined as the correlation between habitat position and topographic position. The geographic positions are designated as follows: 1(=summit ridge), 2(=middle hill or branch), 3(=downhill), 4(=valley, creek side, riverside) and 5(=lake surface). The numbers used to evaluate the degree of soil moisture are in an increasing order, i.e., 1 is the driest land, and 5 is the most moist area.

Figure 1. The geographic location of the Yuanyang Lake (YYL) forest site. Numbers indicate the sampling plots. A, sampling plots in the YYL forest site; B, sampling plots around the YYL area.

Chou et al. — Vegetation composition of Yuanyang Lake

Table 1. Vegetation composition of the Yuanyang Lake forest.

Species name Relative coverage, % Relative density, % Dominance, %

Chamaecyparis obtusa formosana 38.87 3.36 21.11

Tsuga chinensis formosana 40.92 0.39 20.65

Illicium philippinense 0.78 7.29 4.03

Rhododendrum formosanum 0.09 6.11 3.10

Schefflera taiwaniana 2.01 4.32 3.17

Dendropanax pellucidopunctata 0.13 4.57 2.35

Barthea formosana 1.31 3.44 2.37

Adinandra lasiostyla 0.23 3.33 1.78

Illex pedunculosa 0.14 2.72 1.43

Neolitsea acuminatissima 0.52 2.44 1.48

Skimmia arisanensis 0.68 2.32 1.50

Eurya leptophylla 0.09 2.48 1.29

Eurya glaberrima 0.18 2.03 1.10

Vaccinium randaiense 0.42 1.61 1.01

Elaeocarpus japonicus 0.67 1.20 0.93

Neolitsea variabillima 0.53 1.04 0.79

Daphniphyllum himalaense 1.12 0.64 0.88

Creptomeria japonica 0.19 0.98 0.59

Ternstroemia gymnanthera 1.99 0.21 1.10

Ilex sugeroki brevipedunculata 0.63 0.64 0.64

Viburnum furcatum 1.27 0.37 0.82

Ardisia crenata 0.55 0.57 0.56

Trochodendron aralioides 0.37 0.59 0.48

Symplocos anomala 0.50 0.42 0.46

Symplocos lancifolia 0.07 0.57 0.32

Stranvaesia niitakayamensis 0.18 1.00 0.59

Ilex hayataiana 0.54 0.38 0.46

Eurya strigillosa 0.15 0.51 0.33

Prunus takasagomontana 0.02 0.41 0.21

Osmanthus heterophyllus 0.51 0.20 0.35

Viburnum foetidum 0.67 0.11 0.39

Photinia beauverdiana 0.05 0.33 0.19

Acer morisonensis 0.66 0.09 0.37

Lasianthus japonicus 0.04 0.29 0.16

Rhododendron ellipticum 0.01 0.26 0.13

Viburnum taiwanianum 0.61 0.01 0.31

Litsea mushaensis 0.03 0.21 0.12

Symplocos lucida 0.14 0.15 0.14

Damnacanthus angustifolius 0.15 0.12 0.13

Litsea cubeba 0.43 0.01 0.22

Rhododendron morii 0.26 0.07 0.16

Rhododendron mariesii 0.37 0.01 0.19

Ligustrum japonicum 0.01 0.13 0.07

Machilus japonica 0.25 0.03 0.14

Lindera thunbergii 0.01 0.12 0.06

Daphne arisanensis 0.04 0.10 0.07

Lonicera apodonta 0.01 0.11 0.06

Pieris taiwanensis 0.07 0.08 0.08

Rhaphiolepis indica tashiroi 0.21 0.01 0.11

Rhamnus crenata 0.08 0.05 0.07

Symplocos heishanensis 0.05 0.04 0.04

Ilex yunnanensis parvifolia 0.02 0.04 0.03

Microtropis fokienensis 0.01 0.03 0.02

Machilus thunbergii 0.05 0.01 0.03

Pittosporum illicioides 0.02 0.03 0.02

Symplocos stellaris 0.01 0.03 0.02

Ilex lonicerifolia hakkuensis 0.04 0.01 0.02

Ilex tsugitakayamensis 0.04 0.01 0.02

Acer palmatum pubscence 0.01 0.01 0.01

Ilex suzukii 0.02 0.01 0.02

Ilex goshiensis 0.01 0.01 0.01

Itea oldhamii 0.01 0.01 0.01

Total 100.00 100.00 100.00

Botanical Bulletin of Academia Sinica, Vol. 41, 2000

Elevation above lake surface. A negative value indicates a submerged plant, while a positive value indicates a terrestrial plant. These data were used to classify vegetation patterns of the plant community in the YYL forest ecosystem.

Results

Floristic Composition of the YYL Forest

Based on the data of relative coverage, relative density, and dominance value (DV), the order of dominance among plants in the YYL area is given in Table 1. It shows that Chamaecyparis obtusa var. formosana and Tsuga chinese are predominant species with dominance over 20%. Floristically there are 185 species in 115 genera and 71 families. Pteridophytes comprise 33 species in 23 genera and 14 families. Gymnosperms comprise 4 species in 3 genera and 3 families. Regarding dicots, there are, 108 species in 70 genera and 46 families; while for monocots there are 22 species in 19 genera and 8 families. The most common plants found in the area include 7 species of Polypodiaceae (pteridophytes), 9 species of Rosaceae, 8 species of Aquifoliaceae, and 10 species of Ericaceae. These plants are representative of warm temperate flora; however, the most abundant warm temperate plants in Taiwan, such as Lauraceae and Fagaceae, were scarcely present in the area. A comparison of plants of YYL with those of neighboring areas, such as Fushan, was made. The number of species in Lauraceae and Fagaceae was much lower in the YYL area than in the Fushan area, suggesting that the dominant species, such as Chamaecyparis and Rhododendron, took over Lauraceae and Fagaceae.

Figure 3. The cluster formation of sampling stands at the Yuanyang Lake site between the X and Z axes based on DCA analysis. The designations I, II, III, IV, V, and VI are the same as Figure 2.

Vegetation Analysis

Statistical analysis of TWINSPAN reveals that the plant community in the YYL area can be divided into two major sub-communities in the first run of computing, namely, a forest community and a swamp or early succession plant community (Table 2). In the second computing run, the forest community then can be divided into two groups, Chamaecyparis spp. (natural vegetation) and Cryptomeria joponica (plantation). The forest community can be grouped into two subtypes: Chamaecyparis—Rhododendron type and Chamaecyparis—Tsuga type (Table 2). On the other hand, the swamp vegetation can be divided into two groups, submerged hydrophytes (e.g., Potamogeton octandrus) and emergent hydrophytes (e.g., Schoenoplectus mucronatus and Sparganium fallax). Miscanthus transmorrisonesis was out of the S. mucronatus group.

By using DCA analysis, the data can be formed into three axes, representing three dimensions based on environmental factors mentioned previously. This is shown in Tables 3 and 4. The correlation between the X axis and environmental factors was significant, but a negative correlation was revealed with slope, altitude, content of sand, and distance from lake surface. However, the other two axes, Y and Z, were not statistically correlated to the environmental factors given. Therefore, if the correlation is based on the X and Y axis, two distinct communities are shown (Figure 2). Plots 1-11 belong to A group, comprising types I and II, while plots 12-36 belong to B group comprising types III, IV, V, and VI. Furthermore, correlation between the X and Z axes also reveals two community sub-groups (Figure 3), in which vegetation patterns are similar to that of Figure 2. These findings conclude that six vegetation types are represented in the YYL plant community.

Figure 2. The cluster formation of sampling plots at the YYL site between the X and Y axes based on DCA analysis. The designations of plots are: I, Stands of Chamaecyparis obtusa var. formosana and its association; II, Stands of Cryptomeria japonica plantation; III, Stands of dominant community of Miscanthus transmorrisonensis; IV, Stands of submerged plants community; V, Stands of emergent hydrophyte dominated by Sparganium fallax and scattered by Schoenoplectus mucronatus; VI, Stands of dominant community of Schenoplectus mucronatus.

Chou et al. — Vegetation composition of Yuanyang Lake

Table 2. The vegetation types of species distribution in the Yuanyang Lake forest community. The data were analyzed by TWINSPAN method.

Vegetation type

I II III IV V VI

Species name Sampling plot

000 00000 011 11111 112223 222 3322233 1233

378 24561 901 23456 899796 246 0201315 7534

Elaeocarpus japonicus 111 12212 --- ----- ------ --- ------- ---- 000011

Myrsin stolonifera -1- 111-1 --- ----- ------ --- ------- ---- 000011

Tsuga chinensis formosana 556 5---- --- ----- ------ --- ------- ---- 000100

Monachosorum henryi 131 ----1 --- ----- ------ --- ------- ---- 000100

Yushania niitakayamensis -58 ----- --- ----- ------ --- ------- ---- 000100

Neolitsea acuminatissima 545 31133 2-2 ----- ------ --- ------- ---- 000101

Oxalis acetosella japonica 23- ---31 --1 ----- ------ --- ------- ---- 000101

Pleione formosana 4-- 2---- --1 ----- ------ --- ------- ---- 000101

Polypodium amoenum 2-1 12-1- -1- ----- ------ --- ------- ---- 000110

Ilex hayataiana 111 1--21 -1- ----- ------ --- ------- ---- 000111

Viburnum furcatum 132 22332 111 ----- ------ --- ------- ---- 000111

Lyonia ovalifolia lanceolata 13- 31211 -11 ----- ------ --- ------- ---- 000111

Ternstroemia gymnanthera 212 32213 -11 ----- ------ --- ------- ---- 000111

Xiphopteris okuboi 111 11113 --- ----- ------ --- ------- ---- 000111

Vittaria flexuosa 11- 111-4 --1 ----- ------ --- ------- ---- 000111

Shortia exappendiculata 212 43141 --2 ----- ------ --- ------- ---- 000111

Nertera nigricarpa 111 11111 --- ----- ------ --- ------- ---- 000111

Skimmia arisanensis 321 44322 111 ----- ------ --- ------- ---- 000111

Schefflera taiwaniana 425 43524 455 ----- ------ --- ------- ---- 001000

Vaccinium randaiense -11 ----2 -11 ----- ------ --- ------- ---- 001000

Symplocos anomala 211 2--11 11- ----- ------ --- ------- ---- 001000

Araiostegia perdurans 221 111-- -21 ----- ------ --- ------- ---- 001000

Rhus orientalis 121 11111 112 ----- ------ --- ------- ---- 001000

Asarum macranthum 22- 1-111 211 ----- ------ --- ------- ---- 001000

Rhododendron kawakamii -11 -11-1 -11 ----- ------ --- ------- ---- 001000

Vaccinium japonicum lasiostemon 131 11111 -11 ----- ------ --- ------- ---- 001000

Rubus pectinellus 43- ----1 1-2 ----- ------ --- ------- ---- 001000

Daphne arisanensis 111 1--11 1-1 ----- ------ --- ------- ---- 001000

Chamaecyparis obtusa formosana 777 67777 -56 ----- ------ --- ------- ---- 001001

Illicium philippinensis 626 54565 466 ----- ------ --- ------- ---- 001001

Barthea formosana 354 25545 223 ----- ------ --- ------- ---- 001001

Adinandra lasiostyla 423 33534 323 ----- ------ --- ------- ---- 001001

Mecodium polyanthos 553 35364 355 ----- ------ --- ------- ---- 001001

Elaphoglassum conforme 11- 11211 11- ----- ------ --- ------- ---- 001001

Plagiogyria euphlebia 553 46654 656 ----- ------ --- ------- ---- 001001

Arthromeris lehmanni 111 11321 111 ----- ------ --- ------- ---- 001001

Ainsliaea reflexa 11- 111-- -11 ----- ------ --- ------- ---- 001001

Vaccinium merrillianum 2-2 31111 -13 ----- ------ --- ------- ---- 001001

Tripterospermum lanceolatum 1-1 11111 -11 ----- ------ --- ------- ---- 001001

Sarcopyramis delicata 432 13641 253 ----- ------ --- ------- ---- 001001

Ardisia japonica 511 36552 235 ----- ------ --- ------- ---- 001001

Damnacanthus angustifolius 1-1 1111- 111 ----- ------ --- ------- ---- 001001

Pellionia trilobulata 56- 32551 214 ----- ------ --- ------- ---- 001001

Smilacina formosana 11- 111-- -11 ----- ------ --- ------- ---- 001001

Neolitsea variabillima -42 -41-- 321 ----- ------ --- ------- ---- 00101

Lycopodium serratum longipetiolatum --- -1311 11- ----- ------ --- ------- ---- 00101

Rhododendron formosanum 162 65565 --4 ----- ------ 6-6 ------- ---- 0011

Viburnum taiwanianum 2-1 111-1 121 ----- ------ --- ------- ---- 01000

Symplocos lancifolia --1 -1111 21- ----- ------ --- ------- ---- 010010

Ophiopogon japonica 22- 14331 444 ----- ------ --- ------- ---- 010010

Ilex pedunculosa 111 11111 -34 ----- ------ --- ------- ---- 010011

Ilex sugeroki brevipedunculata 112 11221 223 ----- ------ --- ------- ---- 010011

Dendropanax pellucidopunctata 344 35223 256 3---- ------ --- ------- ---- 010011

Botanical Bulletin of Academia Sinica, Vol. 41, 2000

Table 2. (Continued)

Vegetation type

I II III IV V VI

Species name Sampling plot

000 00000 011 11111 112223 222 3322233 1233

378 24561 901 23456 899796 246 0201315 7534

Viburnum foetidum rectangulatum 111 1111- 331 ----- ------ --- ------- ---- 010011

Osmanthus heterophyllus bibracteatus 3-1 -1--- 211 ----- ------ --- ------- ---- 010011

Eurya glaberrima 113 11-31 643 ----- ------ --- ------- ---- 010011

Berberis kawakamii 2-- 111-1 121 ----- ------ --- ------- ---- 010011

Rubus liuii 11- 1-2-1 231 ----- ------ --- ------- ---- 010011

Nertera depressa 111 211-1 223 ----- ------ --- ------- ---- 010011

Pellionia arisanensis -4- ----- 5-- ----- ------ --- ------- ---- 010011

Smilax sp. 111 11111 411 ----- ------ --- ------- ---- 010011

Cryptomeria japonica --- ----- 766 ----- ------ --- ------- ---- 010100

Daphniphyllum himalaense macropodum 1-1 11-1- 542 ----- ------ --- ------- ---- 010100

Vaccinium dulanianum caudatifolium --- ----1 122 ----- ------ --- ------- ---- 010100

Stranvaesia niitakayamensis 1-1 1---1 343 ----- ------ --- ------- ---- 010100

Symplocos lucida 1-- ----- 423 ----- ------ --- ------- ---- 010100

Trochodendron aralioides --- ---11 451 ----- ------ --- ------- ---- 010100

Peranema cyatheoides --- ----1 342 ----- ------ --- ------- ---- 010100

Diplopterygium glaucum --2 -2--1 454 ----- ------ --- ------- ---- 010100

Plagiogyria stenoptera --- ----1 113 ----- ------ --- ------- ---- 010100

Hydrangia integrifolia 11- --1-- 4-1 ----- ------ --- ------- ---- 010100

Ligustrum japonicum --- 2---- 321 ----- ------ --- ------- ---- 01011

Akebia chingshuiensis --- -11-- 321 ----- ------ --- ------- ---- 01011

Eurya leptophylla 214 12212 554 -4-5- ------ --- ------- ---- 011

Lonicera acuminata 111 111-1 111 ----3 ------ --- ------- ---- 011

Coptis quinquefolia 421 34331 113 -55-- ------ --- ------- ---- 011

Prunus tagasagomontana 111 1-1-- 211 ----- ------ --- ------- ---- 10

Rhododendron mariesii --- -1-5- --- 5---- ------ --- ------- ---- 110

Rubus shinkoensis 121 -1111 211 5--54 ------ --- ------- ---- 110

Arisaema consanguineum 1-- 1-11- --- ----4 ------ --- ------- ---- 110

Potemogeton octandrus --- ----- --- ----- 3----- --- ------- 9599 11100

Viburnum matsudai --- ----- --- 33--- ------ --- ------- ---- 111010

Hydrangea paniculata --- ----- --- 63353 ------ --- ------- 4--- 111010

Baeothryon subcapitatum --- ----- --- 88777 ------ --- ------- ---- 111010

Carex sp. 1-- ----- 21- -56-3 ------ --- ------- ---- 111010

Parathelypteris japonica --- -11-- -2- -4-5- --3--- --- ------- ---- 111011

Schoenoplectus mucronatus robustus --- ----- --- -5764 888888 588 --58-5- 5--- 11110

Miscanthus transmorrisonensis --- ----- 454 88788 566334 766 6665 --- 5--- 11110

Alnus formosana --- ----1 --- ----- 4----- --- ------- ---- 111110

Rhododendron ellipticum --- -1-1- --- ----- ----7- --- ------- ---- 111110

Vaccinium bracteatum --- -1--- --- ----- ------ 4-- ------- ---- 111110

Machilus japonica --- ----1 --- ----- ------ -76 ------- ---- 111110

Polygonum dichotomum --- ----- --- ----3 6777-7 -53 5------ ---- 111110

Polygonum thunbergii biconvex --- ----- --- ----6 565565 -6- ------- ---- 111110

Rosa taiwanensis --- ----- -1- ----4 5----- -46 ------- ---- 111110

Galium trifidum --- ----- --- ----- 64-776 44- ------- ---- 111110

Hydrocotyle nepalensis --- ---2- --- ----- ---667 --3 ------- ---- 111110

Carex onoei --- ----- --- ----- --5-33 --- ------- ---- 111110

Juncus effusus decipiens --- ----- -2- ----- 6-4--- --- ------- ---- 111110

Sparganium fallax --- ----- --- ----- ----3- 663 9999999 69 -- 111111

000 00000 000 11111 111111 111 1111111 1111

000 00000 111 00000 000000 000 0000000 1111

000 11111 00000 111111 111 1111111

00001 00001 000000 000 1111111

000000 111 0011111

000111 00111

Chou et al. — Vegetation composition of Yuanyang Lake

Vegetation Types

Based on the analysis of DCA of the aforementioned 36 sampling plots, two plant communities with six vegetation types are described as follows:

Community A. Forest community. The forest community comprises two vegetation types.

Type I: Chamaecyparis obtusa var. formosana and its associates.

Chamaecyparis obtusa appeared in plots 1-8. They were tall and distributed from the lake side up to mountain summit. The tree height was above 20 m and classified as T1 layer, where Chamaecyparis obtusa var. formosana was the dominant species and Tsuga chinensis

Table 3. Information of eight environmental parameters for each stand at the YYL sites.

Environmental parameter^a

Stand No. FSL DSS Aspect Slope Topography Elevation Stoniness DLS

1 57 72 4 40 4 1700 30 28

2 75 88 7 13 6 1900 10 228

3 63 72 7 6 5 2000 5 328

4 51 64 7 25 3 1800 28 128

5 33 29 7 40 3 1685 35 13

6 60 71 8 22 4 1725 0 153

7 52 51 8 38 6 1930 15 258

8 66 74 1 6 5 1900 3 228

9 55 81 1 35 4 1870 19 198

10 60 76 1 26 4 1820 15 148

11 52 62 3 25 4 1850 15 178

12 57 75 1 0 2 1675 0 2

13 53 60 1 4 2 1675 0 2

14 53 69 1 3 2 1675 0 3

15 59 75 1 0 2 1675 0 2

16 59 70 1 0 2 1675 0 2

17 65 79 1 0 1 1672 0 -2.2

18 63 78 1 0 1 1672 0 -0.6

19 59 76 1 0 1 1672 0 -0.8

20 51 58 1 0 1 1672 0 -1

21 60 80 1 0 1 1672 0 -0.9

22 51 61 1 0 1 1672 0 -0.9

23 58 74 1 0 1 1672 0 -1.1

24 59 76 1 0 1 1672 0 -0.8

25 58 73 1 0 1 1672 0 -1

26 57 73 1 0 1 1672 0 -0.7

27 57 77 1 0 1 1672 0 -0.3

28 60 77 1 0 1 1672 0 -0.3

29 56 73 1 0 1 1672 0 -0.8

30 59 74 1 0 1 1672 0 -1

31 55 68 1 0 1 1672 0 -1.1

32 55 72 1 0 1 1672 0 -1.4

33 59 70 1 0 1 1672 0 -2.1

34 56 70 1 0 1 1672 0 -2.4

35 61 77 1 0 1 1672 0 -1.3

36 61 79 1 0 1 1672 0 -0.5

^aThe abbreviation of parameters are: FSL=Full sky light space; DSS=Direct sky light space; DLS=Distance from lake surface.

Table 4. Correlation between environmental axis and environmental parameter.

Environment parameter^b

Environmental axis^a FSL DSL Slope Elevation Stoniness DLS

X 0.097 0.255 -0.811 -0.773 -0.723 -0.802

Y -0.113 -0.109 0.042 0.035 0.042 0.033

Z 0.059 0.172 -0.191 -0.173 -0.200 -0.217

^aX, Y, Z: indicates the dimension of environmental factor.

^bAbbreviations of environmental parameters are: FSL=Full sky light space; DSL=Direct sky light space; DLS=Distance from lake surface.

Botanical Bulletin of Academia Sinica, Vol. 41, 2000

var. formosana was the second dominant. However, Tsuga chinensis var. formosana was distributed only in higher elevation above 2,500 m. On the other hand, tree height between 10 and 20 meters was classified as T2 layer. Trees of Lauraceae and Fagaceae were grouped into T2 layer. These plants, however, were scarce in the YYL site.

Trees below 10 m height were classified as T3 layer and distributed in the area around the lakeside, where Illicium philippinense and Rhododendron formosanum were predominant. Other common trees are Neolitsea cuminatissima, Schefflera taiwaniana, Barthea formosana, Ternstroemia gymnanthera, Adinandra formosanum, Damnacanthus angustifslius, Dendropanax pellcidopunctata and Skimumia arisamensis (Figure 4). Grassland species are Miscanthus transmorrisonensis, Plagiogyria glauca var. philippinensis, Coptis quinquefolia, Ardisia japonica, Asarum spp., Pellionia trilobulata. Epiphytes are Mecodium polyanthos and Sarcopyramis delicata. Vine tree is dominated by Smilax spp.

Type II: Cryptomeria japonica plantation.

Regarding type II of Cryptomeria and plantation trees, plots 9, 10 and 11 are distributed in the eastern range area of the YYL natural preserve. Forest plantation, such as Cryptomeria joponica was dominant but substantial old deforested Chamaecyparis trees were still there. Several native species have gradually reappeared in the area.

These native species include Chamaecyparis formosensis, C. obtusa var. formosana, Viburnum furcatum, Skimmia arisanensis, Illicium philippinense, Symplocos anomala, Barthea formosana, Ilex sugeroki var. brevipedunculata, Dendropanax pellcidopunctata, Berberis Kawakamii, Daphniphyllum himalaense subsp. macropodum, Symplocos lucida, Eurya glaberrima, Trochodendron aralioides, Vaccinium dunaliannum var. caudatifolium, Ligustrum japonicum and Shefflera taiwaniana.

Community B. Aquatic and grassland community.

The aquatic and grassland community appeared in the lake and swamp area around the lake. Based on DCA analysis, four types of vegetation are recognized:

Type III: Miscanthus transmorrisonensis.

Type III vegetation is represented by M. transmorrisonensis based on sampling plots 12, 13, 14, 15, and 16. The vegetation was the dominant species in marsh area, and the mean coverage was above 5% of the area. The other common species were Carex onoei, Baeothryon subcapitatum, and Juncus effusus var. decipiens, which were typical marsh plants. Other Gramminae occupied only a small area with relatively low coverage. There were a few shrubs, such as Hydrangia paniculata (most common), Rhamnus crenata and Alnus formosana.

Type IV: Potamogeton octandrus.

Figure 4. A general diagram of the forest community in the area of the Yuanyang Lake .

Chou et al. — Vegetation composition of Yuanyang Lake

Potamogeton octandrus appeared in plots 17, 25, 33, and 34 and was a submerged plant. Its leaves floated on the lake water.

Type V: Sparganium fallax.

Sparganium fallax appeared in plots 20, 21, 23, 30, 32, 31, and 35 and was an emergent hydrophyte. It grew mostly along the lakeside. Sparganium fallax was dominant at the site, and Schoenoplectus mucronata was scattered throughout the stand of S. fallax.

Type VI: Schoenoplectus mucronatus.

Schoenoplectus mucronatus appeared in plots 18, 19, 22, 24, 26, 27, 28, 29, 36. It was an emergent hydrophyte, frequently forming a pure stand. It was also found in the surrounding swamp. The associated species are Polygonum dichotomum, Polygonum thunbergii f. biconvexum, Hydrocotyle nepalensis, and Galium trifidum. This vegetation type often forms two subtypes, namely the Schoenoplectus-Polygonum subtype and the Schoenoplectus-Sparganium subtype based on the population size of Polygonum thunbergii.

The growth habitat of vegetation types IV, V and VI can be contrasted as follows: Potamogeton octandrus grows in deep water; Schoenoplectus grows in the shallow water; and Sparganium fallax grows in between.

Regeneration of Chamecyparis obstusa var. formosana Trees in YYL Forest

We measured the diameter at breast height (DBH) of all Chamaecyparis trees in 0.8 ha of the forest at the YYL. Results based on 5 cm set of diameter are given in Figure 5. It shows that the number of individuals with a 5 cm diameter is the highest (118), while the number of individual trees with 50, 10, and 45 cm diameters is less than 20. Only four trees have diameter over 70 cm, and only about one or two trees with diameter over 90 cm were found (Figure 5). This fact indicates that the forest is relatively mature and that the cypress trees are regenerating and sustainable as a dominant community there. The young (less than 10-year old) cypress trees were abundant although some old trees were also present. That lack of old trees could

Figure 5. Number of plants of Chamaecyparis obtusa var. formosana per hectare based on the stem diameter at breast height at the Yuanyang Lake site.

be due to some physical factors, such as shallow soil and frequent typhoons. An old cypress tree was destroyed and broken in half by a thunderstorm in 1994.

Successional Trend in the YYL Forest

Most alpine lakes contain organic debris or other matter coming from the upper stream to a narrow creek mouth. The continuous accumulation of deposition causes the lakeside to become shallow and aquatic plants gradually invaded the land. A hydrosere will occur at all alpine lakes if organic debris is allowed to continuously deposit. The present vegetation of aquatic plants occurring in the center and surrounding lake is obvious. The succession has begun from the east and southwest side of the lake where the creek passes through. Potamogeton octandrus (submerged plant), Schoeneplectus mucronatus and Sparganium fallax (both are emergent hydrophyte) are pioneer species growing in the area. In the second stage of plant succession, Miscanthus transmorrisonensis and Alnus formosana become dominant, and in the final successional stage the Chamaecyparis species becomes dominant. The cypress trees and seedlings are found everywhere, indicating a regeneration by natural reseeding has occurred. A proposed pathway of the succes

Figure 6. A proposed succession trend of the Yuanyang Lake forest community.

Botanical Bulletin of Academia Sinica, Vol. 41, 2000

sional trend of vegetation at the Yuenyang Lake forest is given in Figure 6. Our findings are very much in agreement with that of Moir (1992), who stated that an old growth forest should possess big fallen trees or dead trees with a large diameter, and large vine trees as well.

Discussion

In the YYL forest community, many dead and fallen trees of Chamaecyparis obtusa var. formosana were found. Many seedlings of this plant grew luxuriantly on the decaying wood and in open areas. It has been reported that the cypress forest has been there for many thousands of years and has become a climax vegetation (Chang, 1963; Liu and Hsu, 1973; Liu, 1975). Chen and Yang (1996) further indicated that pollen of Chamaecyparis have been dominant for 3,000 years. They also found pollen of the Fagaceae species at around 3,000, 2,500, 1,800, 1,380 and 300 years ago, indicating that the climate change led temperatures to rise temporarily. The rise of temperature is presumably favorable for the growth of hardwood forests, such as Fagaceae and Lauraceae; however, these plants were not dominant due to the short duration of temperature rise. Consequently, the Chamaecyparis seedlings established themselves in the open gap area where the hardwood forest died. In the present study, we did not find plants of Fagaceae and Lauraceae, which are dominant at similar altitudes, at other places in Taiwan. This fact reflects that the climatic and edaphic development might have been stable for many thousands of years and the trees of Chamaecyparis species have been able to resist the invasion of other species. Many recent workers have reported that the productivity of Chamaecyaris plants has reached its maximum and is stablized at the YYL area. The aforementioned evidence may lead one to conclude that the YYL site is favorable to the growth of Chamaecyparis plants, which might reach a climax stage as defined by Clements (1936) and Daubenmire (1968).

One of the nature preserve’s naturalized and rare species is Sparganium fallax, which is native to northeast China. The plants may have been introduced by birds to YYL and some other alpine lakes or swamp land, such as Nantau (1,150 m in elevation), Fushan pond (700 m), Shenmi lake (1,000-1,150 m) or Taolin (1,300 m) in Taiwan. These areas are favorable for the growth of Fagaceae trees. However, Sparganium growing in the lake or swamp area can be regarded as an important indicator plant. The adaptive mechanisms of Sparganium were studied by Hwang and his associates (1996). Other physiological ecology studies conducted by Lee et al. (1996a and b) concluded that abscisic acid and putresine played an important role in the plant growth of Schoenoplectus mucronata (Scirpus mucronatus). Furthermore, these plants could grow in water of rather high acidity (pH 3.5-4.5), indicating that a good adaptive strategy of plant growth could be developed. We have conducted an alleopathic study on the dominant species of Sparganium, which revealed allelopathic potential (Chou, unpublished data). Chou (1993) indicated that allelopathy is an important species survival

strategy when the plant grows under a stressful environment. Further clarification of this, however, is needed.

The aforementioned findings conclude that the cypress forests of Chamaecyparis and its related species are stable and can self-regenerate due to the favorable weather conditions of high humidity and low temperature. Chamaecyparis obtusa var. formosanus, Tsuga chinese, Illicium philippinense, Schefflera taiwaniana, and Rhododendron formosanum are the top five dominant forest species (Table 1), while Potamogeton octandrus, Sparganium fallax, Schoenoplectus mucronntus, and Miscanthus transmorrisonensis are the most dominant species in the YYL and its surrounding swamp area. These plants form a plant community of six major vegetation types, which is unique among alpine lakes and very different from other areas of subtropical forest at the same altitude in Asia. The unique, unspoiled YYL ecosystem is significant for performing long-term research. Permanent plots need to be established in order to elucidate the structure and function of the alpine lake forest ecosystem and to provide valuable information about ecological processes that help forest management.

Acknowledgement. The authors express their sincere appreciation to the Department of Forest Management, Veterans Affairs Commission, Executive Yuan, Taiwan for providing field assistance in the course of the study.

Literature Cited

Billings, W.D. 1952. The environmental complex in relation to plant growth and distribution. Quart. Rev. Biol. 27: 261-265.

Chang, L.M. 1963. Ecological Studies of Chamaecyparis formosensis and C. taiwanensis Mixed Forest in Taiwan. Bull. Taiwan Forest. Res. Inst. No. 91. Taipei.

Chen, S.H. and Y.L. Yang. 1996. Study of vegetation history around Yuan-Yang Lake. The Joint Sym. On Taiwan Quaternary (6) and on Investigation of Subsurface Geology and Engineering Environment of Taipei Basin, pp. 257-260.

Chen, Y.H. 1996. Studies on the vegetation ecology of a watershed along the upper researches of the Dona Wenchuan River, Liukuei Taiwan. J. Forest. Sci. 11(3): 275-287.

Chou, C.H. 1993. The role of allelopathy in plant diversity of plant communities in Taiwan. Bot. Bull. Acad. Sin. 34: 211-221.

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Curtis, J.T. and R.P. McIntosh. 1951. An Upland Forest Community in the Prairie-Forest Border Region of Wisconsin. Ecology 32: 476-496.

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Hill, M.O. 1979. TWINSPAN- A FORTRAN Program for Arranging Multivariate Data in an Ordered Two-Way Table by Classification of the Individuals and Attributes. Cornell

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Hwang, Y.H., C.W. Fan, and M.H. Yin. 1996. Primary production and chemical composition of emergent aquatic macrophytes, Schoenoplectus mucronatus ssp. robustus and Sparganium fallax, in Lake Yuanyang, Taiwan. Bot. Bull. Acad. Sin. 37: 265-273.

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Botanical Bulletin of Academia Sinica, Vol. 41, 2000

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