ARTÍCULO

Plant species and communities in Poyang Lake, the largest freshwater lake in China

H.-F. WANG (王华锋)¹, M.-X. REN (任明迅)², J. LÓPEZ PUJOL³, C. ROSS FRIEDMAN⁴, L. H. FRASER⁴ & G.-X. HUANG (黄国鲜)¹

¹ Key Laboratory of Protection and Development Utilization of Tropical Crop Germplasm Resource, Ministry of Education,
College of Horticulture and Landscape Agriculture, Hainan University, CN-570228 Haikou, China
² College of Horticulture and Landscape Architecture, Hainan University, CN-570228 Haikou, China
³ Botanic Institute of Barcelona (IBB-CSIC-ICUB), pg. del Migdia s/n, ES-08038 Barcelona, Spain
⁴ Department of Biological Sciences, Thompson Rivers University, 900 McGill Road, CA-V2C 0C8 Kamloops,
British Columbia, Canada

Author for correspondence: H.-F. Wang (huafengw82@163.com)

Editor: J. J. Aldasoro

ABSTRACT
Plant species and communities in Poyang Lake, the largest freshwater lake in China.— Studying plant species richness and composition of a wetland is essential when estimating its ecological importance and ecosystem services, especially if a particular wetland is subjected to human disturbances. Poyang Lake, located in the middle reaches of Yangtze River (central China), constitutes the largest freshwater lake of the country. It harbours high biodiversity and provides important habitat for local wildlife. A dam that will maintain the water capacity in Poyang Lake is currently being planned. However, the local biodiversity and the likely effects of this dam on the biodiversity (especially on the endemic and rare plants) have not been thoroughly examined. Therefore, in order to assess the richness of plant species and plant communities in Poyang Lake, we conducted a detailed field investigation combined with a literature review. A total of 124 families, 339 genera, and 512 species (including sub-species, varieties and forms) as well as eight dominant plant communities were identified, confirming the lake’s wetland as a regional hotspot of plant diversity. It is imperative to carry out further research on the impact of damming on the vegetation, particularly research focusing on protecting local biodiversity, maintaining the lake’s ecosystem services, controlling the spread of invasive species, and restoring degraded ecosystems.
KEYWORDS: conservation; dam; plant diversity; species richness; Yangtze River.

Especies y comunidades vegetales del lago Poyang, el lago de agua dulce más grande de China

RESUMEN
Especies y comunidades vegetales del lago Poyang, el lago de agua dulce más grande de China.— El estudio de la riqueza y la composición de especies vegetales de un humedal es esencial a la hora de estimar su importancia ecológica y sus servicios ecosistémicos, especialmente cuando éste está sujeto a perturbaciones humanas. El lago Poyang, situado en el curso medio del río Yangtsé (China central) constituye la mayor superfície de agua dulce del país. Alberga una elevada biodiversidad y proporciona hábitats importantes para la flora y fauna locales. En la actualidad existen planes de construir una presa que mantendrá el volumen de agua del lago estable. Sin embargo, y hasta la fecha, apenas existen estudios que hayan abordado la biodiversidad del lago y los posibles efectos negativos de la presa sobre ésta (y en especial sobre las especies endémicas y raras). Así pues, se ha llevado a cabo una intensa campaña de campo combinada con una búsqueda bibliográfica con el objetivo de evaluar la riqueza de especies y comunidades vegetales del lago Poyang y sus humedales asociados. Se han identificado un total de 124 familias, 339 géneros y 512 especies (incluyendo subespecies, variedades y formas) así como ocho comunidades vegetales dominantes, confirmándose así el papel de los humedales del lago Poyang como hotspot regional de biodiversidad. Resulta imperativo estudiar los efectos del represado sobre la vegetación, y, de manera especial, todo aquello concerniente a la protección de la biodiversidad local, el mantenimiento de los servicios ecosistémicos, el control de las especies invasoras y la restauración de los ecosistemas degradados.
PALABRAS CLAVE: conservación; diversidad vegetal; presa; río Yangtsé; riqueza de especies.

摘要
中国最大淡水湖泊鄱阳湖的植物物种和群落。— 研究湿地的植物丰富度和组成对评估其生态重要性和生态系统服务功能很有必要，特别是对于那些受人类干扰的湿地。位于中国长江中游的鄱阳湖是中国最大的淡水湖，其生物多样性较高，同时也是当地野生动物的重要栖息地。目前，为了维持鄱阳湖的水容量，中国相关部门正在计划修建一个大坝。然而，鄱阳湖的生物多样性本底情况还不清楚，大坝对当地生物多样性（特别是珍稀植物）可能产生的潜在影响也还没有查清。为了评估鄱阳湖植物物种和群落的丰富度，我们进行了详尽的野外调查和相关文献分析。研究发现：鄱阳湖湿地植物分属124科，339属，512种（包括亚种，变种和变型）以及八种主要的植物群落，进一步确认了鄱阳湖湿地是区域性的植物多样性热点地区。水坝对鄱阳湖湿地植物与群落的影响研究势在必行，尤其应聚焦于保护当地的生物多样性、维持湖泊的生态系统服务、控制外来入侵物种传播、恢复退化生态系统这四个方面。
关键词：保护；大坝；植物多样性；物种丰富度；长江。

CONTENIDOS

INTRODUCTIONTop

During the past century, approximately fifty percent of the world’s wetlands have been destroyed, largely as a result of human activities (UNWWAP, 2003UNWWAP (United Nations World Water Assessment Programme) 2003. Water for people, water for life. United Nations Educational, Scientific and Cultural Organization (UNESCO) & Berghahn Books, New York.; Fraser & Keddy, 2005Fraser L. H. & Keddy P. A. 2005. The World’s largest wetlands: Ecology and conservation. Cambridge University Press, Cambridge. http://dx.doi.org/10.1017/CBO9780511542091). An increased human population coupled with habitat loss and fragmentation has led to shrinkage of wetland areas, and data show that as they decrease, their key functions decline (Fraser & Keddy, 2005Fraser L. H. & Keddy P. A. 2005. The World’s largest wetlands: Ecology and conservation. Cambridge University Press, Cambridge. http://dx.doi.org/10.1017/CBO9780511542091). Reduced wetland area does not only cause more flooding in spring, less available water during drought, greater risk of water pollution, less food production, and reduced carbon storage, but also leads to the loss of habitats for many animals and plants and the loss of wetland’s capacity for regulating the regional climate (MEA, 2005MEA (Millennium Ecosystem Assessment) 2005. Ecosystems and human well-being: Wetlands and water synthesis. World Resources Institute, Washington.; Ramsar, 2011Ramsar 2011. Wetland ecosystem services. The Ramsar Convention on Wetlands. Retrieved December 18, 2011, from http://www.ramsar.org/cda/en/ramsar-pubs-info-ecosystem-services/main/ramsar/1-30-103%5E24258_4000_0_). Much of the remaining pristine wetland systems are found in the world’s largest wetlands, and yet these areas have been subjected to surprisingly little scientific research (Fraser & Keddy, 2005Fraser L. H. & Keddy P. A. 2005. The World’s largest wetlands: Ecology and conservation. Cambridge University Press, Cambridge. http://dx.doi.org/10.1017/CBO9780511542091). Therefore, studying the floristic richness and composition of a given wetland is essential when a major human impact is expected to take place, especially if it is known that endemic and threatened plants are present. Such a study is a mandatory preliminary step in order to implement adequate conservation measures.

The middle reaches of the Yangtze River is an extensive network of rivers, shallow lakes and wetlands, and constitutes one of the main Asian hotspots of biodiversity (Olson & Dinerstein, 2002Olson, D.M. & Dinerstein, E. 2002. The Global 200: priority ecoregions for global conservation. Annals of the Missouri Botanical Garden 89: 199–224. http://dx.doi.org/10.2307/3298564; Xie, 2003Xie, Z. 2003. Characteristics and conservation priority of threatened plants in the Yangtze valley. Biodiversity and Conservation 12: 65–72. http://dx.doi.org/10.1023/A:1021200525430; Fang et al., 2006Fang, J., Wang, Z., Zhao, S. et al. 2006. Biodiversity changes in the lakes of the Central Yangtze. Frontiers in Ecology and the Environment 4: 369–377. http://dx.doi.org/10.1890/1540-9295(2006)004[0369:BCITLO]2.0.CO;2 ; López-Pujol & Ren, 2009López-Pujol, J. & Ren, M.-X. 2009. Biodiversity and the Three Gorges Reservoir: a troubled marriage. Journal of Natural History 43: 2765–2786. http://dx.doi.org/10.1080/00222930903220010). The huge human-driven transformation of this region (including intensive land reclamation and the construction of numerous dams and dikes) has altered most of the water network connections and, at present, the Poyang and Dongting lakes are the only sizable lakes that remain linked to the Yangtze River (Fang et al., 2006Fang, J., Wang, Z., Zhao, S. et al. 2006. Biodiversity changes in the lakes of the Central Yangtze. Frontiers in Ecology and the Environment 4: 369–377. http://dx.doi.org/10.1890/1540-9295(2006)004[0369:BCITLO]2.0.CO;2 ; Li, 2009Li, J. 2009. Scientists line up against dam that would alter protected wetlands. Science 236: 508–509. http://dx.doi.org/10.1126/science.326_508; Finlayson et al., 2010Finlayson, M., Harris, J., McCartney, M., Young, L. & Zhang, C. 2010. Report on Ramsar visit to Poyang Lake Ramsar site, P.R. China, 12–17 April 2010. Ramsar Convention on Wetlands. Retrieved December 18, 2011, from http://www.ramsar.org/pdf/Poyang_lake_report_v8.pdf ). The considerable biodiversity in these big lakes is also under threat by dam construction (e.g. López-Pujol & Ren, 2009López-Pujol, J. & Ren, M.-X. 2009. Biodiversity and the Three Gorges Reservoir: a troubled marriage. Journal of Natural History 43: 2765–2786. http://dx.doi.org/10.1080/00222930903220010). Such is the case for Poyang Lake, the biggest freshwater lake in China.

Poyang Lake is located at the south bank of the middle reaches of the Yangtze River, the largest river in China. This lake constitutes one of the six largest wetlands in China, with a maximum area of up to 4125 km² and a highest water depth of 20 m (Li, 2009Li, J. 2009. Scientists line up against dam that would alter protected wetlands. Science 236: 508–509. http://dx.doi.org/10.1126/science.326_508; Finlayson et al., 2010Finlayson, M., Harris, J., McCartney, M., Young, L. & Zhang, C. 2010. Report on Ramsar visit to Poyang Lake Ramsar site, P.R. China, 12–17 April 2010. Ramsar Convention on Wetlands. Retrieved December 18, 2011, from http://www.ramsar.org/pdf/Poyang_lake_report_v8.pdf ). The ecological importance of the lake and the associated wetland has been recognized at both national and international levels; in 1983 the Poyang Lake National Nature Reserve was established, and in 1992 it was listed as a Ramsar site (www.ramsar.org/). However, the local government has proposed to build a big dam at the northern end of Poyang Lake, 27 km from the Yangtze River (Li, 2009Li, J. 2009. Scientists line up against dam that would alter protected wetlands. Science 236: 508–509. http://dx.doi.org/10.1126/science.326_508). The main purpose of this planned dam is to stabilize the lake’s water level. During the last decade (and especially during 2011; Xinhua, 2011Xinhua 2011. China’s largest freshwater lake dwindles in severe drought. Xinhua Agency News, September 6, 2011. Retrieved December 20, 2011, from http://news.xinhuanet.com/english2010/china/2011-09/06/c_131106344.htm; China Daily, 2012China Daily 2012. Drought drying out Poyang Lake. China Daily, January 5, 2012. Retrieved April 15, 2012, from http://www.chinadaily.com.cn/china/2012-01/05/content_14382441.htm; Feng et al., 2012Feng, L., Hu, C., Chen, X., Cai, X., Tian, L. & Gan, W. 2012. Assessment of inundation changes of Poyang Lake using MODIS observations between 2000 and 2010. Remote Sensing of Environment 121: 80–92. http://dx.doi.org/10.1016/j.rse.2012.01.014), large sections of the lake have dried up; in January 2012, the inundation area dropped below 200 km² (China Daily, 2012China Daily 2012. Drought drying out Poyang Lake. China Daily, January 5, 2012. Retrieved April 15, 2012, from http://www.chinadaily.com.cn/china/2012-01/05/content_14382441.htm), which is less than 5% of its maximum extension. This drought produced losses in fisheries and other industries (Li, 2009Li, J. 2009. Scientists line up against dam that would alter protected wetlands. Science 236: 508–509. http://dx.doi.org/10.1126/science.326_508; People’s Daily 2011People’s Daily 2011. Drought turns China’s largest freshwater lake into ‘prairie’ People’s Daily Online, May 27, 2011. Retrieved December 20, 2011, from http://english.peopledaily.com.cn/90001/90783/7393094.html; China Daily, 2012China Daily 2012. Drought drying out Poyang Lake. China Daily, January 5, 2012. Retrieved April 15, 2012, from http://www.chinadaily.com.cn/china/2012-01/05/content_14382441.htm). However, disrupting the seasonal water flow by damming would also likely have severe negative impacts on the local climate and biodiversity (Li, 2009Li, J. 2009. Scientists line up against dam that would alter protected wetlands. Science 236: 508–509. http://dx.doi.org/10.1126/science.326_508; Harris & Hao, 2010Harris, J. & Hao, Z. 2010. An ecosystem approach to resolving conflicts among ecological and economic priorities for Poyang Lake wetlands. Wetlands International – IUCN SSC Crane Specialist Group. Retrieved December 22, 2011, from http://cmsdata.iucn.org/downloads/iucn_poyang_report_august_2010_final.pdf ), and thus the central government has suspended the project pending further studies.

The aim of this study is two-fold: (1) to survey the floristic richness of the whole region of Poyang Lake, by cataloguing both plant species and the dominant community types; and (2) to provide recommendations for the protection of plant diversity prior to the building of the dam based on our data gathering and analysis.

MATERIALS AND METHODSTop

Study area

Poyang Lake, while considered a shallow lake, does have flowing water and is the catchment for most of the surface water pooling in Jiangxi Province (CPLRE, 1988CPLRE (Council of Poyang Lake Research Editors) 1988. 鄱阳湖研究 [Research on Poyang Lake]. Shanghai Science & Technology Press, Shanghai [in Chinese].). The lake also functions in sediment transport (from the rivers flowing into the lake to the Yangtze River), and serves as a water accumulation center. The lake is located in a very flat area (the Middle-Lower Yangtze Plain) characterized by a mild subtropical monsoon climate. The water level of Poyang Lake is mainly influenced by the local watershed as well as by the Yangtze River’s water level. Inter-year and annual water level variation changes dramatically, with the inter-annual maximum amplitude reaching 16.69 m, which is mainly driven by the local precipitation regime and water level of Yangtze main channel (Feng et al., 2012Feng, L., Hu, C., Chen, X., Cai, X., Tian, L. & Gan, W. 2012. Assessment of inundation changes of Poyang Lake using MODIS observations between 2000 and 2010. Remote Sensing of Environment 121: 80–92. http://dx.doi.org/10.1016/j.rse.2012.01.014). Its flood season is from April to September, and its dry season is from October to the following March. The lake area differs substantially between flood season and dry season: its maximum area is up to 22 times that of the minimum area (Liu et al., 2006Liu X.-Z., Fan S.-B. & Hu B.-H. 2006. 江西湿地自然保护区综合科学考察 [Comprehensive scientific investigation in Jiangxi Wetland Nature Reserve]. China Forestry Publishing House, Beijing [in Chinese].). On average, the lake has a surface of over 3000 km² in the rainy season and less than 1000 km² in the dry season (Feng et al., 2011Feng, L., Hu, C., Chen, X., Li, R., Tian, L. & Murch B. 2011. MODIS observations of the bottom topography and its inter-annual variability of Poyang Lake. Remote Sensing of Environment 115: 2729–2741. http://dx.doi.org/10.1016/j.rse.2011.06.013).

Sampling site selection

Based on Poyang Lake’s geographical features, we selected nine areas (Table 1) within its wetland to conduct surveys of both plant species and community types. We used the broad definition provided by the Ramsar Convention to define the wetland; namely, wetlands are not only the areas permanently or temporarily covered by water (wetlands in the strict sense), but also the coastal or riparian zones adjacent to wetlands (RCS, 2013RCS (Ramsar Convention Secretariat) 2013. The Ramsar Convention Manual: a guide to the Convention on Wetlands (Ramsar, Iran, 1971) (6th ed.). Ramsar Convention Secretariat, Gland.). The nine selected areas were the following: (1) Ganjiang River bank near Nanchang Bridge, (2) Taizi River of Hongwei Village in Nanji Mountain, (3) west branch of Ganjiang River in Wucheng Town of Yongxiu County, (4) Old petrochemical wharf in Xingzi County, (5) Shizhong Mountain in Hukou County, (6) Changjiang in Poyang County, (7) East River of Xinjiang River, (8) Sub-river of Chenjia Lake, and (9) Sanyang Bridge of Fuhe River (Fig. 1 and Table 1). In the above nine areas, we selected a number of sampling sites according to the shape and size of the local water bodies. Sites were randomly located along a transect from the central core of the wetland to its edge. Additional sampling sites were selected both in areas with very large wetlands and in cases where we detected that the distribution of plant species was uneven (Table 1). We set at least three plots (of 1 × 1 m) at each of the sampling sites. In total, 317 sampling plots were established, which were representative of three main habitats or ecological zones of the Poyang Lake wetland system: permanent aquatic areas, seasonally aquatic areas (that is, those covered during the flood season, e.g. lakeshore areas), and areas adjacent to wetlands (i.e. those areas only flooded occasionally) (Table 1).

Figure 1. Location of the nine study areas within the Poyang Lake wetland. The location of Poyang Lake within the Yangtze River Basin and the location of Yangtze River Basin within China are also shown (smaller maps below the larger map). [View full size] [Descargar tamaño completo]

Plant species and plant community measures

For each plot, we catalogued all the plant taxa occurring there; plants were identified following Moss Flora of China (MFCEC, 1999–2011MFCEC (Moss Flora of China Editorial Committee) 1999–2011. Moss Flora of China 1–8. Science Press, Beijing and New York, and Missouri Botanical Garden, St. Louis. ), Flora of China (http://flora.huh.harvard.edu/china/), and Flora of Jiangxi (ECFJ, 1993ECFJ (Editorial Committee for Flora of Jiangxi) 1993. 江西植物 [Flora of Jiangxi] 1. Jiangxi Science and Technology Publishing House, Nanchang [in Chinese]. Retrieved April–June, 2012, from http://v2.cvh.org.cn/difangzhi/jiangxi/List.asp?pgno=1). We also recorded the dominant plant community types for each plot, which were identified following the criteria of Vegetation of China (Wu, 1980Wu, Z.-Y. (Ed.) 1980. 中国植被 [Vegetation of China]. Science Press, Beijing [in Chinese].). For each plant taxon, a series of characteristics useful for recognizing the plant community types and defining their features (community structure, composition) were determined, including: habit (annual, biennial, or perennial), life-form (herb, shrub, tree, or vine), origin (see below), hydro-ecotype (see below), coverage, height, phenology, and abundance. Some of these traits were determined with the aid of the Higher aquatic plants in Jiangxi Province (Guan & Zhang, 1989Guan, S.-F. & Zhang T.-H. 1989. 江西高等水生植物 [Higher aquatic plants in Jiangxi]. Shanghai Science and Technology Press, Shanghai [in Chinese].) and other relevant sources (e.g. Flora of China; http://flora.huh.harvard.edu/china/). For the origin, we assigned each taxon to one of the following categories: endemic to China, native to China, and alien; the alien taxa, in turn were classified in three groups: naturalized, invasive, and cultivated. The hydro-ecotypes of the identified plant species were determined depending on their water requirements: plant species that grow in moist environments and that cannot endure long term water deficiency were regarded as hygrophytes, those that grow in moderately moist habitats as mesophytes, those that grow in arid environments and show drought tolerance as xerophytes, and those truly aquatic as hydrophytes (Li et al., 2004Li, B., Yang, C. & Lin, P. 2004. 生态学 [Ecology]. Higher Education Press, Beijing [in Chinese].).

All the fieldwork was conducted in October 2011. In addition, several relevant works (i.e. Guan & Zhang, 1989Guan, S.-F. & Zhang T.-H. 1989. 江西高等水生植物 [Higher aquatic plants in Jiangxi]. Shanghai Science and Technology Press, Shanghai [in Chinese].; Ge & Wu, 2006Ge, G. & Wu, L. 2006. 南矶山自然保护区种子植物区系 [Analysis on the flora of seed plants in Nanjishan Nature Reserve, Jiangxi]. Journal of Nanchang University (Natural Science) 30: 52–55 [in Chinese].; JPLNNRA, 2008JPLNNRA (Jiangxi Poyang Lake National Nature Reserve Authority) 2008. 植物种类数据库 [Plant species database]. Retrieved October 12–30, 2011, from http://www.poyanglake.org/ArticleDetail.aspx?id=151; Ge et al., 2010Ge, G., Li, E.-X., Wu, H.-P. & Wu Z.-Q. 2010. 鄱阳湖国家级自然保护区的外来入侵植物调查 [Invasive plants in the national nature reserve of Lake Poyang]. Journal of Lake Sciences 22: 93–97 [in Chinese].; Hu et al., 2010Hu, Z.-P., Ge, G., Liu, C.-L., Chen, F.-S. & Li S. 2010. 鄱阳湖湿地植物生态系统结构及湖水位对其影响研究 [Structure of Poyang Lake wetland plants ecosystem and influence of lake water level for the structure]. Resources and Environment in the Yangtze Basin 19: 597–605 [in Chinese].; Wu et al., 2010aWu, J.-D., Liu, G.-H., Jin, J.-F. et al. 2010a. 鄱阳湖秋季沙洲植被结构分析 [Structure analysis of beach vegetation in Poyang Lake in autumn]. Jiangxi Science 28: 549–554 [in Chinese].; Li et al., 2011Li, S.-D., Lu, B., Liu, H., Liu, W.-Z. & Duan, X.-H. 2011. 鄱阳湖湿地土壤种子库特征及其与地表植被的关系 [Soil seed bank and its relation to vegetation in the littoral zone of Poyang Lake]. Journal of Jiangxi Normal University (Natural Science Edition) 35: 431–436 [in Chinese].) were also consulted to complete the list of plant species and communities occurring within the Poyang Lake wetland. Infraspecific taxa (i.e. subspecies, varieties, and forms) were treated as equivalent to species to simplify the analyses.

RESULTSTop

Species richness

Poyang Lake harbored a high diversity of plants: up to 124 families, 339 genera, and 512 species (including sub-species, varieties and forms) were found in the study area (see Appendix). The number of species belonging to bryophyta, pteridophyta, gymnospermae, and angiospermae was two, 16, 13, and 481, respectively, which accounted for 0.4%, 3.1%, 2.5%, and 93.9% of all species, respectively. Of the angiosperms, eight were basal angiosperms, 123 were monocots, and 350 were eudicots. The plant families with the greatest number of species were Asteraceae (38 species), Poaceae (35), Cyperaceae (25), and Fabaceae (24). These, together with other six families (Fig. 2), contained a total of 208 species, which accounted for 40.6% of all plant species. Polygonum L., Carex L., and Potamogeton L. were the genera with the largest number of representatives in the wetland, with 10, nine, and seven species, respectively.

Figure 2. Taxonomic structure of Poyang Lake flora. Only the 10 largest families in number of plant taxa in Poyang Lake are shown. [View full size] [Descargar tamaño completo]

The habits and life-forms of all plant species in the Poyang Lake wetland were also diverse. Most of the species recorded in the wetland were herbs (371 out of 512 species), although these greatly differed regarding the habit (Fig. 3). Shrubs represented about 11.3% of the total number of species (58 species), trees about 13.3% (68 species), and vines ca. 2.9% (15 species) (Fig. 3). Regarding the hydro-ecotype, the bulk of the plants in the wetland were mesophytes, which accounted for up to 62.7% of the total number of species (321 species); moreover, plants that were either classifed as mesophytes or hygrophytes represented 13.7%, those that were either mesophytes or xerophytes represented 9.8%, and those that were either mesophytes, xerophytes, or hygrophytes accounted for 0.4%. Species with strict water requirements constituted a relatively low percentage of the Poyang wetland plants: hydrophytes acounted for 7.0%, hygrophytes for 3.7%, and those species that were either classified as hydrophytes or hygrophytes, for 2.7%.

Figure 3. Habit and life-form of Poyang Lake flora. [View full size] [Descargar tamaño completo]

As for the origin, most of the plant taxa that occur in the Poyang Lake wetland were native to China (402 taxa, 78.5%), whereas only 31 (6.1%) were endemic to China. Among the endemics, there were several rare, threatened, and/or nationally protected species; some outstanding examples include (1) the fern Isoëtes sinensis Palmer (which is ‘critically endangered’ according to IUCN criteria, and included both in the National List of Rare and Endangered Plant Species of 1984 and in the Catalogue of the National Protected Key Wild Plants of 1999), as well as (2) the gymosperms Ginkgo biloba L. and Metasequoia glyptostroboides Hu & W. C. Cheng (which are ‘endangered’ and included in both protection lists). A total of 79 species of the 512 recorded within the wetland (that is, 15.4%) were of alien origin; of these, 25 were cultivated, 31 were invasive, 11 were naturalized, and 12 were of uncertain nature, which accounted for 4.9%, 6.1%, 2.1%, and 2.3% of all species, respectively. Although not very large, we found some differences regarding the origin of plant taxa between ecological zones (Fig. 4): the percentage of native taxa decreases from permanent aquatic areas to areas adjacent to wetlands, whereas the reverse trend was observed for the alien plants.

Figure 4. Histogram showing the percentage of plant taxa native to China (N), endemic to China (E), alien cultivated (AC), alien invasive (AI), alien naturalized (AN), alien cultivated or invasive (AC/AI), and alien cultivated or naturalized (AC/AN) for the three ecological areas in the Poyang Lake wetland system (permanent aquatic areas, seasonally aquatic areas, and areas adjacent to wetlands). [View full size] [Descargar tamaño completo]

Plant communities

Based on the species composition in the Poyang Lake wetlands, eight dominant plant communities can be distinguished:

(1) Phalaris arundinacea L. – Polygonum criopolitanum Hance – Cardamine lyrata Bunge communities. These communities, typically of seasonally aquatic areas (Table 2), were mainly distributed in the northern low marshland and southern delta islands, with a height of 60–80 cm and total vegetative coverage per unit area of up to 60 to 80% (Figs. 5 and 6). The companion species were Carex argyi H. Lév. & Vaniot and Cardamine lyrata.

Table 2. Occurrence of the eight dominant plant communities on the three main habitats or ecological zones of the Poyang Lake wetland system (permanent aquatic areas, seasonally aquatic areas, and areas adjacent to wetlands). ++, high occurrence; +, intermediate occurrence; –, low or no occurrence.

Communities Permanent aquatic areas Seasonally aquatic areas Areas adjacent to wetlands Phalaris arundinacea – Polygonum criopolitanum – Cardamine lyrata communities – ++ + Nymphoides peltata – Potamogeton wrightii – Hydrilla verticillata + Vallisneria natans communities ++ – – Carex spp. communities – ++ + Polygonum criopolitanum communities – ++ + Phragmites australis – Miscanthus lutarioriparius communities + ++ + Cynodon dactylon communities + ++ + Eleocharis valleculosa communities + ++ + Vallisneria spp. communities ++ + –

Figure 5.Some plant species in the Poyang Lake wetland, Jiangxi Province. (A), Nymphoides peltata; (B), Eichhornia crassipes; (C), Lagopsis supina (Steph. ex Willd.) Ikonn.-Gal. ex Knorring; (D), Rumex acetosa L.; (E), Polygonum criopolitanum; (F), Xanthium strumarium L. [View full size] [Descargar tamaño completo]

Figure 6. Representative plant communities in the Poyang Lake wetland. (A), Miscanthus lutarioriparius + Carex cinerascens Kük. community; (B), Polygonum criopolitanum community; (C), Phalaris arundinacea + Carex cinerascens community; (D), Oryza sativa L. + Cynodon dactylon community. [View full size] [Descargar tamaño completo]

(2) Nymphoides peltata (S. G. Gmel.) Kuntze – Potamogeton wrightii Morong – Hydrilla verticillata (L. f.) Royle + Vallisneria natans (Lour.) H. Hara communities. These were primarily distributed on the edges and marshland of rivers, exclusively on permanent aquatic areas (Table 2). Nymphoides peltata (Fig. 5), a floating-leaved plant, was the dominant species occupying the upper layer. Potamogeton wrightii, Hydrilla verticillata, and Vallisneria natans were common species showing underwater stratification.

(3) Carex spp. communities. These comprised widely distributed communities that occupy the largest area in the Poyang Lake wetlands (Fig. 6), mainly on seasonally aquatic areas (Table 2). The height of the community was between 40–60 cm with a vegetative cover of 100%. The structure was simple, usually composed of six to eight species per square meter, with the following common companion species: Cardamine lyrata, Polygonum hydropiper L., Polygonum japonicum Meisn., Panicum bisulcatum Thunb., and Viola philippica Cav.

(4) Polygonum criopolitanum communities. These were mainly distributed in the marshes of river banks with a total vegetative coverage of about 40%, a height of 5–10 cm and a single-layer structure (Fig. 6). The companion species of these communities, mainly occurring on seasonally aquatic areas (Table 2), were Lapsanastrum apogonoides (Maxim.) Pak & K. Bremer, Rorippa indica (L.) Hiern, and Alopecurus aequalis Sobol.

(5) Phragmites australis (Cav.) Trin. ex Steud. – Miscanthus lutarioriparius L. Liu ex Renvoize & S. L. Chen communities. These were mainly distributed on seasonally aquatic areas (particularly in the levee embankment; Table 2), and were mainly located in the southwest corner of Mopanzhou and Dashahuang islands (Fig. 6). The dominant species were Phragmites australis and Miscanthus lutarioriparius, the community structure was complex, and the companion species included Artemisia selengensis Turcz. ex Besser, among others.

(6) Cynodon dactylon (L.) Pers. communities. These were single-layer structure communities typically occurring on seasonally aquatic areas (Table 2), with a height of 20–30 cm, distributed near the levee and the high beaches (Fig. 6). The total vegetative cover per unit area of these communities was typically 80–90%, dominated by C. dactylon. Companion species included Eremochloa ophiuroides (Munro) Hack., Hemarthria altissima (Poir.) Stapf & C. E. Hubb., Hemisteptia lyrata (Bunge) Fisch. & C. A. Mey., Aster indicus L., Hydrocotyle sibthorpioides Lam., and Mollugo stricta L.

(7) Eleocharis valleculosa Ohwi communities. These were the most common communities in the Poyang Lake marsh, mainly found on seasonally aquatic areas (Table 2). The species composition was complex, having a height of 20–30 cm and total vegetative cover per unit area of 70–80%. The vertical structure, in contrast, was simple, with only one layer.

(8) Vallisneria spp. L. communities. These comprised the most widespread submerged plant communities in Poyang Lake (Table 2). Mainly distributed in the southern section of the lake, the community structure was simple, consisting of a single layer, and the companion species were Utricularia aurea Lour., Potamogeton crispus L., and Potamogeton distinctus A. Benn.

DISCUSSIONTop

Floristic and vegetation features of Poyang Lake

The vegetation resources in Jiangxi Province are abundant, possessing a high taxonomic richness along with numerous and complex vegetation types that are closely related to the floristic origin and evolution of this region (ECFJ, 1993ECFJ (Editorial Committee for Flora of Jiangxi) 1993. 江西植物 [Flora of Jiangxi] 1. Jiangxi Science and Technology Publishing House, Nanchang [in Chinese]. Retrieved April–June, 2012, from http://v2.cvh.org.cn/difangzhi/jiangxi/List.asp?pgno=1; Wang, 2004Wang, X.-H. 2004. 鄱阳湖湿地生态系统评价 [Poyang Lake Wetland ecosystem assessment]. Science Press, Beijing [in Chinese].; Peng, 2007Peng, K.-S. 2007. 江西生态学 [Jiangxi ecology]. Jiangxi People’s Publishing House, Nanchang [in Chinese]. ; Hu et al., 2010Hu, Z.-P., Ge, G., Liu, C.-L., Chen, F.-S. & Li S. 2010. 鄱阳湖湿地植物生态系统结构及湖水位对其影响研究 [Structure of Poyang Lake wetland plants ecosystem and influence of lake water level for the structure]. Resources and Environment in the Yangtze Basin 19: 597–605 [in Chinese].). The regional vegetation of Jiangxi Province belongs to subtropical evergreen broad-leaved forest, with some warm temperate plant elements (deciduous broad-leaved forest) that are mixed gradually in the northern part of the Poyang Lake wetland (i.e. in the northern part of Jiangxi Province) (Wu, 1980Wu, Z.-Y. (Ed.) 1980. 中国植被 [Vegetation of China]. Science Press, Beijing [in Chinese].; Hou, 1983Hou, X-Y. 1983. Vegetation of China with reference to its geographical distribution. Annals of the Missouri Botanical Garden 70: 509–548. http://dx.doi.org/10.2307/2992085). The vegetation of the province can be regarded as unique in the sense that there are many subtropical endemic genera, relic plant species, and ancient tropical flora elements (ECFJ, 1993ECFJ (Editorial Committee for Flora of Jiangxi) 1993. 江西植物 [Flora of Jiangxi] 1. Jiangxi Science and Technology Publishing House, Nanchang [in Chinese]. Retrieved April–June, 2012, from http://v2.cvh.org.cn/difangzhi/jiangxi/List.asp?pgno=1); in fact, the province harbour some of the main centres of plant endemism in China (López-Pujol et al., 2011López-Pujol, J., Zhang, F.-M., Sun, H.-Q., Ying, T.-S. & Ge, S. 2011. Centres of plant endemism in China: places for survival or for speciation? Journal of Biogeography 38: 1267–1280. http://dx.doi.org/10.1111/j.1365-2699.2011.02504.x; Huang et al., 2012Huang, J., Chen, B., Liu, C., Lai, J., Zhang, J. & Ma, K. 2012. Identifying hotspots of endemic woody seed plant diversity in China. Diversity and Distributions 18: 673–688. http://dx.doi.org/10.1111/j.1472-4642.2011.00845.x). Our study confirms that these features (high species richness, endemism and presence of relict elements) also characterize the flora of Poyang Lake.

The Poyang Lake wetland is very rich in terms of total plant species, and harbours a significant part of the total flora of the province. Of the 49 families, 114 genera, and 400 species of ferns recorded in Jiangxi Province (ECFJ, 1993ECFJ (Editorial Committee for Flora of Jiangxi) 1993. 江西植物 [Flora of Jiangxi] 1. Jiangxi Science and Technology Publishing House, Nanchang [in Chinese]. Retrieved April–June, 2012, from http://v2.cvh.org.cn/difangzhi/jiangxi/List.asp?pgno=1), 12 families, 13 genera and 16 species have been identified in the present study (which accounts for 22.5%, 11.4%, and 4%, respectively). Regarding gymnosperms, the provincial flora contains eight families, 23 genera and 30 gymnosperm species (ECFJ, 1993ECFJ (Editorial Committee for Flora of Jiangxi) 1993. 江西植物 [Flora of Jiangxi] 1. Jiangxi Science and Technology Publishing House, Nanchang [in Chinese]. Retrieved April–June, 2012, from http://v2.cvh.org.cn/difangzhi/jiangxi/List.asp?pgno=1); in the Poyang Lake wetland, five families, 10 genera and 13 species are found, accounting for 62.5%, 43.5%, and 43.3%, respectively. The wetland flora is also rich in angiosperms: of the 220 families, 1309 genera, and 2373 species included in Flora of Jiangxi (Guan & Zhang, 1989Guan, S.-F. & Zhang T.-H. 1989. 江西高等水生植物 [Higher aquatic plants in Jiangxi]. Shanghai Science and Technology Press, Shanghai [in Chinese].; ECFJ, 1993ECFJ (Editorial Committee for Flora of Jiangxi) 1993. 江西植物 [Flora of Jiangxi] 1. Jiangxi Science and Technology Publishing House, Nanchang [in Chinese]. Retrieved April–June, 2012, from http://v2.cvh.org.cn/difangzhi/jiangxi/List.asp?pgno=1), we have found 106 families, 314 genera, and 481 species, which accounts for 48.2%, 24.0%, and 20.3%, respectively. The large number of plant taxa identified in the present study (512) is in agreement with recent studies (Ge & Wu, 2006Ge, G. & Wu, L. 2006. 南矶山自然保护区种子植物区系 [Analysis on the flora of seed plants in Nanjishan Nature Reserve, Jiangxi]. Journal of Nanchang University (Natural Science) 30: 52–55 [in Chinese].; JPLNNRA, 2008JPLNNRA (Jiangxi Poyang Lake National Nature Reserve Authority) 2008. 植物种类数据库 [Plant species database]. Retrieved October 12–30, 2011, from http://www.poyanglake.org/ArticleDetail.aspx?id=151; Jiang et al., 2009Jiang, X.-M., Zhou, M.-R., Li, T., Sun, Z.-Y., Xiao, F.-M. & Lou, Z.-J. 2009. 鄱阳湖退化湿地生态系统恢复策略初探 [Recovery strategies of degradation wetland ecosystem in Poyang Lake]. Jiangxi Forestry Science and Technology 6: 50–53 [in Chinese].; see Table 3), although our work is the first covering all the wetlands range and all the major plant communities in Poyang Lake.

As mentioned, many endemic (up to 38 species, 7.4% of the total) and relict floristic elements are present in Poyang Lake. For example, we found Cryptomeria japonica (Thunb. ex L. f.) D. Don var. sinensis Miq., a conifer lineage that might date from the Cretaceous according to molecular data (Ran et al., 2010Ran, J.-H., Gao, H. & Wang, X.-Q. 2010. Fast evolution of the retroprocessed mitochondrial rps3 gene in Conifer II and further evidence for the phylogeny of gymnosperms. Molecular Phylogenetics and Evolution 54: 136–149. http://dx.doi.org/10.1016/j.ympev.2009.09.011). At present, only a single species with two varieties exists in the world; one is native to Japan [i.e. Cryptomeria japonica (Thunb. ex L. f.) D. Don var. japonica], and the other one (Cryptomeria japonica var. sinensis) is widespread in China, including Jiangxi Province. Another relict species that occurs within the Poyang Lake wetland is Cunninghamia lanceolata (Lamb.) Hook., a companion species in the evergreen broad-leaved forest now widely cultivated as a plantation tree. It has become one of the most important and valuable fast-growing species in subtropical China. Metasequoia glyptostroboides and Ginkgo biloba are also relict species that have lineages likely dating from the Cretaceous (Ran et al., 2010Ran, J.-H., Gao, H. & Wang, X.-Q. 2010. Fast evolution of the retroprocessed mitochondrial rps3 gene in Conifer II and further evidence for the phylogeny of gymnosperms. Molecular Phylogenetics and Evolution 54: 136–149. http://dx.doi.org/10.1016/j.ympev.2009.09.011). These rare and nationally protected species (Fu & Jin, 1992Fu L.-G. & Jin J.-M. (Eds.) 1992. China plant Red Data Book. Rare and endangered plants 1. Science Press, Beijing. ; YNCC, 2011YNCC (Yunnan Nature Conservancy of China) 2011. 云南自然保护数据库 [Database of Yunnan Nature Conservation]. Retrieved December 1, 2011, from http://www.ynnc.org:7001/WZML/WzmlxxListCs.do?wzlbdm=01) are widely found within the Poyang Lake wetland.

When Poyang Lake is at its normal water level (14 to 15 meters), the inundated area is over 3000 km² (Feng et al., 2011Feng, L., Hu, C., Chen, X., Li, R., Tian, L. & Murch B. 2011. MODIS observations of the bottom topography and its inter-annual variability of Poyang Lake. Remote Sensing of Environment 115: 2729–2741. http://dx.doi.org/10.1016/j.rse.2011.06.013), which represents about 2% of the total land mass of Jiangxi Province. Because of the high plant diversity in this small area, it is of vital importance to ensure an adequate protection of Poyang Lake. Indeed, the wetland represents a regional hotspot of biodiversity and its species richness is higher than that of other wetlands within the Yangtze Basin. Poyang wetland alone harbours a very important part of China’s wetland flora: 65% of the gymnosperms (13 out of 20; An et al., 2007An, S., Li, H., Guan, B. et al. 2007. China’s natural wetlands: Past problems, current status, and future challenges. Ambio 36: 335–342. http://dx.doi.org/10.1579/0044-7447(2007)36[335:CNWPPC]2.0.CO;2), and 40% of the angiosperms (481 out of 1200; An et al., 2007An, S., Li, H., Guan, B. et al. 2007. China’s natural wetlands: Past problems, current status, and future challenges. Ambio 36: 335–342. http://dx.doi.org/10.1579/0044-7447(2007)36[335:CNWPPC]2.0.CO;2). For example, Dongting Lake, the second largest freshwater lake in China (and with a similar area to Poyang; Table 3), has considerably less plant diversity, with only about 192 plant species reported (ECWVC, 1999ECWVC (Editorial Committee of Wetland Vegetation in China) 1999. 中国湿地植被 [Wetland vegetation in China]. Science Press, Beijing [in Chinese]. ). Another sizable lake (Taihu Lake, which is located in the Yangtze Delta plain) also has a much lower plant species richness (74 species; Zhang et al., 1999Zhang, S.-Z., Wang, G.-X., Pu, P.-M. & Chigira, T. 1999. 太湖东区沼泽水生植被演替 [Succession of hydrophytic vegetation and swampy tendency in the East Taihu Lake]. Journal of Plant Resources and Environment 8: 1–6 [in Chinese]. ), although for the Taihu Lake study only the permanent and seasonally aquatic areas were studied (Table 3).

In addition to biogeographical and ecological reasons, the wealth of species in Poyang wetland may be partly due to its relatively good conservation status (Li, 2009Li, J. 2009. Scientists line up against dam that would alter protected wetlands. Science 236: 508–509. http://dx.doi.org/10.1126/science.326_508). Mirroring this, most of the species present in the wetland are native (around 80%), a percentage that increases from areas adjacent to wetlands (the most disturbed due to their strong cultivation, especially rice) to permanent aquatic areas (the less disturbed ones; Fig. 4). On the contrary, the reverse trend occurs for the alien plants, which peak in the areas adjacent to wetlands. Human disturbances, such as fires, urbanization, or agricultural practices, may encourange invasions because new ecological niches are available for alien species (Mack et al. 2000Mack, R. N., Simberloff, D., Lonsdale, W. M., Evans, H., Clout, M. & Bazzaz, F. A. 2000. Biotic invasions: causes, epidemiology, global consequences, and control. Ecological Applications 10: 689–710. http://dx.doi.org/10.1890/1051-0761(2000)010[0689:BICEGC]2.0.CO;2, Simberloff & Rejmánek, 2011Simberloff, D. & Rejmánek, M. (Eds.) 2011. Encyclopedia of biological invasions. University of California Press, Berkeley, Los Angeles & London.).

Up to 15 regional and non-regional vegetation types defined in the provincial flora (ECFJ, 1993ECFJ (Editorial Committee for Flora of Jiangxi) 1993. 江西植物 [Flora of Jiangxi] 1. Jiangxi Science and Technology Publishing House, Nanchang [in Chinese]. Retrieved April–June, 2012, from http://v2.cvh.org.cn/difangzhi/jiangxi/List.asp?pgno=1) have been recorded in Jiangxi, of which four (meadows, aquatic plant communities, herb marshes and peat swamps) are present in the Poyang Lake wetland. In fact, Poyang Lake harbors a representative sample of the vegetation types reported for China as a whole (two of the 11 vegetation type groups, and 55 of the 960 formations and sub-formations; Zhang, 2007Zhang, X. (Ed.) 2007. 中华人民共和国植被图 [The vegetation map of the People’s Republic of China (1:1,000,000)]. The Geological Publishing House, Beijing [in Chinese]. ; Hu et al., 2010Hu, Z.-P., Ge, G., Liu, C.-L., Chen, F.-S. & Li S. 2010. 鄱阳湖湿地植物生态系统结构及湖水位对其影响研究 [Structure of Poyang Lake wetland plants ecosystem and influence of lake water level for the structure]. Resources and Environment in the Yangtze Basin 19: 597–605 [in Chinese].; Zhang et al., 2012Zhang, L., Yin, J., Jiang, Y. & Wang, H. 2012. Relationship between the hydrological conditions and the distribution of vegetation communities within the Poyang Lake National Nature Reserve, China. Ecological Informatics 11: 65–75. http://dx.doi.org/10.1016/j.ecoinf.2012.05.006). In our study, up to eight dominant plant community types have been identified in the Poyang Lake wetland, and these eight communities belong to the above four vegetation types. Cynodon dactylon communities, Carex spp. communities, and Polygonum criopolitanum communities belong to the meadow vegetation type; Phragmites australis – Miscanthus lutarioriparius communities belong to the herb marsh vegetation type; Nymphoides peltata – Potamogeton wrightii – Hydrilla verticillata + Vallisneria natans communities, Eleocharis valleculosa communities, and Vallisneria spp. communities belong to the aquatic plant vegetation type; and Phalaris arundinacea – Polygonum criopolitanum – Cardamine lyrata communities belong to the peat swamp vegetation type.

Conservation implications

If the reservoir is built with the purpose of stabilizing lake levels, the original habitats of many species will be permanently flooded: most of the mesophytes and hygrophytes that live in the currently seasonally flooded areas will lose their habitat. Flooding will have a severe impact on several rare and endangered plants, e.g. Cryptomeria japonica var. sinensis, Ginkgo biloba, and Metasequoia glyptostroboides. Hydrophytes will also be affected, as the water levels and flood regime of Poyang Lake will be deeply modified. Regarding the vegetation, Phragmites australis – Miscanthus lutarioriparius communities, and Cynodon dactylon communities would be among the most affected by the potential flooding because these occur on the shore. On the other hand, those communities that may survive at a very wide variety of hydrological conditions, such as Carex ssp. communities, would not be seriously affected; these Carex spp. communities, which are the dominant type in Poyang Lake wetland, can be found at depths ranging from 0 to nearly 15 m, with the percent time inundated between 0 and 100% (Zhang et al., 2012Zhang, L., Yin, J., Jiang, Y. & Wang, H. 2012. Relationship between the hydrological conditions and the distribution of vegetation communities within the Poyang Lake National Nature Reserve, China. Ecological Informatics 11: 65–75. http://dx.doi.org/10.1016/j.ecoinf.2012.05.006).

If the dam is constructed, water flow will be slower and the regime of water-level fluctuations will change in Poyang Lake and related rivers. These modifications can accelerate eutrophication and will likely facilitate clonal reproduction and spread of invasive plants (Mack et al., 2000Mack, R. N., Simberloff, D., Lonsdale, W. M., Evans, H., Clout, M. & Bazzaz, F. A. 2000. Biotic invasions: causes, epidemiology, global consequences, and control. Ecological Applications 10: 689–710. http://dx.doi.org/10.1890/1051-0761(2000)010[0689:BICEGC]2.0.CO;2), especially of the floating macrophytes such as the water hyacinth, Eichhornia crassipes (Mart.) Solms, and the water lettuce, Pistia stratiotes L., both of which were already found in Poyang Lake (see Appendix and Fig. 5). These two noxious plant invaders can seriously threaten the local plant diversity and ecosystem functioning (Barrett, 1989Barrett, S. C. H. 1989. Waterweed invasions. Scientific American 260: 90–97. http://dx.doi.org/10.1038/scientificamerican1089-90). Serious attention should be paid to these invasive plants and the other alien species that may likely cause similar environmental problems after the reservoir is built. Construction of the Three Gorges Dam, about 900 km usptream on the Yangtze River, have facilitated the establishment of highly invasive alien species in its reservoir region, including the above-mentioned Eichhornia crassipes, Alternanthera philoxeroides (Mart.) Griseb., or Erigeron sumatrensis Retz. (Ding et al., 2008Ding, J., Mack, R. N., Lu, P., Ren, M. & Huang, H. 2008. China’s booming economy is sparking and accelerating biological invasions. BioScience 58: 317–324. http://dx.doi.org/10.1641/B580407). In this sense, appropriate management strategies to minimize further invasions in Poyang wetland, including setting up early detection methods and enforcing quarantines and inspection procedures, should be urgently implemented. Clearly, more specific research is needed (e.g. vegetation succession and biophysical and ecological modelling; Kummu et al., 2006Kummu, M., Sarkkula, J., Koponen, J. & Nikula, J. 2006. Ecosystem management of the Tonle Sap Lake: an integrated modelling approach. International Journal of Water Resources Development 22: 497–519. http://dx.doi.org/10.1080/07900620500482915) to precisely identify and quantify the possible impacts on the biodiversity that damming will exert.

Disappearance or disturbance of forests, shrublands, grasslands, and aquatic communities due to permanent flooding will lead to great ecological losses. Therefore, in order to minimize these impacts, it is imperative to set up a series of in situ conservation measures that might include enhancing nature reserves, restoring degraded ecosystems, and optimizing artificial ecosystems. Setting up new nature reserves and expanding existing ones seems an urgent and necessary task given that new pressures on Poyang wetland are arising, such as the massive sand dredging currently being undertaken in an effort to cope with the demand for sand used in construction (Harris & Hao, 2010Harris, J. & Hao, Z. 2010. An ecosystem approach to resolving conflicts among ecological and economic priorities for Poyang Lake wetlands. Wetlands International – IUCN SSC Crane Specialist Group. Retrieved December 22, 2011, from http://cmsdata.iucn.org/downloads/iucn_poyang_report_august_2010_final.pdf ). Constructed and restored wetlands, e.g. paddy fields and fishing grounds, often lack, however, the ecological functions provided by natural habitats (Zedler, 1993Zedler, J. B. 1993. Canopy architecture of natural and planted cordgrass marshes: Selecting habitat evaluation criteria. Ecological Applications 3: 123–138. http://dx.doi.org/10.2307/1941796; Kentula, 1996Kentula, M. E. 1996. Wetland restoration and creation. In: Fretwell, J. D., Williams, J. S. & Redman P. J. (Eds.), The national water summary on wetland resources. Water-supply paper 2425. U.S. Geological Survey, Washington: 87–92.) and thus additional research should be conducted in this direction. The ex situ conservation of the rare and interesting species affected by damming could be accomplished by transplanting these species into botanical gardens and keeping their seeds in germplasm banks. These measures, in addition to contributing to the plant diversity protection, would also serve for economic development.

ACKNOWLEDGMENTSTop

The authors are grateful to Dr. Y.-Y. Xu (Anhui Normal University, China) for his constructive comments and suggestions to the manuscript, and to Dr. T. Friedman (Thompson Rivers University) for his review of the manuscript. The field work is financially supported by a special fund project for the scientific research from the Ministry of Water Resources of People’s Republic of China (201101041), a grant from Poyang Lake Water Project on Water Environment Regulation Research (201001054), and a grant from the National Natural Science Foundation of China (41201049). This work was also supported in part by a Discovery Grant from the Natural Sciences and Engineering Research Council (NSERC) of Canada (grant number 164375) to C. Ross Friedman, and by a post-doctoral “Beatriu de Pinós” fellowship (Generalitat de Catalunya) to J. López-Pujol.

APPENDIXTop

REFERENCESTop