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22 May 2018 A contribution to the knowledge of epiphyllous bryophytes in Tianmushan National Nature Reserve (Zhejiang, China), with remarks on climate warming and nature conservation
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Abstract
Five epiphyllous liverwort species, all members of the family Lejeuneaceae, are newly reported from Tianmushan National Nature Reserve, Zhejiang Province, China. The locality constitutes the northernmost occurrence of epiphyllous bryophytes in eastern China. It is proposed that the establishment of the epiphyllous species in the reserve was the result of a recent dispersal event influenced by climate warming. The site where the species occur is increasingly impacted by ecotourism and forest ecology teaching. Limitation of teaching at the site, reduction of the number of trails and stricter conservation is recommended in order to protect the fragile local epiphyllous community.

Epiphyllous bryophytes mainly occur on leaves of vascular plants, in the understory of moist tropical and subtropical forests (Richards 1984, Jiang et al. 2014), and more than 95% of the species are members of the liverwort family Lejeuneaceae (Pócs 1996, Gradstein 1997). They occur in 21 floristic regions of Asia, Australia, Africa, America and Europe, with Asia having the highest diversity with more than 500 known species of epiphylls (Pócs 1996). Outside the tropics and subtropics, epiphyllous bryophytes are rare (Duckett 2008). In China, the distributional ranges of epiphyllous liverworts are restricted to south of 31° N, including 11 provinces (Anhui, Fujian, Guangdong, Guizhou, Hainan, Hunan, Jiangxi, Sichuan, Taiwan, Yunnan and Zhejiang) as well as the regions of Guangxi, Xizang and Hong Kong, at elevations ranging from sea level to 3000 m (Zhu and So 2001, p. 27). Highest species numbers are found in cloud forests of Yunnan, Hainan and Taiwan between 700 – 1600 m (Zhu and So 2001).

Being negatively affected by direct sunlight and reduction of air humidity, epiphyllous bryophytes are very sensitive to climate change and forest modification, and hence are potential indicators of forest health (Alvarenga et al. 2009, Frego 2007, Pócs 1996, Zartman 2003). Negative impacts on the structure of the canopy or other layers of the forest may result in impoverishment or loss of the epiphyllous communities. The invasion of weedy angiosperm species unsuitable as hosts for epiphylls may also negatively influence the epiphyllous bryophyte flora (Pócs 1996).

Over the past 30 years, China has experienced rapid economic development, accompanied by increased emission of greenhouse gases, ozone precursors and aerosols, and made a contribution to global radiative forcing (Li et al. 2016). The rapid economic growth as well as the increased tourism activities had a significant impact on the environment (Jiang and Shao 2016).

Tianmushan National Nature Reserve (TNNR) in the province of Zhejiang (119°23′47″–119°28′27″E, 30°18′30″–30°24′55″N), lies at the northern limit of mid-subtropical zone and covers a total area of 4284 hm2. The reserve is part of the International Biosphere Reserve (MAB) network and is located in the Yangtze River Delta region, which is the most populous and fastest growing area in China. The area has a damp monsoon climate with an annual precipitation of 1390–1870 mm and an annual temperature of 8.8–14.8°C. The reserve is one of the sites with the richest subtropical higher plant flora in China. More than 2000 species of plants have been recorded from the reserve, including the last surviving wild population of Ginkgo trees. Animal resources of the reserve are also very rich, including 341 vertebrate and 4209 insect species according to current knowledge (Chen 2006). In addition, the reserve has been a famous mountain for Tao religion since the West Han dynasty (around 2000 years ago).

The scenery, rich biodiversity and religious constitution have made TNNR a famous ecotourism destiny in east China (Li 2004). The number of annual visitors has increased from 40 000 to 210 000 in the last 30 years (Wang et al. 2013). In addition, the reserve serves as an important field practice base for more than seventy universities in east China. These activities have had negative influences on the environment of TNNR and its biodiversity (Yan et al. 2009, Zhu et al. 2006). For example, bird song in the reserve has become reduced (Li 2004) and bryophyte diversity, especially liverwort diversity, has declined since 1977 (Li et al. 2006, Wang et al. 2012, 2013).

Figure 1.

The locality of epiphyllous bryophytes in TNNR (green dot).

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In order to better understand the impact of rapid economic development and tourism activities on the environment and the declining biodiversity, we are conducting surveys of bryophyte diversity in TNNR and other mountain areas in east China with support of the Ministry of Science and Technology, China. Bryophytes have been inventoried in TNNR on a regular basis since 1981 (Hu and Wang 1981). In the course of the field investigation in TNNR in the spring of 2017, we found five epiphyllous species, all belonging to Lejeuneaceae (Fig. 1, 2). This is the first observation of epiphylls in TNNR and the northernmost known occurrence of epiphyllous bryophytes in eastern China. Previously, the northernmost location of epiphyllous bryophytes in eastern China was in Qimen County (29°39′N, 117°31′E), Anhui Province, about 200 km south of TNNR (Fig. 3, 4). In view of the declining bryophyte diversity in TNNR, the discovery of epiphyllous bryophytes in this reserve was unexpected.

Figure 2.

The locality of epiphyllous bryophytes in TNNR where the habitat has become a forest ecology teaching point.

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The five epiphyllous species detected in TNNR are listed below together with details on locality, elevation, habitat and voucher number. The importance of the new records is discussed with reference to climate warming and nature conservation.

List of epiphyllous bryophyte species found in TNNR

Cololejeunea japonica (Schiffn.) Mizut.

Near the protection bureau, 30°19′03.3″N, 119°26′90.0″E, 333 m, on Trachycarpus fortune, 26 Apr 2017, J. Wang et al. 20170426-10B (HSNU); 30°18′60.0″N, 119°26′65.5″E, 320 m, on T. fortune, 26 Apr 2017, J. Wang et al. 20170426-20, 20170426-22, 20170426-23, 27 Apr 2017, 20170427-6A, 20170427-8B, 20170427-9, 20170427-10, 20170427-11, 20170427-12, 20170427-13, 20170427-14 (HSNU).

Cololejeunea japonica often occur