Ecology Of Bryophytes From Karst Waterfalls In Southwestern China

Karst waterfalls are one of the special ecosystems that interest ecologists, geologists and environmental scientists. China is one of countries in the world with thousands of karst wa- terfalls of different types and economic importance. The landscapes of karst waterfalls are important for a lot of world heritage sites, national natural reserves and national scenic spots in southwestern China, for example, Huangguoshu Waterfalls in Guizhou, Jiuzhaigou Waterfalls and Huanglong Waterfalls in Sichuan, Nine-Dragon Waterfalls in Yunnan and Detian Waterfalls in Guangxi. All of them are important for biodiversity conservation, tourism and basic science research.From October 2004 to August 2007, many surveys were conducted in the karst area of southwestern China. About 2100 samples and specimens were collected from 86 active karst waterfalls. The growth rates of six aquatic mosses were measured at eight karst water- falls in the field from August 2005 to August 2007. By means of Atomic Absorption Spectrometry (A Analyst 800) and Atomic Fluorescence Spectroscopy (AF-640), contents of seven metal elements of eight mosses and water samples were analysed from eight karst waterfalls in Guizhou Province. To understand the general features of aquatic bryophyte communities of karst waterfalls, we made a comparison of bryophyte communities of 36 karst waterfalls from southwestern China and western Europe.Major results are summarised as follows:1) Based on a series of investigations for 86 karst waterfalls in southwestern China, a classification system of karst waterfalls was proposed. According to the characteristics of karst water sources and karst landforms, karst waterfalls were divided into two types, and subdivided into four subtypes and further into twelve small types. Distribution and features of karst waterfalls were discussed.2) The bryoflora of karst waterfalls consisted of 248 species (including varieties and subspecies) in the southwestern China, which belong to 92 genera and 34 families. Five occurrence frequencies of bryophytes in karst waterfalls were distinguished: very rare species (134 taxa, 54.03%), rare species (81 taxa, 32.66%), frequent species (11 taxa, 4.43%), occasional species (17 taxa, 6.86%) and common species (5 taxa, 2.02%). The phytogeo-graphical elements of the bryoflora included Tropical Asian (20.97%), Pantropical (1.21 %), Tropic Asian to Tropic African (1.21%), East Asian (19.35%), North Temperate (20.57%), East Asian and North America disjuncted ( 1.61% ), Old World Temperate (1.21%), Temperate Asian elements (4.03%), Endemics to China(14.5%) and Cosmopolitans (15.32%).3) According to the differences of bryophytes in ecological adaptation to calcite ions, three ecological groups were identified: travertine bryophytes (38 taxa, 15.32 % ), calciphilous bryophytes(98 taxa, 39.52 %) and eurytopic bryophytes (112 taxa, 45.16%). Vegetative propagations of bryophytes were common while sporophytes with capules were very rare. The reproductive systems consisted of five types, dioecious taxa accounted for 81.45%. Interestingly, we found that there were four different areas in shoots of mosses that might be associated with ecological adaptation, i.e., green growth area, half-calcification area, calcification area and petrification area. Calcification and petrification of shoots allow bryophytes to be successful competitors in harsh environments characterised by fast water flow, rich calcite and rapid deposition.4) Growth rates were obtained for six mosses from eight karst waterfalls every month in Guizhou province from August 2005 to August 2007. The estimated rates per annum were as follows: Fissidens grandifrons 1.283 cm, Hydrogonium dixonianum 2.072 cm, H, williamsii 2.35 cm, Gymnostomum recurvirostre 1.76 cm, G aurantiacum 0.883 cm, Cra-toneuron filicinum 1.56 cm. The results were discussed with reference to karst depo si- tion, water chemistry and water flow rate. Seasonal patterns of growth of six moss species were investigated in field, and significant differences in relative growth rate were observed between species.5) The results showed that the element contents in plants were higher, and that the element contents in plants were related to those in water. Moreover, the capacities to absorb and enrich elements varied among bryophytes. We found that Hydrogonium majusculum and Philonotis turneriana had strong ability to enrich Zn and Ca, Gymnostomum aurantiac- um and Calliergon cordifolium Zn and Cu, Hydrogonium dixoniana and Cratoneuron filicinum Zn, and Reimersia inconspicua and Fissidens grandifrons Cu, Pb and Zn. Therefore, our results suggest that these bryophytes may have ecological tolerance of different metal elements in water from karst waterfall in the area, hence can be used as indicators of metal contamination.6) Comparative studies of characteristics of bryophyte communities were conducted between 18 karst waterfalls in southwestern China and 18 karst waterfalls in western Europe. We found that 30 aquatic bryophyte communities consisted of 61 taxa belonging to 27 genera and 12 families in China, whereas 28 aquatic bryophyte communities consisted of only 33 taxa belonging to 24 genera and 15 families in Western Europe. Although there were some differences in typical bryophyte communities, we found common features of southwestern China and western Europe, including life-forms and ecological distribution types of bryophyte communities.7) A new classification for bryoliths associated with karst waterfalls was proposed. According to the features of environmental factors and bryophyte communities, four ecological types (stream waterfall deposition, river waterfall deposition, dam deposition and cave deposition ) and 16 subtypes of biokarst depositions associated with bryophytes could be distinguished.8) From the viewpoint of biodiversity conservation of bryophytes in the karst area, 20 bryophyte taxa were suggested to be priority species for biodiversity conservation at karst waterfalls in southwstern China, i.e., Fissidens grandifrons Brid., Hydrogonium dixonianum Chen, H. majusculum (C. Muell.) Chen, H. gracileutum (Mitt.) Chen, H. consguireum (Thwait et Mitt.) Hilp., H. setschwanicum (Broth.)Chen, H. williamsii Chen, Gymnostomum recurvirostrum Hedw., G subridulum (Broth) Chen, G aurantiacum(Mitt.)Jaeg., G aeruginosum Sm, Anoectangium clarum Mitt., Cratoneuron filicinum (Hedw.) Spruce., Palustriella commutata (Hedw.) Ochyra, P. falcata (Brid.) Hedenas, Philonotis calcarea (B.S.G) Schimp., P. turneriana (Schwaegr.) Mitt., Bryum pseudotriquetrum (Hedw.) Gaerth, Barbula tophacea (Brid.) Mitt. and Cyathodium cavernarum Kunze.