Diversity Of Bryophytes And Their Potential In Ecological Restoration From Laowanchang Lateritic Gold Mine, Guizhou

Laowanchang Lateritic Gold Mine,the first lateritic gold mine found in Guizhou,is a kind of karst-collapse-originated lateritic gold mine.The perennial and devastating mining lead to a mass of limestone exposing to the earth's surface and becoming a new type rock desertification.According to our field survey,we found that bryophytes have been the dominant plants on the destructive surface of this mine.870 specimens and samples of bryophytes were collected from this gold mine. The characteristics of bryological biodiversity as follows:(1) It consists of 130 bryophyte taxa in 48 genera and 15 families.Among them,126 moss taxa in 46 genera and 13 families. were founded while 4 liverwort taxa in 2 genera and 2 families were recorded.Pottiaceae,Ditrichaceae,Dicranaceae and Bryaceae are dominant families.Barbula Hedw.and Bryum Hedw. are absolutely dominant genera.(2)The diversity of bryophyte community on lateritic gold sites is quite low while those on limestone and scoria are high,moreover,the bryophyte communities on limestone are pure communities while those on lateritic gold sites and scoria are mixed.(3) The life-forms are Short turfs(70.77%),Tall turfs(12.31%),Cushions(9.23%), Wefts(4.62%) and Mats(3.07%).Among them,Turfs(including Short turfs and Tall turfs) which account for 83.08%are dominant life-forms.(4) The geographical elements of bryophytes are complex,including 12 types in this studied mine, Cosmopolitan is the dominant element,Endemic to China take second place,North temperate element,Eastern Asia are next, Temperate Asian elements,Eastern Asia and North America and so on just take a small proportion.The accumulation of heavy metals in mosses,biomass and quantity of saturated water absorption of mosses,effect of different pH and Hg²⁺ contents to the spore germination rate and growth of moss protonema were analyzed to search the potential in ecological restoration of mine.After analysis we find:(1) Concentration of Au,Ca,Cr,Cu,Pb,Zn,Cd,Co,Hg and As in four mosses[Didymodon vinealis(Brid.)Zander,Trichostomum crispulum Bruchin F.A.Muell,Anombryum gemmigerum Broth,and Tortula yunnanensis Chen],two fibrovascular plants(Pteris vittata L.and Eupatorium adenophorum Spreng.) and their soil were analysed by means of applying the Atomic Absorption Spectrometry.Compared to the soil environmental quality standards of China(GB15618-1995),mean contents of Hg and As are 4.83,15.88 times higher than the recommended standard in soil,respectively.The results showed that Hg and As are the most seriously polluted elements in soil at this mine.The contents of the ten heavy metals in mosses are higher than the contents in the two measured f ibrovascular plants in this mine. According to our analysis for enrichment ability of mosses to elements,Anombryum gemmigerum not only has strong enrichment ability to Au element but also has enrichment ability to Ca, Cr,Zn and Co elements.Trichostomum crispulum has strong enrichment ability to Au element and has enrichment ability to Ca.Tortula yunnanensis has enrichment ability to Pb.The enrichment ability of Didymodon vinealis(Brid.) Zander to the ten heavy metals quite low but it holds quite large biomass that means it presents quite high fastness to these elements.For these four mosses,Cr-As,Au-Cu may cooperate with each other while Au-Hg,Cu-Hg may exclude each other in mosses' absorption.(2)On the limestone of this gold mine,Didymodon vinealis Com.which is the main producer owns large quantity of saturated water absorption.It is a valuable material which can improve the environment of the rock desertification well.According to the analysis of correlation between biomass. and quantity of saturated water absorption of mosses,we find when one mosses has large biomass it also can absorb large quantity water,which shows that quantity of saturated water absorption were relative with the biomass significantly.(3) According to the study on effect of different pH and Hg²⁺ contents to the spore germination and growth of moss protonema, we find that the pH of Funaria hygromitrica Hedw.and Didymodon vinealis(Brid.) Zander both range from 5 to 8,and the Hg²⁺ contents both range from 0 to 0.05 mg/L.The pH of Pogonatum neesii(C.Muell.) ranges from 4 to 7 and accommodate with the content of Hg²⁺ranges from 0 to 0.1 mg/L.These mosses contribute important function to the ecological restoration of degraded ecosystem on lateritic gold mine during the cultivating virgin soil period because of their endurance abilities to high Hg²⁺content in acidic soil environment of mines.