Quantitative Ecology On Bryophytes On The Reclaimed Tailings Of Jianshan Iron Mine

In this study,the bryophyte community under planted vegetation with different restoration years(3-29a)on the reclaimed tailings(dams)of Jianshan iron mine in Loufan county of Taiyuan city,Shanxi province is taken as the research object.On the basic of the filed samplings of bryophyte community and soil,the methods of microscopic observation,quantitative ecological and soil biochemical analyses were used to study the bryophyte species,community composition and floristic characteristics,quantitative ecological characteristics of bryophytes and its soil physical-chemical properties and enzyme activities,to reveal the relationship between the distribution of bryophyte community and environmental factors,and to screen the dominant bryophyte species indicating the improvement of soil fertility and resistant to metals pollution on the reclaimed tailings,so as to promote the ecological restoration of the tailings and provide the scientific basis for the ecological restoration and bryophyte diversity conservation of similar mine tailings.The main research findings are as follows:(1)A total of 4 families,11 genera and 34 species of bryophytes were identified from126 bryophyte quadrats of 21 plots under planted vegetation with different restoration years on the reclaimed tailings of Jianshan iron mine.The dominant families were Bryaceae and Pottiaceae,accounting for 50%of the total families and covering 94.11%of the bryophyte species on the reclaimed tailings;the dominant genera were Didymodon and Bryum,accounting for 18.19%of the total genera and covering 67.65%of the bryophyte species in the reclaimed tailings.From the viewpoint of life form,the bryophytes on the reclaimed tailings could be divided into three types according to life form:short turfs,high turfs and wefts,among which the proportion of short turf was reached at 67.75%.From the viewpoint of zonation,the bryophytes on the reclaimed tailings including seven types of floristic geographical elements,and the distribution type of north temperate zone accounted for 52.95%,which occupied absolute dominance in the bryophyte floristic geographical elements of the reclaimed tailings,which was basically consistent with the composition of bryophyte flora and seed plant flora in Shanxi,as well as the geographical location of the study area,which was belonging to the northern temperate zone located on the Loess Plateau.(2)TWINSPAN classification classified the bryophytes under planted vegetation on the reclaimed tailings of Jianshan iron mine into 12 bryophyte communities with different restoration years,namely:ⅠComm.Bryum caespiticium,ⅡComm.Crossidium crassinerve,ⅢComm.Didymodon tectoru,ⅣComm.Didymodon vinealis,ⅤComm.Bryum capillare,ⅥComm.Didymodon constrictus,ⅦComm.Didymodon constrictus+Barbula unguiculata,ⅧComm.Didymodon constrictus+Bryum turbinatum,ⅨComm.Didymodon constrictus+Bryum caespiticium,ⅩComm.Didymodon rufidulus,ⅪComm.Didymodon vinealis+Bryum uliginosum andⅫComm.Bryum turbinatum.The results of TWINSPAN classification and DCA ordination basically consistent,and overall,with the increase of restoration years,the species diversity of 12 bryophyte communities under planted vegetation with different restoration years on the recalimed tailings of Jianshan iron mine showed a trendency of increasing first and then decreasing,and the bryophyte communities in the middle restoration period(10-20a)had the highest richness.The distribution and species diversity characteristics of the 12 bryophyte communities on the reclaimed tailings were consistent with the restoration years.(3)The positive and negative correlation ratios ofχ~2test,Pearson correlation and Spearman’s rank correlation coefficients of 10 dominant bryophytes under planted vegetation with different restoration years on reclaimed tailings of Jianshan iron mine were less than 1.Most of the dominant bryophyte species-pairs showed insignificant negative correlation,the dominant species were loosely associated with each other,and mostly distributed independently and easily disturbed by external environment.The 10dominant bryophytes had high ecological niches but low overlap values.Among them,the dominant species of Didymodon constrictus had a positive correlation with Bryum caespiticiumis and an extremely significant negative correlation with Didymodon vinealis.These three species had strong ecological adaptability.In the future ecological restoration of abandoned tailings of iron mine,the dominant species of Didymodon constrictus could be used as a dominant species to indicate the soil fertility improvement and heavy metals tolerance,and meanwhile,it could be mixed planting with Bryum caespiticiumis,while Didymodon vinealis fits for mono-planting.(4)With the increase of restoration years,the soil physical-chemical properties of bryophyte communities under planted vegetation with different restoration years on the reclaimed tailings of Jianshan iron mine improved significantly.Among the 12 bryophytes communities,the communities with the highest soil nutrient content,higher enzyme activity,lower heavy metal content and better ecological restoration effects were Comm.Didymodon constrictus+Bryum turbinatum(Ⅷ)and Comm.Didymodon constrictus+Bryum caespiticium(Ⅸ),which were in the middle stage of restoration period(10-20a).Overall,soil total nitrogen(TN),organic matter(OM),alkaline phosphatase activity(ALP),urease activity(URE),iron(Fe),and mercury(Hg)were the major environmental factors limiting the distribution of bryophyte communities on the reclaimed tailings of Jianshan iron mine,and soil available phosphorus(AP),lead(Pb),enzymatic activities of catalase(CAT)and sucrase(SUC)also had some effects on the distribution of bryophyte communities.The Didymodon nigrescens and Bryum turbinatum had strong tolerance to soil iron.(5)Among the 12 bryophyte communities under planted vegetation with different restoration years on reclaimed tailings of Jianshan iron mine,the comprehensive appraisal value of ecological effect of Comm.Didymodon constrictus+Bryum turbinatum(Ⅷ)was the highest and its ecological effect was the best.The ecological effects of Comm.Didymodon vinealis+Bryum uliginosum(Ⅺ)and Comm.Didymodon constrictus+Bryum caespiticium(Ⅸ)were secondly.Compared with the bryophyte community with single dominant bryophyte species,the metacommunity with two dominant bryophytes had better ecological effect.