| Zhongliang Mountain in Chongqing is a karst valley,which belongs to a typical karst landform.The hazard of rocky desertification in karst areas has been an ecological and environmental issue of great concern in Southwest China for more than ten years.Bryophytes,as the lowest higher plant,play the role of pioneer species in many habitats.It plays a vital role in the improvement of the environmental quality in the initial stage of the habitat.Therefore,more and more attention has been paid to the ecological function of bryophytes in the karst rocky desertification environment.The bryophyte community under different habitat types in the Zhongliang mountain karst area of Chongqing were taken as the research object of this study.Quantitative ecological methods such as cluster analysis,ordination analysis,niche and interspecific association analysis were used to reveal quantitative ecological research on bryophyte communities in different habitat types in the Zhongliang mountain Karst area.It is hoped that can enrich the research content of bryophytes in the karst areas of Chongqing,and provide a scientific basis for the ecological restoration of karst rocky desertification and the protection of bryophyte diversity.The main results are as follows:(1)More than 900 specimens were collected from 540 sampling quadrats in 20 plots of different habitat types in the Zhongliang mountain Karst area.A total of 25 families,46 genera,and 88 species of bryophytes were identified,including 82 species of mosses,6 species of liverworts,and no hornworts found.Pottiaceae and Brachytheciaceae were the dominant families,and their plants accounted for 17.0 % and 18.2 % of the total species,respectively,Brachythecium and Bryum are the dominant genera.The bryophytes in the study area were divided into 6 types of life forms,with the tiling type predominating(36.4 %),followed by the short-clustering type(27.3 %),the high-clustering type(22.7 %),the interweaving type(9.1 %),cushion type(3.4 %)and fan type(1.1 %).(2)Two-way indicator species analysis(TWINSPAN)divided the bryophytes in the 20 plots into the following seven association: Ⅰ Eurohypnum leptothollum + Brachythecium amnicola association,Ⅱ Eurohypnum leptothollum + Brachythecium curtum association,Ⅲ Eurohypnum leptothollum +Barbula subcontorta association,Ⅳ Brachythecium planiusculum + Physomitrium eurystomu association,Ⅴ Plagiomnium maximovicgii+Taxiphyllum taxirameum association,Ⅵ Eurohypnum leptothollum + Rhacopilum aristatum association,Ⅶ Campylopus laxitextus + Campylopus schmidii association.There were no significant differences in species richness,Shannon-Wiener diversity index,Simpson diversity index and Pielou evenness index among different groups(P>0.05).Ward clustering divides it into 8 groups: Ⅰ Eurohypnum leptothollum + Barbula subcontorta association,Ⅱ Campylopus laxitextus + Campylopus schmidii association,Ⅲ Rhacopilum aristatum+ Fissidens cristatus association,Ⅳ Brachythecium amnicola + Barbula subcontorta association,ⅤBrachythecium planiusculum + Physomitrium eurystomum,Ⅵ Eurhynchium coarctum +Plagiomnium maximovicgii association,Ⅶ Eurohypnum leptothollum + Rhacopilum aristatum association and Ⅷ Rhacopilum aristatum + Hypnum plumaeforme association.There was no significant difference in the Simpson diversity index and Pielou evenness index between different groups(P>0.05).The Patrick index and Shannon-wiener index were significantly different among clusters Ⅵ,Ⅶ and Ⅰ(P<0.05).Multiple regression tree(MRT)divides it into 7 association : Ⅰ Bryum billarderi + Fissidens cristatus association,Ⅱ Eurohypnum leptothollum + Rhacopilum aristatum association,Ⅲ Eurhynchium laxirete + Campylopus schmidii association,Ⅳ Eurohypnum leptothollum + Barbula subcontorta association,Ⅴ Brachythecium planiusculum + Timmiella diminuta association,Ⅵ Brachythecium amnicola + Barbula subcontorta association,ⅦEurhynchium coarctum + Rhacopilum aristatum association.There was no significant difference in Patrick richness index,Shannon-wiener diversity index and Pielou evenness index among different community types(P>0.05).The Simpson index was significantly different between clusters Ⅵ and Ⅰ(P < 0.05).Combined with DCA,it is found that among the three methods,the TWINSPAN classification results are more consistent with the DCA analysis results,and the distribution range and boundaries of the clusters on the ordination map are more obvious.The MRT and CCA ranking results are more consistent.At the same time,the main environmental factors affecting the distribution of bryophytes in the study area by CCA analysis were canopy closure,light and rock-soil ratio.(3)The niche breadths of the 17 bryophyte dominant species were 1.000-10.867(Levins index)and0.000-2.550(Shannon-Wiener index).The niche overlap value is between [0.000,0.970],with an average value of 0.193,mainly concentrated in [0.100,0.200],accounting for 64.0% of the total number of species pairs.Among them,the niche width of Eurohypnum leptothollum is the largest and Campylopus laxitextus is the smallest.Among the 136 species pairs,the total association coefficient was 1.334,and there was no significant positive association.The positive and negative correlation ratios of χ~2 test,Spearman rank correlation coefficient and Pearson correlation coefficiet were 0.940 0.720 and 0.490,respectively.More than 71.0% of species pairs showed no significant negative correlation,and the correlation between species was weak.Among them,Rhacopilum aristatum and Bryum billarderi,Rhacopilum aristatum and Fissidens cristatus,Taxiphyllum taxirameum and Eurhynchium coarctum,Hyophila involuta and Plagiomnium maximovicgii are the dominant species pairs,the niche overlap values of them were all greater than 1.000.By fitting the Spearman rank correlation coefficient and Pearson correlation coefficient with the niche overlap value,it was found that the connection coefficient was significantly positively correlated with the niche overlap value.In general,the stronger the positive(negative)interspecific connection of dominant plants,the greater(smaller)the degree of niche overlap.To sum up,this study explored the species diversity of bryophytes in the Zhongliangshan Karst area of Chongqing and the distribution characteristics of moss species in different habitats.It enriches the background data of bryophytes in Chongqing,and provides a reference for the later research of mosses in this area. |
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