Studies On Diversity And Ecology Of Bryophytes In The Periglacial Zones

The alpine subnival belt,a geographical area located between alpine meadows and the end of glaciers,is considered as one of the most extreme habitats on the earth,with harmful limiting factors for plants,including low temperature,low atmosphere pressure,strong ultra-violet radiation,frost,snow,variable climate and large temperature difference between day and night.With the continues of global climate warming,glaciers were receded in vast area on the earth,resulting in newly exposed land known as glacial foreland,which is an ideal place to study the primary succession of vegetation.Bryophytes have strong resistance to cold,drought,and infertility,and are the earliest pioneer plants in glacial foreland.However,because of their small size,bryophytes in glacial foreland are often seriously ignored.There are very few data on the species diversity,reproduction,succession,and life strategies of bryophytes in alpine glacial environments.In this study,we choose four representative glaciers foreland as research sites,are Muz Taw Glacier,Tianshan No.1 Glacier,Xiao Dongkemadi Glacier and 24 K Glacier,to study the species diversity andcharacteristics,community succession,reproduction characteristics and strategies of bryophytes.This study broadens the research area and field of bryophyte ecology,and deepens the research on the reproductive adaptation mechanism of bryophytes to high-stress environments.It is the first time to comprehensively acquire the diversity and evolution information of bryophytes in glacial foreland in China,also enrich and develop the development,evolution,reproduction ecology of plants in the alpine subnival belt environment.And the results are as follows:1.Species diversity and characteristics of bryophytesThe species diversity of bryophyte shows a large difference in different glacial foreland.There are 28 species of mosses in the glacial foreland of Muz Taw Glacier(8families and 13 genera),48 species of bryophytes in the glacial foreland of Tianshan No.1 Glacier(14 families and 42 genera),53 species of mosses in the glacial forelandof Xiao Dongkemadi Glacier(15 families and 25 genera),and 114 species of bryophytes in the glacial foreland of 24 K Glacier(29 families and 60 genera).Including 2 new records of bryophytes in Xinjiang and 10 new records of bryophytes in Tibet.The common characteristics of the species diversity of the bryophytes in the four glacial foreland areas are: Potiaceae and Bryaceae are the main dominant families,and Bryum is the main dominant genus.The proportion of monotypic family and monotypic genus of bryophytes are high,monotypic family is as high as 53.33%and monotypic genus is 72%(both in Xiao Dongkemadi Glacier),which reflects the high degree of heterogeneity and complexity of the environment of glacial foreland.Whats more,monotypic family and monotypic genus are more likely to disappear due to environmental damage,it is necessary to strengthen the protection of the alpine subnival belt areas where the ecological restoration capacity is low.The phytogeographical distribution patterns of bryophytes shows that North Temperate distribution patterns,Artic-Alipne subtypeis is the dominant type,which is consistent with the geographical characteristics of glacial foreland.In the coefficient of similarity analysis,the coefficient of similarity of genus of bryophytes in four glacial foreland are all higher than 50%,which indicates that the bryophytes in the four glacial foreland are closely related to each other.2.Bryophyte community successionThe earliest visible plants in the glacial foreland are bryophytes.The bryophyte species richness in the glacial foreland shows an increases with distance from the glacial,but there are some fluctuations in the middle.The succession process of bryophytes in glacial foreland has obvious regularity: Acrocarpous mosses(such as Bryaceae,Pottiaceae,Ditrichaceae)? Pleurocarpous mosses(such as Orthotrichaceae,Amblystegiaceae,Brachytheciaceae,Hypnaceae).This regularity indicates that Pleurocarpous mosses is more able to adapt to the harsh environment than Acrocarpous mosses.3.Reproduction strategies of bryophytesBryophytes in glacial foreland maintain and renewal their populations through asexual reproduction,which with less investment in reproductive distribution.On the other hand,there is a high percentage of sexual reproduction strategy among them,which invest in the production and spread of spores to colonize newer habitats or to spend the cold season.through this "smart" strategy(both asexual reproduction and sexual reproduction strategy)to maintain their survival and widespread distribution in the glacial foreland.This study shows that dioecious bryophytes are dominated in glacial foreland,which reflecting that the dioecious bryophytes are more adaptable to harsh environments than the monoicous bryophytes.However,the proportion of sexual expression and unsexual reproduction of bryophytes in glacial foreland is not significantly neither in dioecious or monoicous bryophytes,which may affected by environment,life history,individual adaptive ability,etc.There is an obvious female-bias in the dioecious bryophytes in glacial foreland.This pattern is consistent with the gender-bias of the bryophytes.This may be related to the cost of realized reproduction hypothesis: the cost of male expression(antheridium)is higher than that of female(corpusculum)in bryophytes.