| The Northern Yanshan Mountain, a geographical district on the northern edge of North China, and the northern part of which is adjacent to the grassland, lies in the transitional zones of the Northeast China and the Northern China broad-leaf forests. The Chifeng loess hilly area is on the northern verge of the extended loess region, and the hilly and its adjacent Horqin Sandland are the interleaving zones of agriculture and stock farming. Because of the sensitivity and vulnerability of the ecological environment, the study on the bryophyte flora and its ecology in the three landforms is very important and practical.Through a systematic study on the 2,140 bryophyte specimens collected from 10 collecting localities , 48 families, 121 genera and 279 species (including subspecies and varieties) of bryophytes are found in the whole research area, and which respectively occupy 76.19%, 65.76% and 54.60% of the total number of the bryophytes in Inner Mongolia. Among them, 18 families, together with their 22 genera and 44 species, belong to Hepaticae; 1 family, together with its 1 genus and 1 species, belongs to Anthocerotae; 29 families, together with their 98 genera and 234 species, belong to Musci. 1 genus and 7 species of these bryophytes are newly recorded in China. 1 class, 3 families, 11 genera and 36 species are new in the Inner Mongolia Autonomous Region. These findings have built up the study on the composition of the bryophytes in both China and Inner Mongolia.Similar to the whole research area, there are altogether 47 families, 119 genera and 273 species (including subspecies and varieties) of bryophytes in the Northern Yanshan Mountain. In Inner Mongolia, the families and their genera and species make the mountain only second to Northern Great Khingan Mts, a place which is also rich in bryophytes. A pilot study in the Chifeng loess hilly area displays 9 families, 20 genera and 27 species of bryophytes. There are 17 families, 38 genera and 69 species of bryophytes in the Horqin Sandland. Because 100% of the families, 100% of the genera and 96.30% of the species in the Chifeng loess hilly area, and 94.12% of the families, 94.74% of the genera and 92.65% of the species in the Horqin Sandland are found in the Northern Yanshan Mountain, this area is considered highly comprehensive. Along with the transition of the collecting localities from the forest area to the forest-steppe area and then from the forest-steppe area to the grassland, the quantities of the families, the genera and the species of the bryophytes decline remarkably. The liverworts and the percentage of Pleurocarpi-muscorum also show an obvious tendency of decrease.However, the percentage of Acrocarpri-muscorum progressively increases.Being a phytogeographical complex region, the whole research area has 10 types of bryoflora compositions, which, including the percentage, are listed as follows: 35 species of Cosmopolitan, 3 species of Pantropical elements (1.23%), 3 species of Tropical Asian elements (1.23%), 2 species of Tropical Asian-African elements (0.82%), 148 species of North Temperate elements (60.66%),7 species of Asian and North American elements( 2.87%), 7 species of Old World Temperate elements(2.87%), 4 species of Temperate Asian elements(1.64%), 56 species of East Asia elements (22.95%) and 14 species of Endemic to China elements (5.74%).There are respectively 10 kinds, 6 kinds and 9 kinds of elements in the mountainous area, the loess hilly area and the sandland. In the three landforms, the major phytogeographical compositions of bryoflora are the North temperate element and East Asia element, the former of which reaches the highest percentage (72.22%) in Chifeng loess Hillyland, and the latter of which reaches the highest percentage (23.11%) in the northern Yanshan Mountain, the second high in the Horqin Sandland. The fact that the northern Yanshan Mountain has more proportion of the East Asia element than the whole research area and contains almost all the East Asia elements in the other two areas shows that it has an important influence on the loess hilly area and the sandland. Among the 10 collecting localities of bryophytes, the Heilihe national natural reserve ranks the first in the quantity of the East Asia element, 34 species are found in this collecting localities.The highest proportion of the East Asia element, which is 26.19%, is that of the Daheishan natural reserve, the most concentrative distribution area of the East Asia element in Inner Mongolia.In the Principal Component Analysis on the species percentage of each families, the Northern Yanshan Mountain keeps the nearest distance with the southern Khinggan mountain, and then the Yinshan mountain, in addition to Helan Mountain and Wuling Mountain. It has the characteristic of being the transitional zones between the wetting forest area and the arid steppe area, between the cold-intermediate temperate and the warm temperate zone, and among Chinese bryophytes flora of North China, Northeast China and Neimenggu-Xinjiang.In the comparison of generic and specific similarity coefficient and phytogeographical compositions of bryoflora in the 8 mountains, high similarity is found between the bryoflora in this area and those in the Southern Great Khingan Mts, less in Wuling Mountain, and then in Northern Khinggan Mountain and Yinshan Mountain. The Northern Yanshan Mountain, through which the East Asia elements immigrates to the mountain in the steppe area , contains 95% and 71.43% East Asia element of the Southern Great Khingan Mountain and Yinshan Mountain respectivley. Simultaneously comprised of xeric-mesic, mesic and mesic-meso species, its East Asia element contains both the Sino-Japan elements and the Sino-Himalaya elements, whose percentage is lower than that of Xitianmu Mountain and Changbai Mountain , and slightly higher than that of the Wuling Mountain. All these reflect obvious East Asiatic and North China characteristics of this region. The quantities of families, genera and species in the Chifeng loess hilly area are less than those in the Aguin Sum area of Erdos, and the percentage of Northern temperate element and East Asia element is similar in two area. The quantities offamilies, genera and species in Horqin sandland are obviously higher than those in Mu Us Sandland, Hobq Desert and Shapotou region of the Tengger Desert. Phytogeographical compositions of bryoflora are the most complicated in the four areas, and there are 9 species East Asia element which occupy 15.79 percent of the total quantity of species. The phytogeographical compositions of btyoflora in the other three area are mainly comprised of Northern temperate element and Cosmopolitan element, while the East Asia element does not distribute there. By the statistics of distribution of species in the loess hilly area and the Sandland (desert), we found that some species indicate the inseparable connection between the loess hilly area, the sandland (desert) and their adjacent mountainous area.The study on the composition and the community of bryophytes in different vascular plant vegetation forms show that there are 41 families (85.42%), 93genera(76.86%) and 186 species(66.67%) of bryophytes in the forest vegetation belt mainly comprised of Populus and Betula, and the overwhelming majority of liverworts and Pleurocarpi-muscorum in the whole research area distributes in this forest belt. Among them, 24 species of liverworts and 78 species of mosses are not found in other vegetation forms, which are asking for diversity protection. Compared with the forest vegetation forms, the bryophytes are much fewer in the steppe and scrub vegetation forms. As the habitats change, from the steppe to the xeric-mesophytic scrub, and then to the open forest and the forest forms of different moisture conditions, the dominant bryophytes species in the community also correspondingly change in the following order:Acrocarpri-muscorum-^Liverworts+Acrocarpri-muscorum—>Pleurocarpi-musc-onim+Liverworts+Acrocaipri-musconmi^Pleurocarpi-muscorum+Liverworts. Rock epixylophytia and putridae epixylophytia community begin to appear, and the quantity of the dominant species of bryophytes gradually increases. For the ground community, rock community, epixylophytia and putridae epixylophytia in the whole research area, the dominant species of bryophtes preliminary acknowledge 46, 35, 7 and 9 species respectively. Some of these species are single substrate, yet some can keep their dominant position in more than two kinds of substrates, and they indicate that substrate and air moisture are the more important factors than the substrate types are in influencing the distribution and the population growth of some bryophytes. In addition, the same shrub and forest forms on different textural soils have high similarity in the composition of the dominant species and the companion species.73 species of ground bryophytes are found in the species diversity research on ground bryophytes in typical habitats, in which the quantities of the ground bryophytes change between 7 and 32 species. In these habitats, 1 or 2 species have very high importance value in the shrub, the meadow and the open forest plots. Bryum argenteum in the Caragana microphylla shrub on fixed dune of sandland has the highest importance value of 76.67%. For the 10 plots, ground bryophytes Shannon-Wiener index are between 0.4048 and 1.2617, species richness are between 1.067±0.203 species/quadrat and 7.167±0.966 species/quadrat. Beta diversity index are between 0 and 0.667, and the coverage are between 3.081%±0.481% and 17.557%±2.386%. The species quantities, richness and the Shannon-Wiener index arethe lowest in the Caragana microphylla shrub on fixed dune of sandland. species quantities and richness are the highest in the Quercus mongolica forests. The Shannon-Wiener index is the highest in the Pinus tabulaeformis forests. Because most of the species in Quercus mongolica forests and Pinus tabulaeformis forests are Acrocarpri-muscorum, this diversity is unstable and fluctuating. The dominant species of Bryum argenteum, Didymodon vinealis, Barbula indica, Entodon compressus, Brachythecium salebrosum can adapt themselves to the broad water ecological amplitude, and may be exploiting species in the ecological succession from xerophytic to xeric-mesophytic habitat and mesophytic habitat with relatively higher moisture. By the linear regression, we found that the species quantities are correlated with canopy density (P<0.05), Shannon-Wiener index of bryophytes are positively correlated with environmental variables of soil moisture and negatively correlated with the coverage of herb layer(P<0.05), and the coverage of bryophytes and species richness are not correlated with all the environmental variables(P>0.05) .There are 73 species in 12 families and 35 genera involved in the formation of the soil microbiotic crusts in the whole research area, in which most species belong to Pottiaceae and Bryaceae of Musci and Grimaldiaceae of Hepaticae. In these species ,3 species including Crossidium chloronotos, Pterygoneurum subsessile and Aloina obliquifolia distribute in the xerophytic habitat, 40 species are found from xeric-mesophytic to mesophytic habitat, and 3 species including Bryum argenteum, B. capillare and B. dichotomum are found from xerophytic to hygrophytic habitat. In the 17 plots , there were at most 23 species under the Ulmus macrocarpa open forest in Northern Yanshan Mountain, and the coverage of bryophytes in the habitas is 8.661percent, and Mannia sibirica occupys 37.18 % of the total coverage in the crusts. The highest bryophytes coverage of 35.17% is under the artificial Picea sylvestris var. mongolica forests on the fixed dune at the Naiman Station of Horqin Sandland, and Bryum argenteum keep very obvious dominant with its coverage making up the total coverage between 98.15% and 100% in all kinds of habitats around the station. In the loess hillyland area , the highest bryophytes coverage of 9.382% is under the Zizyphus jujuba var.spinosa shrub on the light loamy soil ,and the dominant species of Didymodon vinealis occupys 56.28% of the total coverage.In order to progressively reveal the formation and maintenance of the bryophytes crusts, the morphological and structural properties of 5 species of liverworts and 6 species of mosses are compared respectively, and 2 different experiments of the asexual reproduction(broadcast planting and offshoots) of Bryum argenteum and Didymodon vinealis are respectively done. All the results are listed as follows: 1) Drought resistance of Riccia sorocarpa and Rsetigera are stronger than the other 3 species; Targionia hypophylla and Plagiochasma rupestre' are inferior than the others, and M. sibirica' are in the middle of 5 species of liverworts. 2) The leaf cells of Crossidium chloronotos pterygoneurum subsessile and Aloina rigida have obvious differentiation. Their leaf structures are more complex than other species; the plants of the dominant species of Bryum argenteum and Didymodon vinealis grow densely, the stems of which have distinct central strand and small obvious incrassation on thesclerenchyma of the external cortex. 3) the plants of Mannia sibirica are larger than that of Riccia sorocarpa and R.setigera , grow densely , and easily formed big area crusts by forked ramification on the uncovered soil in the xeric-mesophytic habitat such as the Ulmus macrocarpa open forest. 4) Bryum argenteum and Didymodon vinealis reproduce easily through the fragments of the plants and gemmae; there are two main reproduction approaches, one of which is that the stems continually branch and produce young plants, and the other of which is that the young plants, gemmae and the fragments of the stems and leaves repeatedly and extensively reproduce protonema which develop into a large number of new plants finally, and the protonema extend easily in the sand soil and light loamy soil through which the moss crusts continuously occupy the plots with high coverage.
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