| The paleo-periglacial landforms developed in the territory of the Liaodong mountainous,which affected by the climate of the last glacial period.Dense gravels packing on the slope surface,and the succession of overlaying vegetation were extremely slow,which led to instability of landforms,such as landslides,debris flow,etc.The regional ecological environment of research area has obvious features on periglacial and locates at the highly ecological-sensitive areas.However,we have to face the truth that most of the researches on the paleo-periglacial landforms are focus on vegetation characteristic,soil characteristics or few of simply geomorphologic survey,but none of the community stability,which take into account the substrate surface and vegetation coverage.In view of the reinforce and coalition of vegetation coverage on the paleo-periglacial landforms,especially the mountain Laotudingzi be concentrated with the paleo-periglacial landforms,the research focused on the plant community characteristics without human disturbance,by means of the conventional landform survey,investigation of plant community,site environmental factors and the sample analysis in the laboratory,mathematical model analysis and quantitative analysis of vegetation.And then,we could excavate the content of community stability on paleo-periglacial landform,and assess the stability level of plant community,what's more,we plan to study the basic features of their own community and site conditions when the plant community was stable under natural conditions.The results not only provide a scientific basis for the forestry management and soil and water conservation in paleo-periglacial areas,but also afford the follow-up researchers some useful basic data.And the achievement was beneficial to expand the geography of plants and periglacial geomorphology research,as well as maintenance of ecological safety and environmental benefits of Liaodong mountainous,and has important scientific significance in theory and practice.The main conclusions as follow:(1)Based on the investigation and study of the periglacial landforms in Mt.Laotudingzi,which places as the centered of Nature Reserve in eastern Liaoning.From the observed it showed that the types of extensively developed periglacial landforms in this region involved the Block stream,Rock slope,Rock block field,and occasionally,Rock fort,Nivation Swale,gelifraction collapse and Talus rock.The rock stream usually develops in the range of 690-1,130 meters and located on the slope of about 5 degrees to 35 degrees,which mainly concentration of 850 meters.The rock slope usually develops in the range of 820-1,300 meters and located on the slope of about 20 degrees to 35 degrees,which mainly concentration of 1,160 meters.The rock block field usually develops on the mountaintop above 1,300 meters and located on the slope of about 7 degrees.The combination of the glacial landform was Rock fort-gelifraction collapse-Rock block field-Nivation Swale-Talus rock-Rock slope-Rock stream,along the changes of elevation successively in accordance to the complexity of periglacial landforms development.And the glacial agency changes from simple frost heaving-gravitational process to frost heaving-heat melting-nivation—abrasion synthetic action;it reflected the trend of periglacial processes was changes from simple to complex with the decrease of elevation.(2)Affected by paleo-periglacial process,the stony slope was widely developed here.The gravel matrix was composed of gravels,which covered by lichen,moss,etc.The granite,gneiss dominated gravel accumulates on the surface in disorder,forming the thickness of a few meters to tens of meters and roundness of grinding is mostly sub-roundness.Different topographic have different gravel formation characteristic.On rock stream,the long axis of the stone river landform between 30.9 to 183.9cm(the average was 104.5cm and the coefficient of variation was 47.2%),AB surface of gravel tendency 129 to 212 degrees and the dip angle with 26 to 54 degrees.The gravel long axis ranged value of rock slope landforms from 26.8 to 164.6 cm(the average was 93.5cm and the coefficient of variation was 41.8%),AB surface of gravel tendency 126 to 324 and the dip angle with 29 to 62 degrees.The gravel long axis ranged value of rock block field from 39 to 168 cm(the average was 89.3cm and the coefficient of variation was 43.3%),AB surface of gravel tendency 156 to 237 degrees and the dip angle with 25 to 43 degrees.It's reflecting that the steep rock stream and the rock slope developed in the formation of gravel in disorder were more susceptible to rolling.The gravel matrix was hard for the formation and stability of plant community development,which difficult to conserve water,heat and substrate of fertilizer.The characteristic of terrain,soil,meteorological and hydrological conditions exhibited asymmetrical in north and south slopes.The vertical gradient is larger on the North Slope which has obvious vertical zone spectrum,and the paleo-periglacial relics also be found universally.Based on the investigation and fieldwork,the undisturbed soil samples were returned and pretreated,the grain size characteristics of the overlying soil in 48 sample plots here were analyzed,it is found that most of the soil particles are fine,and the soil texture is mainly dominated by clayey silt.The soil texture is made up of clay(20.79%)and silt(69.54%)and sand(9.67%).In combination with electrical conductivity,salt content and soil temperature,soil pH,magnetic susceptibility,ignition loss,such as mutual reflect,In combination with electrical conductivity,salt content and soil temperature,soil pH,magnetic susceptibility,ignition loss,such as mutual reflect,Low altitude section thickness is bigger(the mean between 7.5?95 cm,38.2 cm)of the weak rock stream landscape soil acidity(4.11?4.11,the average is about 4.9),less leaching,high organic matter content(22.15%)in the soil solution environment conducive to hydration,hydrolysis and microbial activities,soil role in optimal;High altitude of rock slope in soil(thickness between 6.5?90 cm,average 20.6 cm)leaching is bigger,strong acid(3.87?3.87,the average is about 4.5),the soil is poor;High altitude of sihai soil is slightly heavy and is easy to be washed out,but higher organic matter content(17.11%),conducive to plant growth.Chemical element analysis showed that soil zone soil mineral elements content is rich,but had different degree of elements for all kinds of landscape of soil leaching,migration,especially in high altitude of rock slope landforms in soil significantly;Lower altitude and vegetation good stone river landscape soil element migration quantity is small.Abundant rainfall in this area supplies(summer precipitation of about 223 mm),appropriate sunshine,temperature and humidity(summer temperature is 21.6?,10? accumulated temperature can reach 670?)and a large quantity of surface ground cover accumulated to a great extent,make up the disadvantage of poor matrix,and it has many rivers development,formation and stability of plant community development provides a strong support.(3)The types of vegetation in the study area inherited from the ancient Tertiary flora,with the characteristics of Changbai and North China flora.Affect by the glacial process,the vegetation here lived through the climatic cycle of warm-wet to wet-cold to warm-wet.Influenced by this,the species composition was changed from the type of simplifying to complex,and to simplifying,correspondingly,the changes of plant morphology has the similarly trend.Plant communities can be divided into 16 forest formations and 6 shrub formations,vegetation types could be categorized as deciduous broad-leaf forest,coniferous forest,coniferous forest,elfin forest,and scrub and shrub bushes.The vegetation types sequentially distributed with altitude gradually increased,showing a vertical arrangement law.The diversity and similarity analysis showed that the species diversity of coniferous and broad leaved mixed forest was enlarged due to the edge effect of the community,and the plant communities far away from the each other in altitude were at lower similarity,indicating which hydrothermal conditions have a significant impact on plants in the area for the vertical distribution of the main reasons limited by elevation.68 families,138 genuses and 193 seeds on the periglacial landform of Mt.Laotudingzi were recorded during the research,including pteridophytes of 8 families,10 genuses and 14 seeds,gymnosperm of 1 families,3 genuses and 4 seeds,dicotyledon of 53 families,106 genuses and 150 seeds,monocotyledons of 6 families,19 genuses and 25 seeds.Among the plant community of the periglacial landform in Mt.Laotudingzi are Phanerophyte which takes up 38%,Cryptophyte which occupies 36.3%,and Hemicryptophyte occupied 21.8%.There are few Chamaephyte and Therophyte.In addition,the proportion of seedlings and saplings proportion of the dominant species in each sample plot was about 30%,and a large number of pioneer plants were found in the landscape environment.All of these reflect that the microclimate in the periglacial landform of mountainous region in Liaoning is that the area is warm and rainy in summer,while it is cold and lasts long time in winter,and the natural regeneration potential of vegetation is relatively large.(4)The stability of the plant community in the paleo-periglacial landform not only depends on its own growth and development status,also involve the substrate condition,topography,soil environment,meteorological hydrological aspects of mutual influence.And it could join the physical and chemical factors of paleo-periglacial inorganic to biotic factor of organic world with vegetation at the core.Under the influence of mutual promotion,restrictive,adjustment of different site factor,the paleo-periglacial plant community could keep their sustained development.The selection of index factors was from the viewpoint of intensive cultural meaning of architecture(eg.Vegetation coverage,species richness and species diversity etc),the architectural stability was constructed and evaluated based on entropy-weight and matter-element extension mode.The results show:Stability level for II survey sample area accounted for 39.6%,level for level III accounted for 43.8%,level in ?and V accounted for 12.5%and 4.1%,that is to say,the samples of stability level of"medium" and "relatively high" accounted for more than 80%,so,the paleo-periglacial plant community was in the stability level of "medium" and "relatively high".The stability of the overlying vegetation on rock stream each was "relatively high"(41.7%)and "medium"(58.3%).The stability of rock slope each was "relatively high"(47%),"medium"(35.3%),"relatively low"(11.8%),"low"(5.9%).The stability of the overlying vegetation on rock block field each was "relatively high","medium","low"(14.3%),and "relatively low"(57.1%).The vertical distribution of stability has gradually decreased with the increase in elevation,and the horizontal distribution of stability was shown in the form of mountaintop-centered and radiated outwards,which gradually increased from inside to outside. |
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