| With the concentrated distribution of karst landforms in southwest China,the phenomenon of rocky desertification seriously restricts the level of regional development and threatens the ecological security of the Yangtze River and Pearl River basins,and it is difficult to control rocky desertification.The characteristics of water and thermal ecological factors in karst micro-habitats are different,but the corresponding research is not continuous and not deep enough.Soil microbiota play an important role in the material cycle in the ecosystem and are closely related to the health of plants,but the mechanism of their action by karst habitats is unclear.The study on the effect of karst niches on plant morphogenesis is not deep enough.In order to systematically understand the differences of karst micro-habitats and their effects on microorganisms and plants,and to support the application of rocky desertification ecological control engineering.In this study,a set of soil moisture and temperature data of 40 layers indifferent karst micro-habitats(Rock trough,Rock hole,Rock upside,Rock crevice,Rock gully and Soil surface)and simulated karst micro-habitats systems(bedrock exposed habitat simulating 10~50cm soil thickness and soil surface habitat)were recorded continuously for 2 a to study the spatial vertical and temporal differentiation characteristics of water and thermal ecological factors of karst micro-habitats in the karst plateau.Based on the high-throughput sequencing of DNA,a total of 342 samples were obtained from different layers of the habitats to analysis the soil microbial community ecology.The vertical differentiation of soil microorganisms in the micro-habitats and their change in the process of vegetation succession were analyzed,and the response of soil microorganisms to the ecological factors of karst micro-habitat was studied.Based on LC-MS technique,the root metabolism and functional traits of 184 samples treated with ecological factors of simulated niche were measured,and the effects of micro-habitats on plant functional traits and root metabolism,the correlation between root metabolites and functional traits affected by micro-habitats,and the interaction between root metabolites and soil microorganisms affected by micro-habitats were studied.The main results are as follows:(Ⅰ)The exposed bedrock leads to different temperature characteristics of karst micro-habitats soil in spring,summer,autumn and winter.The soil temperature of bedrock exposed habitat is 1-2 ℃ significantly higher than that of Soil surface micro-habitats in summer,but significantly lower than that in winter.The deepening of soil thickness in the micro-habitat will alleviate the temperature difference caused by bedrock exposure,but there is still a big difference in the same horizon.In addition,the bottom of the micro-habitat where the bedrock is exposed is disturbed more quickly and greatly by external heat.In addition to seasonal factors,habitat soil thickness largely determines the characteristics of habitat soil temperature,and the difference of soil types also has a certain influence.The shallower the soil thickness of the exposed bedrock is,the faster it is affected by the external environment.In the field observation,the type of micro-habitat is the main reason for the difference of soil moisture in karst micro-habitat,followed by the soil layer.In the same horizon,the soil moisture in the micro-habitat which exposed bedrock is 5%(Volume percentage)lower than that in the soil surface habitat.The interaction of soil layer,thickness and type determines the variation characteristics of soil moisture.The surface and bottom soil in the exposed bedrock micro-habitat are greatly affected by precipitation,while the Soil surface micro-habitat is greatly affected it only in the surface layer.The control experiment shows that the soil thickness in the micro-habitat is the most important factor of soil moisture,but the conditions affecting soil moisture are complex and need to be further verified.The Soil thickness of 40 cm may be the critical point of soil moisture variation in the micro-habitat where bedrock is exposed.(Ⅱ)The main factors affecting the composition of microbial community are the stage of vegetation succession,slope position and other comprehensive factors.The type of micro-habitat had a significant effect on the construction of soil microbial community in the grass stage,but had no significant effect on the micro-habitat in the shrub and tree stage,it indicating that with the vegetation succession after the micro-habitat was obscured by the plant canopy,the difference of ecological factors in micro-habitat types decreased.The results support that the biological factors of the plant community have a decisive effect on soil microbial community composition.The phenomenon of accompanying succession of soil microorganisms in the process of vegetation succession was recognized in this study.Under the condition of controlled experiment,it is recognized that the composition of soil microbial community is affected by soil thickness,precipitation pattern and frequency and soil layer.The exposed bedrock changed the composition of soil microbial community.The meteorological factors of micro-habitat can explain the variation of soil microbial community.The effects of environmental factors on the dominant species and functional groups of soil microorganisms are different,but it is certain that they are not significantly affected by biological environmental factors on the micro-habitat level.(Ⅲ)Ecological factors such as soil type,soil thickness,water supply mode,precipitation frequency and their interaction of micro-habitat have significant effects on plants.The phenomenon of multi-factor interaction is smaller than that of single factor interaction.The composition of chemical elements of soil in micro-habitat has a great effect on plant metabolism,which the ratio of carbon to nitrogen is the most significant.In this study,the soil bacterial groups significantly associated with the metabolites of medicinal active components of 0)(64)(6 7)(7(6(6,and the relationship between the metabolites of 0)(64)(6 7)(7(6(6 and functional traits were obtained.A path model for micro-habitat ecological factors to regulate the metabolites of Pueraria lobata was established.Some conclusions are obtained: Soil moisture,Heat / temperature characteristics of Karst Microhabitat were changed by bare rock exposure.The characteristics of water and heat in karst microhabitat were different during early stage of vegetation succession there are vegetation coverage low and community level simple.It significantly affects the composition of soil microbial community in micro-habitat,but the difference of this micro-habitat decreases with vegetation succession there were high vegetation coverage and complex community level,that is,the uniformity of abiotic environmental factors increases.The difference of soil microbial composition in climax community vegetation is mainly affected by biological factors and their derivative factors.The effects of microhabitat type differences on the composition of microbial community are mainly affected by habitat soil type,soil thickness,water characteristics and their derivative factors.These factors also affect the performance of plant functional traits and the relationship between soil microorganisms and plant functional traits. |
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