Meridian Hill Plant Community Succession And Soil Nutrient And The Relationship Between The Microbial Community

Forest secondary succession is a synergistic development process of numerous ecological factors. Due to the key roles of phytocommunity, soil micro-community and soil nutrient in the process of forest materials circulation and energy flowing, the study on the synergistic succession characteristics as well as relationship among them would be beneficial to comprehensively understand the law and mechanism of forest secondary succession, which is also significant towards the recovery, reconstruction and scientific management of degraded forest ecosystem.This study was based on the research results from forest plant succession in the Loess Plateau, China, taking the communities as the research object which was located in the different succession stages, from abandoned landâ†'grasslandâ†'shrub grasslandâ†'natural secondary forests (Natural secondary forests community also could be divided into three parts, including early successional stage, transitional stage and climax successionial stage);Determination of phytocommunity and composition of soil microbial community and soil nutrient were investigated with the method of the ecology of plant communities, soil microbial ecology (T-RFLP and Biolog etc.) and soil science; The content of synergistic succession characteristics as well as relationship among phytocommunity - soil microbial community - soil nutrient during the natural secondary forests succession in the Loess Plateau based on the multivariate statistical analysis. The research results were as follows:1. Phytocommunity, most soil nutrient indexes and soil comprehensive fertility demonstrated a similar increasing trend during the succession from abandoned landâ†'grasslandâ†'shrub grasslandâ†'nnatural secondary forests;Meanwhile, total soil micro-community diversity exhibited the lowest in abandoned land community but the highest in the grassland community as well as a similar trend between forest and shrub grassland community which located in the middle;as for the different forest communities, the variation among phytocommunity, soil nutrient indexes and soil comprehensive fertility did not reflect their succession relationship; Nevertheless, total soil micro-community diversity demonstrated that climax succession stage was higher than early successional stage.2. As far as phytocommunity and soil micro-community be concerned, if their diversity mean value in different communities demonstrated the higher but their waviness would be the lower in the succession process, and this trend is not vice versa; In some degree, the waviness would reflect the stability of phytocommunity (or different growth pattern) and micro-community during succession. In the phytocommunity, the growth pattern (eg. Herb layer in the grassland community and tree layer of forest community) directly-affected by external environment exhibited a lower diversity but the growth pattern (eg. Herb and shrub layer of forest community) less directly-affected byl external environment exhibited a higher diversity. In the micro-community, soil layer at 0-10cm and 10-20cm was mostly-affected by vegetation succession, its diversity exhibited the higher; but for the layer at 20-40cm, it was seldom-affected by vegetation succession, thereby its diversity exhibited the lower.3. As far as phytocommunity only be concerned, total diversity during the succession demonstrated as follows:climax community (Quercus liaotungensis forest) > shrub land> grassland;In the climax community, its diversity demonstrated as follows:herb layer + shrub layer + tree layer>herb layer + shrub layer>herb layer. Such a corresponding relationship of phytocommunity and the climax community would further illustrate a view that is "The climax community is a complex of succession series", diversity variation in the vertical space of forest phytocommunity could reflect the time course of succession in some degree.4. There was a similar trend between the total soil micro-community diversity and herb layer community diversity of phytocommunity during the process from abandoned land community to the forest community;But among the different forest communities, the variation trend of the total soil micro-community diversity was similar with litter accumulation. It illustrated that variation of soil micro-community diversity was also the reflection of environment variation, in which phytocommunity root system and forest litter and so on would be vital environment influence factors on soil micro-community diversity.5. Plant progressive succession could enhance the improvement and recovery of soil fertility, thereby surface soil layer would be mostly affected and it contrast with the deep soil layer, which determined the soil fertility and its variation. Phytocommunity process is also the differentiation process of soil fertility in different soil layers: variation of soil fertility (increasing trend) from the deep to the surface layer is corresponding with the variation of soil fertility from early plant successionsl stage (abandoned land) to the climax succession stage (forest community), that is variation process of soil fertility in the vertical space is corresponding with its time succession process in the level.6. As for as the phytocommunity diversity, soil micro-community MBC as well as soil fertility, they exhibited a significantly positive correlation among them during the vegetation succession. The improvement of phytocommunity diversity and bio-mass would not merely enrich soil nutrient type, but meet the microbes’needs of soil fertility as well, thereby soil MBC and its fertility level would be improved with the development of succession, which further illustrated that self-fertilization capability is an important mechanism for accumulation and formation of natural phytocommunity fertility.7. The effect of phytocommunity composition on the soil fertility characteristic was investigated via the method of comparing two hierarchical clustering in the filed of "Date mining", the results would reveal the relationship between phytocommunity and soil nutrient at different layers during the succession process in some degree, which would further indicate that the more similar plant composition on the soil surface, the more similar soil physical and chemical and biological characteristics will be.8. Significant difference of 31 carbon source utilization of soil micro-community and its physiological activity as well as functional diversity changed as abandoned land soils were treated by various forest litters. The treatment effect from Quercus liaotungensis and Pinus tabulaeformis demonstrated the similar carbon source utilization characteristics, but the treatment effect from Betula platyphylla was similar with the abandoned land soil (control group);Compare with the litter of Pinus tabulaeformis and Betula platyphylla, promoting effect of litter composition from Quercus liaotungensis on micro-physiological activity and functional diversity was the highest of all the three forest litters, moreover, this increasing promoting effect (from Betula platyphylla to Quercus liaotungensis) was corresponding with the succession stages which the Quercus liaotungensis, Pinus tabulaeformis and Betula platyphylla were located, respectively. Therefore, try to use effective components of the forest litter from local dominant tree species to treat the returning farmland to forest soil firstly in the forestry practice, because it would be beneficial to the survival and growth of tree seedlings and accelerate the forest succession process if the micro-physiological activity and functional diversity were improved. 9. The previous study results on vegetation succession in this region demonstrated that Quercus liaotungensis has more competitive than Pinus tabulaeformis;And Quercus liaotungensis forest is the climax community of the vegetation succession but Pinus tabulaeformis forest is merely the sub-climax, thereby it is speculated that Pinus tabulaeformis forest will develop towards the Quercus liaotungensis forest with the development of succession. In this study, we have also obtained the similar result form the angle of relationship between plant and soil, that is:the similar carbon source utilization characteristics have been obtained from both soil samples mixed-treated by Quercus liaotungensis and Pinus tabulaeformis and soil samples treated by Quercus liaotungensis only, which further illustrated that a decisive role on soil micro-community characteristics from Quercus liaotungensis is more than Pinus tabulaeformis;It can be inferred that Quercus liaotungensis located in the disadvantage originally when it invaded in the forest of Pinus tabulaeformis, after that, it changed the soil micro-community characteristics via the characteristics of itself (eg. litter composition) and this situation will expand its scope, thereby the original soil micro-community characteristics will be changed finally, and the soil environment will be beneficial to the survival and growth of Quercus liaotungensis,and finally, the Pinus tabulaeformis forest would be replaced by the Quercus liaotungensis forest consequently.