红壤坡地水力侵蚀对土壤有机碳及微生物影响规律研究

发布时间：2018-06-07 17:30

本文选题：土壤侵蚀 + 模拟降雨　；参考：《湖南大学》2015年硕士论文

【摘要】：全球变暖已成为当前重大环境问题之一,而全球碳循环格局与全球气候变暖有着直接的关系,对全球碳循环的研究正是在全球气候变暖背景下应运而生的科学热点。土壤侵蚀对土壤碳库的影响直接关系全球碳循环格局。然而,土壤侵蚀在土壤碳循环格局中究竟扮演“碳源”还是“碳汇”的角色,目前依然存在着广泛的争议。在这个争议当中较为关键的问题即是由侵蚀作用引起的微生物响应特征尚不明确,从而导致无法准确判断侵蚀对于土壤碳库的具体影响。本研究通过野外径流小区(2×5 m)模拟降雨实验,结合定量聚合酶链式反应技术,研究了水力侵蚀条件下土壤有机碳、全氮、全磷、机械组成和含水率的变化情况,对雨后短期内(10 d)坡耕地表层土壤微生物数量和土壤有机碳动态变化特征进行探讨,并在此基础上探讨了微生物与土壤有机碳间的关系,其主要结果和结论如下:(1)水力侵蚀过程明显改变了土壤有机碳在坡面和剖面的分布格局,并且在不同的雨强条件下有机碳变化特征并不一致,小雨强(0.58mm min-1)更有利于坡面尺度坡下部位土壤有机碳的积累。水力侵蚀条件下,雨强和土壤性质对土壤有机碳的迁移和分布有显著的影响。(2)全氮和全磷在土壤坡面和剖面的分布同样受到水力侵蚀过程的影响,降雨后坡面表层土壤中全氮和全磷含量增高。受到水分下渗的影响,深层土壤中全氮和全磷含量出现不同程度的变化。雨后土壤含水率显著增加而机械组成基本不变。(3)水力侵蚀显著改变了红壤丘陵区表层土壤中微生物丰度在坡面上的分布格局。雨后不同坡位细菌和真菌丰度在短时间内均有较为明显的增长趋势,达到峰值后减少。降雨对细菌和真菌与土壤有机碳之间的关系有极大的扰动,雨后不同坡位微生物与土壤有机碳并未均呈现正相关关系。总之,水力侵蚀不仅直接影响有机碳在土壤中的迁移和分布,还通过改变土壤理化性质影响微生物的生命活动间接影响有机碳在土壤中的动态;同时,水力侵蚀能够直接作用于微生物,改变细菌和真菌丰度和和生命活动直接影响土壤有机碳的分解矿化。因而,在研究侵蚀条件下土壤有机碳动态,应注重土壤微生物对土壤有机碳的具体作用及相应微观机制的研究。
[Abstract]:Global warming has become one of the most important environmental problems, and the pattern of global carbon cycle has a direct relationship with global warming. The research on global carbon cycle is a scientific hotspot under the background of global warming. The effect of soil erosion on soil carbon pool is directly related to the global carbon cycle pattern. However, whether soil erosion plays a role of "carbon source" or "carbon sink" in soil carbon cycle pattern is still controversial. The key issue in this controversy is that the characteristics of microbial response caused by erosion are not clear, which makes it impossible to accurately judge the specific impact of erosion on soil carbon pool. In this study, the changes of soil organic carbon, total nitrogen, total phosphorus, mechanical composition and moisture content under hydraulic erosion were studied by simulated rainfall experiment of field runoff plot (2 脳 5 m) and quantitative polymerase chain reaction (QPCR). The characteristics of soil microbial quantity and soil organic carbon dynamic change in sloping farmland were discussed in a short period of 10 days after rain, and the relationship between microorganism and soil organic carbon was discussed. The main results and conclusions are as follows: (1) hydraulic erosion process has obviously changed the distribution pattern of soil organic carbon on slopes and sections, and the variation characteristics of organic carbon under different rainfall intensity are not consistent. Light rain (0.58mm min-1) is more favorable for soil organic carbon accumulation in the downslope on slope scale. Under the condition of hydraulic erosion, rainfall intensity and soil properties have significant effects on the migration and distribution of soil organic carbon. (2) the distribution of total nitrogen and total phosphorus on the slope and section of the soil is also affected by the process of hydraulic erosion. The contents of total nitrogen and total phosphorus in topsoil were increased after rainfall. Under the influence of water infiltration, the contents of total nitrogen and phosphorus in the deep soil changed in different degrees. The soil moisture content increased significantly and the mechanical composition remained unchanged after rain. 3) hydraulic erosion significantly changed the distribution pattern of microbial abundance in the topsoil of the red soil hilly region. Bacterial and fungal abundance in different slope positions after rain increased obviously in a short period of time and decreased after reaching the peak value. The relationship between bacteria and fungi and soil organic carbon was greatly disturbed by rainfall, but there was not a positive correlation between soil organic carbon and microbes in different slope positions after rain. In short, hydraulic erosion not only directly affects the migration and distribution of organic carbon in soil, but also indirectly affects the dynamics of organic carbon in soil by changing the physical and chemical properties of soil. Hydraulic erosion can directly affect microbes, change the abundance and life activities of bacteria and fungi, and directly affect the decomposition and mineralization of soil organic carbon. Therefore, in studying soil organic carbon dynamics under erosion conditions, we should pay attention to the specific role of soil microbes on soil organic carbon and the corresponding microscopic mechanism.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S157.1

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