Microbial regulation of nitrogen dynamics along the hillslope of a natural forest
Microbial regulation of nitrogen dynamics along the hillslope of a natural forest
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DOI：
10.3389/fenvs.2014.00063
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发表时间：
2015-01
影响因子：
4.6
通讯作者：
K. Isobe;N. Ohte;T. Oda;Sho Murabayashi;Wei Wei-Wei;K. Senoo;N. Tokuchi;R. Tateno
中科院分区：
文献类型：
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作者：
K. Isobe;N. Ohte;T. Oda;Sho Murabayashi;Wei Wei-Wei;K. Senoo;N. Tokuchi;R. Tateno
地形影响土壤物理化学、土壤氮素动态以及森林中植物的分布和生长。在日本，许多森林分布在山区，这些特征在陡峭的山坡上往往是高度可变的。在这项研究中，我们研究了微生物种群动态如何反映沿日本天然林土壤中沿坡面的物理化学梯度的生物有效氮动态。采用N同位素稀释法测定了土壤中NH_4~+产生、硝化和NH_4~+/NO_3-−固定化的总速率，分析了土壤中N的动态变化。我们还用定量聚合酶链式反应测定了细菌16S rRNA基因和细菌及古生菌氨单加氧酶基因(AmoA)的丰度，以评估细菌总数和硝化细菌的数量。研究发现，坡面下部土壤NH4+产生速率和硝化速率较高，分别与细菌16SRRNA基因丰度和古生菌AMOA丰度呈正相关；坡面下部由于微生物硝化活性较高，微生物NO3−固定化活性较低，植物对N的有效性较高，尤其是NO3−。通径分析表明，NH4+产生速率和硝化速率主要受底物(溶解有机N和NH4+)浓度和总细菌和硝化细菌种群大小的调节，其种群大小受土壤理化性质如pH和水分的强烈影响。我们的结果表明，沿坡面的土壤物理化学梯度通过改变森林坡面的氨化细菌和硝化细菌群落而导致NH4+产生和硝化速率的空间梯度，并通过向植物提供生物有效氮来影响植物的分布和生长。
Topography affects the soil physicochemistry, soil N dynamics, and plant distribution and growth in forests. In Japan, many forests are found in mountainous areas and these traits are often highly variable along steep slopes. In this study, we investigated how the microbial population dynamics reflected the bioavailable N dynamics with the physicochemical gradient along the slope in soils of a natural forest in Japan. We measured the gross rates of NH4+ production, nitrification, and NH4+/ NO3− immobilization using the N isotope dilution method to analyze the N dynamics in the soils. We also determined the abundance of the bacterial 16S rRNA gene and bacterial and archaeal ammonia monooxygenase gene (amoA) using qPCR to assess the populations of total bacteria and nitrifiers. We found that gross rates of NH4+ production and nitrification were higher in the lower part of the slope, they were positively correlated with the abundance of the bacterial 16S rRNA gene and archaeal amoA, respectively; and the availability of N, particularly NO3−, for plants was higher in the lower part of the slope because of the higher microbial nitrification activity and low microbial NO3− immobilization activity. In addition, path analysis indicated that gross rates of NH4+ production and nitrification were regulated mainly by the substrate (dissolved organic N and NH4+) concentrations and population sizes of total bacteria and nitrifiers, respectively, and their population sizes were strongly affected by the soil physicochemistry such as pH and water content. Our results suggested that the soil physicochemical gradient along the slope caused the spatial gradient of gross rates of NH4+ production and nitrification by altering the communities of ammonifiers and nitrifiers in the forest slope, which also affected plant distribution and growth via the supply of bioavailable N to plants.