Topographical differences in soil N transformation using15N dilution method along a slope in a conifer plantation forest in Japan
Topographical differences in soil N transformation using15N dilution method along a slope in a conifer plantation forest in Japan
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日本针叶人工林斜坡上15N稀释法土壤氮转化的地形差异
DOI：
10.1007/bf02762758
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发表时间：
2000
影响因子：
1.5
通讯作者：
K. Koba
中科院分区：
文献类型：
--
作者：
N. Tokuchi;M. Hirobe;K. Koba
采用15n稀释法研究了针叶林坡地土壤氮的转化。虽然实验室培养的净氮矿化率没有显著差异，但净硝化率在下坡增加。15n稀释法对粗N的转化不仅在速率上有明显差异，而且在主要过程上也有明显差异。矿化氮一半被固定，另一半留在坡体上部的NH4+库中，而矿化氮全部用于固定或硝化，坡体下部的NH4+库减少。土壤氮的转化分为两组，773 m以下为一组，782 m以上为一组。硝化抑制剂孵育表明，硝化作用主要由自养生物进行，而与斜坡的位置无关。不同地点的微生物生物量和微生物C/N相似。在相同呼吸速率下，773 m以下总矿化率高于782 m以上。这表明基质质量可能是土壤氮转化的控制因素之一。斜坡下部可提取有机碳氮比与微生物碳氮比基本一致。说明在773 m以下，基质的可分解性较好。认为土壤N的转化受地形水分和养分梯度的影响，使植物的生长和分解速度不同。
Soil N transformation was investigated using15N dilution method along a slope on a conifer plantation forest. Although there was no significant difference in the net N mineralization rates by laboratory incubation, net nitrification rates increased downslope. Gross N transformation by15N dilution method showed a distinct difference not only on the rates, but also on the main process between the lower and the upper of the slope. Half of minelarized N was immobilized and the other half was left in NH4+pool at the upper part of the slope, while all of mineralized N was used for immobilization or nitrification and NH4+pool decreased at the lower of the slope. Soil N transformations were classified into two groups: one was shown below 773 m and the other was shown above 782 m. The incubation with nitrification inhibitor showed that nitrification was mainly conducted by autotrophs irrespective of the position of the slope. Microbial biomass and microbial C/N were similar among the sites. However, the gross mineralization rate was higher below 773 m than above 782 m under similar respiration rates. This suggests that the substrate quality may be one of the controlling factors for soil N transformation. Extractable organic C/N was similar to microbial C/N at the lower of the slope. It indicated that the substrate was more decomposable below 773 m. It is considered that soil N transformation is affected by topographical gradient of moisture and nutrient which makes plant growth and decomposition rate different.