Background and aim

Global nitrogen (N) deposition has been proposed to enhance phosphorus (P) limitation in various terrestrial ecosystems. The impact of N addition on soil P transformation, considering both microbial and abiotic properties, is not well understood.

Methods

In this study, the experiment with three levels of N addition (0 (N0, no fertilizer), 25 (N25) and 50 kg N ha⁻¹ yr⁻¹ (N50)) was implemented in a temperate broad-leaved forest to assess the long-term (12 years) effects of N addition on soil P fractions associated with soil properties, iron, aluminum, calcium, phospholipid fatty acids (PLFAs), and enzyme activities.

Results

The results indicated a significant decrease in labile P, despite of a significant increase of approximately 54.0% in available P under N addition (N50). In contrast, the moderately labile P significantly increased under N addition treatment because of the increase in organic P in less labile fractions. The redundancy analysis and mantel-test found soil pH and MBP contributed to the variation of soil P fractions. The results of structural equation model confirmed that the microbial biomass P play a key role in the transformation of soil available P into moderately and occluded P fractions.

Conclusion

These results suggested that the long-term addition of N decreased soil labile P and increased moderate and occluded P fractions through increasing microbial P use efficiency with increased MBP, leading to the enhancement of soil P limitation in the broad-leaved temperate forest.

中文翻译：

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氮添加通过增加温带森林微生物生物量磷促进土壤有机磷积累

 背景和目的

有人提出全球氮 （N） 沉积以增强各种陆地生态系统中磷 （P） 的限制。考虑到微生物和非生物特性，氮添加对土壤 P 转化的影响尚不清楚。

 方法

在本研究中，在温带阔叶林中实施了三个水平氮添加量（0（N0，无肥料）、25 （N25） 和 50 kg N ^{ha-1 yr-1} （N50））的实验，以评估氮添加对与土壤性质相关的土壤 P 组分的长期（12 年）影响、铁、铝、钙、磷脂脂肪酸 （PLFAs）、 和酶活性。

 结果

结果表明，尽管在氮添加 （N50） 下有效 P 显著增加约 54.0%，但不稳定 P 显著降低。相比之下，由于不太不稳定的馏分中有机 P 的增加，因此在 N 添加处理下中度不稳定的 P 显著增加。冗余分析和 mantel-test 发现土壤 pH 和 MBP 对土壤 P 组分的变化有贡献。结构方程模型的结果证实，微生物生物量 P 在土壤速效 P 转化为中等和封闭的 P 组分中起关键作用。

 结论

这些结果表明，长期添加 N 通过提高微生物 P 利用效率和增加 MBP 来降低土壤不稳定 P，增加中等和封闭的 P 组分，导致阔叶温带森林土壤 P 限制的增强。