Addition of inorganic phosphorus to soil leads to desorption of organic compounds and thus to increased soil respiration
Addition of inorganic phosphorus to soil leads to desorption of organic compounds and thus to increased soil respiration
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DOI：
10.1016/j.soilbio.2018.12.018
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发表时间：
2019-03
影响因子：
9.7
通讯作者：
M. Spohn;P. Schleuss
中科院分区：
文献类型：
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作者：
M. Spohn;P. Schleuss
在土壤中添加无机磷(P)常被报道导致土壤呼吸的增加，这被归因于减轻了微生物对P的限制。作为对这一现象的另一种解释，我们检验了一种假设，即添加无机P会增加微生物的呼吸作用，因为添加的无机P会与土壤中吸附的有机化合物进行交换，从而使这些有机化合物可供微生物分解。用~(14)C标记的一磷酸腺苷(AMP)进行了试验，测定了在有机层和A层中添加无机磷对土壤中溶解有机碳(DOC)、溶解DNA和土壤呼吸的影响。我们在含有微量14C-AMP的四个土层中添加无机磷，发现所有土层中添加磷显著增加了14C-CO2的排放，增加了1.4~4.0倍。由于无机磷的添加，所有土层的呼吸速率都显著增加了1.1到1.9倍。添加无机磷后1h，DOC浓度较对照增加1.6~3.5倍，添加无机磷后7d，DOC浓度仍高于对照。此外，可溶性DNA和胞外DNA浓度也显著增加。~(14)C实验表明，无机磷的添加增加了土壤固相中一种强烈吸附的化合物的微生物代谢，表明增加呼吸的碳的来源是死有机质，在无机磷的添加下解吸。提取实验表明，无机磷的加入导致DOC浓度升高。综上所述，我们的研究支持这一假设，即添加无机磷增加了微生物的呼吸作用，因为添加的无机磷与土壤中吸附的有机化合物进行交换，从而使这些化合物可供微生物分解。结果表明，土壤微生物呼吸作用的增加并不是因为微生物对磷的限制得到了缓解，而是解吸的有机碳缓解了微生物对碳的限制。
Addition of inorganic phosphorus (P) to soil has often been reported to cause increases in soil respiration, and this has been attributed to an alleviation of microbial P limitation. As an alternative explanation for this phenomenon, we tested the hypothesis that addition of inorganic P increases microbial respiration because added inorganic P exchanges with sorbed organic compounds in soil, and thus renders these organic compounds available for microbial decomposition. We conducted an experiment with14C-labeled adenosine-monophosphate (AMP), and we determined the effect of inorganic P addition on dissolved organic carbon (DOC), dissolved DNA and soil respiration in the organic horizon and the A horizon of two beech forest soils with contrasting P stocks. We added inorganic P to the four soil horizons that contained trace amounts of14C-AMP, and found that the emission of14C-CO2increased significantly due to P addition in all soil horizons by a factor of 1.4 to 4.0. Respiration rates increased significantly in all soil horizons by a factor 1.1 to 1.9 due to inorganic P addition. One hour after the addition of inorganic P, DOC concentrations were increased by a factor of 1.6 to 3.5 compared to the controls, and they were still similarly high seven days after the addition of inorganic P. Furthermore, concentrations of dissolved, extracellular DNA were also significantly increased in response to P addition. The14C experiment shows that the addition of inorganic P led to increased microbial metabolization of a compound that strongly sorbs to the soil solid phase and suggests that the source of the additionally respired C is dead organic matter that desorbs upon inorganic P addition. The extraction experiments show that addition of inorganic P led to elevated DOC concentrations. In conclusion, our study supports the hypothesis that the addition of inorganic P increases microbial respiration because added inorganic P exchanges with sorbed organic compounds in soil, and thus turns these compounds available for microbial decomposition. The results indicate that microbial respiration was increased in response to P addition not because microbial P limitation was alleviated but because microbial C limitation was alleviated by desorbed organic C.