| 不同水分梯度下UV-B辐射对2个稻田土壤碳氮转化的影响 |
| 摘要点击 1553 全文点击 534 投稿时间：2017-04-04 修订日期：2017-05-27 |
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| 中文关键词 UV-B辐射 水分 TOC DOC 矿质态氮 |
| 英文关键词 UV-B radiation soil moisture total organic carbon (TOC) dissolved organic carbon (DOC) mineral nitrogen |
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| 中文摘要 |
| UV-B辐射对土壤碳氮转化的影响与土壤物理化学性质有关，为明确土壤水分状态对UV-B辐射的影响，以有机质含量不同的两个水稻土（有机质含量低的记为L，高的记为H）为研究材料，在室内研究了含水量为25% （W1）、50% （W2）和100% （W3）时，UV-B辐射对土壤总有机碳（TOC）、可溶性有机碳（DOC）、铵态氮（NH4+-N）、硝态氮（NO3--N）以及累积净矿化氮量的影响.结果表明：120 h后，与避光（对照，CK）相比，UV-B辐射显著降低了土壤TOC的含量（P<0.05）； UV-B辐射下，水分从低到高，L土壤的TOC分别降低了9.9%、4.5%和6.3%，H土壤降低了10.9%、5.6%和6.3%.但与对照相比，UV-B辐射却促使土壤DOC增加；且在UV-B辐射下水分为100%的处理中，土壤DOC含量高于25%和50%的处理，120 h时，L土壤的DOC分别增加了21.5% （W1）、9.4（W2）和26.3% （W3），H土壤分别降低了26.7% （W1）、14.2% （W2）和33.8% （W3）.与对照相比，UV-B辐射使NH4+-N含量有所下降；且在UV-B辐射中，NH4+-N含量的变化幅度在不同水分条件下的整体表现为W1 < W2 < W3.较对照处理，UV-B辐射促进NO3--N的累积，NO3--N变化幅度在不同水分条件下的表现为：W1 < W3 < W2. 24 h后与对照相比，UV-B辐射对土壤累积净矿化氮量有显著影响（P<0.05），且UV-B辐射下累积净矿化氮量在不同水分之间差异显著（P<0.05）.这表明光降解在土壤有机质的稳定中扮演着重要角色，UV-B辐射会加速土壤有机碳的损失，影响土壤矿质态氮的转化，且水分不同，UV-B辐射对土壤碳氮转化的影响存在一定差异. |
| 英文摘要 |
| Carbon and nitrogen in soils play an important role in the global carbon and nitrogen cycle. The enhancement of ultraviolet radiation (predominantly UV-B) resulting from the depletion of stratospheric ozone has raised significant concern. The effects of UV-B radiation on soil carbon and nitrogen transformation is connected directly to the physical and chemical properties of the soil. In order to clearly understand the effects of soil moisture on UV-B radiation, this study collected soil samples from two paddy fields with different levels of organic matter in a subtropical region of China. The response of the total organic carbon (TOC), dissolved organic carbon (DOC), ammonia nitrogen (NH4+ -N), nitrate nitrogen (NO3- -N) and cumulative net nitrogen mineralization to UV-B radiation under three different moisture gradients (W1=25%, W2=50%, and W3=100%) were monitored in laboratory for 120 h. After this period, the results were compared with a control treatment (CK) and it was found that:the TOC content had significantly decreased under UV-B radiation (p<0.05). From low to high moisture content (W1, W2 and W3), the TOC decreased by 9.9%, 4.5% and 6.3%, respectively for soil with low organic matter (L), and by 10.9%, 5.6% and 6.3%, respectively for soil with high organic matter (H), under UV-B radiation. However, UV-B radiation was found to enhance the DOC content in the soil compared with the CK. Furthermore, the DOC for soil moisture contents under 100% (W3) was higher than for other moisture contents (W1, W2). The measured DOC increased by 21.5% (W1), 9.4% (W2), and 26.3% (W3) for soil with L. In addition, the measured DOC increased by 26.7% (W1), 14.2% (W2) and 33.8% (W3) for soil with H under UV-B radiation after 120 h. Compared with control treatment (CK), UV-B radiation decreased the NH4+ -N content significantly, but there was an increased NO3- -N content. The decrease of the NH4+ -N content was largest for W3 and smallest for W1. The increase in NO3- -N content was largest for W2 and smallest for W1 for the two soil samples under UV-B radiation. UV-B radiation demonstrated an obvious effect on the cumulative net nitrogen mineralization (p<0.05) after 24 h compared with the CK and the effect of different soil moisture treatment was also significant (p<0.05). Overall, light degradation played a major role in the stabilization of soil organic matter, soil moisture, and UV-B radiation could accelerate the loss of soil organic carbon and has a major impact on the transformation of mineral nitrogen in the soil. Therefore, in agricultural production systems, completely bare surfaces should be avoided. For example, paddy rice-upland crop rotation systems could reduce the use of fallow periods. |
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