Poyang Lake Eco-economy Research Center, Jiujiang University, Jiujiang, 332005, China.
State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China.
Sci Rep. 2018 Sep 28;8(1):14512. doi: 10.1038/s41598-018-32863-8.
Although straw decomposition is important for ecosystem fertility and carbon balance, influence of ultraviolet-B (UV-B) radiation and nitrogen (N) deposition on this process is unclear. In this study, UV-B-exposed rice straw was decomposed under different N addition treatments for 15 months to investigate the indirect effects of UV-B radiation on straw chemistry and direct effects of N deposition on decomposition. UV-B exposure during rice plant growth changed the rice straw chemical composition, increasing the concentrations of acid-insoluble fraction (AIF), acid-soluble fraction, and UV-B-absorbing compounds. High N content had a negative effect on decomposition of rice straw exposed to enhanced and ambient UV-B radiation. Both AIF concentration and FTIR peak intensities indicated that lignin in rice straw was selectively preserved following N addition and UV-B radiation, reducing straw decomposition rate, which corresponded to lower activities of lignin-degrading enzymes in the later stage of decomposition. Thus, enhanced UV-B radiation during rice plant growth produced more recalcitrant substrates (lignin) and N reacted with lignin to produce more resistant compounds, further decreasing straw decomposition rate. UV-B radiation during plant growth and N deposition inhibit litter decomposition in agroecosystem, and their effects should be considered when establishing biogeochemical models in response to global changes.
虽然秸秆分解对生态系统肥力和碳平衡很重要，但紫外线-B（UV-B）辐射和氮（N）沉积对这一过程的影响尚不清楚。在这项研究中，将暴露于 UV-B 下的水稻秸秆在不同的 N 添加处理下分解 15 个月，以研究 UV-B 辐射对秸秆化学性质的间接影响以及 N 沉积对分解的直接影响。在水稻生长期间暴露于 UV-B 会改变水稻秸秆的化学成分，增加酸不溶部分（AIF）、酸可溶部分和吸收 UV-B 的化合物的浓度。高 N 含量对增强和环境 UV-B 辐射下的水稻秸秆分解有负面影响。AIF 浓度和傅里叶变换红外光谱（FTIR）峰强度均表明，在 N 添加和 UV-B 辐射后，水稻秸秆中的木质素被选择性地保留，降低了秸秆分解速率，这与分解后期木质素降解酶活性较低相对应。因此，在水稻生长过程中增强的 UV-B 辐射产生了更多的难降解物质（木质素），而 N 与木质素反应生成了更多的抗性化合物，进一步降低了秸秆分解速率。植物生长过程中的 UV-B 辐射和 N 沉积抑制了农业生态系统中凋落物的分解，在建立应对全球变化的生物地球化学模型时应考虑这些因素的影响。
