氮沉降与生物炭对土壤可溶性有机质的影响

利用盆栽实验，探讨氮沉降与生物炭（BC）施用对杉木幼苗土壤可溶性有机碳（DOC）含量和可溶性有机质（DOM）光谱学特征的短期影响.氮沉降处理为0（对照）、40（低氮）和80kgN/（hm²·a）（高氮），在不同氮沉降下BC施用水平分别为0（对照）、12（低量BC）和36t/hm²（高量BC）.结果表明：相比对照处理，单独低氮与单独高氮处理3个月后土壤pH值分别下降了0.06和0.09（P<0.05），但单独施用BC和氮沉降背景下施用BC处理的土壤pH值均呈上升趋势，增加了0.32~0.94（P<0.05）.与对照处理相比，单独低氮处理的土壤DOC含量显著降低，单独高氮处理的则显著升高且DOM结构趋于简单；单独施用BC和氮沉降背景下施用BC处理中，低量BC处理的土壤DOC含量无明显变化，但高量BC处理的显著提高了30.1%~95.6%，并且DOM结构趋于复杂.冗余分析发现，土壤pH值是导致不同处理DOM存在差异的关键因素.因此，氮沉降背景下施用高量BC短期内可以减缓土壤酸化，提高土壤DOC含量并使DOM更加稳定.

Effects of nitrogen deposition and biochar application on soil dissolved organic matter

A serious of pot experiments were conducted to investigate the effects of biochar (BC) application on the contents of soil dissolved organic carbon (DOC) and spectral properties of soil dissolved organic matter (DOM) of Cunninghamia lanceolata seedling under various nitrogen (N) deposition condition. Simulated N deposition treatments were performed with 0 (control), 40 (lower N deposition) and 80kgN/(hm²·a) (higher N deposition), and biochar application rates were 0 (control), 12 (lower BC application) and 36t/hm² (higher BC application) under each N treatment. The soil pH was significantly decreased by 0.06 to 0.09unit (P<0.05) after 3months in the treatments of lower and higher N deposition alone compared with the control, respectively, but it was significantly increased by 0.32 to 0.94unit (P<0.05) in the treatments of BC application alone or BC application combined with N deposition. Compared with the control, the DOC content was decreased significantly in the treatment of lower N deposition alone, while it was significantly increased in the treatment of higher N deposition alone, and the DOM structure became simpler. The soil DOC content did not significantly change in the treatments of lower BC application alone or lower BC application combined with N deposition, but it was significantly increased from 30.1% to 95.6% in the treatments of higher BC application alone or higher BC application combined with N deposition, and the structure of DOM tended to be more complex. Redundancy analysis showed that the pH was the most important factor in controlling the properties of soil DOM among different treatments. These results implied that the higher application of BC could alleviate soil acidification in the short period, increase soil DOC content, and make DOM more stable under N deposition conditions.