鼎湖山亚热带常绿针阔叶混交林凋落物及矿质氮输入对土壤有机碳分解的影响

Effects of litter and mineral nitrogen input on soil organic carbon decomposition in subtropical mixed forest in Dinghu Mountain,South China.

2010年7—12月,选取鼎湖山国家级自然保护区亚热带针阔叶混交林,采用全因子控制试验,研究不同类型的凋落物(针叶和阔叶凋落物)添加及氮处理(加氮模拟氮饱和、减氮模拟根吸收)对表层(0～10cm)和下层(20～30cm)土壤有机质分解(呼吸)的影响.结果表明:2010年7—11月间,两种凋落物的添加使土壤-凋落物系统的呼吸速率显著增加,但这种影响在12月消失.减氮和加氮处理均显著增加了土壤-凋落物系统的呼吸.叶凋落物短期内完全分解,对土壤碳分解和积累的影响十分有限,可能不是该系统中土壤有机质的主要来源.通过减少土壤可利用氮模拟根系对氮的吸收能够明显促进土壤有机质的分解.

In July-December 2010,a complete factor-controlled experiment was conducted to study the effects of litter and mineral nitrogen addition on soil organic matter decomposition（soil respiration） at the depths of 0-10 cm and 20-30 cm in Dinghu Mountain National Reserve.Coniferous needle litter and broadleaved litter were added,respectively,and 70 g N·m-2·yr-1 of NH4NO3 was applied to simulate soil nitrogen saturation whereas soil mineral nitrogen was removed by ion-exchange membrane to simulate the decreased nitrogen absorption by root.The addition of both needle litter and broadleaved litter increased the respiration rate of soil-litter system significantly from July to November,but this effect disappeared in December.Both mineral nitrogen application and soil mineral nitrogen removal increased the soil-litter respiration significantly.These results suggest that litter decomposed completely in a short period therefor had limited effects on soil organic matter decomposition and accumulation,and thus,foliar litters could be not the major source of soil organic matter,whereas soil mineral nitrogen removal could obviously promote the soil organic matter decomposition in the system.