不同土壤水分条件下香樟凋落叶覆盖对土壤碳氮循环的影响

凋落物作为森林生态系统碳库的重要组成部分对森林土壤碳、氮循环具有重要作用.为探讨香樟凋落叶对土壤碳、氮循环的影响,室内模拟研究了10%、20%和30% 3种土壤含水量条件下香樟凋落叶覆盖森林土壤中碳、氮元素的变化.结果表明: 3种含水量条件下香樟凋落叶覆盖均显著增加了土壤CO₂排放速率和土壤溶解性有机碳(WSOC)含量,但显著降低了土壤中硝态氮含量,表明香樟凋落叶覆盖能够增强土壤呼吸强度和碳矿化,抑制土壤硝化作用;香樟凋落叶覆盖能够显著增加10%含水量土壤中铵态氮含量,但降低了20%和30%含水量土壤铵态氮含量,表明香樟凋落叶覆盖对土壤铵态氮含量的影响与土壤含水量有关.香樟凋落叶中部分单萜烯浓度在不同土壤含水量条件下分别与土壤CO₂排放速率和铵态氮含量呈显著正相关,而与土壤WSOC和硝态氮含量呈显著负相关,说明香樟凋落叶覆盖对土壤碳、氮循环的影响可能与凋落叶中的单萜烯有关.

Effects of Cinnamomum camphora leaf litter cover on soil carbon and nitrogen cycles under different water conditions

Litter, as an important carbon stock, plays a significant role in carbon and nitrogen cycle in forest soil. To examine the effects of Cinnamomum camphora leaf litter on soil carbon and nitrogen cycles, the contents of carbon and nitrogen were investigated in C. camphora leaf litter-covered forest soils with the water content of 10%, 20% and 30% under laboratory-controlled condition. The results showed that leaf litter cover significantly increased both soil CO₂ emission rates and water soluble organic carbon (WSOC) content, but decreased soil nitrate nitrogen content under the three water conditions, indicating that leaf litter cover could improve soil respiration and carbon mineralization but inhibit soil nitration. Leaf litter cover significantly enhanced the content of soil ammonium with the water content of 10%, but reduced those in soils with water content of 20% and 30%, revealing that the effects of leaf litter cover on soil ammonium nitrogen contents was dependent on soil water content. The content of some monoterpenes in leaf litter had a significantly positive correlation with soil CO₂ emission rate and ammonium content, but a prominently negative relation with soil WSOC and nitrate content, implying that the effects of leaf litter cover on soil carbon and nitrogen cycles might be attributed to monoterpenes in leaf litter.