蚂蚁筑巢对西双版纳热带森林土壤有机氮矿化的影响

蚂蚁作为生态系统工程师能够调节土壤微生物及理化环境，进而对热带森林土壤有机氮矿化速率及其时间动态产生显著影响。以西双版纳白背桐热带森林群落为研究对象，采用室内需氧培养法测定土壤有机氮矿化速率，比较蚁巢和非蚁巢土壤有机氮矿化速率的时间动态，揭示蚂蚁筑巢活动引起土壤无机氮库、微生物生物量碳及化学性质改变对有机氮矿化速率时间动态的影响。结果表明：（1）蚂蚁筑巢显著影响土壤有机氮矿化速率（P<0.01），相较于非蚁巢，蚁巢土壤有机氮矿化速率提高了261%；（2）土壤有机氮矿化速率随月份推移呈明显的单峰型变化趋势，即6月最大（蚁巢1.22 mg kg^-1 d^-1、非蚁巢0.41 mg kg^-1 d^-1），12月最小（蚁巢0.82 mg kg^-1 d^-1、非蚁巢0.18 mg kg^-1 d^-1）；（3）两因素方差分析表明，不同月份及不同处理对土壤有机氮矿化速率、NH₄-N及NO₃-N产生显著影响（P<0.05），但对NO₃-N的交互作用不显著；（4）蚂蚁筑巢显著提高了无机氮库（NH₄-N与NO₃-N）、微生物生物量碳、有机质、水解氮、全氮及易氧化有机碳等土壤养分含量，而降低了土壤pH值；（5）回归分析表明，铵态氮和硝态氮对土壤有机氮矿化速率产生显著影响，分别解释87.89%、61.84%的有机氮矿化速率变化；（6）主成份分析表明NH₄-N、微生物生物量碳及有机质是影响有机氮矿化速率时间动态的主要因素，而全氮、NO₃-N、易氧化有机碳、水解氮及pH对土壤有机氮矿化速率的影响次之，且pH与土壤有机氮矿化速率呈显著负相关。总之，蚂蚁筑巢活动主要通过影响土壤NH₄-N、微生物生物量碳及有机质的状况，进而调控西双版纳热带森林土壤有机氮矿化速率的时间动态。研究结果将有助于进一步提高对土壤氮矿化生物调控机制的认识。

Effect of ant colonization on soil organic nitrogen mineralization in the Xishuangbanna tropical forest

Ants often act as ecosystem engineers in mediating the soil microbial and physicochemical properties. This thus can exert a crucial effect on soil organic nitrogen mineralization and its temporal dynamics in tropical forest. The indoor-aerobic incubation method was used to determine soil organic nitrogen mineralization rates in Mallotus paniculatus community of Xishuangbanna tropical forest. This study aimed to compare temporal dynamics of soil organic nitrogen mineralization rates in ant nests and the reference soils. We also revealed the effects of the changes of soil inorganic nitrogen pool (i.e., NH₄-N and NO₃-N), microbial biomass carbon, and chemical properties on the temporal dynamics of organic nitrogen mineralization rates driven by the ant nesting activities. The results were as follows:(1) Ant colonization had a significant effect on soil nitrogen mineralization rates (P<0.01). The mean organic nitrogen mineralization rates were 261% higher in ant nests than in reference soils. (2) The monthly dynamics in soil organic nitrogen mineralization rates showed an obvious trend of single peak, which was the largest in June (ant nests:1.22 mg kg^-1 d^-1, reference soils:0.41 mg kg^-1 d^-1) and the smallest in December (ant nests:0.82 mg kg^-1 d^-1, reference soils:0.18 mg kg^-1 d^-1). (3) Two-way ANOVAs showed that the factors of month and treatment had significant effects on the concentrations of soil organic nitrogen mineralization rates, NH₄-N, and NO₃-N (P<0.05), but no significant interaction of them was observed on NO₃-N. (4) Ant colonization significantly increased the concentrations of soil inorganic nitrogen pool (NH₄-N and NO₃-N), microbial biomass carbon, organic matter, hydrolyzable nitrogen, total nitrogen, readily oxidizable organic carbon, but reduced the value of soil pH. (5) The regression analysis showed that ammonium and nitrate nitrogen had significant effects on soil organic nitrogen mineralization rates, accounting for 87.89% and 61.84% of the changes in soil organic nitrogen mineralization rates, respectively. 6) Principal component analysis indicated that ammonium nitrogen, microbial biomass carbon, and organic matter were the main factors affecting the temporal dynamics of soil nitrogen mineralization rates, followed by total and nitrate nitrogen, readily oxidizable organic carbon, hydrolyzable nitrogen, and pH. Soil pH was negatively correlated with soil nitrogen mineralization rates. In short, the ant colonization had a crucial role in regulating the temporal dynamics in soil organic nitrogen mineralization rates, through affecting ammonium nitrogen, microbial biomass carbon, and soil organic matter in the Xishuangbanna tropical forest. The results would be helpful to further improve our understanding of the biological regulation mechanism of soil nitrogen mineralization.