磷添加对橡胶林土壤N_(2)O、CO_(2)排放及净氮转化速率的影响

Effects of Phosphorus Addition on N_(2)O,CO_(2)Emissions and Net Nitrogen Transformation Rates in Rubber Forest Soil

【目的】大量研究表明,热带地区是陆地生态系统N_(2)O排放的重要区域,同时对CO_(2)的吸收和排放具有重要影响。在高度风化的热带土壤中,磷是影响橡胶林地生态系统初级生产力的重要限制因子之一,调控包括土壤N_(2)O和CO_(2)排放在内的生态功能。本研究通过室内好氧培养试验,旨在明确外源磷输入对橡胶林土壤N_(2)O、CO_(2)排放和氮素转化速率的影响。【方法】以热带地区橡胶林土壤为研究对象,在土壤质量含水量25%、温度20℃条件下,利用Robot自动连续在线培养系统,每间隔8 h测定培养瓶内气体浓度,研究不同磷添加量对土壤N_(2)O、CO_(2)排放量和净氮转化速率的影响。【结果】与单独氮添加相比,橡胶林土壤单独磷添加后显著降低N_(2)O排放并增加土壤呼吸速率,单独磷添加对N_(2)O和CO_(2)两种温室气体排放的影响存在某种程度上的“此消彼长”效应。在相同氮添加基础上,增加磷输入并未显著增加N_(2)O的产生,而显著增加了CO_(2)产生量。磷添加显著降低土壤NH_(4)^(+)含量,而对NO_(3)^(-)含量无显著影响。橡胶林土壤N_(2)O平均产生速率与NH_(4)^(+)含量呈极显著正相关关系(P<0.01),而与NO_(3)^(-)含量无关。与对照相比,单独磷添加显著降低橡胶林土壤的净氨化速率。在氮添加基础上,磷的输入显著增加橡胶林土壤氮的固定。与单独氮添加相比,单独磷添加显著增加橡胶林土壤硝化率而对净硝化速率无影响。【结论】考虑到热带海南地区橡胶林土壤中存在普遍缺磷现象,结合本试验研究结果,表明在橡胶林中合理施用磷肥可能是实现温室气体N_(2)O减排的重要措施,而在此过程中,磷肥施用增加温室气体CO_(2)排放需要引起重视。

[Objective]Previous studies have shown that the tropical region is a crucial area for N_(2)O emissions in terrestrial ecosystems,and it has an important impact on CO_(2)absorption and emissions.In the highly weathered tropical soil,phosphorus is one of the important limiting factors affecting the primary productivity of rubber plantation ecosystem,and it also regulates the ecological functions including soil N_(2)O and CO_(2)emissions.The objective of the present study is to evaluate the effects of phosphorus addition on N_(2)O,CO_(2)emissions and net nitrogen transformation rates in rubber forest soil under aerobic incubation conditions.[Method]An aerobic incubated experiment was conducted by using a robotized continuous on-line incubation system under the conditions of 25%soil moisture at 20℃.N_(2)O and CO_(2)concentration in sample flasks were auto-monitored at an interval of 8 hours in order to analyze the effects of P addition on N_(2)O,CO_(2)emission and net nitrogen transformation rates in rubber forest soil.[Result]Compared with N addition alone,P addition alone significantly reduced N_(2)O emission and increased soil respiration rate in the rubber plantation soil.Meanwhile,P addition alone had a“trade-off”effect on the production of N_(2)O and CO_(2)to some extent.Increasing P addition rate did not significantly enhance N_(2)O production,however,CO_(2)production was significantly increased under the same rate of N addition.P-addition significantly decreased soil NH_(4)^(+) content,while it had no significant effect on NO_(3)^(-).Significant positive correlation relationships(P<0.01)were observed between soil average N_(2)O production rate and NH_(4)^(+) content,but there was no correlation relationship between the production rate and NO_(3)^(-).Compared with the CK,the addition of P could significantly reduce net ammonification rate.P input significantly increased soil nitrogen fixation on the basis of N addition.Compared with the addition of N alone treatment,the addition of P alone significantly increased the nitrification rate,but it had no effect on the net nitrification rate in the rubber plantation soil.[Conclusion]P is often regarded as the primary limiting nutrient for plant growth in the rubber plantation soil.The results of this study showed that the reasonable application of P fertilizer could reduce N_(2)O emission.Meanwhile,it should be highly concerned that P fertilizer could lead to the increasing of CO_(2)emission.