黄土高原苹果园土壤N2O排放特征及其微生物驱动机制

Nitrous oxide (N2O) is an important greenhouse gas, and farmland soil is the most important source of N2O emissions to atmosphere. Apple planting area increased rapidly and usually receive high doses of nitrogen (N) fertilizer in the semiarid Loess Plateau of China, apple orchard formed a very unique ecosystem considering its water and fertilizer management and regional particularity, we suspect that it should have completely different N2O production process, N2O emission characteristics and microbial driving mechanism relative to other farmland ecosystem. Therefore, this study will select different aged apple orchard in the loess plateau as the research object by integrated using static chamber-gas chromatographic techniques, inhibitions of acetylene (C2H2) and/or oxygen (O2) combinations and DNA sequencing technology, we will quantify the N2O production process, N2O emissions characteristics and driving factors from the apple orchard ecosystem, which is for reasonable estimation of the N2O emissions amount from apple orchard ecosystem in Loess Plateau area and providing a scientific basis for regional contribution to global change; and to further clarify nitrifying and denitrifying microorganism quantity, diversity and composition structure driving N2O emissions from apple orchard ecosystem, so as to provide a scientific basis for controlling N2O emissions and regulating nitrogen transformation process in the apple orchard soil. Research results would improve scientific understanding of N2O produce mechanism from apple orchard soil and have great significance on explaining or predicting N2O emissions amount in the semiarid Loess Plateau of China.

氧化亚氮（N2O）是重要的温室气体，农田土壤是N2O的最重要排放源。黄土高原苹果种植面积逐年增加且氮肥施用量高，由于水肥管理和地域特殊性形成了非常独特的生态系统，相对于农田生态系统果园土壤极可能具有完全不同的N2O产生过程、排放特征及微生物驱动机制。基于此本研究选取渭北黄土高原不同年限果园土壤为研究对象，综合运用静态暗箱-气相色谱法、乙炔+氧气组合抑制法、DNA高通量测序技术，旨在定量研究果园生态系统N2O产生过程、排放特征和驱动因素，为合理估算黄土高原果园生态系统所排放的N2O总量及其对全球变化的区域性贡献提供数据支持；并进一步阐明影响果园生态系统N2O排放的硝化和反硝化微生物的数量、多样性和区系组成结构等微生物学关联机制，以期为调控果园土壤N2O排放和氮转化过程提供科学依据。研究结果对于明确果园土壤N2O产生机理以及解释和预测黄土高原N2O的排放量具有重要意义。

本研究选取渭北黄土高原果园土壤为研究对象，综合运用静态暗箱-气相色谱法、乙炔+氧气组合抑制法、DNA高通量测序技术，对比研究了氮肥位置、土地利用方式及新老果园对果园生态系统N2O产生过程、排放特征和驱动因素的影响。研究结果表明，苹果园土壤不同氮肥施用位置显著影响温室气体的排放，是影响其排放的重要因素，穴施（集中施肥）可显著减少综合温室效应，氮肥施用位置的选择可以作为果园减排的有效方式；不同组合乙炔+氧气抑制技术对苹果园土壤N2O产生过程具有重要影响，但是其中的高浓度氧气处理都不能明显抑制果园土壤的反硝化作用或硝化作用；与小麦相比，果园土壤N2O的单位面积排放量高，排放系数更大，农田改种苹果后会显著增加综合温室效应；随着栽植年限的增加显著提高了微生物生物多样性，同时发现较高的N2O排放峰主要发生在施入铵态氮或酰胺态氮肥后的1-2周内，即使土壤中有较高硝态氮浓度，其他时段也没有较强的排放峰，对周年总排放量贡献较小，初步推测硝化过程强氨氧化非耦联过程可能是黄土高原苹果园土壤N2O产生的主要机制。研究结果为明确果园土壤N2O产生机理及调控果园土壤N2O排放和氮转化过程提供科学依据。