旱作农业区土壤有效碳对N2O排放的田间影响及区域评估——以关中平原为例

The process of farmland N2O emission and potential emission of typical agricultural area have been deeply concerned in recent years. Soil carbon is an important factor in the process. The related researches are mainly focus on laboratory culture and single factor. However the quantitative and net effect of field emission study are seldom carried out. On the other hand,consider the effect of soil available carbon more in the process model is very important for an accurate assessment of regional N2O emissions. The present project will monitor N2O emissions in dry farming areas of Guanzhong Plain to study the field quantitative relationships of soil available carbon and N2O emissions. Then conduct regional simulation based on this relation. The project try to answer these questions: What is the relationship of the soil available carbon and N2O emissions under the field practical farming conditions? Whan is the extent of this influence? Will regional N2O emissions respond quantitatively? And how to evaluate its contribution to reduction control of agricultural N2O emission? This will provide new scientific evidence and research methods for rational response to climate change, and reasonable and practical measures to N2O emissions reduction.

近年来，农田N2O排放过程正受到热切关注，明确排放过程中各影响因素有助于更加可靠的评估区域排放量。土壤碳的有效性是其中的重要因子，但目前相关工作多为实验室培养和单因素影响，而对田间定量水平和排放净效应的研究开展不多。另一方面，在过程模型中更多的考虑有效性碳作用，对准确评估区域N2O排放具有重要意义。 本项目将在关中平原典型旱作农业区监测N2O排放，研究土壤有效碳与N2O排放的田间定量关系，并在此基础上进行区域模拟。项目力图回答：在田间实际耕作管理条件下，土壤有效碳与N2O排放的关系如何？能达到何种水平？对大尺度区域土壤N2O排放是否仍存在这种量级关系？如何评价其对农业N2O减排控制的贡献程度？这将为我国合理应对气候变化、制定确实可行的N2O减排措施提供新的科学依据和研究方法。

农田土壤碳、氮排放及影响因素还存在不确定性，对于区域评估的可靠性和准确性有重要意义。本项目通过模式方法对中国西北旱作农业区土壤碳和氧化亚氮进行模拟，针对土壤变化影响因素开展工作。研究表明耕作方式和气候因素对农田土壤碳、氮影响显著。西北地区农业土壤有机碳含量整体水平低下，具有较大的增长潜力，并受降水影响沿湿度变化梯度不断增加。氧化亚氮排放在西北地区呈波动式增长，排放格局总体呈现从东南向西南减少的趋势。过量的氮肥施用、明显的增温是南部地区排放增强的主要原因。减少人类干扰、保护性耕作以及灌溉效率提高在干旱、半干旱地区对于提高作物生产力、维持土壤碳氮含量有关键作用。