南方红壤丘陵区不同土地利用方式土壤N₂O排放系数研究

王芝麟 邹彬 张涵 郭季璞 韩林蓉 王逗 李玲玲 秦红灵 郭家骅

摘要：【目的】明确不同土地利用方式土壤氧化亚氮（N2O）排放系数的差异并评估区域N2O排放，为评估南方红壤丘陵区N2O排放清单提供基础数据和参考依据。【方法】选择南方红壤丘陵区4种常见的土地利用方式（油茶林、旱地农田、稻田和松林），通过分析土壤不施肥与施氮肥时N2O排放速率和排放量的差异，计算排放系数，并用15N同位素标记方法探究硝化作用和反硝化作用对土壤排放N2O的相对贡献。【结果】不同土地利用方式土壤理化性质差异明显，稻田全氮含量最高（2.22 g/kg），显著高于其他3种土地利用方式土壤（P<0.05，下同）。土壤不施肥时，N2O排放速率在0～227.80 μg/（kg?h），施氮量为200 kg N/ha时，N2O排放速率在0～4213.27 μg/（kg?h）。4种土地利用方式的土壤N2O排放系数均随土壤孔隙含水量（WPFS）增加而增加，WPFS为75%时，稻田、旱地农田、油茶林和松林土壤N2O排放系数分别为2.47%、0.39%、2.31%和0.91%。4种土地利用方式土壤N2O排放系数主要受全氮含量影响，N2O累积排放量均与潜在反硝化潜势呈显著正相关，除稻田外，其他3种土地利用方式土壤N2O累积排放量也与潜在硝化势呈显著正相关，以NO3?-N为底物的反硝化作用对N2O排放的相对贡献平均大于90.00%，远高于硝化作用。【结论】南方红壤丘陵区土壤以NO3?-N为底物的反硝化作用主导N2O排放，施用氨基氮肥可能有效减少氮肥N2O排放损失，为国家执行碳中和政策提供理论依据。

关键词： 氧化亚氮（N2O）;排放系数;硝化和反硝化;土地利用方式;红壤

中图分类号： S154.1                           文献标志码： A 文章编号：2095-1191（2021）08-2193-09

Differences in soil N2O emission coefficients of different land use types in red soil hilly areas in southern China

WANG Zhi-lin1， ZOU Bin1， ZHANG Han1， GUO Ji-pu2， HAN Lin-rong3， WANG Dou4，5，

LI Ling-ling5， Qin Hong-ling4*， GUO Jia-hua3

（1State Gird Shaanxi Electric Power Company， Xian 710048， China;2 State Gird Shaanxi Electric Power Research Institute， Xian  710100， China; 3College of Urban and Environmental Sciences， Northwest University/Shaanxi Key Laboratory of Earth Surface System and Environmental Carrying Capacity， Xian  710127， China; 4Institute of Subtropical Agriculture， Chinese Academy of Sciences/Key Laboratory of Agro-ecological Processes in

Subtropical Region， Changsha  410125， China; 5Agronomy College， Gansu Agriculture University/

Gansu Provincial Key Laboratory of Arid Land Crop Science， Lanzhou  730070， China）

Abstract：【Objective】To clarify the differences in soil N2O emission coefficients of different land use methods and assess regional N2O emissions，to provide basic data and basis for evaluating the N2O emission inventory of red soil hilly areas in southern China. 【Method】This paper selected four common land use methods （Camellia oleifera forest，dry farmland，rice field and pine forest） in the red soil hilly region of southern China，and calculated the emission coefficient by ana-lyzing the difference in the N2O emission rate and amount when the soil was not fertilized and when nitrogen was applied，and 15N isotope was used. The labeling method explored the relative contribution of nitrification and denitrification to soil N2O emissions. 【Result】There weregreat differences in soil physical and chemical properties among different land use methods，and the total nitrogen content of paddy fields was the highest（2.22 g/kg），which was significantly higher than others（P<0.05，the same below）. When the soil was not fertilized，the N2O emission rate was 0-227.80 μg/（kg?h），and when the nitrogen application rate was 200 kg?N/ha，the N2O emission rate was 0-4213.27 μg/（kg?h）. The soil N2O emission coefficients of the four land use methods all increased with the increase of water content of soil porosity（WPFS）. When the WPFS was 75%，the soil N2O emission coefficients of paddy field，dry farmland，C. oleifera forest and pine forest were 2.47%，0.39%，2.31%，0.91%，respectively. The N2O emission coefficients of the four land use methods were mainly affected by total nitrogen content，and accumulated N2O emissions were significantly positively related with potential denitrification potential， except paddy fields， N2O cumulative emission of the other three land use methods was signi-ficantly positively related with potential nitrification potential. The relative contribution of denitrification with NO3?-N as the substrate to N2O emissions was more than 90% on average，which was much higher than nitrification. 【Conclusion】In red soil hilly areas in southern China，the denitrification with NO3?-N as the substrate dominates N2O emission. The application of amino nitrogen fertilizer may effectively reduce the loss of nitrogen fertilizer N2O emission and provide technical support for the national implementation of carbon neutral policy.

Key words： nitrous oxide（N2O）; emission factor; nitrification and denitrification; land use type; red soil

Foundation item： National Natural Science Foundation of China（41771335）; General Project of Hunan Natural Science Foundation （2020JJ4654）

0 引言

【研究意義】氧化亚氮（N2O）是一种具有温室效应的气体（张玉铭等，2011），在大气中的存留时间能长达120年左右，并可直接参与某些大气中的光化学反应，使臭氧层遭到破坏。虽然大气中的N2O含量很低，但100年时间尺度N2O单分子增温潜势为二氧化碳的265倍[Intergovernmental Panelon Climate Change（IPCC），2014]，是继二氧化碳和甲烷之后的第三大温室气体。N2O排放系数是编制N2O排放清单的重要依据，硝化或反硝化过程对N2O排放的贡献率是利用模型估算区域N2O排放的重要参数（韦良焕等，2019）。不同土地利用方式导致土壤温度、湿度、有机碳及养分含量等土壤环境因子的改变，进而改变土壤N2O的排放，IPCC方法指南中特别强调各国在编制N2O排放清单时要尽可能采用当地的排放系数（石洪艾等，2013）。……