The Emissions of Carbon Dioxide, Methane, and Nitrous Oxide during Winter without Cultivation in Local Saline-Alkali Rice and Maize Fields in Northeast China

Hao Zhang,Shuang Liang,Ping Yang,Jie Tang,Jingjing Wang,Zhaoyang Li,Sining Wang

doi:10.3390/su9101916

Abstract

Agricultural ecosystems are important contributors to atmospheric greenhouse gasses (GHGs); however, in situ winter emission data in saline-alkali fields are scarce. Gas samples were collected during different periods, from three rice (R1–R3) and three maize (M1–M3) fields with different soil pH levels and salinity conditions. Carbon dioxide (CO2) emissions in the rice and maize fields decreased with decreasing temperature during the freezing period and increased with the rising temperature during the thawing period, with the majority of winter CO2 emissions occurring during these two periods. Peaks in methane (CH4) emissions were observed during the freezing period in the rice fields and during the snow-melting period in the rice and maize fields. CH4 emissions in the rice fields and CH4 uptake rates in the maize fields were significantly (P < 0.05) related to surface soil temperature. Nitrous oxide (N2O) emissions remained relatively low, except for during the peaks observed during the snow-melting period in both the rice and maize fields, leading to the high GHG contribution of the snow-melting period throughout the winter. Higher pH and salinity conditions consistently resulted in lower CO2, CH4, and N2O emissions, CH4 uptake, and lower global warming potential (GWP). These results can contribute to the assessment of the GWP during winter in saline-alkali regions.

Highlights

Global warming could alter the earth’s ecosystems by rising sea levels caused by glacier melting, changes in biome distribution, and food production, and an elevated minimum temperature in winter, and it influences the survival and development of humans
Increasing atmospheric CO2 concentrations account for most the greenhouse gases (GHGs) (IPCC, 2013) [1], N2O and CH4 are as important because of their unique radiative properties and long residence time in the atmosphere result in their global warming potential (GWP) being 298 and 25 times that of CO2 over a period of 100 years, respectively (IPCC, 2007) [3]
CO2 emission peaks occurred during the early thawing period in M1, M2, R1, R2, whereas R3, and M3 did not exhibit obvious CO2 emission peaks during the early thawing period, possibly because of the high salinity conditions in R3 and M3 restrained microbial activities [33], reduced microbial biomass [47], and decelerated the consumption of readily available dissolved organic matter

Summary

Introduction

Global warming could alter the earth’s ecosystems by rising sea levels caused by glacier melting, changes in biome distribution, and food production, and an elevated minimum temperature in winter, and it influences the survival and development of humans. Global temperatures have increased by 0.85 ◦C in the past 130 years, and are predicted to continue to increase by 1.2 ◦C to 4.8 ◦C by the end of the 21st century [1]. According to the 2013 Intergovernmental Panel on Climate Change (IPCC), the increased atmospheric concentration of greenhouse gases (GHGs), including carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), are responsible for past, current, and predicted future global warming by substantially increasing the greenhouse effect [1]. Increasing atmospheric CO2 concentrations account for most the GHGs (IPCC, 2013) [1], N2O and CH4 are as important because of their unique radiative properties and long residence time in the atmosphere result in their global warming potential (GWP) being 298 and 25 times that of CO2 over a period of 100 years, respectively (IPCC, 2007) [3]. Considering the emissions of these three gasses when assessing the greenhouse effect is important

Methods

Findings

Discussion

Conclusion