Abstract:

Farmland is an important source of greenhouse gas emissions and a significant carbon sink for terrestrial ecosystems. A comprehensive understanding of the carbon pool potential of the Fenwei Plain (an important grain production base in China) and the carbon emission characteristics of agricultural activities in the Fenwei Plain can provide basic information for the industrial structure adjustment and regional sustainable development of the Fenwei Plain. In this work, by collecting the agricultural input factors and crop yield data of the farmland ecosystem of the Fenwei Plain from 2011 to 2020, the temporal and spatial changes and influencing factors of carbon source/sink and carbon footprint of the farmland ecosystem in the Fenwei Plain were analyzed, and the carbon ecological surplus/deficit of the farmland ecosystem in the Fenwei Plain was calculated. From 2011 to 2020, the total carbon emissions from the farmland ecosystem in the Fenwei Plain first increased from 3.78×10⁶ t to 4.16×10⁶ t and then decreased to 3.72×10⁶ t, and the carbon emissions per unit sown area showed an upward trend, reaching the maximum of 0.880 t·hm^-2, both showing a distribution pattern of higher in the west than the east and higher at the center than on the edge. The use of chemical fertilizer was the main factor that influenced carbon emissions, with the average annual total carbon emission contribution ratio reaching 58.8%, and its carbon emissions were generally consistent with the changing trend of total carbon emissions. The total carbon sequestration of the farmland ecosystem in the Fenwei Plain first increased from 2.48×10⁷ t to 2.69×10⁷ t and then decreased to 2.38×10⁷ t, and the spatial distribution was relatively balanced, while the carbon sequestration per unit sown area showed an upward trend with time, up to 5.98 t·hm^-2, and the distribution pattern gradually evolved to an opposite pattern where the west side became higher than the east. Food crops were the main contributors to carbon sequestration, and their carbon sequestration accounted for 92.7% of the farmland total carbon sequestration. The carbon footprint of the farmland ecosystem in the Fenwei Plain first increased from 5.94×10⁵ hm² to 6.44×10⁵ hm² and then decreased to 5.54×10⁵ hm², and the spatial distribution was irregular, while the carbon footprint per unit area showed an upward trend, generally showing a distribution pattern of high in the west and low in the east. Overall, the farmland ecosystem in the Fenwei Plain has a carbon ecological surplus, but in recent years the surplus has also shown a certain downward trend, and there is a risk of weakening the carbon reservoir function of the farmland ecosystem. The agricultural development in different cities is relatively uneven, and thus attention should be given to the green development of the primary industry for maintaining the scale of farmland carbon sink and achieving regional carbon peaking.

Key words: carbon footprint, Fenwei Plain, farmland ecosystem, carbon sequestration, carbon emission

摘要：

农田是重要的温室气体排放源，同时也是陆地生态系统的重要碳汇。充分认识我国重要粮食生产基地——汾渭平原的碳库潜力，深入了解汾渭平原农业活动的碳排放特征，可为汾渭平原产业结构调整和区域可持续发展提供基础信息。通过收集2011—2020年汾渭平原农田生态系统农业投入要素及作物产量数据，解析了汾渭平原农田生态系统的碳源/碳汇及碳足迹时空变化及影响因素，核算了汾渭平原农田生态系统的碳生态盈余/赤字。2011—2020年，汾渭平原碳排放总量从3.78×10⁶ t先升高至4.16×10⁶ t后逐步下降到3.72×10⁶ t，单位播种面积碳排放呈上升趋势，最高达0.880 t·hm^-2，两者均呈现西部高于东部、中心高于边缘的分布格局，而化肥使用是碳排放的主要因素（碳排放总量年均贡献率达58.8%），其所贡献的碳排放量与总碳排放量的变化趋势大体一致。汾渭平原碳吸收总量从2.48×10⁷ t先升高到2.69×10⁷ t后下降至2.38×10⁷ t，空间分布较为均衡，而单位播种面积碳吸收随时间呈上升趋势，最高达5.98 t·hm^-2，且逐步由东部高于西部演变为西部高于东部，其中粮食作物是碳吸收的主要贡献源，其碳吸收量占农田总吸收量的92.7%。汾渭平原碳足迹从5.94×10⁵ hm²先升高至6.44×10⁵ hm²后下降至5.54×10⁵ hm²，空间分布不规律，而单位面积碳足迹呈上升趋势，大体呈现西部高、东部低的分布格局。汾渭平原农田整体呈碳生态盈余状况，然而近年也出现了盈余下降趋势，其农田生态系统碳库功能有削弱风险。各城市间农业发展不均衡较为明显。重视第一产业的绿色发展对保持农田碳汇规模、实现区域碳达峰具有重要意义。

关键词: 碳足迹, 汾渭平原, 农田生态系统, 碳吸收, 碳排放