近20年海南岛热带农田生态系统碳足迹时空格局演变

目的 厘清农田生态系统碳动态及其影响因素，为海南发展热带特色高效农业，推进国家生态文明试验区建设提供理论依据和数据支撑。方法 文章基于1999—2018年海南岛县域尺度的农田生产投入及作物产量等数据，构建农田生态系统碳足迹模型，利用ArcGIS 10.4、SPSS 21.0等平台，探讨海南岛农田生态系统碳足迹时空变化及其影响因素。结果 研究期间海南岛农田生态系统碳排放总量呈波动增长，年均增幅1.15%，其中，土壤呼吸占碳排放量比例最高，为52.52%；碳吸收总量呈现先上升后下降的趋势，拐点发生在2013年，作物结构调整是碳吸收总量下降主要原因；海南岛农田生态系统碳足迹总量呈波动增长趋势，年均增长率为2.94%，2016年农田系统碳平衡由生态盈余转为生态赤字。从空间上看，碳排放、碳吸收和碳足迹总量都呈四周沿海地区高，中部内陆地区低的分布格局；但单位面积碳足迹呈现东南高，西北低的空间分布规律。结论 研究期间海南岛各县市的农田系统碳足迹呈持续增长趋势，农田生态系统碳汇功能持续减弱，并在2016年由碳汇转变为碳源，调整优化农业产业结构和加强田间管理是增加农田生态系统碳汇功能的主要措施。

SPATIAL AND TEMPORAL EVOLUTION OF CARBON FOOTPRINT OF TROPICAL FARMLAND ECOSYSTEM IN HAINAN ISLAND IN RECENT 20 YEARS

Clarifying the carbon dynamics and its influencing factors of farmland ecosystem can provide theoretical basis and data support for Hainan to develop high-efficient agriculture with tropical characteristics and promote the construction of national ecological civilization experimental zone. Models for the estimation of carbon footprint of farmland ecosystem were proposed based on the data of farmland production input and crop output among counties in Hainan province from 1999 to 2018, and the spatial and temporal changes of the carbon footprint and influencing factors were discussed by means of ArcGIS 10.4 and SPSS 21.0. The results showed that during the study period, the total carbon emissions of the farmland ecosystem in Hainan island presented a fluctuant increasing trend, with an average annual increase of 1.15%, and soil respiration accounted for 52.52% of carbon emissions. The total carbon absorption first increased and then decreased with an inflection point in 2013, and the adjustment of crop structure was the main reason for the decline in carbon absorption. The total carbon footprint of farmland ecosystem in Hainan island showed an overall increasing trend with an average annual growth rate of 2.94%. In 2016, the carbon balance of farmland system changed from ecological surplus to ecological deficit. Spatially, total carbon emissions, total carbon absorption and total carbon footprint were high in the coastal areas, low in the central inland areas, with significant regional differences. However, the carbon footprint per unit area was higher in the southeast and lower in the northwest. To conclude, during the study period, the carbon footprint of farmland ecosystem showed a continuous growth trend in the counties of Hainan island. The carbon sink function of farmland ecosystem continued to weak, and the farmland ecosystem changed from carbon sinks to carbon sources in 2016. So, adjusting and optimizing the agricultural industrial structure and strengthening the field management are the main measures to increase the carbon sink function of farmland ecosystem.