海南橡胶林生态系统净碳交换物候特征

橡胶林是我国热区重要的森林生态系统,在区域碳循环中扮演着重要角色,其碳汇功能不能忽视。本研究中将海南儋州橡胶林作为研究对象,采用位于中国热带农业科学院试验农场三队的50 m微气象观测系统观测的2018—2020年数据,分析橡胶林净生态系统交换量（NEE）、生态系统呼吸（Re）和总生态系统光合生产力（GPP）的物候变化特征,并结合物候模型分析影响因子。结果表明：（1）橡胶林生态系统扮演着碳汇的角色且具有明显日变化特征,呈现“U”型,NEE白天为负值,夜间为正值,11：00—13：00达到峰值;（2）以年度为单位时,会发现明显的趋同物候变化。在橡胶的生长季（3—11月）时,Re及GPP明显大于非生长季,NEE（负值）小于非生长季,均呈现单峰,在8—9月的橡胶生长旺盛期均达到峰值;（3）橡胶林生态系统物候特征显示,在第Ⅱ期生产力上升,在第Ⅲ期达到顶峰,第Ⅳ期开始下降,第Ⅴ至翌年Ⅰ期落叶盛期生产力持续降低;（4）橡胶林生态系统生长季较长,NEE与Re均在生长季达到最大值,雨热同期导致橡胶树在第一、二蓬叶抽发时期,净生态系统碳交换增加迅速;（5）不同物候时期NEE与环境因子关系不同,海南儋州橡胶林的环境因子影响物候,物候影响NEE的变化。研究物候与生态系统碳交换的关系,同时结合环境因子综合讨论,可为后续橡胶林碳循环及对气候变化的响应研究提供理论支持,为橡胶林生态系统评价和经济社会可持续发展规划提供更多的依据和参考。

Phenological Characteristics of Net Ecosystem Carbon Exchange in Hainan Rubber Forest Ecosystem

Rubber (Hevea brasiliensis) plantation is an important forest ecosystem in the tropical region of China, plays an important role in the regional carbon cycle, and the carbon sink function cannot be ignored. In this study, we take the rubber plantation located in Danzhou, Hainan as the experiment subject, using the 50-meter micro-meteorological observation system which located in the third team of the Chinese Academy of Tropical Agricultural Sciences experimental farm. The data from 2018 to 2020 combined with the phenological model were used to analyze the dynamic characteristics of net ecosystem carbon exchange (NEE), ecosystem respiration (Re), gross primarily productivity (GPP), environmental control factors and phenological characteristics. The rubber plantation played the role of carbon sink and had obvious diurnal characteristics, showing a tendency of “U” shape. NEE was negative during the daytime and positive during the night, the maximum peak for NEE appeared at 11:00—13:00 at noon. When taking the annual as a unit, obvious convergent phenological changes would be found. During the rubber growing season (March to November), Re and GPP were significantly larger than those in the non-growing season, while NEE (negative value) is lower than the non-growing season, showing a single peak, all peaked during the rubber growth period from August to September. The phenological characteristics of the rubber plantation ecosystem showed, GPP increased during the second phase, peaked in the third phase, began to decline in the fourth phase, and continued to decrease during the deciduous period from the fifth phase to the next year first phase. The rubber plantation had a long growing season. Both NEE and Re reach the maximum during the growing season. During the period of the first and second rubber leaves, the rubber plantation net ecosystem exchange increased rapidly due to the heavy rainfall and high heat occurred at the same period. The relationship between NEE and environmental factors in different phenological periods was different. The environmental factors of rubber plantations in Danzhou, Hainan affected the phenology, and the phenology affected the changes of NEE. Study the relationship between phenology and carbon net ecosystem exchange, combined with a comprehensive discussion of environmental factors, would provided theoretical support for subsequent research on rubber plantation carbon cycle and lay a foundation for further research on response of rubber plantation to climate change, and provide more information and reference for rubber plantation ecosystem evaluation and sustainable economic and social development planning.