DIBAF, Tuscia University, Viterbo, Italy.
DICII, University of Rome Tor Vergata, Rome, Italy.
Glob Chang Biol. 2020 Jun;26(6):3402-3416. doi: 10.1111/gcb.15072. Epub 2020 Apr 23.
Monitoring ecosystem functions in forests is a priority in a climate change scenario, as climate-induced events may initially alter the functions more than slow-changing attributes, such as biomass. The ecosystem functional properties (EFPs) are quantities that characterize key ecosystem processes. They can be derived by point observations of gas and energy exchanges between the ecosystems and the atmosphere that are collected globally at FLUXNET flux tower sites and upscaled at ecosystem level. The properties here considered describe the ability of ecosystems to optimize the use of resources for carbon uptake. They represent functional forest information, are dependent on environmental drivers, linked to leaf traits and forest structure, and influenced by climate change effects. The ability of vegetation optical depth (VOD) to provide forest functional information is investigated using 2011-2014 satellite data collected by the Soil Moisture and Ocean Salinity mission and using the EFPs as reference dataset. Tropical forests in Africa and South America were analyzed, also according to ecological homogeneous units. VOD jointly with water deficit information explained 93% and 87% of the yearly variability in both flux upscaled maximum gross primary productivity and light use efficiency functional properties, in Africa and South America forests respectively. Maps of the retrieved properties evidenced changes in forest functional responses linked to anomalous climate-induced events during the study period. The findings indicate that VOD can support the flux upscaling process in the tropical range, affected by high uncertainty, and the detection of forest anomalous functional responses. Preliminary temporal analysis of VOD and EFP signals showed fine-grained variability in periodicity, in signal dephasing, and in the strength of the relationships. In selected drier forest types, these satellite data could also support the monitoring of functional dynamics.
监测森林生态系统功能是气候变化情景下的首要任务，因为气候诱发事件最初可能会改变功能，而不是缓慢变化的属性，如生物量。生态系统功能属性（EFPs）是描述关键生态系统过程的数量。它们可以通过在通量网络通量塔站点全球收集的生态系统与大气之间气体和能量交换的点观测来得出，并在生态系统水平上进行放大。这里考虑的属性描述了生态系统优化资源利用以吸收碳的能力。它们代表功能森林信息，依赖于环境驱动因素，与叶片特征和森林结构相关联，并受气候变化影响。利用 2011 年至 2014 年由土壤湿度和海洋盐度任务收集的卫星数据，并将 EFPs 作为参考数据集，研究植被光学深度（VOD）提供森林功能信息的能力。分析了非洲和南美洲的热带森林，也根据生态同质性单元进行了分析。VOD 与水分亏缺信息一起，分别解释了非洲和南美洲森林中通量放大的最大总初级生产力和光利用效率功能属性的年变异性的 93%和 87%。检索属性的地图表明，在研究期间与异常气候诱发事件相关的森林功能响应发生了变化。研究结果表明，VOD 可以支持受高不确定性影响的热带地区通量放大过程，并可以检测到森林异常功能响应。VOD 和 EFP 信号的初步时间分析显示出周期性、信号失相和关系强度的细粒度变化。在选定的较干燥森林类型中，这些卫星数据也可以支持功能动态的监测。
