Department of Geography, University of Cambridge, Downing Place, Cambridge CB2 3EN, UK; Cambridge Centre for Climate Science, Department of Geography, University of Cambridge, Cambridge CB2 3EN, UK..
Sci Total Environ. 2018 Mar 15;618:665-673. doi: 10.1016/j.scitotenv.2017.07.237. Epub 2017 Nov 24.
Land surface phenology (LSP) provides bio-indication of ongoing climate change. It uses space-borne greenness proxies to monitor plant phenology at the landscape level from the regional to global scale. However, several unconsidered methodological and observational -related limitations may lead to misinterpretation of the satellite-derived signals. For instance, changes in species composition within a pixel could result in a change in the time series of the greenness proxy, due to the distinct phenology of the plant species involved. The change in the signal would then be misinterpreted as a phenological change while it is actually related to changes in species composition within the pixel. Other limitations include the selection of the smoothing technique and the method used to extract the LSP metrics. These not only may affect the timing of the LSP metrics but also the sign of the observed LSP change. Another and much less known limitation is related to the mixed signal from multi-canopy layers. Satellites may detect changes that corresponds to the understorey layer in complex vertical vegetation systems while the 'real' contribution of this layer (in terms of ecosystem functioning and dynamics) might be small compared to the undetected overstorey layer in cases of a late overstorey development. Here, some of the LSP basics are reviewed with emphasis on these (and other) potential sources of misinterpretation. Several aids to overcome these limitations, which include suggestions for multi methods analysis and the integration of information from satellite and ground-based sensors are provided alongside some prospective future LSP research directions.
陆地表面物候学（LSP）为正在发生的气候变化提供了生物指示。它利用天基绿色度代理，从区域到全球尺度监测景观水平的植物物候。然而，一些未被考虑的方法学和观测相关的限制因素可能导致对卫星衍生信号的误解。例如，由于所涉及植物物种的物候明显不同，一个像素内的物种组成的变化可能导致绿色度代理的时间序列发生变化。然后，信号的变化将被误解为物候变化，而实际上它与像素内的物种组成变化有关。其他限制因素包括平滑技术的选择和提取 LSP 指标的方法。这些不仅可能影响 LSP 指标的时间，还可能影响观察到的 LSP 变化的符号。另一个鲜为人知的限制因素与多冠层层的混合信号有关。卫星可能会检测到对应于复杂垂直植被系统下层植被的变化，而在某些情况下，由于上层植被发育较晚，这个下层植被（就生态系统功能和动态而言）的实际贡献可能相对较小，而未被检测到的上层植被则会被忽略。本文重点介绍了这些（和其他）潜在的误解来源，回顾了一些 LSP 基础知识。提供了一些克服这些限制的辅助方法，包括对多方法分析的建议以及卫星和地面传感器信息的集成，同时还提出了一些未来 LSP 研究方向。
