Satellite-based solar-induced fluorescence tracks seasonal and elevational patterns of photosynthesis in California’s Sierra Nevada mountains
Satellite-based solar-induced fluorescence tracks seasonal and elevational patterns of photosynthesis in California’s Sierra Nevada mountains
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DOI：
10.1088/1748-9326/ad07b4
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发表时间：
2023-10
影响因子：
6.7
通讯作者：
Lewis Kunik;D. Bowling;B. Raczka;Christian Frankenberg;P. Köhler;Rui Cheng;Kenneth R. Smith;M. Goulden;Martin Jung;John C. Lin
中科院分区：
文献类型：
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作者：
Lewis Kunik;D. Bowling;B. Raczka;Christian Frankenberg;P. Köhler;Rui Cheng;Kenneth R. Smith;M. Goulden;Martin Jung;John C. Lin
土地管理者需要强有力的碳监测系统，以评估和减轻生态系统压力对美国西部森林不断变化的影响，因为大部分地上碳储存在山区。通过总初级生产力（GPP）吸收的大气碳是生态系统功能的一个重要指标，与碳监测系统特别相关。然而，在地形复杂的偏远地区进行的地面观测有限，这对跟踪区域尺度全球初级生产力构成了重大挑战。卫星观测可以帮助弥补这些监测空白，但在山地万年青针叶生物群落中，遥感方法用于推断全球生产力的准确性仍然有限，在这些生物群落中，（a）光合作用活动在很大程度上与冠层结构和叶绿素含量无关，（B）物候和大气条件的强烈异质性难以在空间和时间上解决。使用每月太阳能诱导的叶绿素荧光（SIF）采样在104公里的对流层监测仪器（TROPOMI），我们表明，高分辨率的卫星观测的SIF遵循生态预期的季节性和海拔模式的GPP跨越3000米的海拔梯度在内华达州山脉的加州。在考虑了TROPOMI SIF中由于积雪引起的高反射辐射的影响后，SIF的季节和海拔模式与机器学习模型（FLUXCOM）和陆面模型（CLM5.0-SP）的GPP估计值相关性很好，优于其他光谱植被指数。TROPOMI SIF和GPP估计的季节性差异可能是由于水分限制和冬季光合作用活动的错误描述分别在FLUXCOM和CLM5.0，与GPP来自涡动协方差观测在南部山脉内华达州的差异。这些结果表明，卫星观测的SIF可以作为一个有用的诊断和约束，以提高对多尺度碳监测系统在山地，万年青针叶林生物群落在区域尺度上的GPP的估计。
Robust carbon monitoring systems are needed for land managers to assess and mitigate the changing effects of ecosystem stress on western United States forests, where most aboveground carbon is stored in mountainous areas. Atmospheric carbon uptake via gross primary productivity (GPP) is an important indicator of ecosystem function and is particularly relevant to carbon monitoring systems. However, limited ground-based observations in remote areas with complex topography represent a significant challenge for tracking regional-scale GPP. Satellite observations can help bridge these monitoring gaps, but the accuracy of remote sensing methods for inferring GPP is still limited in montane evergreen needleleaf biomes, where (a) photosynthetic activity is largely decoupled from canopy structure and chlorophyll content, and (b) strong heterogeneity in phenology and atmospheric conditions is difficult to resolve in space and time. Using monthly solar-induced chlorophyll fluorescence (SIF) sampled at ∼4 km from the TROPOspheric Monitoring Instrument (TROPOMI), we show that high-resolution satellite-observed SIF followed ecological expectations of seasonal and elevational patterns of GPP across a 3000 m elevation gradient in the Sierra Nevada mountains of California. After accounting for the effects of high reflected radiance in TROPOMI SIF due to snow cover, the seasonal and elevational patterns of SIF were well correlated with GPP estimates from a machine-learning model (FLUXCOM) and a land surface model (CLM5.0-SP), outperforming other spectral vegetation indices. Differences in the seasonality of TROPOMI SIF and GPP estimates were likely attributed to misrepresentation of moisture limitation and winter photosynthetic activity in FLUXCOM and CLM5.0 respectively, as indicated by discrepancies with GPP derived from eddy covariance observations in the southern Sierra Nevada. These results suggest that satellite-observed SIF can serve as a useful diagnostic and constraint to improve upon estimates of GPP toward multiscale carbon monitoring systems in montane, evergreen conifer biomes at regional scales.