Seasonal changes in GPP/SIF ratios and their climatic determinants across the Northern Hemisphere
Seasonal changes in GPP/SIF ratios and their climatic determinants across the Northern Hemisphere
复制标题
DOI：
10.1111/gcb.15775
复制
发表时间：
2021-06
影响因子：
11.6
通讯作者：
Anping Chen;J. Mao;D. Ricciuto;Dan Lu;J. Xiao;Xing Li;P. Thornton;A. Knapp
中科院分区：
文献类型：
--
作者：
Anping Chen;J. Mao;D. Ricciuto;Dan Lu;J. Xiao;Xing Li;P. Thornton;A. Knapp
卫星衍生的太阳诱导叶绿素荧光（SIF）已越来越多地用于估算总初级生产力（GPP）。然而，SIF和GPP之间的关系尚未明确，这阻碍了卫星观测到的SIF到GPP的转换。以前的研究通常假设 SIF 和 GPP 在每日和更长的时间尺度上呈线性关系，但缺乏对这一假设的支持。在这里，我们使用 GPP/SIF 比率来研究北半球 (NH) 上 SIF 和 GPP 之间关系的季节变化。基于多个 SIF 产品以及 MODIS 和 FLUXCOM GPP 数据，我们发现北纬地区 GPP/SIF 比率呈现强烈的季节性驼峰状模式，夏季的值高于春季或秋季。这种驼峰形的 GPP/SIF 季节性变化通过检查不同的 SIF 产品得到了证实，并且对于除常绿阔叶林之外的大多数植被类型都很明显。 GPP/SIF比值的季节幅度从北方/北极地区向旱地和热带地区减小。对于大多数新罕布什尔州来说，GPP/SIF 值最低出现在 10 月或 9 月，而 GPP/SIF 值最高则出现在 6 月和 7 月。 GPP/SIF 最显着的季节性幅度发生在中间温度和降水范围内。 GPP/SIF 与生长季前期和后期的温度呈正相关，但与生长高峰月份的温度无关。不同月份温度和 GPP/SIF 之间的这些变化关系似乎在 GPP/SIF 的季节性动态中发挥着关键作用。有几种机制可以解释我们观察到的模式，未来的研究需要涵盖广泛的气候和植被设置，以提高我们对 SIF 和 GPP 之间时空关系的理解。尽管如此，我们发现 GPP/SIF 的强烈季节性变化凸显了将这种行为纳入基于 SIF 的 GPP 估计的重要性。
Satellite‐derived sun‐induced chlorophyll fluorescence (SIF) has been increasingly used for estimating gross primary production (GPP). However, the relationship between SIF and GPP has not been well defined, impeding the translation of satellite observed SIF to GPP. Previous studies have generally assumed a linear relationship between SIF and GPP at daily and longer time scales, but support for this assumption is lacking. Here, we used the GPP/SIF ratio to investigate seasonal variations in the relationship between SIF and GPP over the Northern Hemisphere (NH). Based on multiple SIF products and MODIS and FLUXCOM GPP data, we found strong seasonal hump‐shaped patterns for the GPP/SIF ratio over northern latitudes, with higher values in the summer than in the spring or autumn. This hump‐shaped GPP/SIF seasonal variation was confirmed by examining different SIF products and was evident for most vegetation types except evergreen broadleaf forests. The seasonal amplitude of the GPP/SIF ratio decreased from the boreal/arctic region to drylands and the tropics. For most of the NH, the lowest GPP/SIF values occurred in October or September, while the maximum GPP/SIF values were evident in June and July. The most pronounced seasonal amplitude of GPP/SIF occurred in intermediate temperature and precipitation ranges. GPP/SIF was positively related to temperature in the early and late parts of the growing season, but not during the peak growing months. These shifting relationships between temperature and GPP/SIF across different months appeared to play a key role in the seasonal dynamics of GPP/SIF. Several mechanisms may explain the patterns we observed, and future research encompassing a broad range of climate and vegetation settings is needed to improve our understanding of the spatial and temporal relationships between SIF and GPP. Nonetheless, the strong seasonal variation in GPP/SIF we identified highlights the importance of incorporating this behavior into SIF‐based GPP estimations.