Tower‐Based Remote Sensing Reveals Mechanisms Behind a Two‐phased Spring Transition in a Mixed‐Species Boreal Forest
Tower‐Based Remote Sensing Reveals Mechanisms Behind a Two‐phased Spring Transition in a Mixed‐Species Boreal Forest
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基于塔的遥感揭示了混合物种北方森林两阶段春季转变背后的机制
DOI：
10.1029/2020jg006191
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Bowling, David R.
中科院分区：
文献类型：
--
作者：
Pierrat, Zoe;Nehemy, Magali F.;Roy, Alexandre;Magney, Troy;Parazoo, Nicholas C.;Laroque, Colin;Pappas, Christoforos;Sonnentag, Oliver;Grossmann, Katja;Bowling, David R.
北方森林是全球气候系统的主要贡献者，因此，减少森林如何应对气候变化的不确定性至关重要。不确定性的一个来源是春季过渡的时间和驱动因素。遥感可以提供关于这种转变的重要信息，但持续的树叶绿色，季节性积雪，以及混合林（落叶和万年青物种）的高度流行，使这些信号的解释变得复杂。我们收集了基于塔的遥感数据（基于反射率的植被指数和太阳诱导叶绿素荧光[SIF]），树干半径测量，总初级生产力和环境条件在北方混合林林分。对这些数据集的评估显示了两个阶段的春季过渡。第一阶段是常绿植物光合作用和蒸腾作用的重新激活，其特征是相对SIF的增加，并由解冻的茎、温暖的空气温度和增加的土壤水分触发。第二阶段是常绿植物中大量光保护色素的减少，其标志是叶绿素-类胡萝卜素指数的增加。落叶落叶发生在这一阶段，标志着所有遥感指标的增加。第二阶段是由土壤解冻控制的。我们的研究结果表明，遥感指标可以用来检测特定的生理变化，在春季过渡的北方树种。这两个阶段的过渡解释了遥感估计春季恢复的时间和驱动因素的不一致性。我们的研究结果意味着，基于卫星的观测将通过使用植被指数和SIF的组合，随着物种分布信息沿着。
The boreal forest is a major contributor to the global climate system, therefore, reducing uncertainties in how the forest will respond to a changing climate is critical. One source of uncertainty is the timing and drivers of the spring transition. Remote sensing can provide important information on this transition, but persistent foliage greenness, seasonal snow cover, and a high prevalence of mixed forest stands (both deciduous and evergreen species) complicate interpretation of these signals. We collected tower‐based remotely sensed data (reflectance‐based vegetation indices and Solar‐Induced Chlorophyll Fluorescence [SIF]), stem radius measurements, gross primary productivity, and environmental conditions in a boreal mixed forest stand. Evaluation of this data set shows a two‐phased spring transition. The first phase is the reactivation of photosynthesis and transpiration in evergreens, marked by an increase in relative SIF, and is triggered by thawed stems, warm air temperatures, and increased available soil moisture. The second phase is a reduction in bulk photoprotective pigments in evergreens, marked by an increase in the Chlorophyll‐Carotenoid Index. Deciduous leaf‐out occurs during this phase, marked by an increase in all remotely sensed metrics. The second phase is controlled by soil thaw. Our results demonstrate that remote sensing metrics can be used to detect specific physiological changes in boreal tree species during the spring transition. The two‐phased transition explains inconsistencies in remote sensing estimates of the timing and drivers of spring recovery. Our results imply that satellite‐based observations will improve by using a combination of vegetation indices and SIF, along with species distribution information.
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DOI：
--
发表时间：
2013
期刊：
影响因子：
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作者：
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影响因子：
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Oliveira, Rafael S.
DOI：
10.1098/rstb.2010.0102
发表时间：
2010-10-12
影响因子：
6.3
作者：
Richardson, Andrew D.;Black, T. Andy;Varlagin, Andrej
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Varlagin, Andrej