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Wetlands play an essential role in the global greenhouse gas budget via carbon dioxide sequestration as well as methane emission. In recent decades, solar‐induced chlorophyll fluorescence (SIF) has been recognized as a remotely sensed proxy of gross primary productivity (GPP), which generates substrates for methane production. To examine the suitability of SIF for estimation of these two fluxes, we conducted ground tower‐based SIF observation with an ultrafine‐resolution spectroradiometer in conjunction with eddy covariance measurement in a cool‐temperate bog. The daily SIF retrieved in the red (687 nm) and far‐red (760 nm) bands (SIFred and SIFfar‐red, respectively) increased nonlinearly with GPP and linearly with absorbed photosynthetically active radiation (APAR). The relatively weak correlation between apparent SIF yield (ΦSIF = SIF/APAR) and light use efficiency implied that both APAR and plant physiology constrained the SIF emission in this wetland. The SIFred/SIFfar‐red ratio showed a significant negative relationship with vegetation greenness indices, and the similar seasonal variation in SIFred and SIFfar‐red indicated that the SIFred reabsorption effect only weakly influenced the SIFred–GPP relationship. Episodic temporal reduction in the water table did not distinctly influence SIF and ΦSIF. Estimation of the methane emission rate was subtly improved by incorporating SIF, which was substituted for GPP as the methanogenesis substrate, in a multivariable regression analysis together with two environmental factors: soil temperature and water table depth. This study illustrates the potential of both SIFred and SIFfar‐red to monitor GPP and to predict methane emission in wetlands. Plain Language Summary: Wetlands play a crucial role in the carbon cycle on Earth, involving both storing carbon and releasing methane. A small energy emission from plants, known as solar‐induced chlorophyll fluorescence (SIF), is a recent discovery that serves as a signal for plant productivity. It's a useful tool for tracking plant productivity. This study was conducted in a cool‐temperate bog, and we found that daily SIF measurements increased differently with plant growth and sunlight absorption. This suggests that both sunlight and plant health affect SIF in wetlands. The study also showed that SIF measurements could be useful for monitoring plant growth and predicting methane emissions in wetlands. To make these predictions better, we combined SIF with information about the environment, like soil temperature and water depth. Overall, this research highlights the potential of using SIF measurements to keep an eye on plant growth and predict methane emissions in wetlands. Key Points: Chlorophyll fluorescence in the 687 and 760 nm bands (SIFred and SIFfar‐red) has promise as a photosynthesis proxy in temperate bogsThe simple canopy structure of the wetland plant community contributed to a weak reabsorption effect of SIFredMethane prediction improved subtly with incorporation of solar‐induced chlorophyll fluorescence and environmental factors in a multivariable regression model [ABSTRACT FROM AUTHOR]

The taiga ecosystem in northeastern Siberia, a nitrogen-limited ecosystem on permafrost with a dry climate, changed during the extreme wet event in 2007. We investigated the normalized difference vegetation index (NDVI) as a satellite-derived proxy for needle production and compared it with ecosystem parameters such as soil moisture water equivalent (SWE), larch foliar C/N ratio, δ13 C and δ15 N, and ring width index (RWI) at the Spasskaya Pad Experimental Forest Station in Russia for the period from 1999 to 2019. Historical variations in NDVI showed a large difference between typical larch forest (unaffected) and the sites affected by the extreme wet event in 2007 because of high tree mortality at affected sites under extremely high SWE and waterlogging, resulting in a decrease in NDVI, although there was no difference in the NDVI between typical larch forest and affected sites before the wet event. Before 2007, the NDVI in a typical larch forest showed a positive correlation with SWE and a negative correlation with foliar C/N. These results indicate that not only the water availability (high SWE) in the previous summer and current June but also the soil N availability likely increased needle production. NDVI was also positively correlated with RWI, resulting from similar factors controlling them. However, after the wet event, NDVI was negatively correlated with SWE, while NDVI showed a negative correlation with foliar C/N. These results indicate that after the wet event, high soil moisture availability decreased needle production, which may have resulted from lower N availability. Foliar δ15 N was positively correlated with NDVI before 2007, but foliar δ15 N decreased after the wet event. This result suggests damage to roots and/or changes in soil N dynamics due to extremely high soil moisture. As a dry forest ecosystem, taiga in northeastern Siberia is affected not only by temperature-induced drought but also by high soil moisture (led by extreme wet events) and nitrogen dynamics. [ABSTRACT FROM AUTHOR]

Flooding is one of the greatest disasters that produces strong effects on the ecosystem and livelihoods of the local population. Flood frequency is expected to increase globally making its risk assessment an urgent issue. In spring‐summer 2017, an extreme flooding occurred in the Indigirka River lowland of Northeastern Siberia that inundated a large area. In this study, the extent and climatic drivers of the flooding were determined using the results of field observations, satellite images, and climate reanalysis dataset, and its possible effects on the ecosystem were discussed. In 2017, a significant lowland area of around 16,016 km2 was covered with water even in July, which was 5,217 km2 (around 4% of the total area) greater than the water‐covered area in 2015 when usual hydrological condition in the area was observed. The hydrographic signature obtained for the Indigirka River water level in 2017 was unusual. Although the water level rose sharply at the end of May (which was typical for the Arctic region), it did not fall afterwards and even increased again to an annual daily maximum value in the middle of July. The climate reanalysis dataset obtained for the temporal–spatial variations of snow water equivalent, snowmelt, and runoff over the lowland revealed that a large amount of snowmelt runoff in June and July 2017 produced a large water‐covered area and unusually high river water levels that lasted until summer. Snow depth from winter to spring was largest in 2017 over the period from 2009 to 2017, and the surface of the lower reach of the lowland was partially covered with snow even in the end of June due to the extreme snowfall that occurred in October 2016. Such unusual hydrological conditions waterlogged most trees over the lowland, which caused serious ecosystem devastation and changes in the material cycle. [ABSTRACT FROM AUTHOR]

Although stable carbon isotopic composition (δ 13 C) of plants has been widely used to indicate different water regimes in terrestrial ecosystems over the past four decades, the changes in the plant δ 13 C value under waterlogging have not been sufficiently clarified. With the enhanced global warming in recent years, the increasing frequency and severity of river floods in Arctic regions lead to more waterlogging on willows that are widely distributed in river lowland. To investigate the δ 13 C changes in plants under different water conditions (including waterlogging), we measured the δ 13 C values in the leaves of willows with three species, Salix boganidensis , S. glauca , and S. pulchra , and also monitored changes in plant physiology, under several major flooding conditions in Northeastern Siberia. The foliar δ 13 C values of willows varied, ranging from -31.6 to -25.7‰ under the different hydrological status, which can be explained by: (i) under normal conditions, the foliar δ 13 C values decrease from dry (far from a river) to wet (along a river bank) areas; (ii) the δ 13 C values increase in frequently waterlogged areas owing to stomatal closure; and (iii) after prolonged flooding periods, the δ 13 C values again decrease, probably owing to the effects of not only the closure of stomata but also the reduction of foliar photosynthetic ability under long period of waterlogging. Based on these results, we predict that plant δ 13 C values are strongly influenced by plant physiological responses to diverse hydrological conditions, particularly the long periods of flooding, as occurs in Arctic regions., Competing Interests: The authors declare that they have no competing interests.