Effects of extreme drought and wet events for tree mortality: Insights from tree‐ring width and carbon isotope ratio in a Siberian larch forest

Abstract

Recent studies suggest that forest vulnerability to tree mortality has increased as a result of extreme climate events such as severe drought and heavy rain. However, little is known about the mortality processes, particularly when they are induced by heavy rain. A dendroecological analysis was conducted on living and dead trees in a Siberian larch forest using the chronologies of 30 years of radial growth and carbon isotope (Δ 13 C) discrimination. The analysis demonstrates the relationship between heavy rain and larch tree mortality. Radial growth and Δ 13 C patterns in dead trees at a wet subsite diverged from those of living trees only during the heavy rain period in 2005-2007. On the other hand, the radial growth and Δ 13 C patterns in dead trees at the dry subsite diverged from those of living trees after severe drought events in 1998 and in 2002-2003. At the wet subsite, the heavy rain was intense enough to push the larch trees past their mortality threshold, whereas previous drought conditions also contributed to tree mortality at the dry subsite. Our results demonstrated that the process of larch tree mortality differs with site-specific topographical soil moisture conditions, even when synchronous tree death occurs in a specific year of climatic extremes.

Roads Impact Tree and Shrub Productivity in Adjacent Boreal Peatlands

“…At the bog, the construction of the road caused flooded conditions on the upstream areas of the road by limiting the flow of water as the flow was perpendicular to the road orientation [3]. The tree mortality as a result of inundation due to the water flow blockage has also been observed in other boreal peatlands [30], boreal forest and boreal-tundra boundary ecosystems [49,50]. The results are consistent with these findings with flooding conditions resulting in tree mortality by which an estimated rate of 8.8 ± 1.9 kgC/m 2 in terms of aboveground tree biomass was lost after road construction in the bog.…”

Early Growth Responses of Larix kaempferi (Lamb.) Carr. Seedling to Short-Term Extreme Climate Events in Summer

“…Moreover, excessive rainfall may also decrease plant productivity under extreme rainfall due to reduced photosynthetic and stomatal conductance under waterlogged conditions [18]. However, it is unclear whether tree mortality occurs only due to an excessively wet environment [19]. The vulnerability of plants may increase when such extreme events occur simultaneously.…”

Holocene wildfire and vegetation dynamics in Central Yakutia, Siberia, reconstructed from lake-sediment proxies

“…These forests provide valuable ecosystem services both for the local communities and on continental to global scales, for example, by protecting carbon-rich permafrost from accelerated degradation (Kukavskaya et al, 2013;Herzschuh et al, 2016;Herzschuh, 2020;Holloway et al, 2020;Stuenzi et al, 2021). Next to weather extremes or insect invasions, wildfires are the most important ecological disturbance in this region (Tei et al, 2019;Kharuk et al, 2021). The current fire regime of Siberia -generally described as consisting of mostly lowintensity surface fires when compared to the boreal zone of North America (Rogers et al, 2015) -has already been observed to intensify with increasing temperatures (Ponomarev et al, 2018).…”

“…Simultaneously, a prolonged snow-free period (Bulygina et al, 2009) can increase fire probability in months that were previously not associated with the annual fire season. It has been suggested that continued global warming and its direct and indirect consequences will lead to increased tree mortality and changes in species composition (Kukavskaya et al, 2013;Shuman et al, 2017;Tei et al, 2019). Due to a complex network of environmental feedbacks, impacts of these changing fire regimes on the structure of the vast eastern Siberian larch forests are yet to be well understood, especially on longer timescales.…”