Impacts of recurrent dry and wet years alter long‐term tree growth trajectories

Abstract

Climate extremes, such as abnormally dry and wet conditions, generate abrupt shifts in tree growth, a situation which is expected to increase under predicted climate conditions. Thus, it is crucial to understand factors determining short‐ and long‐term tree performance in response to higher frequency and intensity of climate extremes. We evaluated how three successive droughts and wet years influenced short‐ and long‐term growth of six dominant Iberian tree species. Within species variation in growth response to repeated dry and wet years was evaluated as a function of individual traits related to resource and water use (diameter at breast height [DBH], wood density [WD] and specific leaf area [SLA]) and tree‐to‐tree competition across climatically contrasted populations. Furthermore, we assessed how short‐term accumulated impacts of the repeated dry and wet years influenced long‐term growth performance. All species showed strong short‐term growth decreases and enhancements due to repeated dry and wet years. However, patterns of accumulated growth decreases (AcGD) and enhancements (AcGE) across climatically contrasting populations were species‐specific. Furthermore, individual trait data were weakly associated with either AcGD or AcGE and the few relevant associations were found for conifers. Intraspecific variations in tree growth responses to repeated climates extremes were large, and not explained by intraspecific variability in SLA and WD. Accumulated impacts of repeated dry and wet years were related to long‐term growth trends, showing how the recurrence of climate extremes can determine growth trajectories. The relationships of AcGD and AcGE with long‐term growth trends were more common in conifers species. Synthesis. Repeated climate extremes do not only cause short‐term growth reductions and enhancements but also determine long‐term tree growth trajectories. This result shows how repeated droughts can lead to growth decline. Conifers were more susceptible to the accumulated effects of extreme weather events indicating that in the future, more intense and frequent climate extremes will alter growth performance in forests dominated by these species.

Wood density and hydraulic traits influence species’ growth response to drought across biomes

“…Although we avoid the use of drought events overlapping in pre‐ and post‐drought recovery periods (i.e. 4 years) the impacts of drought on growth can last for longer periods and affect long‐term growth trends (Serra‐Maluquer et al, 2021). Overall, this result indicates that all these circumstances, relating to different conditions across drought episodes, contribute to the complexity of observed forest response to drought, making future projections of forest response to climate change at fine scales a great challenge.…”

“…Drought stress limits the radial growth of trees across their lifespan and extreme drought episodes result in growth reductions that can last several years (Anderegg et al, 2015; Gazol et al, 2020; Peltier et al, 2016; Serra‐Maluquer et al, 2021). Drought has become a greater growth constraint during the past century (Babst et al, 2019) and more frequent and intense droughts expected from human‐caused climate change are likely to exacerbate these impacts and lead to additional growth decreases.…”

“…Recently, Li et al (2020) evaluated how much of the spatial variability of tree ring growth responses to drought was explained by several functional traits and found that some traits were related to spatial differences in growth response to drought, although methodological issues may preclude broad conclusions (Zheng et al, 2021). Functional traits and growth responses to drought vary across environmental gradients (Babst et al, 2013; Gazol et al, 2017; Wright et al, 2004), and it is unclear how long‐term growth climate relationships affect short‐term growth responses to drought at global scales (but see Huang et al, 2018; Serra‐Maluquer et al, 2021). Increasing our knowledge about the direction of these relationships, and the possible effects of climatic variables on these relationships is important for disentangling geographic covariations from possible causal relationships.…”

Growth plasticity of Gymnosperm trees did not avoid declining resilience to soil and atmospheric droughts during the 20th century

“…This plasticity may result in adjustments to the gradually changing environmental conditions, such that impacts of subsequent severe droughts on growth may either increase or decrease. Overall, the relative balance of these positive and negative effects caused by antecedent events and their legacies is central in understanding the long-term impacts of extreme climatic events, and especially drought, on tree responses [17][18][19] .…”

Shifting Precipitation Patterns Drive Growth Variability and Drought Resilience of European Atlas Cedar Plantations

“…Climate models forecast harsher conditions for many conifer forests due to a higher recurrence of extreme climatic events such as droughts, which will negatively impact their productivity, reducing tree growth and constraining growth resilience [1,2]. If droughts become more severe and frequent, recurrent stressing conditions may also reduce their long-term growth recovery [3], worsening forest health and rising mortality rates [4,5]. A reduced post-drought growth recovery leads to a declining resilience due to drought legacies or carryover effects, which challenge the ability of forests to act as effective carbon sinks, limiting their potential to mitigate climate warming [6,7].…”