Drought legacies are short, prevail in dry conifer forests and depend on growth variability

Abstract

1. The negative impacts of drought on forest growth and productivity last for several years generating legacies, although the factors that determine why such legacies vary across sites and tree species remain unclear. 2. We used an extensive network of tree-ring width (RWI, ring-width index) records of 16 tree species from 567 forests, and high-resolution climate and normalized difference vegetation index (NDVI) datasets across Spain during the common period 1982-2008 to test the hypothesis that climate conditions and growth features modulate legacy effects of drought on forests. Legacy effects of drought were calculated as the differences between detrended-only RWI and NDVI series (i.e. after removing long-term growth trends) and pre-whitened RWI and NDVI series predicted by a model including drought intensity. Superposed Epoch Analysis (SEA) was used to estimate whether legacy effects differed from random. Finally, legacy effects were related to water balance, growth persistence and variability, and tree species identity. 3. We found a widespread occurrence of drought legacy effects on both RWI and NDVI, but they were seldom significant. According to SEA, first-year drought legacies were negative and different from random in 9% and 5% of the RWI and

Tree Species Are Differently Impacted by Cumulative Drought Stress and Present Higher Growth Synchrony in Dry Places

“…How drought-induced growth reductions translate to changes in primary productivity and vegetation activity at the ecosystem level remains unclear (Gazol et al, 2020). Interestingly, we found a positive relationship between RWIstd and NDVI, which is in accordance with previous results (Vicente-Serrano et al, 2019).…”

“…According to our results the capacity to recover from drought of gymnosperms from dry sites is faster than that of angiosperms in general (Gazol et al, 2018). However, it is also true that most studies have found longer and more lasting legacies of drought in gymnosperms than in angiosperms (e.g., Anderegg et al, 2015;Gazol et al, 2020). Recently, DeSoto et al (2020) found that those trees that die because of drought presented lower growth resilience than surviving ones.…”

“…Gymnosperms are known to have marked growth reductions (i.e., low resistance) in response to drought but in some cases, they can recover fast. Such is the case of Mediterranean pines (Gazol et al, 2020). Thus, growth resistance and recovery alone provide useful but incomplete information as many other factors can ultimately determine how tree species tolerate drought.…”

“…The response of tree species to drought can vary at the intraspecific level depending on both, regional and local factors (Orwig and Abrams, 1997;Gazol et al, 2017Gazol et al, , 2018Aragão et al, 2019;Baker et al, 2019;Crouchet et al, 2019). It is expected that tree species will be more vulnerable to drought near the rearedge (equatorward) and xeric limits of their distribution ranges (Sánchez-Salguero et al, 2017) where stronger legacy effects of drought on growth can be expected (Anderegg et al, 2015;Gazol et al, 2020). However, some studies have also reported greater sensitivity of tree growth to drought at the core and even the cold distribution margins (Muffler et al, 2020).…”

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

“…For instance, evaluation of tree-ring growth during and after extreme weather events allows us to examine the stability of forest productivity and tree growth across different spatial and temporal scales (Cavin & Jump, 2017;Gazol et al, 2018;Lloret et al, 2011;Sánchez-Salguero, Camarero, Carrer, et al, 2017;Sánchez-Salguero et al, 2018). Furthermore, impacts of drought on tree growth can last for years, resulting in the so-called 'legacy effects' (Anderegg et al, 2015;Cavin et al, 2013;Gazol et al, 2020;Kannenberg et al, 2019;Peltier et al, 2016). These legacy effects increase as drought episodes become longer and occur closer in time (Peltier & Ogle, 2019).…”