Impacts of droughts on the growth resilience of Northern Hemisphere forests

Abstract

Aim The intensity and frequency of drought have increased considerably during recent decades in some Northern Hemisphere forested areas, and future climate warming could further magnify drought stress. We quantify how forests resist drought events and recover after them, i.e. we determine their growth resilience. Location North America and Europe. Methods We use a large tree‐ring database to study how drought influences forest growth resilience. We selected 775 tree‐ring width chronologies and studied the occurrence of years with extremely dry conditions (low soil moisture and/or high evaporative stress; hereafter ‘drought’) in these forests. For each drought in each forest we calculated three indices that represent different components of growth resilience to drought: resistance (Rt), recovery (Rc) and resilience (Rs). We related the variation in these indices with geographical, topographic, climatic and ecological conditions from each region. Results The three components of forest growth resilience were interrelated. Resistance and recovery were negatively related, and both were positively and nonlinearly related to resilience. Drought resistance increased with latitude, soil moisture and slope, whereas drought recovery decreased with latitude, soil moisture and summer normalized difference vegetation index. Drought resilience increased with elevation and decreased with the variation in soil moisture. Temperate broadleaf forests from wet regions showed a greater growth resistance (e.g. north‐eastern USA, central Europe) while conifer forests from dry to semi‐arid regions (e.g. south‐western USA, southern Europe) presented a greater growth recovery. Main conclusions The geographical patterns of growth resilience indices confirm the existence of different strategies among forests to cope with droughts, depending on the biome, the tree species and the prevailing climatic conditions. Geographical patterns in soil moisture availability tend to override species‐specific responses to drought.

Detecting the fingerprint of drought across Europe’s forests: do carbon isotope ratios and stem growth rates tell similar stories?

“…Instead, legacy effects of drought varied considerably among species, and with few exceptions seemed to reflect slow, progressive recovery from drought rather than a lagged response sensu stricto (which would manifest as little or no change in growth during the drought year, followed by a more pronounced decline in the following year). Overall, this recovery appears to have been faster for conifers than angiosperms, which is consistent with the results of a recent large scale study on forest resilience to drought across the Northern hemisphere (Gazol et al 2017). Norway spruce for instance showed signs of recovery at three of the four sites where it was sampled.…”

Forest Growth Responses to Drought at Short- and Long-Term Scales in Spain: Squeezing the Stress Memory from Tree Rings

“…Lastly, black pine growth in southern Spain was severely impacted by the 1994-1995and 2005droughts (Sánchez-Salguero et al, 2013. However, what currently demands greater attention is to decipher the short-and long-term consequences of drought on forest growth and tree vigor (Anderegg et al, 2015;Peltier et al, 2016;Gazol et al, 2017a). We evidence that drought leads to legacy effects on tree growth and vigor, and that these effects can vary between and within (in the case of beech) tree species.…”

“…Nowadays, there is a growing scientific interest on forest reactions to drought across different biomes to discern which growth features or functional traits better characterize different species-specific responses to these climate extremes (Anderegg et al, 2013(Anderegg et al, , 2015(Anderegg et al, , 2016Vicente-Serrano et al, 2013;Gazol et al, 2017a). In this sense, annual growth rings provide short-(e.g., years) and long-term (e.g., decades) information on how trees respond to drought (e.g., Anderegg et al, 2015;Camarero et al, 2015b;Gazol and Camarero, 2016;Gazol et al, 2017c).…”

Forest resilience to drought varies across biomes

“…trend will negatively impact forest productivity and growth, and lead to more recurrent and widespread events of forest dieback and tree mortality (Camarero, Gazol, Sang€ uesa-Barreda, Oliva, & Vicente-Serrano, 2015;Gazol, Camarero, Anderegg, & Vicente-Serrano, 2017;Gea-Izquierdo et al, 2017; S anchez-Salguero, Navarro-Cerillo, Camarero, & Fern andez-Cancio, 2012;Sarris, Christodoulakis, & K€ orner, 2007). Drought intensity is usually considered the main driver causing forest growth decline although functional traits of tree species may also confer dissimilar levels of resistance to drought (Greenwood et al, 2017;Peltier, Fell, & Ogle, 2016;Yin & Bauerle, 2017).…”