Drought legacies are dependent on water table depth, wood anatomy and drought timing across the eastern US

Abstract

Severe droughts can impart long‐lasting legacies on forest ecosystems through lagged effects that hinder tree recovery and suppress whole‐forest carbon uptake. However, the local climatic and edaphic factors that interact to affect drought legacies in temperate forests remain unknown. Here, we pair a dataset of 143 tree ring chronologies across the mesic forests of the eastern US with historical climate and local soil properties. We found legacy effects to be widespread, the magnitude of which increased markedly in diffuse porous species, sites with deep water tables, and in response to late‐season droughts (August–September). Using an ensemble of downscaled climate projections, we additionally show that our sites are projected to drastically increase in water deficit and drought frequency by the end of the century, potentially increasing the size of legacy effects by up to 65% and acting as a significant process shaping forest composition, carbon uptake and mortality.

Linking drought legacy effects across scales: From leaves to tree rings to ecosystems

“…We found legacy effects in tree rings to be highly species specific, but the stand-weighted size (~10%) was in line with other investigations (Anderegg et al, 2015;Gazol et al, 2017;Camarero et al, 2018;Kannenberg, Maxwell, et al, 2019). In accordance with other recent studies (Elliott, Miniat, Pederson, & Laseter, 2015;Kannenberg, Maxwell, et al, 2019;Yi et al, 2019), we found species with diffuse porous wood anatomy (A. saccharum and L. tulipifera) to be more sensitive to drought and have larger legacy effects. In the context of the 2012 drought, which occurred later relative to the start of the growing season, wood anatomy could play a large role in dictating drought responses and recovery.…”

“…However, these experimental droughts are likely more severe than those in forests, potentially introducing biochemical (instead of stomatal) limitations on photosynthesis (Flexas & Medrano, 2002). These results confirm previous work indicating that numerous aspects of L. tulipifera physiology are highly sensitive to drought, including RWI (Kannenberg, Maxwell, et al, 2019), radial growth (Brzostek et al, 2014), sap flux (Yi, Dragoni, Phillips, Roman, & Novick, 2017), and photosynthesis (Roman et al, 2015). These results confirm previous work indicating that numerous aspects of L. tulipifera physiology are highly sensitive to drought, including RWI (Kannenberg, Maxwell, et al, 2019), radial growth (Brzostek et al, 2014), sap flux (Yi, Dragoni, Phillips, Roman, & Novick, 2017), and photosynthesis (Roman et al, 2015).…”

“…increasing recognition of the importance of legacy effects on tree growth(Anderegg et al, 2015;Gazol et al, 2017;Camarero et al, 2018;Kannenberg, Maxwell, et al, 2019;Peltier et al, 2016), F I G U R E 4 Seasonal cycles of daily gross primary productivity (GPP) during the 2012 drought, the 2013 "legacy effect" year, and all other years within the flux record. (a) GPP partitioned using the nighttime approach.…”

Delineating Environmental Stresses to Primary Production of U.S. Forests From Tree Rings: Effects of Climate Seasonality, Soil, and Topography

“…The RF model experiments show that climate gradients alone cannot capture spatial variation of environmental stress, except in ecoregions that are strongly limited by climate, such as the driest regions of the western United States, and the mixed effect models further demonstrate the importance of interactions between site characteristics (especially topography) and climate. We did not find strong effects of soil characteristics, possibly due to limitations of the gridded soil data, but previous work has demonstrated the effects of both topography and soils on forest responses to drought and other climatic stresses (Fan et al, ; Kannenberg et al, ; Phillips et al, ). Incorporating either topographic or soil variables in addition to climate variables could substantially improve model performance.…”

Legacies of more frequent drought in ponderosa pine across the western United States

“…In particular, legacy effects of drought-multiyear recoveries of trees from drought, due to induced shifts in growth-climate sensitivities-have the potential to decrease the predictability of forest carbon fluxes worldwide (Anderegg, Schwalm, et al, 2015;Kolus et al, 2019;Peltier, Fell, & Ogle, 2016;Schwalm et al, 2017). This has spurred a growing body of research that aims to characterize drought legacies across the globe (Gao et al, 2018;Huang, Wang, Keenan, & Piao, 2018;Jiang et al, 2019;Kannenberg et al, 2018;O'Brien, Ong, & Reynolds, 2017; Serra-Maluquer, Mencuccini, & Martínez-Vilalta, 2018;Wu et al, 2018;Yin & Bauerle, 2017). Mechanisms underlying drought legacies include decreases in active xylem area, loss of root function, deep soil moisture depletion, needle shedding or canopy loss, and changes in the amounts or availability of stored nonstructural carbohydrates (NSC), among others (Adams et al, 2017;Barbaroux & Bréda, 2002;Brodersen & McElrone, 2013;Fritts, 1976;Galiano, Martínez-Vilalta, & Lloret, 2011;Hagedorn et al, 2016;Rempe & Dietrich, 2018;Resco et al, 2009;Sala, Piper, & Hoch, 2010;Sevanto et al, 2014).…”