Recovery of Ecosystem Carbon and Energy Fluxes From the 2003 Drought in Europe and the 2012 Drought in the United States

Abstract

Recovery of an ecosystem from drought is an important indicator of ecosystem resilience. However, few investigations have heretofore focused on the recovery of ecosystem carbon and energy fluxes but have mainly focused on the drought recovery of plant growth and ecosystem productions. Therefore, the present study uses in situ observations from FLUXNET 2015 to examine the recovery of carbon flux and energy flux of ecosystems from the 2003 European drought and the 2012 U.S. drought on the daily scale. The results reveal the strong impact of these two extreme droughts on ecosystem gross primary production, total ecosystem respiration, net ecosystem exchange, and latent heat flux. In addition, the recovery time of these indicators differ significantly. At the regional scale, the recovery of gross primary production, total ecosystem respiration, net ecosystem exchange, and latent heat flux took 44, 23, 63, and 27 days after the 2003 European drought, and the recovery for corresponding indicators for the 2012 U.S. drought took 42, 63, 15, and 33 days, respectively. Further investigations suggest that indicator background conditions and drought‐damage magnitudes played an important role in regulating drought recovery in the 2003 European drought, with lower background value and greater damage leading to a longer recovery time. The ecosystem recovery from the 2012 U.S. drought, however, was dominated by the precipitation condition during the recovery period, with more precipitation associated with a shorter recovery time. These results provide crucial insight into the divergent recovery trajectories for different carbon‐water processes among diverse bioclimatic regions.

The impact of drought spells on forests depends on site conditions: The case of 2017 summer heat wave in southern Europe

“…Kreyling et al, ) and tree resistance to pest attacks (e.g. Rouault et al, ), which compromised the ability of trees to recover growth and contributed to increase mortality during the following years (He et al, ).…”

“…For instance, in addition to the general response of forests shifting from carbon sinks to carbon sources in low, mesic sites (Ciais et al, ; Reichstein et al, ), at high elevations, enhanced vegetation growth is driven by high temperatures (Jolly et al, ). Differences among forest types/species were also found either in the extent of damage (for instance Bonal, Pau, Toigo, Granier, & Perot, ; Bréda, Huc, Granier, & Dreyer, ) or recovery rate (He et al, ; but see also Pretzsch, Schütze, & Uhl, for mixed vs. pure forest stands comparison) following the 2003 European drought.…”

Revisiting assessments of ecosystem drought recovery

“…Currently, drought recovery is tracked from drought ending time, but the drought legacy effects are reported to be prevalent in dry ecosystems (Liu et al 2018b), which could bias the drought recovery time. An alternative approach that may be worth to explore in future is to identify GPP extremes first (Zscheischler et al 2013) and track the drought recovery from the maximum negative GPP magnitude (He et al 2018).…”

“…Pre-drought based recovery level, i.e. the averaged ecosystem production in a period before the start of the drought, is most commonly used (Wolf et al 2016, Schwalm et al 2017, He et al 2018. Recovering to the level of ecosystem production before the drought is closely linked to the concept of 'drought recovery', and it is easy to calculate.…”

“…One way to determine recovery level is the averaged ecosystem production in a pre-drought period. However, the length of the pre-drought period is often determined subjectively and varies largely across studies (Gazol et al 2017, Schwalm et al 2017, He et al 2018. In addition, previous global-scale studies only used a single metric to identify drought events, and almost all identified drought events are used to assess drought recovery.…”