Towards species‐level forecasts of drought‐induced tree mortality risk

Abstract

Predicting species-level responses to drought at the landscape scale is critical to reducing uncertainty in future terrestrial carbon and water cycle projections.We embedded a stomatal optimisation model in the Community Atmosphere Biosphere Land Exchange (CABLE) land surface model and parameterised the model for 15 canopy dominant eucalypt tree species across South-Eastern Australia (mean annual precipitation range: 344-1424 mm yr −1 ). We conducted three experiments: applying CABLE to the 2017-2019 drought; a 20% drier drought; and a 20% drier drought with a doubling of atmospheric carbon dioxide (CO 2 ).The severity of the drought was highlighted as for at least 25% of their distribution ranges, 60% of species experienced leaf water potentials beyond the water potential at which 50% of hydraulic conductivity is lost due to embolism. We identified areas of severe hydraulic stress within-species' ranges, but we also pinpointed resilience in species found in predominantly semiarid areas. The importance of the role of CO 2 in ameliorating drought stress was consistent across species.Our results represent an important advance in our capacity to forecast the resilience of individual tree species, providing an evidence base for decision-making around the resilience of restoration plantings or net-zero emission strategies.

Non‐Stationary Lags and Legacies in Ecosystem Flux Response to Antecedent Rainfall

“…This capacity to isolate the timescales of influence of both the past extremes and behavioral lags opens important avenues around the introduction of new theory into LSMs to capture ecosystem memory to climate. Our framework provides an approach for important checks on model hypothesis testing around the introduction of new theory related to plant hydraulics (De Kauwe et al., 2022; Sabot et al., 2020, 2022), acclimation (Mercado et al., 2018; Smith & Dukes, 2013), and carbon storage (De Kauwe et al., 2014; Fatichi et al., 2014; Jones et al., 2020). Implementing model hypotheses intended to improve the response timescales of vegetation to climate into LSMs, and then comparing the results between the model and observations when passed through frameworks such as ours, will ensure that model development is correctly capturing the timescales of influence that are evident in the observational records.…”

“…Climate change is increasing the frequency and intensity of some meteorological extremes, with implications for the terrestrial carbon and water cycles (Allen et al., 2015; Dunn et al., 2020; IPCC, 2021; Reichstein et al., 2013). Extreme rainfall has become more intense on short timescales (Allan & Soden, 2008; Min et al., 2011; X. Zhang et al., 2013), summer heatwaves have become more frequent and intense (Alexander, 2016; Perkins‐Kirkpatrick & Lewis, 2020; Schär et al., 2004; Stott et al., 2004) and incidents of record‐breaking and multi‐year droughts have been observed globally (De Kauwe et al., 2022; Jiménez‐Muñoz et al., 2016; Szejner et al., 2020; Williams et al., 2022). These weather extremes affect the vegetation through reductions in function (Ciais et al., 2005; Frank et al., 2015; Ma et al., 2016; Moran et al., 2014; Zscheischler et al., 2014a, 2014b) and in extreme cases, lead directly to mortality (Anderegg et al., 2015a; Arend et al., 2021).…”

A joint framework for studying compound ecoclimatic events

“…A mechanistic representation of the processes driving ecosystem dynamics, disturbances and their feedbacks in global land surface models is therefore needed when projecting future climate changes. Efforts to improve the representation of forest responses to climate stressors [160][161][162] and tree mortality [163][164][165] , of functional diversity 166 and of management activities 167 , and to prognostically simulate disturbances beyond fire in land surface models 168 , are currently ongoing. These efforts are promising, but are still challenged by the lack of data needed to develop underlying theory.…”

Changes in Blue/Green Water Partitioning Under Severe Drought

“…Vegetation resilience and adaptation to drought influences catchment response via plant‐water interactions. These topics have been a major research focus both within Australia and globally (De Kauwe et al., 2020, 2022; Hartmann et al., 2018; McDowell et al., 2008; Nolan et al., 2018; Senf et al., 2020). Focusing on cropland and grassland, Sawada and Koike (2016) used a combination of remote sensing and modeling to demonstrate high ecosystem resilience to the Millennium Drought, achieved through strategic shifts in plant carbon (C) allocation strategies.…”