Dryland mechanisms could widely control ecosystem functioning in a drier and warmer world

Abstract

Responses of terrestrial ecosystems to climate change have been explored in many regions worldwide. While continued drying and warming may alter process rates and deteriorate the state and performance of ecosystems, it could also lead to more fundamental changes in the mechanisms governing ecosystem functioning. Here, we argue that climate change will induce unprecedented shifts in these mechanisms in historically wetter climatic zones, towards mechanisms currently prevalent in dry regions, which we refer to as "dryland mechanisms". We discuss twelve dryland mechanisms affecting multiple processes of ecosystem functioning, including vegetation development, water flow, energy budget, carbon and nutrient cycling, plant production and organic matter decomposition. We then examine mostly rare examples of the operation of these mechanisms in non-dryland regions where they have been considered insignificant at present. Current and future climate trends could force microclimatic conditions across thresholds and lead to the emergence of dryland mechanisms and their increasing control over ecosystem functioning in many biomes on Earth.

Drought legacies and ecosystem responses to subsequent drought

“…In addition to drought‐induced adaptations, degradations of intrinsic factors can have an important influence on ecosystem responses to subsequent droughts. In fact, it has been suggested that an increasing amount of land area globally may be degraded by aridity in the long‐term due to shifts in precipitation regimes (Berdugo et al, 2020), activating a range of dryland mechanisms (Grünzweig et al, 2022). Increased aridity can hamper the recovery after a drought event and lead to more extreme responses to recurrent drought events.…”

Mapping the effects of climate change on reference evapotranspiration in future scenarios in the Brazilian Semiarid Region - South America

“…In addition, the amplification of water deficit levels due to the increase in ETo can change the patterns of the spatial distribution of vegetation (Burrell et al, 2020;Castro Oliveira et al, 2021;Grünzweig et al, 2022). Modeling of future scenarios has shown that by the end of the century, vegetation with xerophytic characteristics will extend into the BSR (Castro Oliveira et al, 2021), mainly on the southern edge (latitude 15° S), where maximum ETo values may extend (Figures 5 and 6).…”

A multi‐satellite framework to rapidly evaluate extreme biosphere cascades: The Western US 2021 drought and heatwave

“…These extreme events may leave long-lasting negative imprints on the biosphere (Ciais et al, 2005;Green et al, 2019) because slow biospheric carbon uptake can be compensated by rapid carbon releases due to extremes and disturbances (Körner, 2003). These extremes can also cause crossing of landscape thresholds and activation of biosphere mechanisms not typically experienced at that location (Grünzweig et al, 2022).…”

“…These extreme events may leave long‐lasting negative imprints on the biosphere (Ciais et al, 2005; Green et al, 2019) because slow biospheric carbon uptake can be compensated by rapid carbon releases due to extremes and disturbances (Körner, 2003). These extremes can also cause crossing of landscape thresholds and activation of biosphere mechanisms not typically experienced at that location (Grünzweig et al, 2022). Furthermore, droughts and heatwaves can amplify carbon uptake interannual variability (Ahlström et al, 2015; Luo & Keenan, 2022; Poulter et al, 2014), confounding how fossil CO 2 mitigation will be detected in the atmosphere at interannual timescales.…”