Systemic effects of rising atmospheric vapor pressure deficit on plant physiology and productivity

Abstract

Earth is currently undergoing a global increase in atmospheric vapor pressure deficit (VPD), a trend which is expected to continue as climate warms. This phenomenon has been associated with productivity decreases in ecosystems and yield penalties in crops, with these losses attributed to photosynthetic limitations arising from decreased stomatal conductance. Such VPD increases, however, have occurred over decades, which raises the possibility that stomatal acclimation to VPD plays an important role in determining plant productivity under high VPD. Furthermore, evidence points to more far‐ranging and complex effects of elevated VPD on plant physiology, extending to the anatomical, biochemical, and developmental levels, which could vary substantially across species. Because these complex effects are typically not considered in modeling frameworks, we conducted a quantitative literature review documenting temperature‐independent VPD effects on 112 species and 59 traits and physiological variables, in order to develop an integrated and mechanistic physiological framework. We found that VPD increase reduced yield and primary productivity, an effect that was partially mediated by stomatal acclimation, and also linked with changes in leaf anatomy, nutrient, and hormonal status. The productivity decrease was also associated with negative effects on reproductive development, and changes in architecture and growth rates that could decrease the evaporative surface or minimize embolism risk. Cross‐species quantitative relationships were found between levels of VPD increase and trait responses, and we found differences across plant groups, indicating that future VPD impacts will depend on community assembly and crop functional diversity. Our analysis confirms predictions arising from the hydraulic corollary to Darcy's law, outlines a systemic physiological framework of plant responses to rising VPD, and provides recommendations for future research to better understand and mitigate VPD‐mediated climate change effects on ecosystems and agro‐systems.

Limited thermal acclimation of photosynthesis in tropical montane tree species

“…guineense only (Figures 2 and 3). In the short term, g s typically decreases with the increasing VPD accompanying an increase in temperature (Figures S2 and S4; Grossiord et al, 2020; López et al, 2021; Oren et al, 1999). The decrease acts to prevent water loss in high‐VPD air, but simultaneously restricts the CO 2 supply for photosynthesis (Farquhar & Sharkey, 1982).…”

“…This response contrasts the least‐cost theory (Prentice et al, 2014) and our second hypothesis. Clearly, additional studies that explore long‐term responses of g s to high temperature and VPD are needed (Grossiord et al, 2020; López et al, 2021; Marchin et al, 2016; Oren et al, 1999). Such knowledge is critical since the response of g s to global change factors has been identified as an important factor that will dictate climate change responses of terrestrial productivity, hydrology and energy balance (Cernusak et al, 2019; Grossiord et al, 2020), particularly for tropical forests (Doughty & Goulden, 2008; McDowell et al, 2018; Tan et al, 2017).…”

“…In our study, g s at a given leaf temperature increased with warming, particularly in the leaf temperature range between 25 and 35℃, but this increase was significant in S. guineense only (Figures 2 and 3). In the short term, g s typically decreases with the increasing VPD accompanying an increase in temperature (Figures S2 and S4;Grossiord et al, 2020;López et al, 2021;Oren et al, 1999). The decrease acts to prevent water loss in high-VPD air, but simultaneously restricts the CO 2 supply for photosynthesis (Farquhar & Sharkey, 1982).…”

“…The few data available on tropical trees show that V cmax25 and J max25 were not impacted by warming (Scafaro et al, 2017;Crous et al, 2018;Fauset et al, 2019; but see Kositsup et al, 2009). Although g s decreases as a response to the short-term increases in the vapor pressure deficit (VPD) that are typically associated with increasing temperature (Grossiord et al, 2020;López et al, 2021;Oren et al, 1999), g s may also acclimate to long-term warming. In different tree species, g s increased (Marchin et al, 2016), decreased (Dusenge et al, 2020;Fauset et al, 2019;Lamba et al, 2018) or remained unchanged (Drake et al, 2015;Dusenge et al, 2020) with growth at elevated temperatures.…”

The Decline In Summer Fallow In The Northern Plains Cooled Near-Surface Climate But Had Minimal Impacts On Precipitation

“…110,000 km 2 (25% of Canada's cultivated lands) to some 35,000 km 2 (8%) (Gameda et al 2007; Vick et al 2016). In the U.S. portion of the NNAGP and across a similar time period, near-surface air temperatures have cooled by nearly 0.2°C decade − 1 during late spring and early summer, and nearsurface atmospheric vapor pressure de cit (VPD) -which strongly depletes crop yields (López et al 2021) -has decreased by − 0.04 kPa decade − 1 on average (Bromley et al 2020). These changes to the regional climate are concurrent with a period of summer fallow decline on the order of 50,000 km 2 in the United States from a peak in 1987 until 2012 (Fig.…”