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Worldwide impacts of atmospheric vapor pressure deficit on the interannual variability of terrestrial carbon sinks.

ABSTRACT: Interannual variability of the terrestrial ecosystem carbon sink is substantially regulated by various environmental variables and highly dominates the interannual variation of atmospheric carbon dioxide (CO₂) concentrations. Thus, it is necessary to determine dominating factors affecting the interannual variability of the carbon sink to improve our capability of predicting future terrestrial carbon sinks. Using global datasets derived from machine-learning methods and process-based ecosystem models, this study reveals that the interannual variability of the atmospheric vapor pressure deficit (VPD) was significantly negatively correlated with net ecosystem production (NEP) and substantially impacted the interannual variability of the atmospheric CO₂ growth rate (CGR). Further analyses found widespread constraints of VPD interannual variability on terrestrial gross primary production (GPP), causing VPD to impact NEP and CGR. Partial correlation analysis confirms the persistent and widespread impacts of VPD on terrestrial carbon sinks compared to other environmental variables. Current Earth system models underestimate the interannual variability in VPD and its impacts on GPP and NEP. Our results highlight the importance of VPD for terrestrial carbon sinks in assessing ecosystems' responses to future climate conditions.

SUBMITTER: He B

PROVIDER: S-EPMC8982191 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description: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.

Project description:Low atmospheric relative humidity (RH) accompanied by elevated air temperature and decreased precipitation are environmental challenges that wheat production will face in future decades. These changes to the atmosphere are causing increases in air vapor pressure deficit (VPD) and low soil water availability during certain periods of the wheat-growing season. The main objective of this study was to analyze the physiological, metabolic, and transcriptional response of carbon (C) and nitrogen (N) metabolism of wheat (Triticum durum cv. Sula) to increases in VPD and soil water stress conditions, either alone or in combination. Plants were first grown in well-watered conditions and near-ambient temperature and RH in temperature-gradient greenhouses until anthesis, and they were then subjected to two different water regimes well-watered (WW) and water-stressed (WS), i.e., watered at 50% of the control for one week, followed by two VPD levels (low, 1.01/0.36 KPa and high, 2.27/0.62 KPa; day/night) for five additional days. Both VPD and soil water content had an important impact on water status and the plant physiological apparatus. While high VPD and water stress-induced stomatal closure affected photosynthetic rates, in the case of plants watered at 50%, high VPD also caused a direct impairment of the RuBisCO large subunit, RuBisCO activase and the electron transport rate. Regarding N metabolism, the gene expression, nitrite reductase (NIR) and transport levels detected in young leaves, as well as determinations of the δ15N and amino acid profiles (arginine, leucine, tryptophan, aspartic acid, and serine) indicated activation of N metabolism and final transport of nitrate to leaves and photosynthesizing cells. On the other hand, under low VPD conditions, a positive effect was only observed on gene expression related to the final step of nitrate supply to photosynthesizing cells, whereas the amount of 15N supplied to the roots that reached the leaves decreased. Such an effect would suggest an impaired N remobilization from other organs to young leaves under water stress conditions and low VPD.

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Worldwide impacts of atmospheric vapor pressure deficit on the interannual variability of terrestrial carbon sinks.

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