Canopy Height and Climate Dryness Parsimoniously Explain Spatial Variation of Unstressed Stomatal Conductance. Issue 15 (8th August 2022)

• Record Type: Journal Article
• Authors: Liu, Yanlan; Flournoy, Olivia; Zhang, Quan; Novick, Kimberly A.; Koster, Randal D.; Konings, Alexandra G.
• Is Part Of: Geophysical research letters. Volume 49:Issue 15(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-08-08
• Subjects: unstressed stomatal conductance -- stomatal trait -- environment‐trait interaction -- canopy height -- climate dryness -- environmental filter; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2022GL099339
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: The spatio‐temporal variation of stomatal conductance directly regulates photosynthesis, water partitioning, and biosphere‐atmosphere interactions. While many studies have focused on stomatal response to stresses, the spatial variation of unstressed stomatal conductance remains poorly determined, and is usually characterized in land surface models (LSMs) simply based on plant functional type (PFT). Here, we derived unstressed stomatal conductance at the ecosystem‐scale using observations from 115 global FLUXNET sites. When aggregated by PFTs, the across‐PFT pattern was highly consistent with the parameterizations of LSMs. However, PFTs alone captured only 17% of the variation in unstressed stomatal conductance across sites. Within the same PFT, unstressed stomatal conductance was negatively related to climate dryness and canopy height, which explained 45% of the total spatial variation. Our results highlight the importance of plant‐environment interactions in shaping stomatal traits. The trait‐environment relationship established here provides an empirical approach for improved parameterizations of stomatal conductance in LSMs. Plain Language Summary: Stomatal conductance regulates the ease with which vegetation extracts water from the soil and releases it to the atmosphere. It thus helps determine the total evapotranspiration and plant uptake of carbon, which in turn significantly influences many aspects of ecosystem function, ranging from regional water resources to biodiversity and climate feedbacks. In particular, stomatal conductance under a stress‐free condition (without limitations from water, light, or other factors) acts as the basis of all mathematical models of stomatal dynamics. It is important to understand what causes the unstressed conductance to vary from one place to the next. Large‐scale models often assume the unstressed stomatal conductance is the same for all ecosystems belonging to the same plant functional type (PFT) (e.g., deciduous forests, grasslands, or croplands). However, based on observations at 115 sites across the globe, we showed that unstressed stomatal conductance varies significantly between sites within the same PFT. Sites located in drier climates and with taller canopies tended to have lower unstressed stomatal conductance. Accounting for climate dryness and canopy height helped better explain the spatial variation. Our results provide a useful approach to improving model descriptions of stomatal conductance. Key Points: Many large‐scale models represent the spatial patterns of unstressed stomatal conductance using plant functional types (PFTs) PFT‐averages of unstressed stomatal conductance at FLUXNET sites only capture 17 percent of spatial variability Spatial variation of unstressed stomatal conductance is better explained using climate dryness and canopy height