From: Are Northeastern U.S. forests vulnerable to extreme drought?
Citations | Measured parameters | Derived parameters | Characteristics of isohydric/anisohydric behavior | Related characteristics | Northeastern species |
---|---|---|---|---|---|
Loewenstein and Pallardy (1998) | Stomatal conductance (g s ), midday leaf water potential (Ψ md), predawn leaf water potential (Ψ pd) |  | Isohydric, little to no decline in Ψ md with decreasing Ψ pd due to greater stomatal closure Anisohydric, greater decline in Ψ md with decreasing Ψ pd | Greater concentrations of abscisic acid (ABA, root origin) during drought in isohydric species | Acer saccharum (A) Quercus alba (A) Juglans nigra (I) |
Tardieu and Simonneau (1998) | g s , leaf water potential (Ψ L ) |  | Isohydric; under high evaporative demand, Ψ L reaches a plateau due to stomatal closure regardless of soil moisture conditions Anisohydric, Ψ L declines with increasing evaporative demand and declining soil moisture with midday stomatal closure under severe water deficit | Isohydric species: g s more sensitive to ABA under high evaporative demand or water deficit. Anisohydric species: g s shows similar response to ABA regardless of evaporative demand or soil water deficit | N/A |
Sperry et al. (2002) | Midday leaf water potential (Ψ md), transpiration per leaf area area (E) |  | Isohydric, constant Ψ md during high evaporative demand that is maintained above critical water potential regardless of soil moisture Anisohydric, Ψ md declines with declining soil moisture until Ψ md approaches a critical Ψ md value | Isohydric and anisohydric species maintain smaller and larger hydraulic safety margins, respectively | N/A |
Martinez-Vilalta et al. (2014) | Predawn leaf water potential (Ψ pd), Ψ md | Slope of Ψ pd − Ψ md relationship (∂Ψpd/∂Ψmd) | Isohydric, ∂Ψpd/∂Ψmd = zero Anisohydric, ∂Ψpd/∂Ψmd > 1 | ∂Ψpd/∂Ψmd negatively correlated with mean summer VPD and P 50 | Quercus alba (partial isohydric) |
Klein (2014) | g s , Ψ L | Ψ at 50% g s of maximum g s \( \left({\varPsi}_{g_{s50}}\right) \) | Isohydric, greater \( {\varPsi}_{g_{s50}} \) across continuum Anisohydric, lower \( {\varPsi}_{g_{s50}} \) across continuum | Isohydric species have smaller P 50 | Liriodendron tulipifera (I) Acer saccharum (intermediate) |
Skelton et al. (2015) | g s , shoot water potential (Ψ), stem-specific conductivity (K s ) | Ψ at 12% g s of maximum g s (P g12), Ψ at 50% loss of conductivity (P 50) | Isohydric, (P g12 − P 50) = positive Anisohydric, (P g12 − P 50) = negative | Isohydric species maintain greater hydraulic safety margin | N/A |
Roman et al. (2015) | Ψ L , soil water potential (Ψ s ), g s , VPD | ∂Ψ L /∂Ψ s , ΔΨ = Ψ L  − Ψ s | Isohydric, ∂Ψ L /∂Ψ s  = 0 Anisohydric, ∂Ψ L /∂Ψ s  > 1 | Isohydric species become less sensitive to VPD due to decreasing ΔΨ and g s during drought | Quercus alba (A) Quercus rubra (A) Acer saccharum (I) Sassafras albidum (I) Liriodendron tulipifera (I) |
Garcia-Forner et al. (2016) | Ψ pd, Ψ md | ΔΨ = Ψ pd − Ψ md | Isohydric, less variation in ΔΨ Anisohydric, greater variation in ΔΨ | Anisohydric species showed greater stomatal control than expected | N/A |
Meinzer et al. (2016) | Ψ pd, Ψ md, leaf osmotic potential at full turgor (Ψ π 100), Leaf water potential at turgor loss point (Ψ TLP) | Hydroscape area: Area of triangle bounded by Ψ pd − Ψ md regression line and 1:1 line | Isohydric, smaller hydroscape area Anisohydric, large hydroscape area | Hydroscape area strongly correlated with Ψ π 100 and Ψ TLP across species | N/A |