Species variation in water relations and xylem vulnerability to cavitation at a forest-woodland ecotone

Dan F. Koepke, Thomas E Kolb

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

Xylem vulnerability to cavitation and response of water potential (Ψ), stomatal conductance (gs), and net photosynthesis (P n) to drought are potentially important mechanisms of drought resistance. We compared Ψ, gs, P n, and cavitation vulnerability of shoot and root xylem among co-occurring ponderosa pine (Pinus ponderosa var. scopulorum Dougl. Ex Laws.), pinyon pine (Pinus edulis Engelm.), and Utah juniper (Juniperus osteosperma [Torr.] Little) at a forest-woodland ecotonal site in northern Arizona to elucidate drought resistance mechanisms of these species. Juniper shoots partly regulated Ψ during drought via stomatal closure, but regulation was weaker than that for ponderosa and pinyon pines, which had similar water relations and P n responses to drought. Midday gs and P n during summer drought were positive for juniper (gs = 14.3 mmol m-2 s-1, P n = 1.23 μmol m-2 s-1) but near zero for ponderosa (gs= 0.7 mmol m-2 s-1, P n = -0.02 μmol m-2 s-1) and pinyon (gs = 1.5 mmol m-2 s-1, P n = -0.18 μmol m-2 s-1) pines. Cavitation vulnerability of shoots and roots was lower for juniper than for both pines. The water potential inducing 50% loss in xylem hydraulic conductivity (Ψ50) for juniper was 5.0 MPa more negative for shoots and 3.9 MPa more negative for roots compared with the respective tissues of the pine species. Pinyon pine (Ψ50 = -2.71 MPa) was slightly more vulnerable to cavitation than ponderosa pine (Ψ50 = -3.42 MPa) for shoots, whereas root vulnerability was similar for both pines (Ψ50 = -1.69 MPa for pinyon; -1.98 MPa for ponderosa). Roots of all species were more vulnerable to cavitation than shoots. Our results show an important role of cavitation vulnerability in the greater drought resistance of Utah juniper than pinyon and ponderosa pines but not for the presumed greater drought resistance of pinyon pine than ponderosa pine.

Original languageEnglish (US)
Pages (from-to)524-535
Number of pages12
JournalForest Science
Volume59
Issue number5
DOIs
StatePublished - Oct 6 2013

Fingerprint

Pinus edulis
water relations
cavitation
ecotones
ecotone
xylem
woodlands
woodland
photosynthesis
vulnerability
drought resistance
shoot
Juniperus osteosperma
drought tolerance
shoots
Pinus
drought
water
Pinus ponderosa
water potential

Keywords

  • Arizona
  • Drought
  • Juniperus osteosperma
  • Pinus edulis
  • Pinus ponderosa

ASJC Scopus subject areas

  • Forestry
  • Ecological Modeling
  • Ecology

Cite this

Species variation in water relations and xylem vulnerability to cavitation at a forest-woodland ecotone. / Koepke, Dan F.; Kolb, Thomas E.

In: Forest Science, Vol. 59, No. 5, 06.10.2013, p. 524-535.

Research output: Contribution to journalArticle

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abstract = "Xylem vulnerability to cavitation and response of water potential (Ψ), stomatal conductance (gs), and net photosynthesis (P n) to drought are potentially important mechanisms of drought resistance. We compared Ψ, gs, P n, and cavitation vulnerability of shoot and root xylem among co-occurring ponderosa pine (Pinus ponderosa var. scopulorum Dougl. Ex Laws.), pinyon pine (Pinus edulis Engelm.), and Utah juniper (Juniperus osteosperma [Torr.] Little) at a forest-woodland ecotonal site in northern Arizona to elucidate drought resistance mechanisms of these species. Juniper shoots partly regulated Ψ during drought via stomatal closure, but regulation was weaker than that for ponderosa and pinyon pines, which had similar water relations and P n responses to drought. Midday gs and P n during summer drought were positive for juniper (gs = 14.3 mmol m-2 s-1, P n = 1.23 μmol m-2 s-1) but near zero for ponderosa (gs= 0.7 mmol m-2 s-1, P n = -0.02 μmol m-2 s-1) and pinyon (gs = 1.5 mmol m-2 s-1, P n = -0.18 μmol m-2 s-1) pines. Cavitation vulnerability of shoots and roots was lower for juniper than for both pines. The water potential inducing 50{\%} loss in xylem hydraulic conductivity (Ψ50) for juniper was 5.0 MPa more negative for shoots and 3.9 MPa more negative for roots compared with the respective tissues of the pine species. Pinyon pine (Ψ50 = -2.71 MPa) was slightly more vulnerable to cavitation than ponderosa pine (Ψ50 = -3.42 MPa) for shoots, whereas root vulnerability was similar for both pines (Ψ50 = -1.69 MPa for pinyon; -1.98 MPa for ponderosa). Roots of all species were more vulnerable to cavitation than shoots. Our results show an important role of cavitation vulnerability in the greater drought resistance of Utah juniper than pinyon and ponderosa pines but not for the presumed greater drought resistance of pinyon pine than ponderosa pine.",
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N2 - Xylem vulnerability to cavitation and response of water potential (Ψ), stomatal conductance (gs), and net photosynthesis (P n) to drought are potentially important mechanisms of drought resistance. We compared Ψ, gs, P n, and cavitation vulnerability of shoot and root xylem among co-occurring ponderosa pine (Pinus ponderosa var. scopulorum Dougl. Ex Laws.), pinyon pine (Pinus edulis Engelm.), and Utah juniper (Juniperus osteosperma [Torr.] Little) at a forest-woodland ecotonal site in northern Arizona to elucidate drought resistance mechanisms of these species. Juniper shoots partly regulated Ψ during drought via stomatal closure, but regulation was weaker than that for ponderosa and pinyon pines, which had similar water relations and P n responses to drought. Midday gs and P n during summer drought were positive for juniper (gs = 14.3 mmol m-2 s-1, P n = 1.23 μmol m-2 s-1) but near zero for ponderosa (gs= 0.7 mmol m-2 s-1, P n = -0.02 μmol m-2 s-1) and pinyon (gs = 1.5 mmol m-2 s-1, P n = -0.18 μmol m-2 s-1) pines. Cavitation vulnerability of shoots and roots was lower for juniper than for both pines. The water potential inducing 50% loss in xylem hydraulic conductivity (Ψ50) for juniper was 5.0 MPa more negative for shoots and 3.9 MPa more negative for roots compared with the respective tissues of the pine species. Pinyon pine (Ψ50 = -2.71 MPa) was slightly more vulnerable to cavitation than ponderosa pine (Ψ50 = -3.42 MPa) for shoots, whereas root vulnerability was similar for both pines (Ψ50 = -1.69 MPa for pinyon; -1.98 MPa for ponderosa). Roots of all species were more vulnerable to cavitation than shoots. Our results show an important role of cavitation vulnerability in the greater drought resistance of Utah juniper than pinyon and ponderosa pines but not for the presumed greater drought resistance of pinyon pine than ponderosa pine.

AB - Xylem vulnerability to cavitation and response of water potential (Ψ), stomatal conductance (gs), and net photosynthesis (P n) to drought are potentially important mechanisms of drought resistance. We compared Ψ, gs, P n, and cavitation vulnerability of shoot and root xylem among co-occurring ponderosa pine (Pinus ponderosa var. scopulorum Dougl. Ex Laws.), pinyon pine (Pinus edulis Engelm.), and Utah juniper (Juniperus osteosperma [Torr.] Little) at a forest-woodland ecotonal site in northern Arizona to elucidate drought resistance mechanisms of these species. Juniper shoots partly regulated Ψ during drought via stomatal closure, but regulation was weaker than that for ponderosa and pinyon pines, which had similar water relations and P n responses to drought. Midday gs and P n during summer drought were positive for juniper (gs = 14.3 mmol m-2 s-1, P n = 1.23 μmol m-2 s-1) but near zero for ponderosa (gs= 0.7 mmol m-2 s-1, P n = -0.02 μmol m-2 s-1) and pinyon (gs = 1.5 mmol m-2 s-1, P n = -0.18 μmol m-2 s-1) pines. Cavitation vulnerability of shoots and roots was lower for juniper than for both pines. The water potential inducing 50% loss in xylem hydraulic conductivity (Ψ50) for juniper was 5.0 MPa more negative for shoots and 3.9 MPa more negative for roots compared with the respective tissues of the pine species. Pinyon pine (Ψ50 = -2.71 MPa) was slightly more vulnerable to cavitation than ponderosa pine (Ψ50 = -3.42 MPa) for shoots, whereas root vulnerability was similar for both pines (Ψ50 = -1.69 MPa for pinyon; -1.98 MPa for ponderosa). Roots of all species were more vulnerable to cavitation than shoots. Our results show an important role of cavitation vulnerability in the greater drought resistance of Utah juniper than pinyon and ponderosa pines but not for the presumed greater drought resistance of pinyon pine than ponderosa pine.

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KW - Juniperus osteosperma

KW - Pinus edulis

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