Hydrologic balance in an intact temperate forest ecosystem under ambient and elevated atmospheric CO2 concentration

Karina Schafer, Ram Oren, Chun Ta Lai, Gabriel G. Katul

Research output: Contribution to journalArticle

141 Citations (Scopus)

Abstract

Increasing atmospheric CO2 concentration decreases stomatal conductance in many species, but the savings of water from reduced transpiration may permit the forest to retain greater leaf area index (L). Therefore, the net effect on water use in forest ecosystems under a higher CO2 atmosphere is difficult to predict. The free air CO2 enrichment (FACE) facility (n=3) in a 14-m tall (in 1996) Pinus taeda L. stand was designed to reduce uncertainties in predicting such responses. Continuous measurements of precipitation, throughfall precipitation, sap flux, and soil moisture were made over 3.5 years under ambient (CO2a) and elevated (CO2e) ambient + 200 μmol mol-1). Annual stand transpiration under ambient CO2 conditions accounted for 84-96% of latent heat flux measured with the eddy-covariance technique above the canopy. Under CO2e, P. taeda transpired less per unit of leaf area only when soil drought was severe. Liquidambar styraciflua, the other major species in the forest, used progressively less water, settling at 25% reduction in sap flux density after 3.5 years under CO2e. Because P. taeda dominated the stand, and severe drought periods were of relatively short duration, the direct impact of CO2e on water savings in the stand was undetectable. Moreover, the forest used progressively more water under CO2e, probably because soil moisture availability progressively increased, probably owing to a reduction in soil evaporation caused by more litter buildup in the CO2e plots. The results suggest that, in this forest, the effect of CO2e on transpiration was greater indirectly through enhanced litter production than directly through reduced stomatal conductance. In forests composed of species more similar to L. styraciflua, water savings from stomatal closure may dominate the response to CO2e.

Original languageEnglish (US)
Pages (from-to)895-911
Number of pages17
JournalGlobal Change Biology
Volume8
Issue number9
DOIs
StatePublished - Sep 11 2002

Fingerprint

temperate forest
Ecosystems
forest ecosystem
Transpiration
Water
transpiration
stomatal conductance
Drought
Soil moisture
litter
soil moisture
drought
Fluxes
throughfall
Soils
eddy covariance
latent heat flux
leaf area index
water
Latent heat

All Science Journal Classification (ASJC) codes

  • Environmental Science(all)
  • Global and Planetary Change
  • Ecology
  • Environmental Chemistry

Keywords

  • Canopy transpiration
  • Elevated CO
  • Liquidambar styraciflua
  • Pinus taeda
  • Ulmus alata
  • Water balance

Cite this

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title = "Hydrologic balance in an intact temperate forest ecosystem under ambient and elevated atmospheric CO2 concentration",
abstract = "Increasing atmospheric CO2 concentration decreases stomatal conductance in many species, but the savings of water from reduced transpiration may permit the forest to retain greater leaf area index (L). Therefore, the net effect on water use in forest ecosystems under a higher CO2 atmosphere is difficult to predict. The free air CO2 enrichment (FACE) facility (n=3) in a 14-m tall (in 1996) Pinus taeda L. stand was designed to reduce uncertainties in predicting such responses. Continuous measurements of precipitation, throughfall precipitation, sap flux, and soil moisture were made over 3.5 years under ambient (CO2a) and elevated (CO2e) ambient + 200 μmol mol-1). Annual stand transpiration under ambient CO2 conditions accounted for 84-96{\%} of latent heat flux measured with the eddy-covariance technique above the canopy. Under CO2e, P. taeda transpired less per unit of leaf area only when soil drought was severe. Liquidambar styraciflua, the other major species in the forest, used progressively less water, settling at 25{\%} reduction in sap flux density after 3.5 years under CO2e. Because P. taeda dominated the stand, and severe drought periods were of relatively short duration, the direct impact of CO2e on water savings in the stand was undetectable. Moreover, the forest used progressively more water under CO2e, probably because soil moisture availability progressively increased, probably owing to a reduction in soil evaporation caused by more litter buildup in the CO2e plots. The results suggest that, in this forest, the effect of CO2e on transpiration was greater indirectly through enhanced litter production than directly through reduced stomatal conductance. In forests composed of species more similar to L. styraciflua, water savings from stomatal closure may dominate the response to CO2e.",
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Hydrologic balance in an intact temperate forest ecosystem under ambient and elevated atmospheric CO2 concentration. / Schafer, Karina; Oren, Ram; Lai, Chun Ta; Katul, Gabriel G.

In: Global Change Biology, Vol. 8, No. 9, 11.09.2002, p. 895-911.

Research output: Contribution to journalArticle

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AU - Oren, Ram

AU - Lai, Chun Ta

AU - Katul, Gabriel G.

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KW - Ulmus alata

KW - Water balance

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