Topographical and seasonal trends in transpiration by two co-occurring Eucalyptus species during two contrasting years in a low rainfall environment

Isa A.M. Yunusa, Colin D. Aumann, M.A. Rab, Noel Merrick, Peter D. Fisher, Philip Eberbach, Derek Eamus

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

Understanding the strategies that confer resilience on natural woodlands in drought prone environments is important for the conservation of these and similar ecosystems. Our main aim in this 2-year study was to assess traits (sapwood area, sapwood density and leaf area index) that control transpiration in Eucalyptus camaldulensis and E. microcarpa in a natural forest in which topographical variation created surface soils of sandy clay in a depression (clay-zone) and of loamy sand underlain by a dense profile on the terraces (sand-zone). The clay-zone had a wetter profile due to extra water supply through subsurface lateral flow from the adjoining, topographically higher, sand-zone. In the clay-zone, the differences between the two tree species in their hydraulic attributes were large and rates of water use were widely divergent. Rates of transpiration per unit land area (Ec) and canopy conductance of E. camaldulensis that was dominant in the clay-zone were about 50% lower than those for E. microcarpa in the same zone. This was in marked contrast to the behavior of trees growing in the sand-zone where water availability was persistently low and variations in sapwood density, sapwood area and canopy conductance were narrow. This resulted in almost identical rates of water use for the two species in the sand-zone, despite E. microcarpa dominating the stand. Contrary to many previous studies, sapwood density was positively correlated with Ec in these eucalypt species, while the proportion of trunk area assigned to sapwood declined with sapwood density. Consequently in this low rainfall environment, with prolonged dry seasons, dense sapwood safeguards against turgor loss, and possibly xylem embolism, thereby allowing Ec to be sustained under extremely low soil-water availability. We concluded that variation in hydraulic traits is less likely where trees are under persistent water-stress than where the stress is short and relatively mild.We developed single functions for predicting Ec for the two species by integrating their responses to micrometeorological and soil-water conditions.
Original languageEnglish
Pages (from-to)1234-1244
Number of pages11
JournalAgricultural and Forest Meteorology
Volume150
Issue number9
DOIs
Publication statusPublished - 2010

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sapwood
transpiration
Eucalyptus
rain
rainfall
sand
clay
Eucalyptus camaldulensis
leaf area index
fluid mechanics
water availability
sandy clay soils
canopy
water use
soil water
embolism
water
plant available water
terraces
turgor

Cite this

Yunusa, Isa A.M. ; Aumann, Colin D. ; Rab, M.A. ; Merrick, Noel ; Fisher, Peter D. ; Eberbach, Philip ; Eamus, Derek. / Topographical and seasonal trends in transpiration by two co-occurring Eucalyptus species during two contrasting years in a low rainfall environment. In: Agricultural and Forest Meteorology. 2010 ; Vol. 150, No. 9. pp. 1234-1244.
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abstract = "Understanding the strategies that confer resilience on natural woodlands in drought prone environments is important for the conservation of these and similar ecosystems. Our main aim in this 2-year study was to assess traits (sapwood area, sapwood density and leaf area index) that control transpiration in Eucalyptus camaldulensis and E. microcarpa in a natural forest in which topographical variation created surface soils of sandy clay in a depression (clay-zone) and of loamy sand underlain by a dense profile on the terraces (sand-zone). The clay-zone had a wetter profile due to extra water supply through subsurface lateral flow from the adjoining, topographically higher, sand-zone. In the clay-zone, the differences between the two tree species in their hydraulic attributes were large and rates of water use were widely divergent. Rates of transpiration per unit land area (Ec) and canopy conductance of E. camaldulensis that was dominant in the clay-zone were about 50{\%} lower than those for E. microcarpa in the same zone. This was in marked contrast to the behavior of trees growing in the sand-zone where water availability was persistently low and variations in sapwood density, sapwood area and canopy conductance were narrow. This resulted in almost identical rates of water use for the two species in the sand-zone, despite E. microcarpa dominating the stand. Contrary to many previous studies, sapwood density was positively correlated with Ec in these eucalypt species, while the proportion of trunk area assigned to sapwood declined with sapwood density. Consequently in this low rainfall environment, with prolonged dry seasons, dense sapwood safeguards against turgor loss, and possibly xylem embolism, thereby allowing Ec to be sustained under extremely low soil-water availability. We concluded that variation in hydraulic traits is less likely where trees are under persistent water-stress than where the stress is short and relatively mild.We developed single functions for predicting Ec for the two species by integrating their responses to micrometeorological and soil-water conditions.",
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Topographical and seasonal trends in transpiration by two co-occurring Eucalyptus species during two contrasting years in a low rainfall environment. / Yunusa, Isa A.M.; Aumann, Colin D.; Rab, M.A.; Merrick, Noel; Fisher, Peter D.; Eberbach, Philip; Eamus, Derek.

In: Agricultural and Forest Meteorology, Vol. 150, No. 9, 2010, p. 1234-1244.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Topographical and seasonal trends in transpiration by two co-occurring Eucalyptus species during two contrasting years in a low rainfall environment

AU - Yunusa, Isa A.M.

AU - Aumann, Colin D.

AU - Rab, M.A.

AU - Merrick, Noel

AU - Fisher, Peter D.

AU - Eberbach, Philip

AU - Eamus, Derek

N1 - Imported on 12 Apr 2017 - DigiTool details were: Journal title (773t) = Agricultural and Forest Meteorology. ISSNs: 0168-1923;

PY - 2010

Y1 - 2010

N2 - Understanding the strategies that confer resilience on natural woodlands in drought prone environments is important for the conservation of these and similar ecosystems. Our main aim in this 2-year study was to assess traits (sapwood area, sapwood density and leaf area index) that control transpiration in Eucalyptus camaldulensis and E. microcarpa in a natural forest in which topographical variation created surface soils of sandy clay in a depression (clay-zone) and of loamy sand underlain by a dense profile on the terraces (sand-zone). The clay-zone had a wetter profile due to extra water supply through subsurface lateral flow from the adjoining, topographically higher, sand-zone. In the clay-zone, the differences between the two tree species in their hydraulic attributes were large and rates of water use were widely divergent. Rates of transpiration per unit land area (Ec) and canopy conductance of E. camaldulensis that was dominant in the clay-zone were about 50% lower than those for E. microcarpa in the same zone. This was in marked contrast to the behavior of trees growing in the sand-zone where water availability was persistently low and variations in sapwood density, sapwood area and canopy conductance were narrow. This resulted in almost identical rates of water use for the two species in the sand-zone, despite E. microcarpa dominating the stand. Contrary to many previous studies, sapwood density was positively correlated with Ec in these eucalypt species, while the proportion of trunk area assigned to sapwood declined with sapwood density. Consequently in this low rainfall environment, with prolonged dry seasons, dense sapwood safeguards against turgor loss, and possibly xylem embolism, thereby allowing Ec to be sustained under extremely low soil-water availability. We concluded that variation in hydraulic traits is less likely where trees are under persistent water-stress than where the stress is short and relatively mild.We developed single functions for predicting Ec for the two species by integrating their responses to micrometeorological and soil-water conditions.

AB - Understanding the strategies that confer resilience on natural woodlands in drought prone environments is important for the conservation of these and similar ecosystems. Our main aim in this 2-year study was to assess traits (sapwood area, sapwood density and leaf area index) that control transpiration in Eucalyptus camaldulensis and E. microcarpa in a natural forest in which topographical variation created surface soils of sandy clay in a depression (clay-zone) and of loamy sand underlain by a dense profile on the terraces (sand-zone). The clay-zone had a wetter profile due to extra water supply through subsurface lateral flow from the adjoining, topographically higher, sand-zone. In the clay-zone, the differences between the two tree species in their hydraulic attributes were large and rates of water use were widely divergent. Rates of transpiration per unit land area (Ec) and canopy conductance of E. camaldulensis that was dominant in the clay-zone were about 50% lower than those for E. microcarpa in the same zone. This was in marked contrast to the behavior of trees growing in the sand-zone where water availability was persistently low and variations in sapwood density, sapwood area and canopy conductance were narrow. This resulted in almost identical rates of water use for the two species in the sand-zone, despite E. microcarpa dominating the stand. Contrary to many previous studies, sapwood density was positively correlated with Ec in these eucalypt species, while the proportion of trunk area assigned to sapwood declined with sapwood density. Consequently in this low rainfall environment, with prolonged dry seasons, dense sapwood safeguards against turgor loss, and possibly xylem embolism, thereby allowing Ec to be sustained under extremely low soil-water availability. We concluded that variation in hydraulic traits is less likely where trees are under persistent water-stress than where the stress is short and relatively mild.We developed single functions for predicting Ec for the two species by integrating their responses to micrometeorological and soil-water conditions.

U2 - 10.1016/j.agrformet.2010.05.007

DO - 10.1016/j.agrformet.2010.05.007

M3 - Article

VL - 150

SP - 1234

EP - 1244

JO - Agricultural Meteorology

JF - Agricultural Meteorology

SN - 0168-1923

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