Nicole Grant

University of Technology Sydney

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N. Boulain

University of Technology Sydney

James Cleverly

James Cook University

Derek Eamus

University of Technology Sydney

Randol Villalobos‐Vega

University of Technology Sydney

Ralph Faux

University of Technology Sydney

Qiang Yu

Hubei University

Chao Chen

Beijing Academy of Agricultural and Forestry Sciences

Cameron Wood

Queen's University

Andrea Leigh

University of Technology Sydney

Peter G. Cook

National Centre for Groundwater Research and Training

Cooperative Institutions

University of Technology Sydney

National Centre for Groundwater Research and Training

Flinders University

Terrestrial Ecosystem Research Network

Commonwealth Scientific and Industrial Research Organisation

Institut de Recherche pour le Développement

Centre National de la Recherche Scientifique

Université de Montpellier

Center for Health and Gender Equity

Laboratoire HydroSciences Montpellier

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Dynamics of component carbon fluxes in a semi‐arid Acacia woodland, central Australia

Journal of Geophysical Research Biogeosciences (2013)

James Cleverly N. Boulain Randol Villalobos‐Vega Nicole Grant Ralph Faux

Vast areas in the interior of Australia are exposed to regular but infrequent periods of heavy rainfall, interspersed with long periods at high temperatures, but little is known of the carbon budget of these remote areas or how they respond to extreme precipitation. In this study, we applied three methods to partition net ecosystem photosynthesis into gross primary production (GPP) and ecosystem respiration (R e ) during two years of contrasting rainfall. The first year was wet (>250 mm above average rainfall), while little precipitation fell during the second year (>100 mm below average). During the first year of study, rates of GPP were large (793 g C m −2 yr −1 ) in this semi‐arid Mulga ( Acacia aneura ) and grass savanna due to complementary photosynthetic responses by the canopy and C 4 understorey to cycles of heavy rainfall. Patterns in GPP during the summer and autumn matched those in leaf area index (LAI), photosynthetic activity, and autotrophic respiration. During the dry year, small but positive photosynthetic uptake by Mulga contributed to the neutral carbon budget (GPP / R e = 1.06 ± 0.03). Small rates of photosynthesis by evergreen Mulga when dry were supported by storage of soil moisture above a relatively shallow hardpan. Little soil organic matter (1.1%) was available to support heterotrophic respiration (R h ) without input of fresh substrate. The two largest sources of R e in this study were autotrophic respiration by the seasonal understorey and R h through decomposition of fresh organic matter supplied by the senescent understorey.

Understory

Ecosystem respiration

Soil respiration

10.1002/jgrg.20101

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Citations (111)

Carbon and water fluxes in an arid-zone Acacia savanna woodland: An analyses of seasonal patterns and responses to rainfall events

Agricultural and Forest Meteorology (2013)

Derek Eamus James Cleverly N. Boulain Nicole Grant Ralph Faux

Water Use Efficiency

Carbon sink

Ecosystem respiration

Growing season

10.1016/j.agrformet.2013.04.020

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Citations (139)

Aerodynamic Resistance and Penman–Monteith Evapotranspiration over a Seasonally Two-Layered Canopy in Semiarid Central Australia

Journal of Hydrometeorology (2013)

James Cleverly Chao Chen N. Boulain Randol Villalobos‐Vega Ralph Faux

Abstract Accurate prediction of evapotranspiration E depends upon representative characterization of meteorological conditions in the boundary layer. Drag and bulk transfer coefficient schemes for estimating aerodynamic resistance to vapor transfer were compared over a semiarid natural woodland ecosystem in central Australia. Aerodynamic resistance was overestimated from the drag coefficient, resulting in limited E at intermediate values of vapor pressure deficit. Large vertical humidity gradients were present during the summer, causing divergence between momentum and vapor transport within and above the canopy surface. Because of intermittency in growth of the summer-active, rain-dependent understory and physiological responses of the canopy, leaf resistance varied from less than 50 s m−1 to greater than 106 s m−1, in which the particularly large values were obtained from inversion of drag coefficient resistance. Soil moisture limitations further contributed to divergence between actual and reference E. Unsurprisingly, inclusion of site-specific meteorological (e.g., vertical humidity gradients) and hydrological (e.g., soil moisture content) information improved the accuracy of predicting E when applying Penman–Monteith analysis. These results apply regardless of canopy layering (i.e., even when the understory was not present) wherever atmospheric humidity gradients develop and are thus not restricted to two-layer canopies in semiarid regions.

10.1175/jhm-d-13-080.1

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Citations (24)