Ecohydrological controls on grass and shrub above‐ground net primary productivity in a seasonally dry climate

Journal Article · Wed Feb 11 00:00:00 EST 2015 · Ecohydrology

DOI:https://doi.org/10.1002/eco.1605· OSTI ID:1401836

Parolari, Anthony J. ^[1]; Goulden, Michael L. ^[2]; Bras, Rafael L. ^[3]

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1. Nicholas School of the Environment Duke University Durham NC USA, Department of Civil and Environmental Engineering Massachusetts Institute of Technology Cambridge MA USA
2. Department of Earth System Science University of California Irvine CA USA
3. School of Civil and Environmental Engineering Georgia Institute of Technology Atlanta GA USA, School of Earth and Atmospheric Sciences Georgia Institute of Technology Atlanta GA USA

Abstract

Seasonally dry, water‐limited regions are often co‐dominated by distinct herbaceous and woody plant communities with contrasting ecohydrological properties. We investigated the shape of the above‐ground net primary productivity (ANPP) response to annual precipitation ( P _a ) for adjacent grassland and shrubland ecosystems in Southern California, with the goal of understanding the role of these ecohydrological properties on ecosystem function. Our synthesis of observations and modelling demonstrates grassland and shrubland exhibit distinct ANPP‐ P _a responses that correspond with characteristics of the long‐term P _a distribution and mean water balance fluxes. For annual grassland, no ANPP occurs below a ‘precipitation compensation point,’ where bare soil evaporation dominates the water balance, and ANPP saturates above the P _a where deep percolation and runoff contribute to the modelled water balance. For shrubs, ANPP increases at a lower and relatively constant rate across the P _a gradient, while deep percolation and runoff account for a smaller fraction of the modelled water balance. We identify precipitation seasonality, root depth, and water stress sensitivity as the main ecosystem properties controlling these responses. Observed ANPP‐ P _a responses correspond to notably different patterns of rain‐use efficiency (RUE). Grass RUE exceeds shrub RUE over a wide range of typical P _a values, whereas grasses and shrubs achieve a similar RUE in particularly dry or wet years. Inter‐annual precipitation variability, and the concomitant effect on ANPP, plays a critical role in maintaining the balance of grass and shrub cover and ecosystem‐scale productivity across this landscape. Copyright © 2015 John Wiley & Sons, Ltd.

• Sponsoring Organization: USDOE
• Grant/Contract Number: FG02-05ER64021
• OSTI ID: 1401836
• Journal Information: Ecohydrology, Journal Name: Ecohydrology Journal Issue: 8 Vol. 8; ISSN 1936-0584
• Publisher: Wiley Blackwell (John Wiley & Sons)
• Country of Publication: United Kingdom
• Language: English