Fertilization effects on the ecohydrology of a southern California annual grassland

Nitrogen limits leaf gas exchange, canopy development, and evapotranspiration in many ecosystems. In dryland ecosystems, it is unclear whether increased anthropogenic nitrogen inputs alter the widely recognized dominance of water and energy constraints on ecohydrology. We use observations from a fac...

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Bibliographic Details
Published in:Geophysical research letters 2012-04, Vol.39 (8), p.n/a
Main Authors: Parolari, A. J., Goulden, M. L., Bras, R. L.
Format: Article
Language:English
Subjects:
Anthropogenic factors
Arid zones
Canopies
Climate change
Earth
Earth sciences
Earth, ocean, space
ecohydrology
Ecosystems
Evapotranspiration
Exact sciences and technology
Gas exchange
Geobiology
Grasslands
Growing season
Hydrology
Leaves
Nitrogen
Soil moisture
Stomatal conductance
Transpiration
Water vapor
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Summary:Nitrogen limits leaf gas exchange, canopy development, and evapotranspiration in many ecosystems. In dryland ecosystems, it is unclear whether increased anthropogenic nitrogen inputs alter the widely recognized dominance of water and energy constraints on ecohydrology. We use observations from a factorial irrigation and fertilization experiment in a nitrogen‐limited southern California annual grassland to explore this hypothesis. Our analysis shows growing season soil moisture and canopy‐scale water vapor conductance are equivalent in control and fertilized plots. This consistency arises as fertilization‐induced increases in leaf area index (LAI) are offset by reduced leaf area‐based stomatal conductance,gs. We interpret this as evidence of a hydraulic feedback between LAI, plant water status, and gs, not commonly implemented in evapotranspiration models. These results support the notion that canopy physiology and structure are coordinated in water‐limited ecosystems to maintain a transpiration flux tightly controlled by hydraulic constraints in the soil‐vegetation‐atmosphere pathway. Key Points Fertilization modulates canopy properties, but does not alter the water balance Increased LAI in fertilized plots was offset by decreased leaf conductance Soil‐plant‐atmosphere hydraulic constraints may explain this feedback
ISSN:0094-8276
1944-8007
DOI:10.1029/2012GL051411