Journal Article

Antecedent moisture and seasonal precipitation influence the response of canopy-scale carbon and water exchange to rainfall pulses in a semi-arid grassland

Mason, M. J., Cable, J. M., Ignace, D. D., Williams, D. G., English, N. B., Eilts, J. A., Huxman, T. E., Weltzin, J. F., Potts, D. L.

2006

Overview

$\\bullet$ The influences of prior monsoon-season drought (PMSD) and the seasonal timing of episodic rainfall ('pulses') on carbon and water exchange in water-limited ecosystems are poorly quantified. $\\bullet$ In the present study, we estimated net ecosystem exchange of CO2 (NEE) and evapotranspiration (ET) before, and for 15 d following, experimental irrigation in a semi-arid grassland during June and August 2003. Rainout shelters near Tucson, Arizona, USA, were positioned on contrasting soils (clay and sand) and planted with native (Heteropogon contortus) or non-native invasive (Eragrostis lehmanniana) C4 bunchgrasses. Plots received increased ('wet') or decreased ('dry') monsoon-season (July-September) rainfall during 2002 and 2003. $\\bullet$ Following a June 2003 39-mm pulse, species treatments had similar NEE and ET dynamics including 15-d integrated NEE ($NEE_{pulse}$). Contrary to predictions, PMSD increased net C uptake during June in plots of both species. Greater flux rates after an August 2003 39-mm pulse reflected biotic activity associated with the North American Monsoon. Furthermore, August $NEE_{pulse}$ and ecosystem pulse-use efficiency ($PUE_{e} = NEE_{pulse}/ET_{pulse}$) was greatest in Heteropogon plots. $\\bullet$ PMSD and rainfall seasonal timing may interact with bunchgrass invasions to alter NEE and ET dynamics with consequences for $PUE_e$ in water-limited ecosystems.

• Publisher: Oxford, UK : Blackwell Publishing Ltd,Blackwell Science,Blackwell Publishing Ltd,Blackwell
• Subject: Animal and plant ecology / Animal, plant and microbial ecology / arid lands / Arizona / Biological and medical sciences / C4 plants / Carbon / Carbon - metabolism / Carbon dioxide / Carbon Dioxide - metabolism / clay soils / Climate / climate change / Data Interpretation, Statistical / drought / Ecosystem / Ecosystems / Eragrostis / Eragrostis - metabolism / Eragrostis lehmanniana / evapotranspiration / Fundamental and applied biological sciences. Psychology / Grassland soils / grasslands / Heteropogon / Heteropogon contortus / indigenous species / invasive species / metabolism / net ecosystem CO2 exchange / Net ecosystem exchange / photosynthesis / physiology / Plant Transpiration / Plant Transpiration - physiology / Poaceae / Poaceae - metabolism / Precipitation / prior monsoon-season drought / Rain / respiration / sandy soils / Santa Rita Experimental Range / seasonal variation / Seasons / Semiarid grasslands / Soil ecology / soil moisture storage / Soil water / soil water storage / Synecology / Terrestrial ecosystems / Water / Water - metabolism / water stress