Intensification of the hydrologic cycle is predicted with future climate change, and the consequences for ecosystem carbon cycling is a critical question in predicting ecohydrological feedbacks. We analyzed eddy covariance measurements to understand how interannual and inter-site variability in precipitation affects gross primary production, evapotranspiration, and ecosystem water use efficiency (WUE) across diverse ecosystems. Measurements came from ten California sites and spanned a mean annual temperature range of 5 to 23°C and mean annual precipitation range of 100 to 1400 mm, from Mojave Desert scrub to subalpine lodgepole forest. All ten ecosystems exhibited similar patterns in water use efficiency: ecosystem WUE declined sharply as annual precipitation dropped below 500 mm, and WUE plateaued with annual precipitation greater than 500 mm. Surface evaporation and flexible plant physiology contributed to sensitive WUE with low annual precipitation, while limited surface evaporation and "ecosystem inertia" diminished sensitivity of WUE with high annual precipitation.
Kelly, A.; M. Goulden (2014): Water use efficiency variability and controls across ten California ecosystems. American Geophysical Union, Fall Meeting 2014, abstract #H33L-06.
This Paper/Book acknowledges NSF CZO grant support.