%0 Journal Article
%K Carbon
%K Climate change
%K Precipitation
%K Water
%K Nitrogen
%K Grassland
%K Avena barbata
%K Bayesian ANOVA
%K Dry periods
%K Phenology
%K Soil type
%A Erika A Sudderth
%A Samuel B St. Clair
%A Sarah A Placella
%A Stéphanie M Swarbreck
%A Cristina Castanha
%A Donald J Herman
%A Marc L Fischer
%A Markus Kleber
%A Erik B Sudderth
%A Margaret S Torn
%A Mary K Firestone
%A Gary L Andersen
%A David D Ackerly
%B Ecosphere
%D 2012
%N 8
%R 10.1890/ES12-00004.1
%T Annual grassland resource pools and fluxes: sensitivity to precipitation and dry periods on two contrasting soils
%V 3
%X <p>In ecosystems throughout the world climate models project increased variability in precipitation patterns that may strongly affect the above- and below-ground processes that control carbon, water, and nutrient cycles. Uncertainty about how plant and soil processes respond to wet and dry periods at different times in the growing season is a barrier to understanding how changing rainfall patterns will affect ecosystem function in annual grasslands. We used mesocosm systems to test the sensitivity to mid- and late-season dry periods of twenty response variables related to nitrogen, carbon, and water cycling in <em>Avena barbata</em> monocultures. We compared the responses of individual variables and of grassland systems under low and high cumulative rain treatments and between two contrasting soil types.</p><p>Analysis of individual response variables demonstrated strong seasonal patterns: most soil and plant resource pools and fluxes changed between mid- and late-season, and many had larger responses to the late-season dry period. Under increasingly variable precipitation regimes, specific resource pools and fluxes such as soil nitrate and ecosystem CO<sub>2</sub> flux may be more strongly affected when dry periods occur later in the growing season. Individual responses variables were also used as state variables in a principal components analysis of changes in grassland functional states between treatments and over time. There were dramatic functional state shifts between the mid- and late-season for both soil types, driven by changes in canopy height, leaf soluble protein, soil nitrate, gross N mineralization, and leaf N. However, we did not find evidence that the functional state of grassland systems was affected by rainfall patterns, indicating that interactions among below- and above-ground processes resulted in system-level resistance to changes in soil moisture. A strong association between plant canopy size and ecosystem functional state suggests that responses of plant phenology and growth to climate change may predict changes in ecosystem function.</p>