Plant responsiveness to variation in precipitation and nitrogen is consistent across the compositional diversity of a California annual grassland |
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Authors: | Samuel B St Clair Erika A Sudderth Cristina Castanha Margaret S Torn David D Ackerly |
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Institution: | 1. Department of Plant and Wildlife Sciences, Brigham Young University, Provo, UT 84602, USA;2. Department of Integrative Biology, University of California, Berkeley, CA 94720, USA;3. Email sudderth@berkeley.edu;4. Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA;5. Email castanha@nature.berkeley.edu;6. Email mstorn@lbl.gov;7. Email dackerley@berkeley.edu |
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Abstract: | Question: How does responsiveness to water and Nitrogen (N) availability vary across the compositional and functional diversity that exists in a mesic California annual grassland plant community? Location: Northern California annual grassland. Methods: A mesocosm system was used to simulate average annual precipitation totals and dry and wet year extremes observed in northern California mesic grasslands. The effects of precipitation and N availability on biomass and fecundity were measured on three different vegetation types, a mixed grass forb community, and a forb and a grass monoculture. The treatment effects on plant community composition were examined in the mixed species community. Results: While growth and seed production of the three vegetation types was inherently different, their responses to variation in precipitation and N were statistically similar. Plant density, shoot biomass, and seed production tended to increase with greater water availability in all vegetation types, with the exception of a consistent growth reduction in high precipitation (1245 mm) plots in the first year of the study. Shoot biomass responded positively to N addition, an effect that increased with greater water availability. Nitrogen addition had little effect on plant density or seed production. In the mixed grass‐forb community, biomass responsiveness to water and N treatments were consistently driven by the shoot growth of Avena barbata, the dominant grass species. Conclusions: Vegetation responses to changes in precipitation and N availability were consistent across a range of composition and structural diversity in this study. Plant growth and seed production were sensitive to both increased and decreased precipitation totals, and the magnitude of these responses to N availability varied depending on soil moisture conditions. Our results suggest the impacts of changing precipitation regimes and N deposition on annual productivity of California grasslands may be predictable under different climate scenarios across a range of plant communities. |
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Keywords: | Annual grassland Avena Climate change Drought Fecundity Soil moisture Water deficit |
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