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Climate change models envision an increase in summer precipitation in eastern California and adjacent arid regions by 2050, due to anthropogenic activities. Changes in the frequency, intensity and spatial patterns of rainfall pulses are likely to influence seedling recruitment and establishment, and ultimately community composition and dynamics. The effects of altered water availability might be complicated by the effect of adult plants on resources and conditions, potentially altering seedling recruitment success and affecting community succession. We tested the hypotheses that: (1) an experimental pulse representing a 25% increase in summer precipitation would increase photosynthesis for Artemisia tridentata and...
Plant community structure in the southwestern United States co-varies with soil surface characteristics due to their role in controlling water availability. At the University of Arizona Desert Laboratory on Tumamoc Hill, we evaluated winter and summer season dynamics of photosynthesis in a dominant shrub species, Larrea tridentata (creosotebush), across soils with contrasting development of surface and sub-surface horizons. We measured pre-dawn water potential (?pd), stomatal conductance (gs), leaf nitrogen content (%N), and determined stable carbon isotope discrimination (?). There were no differences in these parameters throughout the winter, although ? was higher and %N was lower on the clay than sandy soil early...