Stephen F. Zitzer

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Arid ecosystems, which occupy about 20% of the earth's terrestrial surface area, have been predicted to be one of the most responsive ecosystem types to elevated atmospheric CO2 and associated global climate change. Here we show, using free-air CO2 enrichment (FACE) technology in an intact Mojave Desert ecosystem, that new shoot production of a dominant(More)
We examined soil and vegetation N isotopic composition (δ15N) and soil inorganic N availability in an intact Mojave desert ecosystem to evaluate potential effects of elevated atmospheric CO2 on N cycling. Vegetation from the dominant perennial shrub Larrea tridentata under elevated CO2 was enriched in 15N. Over a 7-month sampling period, Larrea δ15N values(More)
Root nodule development, and seasonal patterns of nodular nitrogenase and hydrogenase activities were determined for 5- to 8-year old black alder (Alnus glutinosa (L.) Gaertn.) and Russian olive (Elaeagnus angustifolia L.) interplanted with black walnut (Juglans nigra L.) on bottomland and upland sites in central Illinois, USA. Black alder produced nodules(More)
Regression equations were developed to predict above-ground biomass, carbon and nitrogen content from stem and canopy dimensions for 10 shrub species common to subtropical thorn parklands of southern Texas. Projected canopy area yielded slightly more precise estimates of biomass and nutrient concentrations than the sum of stem basal diameters at the soil(More)
Nodulation (mean number of nodules per seedling) was 5 times greater for Elaeagnus angustifolia than for Alnus glutinosa overall when seedlings were grown in pots containing either an upland or an alluvial soil from central Illinois, USA. However, the upland Alfisol had 1.3 times greater nodulation capacity for A. glutinosa than for E. angustifolia. The(More)
*Department of Biological Sciences, University of Nevada, Las Vegas, NV 89154-4004, U.S.A. ?Department of Biological Sciences, Rutgers University, Newark, NJ 07102-1811, U.S.A. @Department of Environmental Resource Sciences, University of Nevada, Reno, NV 89557, U.S.A. ADepartment of Biology, California State University, San Bernardino, CA 92407, U.S.A.(More)
Desert annuals are a critically important component of desert communities and may be particularly responsive to increasing atmospheric (CO2 ) because of their high potential growth rates and flexible phenology. During the 10-year life of the Nevada Desert FACE (free-air CO2 enrichment) Facility, we evaluated the productivity, reproductive allocation, and(More)
Numerous studies, including those of desert plants, have shown reduced stomatal conductance under elevated atmospheric CO2. As a consequence, soil water has been postulated to increase. Soil water was measured for .4 yr at the Nevada Desert Free Air CO2 Enrichment (FACE) Facility to determine if elevated atmospheric CO2 conserves soil water for a desert(More)
OBJECTIVES To learn whether managed care patients with Alzheimer's disease (AD) are more or less costly to care for than patients with other forms of dementia or patients without dementia during the last few years of life. DESIGN Case control study. SETTING A health maintenance organization base population. PARTICIPANTS Three groups of subjects (mean(More)