Our laboratory maintains a breadth of interests centering on aspects of vascular plant adaptation to environmental water and nutrient stress. Within this context we have focused particularly on the interactions of physiological water stress and nutrient availability in limiting net primary production of arid zone plants. We are looking intensively at the relationship of seasonal changes in morphological, architectural and physiological components of plant form and function in woody desert legumes and evergreen shrubs. Our approaches in these investigations involve analysis of components of tissue water relations, photosynthetic capacity, foliar nutrient levels, leaf morphology and canopy architecture. We are very interested in applications of stable isotope ratios to ecological research studies as a means of developing integrated measurements of physiological response to environmental stress. Such measures will help us link physiological process studies to an ecosystem perspective. In addition to our work on desert ecosystems, my laboratory group maintains interests in several other areas. These include the physiological ecology of plant species in Mediterranean-type and tropical ecosystems, parallel with our desert research. We are also investigating the impact of air pollutants on photosynthetic capacity and productivity of coniferous forest trees in California.