This multi-investigator research project will address mechanisms of plant competition and their linkage with the process of competition and plant community development in the Great Basin sagebrush-dominated ecosystem. The research is based on manipulative field studies in replicated plots with extension to a landscape setting. Belowground competition is emphasized in four sets of hypotheses concerning (1) the occurrence, magnitude and significance of water leakage from roots and water transfer between plants -- experiments involving whole-plant gas exchange, soil psychrometry and time-domain reflectometry, stable isotopes, and root anatomy, (2) exploitation of resource-rich patches -- involving microscale root distributions, mycorrhizal dynamics, dual-isotope labeling, and root physiological properties, (3) characteristics of roots associated with competitive ability -- using indicator plant approaches with a broad germplasm resource, and (4) linking competition with plant fitness components such as seed output and seedling establishment -- using plant demographic and competition exclusion approaches. Additionally, a set of predictions extending these concepts to landscape situations will be tested. In all, 22 hypotheses and 4 predictions are posed and these range in scale from individual roots and associated mycorrhizae to community-level phenomena. The research team for this project is excellent and will undoubtedly maintain its pest productivity. Facilities provided by the institution for both field and laboratory positions of the project are first-class. A high level of scientific productivity can be expected to result.
