LTREB: The Population and Community Dynamics of Desert Winter Annuals

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0212782VenableThis LTREB proposal is to extend the continuous record of population and community dynamicsof desert winter annual plants on permanent plots at a Sonoran Desert site at the DesertLaboratory near Tucson, AZ, USA. It will clarify and extend the understanding of demographicvariation and covariation and its role in population and community processes. Data ongermination, survival and reproduction of desert annual plants will be continuously monitored onlong-term plots established from 10 to 19 years ago at locations both under shrub canopies and inthe open at this field station. Delayed germination and between year seed carry over are thoughtto be important for the persistence of desert annuals, so the magnitude of the soil seed reserveswill be monitored and determine what fraction germinate in each year for each species undershrubs and in the open. Seeds will be separated from standardized soil samples and tested forviability. The results of this research will be analyzed together with weather data to determinehow climatic variation determines population variation for these annual plant species. Theinvestigators will then construct population and community models of this desert annual system.These models will be used to explore the role of soil seed banks in buffering populations in theface of environmental variation. They will also be used to investigate how life historydifferences among species promote their coexistence and species diversity.Desert annual plants have played an important role as model organisms in the development of ourunderstanding of how organisms adapt to variable and unpredictable environments. They havealso been used to exemplify ideas about non-equilibrium community dynamics in variableenvironments. Yet their dynamics are not well known empirically, especially the behavior ofseeds. This project will provide the best available long-term data for evaluating these ideas.There has been considerable theoretical and experimental work carried out on the evolutionaryecology, population ecology and community ecology of this system. Such combinations oftheoretical and experimental work with long-term observations are proving to be a powerfulapproach to yield new insights and syntheses in plant ecology.This research will further the goal of combining research and education by virtue of occurring inthe academic environment of a major research university. Graduate and undergraduate studentswill be involved in capacities that fosters hands-on training and research experience thatcomplements formal coursework. Ph.D., Masters, and undergraduate honors projects will befacilitated as part of or offshoots of this research. REU support will be sought for relatedundergraduate projects. In the first phase of this research more than half of the undergraduateand graduate participants in this project were women and an attempt will be made to include ahigh percentage of women in the proposed research. The PI will endeavor to includeunderrepresented ethnic and cultural groups in this research by working with minority accessprograms on campus.