LTREB: The Population and Community Dynamics of Desert Winter Annuals

University Of Arizona, Tucson AZ

Investigators

Abstract

0212782 Venable This LTREB proposal is to extend the continuous record of population and community dynamics of desert winter annual plants on permanent plots at a Sonoran Desert site at the Desert Laboratory near Tucson, AZ, USA. It will clarify and extend the understanding of demographic variation and covariation and its role in population and community processes. Data on germination, survival and reproduction of desert annual plants will be continuously monitored on long-term plots established from 10 to 19 years ago at locations both under shrub canopies and in the open at this field station. Delayed germination and between year seed carry over are thought to be important for the persistence of desert annuals, so the magnitude of the soil seed reserves will be monitored and determine what fraction germinate in each year for each species under shrubs and in the open. Seeds will be separated from standardized soil samples and tested for viability. The results of this research will be analyzed together with weather data to determine how climatic variation determines population variation for these annual plant species. The investigators 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 the face of environmental variation. They will also be used to investigate how life history differences among species promote their coexistence and species diversity. Desert annual plants have played an important role as model organisms in the development of our understanding of how organisms adapt to variable and unpredictable environments. They have also been used to exemplify ideas about non-equilibrium community dynamics in variable environments. Yet their dynamics are not well known empirically, especially the behavior of seeds. 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 evolutionary ecology, population ecology and community ecology of this system. Such combinations of theoretical and experimental work with long-term observations are proving to be a powerful approach to yield new insights and syntheses in plant ecology. This research will further the goal of combining research and education by virtue of occurring in the academic environment of a major research university. Graduate and undergraduate students will be involved in capacities that fosters hands-on training and research experience that complements formal coursework. Ph.D., Masters, and undergraduate honors projects will be facilitated as part of or offshoots of this research. REU support will be sought for related undergraduate projects. In the first phase of this research more than half of the undergraduate and graduate participants in this project were women and an attempt will be made to include a high percentage of women in the proposed research. The PI will endeavor to include underrepresented ethnic and cultural groups in this research by working with minority access programs on campus.