OOS 48 - Ecohydrology of Shallow Soil Communities and of Roots in Rocks

Friday, August 12, 2011: 8:00 AM-11:30 AM
17B, Austin Convention Center
Organizer: Susan Schwinning
Co-organizers: Georgianne W. Moore , James L. Heilman , Pieter Poot , Michael C. Duniway and Karin T. Rebel
Moderator: Susan Schwinning
Continental scale soil depth maps suggest that a large proportion of the global land area has limited soil depth of 1 m or less. These regions are often underlain by weathered bedrock or cemented horizons that impede water infiltration and root development. Though most hydrologic models assume that these firm horizons do not contribute to ecohydrologic processes, isolated case studies in locations around the world suggest a significant role for fractured bedrock and petrocalcic horizons in plant water availability. Furthermore, vegetation adaptations to soil depth limitations and resulting impacts on hydrological processes have never been systematically explored. This presents new challenges and opportunities for modeling – predicting how these ecosystems will respond to a changing climate will require a mechanistic understanding of water movement, retention and, most critically, how and when plants utilize water from firm, root restrictive horizons. Many of these ecosystems are vulnerable to climate extremes, erosion and pollution, while often contributing disproportionally to regional biodiversity and water yield. The central objective of this symposium is to work towards framing an integrated ecohydrological research agenda for the study of ecosystems with shallow soils for the purpose of improving the management of these plant communities as well as their representation in hydrological models. The spotlight will be on the following themes: 1) assessment of water storage contributions of weathered bedrock/cemented horizons; 2) plant adaptations to soil depth limitations and the use of fractured bedrock or cemented horizons for water uptake; 3) the representation of mixed soil/rock storage substrates and associated plant traits in ecohydrological models. The symposium will begin with a brief introduction summarizing the global extent of shallow soils and the research questions they pose. On the topic of water storage in bedrock and cemented horizons, presentations will span multiple regions across three continents differing markedly in geological and climate characteristics. On the topic of plant adaptations, speakers will focus on identifying the morphological, physiological and ecological requisites for the extraction of rock water by plant roots and their fungal symbionts. Lastly, speakers will present their thoughts on developing hydrological models that best capture the moisture dynamics of regions characterized by shallow soils and firm subsoil substrates. The session will close with a call for audience feedback and a panel discussion to synthesize the information presented and distill common themes suitable for the framing of a unified ecohydrology of shallow soils.
8:00 AM
Subsurface features: Beyond shallow soils in Yucatan
Hector Estrada-Medina, Universidad Autonoma de Yucatan; Robert C. Graham, University of California, Riverside; Michael F. Allen, University of California Riverside; Wes Tuttle, Na onal Soil Survey Center; Louis S. Santiago, University of California-Riverside; Juan José Jimenez-Osornio, Universidad Autonoma de Yucatan
8:20 AM
Shallow soil constraints on ecohydrological processes in limestone karst ecosystems of the Edwards Plateau, TX
James L. Heilman, Texas A&M University; Marcy E. Litvak, University of New Mexico
8:40 AM
Differences in depth to groundwater modulates the mycorrhizal responses of oak trees to interannual rainfall variability
Louise Egerton-Warburton, Chicago Botanic Garden; José Ignacio Querejeta, Centro de Edafologia y Biologia Aplicada del Segura (CEBAS-CSIC); Michael F. Allen, University of California Riverside
9:00 AM
Water relations and ecosystem function of weathered granitic bedrock
Robert C. Graham, University of California, Riverside
9:20 AM
9:40 AM
9:50 AM
Contrasting responses of seedling development to soil barriers in two woody encroachers
Kathleen D. Eggemeyer, Texas State University; Susanne Schwinning, Texas State University
10:10 AM
Ecohydrology of petrocalcic horizons: Water storage, ecological potential, and hydrologic models
Michael C. Duniway, U.S. Geological Survey; Jeffrey E. Herrick, USDA Agricultural Research Service; Curtis Monger, New Mexico State University; Dawn M. Browning, USDA Agricultural Research Service; Keirith Snyder, USDA, Agricultural Research Service; Debra P.C. Peters, USDA Agricultural Research Service
10:30 AM
Modeling shallow-soil communities: Opportunities and Challenges
Karin T. Rebel, Utrecht University; Georgianne W. Moore, Texas A&M University; Susan Schwinning, Texas State University; Rebecca J. Elkington, Utrecht University
10:50 AM
Transpiration: Whether it varies with land-use change or not, and why
Georgianne W. Moore, Texas A&M University; James L. Heilman, Texas A&M University
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