Scott D. Bridgham

Soluble Organic Nutrient Dynamics in Terrestrial Ecosystems during Primary Succession
           

“Retention of Soluble Organic Nutrients in Ecosystems during Primary Succession and Soil Development” (National Science Foundation, University of Nevada, Reno prime contractor), $225,685, Oct. 1999 – Sept. 2002.

Principal Investigators:  Robert G. Qualls (University of Nevada), Scott D. Bridgham (University of Oregon), Scott W. Tyler (University of Nevada), and Wally W. Miller (University of Nevada)

Postdoctoral Associate:  Juliane Lilienfein

Technicians:  Ryan Murray, Jon Loftus (Notre Dame)

Grant Summary

             Much of the emphasis on the cycling and leaching of nutrients after disturbance and during succession has been focused on inorganic nutrients.  Soluble organic nutrients are also released, however, as vegetation grows, dies, and decomposes. The mechanisms by which these potentially soluble inorganic nutrients are retained during succession are generally well known and illustrated in many studies. These mechanisms may not necessarily be similar for soluble organic nutrients.  The factors which control the leaching of organic nutrients, have not been extensively investigated. We examined the role of leaching of soluble organic nutrients in ecosystem development during primary succession in two classical examples of primary successional chronosequences, which we visualized as representing two end members of a triangular series of sites with respect to the retention of potentially soluble organic nutrients (see figure below).  We visualized geochemical and hydrological controls dominating the tendency of an ecosystem to retain soluble organic nutrients produced by biological processes.  Geochemical processes controlling retention are dominated by the presence or absence of Fe and Al oxyhydroxides or certain clays.  The parent material of one end member of this sequence was represented by sand dunes and other sandy soils such as the Indiana Dunes. Another end member was represented by volcanic soils such as occur at the Mt. Shasta mudflows chronosequence and other soils high in oxyhydroxides, allophane, and imogolite which strongly adsorb humic substances.

             Our objectives were:  (1) to develop a strong conceptual framework to explain the production and retention of soluble organic nutrients in ecosystems and compare this with inorganic nutrients, (2) to evaluate whether the leaching of organically bound nutrients is significant in determining the rate of accretion of ecosystem nutrient stocks during primary succession and pedogenesis, (3) to compare the controls on leaching rates in ecosystems developing on two initial substrates which differ radically in adsorption of dissolved organic nutrients, (4) to define the how the development of the ecosystem changes the tendency of the soil to retain these organic nutrients, and finally (5) to define the mechanisms controlling production and adsorption of soluble organic nutrients and compare them to those controlling inorganic nutrients.

            See my curriculum vitae for publications associated with this project.

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