Robert G. Qualls1, Scott D. Bridgham2, and Julianne Lilienfein1. (1) University of Nevada, MS 370, Reno, NV 89557, (2) University of Oregon, Center for Ecology and Evolutionary Biology, Eugene, OR 97403
During the process of soil development weathering may affect the tendency of dissolved organic matter in soils to be adsorbed and for solid phase C to become stabilized. We use this chronosequence formed from sand dunes as an extreme example of ecosystem development where the parent material results in very limited potential to develop the metal oxides and clays that affect the retention of dissolved organic matter and have been implicated in the stabilization of solid organic matter. Our objectives were to compare measure the development of properties that may control the adsorption capacity for dissolved organic matter and stabilization of solid soil organic matter during soil development. Oxalate extractable Al oxyhydroxides increased with the age of the soils with nearly all the increase being pyrophosphate extractable Al (often assumed to be organically bound). This pattern suggests weathering is important in producing Al oxyhydroxides in the dunes soils but they are quickly “saturated” with organic matter. Crystalline Fe was present in parent material. Oxalate extractable Fe showed no consistent pattern with age and was mostly in the form of pyrophosphate extractable Fe. Litterfall, organic C and N stocks increased to near a maximum in the 1st 400 yr of soil development and then increased only about 15% over the subsequent centuries. Despite the increases in Al oxyhydroxides and an increase in clay and silt there was not a consistent increase in the percentage of C bound to heavy (dense) particles. However, except for the 0-10 cm depth, over half of the organic C was bound to heavy particles.
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