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ARS Home » Pacific West Area » Kimberly, Idaho » Northwest Irrigation and Soils Research » Research » Publications at this Location » Publication #235352
Title: Phosphorus Biogeochemistry Across a Precipitation Gradient in Grasslands of Central North America

Author
item Ippolito, James
item BLECKER, S - COLORADO STATE UNIVERSITY
item FREEMAN, C - COLORADO STATE UNIVERSITY
item MCCULLEY, R - UNIVERSITY OF KENTUCKY
item BLAIR, J - KANSAS STATE UNIVERSITY
item KELLY, E - COLORADO STATE UNIVERSITY

Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/11/2010
Publication Date: 5/14/2010
Citation: Ippolito, J.A., Blecker, S.W., Freeman, C.L., Mcculley, R.L., Blair, J.M., Kelly, E.F. 2010. Phosphorus Biogeochemistry Across a Precipitation Gradient in Grasslands of Central North America. Journal of Arid Environments. 74:954-961.

Interpretive Summary: Ecosystem phosphorus is derived primarily from the weathering of parent material. As soils weather, phosphorus can be incorporated into secondary mineral precipitates, assimilated into biomass, or lost via leaching and erosion. We assessed transformations between phosphorus pools across four sites spanning three grassland communities (shortgrass steppe, mixed grass prairie, and tallgrass prairie) along a 400-mm precipitation gradient across the central Great Plains. Total elemental and constituent mass balance analyses reflected a pattern of increased chemical weathering from the more arid shortgrass steppe to the more mesic tallgrass prairie. Soil phosphorus accumulation found in the surface soil horizons was likely related to increased biocycling and biological mining of material from deeper in the soil profile. Surface soil horizons also contained evidence of calcium-bound phosphorus in the absence of calcium carbonate, while in subsurface horizons the calcium-bound phosphorus was associated with increasing calcium carbonate content. Thus, calcium-bound phosphorus formed under different sets of soil chemical conditions in different climatic regimes, demonstrating the importance of carbonate regulation of phosphorus in semi-arid ecosystems.

Technical Abstract: Ecosystem phosphorus is derived primarily from the weathering of parent material. As soils weather, P can be incorporated into secondary mineral precipitates, assimilated into biomass, or lost via leaching and erosion. The study of soil P transformations and distribution under the water limited conditions that characterize many grasslands may provide further insight into the importance of abiotic and biotic P controls within grass-dominated ecosystems. We assessed transformations between P pools across four sites spanning three grassland communities (shortgrass steppe, mixed grass prairie, and tallgrass prairie) along a 400-mm precipitation gradient across the central Great Plains. Total elemental and constituent mass balance analyses of the pedons reflected a pattern of increased chemical weathering from the more arid shortgrass steppe to the more mesic tallgrass prairie. Soil P accumulation found in the surface A horizons at sites was likely related to increased biocycling and biological mining of material from deeper in the soil profile. Soluble P, a small fraction of total P in surface A horizons, was greatest at the mixed grass sites. The distribution of secondary soil P fractions across the gradient suggested decreasing amounts of Ca-bound P and increasing amounts occluded P with increasing precipitation. Surface A horizons contained evidence of Ca-bound P in the absence of CaCO3, while in subsurface horizons the Ca-bound P was associated with increasing CaCO3 content. Calcium-bound P, which dominates in water limited systems, forms under different sets of soil chemical conditions in different climatic regimes, demonstrating the importance of carbonate regulation of P in semi-arid ecosystems.