102166 Phosphorus Speciation Evolution Across a Climate Gradient in Semi-Arid Prairie Soils.

Poster Number 467-322

See more from this Division: SSSA Division: Soil Chemistry
See more from this Session: Soil Chemistry Poster

Wednesday, November 9, 2016
Phoenix Convention Center North, Exhibit Hall CDE

Chunhao Gu, dept. 3354, 1000 E. University Ave, University of Wyoming, Laramie, WY, Sarah E. Evans, Kellogg Biological Station and Department of Integrative Biology, Michigan State University, East Lansing, MI, Ingrid C. Burke, Haub School of Environment and Natural Resources, Department of Botany, Department of Ecosystem Science and Management, and Program in Ecology, University of Wyoming, Laramie, WY and Mengqiang Zhu, Department of Ecosystem Science and Management, University of Wyoming, Laramie, WY
Abstract:
Climate factors (precipitation and temperature) affect P speciation and thus bioavailability in soils. A few studies addressed how P speciation changes across climate gradients based on sequential chemical extraction method, but the conclusions are inconsistent. Here, we used the modified Hedley chemical sequential extraction (CSE) and P K-edge X-ray absorption near-edge structure (XANES) spectroscopy to characterize soil P speciation changes in surface soils (0 – 10 cm) across a climate gradient located in Inner Mongolia, China with mean annual temperature (MAT) of 0.78 - 5.08 oC and mean annual precipitation (MAP) of 161 - 370 mm. Results show that the total P along the transect ranged from 179 to 436 mg/kg with no correlation with either  MAP or MAT. CSE results show that the percentage of the extracted organic P and Ca-P are 6.6 - 32.4% and 17.2 - 42.3%, respectively. XANES results show that the organic P, Ca-P, Al-P, and Fe-P fractions accounted for 28 - 52%, 16 - 34%, 3 - 44%, and 0 - 25%, respectively. The Ca-P proportions from both methods were comparable, but the organic P proportions from the XANES analysis were much higher than those from the CSE. The difference is caused by that a large proportion of organic P was not extracted and remained in the residuals, which is confirmed by the XANES analysis on the residuals showing that up to 65% organic P in the residuals with the rest being Fe-P. A Pearson correlation analysis between the proportions of the XANES-derived P speciation and the MAT/MAP show that both Al-P and Fe-P fractions were negatively correlated to MAP and MAT while the organic P fraction has a positive correlation with MAP and MAT. Correlations between the Ca-P fraction with MAP or MAT were not observed. The ongoing solution 31P NMR spectroscopic analysis will provide further information on the interaction between each P species and the climate factors. This work provides insights into how climate affects soil P cycling.

See more from this Division: SSSA Division: Soil Chemistry
See more from this Session: Soil Chemistry Poster