Climatic effects on soil organic phosphorus in the North American Great Plains identified by phosphorus-31 nuclear magnetic resonance

Considering the influence of the climate is important in studying the dynam ics of P in soils. In this study, we investigated the effect of climate on the composition of organic P in uncultivated soils of the North American pr airie. We present P-31 nuclear magnetic resonance (NMR) spectra of alkaline extracts of bulk samples and clay fractions along gradients of mean annual temperature (MAT) and mean annual precipitation (MAP) across the Great Pla ins. Orthophosphate monoesters (monoester-P) accounted for 32 to 71% and or thophosphate diesters (diester-P) for 7 to 40% of the total signal intensit y. Compared with bulk soils, diester-P structures were enriched in the clay fractions (P < 0.01). In contrast, monoester-P structures were enriched in particle-size classes coarser than day (P < 0.05). As MAT increased, the p roportion of diester-P increased, whereas that of monoester-P decreased. Th ese statistically significant correlations were more pronounced for both di ester P (r = 0.91) and monoester-P (r = -0.87) in the clay fractions than i n the bulk soils. As MAP increased, the proportions of diester-P also incre ased at the expense of monoester-P, This correlation was more significant f or bulk soils (r = 0.70 for diester-P and r = -0.47 for monoester-P) than f or the clay fractions. We believe that temperature and precipitation strong ly influence the organic P in North American grassland soils through their influence on microbial activity and plant production.