Climatic Effects on Soil Organic Phosphorus in the North American Great Plains Identified by Phosphorus‐31 Nuclear Magnetic Resonance

Abstract

AbstractConsidering the influence of the climate is important in studying the dynamics 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 prairie. We present 31P 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 Plains. Orthophosphate monoesters (monoester‐P) accounted for 32 to 71% and orthophosphate diesters (diester‐P) for 7 to 40% of the total signal intensity. 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 clay (P < 0.05). As MAT increased, the proportion of diester‐P increased, whereas that of monoester‐P decreased. These statistically significant correlations were more pronounced for both diester‐P (r = 0.91) and monoester‐P (r = −0.87) in the clay fractions than in the bulk soils. As MAP increased, the proportions of diester‐P also increased at the expense of monoester‐P. This correlation was more significant for bulk soils (r = 0.70 for diester‐P and r = −0.47 for monoester‐P) than for the clay fractions. We believe that temperature and precipitation strongly influence the organic P in North American grassland soils through their influence on microbial activity and plant production.