Fig. 3

Principal component analysis (PCA) showing treatment-related patterns in (a) soil chemical properties and (b) phosphorus (P) fractions after long-term N and P fertilization and cessation. Ellipses represent 95% confidence intervals around treatment group centroids. In (a), soil variables (pH, exchangeable Ca and Mg, and total C) are projected as vectors illustrating their contribution to the first two principal components (PC1 and PC2). In (b), P fractions (soluble and loosely bound P, Al–P, Fe–P, reductant–P, and Ca–P) are displayed similarly.