Fig. 1 Effects of different land use patterns on TC (a), TN (b), TP (c), C: N ratio (d), C: P ratio (e), and N: P ratio (f). Different letters indicate significant differences among different land use patterns in the same soil layer (p < 0.05). TC: soil total carbon. TN: soil total nitrogen. TP: soil total phosphorus. C: carbon. N: nitrogen. P: phosphorus. AG: alfalfa artificial grassland. WM: wheat-maize rotation field. PC: native grassland.