Latitudinal differentiation of phosphorus in black soil in Northeast of China

Based on the region of black soil in Northeast of China, from Nenjiang County in Heilongjiang Province to Changtu County in Liaoning Province, studies were conducted to explore the relationship between the concentration of organic P and organic matter, organic P and total N; the relationship among the concentration of total P, organic P, inorganic P, the P_o/P_i ratio (ratio of organic P to inorganic P), and contribution of latitude. The results show that the relationship between the organic P and organic matter, organic P and total N are both close, their correlation coefficients are 0.90 and 0.92, respectively which indicate highly significant positive correlation (P<0.01). Along latitude, total P, organic P, inorganic P and the P_o/P_i ratio all show obvious differentiation characteristics, namely, the concentrations of total P, organic P, inorganic P and the P_o/P_i ratio all increase gradually with the increase of latitude. Their correlation coefficients 0.68, 0.77, 0.26, 0.60, respectively. The results of correlation analysis show that these latitudinal differentiations all have highly significant positive correlation(P<0.01). Except for the unclear cause of the latitudinal differentiation of inorganic P, the other latitudinal differentiations may be due to the difference of climate and effects of human activities between north and south, which lead to the difference of the mineralization velocity of organic matter.