Eighteen-year nitrogen addition does not increase plant phosphorus demand in a nitrogen-saturated tropical forest

Nitrogen (N) deposition usually increases plant tissue N concentrations and thus phosphorus (P) demand in young and/or N-limited forests, but the N-deposition effect on plant P demand has rarely been assessed in N-saturated forests.
Impacts of 18-year external N additions (Control: 0, Low N: 50, Moderate N:100, and High N: 150 kg N ha-1 yr-1) on leaf P of four plant life-forms (tree, shrub, herb, and liana), P fractions of bulk and rhizosphere soils were examined in a N-saturated mature tropical forest in southern China.
Leaf N, P, and N: P ratios of all plant life-forms remained stable under three N-additions. Among soil P fractions, moderate labile organic P increased by 25-33% across three N-additions; and soil total P was increased by 11.76 % under Low N, and 8.87% under High N, compared with the control. The PLS-PM results showed that the path coefficient of microbial community to available P significantly increased and of inorganic P to available P significantly decreased under ..., ,