Anthropogenic activities have increased nitrogen (N) and phosphorus (P) inputs to terrestrial ecosystems, which may significantly alter biochemical cycle of nutrients such as nutrient resorption. 1) How did soil nutrient availability effect on different P fractions of different-age leaves? 2) Which P fractions did plants most preferentially resorb in response to soil nutrient availability? We conducted a N and P addition experiment in Chinese fir (Cunninghamia lanceolata) stands using six treatments: +N1 (50 kg N ha−1 year−1), +N2 (100 kg N ha−1 year−1), +P (50 kg P ha−1 year−1), +N1+P, +N2+P and CK (without N and P addition). We measured the concentration of different P fractions (inorganic, nucleic acid, lipid and residual fractions) for live leaves of different ages in the summer and senescent leaves (fresh litter) in the winter.
Results/Conclusions
We also measured soil mineral N and available P concentrations to determine the magnitude of increase due to N and P additions. We found that N addition did not affect the concentration and resorption of different P fractions. P addition increased the concentration of total P, inorganic P, and lipid P fractions, but only promoted the P resorptions of the inorganic and lipid fraction. However, N and P addition decreased the P resorptions of the inorganic and lipid fraction in young leaves. Our results suggest that plants preferentially resorb P from more easily degraded fractions, especially for young leaves. We conclude that P enrichment, when combined with N addition, could strongly influence plant-mediated biogeochemical cycles through altering the resorption of more easily degraded P fractions in the Chinese fir in subtropical China.