Phosphorus cycling and supply–demand balance across a chronosequence of Chinese fir plantations

Abstract

The cycling dynamics and supply–demand balance of nutrients can provide useful information for improving the management of tree plantations and maintaining their long-term productivity. Phosphorus (P) is an essential nutrient for plant growth; however, its cycling characteristics and availability in soils along different stand developmental stages remain unclear, especially in intensively managed plantations. In this study, we examined the stocks, distribution, flux, and supply–demand balance of P across a chronosequence of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.; Taxodiaceae) plantations aged 3, 8–11, 16, 21, 25, 29, and 32 years. <22.18% tree P stock allocated for stem across a chronosequence, suggesting that only stem harvest could return more than three-quarters of tree P stock to soil. The annual P resorption, P return, and P-use efficiency increased with stand age, indicating strong P recycling. Indicators of P acquisition and recycling strategies significantly increased with stand age and promoted P fluxes. The combination of acquisition and recycling strategies might favor the entrainment of P into the biological cycle. With the increase in stand age, the available soil P stocks initially decreased and then increased after 11 years, while the annual P uptake increased at first and then stabilized after 22 years. Based on the best fitted model, the lower soil P supply and higher tree P demand in 9- to 40-year-old plantations revealed that timely and appropriate fertilization could enhance soil P supply and improve stand productivity. This work provides crucial information about the time of fertilization and appropriate harvest methods for the sustainable management of forest P nutrition.