Increased survival rate of Quercus aliena var. Acuteserrata seedlings via nitrogen addition for the succession of pine and pine-oak mixed forests to oak forest

Abstract

Forest regeneration mechanisms of Pinus tabulaeformis, Pinus armandii, and Quercus aliena var. acuteserrata as the constructive species have been the focus of ecologists and silviculturists, and research to better understand the future of forest community composition, succession patterns, and other aspects of far-reaching influence. However, the influence of nitrogen deposition on the regeneration of different succession stages needs further investigation. In this study, seedlings of the three species of different ages were planted in the pine, pine-oak mixed, and oak forests, and the seedlings which planted by the pot culture with natural soil or fertilization soil, were monitored for two years. Survival and growth indicators, chlorophyll content, and foliar nutritional status of the seedlings were measured. The survival rate and chlorophyll content of P. tabulaeformis, P. armandii, and Q. aliena var. acuteserrata seedlings were the lowest in the oak forest, which might be related to the availability of light in the undergrowth at different stages of succession. Regardless of the forest type, after nitrogen addition, the survival rates of P. tabulaeformis and Q. aliena var. acuteserrata seedlings were the highest for 4-year-old seedlings, and the survival rate of P. armandii seedlings was the highest for 10-year-old ones. Nitrogen addition had no significant effect on the survival rate of P. tabulaeformis and P. armandii seedlings, but changed the nutrient content in their leaves. However, the addition of nitrogen improved the survival rate of Q. aliena var. acuteserrata seedlings, and their competitiveness. Therefore, it can be inferred that nitrogen deposition may promote the succession of P. tabulaeformis forest- to oak forest-in the Qinling Mountains, China.