Effects of elevated temperature and nitrogen fertilization on nitrogen metabolism and nutrient status of two coniferous species

Abstract

The effects of soil warming and nitrogen (N) fertilization on nitrogen metabolism and nutrient status of Picea asperata Mast. and Pinus tabulaformis Carr. seedlings were studied in this paper. Infrared heaters increased monthly average soil and air temperature by 2.6 and 2.1°C above the ambient, respectively. Ammonium nitrate (NH4NO3) was added in an amount equivalent to an additional 25 g N m−2 a−1. Interestingly, soil warming, N fertilization, and their combination decreased foliar phosphorus (P) and magnesium (Mg) concentration of Picea asperata seedlings, but increased them in Pinus tabulaformis seedlings. Moreover, the combination of warming and N fertilization induced greater increments of amino acid, area-based N concentration and mass-based N concentration, manganese (Mn) and zinc (Zn), and further decreased P and calcium (Ca) concentration in Picea asperata seedlings. However, this phenomenon was not observed in Pinus tabulaformis seedlings. These results indicated that Picea asperata seedlings are more sensitive to the combination of warming and N fertilizer than Pinus tabulaformis seedlings.