Abstract: Litterfall is the link between plant and soil, and the key in nutrient and energy cycling of forest ecosystem. The return of nutrients to forest floor and soil is controlled by the litterfall production and its elements concentration. By the methods of field investigation and laboratory analysis, the characteristics of the litter layers in coniferous forests of western Qinling Mountains, including the amount of litterfall and the content and storage of mineral elements in litter layer, were studied. In the test forests, the existing amount of litterfall varied from 846 to 2981 t·hm-2, and the annual litterfall ranged from 296 to 423 t·hm-2·a-1, indicating that the decomposition rate of the litterfall was relatively low, and the turnover of the nutrients was slow. The nutrient contents in litter layer varied significantly with tree species, but the nutrient storage in the litter layers of different tree species showed the same tendency of un-decomposed layer (U layer) < half-decomposed layer (S layer) < decomposed layer (D layer). The average storage of nutrients in the litter layers under different tree species was 35771 kg·hm-2 of Ca, 17572 kg·hm-2 of N, 10250 kg·hm-2 of Fe, 5421 kg·hm-2 of Mg, 3196 kg·hm-2 of K, and 1678 kg·hm-2 of P. The decomposition of litterfall resulted in the accumulation of mineral nutrients in decomposed layer (D layer), and different tree species and different management practices had greater effects on the properties of litterfall and its decomposition rate. The decomposition rate of litterfall was in the order of spruce forest<pine forest<larch forest.

Key words: FACE, Elevated CO₂, Rice, Xylem exudates, Root activity, Amino acid synthesis