Phytolith-occluded organic carbon (PhytOC) in the soils is an important long-term carbon pool in terrestrial and plays an important role in regulation of global carbon cycle and mitigation of global climate warming. Intensive management technique including winter mulching has been widely used in the cultivation area of Phyllostachys praecox in the subtropical regions of China. The decomposition of mulching materials with high silicon content (bamboo leaves and rice straw) provides large amounts of silicon for Phyllostachys praecox ecosystem, thus affecting the formation of PhytOC in the ecosystem. To ascertain decomposition rate of mulching materials and silicon dynamic change of mulching residue on the land of Phyllostachys praecox stand, a decomposition experiment of mulching materials was conducted in the main typical production area of Phyllostachys praecox of Lin'an city, Zhejiang province by using decomposition tube method. The experiment results showed that the decomposition of rice straw and bamboo leaves mainly occurred between March and October.
The decomposition peak of rice straw and bamboo leaves happened in July and August and the decomposition rates were 16.3% and 19.1%, respectively. The decomposition half-life of rice straw and bamboo leaves was 228 d and 166 d, respectively. Rice straw and bamboo leaves were decomposed by 67.5% and 79.3% during one year decay, respectively. During one-year decomposition process, C contents in rice straw and bamboo leaves decreased with time,whereas N contents in those increased with time. Carbon contents in bamboo leaves and rice straw and were decreased by 14.8% and 15.3%, respectively. Nitrogen contents in bamboo leaves and rice straw were increased by 15.8 and 174.4%, respectively. The ratios of C/N in bamboo leaves and rice straw were a decrease tendency with time. Decline ranges of the C/N ratios in bamboo leaves and rice straw were 26.4% and 67.5%, respectively. During the experiment period, Si contents in the mulching residues of rice straw and bamboo leaves increased with time. The maximum Si contents in the mulching residues occurred in December. Silicon contents in the mulching residues of rice straw and bamboo leaves were 81.8g/kg and 80.0 g/kg at the end of the experiment, respectively, which were 3.9 and 3.1 times greater than before the decomposition. The contents of Al and Fe in the mulching residues of rice straw and bamboo leaves increased with time. The contents of Al and Fe in the mulching residues of rice straw and bamboo leaves ranged 0.2-8.4 g/kg and 0.3-5.4 g/kg, respectively. The changes trends of P contents in the mulching residues of rice straw and bamboo leaves were the two-peaked curves. The P content in the mulching residues of rice straw ranged from 0.7 g/kg to 1.4 g/kg. The P contents in the mulching residues of bamboo leaves ranged from 1.0 g/kg to 1.7 g/kg. Silicon contents in the mulching residues of rice straw and bamboo leaves was positively correlated with Al or Fe contents (P < 0.01), but where was no relationship between Si contents and P contents (P > 0.05).