Effect of simulated nitrogen deposition on litter decomposition in a Bambusa pervariabilis ×Dendrocala mopsi plantation, Rainy Area of West China
模拟氮沉降对华西雨屏区撑绿 杂交竹凋落物分解的影响

The human activities have substantially altered the nitrogen (N) cycle, and have greatly accelerated the formation and deposition of reactive N. The N cycle alteration has strongly affected the cycles of many other elements, especially the carbon (C) as well. The response of plant growth to N deposition is generally positive in forest ecosystems. However, total C storage of ecosystem depends on the balance between production and decomposition, both of which are affected by projected increase of N deposition. Thus the uncertainty regarding the decomposition response of litter to N deposition has often limited the evaluation of C balance response in ecosystem. Most studies regarding the effects of N deposition on litter decomposition have been conducted in coniferous forests. Bamboo forests are an important forest in the world, but to our knowledge, there has not yet been a study of the effect of N deposition on litter decomposition in bamboo ecosystems. Furthermore, bamboo forests/ plantations are mainly distributed in the southern provinces of China where there is considerable atmospheric N deposition. Therefore, understanding the effect of increasing N deposition on litter decomposition is critical for predicting how the carbon status of bamboo ecosystems will respond to human activities. From January 2008, a two year field experiment of simulated nitrogen deposition has been conducted in a Bambusa pervariabilis × Dendrocala mopsi plantation, Rainy Area of West China. The levels of simulated N deposition were control (CK, 0 g · m-2 · a-1), low N (5 g · m-2 · a-1), medium N (15 g · m-2 · a-1) and high N (30 g · m-2 · a-1). A field experiment using the litterbag method was conducted on the decomposition of leaf litter and sheath litter of B. pervariabilis × D. mopsi. In the end of each month, NH4NO3 was added into N-treated plots. The T95% (the time of 95% mass loss) of leaf litter and sheath litter were 2.9 and 1.5 years, respectively. Simulated nitrogen deposition significantly slowed the decomposition of leaf litter through inhibiting the decomposition of lignin and cellulose. In the later stages of decomposition of leaf litter, the ash-free mass remaining in control was significantly lower than those in the three nitrogen treatments. However, there was no significant effect of different N application on decomposition of sheath litter. This study suggests that continuous nitrogen deposition may increase the soil carbon storage through inhibiting the decomposition of leaf litter, and conserving more stable organic matter in the soil in the bamboo plantation ecosystem.