[Effects of simulated nitrogen and sulfur deposition on litter decomposition rate in an evergreen broad-leaved forest in the Rainy Area of Western China.] / 模拟氮、硫沉降对华西雨屏区常绿阔叶林凋落叶分解速率的影响.

To examine the effects of nitrogen and sulfur deposition on litter decomposition rate, a one-year field experiment was conducted with the litter bag method from April 2013 to April 2014 in an evergreen broad-leaved forest in the Rainy Area of Western China. There were nine treatments with three nitrogen levels and three sulfur levels, including control (CK), low nitrogen deposition (LN, 50 kg N·hm-2·a-1), high nitrogen deposition (HN, 150 kg N·hm-2·a-1), low sulfur deposition (LS, 200 kg S·hm-2·a-1), high sulfur deposition (HS, 400 kg S·hm-2·a-1), low nitrogen and low sulfur deposition (LNLS), high nitrogen and low sulfur deposition (HSLS), low nitrogen and high sulfur deposition (LNHS), and high nitrogen and high sulfur deposition (HNHS). The results showed that the leaf litter residual rate ranged from 57.0% to 70.7% after one year decomposition. The time of half mass loss ranged from 1.47 to 2.08 years, while the time of 95% mass loss ranged from 6.33 to 9.01 years. Nitrogen deposition had no significant effect on litter decomposition rate. The decomposition rate was significantly increased in LS treatment but significan-tly reduced in HS treatment. The rate was significantly affected by LNHS and HNHS, but unaffected by LNLS and HNLS. In addition, simulated nitrogen and sulfur deposition interacted to affect litter decomposition rate, with antagonistic effects between nitrogen deposition and low-sulfur composite deposition and synergistic effects between nitrogen deposition and high-sulfur composite deposition. In conclusion, sulfur deposition and the combined nitrogen and sulfur deposition affected leaf litter decomposition rate in the evergreen broad-leaved forest, with consequences on the litter decomposition process.

[Effects of simulated nitrogen deposition on soil microbial biomass carbon and nitrogen in natural evergreen broad-leaved forest in the Rainy Area of West China]. / 模拟氮沉降对华西雨屏区天然常绿阔叶林土壤微生物生物量碳和氮的影响.

To understand the effects of increasing nitrogen deposition on soil microbial biomass carbon (MBC) and nitrogen(MBN), an in situ experiment was conducted in a natural evergreen broad-leaved forest in Ya'an City, Sichuan Province. Four levels of nitrogen deposition were set: i.e., control (CK, 0 g N·m-2·a-1), low nitrogen (L, 5 g N·m-2·a-1), medium nitrogen (M, 15 g N·m-2·a-1), and high nitrogen (H, 30 g N·m-2·a-1). The results indicated that nitrogen deposition significantly decreased MBC and MBN in the 0-10 cm soil layer, and as N de-position increased, the inhibition effect was enhanced. L and M treatments had no significant effect on MBC and MBN in the 10-20 cm soil layer, while H treatment significantly reduced. The influence of N deposition on MBC and MBN was weakened with the increase of soil depth. MBC and MBN had obvious seasonal dynamic, which were highest in autumn and lowest in summer both in the 0-10 and 10-20 cm soil layers. The fluctuation ranges of soil microbial biomass C/N were respectively 10.58-11.19 and 9.62-12.20 in the 0-10 cm and 10-20 cm soil layers, which indicated that the fungi hold advantage in the soil microbial community in this natural evergreen broad-leaved forest.

[Characteristics of carbon stock in artificial forest ecosystem in Sichuan Province of China].

By using forest inventory data in combination with plot measurement, the characteristics of carbon density, stock, and partitioning in artificial forest ecosystem in Sichuan Province of China were studied. The results showed that the carbon density in this forest ecosystem was averagely 161.16 Mg C x hm(-2), being ranked in the order of soil layer (141.64 Mg C x hm(-2)) >tree layer (17.95 Mg C x hm(-2)) >litter layer (1.06 Mg C x hm(-2)) >shrub layer (0.52 Mg C x hm(-2)), and the total carbon stock was 573.57 Tg C, with 63.88 Tg C, 1.836 Tg C, 3.764 Tg C, and 504.09 Tg C, accounting for 11.14%, 0.32%, 0.66%, and 87.88% of the total in tree layer, shrub layer, litter layer, and soil layer, respectively. The carbon density and stock in different artificial forest ecosystems varied from 75.50 Mg C x hm(-2) to 251.74 Mg C x hm(-2) and from 1.21 Tg C to 99.44 Tg C, with the highest and lowest values observed in soil layer and shrub layer, respectively. Comparing with other regions in China, Sichuan Province had a lower carbon density in the tree layer of artificial forest ecosystem, due to the higher proportion of young and middle age forest stands, which implied that a proper management of artificial forest could increase the carbon sequestration in forest ecosystem of Sichuan. To monitor the carbon stock in artificial forest ecosystem at ecosystem level could be helpful to the improvement of the precision of forest carbon sequestration evaluation.

[Spatiotemporal variation of carbon storage in forest vegetation in Sichuan Province].

Based on the modeling of forest biomass and timber volume and the 1974-2004 forest inventory data, the spatiotemporal variation of carbon density and storage in forest vegetation in Sichuan Province was studied. The results showed that the forest carbon storage was increased from 300.02 Tg in 1974 to 469.96 Tg in 2004, with an annual increment of 1.51%, which suggested that the forests in Sichuan Province were the sink of CO2. However, owing to the increase of plantations, the average carbon density of forest vegetation decreased from 49.91 Mg x hm(-2) to 37.39 Mg x Shm(-2), implying that Sichuan forests had a great potential of carbon sequestration through artificial forest management. The carbon storage in Sichuan forests had a spatial heterogeneity, and the ranked order was northwest alpine gorge area > southwest mountainous area > low-mountain area > hilly area > western plain. Forest carbon density increased from southwest area to northwest area, with the order of hilly area < northern plain < southwest mountain area < low-mountain area < northwest alpine gorge area. It was suggested that forest management according to different sub-regions would improve the potential of carbon sequestration in Sichuan forests.