作 者 ：涂利华,胡庭兴*,张健,李仁洪,何远洋,田祥宇,肖银龙,景建飞
期 刊 ：生态学报 2010年 30卷 9期 页码：2286~2294
Keywords:simulated nitrogen deposition, soil active carbon pool, root biomass, Neosinocalamus affinis plantation, Rainy Area of West China,
摘 要 ：从2008年1月起，对华西雨屏区慈竹(Neosinocalamus affinis)人工林进行了模拟氮沉降试验，氮沉降水平分别为对照(CK, 0 g?m-2?a-1)、低氮(5 g?m-2?a-1)、中氮(15 g?m-2?a-1)和高氮(30 g?m-2?a-1)。在模拟氮沉降1.5 a后，按土层深度取土样和根样，测定不同深度土壤活性有机碳含量和根生物量。结果表明，华西雨屏区慈竹林土壤有机碳、微生物量碳、浸提性溶解有机碳和活性碳含量均随土层深度的增加而减少。氮沉降显著减少了土壤微生物量碳和活性碳含量，显著增加了浸提性溶解有机碳含量，并使得土壤碳库管理指数减小。同时，慈竹林根密度在氮沉降条件下减少了12%-14%。说明氮沉降的增加减少了土壤有机碳中的活性部分，增加了土壤有机碳的淋溶流失，降低了慈竹林土壤碳库质量。同时，根系生物量的减少，间接影响了土壤微生物活动和土壤碳周转过程。在未来氮沉降持续增加的背景下，慈竹林土壤对碳的保持能力可能会下降。
Abstract:Increasing nitrogen (N) deposition affects the carbon cycle in terrestrial ecosystems largely. In general, the potential carbon accumulation response of aboveground to N deposition is nearly positive in plantations and natural forests, while that of belowground is unclear because there′re some difficulties such as quantifying root biomass (RB), detecting soil organic carbon (SOC) and its components. Following the N deposition increasing, complete understanding of belowground carbon accumulation response to N deposition is critical to assess forest soil carbon cycle. The bamboo forest, one of the normal terrestrial ecosystems, plays an important role in balancing the carbon budget. However, the effect of N deposition on soil active carbon pool (SACP) and root biomass in bamboo forest is still poorly understood. Our objectives were to quantify the effect of simulated N deposition on SACP and RB in bamboo plantation within the Rainy Area of West China. The present study was conducted in the 18a Neosinocalamus affinis plantation located in the bamboo plantation of Sichuan Agricultural University, Ya′an City, southwest Sichuan Province (30°08′ N, 103°00′ E, 660 m above sea level), and the natural wet nitrogen deposition was 14.75 g?m-2?a-1. Twelve plots were established and divided into four N addition treatments (Control, 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) with three replicates. Each square plot was 3 m 3 m, and randomly distributed in the plantation, which intervals were more than 3 m. NH4NO3 was added to each plots after every 15-day from December 2007. After 1.5 years, soil samples (0-20, 20-40, 40-60, and 60-80 cm) were collected to measure the SACP and RB. The results indicated concentrations of soil total organic carbon (TC), microbial biomass carbon (MBC), extractable dissolved organic carbon (EDOC) and liable carbon (LC) decreased with soil depth. N deposition decreased soil MBC and LC significantly, while increased EDOC significantly. The soil carbon management index (CMI) was decreased and the fine root density was decreased from 12% to 14%. It is highlighted that nitrogen addition reduced the active components in soil carbon pool, stimulated the leaching of soil carbon in the form of EDOC and reduced the quality of soil carbon pool in N. affinis plantation. The reduction of root biomass carbon input might indirectly affect microbial activity and carbon turnover. Our results suggest that the response of SACP and RB of N. affinis plantation to atmospheric N deposition demonstrates a decline trend. The chronic increasing N deposition may reduce the retention of C in the soil of N. affinis plantation.
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