氮素富集对青藏高原高寒草甸土壤有机碳迁移和累积过程的影响  

EFFECTS OF NITROGEN ENRICHMENT ON TRANSFER AND ACCUMULATION OF SOIL ORGANIC CARBON IN ALPINE MEADOWS ON THE QINGHAI-TIBETAN PLATEAU

作　　者：李林森[1] 程淑兰[1] 方华军[2] 于贵瑞[2] 徐敏杰[1] 王永生[2] 党旭升[2] 李英年[3] 

机构地区：[1]中国科学院大学资源与环境学院,北京100049 [2]中国科学院地理科学与资源研究所生态系统观测与模拟重点实验室,北京100101 [3]中国科学院西北高原生物研究所,西宁810001

出　　处：《土壤学报》2015年第1期183-193,共11页Acta Pedologica Sinica

基　　金：农业部农业环境与气候变化重点开放实验室开放基金;中国科学院知识创新工程重要方向项目(Y225017EA2);中国科学院地理科学与资源研究所"秉维"优秀青年人才基金(2011RC202)资助

摘　　要：为深入揭示陆地生态系统碳固定对大气氮沉降增加的响应机理,基于海北高寒草甸多形态(NH4Cl、(NH4)2SO4、KNO3)、低剂量(N 0、10、20、40 kg hm-2a-1)的增氮控制试验平台,采集各处理水平下不同深度土壤样品,利用颗粒分组法分离测定总土壤有机碳(SOC)以及各粒径组分的碳含量和δ13C值。研究结果表明:低氮显著增加了土壤粗颗粒态有机碳(Macro POC)和矿质结合态有机碳(MAOC)的含量,而高氮处理正好相反。施氮一致降低土壤细颗粒态有机碳(Micro POC)含量。此外,添加硝态氮肥对SOC各组分含量和δ13C值的影响显著高于铵态氮肥。总体而言,低氮导致地表30 cm层SOC储量增加了4.5%,而中氮和高氮导致SOC储量分别下降了5.4%和8.8%。低氮处理时新增的碳以Macro POC为主,而高氮处理时损失的碳主要是Micro POC。连续5 a施氮促进了颗粒态有机碳(POC)组分的分解,进而导致SOC稳定组分的比例增加。可以认为,大气氮沉降或低剂量施氮(10 kg hm-2a-1)短期内有利于青藏高原高寒草甸土壤碳截留,硝态氮较铵态氮输入对土壤碳储量增加更为有益。Increasing atmospheric nitrogen （N） deposition can significantly change carbon （C） cycling rates and budget in the terrestrial ecosystem, and is generally considered to be an important pathway of missing of the sink. Howev- er, the contribution of atmospheric N deposition to C sequestration in the terrestrial ecosystem is controversial. It is, there- fore, essential to accurately evaluate the effects of rate and type of N deposition on amount, composition and stability of soil organic carbon （SOC）. Stable C isotope natural abundance （or t^3C） contains various information concerning C cyc- ling processes, and hence makes it feasible to track SOC in its transfer, transformation and accumulation processes. The technique of Stable J3C natural abundance provides a way to characterize the dynamics of SOC with different turnover times. It is hypothesized in this study that N deposition increases biomass of plants and 13C-depleted plant debris that leads to expansion of the fraction of coarse particle-sized SOC. Meanwhile, increased N deposition promotes activities of soil mi- crobes, and increases emission of 13C-depleted CO2, thus leading to decrease in SOC content and accumulation of δ13C. Consequently, this study is mainly aimed at determination of the effects of rate and type of N deposition on contents of SOC and its various particle-size fractions in the soil and quantification of relative contributions of the changes in these fractions to the change in total under the condition of N accumulation. Through the above-described researches, it is expected a better in-depth knowledge could be obtained regarding mechanisms of the effects of N deposition on deposit and stability of SOC. For that end a controlled multi-form, low-rate N addition field experiment was conducted at the Haibei Alpine Mead- ow Ecosystem Research Station in 2007. The experiment was designed to have three types of N fertilizers, NH4 C1, （ NH,）2SQ and KNO3 , and four N application rates： 0, 10, 20 and 40 kg hm-2 a-1 , and th

关 键 词：氮沉降 颗粒有机质 土壤有机质稳定性 稳定性碳同位素丰度 高寒草甸 

分 类 号：S154[农业科学—土壤学]