引用本文:韩光中,张甘霖,黄来明,陈留美,李山泉.水耕人为土有机碳和全氮对水分状况和耕作时间的响应[J].土壤学报,2019,56(6):1300-1308.
HAN Guangzhong,ZHANG Ganlin,HUANG Laiming,CHEN Liumei,LI Shanquan.Responses of Organic Carbon and Total Nitrogen in Hydragric Anthrosols to Variation of Water Regime and Cultivation in Age[J].Acta Pedologica Sinica,2019,56(6):1300-1308
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水耕人为土有机碳和全氮对水分状况和耕作时间的响应
韩光中1, 张甘霖2, 黄来明3, 陈留美4, 李山泉5
1.内江师范学院资源与环境科学学院;2.中国科学院南京土壤研究所;3.中国科学院地理科学与资源研究所;4.遵义师范学院;5.邢台学院
摘要:
以我国南方地区数十年至千年尺度的水耕人为土时间序列为研究对象,分析水耕人为土有机碳(SOC)和全氮(TN)对水分状况和耕种时间的响应,阐明不同水分类型水耕人为土的固碳趋势。结果表明,水耕人为土SOC的演变特征和固碳能力受水分状况和起源土壤SOC含量的影响很大。进贤序列(地表水型)在种稻初期SOC的增加主要集中在耕作层,到一定阶段后下层也明显增加。慈溪序列(良水型)SOC只在耕作层累积,种稻50 a内基本达到饱和。中山序列(地下水-良水型)SOC在种稻30 a内达到饱和,之后随地下水位的下降而略有下降。相比之下,宝应序列(地下水-良水型)SOC在种稻5 a内相对稳定,之后在15 a内地下水位明显下降,SOC显著降低。不同水分类型水耕人为土耕作层碳氮比(C/N)随耕种年限的增加均表现出明显的趋同性,高度熟化的水耕人为土耕作层可能存在相近的碳氮耦合平衡。地表水型水耕人为土在300 a内可一直作为相对稳定的农田有机碳汇,但固碳速率偏低。进贤、中山和宝应序列水耕人为土TN的演变特征和其SOC的演变特征基本一致。慈溪序列土壤含有较多的无机氮,TN的演变特征和其SOC的演变特征差异很大。要注意评估无机氮含量高的水耕人为土在长期耕种过程中土壤氮富集或亏损对环境的影响。
关键词:  水耕人为土  水分类型  有机碳  碳氮比  有机碳密度
DOI:10.11766/trxb201812190421
分类号:
基金项目:国家自然科学基金项目(41401235)、四川省科技计划(2018JY0527)和四川省教育厅重点项目(17ZA0223)
Responses of Organic Carbon and Total Nitrogen in Hydragric Anthrosols to Variation of Water Regime and Cultivation in Age
HAN Guangzhong1, ZHANG Ganlin2, HUANG Laiming3, CHEN Liumei4, LI Shanquan5
1.Neijiang Normal University;2.Institute of Soil Science, Chinese Academy of Sciences;3.Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences;4.Zunyi Normal University;5.Xingtai University
Abstract:
【Objective】Though carbon sequenstration of agricultural soils is one of the focuses of current concern, little has been reported on how soil carbon and nitrogen varies dynamically in Hydragric Anthrosols different in water regime and cultivation age. 【Method】Taking advantage of the long-term paddy cultivation history in China, four types of Hydragric Anthrosols along the chronosequence from a dozen years to a thousand years, were specified in Jinxian of Jiangxi (Jinxian sequence), Cixi of Zhejiang (Cixi sequence), Zhongshan of Guangdong (Zhongshan sequence) and Baoying of Jiangsu (Baoying sequence) for exploration of how organic carbon (SOC) and total N (TN) in the soils responds to changes in water regime and cultivation history. 【Result】Soil organic carbon accumulation was mainly affected by water regime and content of soil organic carbon. For the Jinxian sequence (surface water type), soil organic carbon accumulated mainly in the anthrostagnic epipedon within the first 100 years of rice cultivation and then in subsoil with cultivation going on. For the Cixi sequence (well-drained water type), soil organic carbon accumulated only in the anthrostagnic epipedon and reached to the point of saturation within the first 50 years of rice cultivation. For the Zhongshan sequence (ground water & well-drained type), soil organic carbon reached to the point of saturation within the first 30 years of rice cultivation and then slightly decreased in content with cultivation going on as the groundwater table lowered. In contrast, for the Baoying sequence (also ground water & well-drained type), soil organic carbon was relatively stable in content within the first 5 years of rice cultivation and then significantly decreased with the groundwater table within the following 15 years. All the four types of Hydragric Anthrosols tended to be similar in carbon/nitrogen ratio in the cultivated horizon with paddy cultivation going on for long and had similar carbon-nitrogen coupling balance in highly mellowed plow layers of the Hydragric Anthrosols. The paddy soils of the Jinxian sequence could be deemed as a stable organic carbon sink within 300 years though their carbon sequestration rates tended to be low. For instance, SOCD of the soils increased on average by 3 g•m-2•a-1 only. Following the current normal management and utilization levels, the paddy soils of the Cixi, Zhongshan and Baoying sequences would have their soil carbon pools saturated up to a level compatible tto their water regimes within 15~50 years, thus keeping SOC in a relatively stable balance. In soils relatively high in ground water table, high yield oriented practices, such as drainage, could lower the ground water table, which could lead to rapid depletion of soil organic carbon. 【Conclusion】Evolution of the soil organic carbon pool in and carbon sequestration capacity of Hydragric Anthrosols are highly subject to the impacts of water regime and initial organic carbon content in the soil. It is, therefore, essential to pay enough attention to adoption of certain high-yield oriented agricultural practices and agricultural policies that may cause changes in water regime and their impacts on the soil organic carbon pool in paddy fields. The Jingxian, Zhongshan and Baoying sequences of Hydragric Anthrosols are basically consistent in evolution characteristics of TN and SOC. Hydragric Anthrosols of the Cixi sequence contain relatively more inorganic N and differ quite sharply from the others in evolution characteristics of TN and SOC. So adequate attention should be paid to evaluation of impacts of excessive accumulation or depletion of N in Hydragric Anthrosols that are high in inorganic N content on long-term rice cultivation.
Key words:  Hydragric Anthrosols  Water type  Soil organic carbon  C/N ratio  Soil organic carbon density