摘要
自20世纪80年代,大面积的青藏高原草甸地被开垦为农田并进行了长期施肥,这可能对其土壤中长期累积的腐殖质产生重要影响,并进而影响肥力供应和土壤环境化学过程。应用紫外—可见光谱、傅里叶变换—红外光谱和平行因子分析—三维荧光光谱技术综合表征未开垦的青海草甸和开垦后不同施肥处理的油菜地中黑钙土腐殖质的光谱特征,以揭示开垦与长期施肥对腐殖质组成与来源的影响,为青藏高原草甸的农业活动管理提供理论支撑。结果表明:开垦使土壤有机质显著降低,而施肥使得土壤保肥与营养供给能力增强。长期施肥在减缓土壤有机质降低的同时会造成土壤酸化。紫外—可见光谱指出开垦后长期施肥可能导致了胡敏酸的腐殖化程度、相对分子量、芳香性和对外源依赖性的提高。富里酸在开垦后长期施肥的处理下则表现为腐殖化程度、相对分子量和芳香性均降低,而对内源依赖性提高。傅里叶变换—红外光谱指出长期施肥有利于土壤中羧酸类物质的生成。同时,长期施肥增加了土壤中作物的生物量而使土壤中的碳水化合物和脂肪族有机物大量消耗。结合平行因子分析的三维荧光光谱识别出青海黑钙土腐殖质中含有5个有机质组分,分别为:两个类胡敏酸组分、两个UVC类富里酸组分和一个水溶微生物副产物组分。开垦与长期施肥还显著影响了腐殖质的分子组成,使胡敏酸的大分子组分相对增加,小分子组分相对降低。富里酸在开垦并长期施肥的处理下,其大、小分子组成数量均增加,但小分子组成增加得更为显著。综上,建议青藏高原的农垦活动应当谨慎进行,可增加施用有机肥以减缓土壤有机质的降低,并在提高土壤腐殖质腐殖化程度的基础上扩展富里酸的来源。应当进一步研究腐殖质功能性结构对青藏高原开垦和长期施肥的响应,以探明土壤碳固定,并提出管理措施来维持青藏高原土壤中的碳平衡。
【Objective】Since the 1980 s,a large area of meadow on the Qinghai-Tibet Plateau has been reclaimed to be cropland along with a long term of fertilization,which may have an import influence on soil humus and thereby soil fertility and environmental chemical process in soil.This study was oriented to explore effects of reclamation and long-term fertilization on humification degree,relative molecular weight,aromaticity and source of the humus in an oilseed cole field of chernozem in Qinghai,with a view of providing certain theoretical support for management of agricultural activities in meadows of the QingHai-Tibet Plateau.【Method】In this study,basic physic-chemical properties of chernozem and spectral properties of the humus in a cole field of chernozem under reclamation and long-term fertilization and a tract of virgin meadow of chernozem in Qinghai were characterized by means of UV-vis,Fouriertransform infrared and Parallel factor analysis,three-dimensional fluorescence spectroscopy for comparison.【Result】Results show that reclamation and long-term fertilization significantly affected basic physicochemical properties of the chernozem,the spectral properties of the humic acid and fulvic acid in the soil and molecular composition of the soil humic substances.In terms of soil physico-chemical properties,reclamation significantly reduced soil organic matter,while fertilization enhanced soil fertility and nutrient supply.However,long-term fertilization led to soil acidification,while slowing down the decreasing process of soil organic matter,thus causing degradation of soil quality.UV-vis spectra indicate that reclamation and long-term fertilization enhanced humification degree,relative molecular weight,aromaticity and dependence-on-extraneous-sources of humic acids,but affected all the indices of fulvic acids reversely,except for dependence-on-extraneous-sources,while FT-IR spectra indicate that long-term fertilization facilitated formation of carboxylic acids in the soil,increased biomass of the crops,which in turn depleted much carbohydrate and aliphatic organic matter in the soil.Parallel factor analysis and three-dimensional fluorescence spectra identified five components of soil humus including two types of humic acid-like substances,two types of fulvic acid-like substances and a soluble microbial by-product.Reclamation and long-term fertilization also affected composition of the humus,by relatively expanding the fraction of largemolecule humic acids and shrinking the fraction of small ones,but expanded the fractions of both largeand small-molecular fulvic acids,especially the latter.【Conclusion】All the findings in this study suggest that careful attention should be paid to agricultural reclamation of the meadow resources of the QinghaiTibet Plateau and that it is advisable to apply organic manure to retard reduction of organic matter,and to expand the sources of fulvic acids while increasing humidification degree of soil humus.Further study on the response of functional structure of soil humus to the reclamation and long term of fertilization is also suggested to detect the carbon sequestration and to put forward management practice to maintain carbon balance in soil of the Qinghai-Tibet Plateau.
作者
张桐
何小松
李猛
刘元元
席北斗
张慧
李丹
ZHANG Tong;HE Xiaosong;LI Meng;LIU Yuanyuan;XI Beidou;ZHANG Hui;LI Dan(State Key Laboratory of Environmental Criteria and Risk Assessment,Chinese Research Academy of Environmental Sciences,Beijing 100012,China;School of Urban Construction and Environmental Engineering,Chongqing University,Chongqing 400044,China)
出处
《土壤学报》
CAS
CSCD
北大核心
2019年第2期398-407,共10页
Acta Pedologica Sinica
基金
国家自然科学基金项目(41701561
51325804)
中国博士后科学基金项目(2016M601095)资助~~
关键词
青藏高原
土壤有机质
施肥
开垦
光谱分析
Qinghai-Tibet Plateau
Soil organic matter
Fertilization
Reclamation
Spectral analysis
