贵阳市不同土地利用方式土壤有机碳地球化学研究

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	贵阳市不同土地利用方式土壤有机碳地球化学研究
其他题名	Geochemical Characteristics of Soil Organic Carbon under different land use conditions in Guiyang City
	涂成龙
	2007-12-30
学位授予单位	中国科学院地球化学研究所
学位授予地点	地球化学研究所
学位名称	博士
关键词	自然土壤农业土壤城市土壤有机碳溶解性有机碳
摘要	本研究根据贵阳市区域内不同土地利用方式，选择了自然土壤、农业土壤和城市土壤为主要研究对象。对表层土壤实行多样点的统计分析、以及典型剖面有机碳迁移过程分析，同时结合同位素地球化学示踪原理，探讨了贵阳市区域内土地利用方式变化对土壤有机碳的影响，以及不同土地利用方式间土壤有机碳的来源和降解过程的差异。主要结论如下： (1) 自然土壤转化为农业土壤后，表层(0～10cm) SOC有较为明显的降低趋势。其中，相对于自然土壤(黄壤) 表层SOC(平均值)而言，玉米地、水田、果园下降了40%左右，菜地下降了15%左右。然而，不同菜地土壤间耕种强度存在较大差异，其SOC变异程度高于其它几类农业土壤(CV＝57.07%)。与之相反，农业土壤表层DOC(18.86～48.20mg•L-1)接近或超过自然土壤(10.74～36.30 mg•L-1)，且ƒDOC占SOC的比例明显大于自然土壤。其中，玉米地DOC最高(平均值：48.20mg•L-1)，菜地次之(平均值：30.00mg•L-1)，果园第三(平均值：29.87mg•L-1)，水田最低(平均值：18.86mg•L-1)，但水田由于干湿交替的影响，DOC的变异程度最大(CV＝128.57%)。据此推断，在相同气候条件下，自然土壤转化为农业土壤后，由于表层DOC数量和比例的增加，提高了SOC的迁移性，进而加速了碳素在土壤中的迁移转化进程。 (2) 自然土壤转化为农业土壤后，剖面内部(>10cm)多数层次SOC相对于黄壤和黄色石灰土有明显的增加趋势。且通过对不同类型农业土壤人为干扰强度的调查表明：人为干扰强度越强，剖面中一定深度内SOC增加幅度越大。即：离城市较近的菜地2增长最为突出，果园其次，水田和玉米地相当。离城市较远的菜地1由于受人为干扰层次较浅，且出现了犁底层，剖面内SOC的含量水平与黄色石灰土相当。 (3) 原始土壤经搬运重组后形成城市公路绿化带土壤，表层SOC和DOC变幅较宽、离散程度较大，且没有随时间或植被类型等因素的变化而呈现明显的变化趋势。其中，SOC变异程度依次为新成公路绿化带2(CV＝58.0％)、老成公路绿化带(CV＝55.5％)、新成公路绿化带1(CV＝34.1％)。DOC变异程度依次为新成公路绿化带1(CV＝93.8％)、新成公路绿化带2(CV＝85.7％)、老成公路绿化带(CV＝78.0％)。 (4) 在自然土壤、农业土壤和城市绿化带土壤表层中，DOC与SOC、N、C/N、NO3-、NH4-，以及粘粒含量等的相关性均未达到显著水平。另据方差分析显示：果园、水田、菜地和玉米地表层土壤间DOC、SOC含量均无显著差异，说明农业土壤利用方式不是决定土壤表层SOC和DOC含量的绝对因素；新成公路绿化带1，2和老成公路绿化带表层土壤间DOC、SOC含量均无显著差异，说明植被类别和形成时间不是决定土壤表层SOC和DOC含量的绝对因素。 (5) 自然土壤中，枯枝落叶转化为表层(0～5cm)土壤有机质后，δ13CSOC值升高了1~4‰。通过不同碳源间δ13Corg相互关系的判断，在具备枯枝落叶覆盖的表层土壤中，DOC主要来源于枯枝落叶；而在土壤剖面内，随土壤剖面深度的增加，来自于土壤腐殖类物质的DOC占土壤DOC总量的比例呈增加趋势。在黄壤和黄色石灰土中(>5cm土层)，土壤剖面中大多数层次DOC比SOC更富13C。 (6) 大多数农业土壤有机碳δ13C值显示其有机肥源中存在C4-C源。且农业土壤中受碳源多样性的影响，菜地、果园、水田和玉米地表层土壤中δ13CSOC与δ13CDOC的相关性均未达到显著水平。其次，除玉米地土壤剖面外，其它供试农业土壤剖面大多数层次δ13CDOC值比δ13CSOC偏负，说明菜地、果园、水田土壤DOC主要为外源的加入。 (7) C3植被转化为C4植被(林-农生态系统转化)后，玉米地剖面中SOC有2.55％～20.80％源于C4-C，随剖面层次的加深有降低趋势，但表现为“之”字形反复；DOC中C4-C的比例在剖面0～40cm处较为相近(25.94％～34.54％)，40cm以下则急剧下降(3.18％～15.65％)。说明玉米地剖面 DOC主要来源于土壤腐殖类物质的转化。与林-农生态系统转变过程中的变化趋势相反，洼地农业土壤退耕弃荒一段时间(林-农-林生态系统转化)后，土壤剖面内C4-C占SOC的比例随土壤层次的加深逐渐增加，变化范围在5.77～26.76％。 (8) 在C3植被转向C4植被(林-农生态系统转化)后，玉米地δ13CSOC值与C4-C、C3-C相关系数(r)分别为0.372和-0.102，δ13CDOC值与C4-C、C3-C相关系数分别为0.131和-0.339，其相关性均未达到显著水平。而再从C4植被转回C3植被后，土壤δ13CSOC与C3-C之间呈显著相关性（r=0.88，n＝7），说明退耕弃荒后新加入的C3-C对土壤δ13CSOC值影响较大。其SOC的主要来源于洼地周边坡面土壤的侵蚀堆积物和新生草本植被残体。结合当前SOC降解过程的研究成果，本研究认为：洼地土壤退耕弃荒后一段时间里，土壤SOC可能处于累积大于损失状态。这有利于土壤性状向良性方向发展。 (9) 根据同位素值的相互关系和有机碳的来源调查，判断公路绿化带土壤中C4-C为原始土壤所带来。大气颗粒物和雨水中的DOC是表层土壤DOC的主要来源。公路绿化带土壤剖面中，随着时间的增加，土壤腐殖类物质与DOC的相互转化逐渐加强。上述结论可为人类认识城市区域(特别是有强烈酸性沉降历史的喀斯特城市区域)土地利用方式改变对土壤碳循环的影响，以及不同土地利用方式间土壤有机碳迁移转化过程提供科学依据，也可为正确评估城市区域土壤与其他圈层间碳循环的源、汇关系提供基础资料。
其他摘要	Soils under different land-use conditions, such as undisturbed soils, agricultural soils and urban soils，were collected in the Guiyang city with the main purpose to investigate the geochemical cycling of organic carbon in these soils. Based on the method of statistical analysis, isotopic tracing techniques and the mass balance theory, the geochemical characteristics of the content, origin and the degradation process of soil organic carbon (SOC) and soil dissolvable organic carbon (DOC) were studied with change of land-use type. In addition, the differences of SOC’s geochemical cycling were discussed between a few land-use types. The main results as follow: (1) When undisturbed soils are cultivated to be agricultural soils, the SOC contents decrease in surface soils. Compared with undisturbed surface soils (yellow soils), SOC contents in corn and paddy field, decrease by 40% and 20% in vegetable soils decrease approximately. However, because farming intensity is different between vegetable soils, the variance range of SOC in the vegetable land soils is the most wide (CV＝57.07%). On the contrary, the DOC contents of agricultural soils are close to or more than that of the undisturbed soils. The percentages of ƒDOC occupying SOC are bigger than that in the undisturbed soils. The DOC content of soils are as follow: the most is in corn land soil (mean value: 48.20mg•L-1), the second is in the vegetable land soils (mean value: 30.00mg•L-1), the third is in the orchard soils (mean value:29.87mg•L-1), the smallest is in the paddy field soils(mean value:18.86mg•L-1). Based on these information, the paper put forward that the cycle speed of SOC enhances with DOC content and percentage of ƒDOC occupying SOC increasing. (2) Compared with yellow soils and rendzina soil (undisturbed soil), SOC content rise in most of soil layers of agricultural soil profiles. Based on the investigation of farming intensity in agricultural soil with different land-use type, there is a trend that SOC content increases with farming intensity rising. Namely, increased amount of SOC is the most in the second type vegetable soils, second in orchard soil, third in paddy field soils and corn soils. (3) As some raw soils (most is yellow soil) are removed to be road green belt soils, there isn’t a trend that the SOC and DOC content become more or less with time or plant types change. The SOC variance coefficient in the first and second type new road green belt soils and the old road green belt soils are 34.1%, 58.0%, 55.5% respectively. The DOC variance coefficient in the first and second type new road green belt soils and the old road green belt soils are 93.8%, 85.7%, 78.0% respectively. (4) The relationships between DOC and SOC, N, C/N, NO3-, NH4+ and the clay content are not significant in undisturbed soils, agricultural soils and road green belt soils. In addition, analysis of variance shows that DOC or SOC content are not significant between orchard soils and paddy field soils, vegetable soils, corn soils, and are not significant between different road green belt soils. Those indicate that land-use type in agricultural soils or plant type and time in road green belt soils is not determined factor, which influences on the content of DOC or SOC. (5) The values of δ13CSOC would be enriched by 1~4‰ during litter degrading to be SOC in undisturbed surface soil. The litter-rich surface soil has high content of DOC, the δ13CDOC is similar to δ13C of litter; while the litter-lack surface soil has low content of DOC, and the δ13CDOC is similar to δ13CSOC. It suggests that DOC derives from litter in the litter-rich surface soil. In some mature soil profiles, δ13CSOC and δ13CDOC become more positive with the depth increase. It indicates the degradation degree of SOC is more successful with the depth increase. The variation trends of δ13CSOC and δ13CDOC in soil profiles are similar and the values of Δ(δ13CDOC－δ13CSOC) with the increasing of depth indicate the percentage of DOC under 5cm, which derives from humus degradation, increase with depth. In the premature soil profiles, the variety of δ13CSOC also reflects the mixture of young and old SOC. (6) The δ13CSOC shows that there is C4-C source in agricultural soil organic matter. Because SOC in agricultural soils derive from various sources, the relationships between δ13CSOC and δ13CDOC are not significant. In addition, most of the values of δ13CDOC are more negative in the agricultural soil profiles except for corn soil profiles. It indicates that DOC in agricultural soils is added by human. (7) In corn field soil profile, the C4-C percentage of SOC is between 2.55％ and 20.80％, but zigzag with soil depth; the C4-C percentage of DOC in 0～40cm is similar(25.94％～34.54％), while that under the 40cm decreases abruptly(3.18％～15.65％). These indicate that SOC derives from degradation of humus in whole corn land soil profile. On the contrary, with shift of forest-crop-forest ecosystem, the percentage of C4-C increased with depth in billabong soil profile, the range is 5.77～26.76％. (8) With shift of forest-crop ecosystem, the correlation coefficient between δ13Csoc and C4-C, C3-C is 0.372 and -0.102 respectively; the correlation coefficient between δ13CDOC and C4-C, C3-C is 0.131and -0.339, the relationship is not significant. With shift of forest-crop-forest ecosystem, the relationship between δ13Csoc and C3-C was significant, it indicates δ13Csoc influenced mainly by new C3-C. Based on the theory about degradation of soil organic matter, the paper put forward that the amount of billabong SOC is likely to increase. (9) Based on the investigation on the sources of soil organic matter and the relationships between δ13Corg of the different sources, C4-C in SOC was considered to be derived from original soil in the city road greenbelt soil. The DOC in the rain and air particles can be main sources of DOC in the city road greenbelt soil. The percentage of DOC derived from degradation of humus increases with time. These results described above can be very important scientific information for improving our understanding of soil carbon cycle under different land-use conditions in city area, especially, which locate at Karst region with heavy acid precipitation. In addition, these results are useful to be use to value “source” and “sink” between pedosphere and other spheres.
页数	143
语种	中文
文献类型	学位论文
条目标识符	http://ir.gyig.ac.cn/handle/352002/3360
专题	研究生_研究生_学位论文环境地球化学国家重点实验室
推荐引用方式 GB/T 7714	涂成龙. 贵阳市不同土地利用方式土壤有机碳地球化学研究[D]. 地球化学研究所. 中国科学院地球化学研究所,2007.

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