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海螺沟冰川退缩迹地风化——成土过程与土壤磷形态研究
Alternative TitleWeathering, pedogenesis and changes of soil phosphorus speciation of Hailuogou Glacier foreland chronosequence
Language中文
周俊
Thesis Advisor吴艳宏
2014
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Name博士
Degree Discipline自然地理学
Keyword早期风化过程 风化速率 磷释放 磷生物有效性 磷形态
Abstract土壤磷的生物有效性对植被原生演替具有重要影响。虽然对长时间尺度上磷形态的演变及驱动因素的研究已取得大量成果,但是,“年轻”土壤时间序列上磷形态及生物有效性的演变和驱动机制仍不清楚,而这是阐明磷循环与植被演替之间关系的基础。磷的最终来源为岩石的风化,然而,当前的研究多关注磷释放后在生态系统的生物地球化学过程,对矿物风化过程中磷的释放过程与释放速率的研究却较少。此外,随着原生矿物的风化,土壤中会逐渐生成无定形的金属矿物和次生粘土矿物,这些矿物如何影响磷的生物有效性,也尚待阐明。自然界的风化是一个漫长的地质过程,难以在实验室进行模拟,因此,具有较为明确年龄的冰川退缩迹地土壤时间序列成为研究矿物风化与磷释放过程、以及磷形态和生物有效性随土壤年龄变化的“天然实验室”。 本论文针对贡嘎山海螺沟冰川退缩迹地土壤时间序列(120年),根据土壤年龄(0、12、30、40、52、80和120年)采集土壤和水体样品,采用野外原位观测、实验室矿物连续提取、水化学分析、矿物成分分析、土壤磷连续提取和统计分析等方法,研究海螺沟冰川退缩迹地的矿物风化、磷释放与土壤发育过程,定量评估矿物风化与磷释放速率,阐明早期成土过程中土壤磷形态与生物有效性的变化,揭示控制风化、磷释放与形态演变的关键驱动机制。主要结果和结论如下: (1) 海螺沟冰川退缩迹地土壤母质中硅酸盐矿物(主要为石英和长石)的平均含量为91.3%,只含有极少量的碳酸盐矿物方解石,母质的矿物组成较为均一。水化学分析的结果表明退缩迹地溪流的水化学类型为Ca2+——HCO3-,表明水体主要离子的来源为碳酸盐的风化;退缩迹地内溪流的溶解性总固体(TDS)含量显著高于海螺沟流域水体的含量,表明冰川退缩迹地的风化作用显著强于相邻区域。长期风化速率呈倒抛物线的变化模式,52年样点为最低值,在冰川退缩120年后达到111 cmolc/m2?yr,远高于阿尔卑斯山以及一些热带地区土壤序列的风化速率。碳酸盐矿物的快速溶解是导致风化作用一开始就具有较高速率的主要原因,而52年样点后一定量的黑云母、角闪石和斜长石被风化,导致风化速率又逐渐上升。强烈的冰川作用和冻融交替等物理风化过程为化学风化提供了大量的粉粒物质,而充足的水分条件和快速发育的植被进一步促进化学风化快速进行。 (2) 从土壤剖面发育、交换性阳离子量、铝和铁活化度、pH值和C、N积累等指标来看,海螺沟冰川退缩迹地土壤展现出快速发育的特征。土壤母质总体呈中性至弱碱性,表层pH随土壤年龄的增加而快速降低,在冰川退缩80年后降至5以下,主要受植被种类及随之变化的微生物所控制。土壤有机质呈现快速积累的趋势,120年样点的总有机碳(TOC)积累量为1.54 kg/ m2,积累速率为12.9 g/m2?yr,积累速率远高于年龄相近的其它土壤序列。 (3) 海螺沟冰川退缩迹地土壤母质中原生矿物磷的含量和组成均具有较高同质性。90%的原生矿物磷以磷灰石的形态存在,且能直接与土壤溶解接触,其余10%的原生矿物磷则被包裹于硅酸盐矿物中。土壤pH的快速降低导致原生矿物磷以较高速率被释放,120年样点的释放速率达到46 mmol/m2?yr。而被包裹于硅酸盐矿物中的磷尚未被释放。 (4) 冰川退缩12年内的土壤磷形态无显著变化,自30年开始,随着原生矿物磷的快速降低,生物有效磷和被次生矿物吸附的磷均显著增多,土壤有效磷在随后的各样点间起伏变化,其平均含量为TP的11%。有机磷含量快速增加,120年样点处已有40%的无机磷被转化为有机磷。 (5) 随着风化过程的进行,风化作用产物活性铝、活性铁及次生粘土矿物逐渐增多,活性铝和活性铁的含量在120年样点分别达到4.47和7.98 g/kg,对土壤磷形态和生物有效性产生了重要影响。次生铁氧化物是吸附无机磷的主要载体,而铁、铝化合物——有机质复合体对有机磷的固持是有机磷的主要存在形式。在80年和120年样点,植物导致土壤pH<5,有利于上述被次生金属矿物吸附和络合的磷形态的长期稳定存在。 本研究不仅可丰富对早期风化成土过程和机制的认识,而且对理解全球范围内因气候变暖而大量出现的年轻冰川退缩迹地上植被的发生和发育具有重要意义。
Other AbstractSoil phosphorus (P) bioavailability influences significantly vegetation primary succession. Plenty of information is available for the long-term variations and mechanism of soil P status. However, there is scarce knowledge on the evolution of soil P speciation and bioavailability on young soil chronosequences (<200 years), which is of importance to understand the relationship between soil P cycling and vegetation succession. The ultimate source of P is rocks weathering. Most current researches focus on the P biogeochemical processes in ecosystems after P is released from primary minerals, rare researches investigate the P releasing process and releasing rates. Moreover, amorphous metal compounds and secondary clay minerals generated by primary minerals weathering will impact P speciation and bioavailability. However, mechanism behind this kind of impact has not been revealed. Weathering of rocks in natural conditions takes a long time, hence it is hard to investigate this process under close-to-nature conditions in the laboratory. As a result, glacier foreland chronosequences with relative accurate age are ideal “natural laboratory” to investigate the processes and mechanisms of primary minerals weathering and P evolution with soil age. In the presented research, soil and water samples were collected at seven sites with different ages (0, 12, 30, 40, 52, 80, 120 years) in the Hailuogou Glacier foreland chronosequence on the eastern slope of Gongga Mt., southwest of China. Measurement in situ, Nezat mineral sequential extraction technique, hydrochemical analysis, X-ray Diffraction (XRD), X-ray fluorescence (XRF), a modified Hedley P sequential extraction technique and statistical analysis were utilized to (1) study processes of rock weathering, primary mineral P release and soil development; (2) evaluate the mineral weathering rates and P releasing rates; (3) study evolutions of soil P speciation and bioavailability during soil development; (4) find out relationships between mineral weathering and P releasing and evolution; and (5) reveal key mechanisms controlling rock weathering, P release and evolution in different weathering and pedogenesis stages. The results and conclusions are as followings: (1) The major components of parent materials are silicate minerals (91.3%) in the Hailuogou Glacier foreland chronosequence, while calcite only accounts for a little part of parent materials. The mineral compositions are homogeneous for parent materials. The weathering rate changes with soil age as a reverse parabola, whose minimum value occurs at 52 year-old site. The weathering rate at the 120 year-old site is 111 cmolc/m2?yr, which is higher than that in Alps and in some tropical zones. The rapid dissolution of calcite is the major reason for the high weathering rate at the 30 and the 40 year-old sites. The gradual dissolution of biotite, hornblende, and plagioclase causes the rebound of weathering rate after 52 year-old site. A huge number of fine minerals are produced by strong glaciation and freeze-thaw processes, which is the basis of the high chemical weathering rates in the Hailuogou chronosequence. Furthermore, adequate moisture and rapid succession of vegetation also facilitate the weathering processes. (2) The variations of soil profiles, exchangeable cations, the activated degree of Fe and Al, pH, accumulations of C and N with soil ages show that soil development is rapid for the Hailuogou chronosequence. The soil parent materials are nearly neutral or weakly basic at all sites. While the pH of A horizon decreases sharply with soil ages, which is lower than 5 at the 80 and the 120 year-old sites. The variations of pH are mainly regulated by the vegetation types. Soil organic matters accumulate rapidly with soil ages. The TOC pool (TOC in O horizon plus top 15 cm mineral soil) is 1.54 kg/m2 at the 120 year-old site and the TOC accumulation rate is 12.9 g/m2?yr. This rate is higher than that of soil chronosequences with
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/7867
Collection山地表生过程与生态调控重点实验室
Recommended Citation
GB/T 7714
周俊. 海螺沟冰川退缩迹地风化——成土过程与土壤磷形态研究[D]. 北京. 中国科学院研究生院,2014.
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