|杨子江1,2; 邴海健1; 周俊1; 吴艳宏1; 孙宏洋1; 罗辑1; 孙守琴1; 王吉鹏1,2|
|Other Abstract|| Weathering of bedrocks releasing mineral elements into the pedosphere is the starting point of global element recycling. Therefore, the knowledge of the variation of soil minerals in the soil with the soil forming process and its mechanism is the basis for understanding soil weathering and development. Since the end of the Little Ice Age, the glacier at Hailuogou on the east slope of the Gongga Mountains, Sichuan, China has been retreating continuously, leaving bottom moraines exposed to weathering and soil forming. Then the area is invaded successively by Hippophae rhamnoides L, Populous purdomii Rehder, Abies fabri, and Picea brachytyla, forming a 120 year soil development sequence and plant succession sequence. Besides, the area also contains a rich accumulation of climate data and geological structure data. In this study, six sampling sites were set up in this area, representing 0 yr, 30 yr, 40 yr, 52 yr, 80 yr and 120 yr after the retreat of the glacier, for sampling of soil in the humus horizon and parent material horizon. The soil samples were air-dried and ground to pass a chosen sieve for X-ray diffraction (XRD) analysis (organic matter was removed with H2O2 in pretreatment) to determine qualitatively and quantitatively soil minerals therein in a view to analyzing mineral composition of the soil parent material along the soil chronosequence and variation of the soil minerals with soil development.|
XRD analysis shows that the soil parent material horizon in the area is quite homogenous, and soil minerals are dominated with silicates (about 90%), including quartz (24.5%), plagioclase (28.5%), K-feldspar, augite, hornblende, biotite, chlorite and vermiculite, and some carbonates, like calcite (< 8%) and dolomite (< 2.3%), and phosphate mineral apatite (< 2.1%). However, in some soil samples, some other minerals like pyrite, barites, calcium oxalate, wollastonite and smectite are also detected. The soil in the area is fairly high in content of feldspar, mica and hornblende, which is the feature of entisol. As the pedogenesis proceeds, after 52 years of exposure, calcite in the parent material begins to transform into calcium oxalate. After about 120 years of exposure, biotite or hornblende is very likely to transform into biotite or hornblende, reducing its content in the soil. The soil in the humus horizon is relatively enriched in felsic minerals (quartz, plagioclase and K-feldspar). Correlation analysis shows that the contents of hornblende, apatite, biotite and chlorite decreased significantly with soil development (p<0.05). Surface vegetation biomass and soil pH are two important factors influencing weathering of surface soil. Plant growth and succession not only directly promotes weathering of the minerals in the surface soil, but also speed up, weathering of hornblende, biotite and chlorite along the soil chronosequence by reducing soil pH. And what is more, only when soil pH is dropped down below 5.5, will it accelerate weathering of apatite. In the end, by comparing the Hailuogou Soil Chronosequence with two similar soil chronosequences in the Alps, this paper deduces that mineral composition of the soil forming parent material may affect development of surface vegetation. The high contents of mafic minerals and apatite in the parent material as well as the warm and cool climate are responsible for the flourishing vegetation along the Hailuogou chronosequence. All the findings and data indicate that apparent weathering occurred at the early soil development stage of the Hailuogou Soil Chronosequence.
|Keyword||土壤矿物 早期风化过程 土壤序列 冰川退缩区 X射线衍射分析|
|First Author Affilication||中国科学院水利部成都山地灾害与环境研究所|
|杨子江,邴海健,周俊,等. 贡嘎山海螺沟冰川退缩区土壤序列矿物组成变化[J]. 土壤学报,2015,52(3):507-516.|
|MLA||杨子江,et al."贡嘎山海螺沟冰川退缩区土壤序列矿物组成变化".土壤学报 52.3(2015):507-516.|
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