摘要
对莽山北坡不同海拔高度的5个土壤剖面15个土样的粘粒矿物进行了X射线衍射分析和粘粒氧化物的化学选择溶提测试,结果表明:(1)莽山土壤中粘粒矿物组合的垂直变化明显。海拔500m以下的红壤、黄红壤的粘土矿物以1:1型高岭为主,粘粒氧化物中有较多的晶质氧化铁和热碱溶性氧化硅。海拔850m以上的黄壤、暗黄棕壤和山地灌丛草甸土的粘土矿物以2:1型的14×10^(-10)m过渡矿物和水云母为主,粘粒氧化物中有较多的无定形氧化铁、铝和三水铝石。(2)随海拔升高,土壤粘粒的硅铝率、氧化铁的游离度变幅不大,而氧化铁的活化度和各种氧化铝的富集明显提高。根据这些结果,结合莽山土壤的风化威土的条件与过程,讨论了莽山垂直带土壤中粘土矿物和氧化物的分布与演化过程的特点。
Mangshan is a granitic mountainous region which is located at 24°54′—25°03′ north latitude and 112°43′—113°20′ east longitude. The altitude of the highest mountain peak is 1902 meters. The examined soil samples were collected fron different altitudes. The layer-silicate minerals and the oxides of clay-size minerals of fifteen soil samples in five soil profiles on the north slop of the Mangshan Mountains in Hunan Province were studied by X-ray diffraction analysis and chemical selective solvent extraction analysis respectively.The results indicate that: 1) the vertical change of the layer-silicate minerals and the oxides of clay-size mineral for soils situated at various altitudes on the north slop of the Mangshan Mountains was quite clear. For red soil and yellow-red soil distributed at an altitude below 500 meters, the major clay mineral was kaolinites and there was a certain amount of 14×10^(-10)m intergrade minerals and hydromicas. The contents of crystalline iron oxide and hot alkaliscluble silica in the oxides of clay-size minerals were higher, while those of amorphous iron aluminum oxides and gibbsites lower. For yellow soil, dark yellow-brown soil and mountain shrubby-meadow soil distributed above 850 meters in altitude, the predominant clay mineral was 14×10^(-10)m intergrade minerals and hydromicas and, there was a certain amount of kaolinites and a few chlorites. The amorphous iron, aluminum oxides and gibbsites were more, where as the crystalline iron oxides and hot alkali-soluble silica were less in oxides of clay-size minerals; 2) with the increase of elevation, the changes in the content of free iron oxide (from 5.17% to 4.73%), and in the free degree of iron oxide (from 71% to 66%), as well as in the silicaalumina ratio (from 1.84 to 2.08) in clay fraction of examined soils were not so great except for mountain shrubby-meadow soil. However, the increase of activity of iron oxide was obvious, whereas the content of hot alkali-soluble silica declined evidently; and 3) the amount of amorphous aluminum oxide, aluminum oxide extracted by dithionite citrate bicarbonate sodium solution and gibbsite of clay fraction in soil increased obviously with the increase of elevation. it implied that the enrichment of aluminum in soil clay fraction incerased with the elevation.According to the results mentioned above and the comprehensive analysis of soil-forming conditions of the Mangshan Mountains, the peculiarity of evolution for layer-clay minerals and oxides of clay-size minerals in the soils with the increase of elvation, could summarizde as follows: 1) the weathering desilicification of the transition of 2: 1 type minerals to 1: 1 type minerals becomes weaker whereas the eluviation-dekalifivation and interlayer hydrooxylation of the transition from primary minerals to hydromica and 14×10^(10)m intergrade mineral become stronger; 2) the ageing of iron oxide becomes slower, but its activation and activity are enhanced; and 3) the enrichment and activation of aluminum oxide in soil clay fraction are strengthen. The enrichment of aluminum in the soils distributed at the high altitude of the Mangshan Mountains results mainly from the leaching loss of base and silica under conditions of low temperature, high moisture and complex or chelation eluviation of organic acid.
出处
《土壤学报》
CAS
CSCD
北大核心
1992年第1期48-56,共9页
Acta Pedologica Sinica
基金
高校博士点基金
