Soil development on moraines of Mendenhall Glacier, southeast Alaska .2. Chemical transformations and soil micromorphology
Soil development on moraines of Mendenhall Glacier, southeast Alaska .2. Chemical transformations and soil micromorphology
复制标题
DOI：
10.1016/0016-7061(96)00022-5
复制
发表时间：
1996-07-01
期刊：
影响因子：
6.1
通讯作者：
Alexander, EB
中科院分区：
文献类型：
--
作者：
Burt, R;Alexander, EB
在阿拉斯加东南部的门登霍尔冰川全新世时代的冰碛上的土壤范围从形态上不发达的土壤具有现场确定的灰土层，更强烈地表达随着土壤年龄的增加。有机碳在这些土壤中迅速积累，38年内形成O层，有机碳与阳离子交换量（R（2）= 0.92）、可变电荷（R（2）= 0.94）、可提取酸度（R（2）= 0.83）和1500 kPa持水量（R（2）= 0.97）。10年生土壤pH值为酸性，pH（H_2O）为5.0 ~ 6.4。连二亚硫酸盐-柠檬酸盐、焦磷酸钠和草酸可提取的铁（Fe-O）的增加在> 240年的土壤中最为明显。这些测得的属性在pedons的深度趋势是最独特的铁-O增加从表面矿物层（A或E）的底层地平线在所有pedons。在B层中，Fe-o/Fe-d比值随土龄的增加而增加，在170年生的土壤中，E层的Fe-o/Fe-d比值在0.3 ~ 0.5之间，紧接着的B层的Fe-o/Fe-d比值在0.4 ~ 0.83之间。水铝英石含量较低（小于或等于6 g kg（-1）），在这些pedons，并没有一致的增加，随着土壤年龄。酸性草酸盐抽提物（ODOE）光密度和Al-o + 1/2Fe-o是指示灰岩发育的敏感和一致的化学指标。在B层，ODOE随土龄的增加而增大（0.06 ~ 0.56）。在B层（1.2 ~ 4.5 g kg（-1））和从E层到B层的土壤中，Al-o + 1/2 Fe-o也随土龄的增加而增加。随着土壤年龄的增长，E层的非封闭性钙结合磷（195 ~ 49 mg kg（-1））和全磷（700 ~ 300 mg kg（-1））相对于下层降低。年轻的pedons的表面视野主要是未涂覆的沙子大小的颗粒与有机成分很少的聚合物。早期淋溶过程的证据是蚀刻的矿物颗粒在E层的70岁的土壤。除了> 240年的古土壤的BC层外，这些土壤中没有铁氧化物积累的光学证据。这一时序研究表明，该地区的土壤中，在一个相对较短的时间内实现了spodic的发展。
Soils on Holocene-age moraines of the Mendenhall Glacier in southeast Alaska range from morphologically undeveloped to soils having field-identified spodic horizons that are more strongly expressed with increasing soil age. A soil chronosequence was sampled to study development of spodic features and to compare the expression of these features with chemical and micromorphological properties, Organic C accumulates rapidly in these soils, with O horizons forming within 38 yr, Organic C is highly correlated with cation exchange capacity (R(2) = 0.92), variable charge (R(2) = 0.94), extractable acidity (R(2) = 0.83), and 1500-kPa water retention (R(2) = 0.97), The pH of the IO-yr old pedon is acidic with a soil pH (H2O) ranging from 5.0 to 6.4, The pH decreases with soil age, with the lowest pH in horizons at the organic/mineral contact. Increases in dithionite-citrate, sodium pyrophosphate, and acid-oxalate extractable Fe (Fe-o) are most evident in the > 240-yr old soil. Depth trends for these measured properties within pedons are most distinctive for Fe-o which increases from surface mineral horizons (A or E) to underlying horizons in all pedons. The Fe-o/Fe-d ratio increases with soil age in B horizons, and in pedons 170 yr, this ratio ranges from 0,3 to 0.5 in the E horizons and from 0.4 to 0.83 in B horizons immediately below, These data indicate a greater proportion of poorly crystalline Fe in illuvial horizons with increasing soil age. Allophane content is low (less than or equal to 6 g kg(-1)) in these pedons, and there is no consistent increase with soil age. The optical density of acid-oxalate extract (ODOE) and Al-o + 1/2 Fe-o are sensitive and consistent chemical indicators of spodic development. The ODOE increases with soil age in B horizons (0.06 to 0.56). The Al-o + 1/2 Fe-o also increases with soil age in B horizons(1.2 to 4.5 g kg(-1)) and within pedons from E to B horizons. Nonoccluded Ca-bound P (195 to 49 mg kg(-1)) and total P (700 to 300 mg kg(-1)) decrease in E horizons relative to underlying horizons with soil age. Surface horizons of the younger pedons are predominantly aggregates of uncoated sand-sized grains with few organic constituents. Early processes of eluviation are evidenced by the etching of mineral grains in the E horizon of the 70-yr old pedon. There is no optical evidence of Fe-oxide accumulation in these soils, with the exception of the BC horizon of the > 240-yr old pedon. This chronosequence study indicates that spodic development is achieved within a relatively short period of time in soils of this region.