本報告乃研究蓮華池試驗集水區第三號內的森林土壤之分類。區內的兩土壤剖面,以土元I與Ⅱ(pedon I and Ⅱ)表示,分別育自第三紀頁岩與砂岩,分布於常綠混生濶葉林,亞熱帶氣候區的急陡坡(約69%)集水區內。 土元Ⅰ的剖面具有變遷B層(cambric B-horizon)的特徵,此育自頁岩的土壞含36至46%的黏粒。用蒸餾水測定的pH值,表土為4.2,至1.2m處已增至5.0。鹽基飽和度(中性醋酸銨法)低,且均不超過10%。X-射線繞射結果顯示,黏粒成分主要是間層水雲母-蛭石,幾乎無石英存在。表土坋粒的黏士礦物種類與黏粒相同,惟尚有少量的長石類或綠泥石,但是心土的坋粒含蛭石量並不顯著。強度風化的頁岩主要含石英及少量水雲母。育自頁岩的土元Ⅰ在分類上屬於正淡瘠弱育土(Typic Dystrochrept)。 土元Ⅱ剖面的位置與土元Ⅰ剖面相距不過100公尺,但是剖面形態相差很遠。土元Ⅱ具有淡色披覆層(ochric epipedon)及黏聚Bt層(argillic Bt horizon)。此為砂岩母質之土元,正可反映其質地之粗細上。土元Ⅱ的整個剖面,其含砂粒量皆超過60%。以蒸餾水測定的pH值,表土為4.4,至1m處增至4.8。鹽基飽和度亦低,皆不到10%(中性醋酸銨法)。 土元Ⅱ的黏粒成分的黏土礦物種類與土元I的相同,惟所含之間層水雲母-蛭石量較小。坋粒主含石英及少量的水雲母。此育自砂岩的土壤屬於正簡極育土(Typic Hapludult)。 此二土壤剖面均育自類似的氣候型,林相及地形,但是在分類上都分屬兩土綱,此或許是因為母質相異及發育年齡較輕之故。
Two forest soils, occurred in the Lien-hua-chi experimental watershed No. 3, were studied. These two soils, designated as pedons I and Ⅱ, have formed under an evergreen mixed hardwood forest and a subtropical climatic regime, from tertiary shales and sandstones, respectively, on about 69% slope in central Taiwan. Pedon I was characterized morphologically by developing a cambric B horizon. The clay content of of this shalederived soil varied between 36 and 46%. The pH increased from 4.2, at the surface to 5.0 at 1.2 m, as determined in water. The organic carbon content was 1.7% at the surface but decreased abruptly thereafter and remained low (ca. 0.3%) for the rest of profile. Its base saturation, measured with NH4OAc solution, was low and was less than 10% at all depth. The X-ray diffraction analysis showed that all clay fractions were dominated by interlayered hydromica-vermiculite with barely detectable levels of quartz. Silt fractions of surface horizon contained all the clay minerals that occurred in clay fractions with additional small quantities of feldspars and perhaps chlorites. But the silt fraction of subsoils contained insignificant amount of vermiculite. Ground powder of strongly weathered shale contained exclusively quartz and with minor quantities of hydromica. The soil dervied from shale was classified as Typic Dystrochrept. Pedon Ⅱ, located only about 100m apart from pedon I, was morphologically different. It had an ochric epipedon and an argillic Bt horizon between 50 and 80cm. The texture of this pedon was reflected by the nature of the parent material which was sandstone. It contained over 60% sand throughout the entire profile. The ph values, as measured in water, increased from 4.4 at the surface to 4.8 at 1 m. The organic carbon content decreased from 1.6% at the surface to 0.2% in the C horizon. The base saturation was also very low and was less than 10% (NH4OAc method). The clay fractions of pedon Ⅱ contained the same suites of clay minerals that were found in the Pedon I but with relatively less amount of interlayered hydromica-vermiculite. The silt fractions were quartz-rich with minor amount of hydromica. Pedon Ⅱ, derived from sandstone, was classified as ”Typic Hapludult.” These two soils were formed under similar climate, forest cover and topograpfic features but classified into different orders. It is believed that the differences in parent materials and relative young stages of formation explain the differences observed in these two soils.
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