關刀溪三種不同森林生態系土壤和土壤水中無機離子

Inorganic ions of soil and soil solution in three different stands of Kuandaushi forest ecosystem

本試驗主要探討關刀溪森林生態中人工杉木林、次生闊葉林及天然闊葉林等三種林分之土壤及土壤水中無機陰陽離子含量變化，以及pH與鋁、鐵離子之相關性。分別於三種林分內，依15- 20、30-35及60-65 cm三種深度，採取土樣，並檢測其化學性質；另於相同深度，設置重力水及張力水取樣裝置，每個月收取水樣並分析無機陰陽離子濃度。三種林分土壤的pH值均隨土壤深度增加而增加，大多數無機離子在上層土壤含量最高。土壤鋁離子含量大於鐵離子含量達10倍以上，不同深度土層間鋁、鐵離子濃度差異不顯著。土粒所鍵結之有效性鐵，在此三種林分間差異不大，但游離於土壤溶液中之Fe2+或Fe3+，則以天然闊葉林濃度較高。三種林分土壤張力水之無機離子濃度大多高於重力水，各種無機離子濃度與土層深度之變化無一致趨勢。天然闊葉林之重力水與張力水的無機離子濃度，受乾溼季之影響較其他二種林分為大，並呈現顯著之差異。 Al3+、Fe2+與Fe3+濃度多是張力水高於重力水，而土層間之差異多不顯著； pH與Al3+、Fe2+或Fe3+離子之間無顯著相關。土壤水所呈現Ca2+/Al3+、Mg2+/Al3+、（Ca2++Mg2+） /Al3+或（Ca2++Mg2++K+ ） /Al3+之莫耳濃度比皆大於1.0，顯示關刀溪森林生態系土壤水的鋁濃度尚未達傷害植物之程度。 The purpose of this study was to investigate the variation of the concentration of inorganic ions in soil and soil solution, the relationships between pH and aluminum or iron in three different stands, including China-fir plantation, secondary hardwood and natural hardwood. Soils were sampled from depths of 15-20 cm, 30-35 cm and 60-65 cm, and the chemical properties were determined. Furthermore, the equipments of zero-tension lysimeter and tension lysimeter were established in the same soil depths. The samples of soil solution were collected every month, and then analyzed the concentration of cations and anions. Soil samples from top layer of the three different stands had higher inorganic ion content. The content of aluminum was 10 times higher than iron and had no significant difference among three depths of soil. The iron content of soil was no significant difference among the three different stands, however, the concentration of Fe2+and Fe3+ in soil solution was the highest in natural hardwood. The concentrations of many kinds of inorganic ions in tension lysimeter were higher than those in zero-tension lysimeter, and had no similar trend toward soil depths. The effects of dry and wet seasons on inorganic ion concentrations of soil solution in natural hardwood were higher than in other stands. The Al3+, Fe2+ and Fe3+ concentrations were higher in tension lysimeter than in zero-tension lysimeter, and have no significant difference among all soil depths. The Ca2+/Al3+, Mg2+/Al3+, (Ca2++Mg2+) /Al3+, and (Ca2++Mg2++K+) /Al3+ molar ratio were above 1.0 in soil solution of the three different stands, indicating that aluminum concentration had not yet inhibited plant growth.