福山永久樣區優勢樹種凋落物養分釋出及土壤氮礦化之季節性變動

Nutrients Release from Leaf litter Decomposition of Dominant Tree Species and the Seasonal Soil Nitrogen Mineralization in Fushan Permanent Research Site

張至懿(Chih-Yi Chang)

指導教授 ： 陳尊賢

國立臺灣大學/生物資源暨農學院/農業化學研究所/碩士(2008年)

https://doi.org/10.6342/NTU.2008.01942

摘要

凋落物是有機物循環的基礎，提供森林土壤有機質及礦物質養分，經由植物吸收的養分會釋放回土壤中，因此凋落物的分解在森林養分循環扮演極重要的角色。氣候、土壤性質、微生物族群以及凋落物性質皆會影響凋落物的分解速率。凋落物的組成以落葉佔最高比例，而落葉的養分含量亦是所有凋落物中最高的。本研究目的為研究福山25公頃永久樣區山頂和全區主要優勢樹種之凋落物分解速率、有效養分元素釋出之速率，及主要優勢樹種分布之土壤氮礦化速率與季節性變動。
本研究於2006年10月，在山頂及麓坡各設置三個重覆樣區，山頂樣區各放入十二個凋落物分解袋(以山頂十種優勢樹種百分比配置)，麓坡樣區亦放入十二個凋落物分解袋(以全區十種優勢樹種百分比配置)。自2006年10月起，於不同時間到樣區取回一袋，分析其質量和元素的變化，前後共一年六個月的時間；土壤氮礦化之現地孵育以Lemée的土環法來測定，亦採集土壤回實驗室進行室內定溫孵育。
研究結果顯示山頂和全區優勢樹種初始凋落物養分濃度只有鉀、鈣、鎂、錳有顯著差異(p <0.05)，碳、氮、磷、鈉、鐵、銅、鋅則無顯著差異。全區凋落物分解速率高於山頂優勢樹種凋落物分解速率，這可能是與凋落物養分組成及分解環境有關，而大多數養分隨凋落物質量損失而釋放，鉀和鈉在分解的第一個月質量已釋出超過50%；鋅和鐵至試驗過程最後仍呈累積的現象。另於2006年10月 (降雨最多)、2007年4月 (降雨較少)及7月 (氣溫最高) 進行現地土壤氮礦化孵育試驗，結果顯示土壤溫度與現地氮礦化速率有顯著相關(p <0.05)，土壤溫度越高，氮礦化速率越快。實驗室長期孵育試驗的結果顯示，麓坡樣區有較大的氮礦化潛力。

關鍵字

福山永久樣區 ； 凋落物分解 ； 養分釋放 ； 土壤氮礦化 ； 氣候

並列摘要

Litter is the main source of soil organic matters, it provides organic matter and mineral nutrients for forest ecosystem. More than half of nutrient will be returned to the soil system, therefore, the litter decomposition is one of major role of nutrient cycle in forest ecosystem. Climate, soil properties, microbe populations and litter quality may affect the decomposition rate of litter. Leaf litter is the major part of litter components. The objectives of this study are to understand (1) the rate of leaf litter decomposition and bioavailability nutrients released from summit and whole site of dominant tree species, and (2) the soil mineralization rate of different dominant tree species and their seasonal changes in Fushan Permanent Research Site.
The research sites located in summit and footslope are divided into 3 replicated sites, since October, 2006. Twelve litterbags putting on the summit site were made up based on the composition of leaf litter of ten dominant tree species distributed in the summit region. Twelve litterbags putting on the footslope site were made up based on the composition of leaf litter of ten dominant tree species distributed in the whole region. One litterbag located in each site was sampled back to laboratory to weigh its mass and analyze their nutrient changes in every two weeks to one month or more time in the last stages. Field incubation of soil mineralization was also monitored by soil core method, and the soils were also sampled for laboratory incubation to compare the differences between two methods.
The results showed that there are significant differences of K, Ca, Mg, Mn content in leaf litter of dominant tree species distributed in summit region and whole site in Fushan Permanent Research Site (p <0.05), but there are no significant differences for C, N, P, Na, Fe, Cu and Zn. The decomposition rate in the leaf litter of whole site dominant tree species is faster than that of leaf litter of summit region, it may be related to the initial concentration of litter and environmental conditions. Most of nutrients were released by the loss of mass. More than 50% of K and Na in leaf litter are released during the first month of decomposition experiment in site. Zn and Fe of the leaf litter content are slightly accumulated until the end of decomposition experiment. Field incubations of soil nitrogen mineralization were monitored in the site in October of 2006 (the highest amount of rainfall of the year), March of 2007 (the lowest amount of rainfall of the year), and July of 2007 (the highest temperature of the year). The results indicated that soil nitrogen mineralization rates are related to soil temperate. The results of laboratory incubation also indicated that the soils sampled from the footslope region have more potential soil nitrogen release.

並列關鍵字

Litter decomposition ； Fushan Permanent Research Site ； nutrient release ； soil temperature ； soil nitrogen mineralization

參考文獻

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