【摘要】 凋落物的养分释放是生态系统养分循环的重要组成部分,是维持森林生态系统养分平衡的关键过程。近几十年来,森林生态系统正受到氮沉降增加的影响,开展氮沉降全球化背景下凋落物养分释放的研究,有助于揭示森林养分循环对氮沉降的响应机制。以亚热带有代表性的杉木（Cunninghamia lanceolata）人工林（福建官庄国有林场1992年造林）为研究对象,自2004年1月开始进行氮沉降模拟试验,设置4个氮沉降处理,分别为0（N0）、60（N60）、120（N120）、240（N240）kg·hm^-2·a^-1,采用分解袋法进行原位分解试验,将分解袋随机投放至林地表面,每隔60天取样1次,共持续660 d,探讨凋落物叶在分解过程中养分（P、K、Ca、Mg、Mn、Zn、Fe）的释放动态。结果表明,在模拟氮沉降初期,氮沉降总体上促进了养分元素的释放,相对于N0处理,氮沉降分别使K的周转期缩短22.14%-26.09%,Ca周转期缩短15.31%-34.59%,Mg的周转期缩短5.25%-27.03%,Mn的周转期缩短17.85%-46.80%,Zn的周转期缩短20.51%-33.18%;就P和Fe而言,仅有N₂处理对其表现为促进作用,周转期分别缩短11.02%和26.01%。在各氮沉降水平中,120 kg·hm^-2·a^-1的施入量对凋落物养分释放作用最显著,说明此时杉木人工林还未达到氮饱和状态,随着时间的推移,当杉木人工林生态系统达到氮饱合时,则有可能对凋落物的养分释放产生不利的影响。更多还原

【Abstract】 Nutrient release of litterfall represents an important component of nutrient cycle in ecosystems, which is a key process to maintain nutrient balance for forest ecosystem. Over the past few decades, forest ecosystem has been affected by increasing nitrogen deposition. Therefore, studies on nutrient release of litterfall under nitrogen deposition is helpful to reveal mechanism of forest nutrient cycle in responses to nitrogen deposition. In this study, a field experiment was initiated in January 2004 in a Cunninghamia lanceolata plantation, which was located at Guanzhuang National Forestry Farm in subtropical region of China. Simulated N deposition treatment（N0, N1, N2 and N3） was designed as 0, 60, 120 and 240 kg·hm^-2·a^-1, respectively. Nutrient dynamics during leaf litter decomposition were investigated by using litterbag method. Litterbags were randomly placed on the surface of soil and collected from each plot at 60-days intervals for 660 days. Results showed that nitrogen deposition promoted nutrient release.Compared with N0 treatment,the turnover period（decomposition 95% in years） of K, Ca, Mg, Mn, and Zn was shortened by nitrogen deposition by 22.14%-26.09%, 15.31%-34.59%, 5.25%-27.03%, 17.85%-46.80%, and 20.51%-33.18%, respectively.However, only N₂ treatment had a positive effect on release of P and Fe with the turnover period shortened by 11.02% and 26.01%.We found that high nitrogen input such as 120 kg·hm^-2·a^-1 had a significant effect on nutrient release of litterfall, indicating that Cunninghamia lanceolata plantation studied had not reached the status of nitrogen saturation at that time. If the rate of nitrogen deposition increases in future, nitrogen saturation might occur in this Cunninghamia lanceolata plantation ecosystem and thus would have negative effect on nutrient release of litterfall.更多还原