模拟氮沉降对温带森林凋落物分解的影响

森林凋落物的分解是生态系统养分循环的重要过程,以北京西山地带性植被栎树林（辽东栎：Quercus liaotungensis）为对象,主要研究温带森林植物凋落物分解对模拟氮沉降的响应,为更好地了解氮沉降对温带森林地区凋落物的分解过程提供参考.通过模拟氮沉降,研究不同形态氮（硝态氮、铵态氮和混合态氮）和不同水平氮沉降（对照0 kg·hm^-2·a^-1、低氮处理50 kg·hm^-2·a^-1 和高氮处理150 kg·hm^-2·a^-1）对凋落物分解的影响,在2 年的时间内调查分析了凋落物分解过程中质量损失动态和碳（C）、N 含量及w（C）/w（N）比值的变化.研究结果表明,氮沉降均使凋落物分解速率减缓,且随氮沉降剂量增加,凋落物分解速率相比对照分别减慢了9.88%（硝态氮低氮）、15.02%（硝态氮高氮）、11.46%（铵态氮低氮）、14.62%（铵态氮高氮）、13.04%（混合态氮低氮）和16.20%（混合态氮高氮）.且不同氮沉降类型、不同氮沉降水平间差异显著.不同形态、不同水平的氮沉降显著地增加了凋落物N 含量（P=0.061,P=0.087）,其中混合态氮沉降对凋落物中N 素含量增加最显著（P=0.044）.但在分解过程中,各处理均未对凋落物C 含量产生显著影响.不同水平的氮沉降显著降低了凋落物的w（C）/w（N）比值,而且不同类型不同水平氮沉降对凋落物w（C）/w（N）比值具有显著的交互作用（P=0.011）.综上所述,通过对模拟氮沉降后凋落物残留率等的变化分析,得出氮沉降对温带森林凋落物的分解产生了抑制作用.

Effects of Simulated Nitrogen Deposition on Temperate Forest Litter decomposition

In the recent decades, human activities have more influence on the global ecological cycle, leading to the atmosphericchange and the increases in N deposition. Litter decomposition is a crucial process in the cycling of ecosystem elements. Taking theQuercus liaotungensis in Beijing west-mountain area as the research object, a field experiment was conducted to investigate theresponses of litter decomposition to simulated N deposition. This provides reference to get a better understanding of nitrogendeposition on litter decomposition process of temperate forest. This paper indicated how three different N forms （NO3^--N, NH4^＋-Nand mixed N） and three N input levels （Control N 0 kg·hm^-2·a^-1、low N 50 kg·hm^-2·a^-1 and high N 150 kg·hm^-2·a^-1） effect on litterdisposition. Within 2 years, we have investigated and analyzed the dynamic changes of mass loss, C＆N content and w（C）/w（N） valueduring the litter decomposition process. The data suggested that, three different levels of N input all slowed the litter decompositionrate inordinately. With the increase of N addition, the litter decomposition rate, compared with the contrast, has slowed 9.88% （lownitrate N）, 15.02% （high nitrate N）, 11.46% （low ammonium N）, 14.62% （high ammonium N）, 13.04% （low mixed N） and 16.20%（high mixed N） respectively. There is significant difference among different forms or different levels of N addition. They all play asignificant role in promoting the N content in litter （P=0.061, P=0.087）, in which mixed N addition has the most significant effect onthe N content in the litter （P=0.044）. But in the process of decomposition, the treatments had no significant effect on the C content inlitter. Different levels of N addition significantly reduced the w（C）/w（N）ratio in litter. The different levels and types of N additionhave significant interaction effect on the litter w（C）/w（N） values （P=0.011）. After simulated nitrogen deposition, the analysis of thelitter residual