水分和温度对挪威云杉林枯枝落叶层浸提液pH值的影响

Influence of Water Content and Temperature on the pH values of Solution Extracted from Acidified Forest Floor Materials of Norway Spruce

在室内控制条件下研究了含水量和温度对富含ＮＨ＋４的严重酸化挪威云杉林枯枝落叶层物质饱和浸提液ｐＨ值的影响，包括未分解层ＯＬ、半分解层ＯＦ和已分解层ＯＨ，在为期１ａ的实验期间内没有元素的输入、淋失和根系吸收，但可相对自由地进行气体交换。实验分４个水分处理（从几乎风干到各种被分解物的饱和含水量）和３个温度处理（年均温度分别为１１．６、１２．３、１４．５℃）。干旱使枯枝落叶浸提液ｐＨ值明显下降，极端干旱条件下Ｈ＋饱和浸提量为初始值的２．２～２．７倍。为避免ｐＨ值急剧下降，枯枝落叶层的含水饱和度应维持在６０％～８０％。如果ＯＬ的含水饱和度小于３０％，ＯＦ和ＯＨ小于５０％，则浸提液ｐＨ值低于初始值。干旱条件下，富含ＮＨ＋４的酸化枯枝落叶也会发生氨挥发，并且在ｐＨ值下降中起着十分重要的作用。在应用温度范围内。

The influence of temperature and water content during incubation on the pH values of solutions extracted with saturated water content from the strongly acidified and NH + 4 riched forest floor materials (O L ,O F and O H layers) of Norway spruce was investigated under manipulated conditions for one year. During the incubation there were no element input,element leaching and plant uptake,but the gas exchange with the atmosphere was relatively free. There were 3 temperature treatments (with annual average air temperature of 11.6,12.3 and 14.5 ℃ respectively) and 4 water content treatments (from nearly air dry to the saturation of each material). Drought led to a significant decrease of pH value. In the extreme drought treatment,the extracted H + amounted to 2.2～2.7 times of that of the starting phase. In order to avoid a sharp decrease of pH value,a saturation degree of 60%～80% for the forest floor materials should be maintained. If it is smaller than about 30% for the O L and 50% for the O F and O H material,the pH value will be lowered compared with the starting phase. Surprisingly,ammonia volatilization can take place under drought conditions,even in the strongly acidified forest floor materials which have a high content of NH + 4. Furthermore,ammonia volatilization plays the most important role in the decrease of pH value. On the contrary the influence of warming was not significant in the applied temperature range.