Changes and Future Prediction in the Dynamics of Dissolved Organic Matter in Soils under Forest Ecosystems by Global Warming

为探讨全球变暖和气温升高对森林生态系统土壤O层溶解性有机质（DOM）的影响及其未来预测，对不同温度下培养80天的O层样品进行了水提取DOM的实验，并在“加温箱”条件下对O层淋洗液中的DOM进行了测定。选择了两个具有代表性的研究地点，一个是筑波大学川上林业实验站，那里是典型的以阔叶树为主的冷温带森林生态系统（Qercus Mongolia spp.）一个是生长在酸性棕色森林土壤（Dystric Cambisols）上的冷杉林，另一个是以针叶树（Abies spp.）生长在灰化土壤上（典型灰化土）。 ...更多信息 2003年至2005年期间，除冬季外，进行了“加温室”的模拟实验。结果表明：（1）培养80 d后，O层样品提取液中溶解有机碳（DOC）含量增加，尤其是15℃下的样品。培养后DOM中亲水性组分的比例增加，钙、镁、钾、钠、铝、铁等阳离子的提取量也增加。根据DOC在285nm处的吸光度、红外光谱和元素组成推断，DOC的化学结构发生了变化，表明饱和度较低的芳香碳含量增加。2）模拟“升温室”条件下，O层平均日温升高约0.5℃，这表明，较高的分解速率将是合理的，通过测量土壤呼吸速率的高温条件下，导致更多的芳香族组分的DOM释放检测。然而，在现场条件下，DOM的亲水性组分的比例没有明显的增加。3）温度的升高，可能是全球气候变暖的原因，使饱和度较低的酚类、富里酸类等芳香碳的DOM含量增加，通过对两个试验点的对比研究，认为：气候较冷的森林生态系统下，全球变暖对DOM的数量和组成的影响更为明显。通过本项目的研究，获得了全球变暖背景下森林生态系统DOM动态变化的基础知识。少

In order to investigate the changes and future prediction in the dynamics of dissolved organic matter (DOM) in the O horizon of soils under forest ecosystem due to global warming and temperature increase, DOM after an incubation experiments of O horizon samples under different temperatures for 80days extracted with water and also the DOM in the leaching solution from O horizon under the "Warming Chamber" made of plastics of acryl resins were subjected to the various analyses, especially their chemical composition.Two representative study sites were selected, one was the Kawakami Experimental Station of Forestry, University of Tsukuba where a typical cool temperate forest ecosystems composed of mainly broad-leaved trees (Qerccus Mongolia spp.) growing on an acid brown forest soils (Dystric Cambisols), and the other was the Oodarumi National Forest where a typical sub-frigid forest ecosystems composed of mainly needle-leaved trees (Abies spp.) growing on a podzolic soils (Typic Podzols). … More The simulated experiment for the "Warming Chamber" was conducted during the period from 2003 to 2005 except for winter times. The results obtained were as follows.1)Concentration of dissolved organic carbon (DOC) in the extracts of O horizon sample increased after the incubation for 80days, especially for the samples under 15℃. The proportion of hydrophilic components of DOM also increased after the incubation as well as extracted cations including calcium, magnesium, potassium, sodium, aluminum and iron. The changes in the chemical structure were inferred from the absorbance at 285nm per DOC,IR spectra and elemental compositions, suggesting the increase in the aromatic carbon with lower "saturation degree".2)DOC concentration in the leaching solutions increased for the sites under simulated "Warming Chamber" where about 0.5℃ increase in the mean day temperature was observed in the O horizon, suggesting that the higher decomposition rate would be plausible as detected by the measurement of soil respiration rate for the elevated temperature conditions resulting in the release of more aromatic components of DOM. However the increase in the proportion of hydrophilic components of DOM was not clearly detected in the field conditions. Moreover changes of soil properties were observed especially for those in the surface horizons.3)The increase in temperature, possibly global warming, increase the amount of DOM of aromatic carbon with lower "saturation degree" like phenol and fulvic acids-like substances, and lead to the changes in the properties of soils of surface horizons.From the comparative study on the two study sites mentioned above it is suggested that the effect of global warming on the amounts and the composition of DOM would be more apparent in the areas under the forest ecosystems of cooler climate. Thus the fundamental knowledge on the dynamics of DOM from forest ecosystems under prevailing global warming was obtained through this project. Less