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下土壤O层溶解有机质（DOM）动态的影响及未来预测，对不同温度下O层样品用水提取80天后的DOM和在丙烯酸树脂塑料“暖室”下O层浸出液中的DOM进行了各种分析。尤其是它们的化学成分。选取了两个具有代表性的研究点，一个是筑波大学川上林业实验站，这里是生长在酸性棕色森林土壤（Dystric Cambisols）上以阔叶树（Qerccus Mongolia spp.）为主的典型寒带森林生态系统，另一个是Oodarumi国立森林，这里是生长在灰化土（typicpozzols）上以针叶树（Abies spp.）为主的典型亚寒带森林生态系统。除冬季外，“暖室”的模拟实验在2003 - 2005年期间进行。所得结果如下：1) O层样品浸提液中溶解有机碳（DOC）浓度在培养80天后有所升高，特别是在15℃条件下。培养后DOM的亲水性成分比例也有所增加，同时提取出钙、镁、钾、钠、铝、铁等阳离子。化学结构的变化由每个DOC的285nm吸光度、红外光谱和元素组成推断，表明“饱和度”较低的芳香碳增加。2)在模拟“暖室”条件下，0层平均日温升高约0.5℃，浸出液中DOC浓度升高，表明土壤呼吸速率的测量表明，温度升高导致DOM释放更多芳香烃成分，浸出液中DOC的分解速率较高。但在田间条件下，DOM亲水组分比例的增加未被明显检测到。此外，土壤性质也发生了变化，特别是表层土壤。3)气温升高，可能是全球变暖，使“饱和度”较低的芳香族碳如苯酚、黄腐酸类物质DOM的含量增加，导致表层土壤性质发生变化。从上述两个研究点的对比研究可以看出，在气候较冷的森林生态系统下，全球变暖对DOM数量和组成的影响更为明显。因此，通过该项目获得了全球变暖背景下森林生态系统DOM动态的基本知识。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