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

为了研究全球变暖和气温升高对森林生态系统O层土壤溶解有机质(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80d后的DOM以及用丙烯树脂塑料制成的保温箱中O层淋洗液中的DOM进行了各种分析，特别是化学成分的分析。另一种是乌达鲁米国家森林，其典型的亚寒带森林生态系统主要由针叶乔木(Abies spp.)生长在泥土上(典型的泥土)。…在此基础上，对“增温室”进行了除冬季以外的2003年至2005年的模拟实验。结果表明：1)培养80d后，O层样品提取液中的溶解有机碳浓度有所增加，尤其是15℃以下的样品。DOM的亲水性组分以及提取的钙、镁、钾、钠、铝和铁等阳离子的比例也有所增加。从DOC285 nm处的吸光度、红外光谱和元素组成推断出化学结构的变化，表明饱和程度较低的芳香碳的增加。2)模拟“暖箱”中的DOC浓度增加，在O层观察到平均日温度增加约0.5DOC的地点，通过对土壤呼吸速率的测量，表明较高的分解速率是可能的，因为高温条件下土壤呼吸速率导致DOM释放更多的芳香成分。然而，在现场条件下，DOM的亲水组分比例没有明显增加。3)气温升高，可能是全球变暖，增加了苯酚、类黄腐酸类物质等饱和度较低的芳香碳的DOM含量，并导致表层土壤性质的变化。从上述两个研究点的对比研究可以看出，全球变暖对DOM数量和组成的影响在气候较凉爽的森林生态系统下更为明显。因此，通过该项目获得了关于全球普遍变暖情况下森林生态系统中DOM动态的基本知识。较少

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