【作者】 廖艳；

【导师】 杨忠芳；

【作者基本信息】 中国地质大学（北京） ， 地球化学， 2011， 博士

【摘要】 气候寒冷地带的低温条件使土壤易于积累有机碳,从而具有较高的土壤有机碳密度;另一方面,低温地带的气候变暖幅度要明显大于温暖的地区。因此,本论文选择我国典型低温区进行土壤碳库变化和土壤呼吸敏感性的研究。采用全国多目标区域地球化学调查数据对土壤碳库储量进行了估算,结合历史数据分析了土壤碳库的时空变化,并从自然和人为两方面分析了其变化原因。在实验室进行了土壤呼吸实验,对低温区土壤呼吸特征和温度敏感性特征进行了探索,以更好地认识低温地区土壤碳库在气候变暖的条件下如何响应于温度的变化。此外,还采用3种实验方法进行了土壤有机碳不同组分的划分。主要的研究结果如下:第一,松嫩平原北部表层土壤总体上为碳源,其释放碳的平均值为1479 t/km2,20年间土壤潜在碳排放总量为0.20 Gt,与化石燃料排放量0.21 Gt相当;其中由气温上升、土地利用和水土流失造成的土壤碳库排放值分别为0.11 Gt、0.09 Gt和0.19 Mt。在现有耕作和土地利用方式下,松嫩平原固碳潜力为负值。第二,吉林中西部地区同样为碳源,有机碳以0.199 tC ha-1·a-1的年变化速率由土壤排放进入大气中。在影响因素中,LUCC带来的是土壤碳的固存,吉林中西部碳库变化受温度变化并不大,但与降水存在明显的相关性,这能大致解释土壤有机碳密度在空间分布上西北低、东南高,由西北向东南逐渐增大的趋势。第三,不同土地利用类型土壤呼吸强度对温度升高存在着显著的正反馈,其变化趋势是随着温度升高而呈指数或乘幂式上升,但温度敏感性系数Q10随温度的升高而减小。东北地区黑土样品试验表明,相同温度下不同土地利用的土壤呼吸强度以林地最高,农田中水田高于旱田,草地介于水田和旱田之间。第四,青藏与漠河地区冻土对温度上升反馈敏感,土壤呼吸强度随温度上升呈指数或乘幂式上升,而且在低温下的温度敏感性系数更高。采用分两库和三库的模型方法模拟土壤碳库动态变化,活性碳含量分别为0.117~0.342 g/kg和0.158~0.795 g/kg,占有机碳总量的比例分别为0.17%~2.89%和0.52%~8.75%。第五,通过密度分选、酸水解和氯仿熏蒸方法,对土壤有机碳进行物理、化学和微生物意义上的划分。同样的土样,酸水解测得的易氧化碳占土壤比重最高,其次是密度分选测得的轻组有机碳,氯仿熏蒸测得的微生物量碳最低。更多还原

【Abstract】 The low temperature condition in cold zones makes the soil accumulate organic carbon easily, and thus the density of soil organic carbon is relatively high; on the other hand, the warming extent in the regions with low temperature is obviously greater than that in warm regions. So, the change of soil carbon pool and the sensitivity of soil respiration were studied in several typical regions with low temperature in China. Using the National Multi-purpose Regional Geochemical Survey data, soil carbon reserves were estimated; the temporal and spatial variation of soil carbon pool were investigated combining with the historical data, and natural and artificial reasons for the change were analyzed. Soil respiration experiment were done in the laboratory, and the characteristics of soil respiration and its the temperature sensitivity in low-temperature regions were explored, so as to better understand the respond of soil organic carbon pool in low-temperature regions to the temperature change under global warming. In addition, different components of soil organic carbon were divided by three experimental methods. The main results are as follows:First, surface soil in the north area of the Songnen Plain was the carbon source from the whole aspect, with an average carbon-release ratio of 1479 t/km2, and the potential amount of soil carbon emission was 0.20 Gt in 20 years, which was equivalent to that of fossil fuel combustion 0.21 Gt; resulting from climate warming, land use and soil erosion, the values of soil organic carbon emission were 0.11 Gt, 0.09 Gt and 0.19 Mt, respectively. Under the existing mode of farming and land use, the potential of carbon sequestration in the Songnen Plain is negative.Second, the central and western area of Jilin was also the carbon source, and with a annual change rate of 0.199 tC ha-1·a-1, organic carbon was released from the soil into the atmosphere. Among the affecting factors, LUCC brought soil carbon sequestration; the change of carbon pool in the central and western area of Jilin was not obviously affected by temperature change, but it had a significant correlation with precipitation variation, which can largely explain that the SOC density is Northwest low, southeast high in spatial distribution, and gradually increases from northwest to southeast in trend.Third, soil respiration of different land use types showed significant positive feedback to temperature increase, which increases exponentially or in power-type as the temperature increase, while temperature sensitivity coefficient Q10 decreases with increasing temperature. The experiment of black soil in the Northeast area showed that at the same temperature, of different land use types, soil respiration in forest was highest, that in paddy field was higher than that in dry farmland, and that in grassland was between that in paddy field and that in dry farmland.Fourth, the feedback of permafrost samples in the Qinghai-Tibet Plateau and in the region of Mohe was sensitive to temperature increase; soil respiration increased exponentially or in power-type with the temperature, and temperature sensitivity coefficient was higher at low temperature. Using the model fitting methods of two pools and three pools, dynamic variation of soil carbon pool were fitted, and the result was that the contents of active carbon were 0.117~0.342 g/kg and 0.158~0.795 g/kg, respectively, and the proportion of active carbon to total amount of carbon pool were 0.17%~2.89% and 0.52%~8.75%, respectively.Fifth, by density separation, acid hydrolysis and chloroform fumigation, soil organic carbon was divided in the physical, chemical and microbiological sense, respectively. As to the same soil samples, the proportion of easily oxidized carbon measured by acid hydrolysis to soil dry weight was the highest, followed by that of light fraction carbon from density separation, and that of microbial biomass C measured by chloroform fumigation was the lowest.更多还原