东北地区黑土退化地球化学指示与退化强度

利用东北地区土地质量地球化学调查数据，分析探讨了黑土不同退化类型的地球化学指标变化，并与20世纪80年代对比分析了黑土下降的面积和强度.结果显示，有机质下降和盐碱化是黑土退化的关键因素，在有机质缺乏区和碱性土壤区，土壤C/N值均小于10.0，且全氮、全磷、全硫、有机碳等指标间呈现弱相关性，而代表黏粒的铝、铁氧化物或指标与易被这些物质吸附的微量元素仍保持“生命共同体”特点.对比海伦及公主岭地区不同时期土壤锌、钼等微量元素含量，显示锌、钼等微量元素含量10年来均明显下降，表明在黑土有机质流失以及土壤盐碱化过程中土壤全氮、全磷、全硫以及锰、锌等营养元素在一定程度上随之流失.自20世纪80年代以来，松辽平原区土壤有机碳减少面积达54.45%，有机碳减少了131 Mt，其中向大气释放碳数量为26.2 Mt.在开垦相对较晚的黑龙江省，黑土有机碳下降程度最强，由北向南随着开垦程度增强，有机碳下降程度反而相对较小，体现随着开垦程度增强，有机碳不断趋于平稳的过程.通过统计及对比研究认为，在研究黑土退化及黑土开发保护过程中既要重视人为活动导致的土壤养分流失，也要重视黑土向强酸、强碱化发展的趋势.

BLACK SOIL DEGRADATION AND INTENSITY IN NORTHEAST CHINA: Geochemical Indication

Based on the data of land quality geochemical survey in Northeast China, the paper analyzes the geochemical index variation in terms of degradation type of black soil, and also the decreased area of black soil nutrients and degradation intensity compared with that in the 1980s. The results indicate that the decrease of organic matter and salinization contribute to most of black soil degradation. The soil C/N values are less than 10.0 in both organic matter-deficient area and alkaline soil area. Besides, the indexes of total nitrogen(TN), total phosphorus (TP), total sulfur (TS) and soil organic carbon (SOC) show weak correlation; while the aluminum and iron oxides or indexes representing clay content and trace elements, which are easily adsorbed by these substances above, still keep the characteristics of "living community". By comparing the trace element contents in Hailun and Gongzhuling areas in different periods, the results show the contents of trace elements such as soil zinc and molybdenum have decreased significantly over the past 10 years, indicating that the TN, TP, TS and soil nutrients of manganese and zinc are lost to a certain extent during the process of organic matter loss and soil salinization. Since the 1980s, the reduction area of SOC in Songliao Plain has reached 54.45%, reduced by 131 Mt, among which 26.2 Mt is released into the atmosphere. In Heilongjiang Province where the reclamation is relatively late, the SOC decreases the most, while the SOC decreases relatively less with the reclamation degree increasing from north to south, reflecting the SOC tends to be stable constantly with the increase of reclamation degree. Through statistics and comparative study, it is concluded that the study of black soil degradation and development/protection should pay attention to not only the loss of soil nutrients caused by human activities, but also the trend of black soil becoming strongly acidic or strongly alkaline.