上海市城郊土壤有机质的时空变异特征及其影响因素

Spatial-temporal Variation Characteristics of Soil Organic Matter and Its Impact Factors in Suburban Shanghai

为了深入了解城市化对城郊农业土壤有机质变化的影响,本研究运用GIS和地统计学结合的方法,对上海市土壤有机质的时空变异规律及其驱动因子进行了探讨。研究结果表明,土壤有机质在整个研究区内表现出中等程度变异,土壤有机质含量分布呈现出西南高,东部低的特点。1980—1999年土壤有机质含量增加,而1999—2010年土壤有机质含量下降。1999—2010年,由水田变为蔬菜地、苗圃时,土壤有机质含量分别下降6.72 g/kg和6.15 g/kg,而水田保持不变时,仅下降了1.51 g/kg。通过空间叠加分析可知,1999—2010年,上海市大部分地区土壤有机质含量呈减少趋势,只有北部、南部和西南的部分地区的土壤有机质含量有所增加。土壤有机质增加的区域离城市较远,而土壤有机质下降区域位于近郊,主要原因是近郊部分水田转化为蔬菜地和苗圃,土地利用方式改变导致了作物根茬和秸秆还田减少,同时有机质分解加快,因此引起了土壤有机质积累下降。

In order to understand the effect of city expansion on the soil organic matter （SOM） changes in suburban areas, GIS technology and geostatistics method were used to study the spatial and temporal variation of SOM in Shanghai and the driving factors were discussed. The results showed that SOM in the study area had a moderate variation. SOM content in the southwest areas was high but low in the eastern areas. SOM content increased from 1980 to 1999 but decreased from 1999 to 2010. From 1999 to 2010, when paddy fields converted to the vegetable fields or nursery fields, SOM content decreased 6.72 g/kg and 6.12 g/kg, respectively, but when the paddy fields kept unchanged, SOM content only decreased 1.51 g/kg. Spatial overlay analysis showed that SOM content reduced in most of the area, only increased in some areas in the north, south and southwest. The areas where SOM increased were far away from the city and the areas where SOM decreased were near the city. The main reason was when some paddy fields which near the city converted into vegetable fields or nursery fields, crop residues and straw returned decreased and the decomposition rate of SOM increased, which led to a decline of SOM content.