中国东部表土磁化率与现代气候因子的关系及其环境意义

Relationships between surface soil magnetic susceptibility and modern climatic factors in eastern China and their environmental significance

选取中国东部E-W和N-S两条环境断面的表土,对其进行磁化率测定并分析土壤磁化率的空间变化特征及其与年均温、年均相对湿度和年均降水量(MAT、MARH和MAP)等现代气候因子的关系。结果表明,E-W断面上土壤χlf(低频磁化率)和χfd(频率磁化率)空间分布具有东高西低的特征;N-S断面上χlf随纬度变化复杂,χfd有向北逐渐降低的趋势。在0℃≤MAT≤12℃或MAP≤1000mm时,χlf随MAT和MAP的增加而上升;当MAT>12℃或MAP>1000mm时,χlf表现出相反的变化。χlf与MAP的回归方程表明磁化率可以作为古降水的定量重建指标。研究结果显示磁化率在用于古环境重建时具有一定的适用范围,在200≤MAP≤1000mm的地区较好反映古降水的变化。

For proper understanding of the relationships between magnetic susceptibility and environmental factors and the influence of climate,especially the temperature and precipitation,on magnetic susceptibility,surface soil samples were collected from two environmental transections,E-W and N-S,in eastern China,and the magnetic susceptibility of soil samples was measured.Spatial distribution characteristics of soil magnetic susceptibility and its relationships with modern climate parameters such as MAT,MARH,and MAP were analyzed.Results indicate that theχlf andχfd values are high in the east and low in the west in E-W transection and thatχlf varies complicatedly with latitude andχfd declines toward the north in N-S transection.At 0℃≤MAT≤12℃or MAP≤1 000 mm,χlf rises with the increases of MAT and MAP.At MAT>12℃or MAP>1 000 mm,χlf shows the opposite change.Precipitation plays a primary role in the process of weathering and pedogenesis,and the influence of temperature is secondary.The regression equations betweenχlf and MAP indicate that magnetic susceptibility can be used as a quantitative reconstruction proxy of paleoprecipitation.The research results show that the reconstruction of the paleoenvironment using magnetic susceptibility has certain limitation,and magnetic susceptibility reflects the change in paleoprecipitation well in the area with 200≤MAP≤1 000 mm.