青藏高原东部表层土壤色度的空间变化特征及其环境意义

认识青藏高原东部现代表土的色度特征及其空间分布，理解其与现代气候因子之间的联系，对于高原地区黄土-古环境重建和揭示第四纪环境变化历史具有重要意义。通过对研究区表层土壤色度的详细分析，对比现代气候资料，探讨了青藏高原东部表层土壤色度的空间变化特征及其环境意义。结果表明：① 高原东部表土色度参数空间变化特征差异显著，表现为随纬度升高，土壤亮度呈先减小后增大的趋势，而红度和黄度则逐步减小；随经度的升高，黄度先增大后减小，而红度值逐步减小；红度和黄度整体随着海拔上升而呈先减小后升高的特征。这些变化特征和差异是表土色度对高原东部复杂地理环境和水热条件变化响应的结果。② 在高原的干旱-半湿润区，土壤亮度对降水的响应敏感；红度和黄度对大尺度的温度变化响应较敏感，而较冷的环境下，红度对温度响应复杂，但与降水存在一定的联系。红度/黄度比值主要指示了气候控制下的赤铁矿和针铁矿的变化和竞争，对干旱-半湿润区域的降水变化响应较为敏感。青藏高原东部现代表土色度与气候密切相关，其空间变化特征一定程度上反映了该地区现代气候因子的空间变化；另一方面由于该区地形和气候复杂多变，部分色度指标与气候关系复杂，在重建青藏高原东部黄土古环境变化历史时需要谨慎。

Spatial variation of surface soil color in the eastern Tibetan Plateau and its environmental significance

The color characteristics and spatial variation of surface soil in the eastern Tibetan Plateau (ETP) are important for understanding the relationship between soil color and modern climate factors and for reconstructing the Quaternary paleoclimatic environment. We analyzed in detail the spatial variation of surface soil color and its environmental significance. Results show that the spatial variation of surface soil color in the ETP is obvious. The soil brightness decreases first and then increases with latitude increase, and the redness and yellowness decrease with the latitude increase. In addition, the change in yellowness shows a parabolic curve from increase to decrease with longitude increase, and redness decreases with longitude increase. Both redness and yellowness decrease first and then slightly increase with altitude increase. The redness/yellowness ratio does not change significantly with latitude, but decreases with longitude increase, and increases with altitude. The spatial variation of soil color is resulted from the hydrothermal variation in local complicated arid semi-humid environment. In the study region of plateau, brightness decreases with precipitation increase within a certain precipitation range and is sensitive to precipitation. Redness and yellowness are sensitive to large-scale temperature changes. However, the response of redness to temperature is complex in a cold environment, which is related to precipitation. The redness/yellowness ratio indicates mainly the formations of hematite and goethite under special climate conditions, and the ratio is more sensitive to precipitation in arid and semi-humid areas than to temperature. The spatial variation in the color of surface soil reflects the spatial variation of regional climate factors under modern atmospheric circulation to a certain extent. However, due to the complexity of terrain and climate in the ETP, the relationship between color parameters and climate is complex. One should be careful in rebuilding the paleoenvironmental history from loess in the ETP.