长江下游典型江心洲形态演变过程恢复与土壤时间序列构建

Three typical fluvial islands (Guanzhou, Tietongzhou, and Zhangjiazhou) in the Anqing-Tongling section of the lower reach of the Yangtze River are selected for this study. Through interpretation of remote sensing images and comparison of historical maps, the evolution process of selected fluvial islands will be identified. Optically stimulated luminescence dating method will be applied to determine the ages of old flood protection dikes widely distributed within the selected fluvial islands. Thus the incremental processes of the islands over longer time scales will be recovered. After the differentiation of the homogeneity of the parent material, the soil chronosequences developed on the Yangtze alluvium will be established to reveal the rate and direction of soil evolution. Soil parameters such as pH, organic matter, calcium carbonate, ferric oxide and soil aggregates which undergo rapid changes at the early stage of soil development will be analyzed to reveal their dynamics. The fitting curves of the relationship between soil parameters and time can be further used as an easy-to-get indicators for discriminating the ages and evolution processes of fluvial islands in the middle and lower reaches of the Yangtze River. The results of this proposed research have great potential of being applied to geomorphology, soil sciences and environmental sciences.

以长江下游安庆-铜陵段的官洲、铁铜洲和张家洲等3个江心洲为研究对象，通过遥感影像解译和历史地图判读，恢复典型江心洲近百年来的形态演变过程。利用光释光测年法获得江心洲内部广泛分布的老防洪堤的修筑时间，恢复江心洲更长时间尺度的淤长过程。对不同年代洲身的土壤母质进行均一性判别后，构建长江冲积物母质的土壤时间序列，揭示土壤演化速率与方向。重点选择土壤pH、有机质、碳酸钙、氧化铁和土壤团聚体组成等在成土初期变化显著的指标，揭示其动态变化特征，建立其随时间变化的模型。借助这些模型，不仅能揭示土壤发生过程和演化趋势，同时也能把易于获得的土壤理化性质，用于长江中下游地区河流冲积物母质土壤的发育程度和江心洲洲身的年龄判别。本申请项目的研究成果具有应用于地貌学、土壤学和环境科学等相关领域的良好前景。

本项目通过在长江下游沿江冲积平原区根据围垦时间先后建立土壤时间序列，揭示土壤演化速率、方向及人类活动的影响。通过调查和考证，在安徽省无为市的长江北岸建立了一个跨度约1500 a的由长江冲积物母质发育的土壤时间序列，选择土壤pH、有机碳、无机碳、重金属、稀土元素、常量元素含量和土壤土壤微生物组成等指标，揭示其在成土过程中动态变化特征和影响机制。目前在以下方面取得一系列成果：长江安徽段江心洲土壤地球化学特征及其指示意义；长江下游沿江平原典型区土壤碳库分配及其动态；长江下游沿江平原典型区土壤C:N:P生态计量比动态变化及其对土地利用变化的响应；长江下游冲积平原围垦后土壤细菌演替特征及土地利用效应；长江下游冲积平原区土壤稀土元素富集与分馏特征。本项目的成果在土壤资源保护和土壤制图等领域有应用前景。