南方离子型稀土矿区芒萁的蔓延格局与稀土迁聚响应

Ionic rare earth in Southern China is the unique resource of middle and heavy rare earth in China and main source of heavy rare earth in world, while severe ecological problems such as water and soil loss in the mingning area has become one of the key emphases and difficulties in ecological restoration.The common ecological restoration can not reduce rare earth content effectively, control soil and water loss permanently and be popularized and applied in large area. Applicants found that Dicranopteris dichotoma played a vital role in ecological restoration in ionic rare earth in Southern China, but Dicranopteris dichotoma' function has always been ignored. The project will take Changting County as the research area to calculate catastrophe situation of Dicranopteris dichotoma patches using catastrophe discriminant model, compute fitness of Dicranopteris dichotoma spread using catastrophe series model; simulate dynamic spread of Dicranopteris dichotoma patches coupling cellular automata model and catastrophe theory; estimate Dicranopteris dichotoma's extraction ability of rare earth, analyze Dicranopteris dichotoma's biological cycle of rare earth, reveal response of rare earth migration; validate and correct the models assembling the time gradient of stop mining points; predict and evaluate ecological restoration effect of Dicranopteris dichotoma with regard to soil and water conservation, rare earth extraction and economic benefit, and construct unique analysis framework and methodology system of phytoremediation in ionic rare earth in Southern China. The research findings can deepen the understanding of spread pattern of Dicranopteris dichotoma and response of rare earth migration in ionic rare earth mining area, providing new theoretical basis and technical support for ecological restoration in ionic rare earth mining area in southern China.

南方离子型稀土矿区水土流失等生态问题严重，成为生态修复的重点与难点。目前稀土矿区常用的修复模式无法有效降低稀土含量、长效遏制水土流失和大面积推广应用。申请人发现芒萁在南方离子型稀土矿区生态修复中具有重要作用，但相关研究极为薄弱。本项目以长汀县离子型稀土矿区为研究对象，采用突变模型计算芒萁斑块突变状态及芒萁蔓延适宜程度；耦合CA模型与突变理论模拟芒萁斑块时空格局；测算芒萁富集稀土能力，解析芒萁稀土生物循环，构建芒萁稀土迁聚动态定量模型，分析芒萁稀土迁聚的响应；通过实证分析验证模型精度及可行性；从水土保持、富集稀土和所需费用等角度预测与评估稀土矿区芒萁生态修复效果。研究成果可提升对芒萁生态修复机制的认识水平，为南方离子型稀土矿区生态修复提供新的科学依据与技术支撑。

南方离子型稀土矿区水土流失等生态问题严重，成为生态修复的重点与难点。本项目以长汀县离子型稀土矿区芒萁为研究对象，研究南方离子型稀土矿区芒萁的蔓延格局与稀土迁聚响应。结果表明：（1）随着稀土矿治理年限增加，芒萁平均株高、地上生物量和总生物量显著增加。（2）稀土矿区土壤TC、TN、TP含量等随着治理年限增加明显改善，但平均含量仍远低于全国土壤平均水平，尤其TP极为低下。（3）矿区4个样地的平均△值均小于0，位于突变模型中不稳定区域，根据矿区的实地样方调查和验证，各样地芒萁种群均处于蔓延扩散状态，对应于模型中的下叶到上叶突变过程。采用CA模型，刈割后2年，牛屎塘3个样方芒萁盖度分别可达89.78%、94.92%和90.48%，刈割后3年，3个样方芒萁盖度分别可达96.26%、99.47%和97.05%。（4）芒萁对稀土元素具有富集能力，其体内稀土含量是土壤中稀土含量的5~7倍。芒萁体内稀土元素的分布规律为叶片>地下茎根>叶柄。芒萁叶柄和叶对轻稀土元素的转移和富集能力要高于重稀土元素，芒萁地下茎根对重稀土元素的富集能力高于轻稀土。（5）芒萁最佳刈割时间是冬季，刈割频率为2年一次。偏中度污染的牛屎塘地区，通过刈割芒萁，需要78年左右，其土壤稀土含量才能降低到全国土壤稀土含量的平均水平，在轻度污染的下坑和三洲桐坝，大约需要28~48年。（6）低芒萁覆盖崩岗存在强烈稀土迁移，在水流和重力的作用下稀土自崩岗较高部位向较低部位迁移；芒萁可以成功定居于崩岗并影响土壤变量，有机质和pH在崩岗稀土迁移中起到重要作用；芒萁是控制稀土迁移和崩岗侵蚀的有潜力的植物。研究成果可提升对芒萁生态修复机制的认识水平，为南方离子型稀土矿区生态修复提供新的科学依据与技术支撑。