Growth Characteristics And Adaptation Mechanism Of Dicranopteris Dichotoma In Ionic Rare Earth Mine Area Of South China

Ionic type rare earth deposit is a kind of valuable middle-heavy rare earth resource that is only found in southern China.However,the back-ward production techniques and the out-of-order and extensive ways to explore resource have led to severe damage of the ecological environment of the rare earth mining which has been the typically degraded ecosystem zone in the southern red soil region in southern China.Vegetation restoration is the first and foremost work in the process of ecological restoration of mine areas.Dicranopteris dichotoma is one of the last herbage disappeared from degraded ecosystem,and it is also the pioneer vegetation of restoration and reconstruction.In this paper,we took four rare earth mines in Changting County,Fujian Province and its plant of Dicranopteris dichotoma as the research objects.We analyzed the Dicranopteris dichotoma growth process and its environment characteristics and discussed Dicranopteris dichotoma 's development tendency based on catastrophe theory.Furthermore,we tried to explore the adaptive strategies of Dicranopteris dichotoma to respond to rare earth mining environments from the features such as biomass allocation,nutrient demand and the accumulation rare earth elements.The main results are as follows:?1?The average plant height,overground and total biomass of Dicranopteris dichotoma significantly are increased as restoration time went on,but plant density is opposed;Seasonal dynamics of growth trend is consistent in all sample sites of rare earth mine area.?2?the rare earth mine's soil bulk density ranges from 1.44 to 1.65 g/cm³,the value of pH ranges from 4.19 to 4.66 and the soil moisture content ranges from 6.27%to 11.33%;the content of TC,TN and TP has been improved significantly as restoration time went on,but its average is still far lower than the national average,especially the content of TP.The soil rare earth elements was mainly composed of light rare earth enrichment type.The average content of rare earth elements ranges from 310.42 to 1509.17 mg/kg,which is significantly higher than that of China's mainland.?3?the dynamics trend of Dicranopteris dichotoma population was analyzed by applying the catastrophe model.The results showed that average delta value was less than 0 corresponding to unsteady zone of the catastrophe model.According to analysis and research in the field trip,all kinds of Dicranopteris dichotoma populations are spreading and dispersing corresponding to catastrophe process in the model from upper lobe to lower lobe.?4?In the aspect of biomass allocation,as the restoration time went on,the root-shoot ratio of Dicranopteris dichotoma was increased from 1.36 to 0.38,which showed its strong phenotypic plasticity and environmental adaptability.In terms of nutrient demand,Dicranopteris dichotoma had efficient element utilization efficiency by low content nutrient,what's more,the contents of nutrient among overground is significantly higher than underground.The content of N in overground gradually was reduced as restoration time went on,but the content of C and P in underground gradually were increased.In the part of accumulation of rare earth elements,in the overground of Dicranopteris dichotoma,the homeostasis indexes(H_LREE?H_HREE?H_REE)are all more than 1,but in the underground,the homeostasis indexes are all less than 1.Comparatively,Dicranopteris dichotoma in the overground has stronger homeostasis ability to accumulate rare earth elements than the underground.When the content of rare earth element of the environment is very high,the overground part of the plant will generate "soil-plant barriers",which will result in the selective absorption and controlled accumulation.