Effects of Clipping Intensity on the Physiology of Dicranopteris pedata and Its Interroot Soil in the Rare-Earth-Mining Area in Southern China

Abstract

Clipping is crucial during phytoremediation. However, research into the effects of clipping intensity on the physiology of Dicranopteris pedata (D. pedata) and its interroot soil in the rare-earth-mining area in southern China is lacking. A clipping experiment was conducted to verify the phytoremediation effect of D. pedata. The physiology of D. pedata, such as biomass, antioxidant enzymes, chlorophyll, and rare-earth elements (REEs), were determined after clipping. And the microbial community diversity and soil enzyme activities in the interroot soil of D. pedata were investigated. The phytoremediation efficiency was determined at the end of the experiment. The results showed that the compensatory growth effect of D. pedata was stronger with increasing clipping intensity. There was no significant difference in the α diversity of interroot soil microorganisms of D. pedata at different clipping intensities, but β diversity analysis showed that the clipping treatment group deviated from the control group. Only urease activity decreased among the interroot soil enzymes in D. pedata after clipping, while the soil catalase and sucrase were less responsive to clipping. The REEs accumulated by D. pedata were dominated by light REEs in the aboveground part of the plant, while the amounts of light and heavy rare-earth elements accumulated in the underground part of the plant were similar. The phytoextraction of REEs gradually increased with increasing clipping intensity. It was concluded that 100% clipping once a year is the most appropriate when considering D. pedata’s phytoremediation potential and soil system. The time it takes for 100% clipping of D. pedata to reduce the soil TREEs (total rare-earth elements), LREEs (light rare-earth elements), and HREEs (heavy rare-earth elements) to below-average soil REE concentration in China was estimated to be 25.54 years, 19.56 years, and 65.43 years, respectively, which was significantly lower than that for other clipping intensities and the control group. It is concluded that clipping D. pedata is an effective way to promote phytoextraction efficiency in the southern rare-earth-mining areas. The soil can still support the resumption of D. pedata growth after high-intensity clipping.