Dicranopteris dichotoma leaf stoichiometry in collapsing erosion areas in Southwest Fujian

Collapse mound is a form of widespread and severe soil erosion in granite areas in South China. As a typical pioneer plant in collapse mound areas, Dicranopreris dichotoma is critical for soil and water conservation in collapsing erosion areas in South China. Plant stoichiometric characteristics reflect the capacity of plants to absorb and store mineral nutrients from the soil. They also reflect the long-term stoichiometric distribution formed during plant adaptation to the environment. Therefore, analysis of the characteristics of ecological stoichiometry of D. dichotoma in collapsing erosion areas can provide an important guidance for ecological restoration in collapsing erosion areas. In order to clarify the characteristics of nutrient storage of D. dichotoma in extremely degraded collapse mound ecosystems, the characteristics of carbon (C), nitrogen (N), phosphorus (P) contents and C/N, C/P and N/P ratios for D. dichotoma leaf in three typical collapse mound areas with different erosion intensities in Southwest Fujian Province were analyzed. The ecological stoichiometry characteristics of D. dichotoma leaves in different erosion intensities of collapsing wall and collapse mound under the same erosion intensity in different erosion positions were also comparatively analyzed. The results showed that the average contents of C, N and P in the leaves of D. dichotoma in collapse mounds were 477.10 g·kg^-1, 6.45 g·kg^-1 and 0.25 g·kg^-1, respectively. The N and P contents were generally extremely low. The average ratios of C/N, C/P and N/P were 96.82, 2 097.20 and 27.67, respectively. Thus D. dichotoma growth was primary limited by P content. On the other hand, there were significant differences in C, N and P contents, and C/P and N/P ratios in collapsing wall leaves under different erosion intensities (P < 0.05). All the C content along with C/P and N/P ratios decreased with increasing erosion intensity. While N content was higher in collapsing walls with moderate erosion, P content increased with increasing erosion intensity. This showed that D. dichotoma had strong ability to adapt to collapse mound ecosystems with severe soil erosion. On the other hand, there were significant differences in P content, and C/P and N/P ratios in D. dichotom a leaves in different erosion positions of collapse mounds under the same erosion intensity (P < 0.05). P content was highest in the upper catchment and lowest on collapsing walls. All the C/P and N/P ratios on collapsing walls were significantly larger than in other erosion positions. Obviously, it was evident that the ability of D. dichotom a to assimilate carbon in collapsing walls was stronger than in other erosion positions of collapse mounds. In addition, P utilization efficiency in collapsing walls was significantly higher than that in other erosion positions. In conclusion, D. dichotom a had strong ability to assimilate C and use P efficiently in severely eroded gully ecosystems and was adaptive to environments with severe soil erosion and extreme nutrient deficiency by regulating C, N and P contents in its cells.