Growth decline mechanism of Zanthoxylum planispinum var. dintanensis in the canyon area of Guizhou Karst Plateau

Zanthoxylum planispinum var. dintanensis is an ecological and economic tree species widely planted in the canyon area of the Guizhou Karst Plateau. However, the rapid growth decline of its plantation in large scale has become one of the major environmental problems affecting vegetation restoration and the consolidation of the achievements of rocky desertification control. In this study, we collected soil samples in the full bloom period (March) and the vigorous growth period (June) from the declining and normal-growing Z. planispinum var. dintanensis communities. Through analyzing fertility quality indexes such as water content and nutrient levels, the mechanism of water-fertilizer coupling affecting the growth decline of Z. planispinum var. dintanensis plantation was explored. The results showed that the pH of soil was about 7.0, and there was no significant difference between the two types of communities. The surface soil water content of the declining community was <20%, which was significantly lower than that of the normal-growing Z. planispinum var. dintanensis community. The deficiency of quick-acting nutrients (e.g., available Ca, Mg, and B) and the imbalance of the medium and trace elements could cause the growth decline of Z. planispinum var. dintanensis, indicating that we should pay attention to the addition of quick-acting nutrients and their stoichiometry in the management process of Z. planispinum var. dintanensis. The comprehensive analysis showed that the decrease of soil water content induced the water-fertilizer coupling deficit effect, which might be one of the reasons for the growth decline of the Z. planispinum var. dintanensis community, in view of the fact that there are many factors causing the growth decline of artificial forest and the mechanism is complex. In the future, it is necessary to systematically study the growth decline of Z. planispinum var. dintanensis community from the perspectives of environmental media, root exudates, plant endogenous hormones, soil microorganisms, and water-fertilizer coupling based on the variations in time and space.

Automated summary

The study found that there was no significant difference in soil pH between the Zanthoxylum planispinum var. dintanensis communities in full bloom period and vigorous growth period, but the declining community had significantly lower surface soil water content than the normal-growing community. The lack of quick-acting nutrients and imbalance of medium and trace elements could lead to the growth decline of Z. planispinum var. dintanensis.