Effects of prescribed burning on plant growth and soil properties of a cycas panzhihuacycasis forest

The effects of prescribed burning on the growth, leaf physiology of Cycas panzhihuaensis L. Zhou et S. Y. Yang and the physical and chemical properties of surface soil (0-15 cm depth) were studied. When compared with the control plots, there were more new leaves and new trees (increased by 201.66% and 317.7%, respectively) in the burnt plots; in contrast, neither height nor the number of adult C. panzhihuacycaside plants were affected significantly by the burning. However, no significant effects of the prescribed burning was observed on the photosynthetic pigment content including chlorophyll a, chlorophyll b, and chlorophyll a+b, and there were also no significant change in the contents of soluble sugar, soluble protein, carbon (C), nitrogen (N), phosphorous (P), potassium (K), the activities of nitrate reductase (NR), glutamine synthetase (GS), and the C/N ratio, N/P ratio of new leaves. On the other hand, the concentration of carotenoid in the new leaves of C. panzhihuacycaside was significantly reduced by the burning. In addition, the prescribed burning obviously changed the physical and chemical properties of the surface soil (0-15 cm). After burning the soil water content, pH, and content of total N, P, K were significantly reduced. However, content of soil organic carbon (TOC), nitrate (NO3 --N), ammonium(NH4 +-N) were significantly increased, while the microbial biomass C content and microbial biomass N content increased slightly. Therefore, the prescribed burning was helpful to increase nutrient (N especially) availability of the soil in the C. panzhihuacycaside forest and provided favorable conditions for the plant regeneration.