Seasonal variations of dissolved silicon in a karst bamboo forest soil-plant system

The distribution and transformation of silicon (Si) and phytolith in soil–plant systems in karst mountainous regions and their role in the terrestrial biochemical carbon-Si coupling cycle are poorly understood. Understanding seasonal variations of Si in a soil–plant system is helpful to reveal the interaction between available Si and phytolith dynamics, and their controlling mechanisms. Soil (O, A, AB-horizons) and different organs (culm, branch, old / new leaves) of bamboo (Dendrocalamus ronganensis) grown on a karst mountain were collected over the course of several seasons. The citric acid extractable Si (citric-Si) and phytolith contents of all samples from the soil–plant system were analyzed to assess their seasonal variations and their links to plant growth and environmental conditions. There was negative correlation between soil phytolith abundance and soil citric-Si content. And the soil citric-Si content rose with months and precipitation increased, were increased but independent on soil parent rock weathering, underground water and organic matter, likely due to rainfall affecting phytolith dissolution. In bamboo organs, citric-Si and phytolith content were increased from culm to branch, and to leaves. However, the citric-Si concentration of the culm remained relatively constant values and showed no apparent correlation with soil citric-Si. Silicon concentration in new leaves was correlated with monthly temperature and precipitation. Our experimental results illustrated that new leaves are suitable for studying the relationships between Si accumulation and climatic variables, whilethe culm is an ideal organ to record the interactions between plant and soil citric-Si concentrations during plant growth. The availability of Si for plant demand is governed more by the plant uptake rate of citric-Si, rather than its concentration. These findings contribute to a better understanding of soil plant available Si management and ecological remediation of karst mountains.