Abstract:

Objectives: The objectives are to select appropriate methods to measure stem fluid flow to reveal its dynamic changes and influencing factors according to the unique biological characteristics and anatomical structure of bamboo plants. It is conducive to in-depth elucidating their physiological and ecological processes and mechanisms, and providing scientific basis for accurate management, efficient utilization and ecological management of water and nutrients in bamboo forests. Method: The methods for measuring stem sap flow in bamboo plants was originated from woody plants, including heat pulse method, heat dissipation probe method and stem heat balance method.Among them, the heat pulse method is not limited by environmental conditions such as terrain, but the measurement results are uncertain under the condition of low transpiration; the cost of the heat dissipation probe method is relatively low, but the sensor is prone to measurement errors caused by the radial gradient formed by the flow density, which needs to be verified and calibrated; the stem heat balance method does not require probe drilling, andthe instrument wraps the bamboo stem to obtain real-time data, but the basic assumptions of stable flow conditions and constant temperature need to be met. Usually, the three assay methods are combined and mutually validated to obtain more reliable flow measurement results. Result: The stem flow of bamboo plants has a relatively common patterns in daily variation, night dynamics and seasonal scales, showing a similar "peak" curve. The daytime flow of bamboo plants starts in the early morning, then increases continuously, reaches a peak in the afternoon, and then continues to decrease, reaching the lowest value after nightfall; the flow changes in sunny weather generally show a "single-peak" curve, and the rainy weather shows a "multi-peak" curve. The nocturnal flow generally maintains a low flow, significantly lower than the daytime flow under different seasons and environmental conditions, and the variation is small. On the seasonal scale, the liquid flow is the lowest in spring, the highest in late summer and early autumn, from winter to summer, the time when the flow begins to rise and the peak is gradually advanced, and the reverse is reversed from summer to winter. There are also differences in the flow pattern of bamboo plants at different growth stages.Factors influencing changes in the flow of bamboo plants include physiological anatomy different from those of woody plants and environmental factors. Among them, the hollow stem and underground whiplash root system of bamboo plants are the biological basis for influencing fluid flow. Environmental factors have a strong correlation between air temperature, saturated water vapor pressure difference and solar radiation and changes in stem flow by influencing transpiration and plant root pressure. Different measurement methods, such as the length of probe and the specific location of measurement, will also affect the measurement results. Conclusion: To put forward prospects for measuring the stem flow of bamboo plants in the future, it is theoretically necessary to explore the influencing mechanisms, and develop statistical and verification models; technically, the existing measuring methods should be integrated and improved, and suitable methods and technologies should be developed to improve the measurement accuracy; in the application of results, it is appropriate to set parameters based on differences in region, climate, terrain conditions and bamboo species to obtain a widely applicable model of measurements.

Key words: bamboo, stem sap flow, thermal technical method, characteristics, influence factors