Research On Measurment And Monitor Of Stem Water Content

This study took the behavior of stem-water-system dielectrics as a key point for further development and evaluation of a new kind of Standing Wave Ratio (SWR) stem moisture measuring system. A series of academic analysis and a lot of experiment research on SWR-based stem moisture technique were carried out and presented in this paper. On the basis of the research, a new stem moisture technique, which it is very suitable for field use, was developed. At the same time, the transportation principle of stem moisture was produced the relationship between stem water content, sap flow rate and water potential. Finally, a system was created to monitor stem water content and to further advise variable irrigation. In general, the study can be summarized as follows:1. According to the plant physiology, the model between stem water content and sap flow rate, water potential was created, and the simulate calculation was get for the daily stem water content.2. Through theoretical analysis on the behavior of stem-water-system dielectrics, it is proved that the real parts of the dielectric constant under high frequency or microwave can be used to measure stem water content rapidly. This method can get a lot of measurement results with high accuracy and wide applicability. As a further application of the above result, a stem moisture technique based on Standing Wave Ratio was developed.3. In this study, a key point of the study is to build up a mathematical model of the character impedance the SWR technique. The structure of two equal-length probes can be viewed as parallel transmission line, the character impedance model of probe with equaling length was built up by utilizing mathematical theory of approach. And then, the character impedance model of SWR probe was built up and validated by experiments.4. Amounts of laboratory and field experiments showed that the consistency of SWR technique is good in different stem texture. There were not big variations among their measurement results. Under the support projects, a series of experiments had been done to compare SWR technique with wood moisture sensor GMK-1010 which was made by Korea. The results showed that the performance of the SWR technique is as good as other technique.5. At the same time, the values between stem water content, sap flow rate and water potential were measured to verify the model of stem moisture. For monitoring stem moisture timely, a measurement system was created to monitor stem water content and to further advise forestry irrigation.In general, SWR technique is good to measure stem water content. It gives more value to save water and get the situation of the tree.