Design Of A Device For Measuring Water Content In Tree Trunks Based On Internal Resistance Of Equivalent Power Source

Water content is an important physiological parameter of standing trees,which is of great significance in improving the regional ecological environment,evaluating the physiological health of trees,and agricultural business management.At present,the main means of real-time measuring the water content of standing trees is based on dielectric constant of the tree trunk.However,this method needs electromagnetic injections into the trunk,which might disturb biopotential measurements and cannot meet the needs of plant electrophysiology research.It is found that arrange electrodes at different positions of the trunk of trees can constitute a biological power source.There is a functional relationship between water content of standing trees and the internal resistance of the biological power source.This principle can be used to measure the water content in-situ in real time without external excitation signals.On the basis of existing methods and established relationship models of some tree species,this article developed a device for measuring water content in tree trunks based on internal resistance of equivalent power source,and conducted application testing,the main research content and conclusions are as follows:(1)Diurnal variation patterns of water content of two tree species were obtaioned.The diurnal changes in water content were observed on Ligustrum lucidum and Heian locust,respectively.The water content continued to decrease from 12:00 a.m.After 16:00 a.m.,the water content showd an upward trend,and reach the peak between 22:00 p.m.and 2:00 a.m.the next day.Subsequently,the water content kept decreasing until 6:00 a.m.,and then contunued continued to rise.Therefore,sampling from 22:00 p.m.to 2:00 a.m.the next day can obtain a large range of the change in water content of samples,providing a basis for obtaining the relationship model between the water content of standing trees and the internal resistance of equivalent power source.(2)The relationship model between the water content and internal resistance was established.Through continuous observations on the water content and internal resistance of two tree species,Ligustrum lucidum and Pagoda pseudoacacia,logarithmic curves were fitted using SPSS software to establish a relationship model: y=a× ln x +b,where a and b represent individual differences in standing trees.(3)A device for measuring water content in tree trunks based on internal resistance of equivalent power source was develped.The device included four modules: control and operation module,data acquisition module,data transmission module,and power module.The device could automatically monitor the power parameters and environmental parameters,and calculate the water content by using the relationship model between water content and internal resistance.(4)The measurement device was tested.The device was used to measure the water content on outdoor experimental tree species day and night.The drying method was used to measure the water content of experimental samples,in order to evaluate the reliability of the device.The results indicated that the device can effectively measure the water content in tree trunks,and has certain reference value in the research on in-situ real-time measurement of water content in tree trunks.