A low-cost monitoring system of stem water content: Development and application to Brazilian forest species

The storage of water in the plant and its impacts on eco-hydrological processes are not commonly considered in the models for estimating plant transpiration and evapotranspiration. The high costs required for a wide monitoring network are major obstacles to obtain more consistent results. The aim of the present study is to build and evaluate a low-cost system for the continuous monitoring of stem moisture content (SM). After constructing and calibrating the stem moisture sensors, they were used to monitor plants of the parica (Schizolobium amazonicum) and catingueira (Caesalpinia pyramidalis Tul.). The parica was studied in equatorial climate conditions while the study with the catingueira was carried out in a tropical semiarid condition. Three individuals of the parica and four of the catingueira were selected for monitoring the SM. The stem moisture sensor probe that was developed showed a small error (less than 4.8% in 95% of measurements) compared to the gravimetric method, and can be used to monitor SM in other species as well as those under study, as long as prior calibration is carried out. In a field experiment, the probe enabled the SM response to be studied in two species with fairly different wood densities and moisture content, in environments of contrasting soil and climate characteristics.