The Sap Flow Measurement Based On The Heat Ratio Method (HRM) And Environment Factor Correction Research

The water is all plant’s survival and the fundamental, over the past decade, our country land desertification is serious, soil erosion to speed up. It is important to reasonable allocation of water resources; water saving drought tolerant plant is a choice in our country in the future development environment of top priority. It is an important guiding significance that study and analysis of main sand-fixation shrub drought desert water features and law of water, in order to select the drought tolerant water-saving plants. The determination of reasonable forestation density and configuration and stable fixing the ecological protection function play shrub has important guiding significance.The sap flow measurement is an important means to study water law of the plants. For growth in arid and semi-arid areas the plant stem flow is low, traditional methods of measurement in the plant of the low rate sap flow measurements take a lot of time, so the heat loss is large. The measurement error is difficult to overcome. Proposed to address these issues in this article, a new hot technology-heat ratio method (HRM) to measure the low rate of sap flow stems of the plant. The temperature probes are spaced equally at both ends of the heating element. With the heating element to release heat pulse, temperature probe at time t to record temperature and (t-1) time temperature.It’s take less time than wait until the two probes at the same temperature, especially low rate of plant sap flow measurements.The heat ratio method (HRM) greatly reduce the measurement error caused by the heat pulse conduction in heat loss.On the other hand,the heat ratio method (HRM) to improve the sampling frequency, long-time continuous measurement, especially for low rate sap flow of plants measurements.Environmental factors on stem flow measurement are an influence. This paper, from the three aspects of the environmental factor influence of flow measurement stem:(1) probe position deviation, study the measurement in the wrong position when the probe on the measurement results the impact, and propose a modified method.(2) The environment temperature, the temperature on the influence of heat transfer heat pulse.(3) The wound correction, stem flow measurement of plants will cause mechanical called flints, plants wound response function for to stem the influence of flow measurement, and this paper puts forward the wound on the correction coefficient compensation fixed.In the environmental factors on the influence of flow measurement stems, to meet the requirements of precision, the paper applied the hierarchical genetic algorithm based on the BP neural network to sap flow measurement environmental factors of data processing. For the input of the heat pulse rate, the environment temperature and wound correction factor, output for the heat pulse rate after correction. Based on hierarchical genetic algorithm of BP neural network can improve the traditional BP neural network. The traditional BP neural network training speed is slow, the local minimum points escape and algorithm of slow convergence speed. Compared with other traditional method of data processing, trained based on hierarchical genetic algorithm of BP neural network can effectively to more input data treatment, the large amount of data, accuracy, and can effectively solve based on the heat ratio method (HRM) stem flow measurement in the environmental impact factor correction on the question of the data processing, fixed amount detection and reduce the errors caused measurement. In Mat lab simulation environment data before and after processing the contrast of the environment factor to observe the effect of flow measurement stems.