【摘要】：樹干邊材液流速率是研究整株樹木蒸騰規(guī)律的重要指標。目前主要的測量方法中,熱擴散法和熱脈沖法由于需要獲取零莖流速率參照值,根據(jù)經(jīng)驗公式來推算莖流速率,存在引入誤差和在不同樹種間通用性差等缺陷;另外現(xiàn)有市場上的莖流測量產(chǎn)品存在價格昂貴、穩(wěn)定性不好等問題。針對上述問題,本文研究了一種改進熱脈沖法的測量技術(shù),基于熱示蹤原理,設(shè)計了一種“溫度峰-峰值”莖流測量方法,克服了標準參數(shù)獲取、通用性差等問題,并開發(fā)了一套完整的植物莖流采集系統(tǒng)設(shè)備,采用便攜式結(jié)構(gòu),傳感器安裝簡便。本文研究內(nèi)容包括以下幾個方面:(1)根據(jù)“溫度峰-峰值”測量方法的需求,設(shè)計了一種插針式莖流傳感器,通過優(yōu)化結(jié)構(gòu)設(shè)計,實現(xiàn)了傳感器熱量注入的高精度、可重現(xiàn)性控制以及邊材液流溫度變化的高靈敏度感知;設(shè)計了相應(yīng)的傳感器信號處理電路和數(shù)據(jù)采集模塊,并基于MCGS組態(tài)軟件設(shè)計上位機系統(tǒng)。(2)通過分析樹干邊材液流的特征,結(jié)合實際試驗總結(jié)邊材液流傳導熱量引起溫升曲線的變化特點,設(shè)計了高頻率采樣、門限檢測、軟件濾波、多次校驗的峰值捕捉方法,在北京市農(nóng)林科學院內(nèi)以楊樹、梧桐樹、棗樹、側(cè)柏四個樹種為樣本進行的測試結(jié)果表明觀察“峰-峰值”現(xiàn)象的最佳間距為30mm到35mm。(3)研究植物傷口機理、環(huán)境因子對測量精度的影響,根據(jù)Swanson等提出的數(shù)值計算模型模擬熱對流及傳導現(xiàn)象得出的傷口修正模型,對誤差進行修正。通過搭建模擬測量系統(tǒng)和實體測量對系統(tǒng)進行測試:模擬測量結(jié)果與實際流速之間的差值低于0.01 mm/s;以楊樹為樣本進行的多組實體測量結(jié)果顯示,測量數(shù)據(jù)重復(fù)性好,日莖流變化趨勢一致,表明本文設(shè)計的莖流傳感器及其數(shù)據(jù)采集系統(tǒng)穩(wěn)定可靠。
[Abstract]:The sap flow rate of sapwood is an important index to study the transpiration of the whole tree. At present, the main measuring methods are thermal diffusion method and thermal pulse method, because of the need to obtain the reference value of zero stem flow rate, according to the empirical formula to calculate the stem flow rate, there are some defects such as introducing error and poor generality among different tree species. In addition, the existing market stem flow measurement products are expensive, poor stability and other problems. In order to solve the above problems, an improved thermal pulse method is studied in this paper. Based on the principle of thermal tracer, a "temperature peak-peak" stem flow measurement method is designed, which overcomes the problems of obtaining standard parameters and generality. A complete plant stem flow acquisition system is developed, which adopts portable structure and is easy to install. The research contents of this paper include the following aspects: (1) according to the requirement of "temperature peak-peak" measurement method, a stylus type stem flow sensor is designed. By optimizing the structure design, the high precision of heat injection is realized. Reproducibility control and high sensitivity perception of temperature change of sapwood liquid flow; The corresponding sensor signal processing circuit and data acquisition module are designed, and the upper computer system is designed based on MCGS configuration software. (2) the characteristics of sap flow of sapwood are analyzed. The characteristics of temperature rise curve caused by heat conduction from liquid flow of sapwood were summarized, and the peak capture method of high frequency sampling, threshold detection, software filtering and multiple check was designed. Poplars and sycamore trees were used in Beijing Academy of Agriculture and Forestry Sciences. The test results of four species of jujube and Platycladus orientalis showed that the best distance between peak and peak was between 30mm and 35mm. (3) the mechanism of plant wound and the effect of environmental factors on measurement accuracy were studied. According to the numerical model proposed by Swanson et al to simulate the heat convection and conduction phenomena, the wound correction model is obtained, and the error is corrected. The system is tested by building a simulated measurement system and a solid measurement system: the difference between the simulated measurement results and the actual velocity is less than 0. 01 mm/s; The results of multi-group solid measurement with poplar as the sample show that the measured data have good repeatability and the trend of daily stem flow change is the same, which indicates that the stem flow sensor and its data acquisition system designed in this paper are stable and reliable.
【學位授予單位】：湖南工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：S126;TP274

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