Improvement And Application Of The Automatic Measurement System Of Soil Respiration Channel

This research is mainly according to the dynamic soil respiration chamber method.IN laboratory，we have some improvements in software and hardware which are basedon original multi-channel soil respiration system; we also arranged indoor performancetesting，field consistency ratio and long-term field text experiment. The purpose of thisstudy is to get a better consistency with the foreign mainstream multi-channel soilrespiratory system and a better application in scientific research.System hardware improvements mainly covered air passage switching module，gas analysis module，gas acquisition module，micro-meteorological elements module.After amelioration，the system selected the better air passage switching module，thedomestic RR9501Model CO2infrared gas analyzer and RR1016data collector whichhave higher accuracy; the air temperature，humidity and pressure sensors were alsoinstalled in the gas chamber. In this way can we have a better automatic switch inchannels and gas path and a better automatic data collection and storage.Two main improvements in system software were the data collector and the controlprogram. Considering some factors like gas filtering system，gas path delay andanalyzer response delay etc. we rewritten programs in collector，storage and the switchof the channel and gas path.We reintegrated the soil respiration algorithm in data processing software，used VBlanguage to program，offset the shortages of the original soil respiration algorithm andproposed the slope method and time accumulation method. When use of slope methodwe can fit the data with linear and nonlinear equations and integrate water vapor in thegas chamber into the algorithm，all of above leading to a higher quality of data.Through the indoor test， the field consistency comparison and verificationexperiment of the original data we got the system zero and full scale are higher about15ppm; the analyzer Stability of volatility is controlled in2ppm，we test the Drift andnonlinearity of the analyzer zero and full scale by two outage; the air tightness andsensitivity of system are well. The field consistency comparison experiments of eachchannel in Shangzhuang is well and the system compared with Li-Cor8100the linearfitting coefficient is1.23and1.15，R2=0.6，it is better than Han guang Lu system whichR2=0.41. In Heihe experiments，the error is7%，R2=0.981between two arithmetic withLi-Cor8100’s original data，the error is10%，the correlation coefficient is0.977(P<0.01)， R2=0.954， by homemade arithmetic. When indoor CO2reaches a certainamount we can found that the flux values by nonlinear fitting method were significantly higher than that of by linear fitting method， the error is about18%.Overall，the automatic multi-channel soil respiration measurement system is easyoperation，simple maintenance and can accomplish automatic collection，observationand experiment，it suitable for long-term field observations. The system hardware andsoftware were improved significantly， application results show that it has goodconsistency with the foreign mainstream instrument，the fitting effect of two algorithmsand two fitting methods is well. At the same time，homemade data processing softwarehas high application with homemade system; the calculation and the correction are bothreliable and convenient.