ace-soil-respiration土壤呼吸测量技术(英文)课件

1、Soil RespirationStephen BonnageDirectorSoil RespirationStephen BonnagSoil Respiration and the Carbon cycleSoil: 4th largest pool2nd largest source to atmosphereSoil Respiration and the CarboSoil RespirationQ. What is soil?Soil is a complex mixture of mineral matter, organic matter and living organis

2、msSoil RespirationQ. What is soiSoil RespirationWhat are the organisms? RootsAlgaeBacteriaFungiEarth wormsInsectsSoil RespirationWhat are the oSoil RespirationQ. How many? A. 1 gram of soil typically holds more organisms than there are people on the Earth109 microbes in 1 gram of soil Soil Respirati

3、onQ. How many? ASoil RespirationQ. What is soil respiration? A. All living organisms, whether animal or microbe, produce CO2 gas as a by-product of the process of respiration.Soil RespirationQ. What is soiSoil RespirationAs Raich and Schlesinger (2002) point out,The rate at which CO2 moves from the

4、soil to the atmosphere is controlled by the rate of CO2 production in the soil (the true soil respiration rate), the strength of the CO2 concentration gradient between the soil and the atmosphere, and properties such as soil pore size, air temperature and wind speed that influence the movement of CO

5、2 through and out of the soil. These factors will be important to consider when assessing various attempts to quantify measurement methodologies. Soil RespirationAs Raich and SSoil RespirationRaich and Schlesinger (1992) estimated that global soil respiration consists of 50 Pg C/year from detritus a

6、nd 18 Pg C/year from live roots and mycorrhizae. Soil respiration rates have been reported to be higher in grasslands than in forests, and higher in deciduous forests than in coniferous forests Soil RespirationRaich and SchlSoil RespirationRaich and Tufekcioglu (2000) reported in a review paper that

7、 root contribution to total soil respiration is high in cold, northern climates such as arctic tundra (50-93%) and boreal forests (62-89%). Temperate forests are lower, with 33-50% in broad-leaved forests, 35-62% in pine forests, and 12-40% in grasslands and croplands. Due to the wide range of the r

8、eported values, they could not establish a correlation between vegetation type and root contribution to soil respiration. Soil properties such as temperature, moisture, and substrate properties were found to be the most influential factors determining soil respiration. Soil RespirationRaich and Tufe

9、Soil RespirationSoil respiration has been shown to be strongly influenced by temperature (Lloyd and Taylor 1994, Fang and Moncrieff 2001). Respirations increases exponentially with temperature. The temperature dependence of soil is often described by the Q10 value. Generally defined, this factor rep

10、resents the difference in respiration rates over a 10 deg C interval; however, there is some debate as to how Q10 is calculated based on what temperature range to use and which equation best describes respirations temperature dependence. Fang and Moncrieff (2001) suggest the equation:Q10 = (R2/R1)10

11、/(T2-T1)for first-order exponential functions, where R1 and R2 are measured respiration rates at temperatures T1 and T2, respectively. Soil RespirationSoil respiratiSoil RespirationLloyd and Taylor (1994) found that the relative sensitivity to temperature change is much greater for soils at low temp

12、eratures than for warmer soils. For example, in the absence of moisture limitations, an increase from 0 to 1 deg C would result in a 22% increase in respiration, while an increase from 25 to 26 deg C leads to a 5% increase. Thus, modest global change scenarios resulting in a 1 to 2 deg C increase in

13、 mean temperature would have the most significant effect on the 60 g C/m2 year respired by tundra. Soil RespirationLloyd and TaylSoil RespirationKirschbaum (1995) compared published respiration data and found that Q10 values decreased with increasing temperature. He concludes that temperature rise w

14、ill lead to increased contribution of atmospheric CO2 from soil. This trend may feedback upon itself as elevated CO2 promotes primary production, increasing inputs to soil organic matter, and further increasing respiration. Nevertheless, the contribution of soil to total atmospheric CO2 is not expec

15、ted to be as important as fossil fuel combustion or deforestation. Soil RespirationKirschbaum (19Soil RespirationQ. How can we measure it? A. Chamber techniques, eddy covariance, Soil RespirationQ. How can we Soil RespirationClosed SystemSoil RespirationClosed SystemSoil RespirationOpen SystemSoil R

16、espirationOpen SystemSoil RespirationAt temperatures over 35 degrees Celsius, root respiration begins to shut down completelyWhy?A. Enzymatic activity is interrupted Soil RespirationAt temperatureSoil RespirationMicroorganisms are divided into three temperature groups; cryophiles, mesophiles and the

17、rmophiles. Cryophiles function optimally at temperatures below 20 degrees Celsius, mesophiles function best at temperatures between 20 and 40 degrees Celsius and thermophiles function optimally at over 40 degrees Celcius. In natural soils many different cohorts, or groups of microorganisms exist. Th

18、ese cohorts will all function best at different conditions so respiration may occur over a very broad range Soil RespirationMicroorganismsSoil RespirationSoil moisture is another important factor influencing soil respiration. Soil respiration is low in dry conditions and increases to a maximum at in

19、termediate moisture levels until it begins to decrease when moisture content excludes oxygen. Soil RespirationSoil moisture Soil RespirationHowever,studies have shown that soil moisture only limits respiration at the lowest and highest conditions with a large plateau existing at intermediate soil mo

20、isture levels for most ecosystems. Hmmmmm!Soil RespirationHowever,HmmmmmSoil RespirationSoil RespirationSoil RespirationTemporal VariabilityHow flux rates change over timeDailyMonthlyYearlySoil RespirationTemporal VariaSoil RespirationDiurnal Over a 24 hour periodSoil RespirationDiurnal OverSoil Res

21、pirationSoil RespirationSoil RespirationSoil RespirationSoil RespirationUnder high soil moisture conditions, many bacteria take in too much water via diffusion, or the movement of a substance across the bacterias cell membrane. This may cause the cell membrane to lyse, or break, spilling the cell co

22、ntents into the soil. The lysis of bacteria allows for a spike in resources for many bacterial predators such as protozoans. This rapid increase in available labile substrates will cause short term enhanced soil respiration Soil RespirationUnder high soiSoil RespirationSpatial variabilityUnder natur

23、al conditions soil flux rates can vary hugely between sites 1 or 2 meters apartSoil RespirationSpatial variabSoil RespirationSpatial variability So how many chambers will I need?Soil RespirationSpatial variabSoil RespirationSpatial variability Go to the field with a soil survey type system and take

24、as many measurements as possibleSoil RespirationSpatial variabSoil RespirationSpatial variability The mean = 50The Standard deviation = 20The Coefficient of variation Cv = / = 20/50 = 0.4 Generally expressed as a percentage e.g. 40%Soil RespirationSpatial variabSoil RespirationSpatial variability No

25、r=(2XCv/error)2Where:N= number of samplesCv= Coefficient of variationError=sample mean deviationCV values for most soils between 10 50%For example, for a 30% = CvTo achieve a 10% error N= (2x30/10)2 = 3636 stations or more will give a 10% errorTo achieve a 20% error N= (2x30/20)2 = 9 stationsSoil Re

26、spirationSpatial variabSoil RespirationSoil RespirationACEAutomated Soil CO2 Exchange SystemACEAutomated Soil CO2 ExchangeSoil respiration: a significant growth area of environmental research Only limited field research until recently. Significant increase in soil respiration sales and interest in l

27、ast 2-3 years. (Soil chambers for LCi, LCpro+, ADC2250)Political interest=Funding=ResearchSoil respiration: a significanAutomated Soil CO2 Exchange SystemACELong-term unattended monitoring of soil flux- Days / weeks / monthsAutomated Soil CO2 Exchange SyRepeated monitoring of same area of soilThen a

28、utomatically exposes soil after measurement - Ambient conditions to soil area between measurements User sets experimental timesUnique “swinging arm” mechanism - Reliable and field ruggedAutomated design covers soil to take measurementRepeated monitoring of same arace-soil-respiration土壤呼吸测量技术(英文)课件In

29、tegral CO2 analyser inside soil chamber+ Fast response+ No gas hang ups in long length of tubing+ Easier to set up+ Field robustNo animals eating tubing+ No large pumps = power efficient+ Major advantage of ACE0-1000ppm CO21ppm resolutionIntegral CO2 analyser inside sComplete System or StationSoil c

30、hamberwith collarSwinging armControl consoleFully integratedFully independent measurement Stationno PC or PDA requiredComplete System or StationSoilRobust field StationNo long length of gas tubingGas hang upsAnimal damageReliable automated mechanismPower efficient40Ah car battery 28 days Weatherproo

31、f design Console cover waterproof connections Transportable (7Kg)Robust field StationNo long leAvailable as closed or open systemClosed systemChamber closesMeasurement one takenUpdates measurements every 10 seconds (CO2 rises)Until end of experiment (customer set)TimeCO2 concentrationNCER calculated

32、Available as closed or open syClosed system mode2.6L large chamber+ Measurements are quick and simple (5-10mins)+ Most popular - Can be less accurate - Station is closed system only Closed system mode2.6L large cOpen system modeOpen systemBefore chamber closed reference air is measured Chamber close

33、d, measurements every 10 secondsCO2 rises until equilibrium reachedUntil end of experiment (customer set)TimeCO2 concentrationNCER calculatedRefOpen system modeOpen systemRefOpen system mode1 L chamber + Potentially more accurate+ Station can be used in closed modeClosed chamber Measurements more co

34、mplex and slower (15-20mins)Open system mode1 L chamber + Zero / ambient optionChange in gas circuit allows ambient CO2concentration to be measuredMore accurate NCER In network not every Station needs ambient option Ambient can be manually enteredZero / ambient optionChange inTransparent chambersSoi

35、l onlySoil and small plantsSoil fluxNCERTransparent chambersSoil onlySOther ACE Station sensorsPAR LCi / LCpro+ Silicon photocell 0-3000umolesSoil Moisture Connect up to 4 as standard Common commercial sensors Delta-T and DecagonSoil Temperature Connect up to 6 as standard Thermistors (ADC supply) T

36、hermocouples Other ACE Station sensorsPARSoEasy to set up and programNo gas circuit set up between analyser and chamberControl consoleLarge display screen5 keys onlyMenu driven software (like LCi) Program Mode (open / closed) Period (time between measurements) Flow rate (in open system,100-500ml/min

37、) Chamber volume and diameter (known) Height (from soil in open system) End of experiment By time Delta CO2 Log fileEasy to set up and programNo gACE Station displays and records Gas exchange data ppm mmoles Soil flux calculations (NCER) Other sensor dataData storage Interchangeable Compact Flash ca

38、rds In console 1G card = 4,000,000 data setsMeasurement every 15 minutescard capacity 114 years! ACE Station displays and recorACE Station configurationOpen or Closed SystemMetal or transparent chamberOptional ambient readingTemperature sensorsSoil moisture sensorsUpgrade sensor numbersSpare connectors ACE Station configurationOpen Li8100Introduced 2004Separate chamber and analyser 2M of tubing awayNot captured marketWater ingressData errorsExpensive (US$20,0