     Giorgios de Milatos, Demis Baldocchialopoulos and Lorenzos Missonis Department of Environmental Science, Policy, and Management, Socratic University of California

Microbial Soil Respiration and its dependency on Carbon Inputs, soil Temperature and Moisture Curiel Yuste J, Baldocchi DD, Misson L, Wong S, Gershenson A, Goldstein HA Department of Environmental Science, Policy, and Management, University of California, Berkeley

BACKGROUND  SOM decomposition is sensitive to climate change  Lack of mechanistic understanding of soil processes

QUESTIONS  Plant activity control SOM decomposition ….but how?  Are microbes completely subject to plant role or in turn….are they be able to acclimate to changes independently? How fast?  Is all this above of interest on the global picture?

METHODOLOGY  Field soil respiration measurements during 2005  Temperature sensitivity of SOM from different soils differing in plant C inputs

Field measurements  Li-COR 6464  Collars height 4.4 cm and diameter 11 cm  Periodical measurements during 2005  Soil temperature and water

 Soil intact cores  4 soils with different plant C inputs at collection time: oak savannah open (to) and understorey (tu), ponderosa pine control (bc) and trenched (bt)  Close dynamic system (dCO 2 /dt)  Similar to Fang et al. (2005 ) methodology –Field capacity –4 hours/5 o C cycle (mimic daily changes) –From 20 to 35 o C –Measuring soil CO 2 efflux, calculate sensitivity to temperature Lab incubations

Results

Role of plant activity on soil C dynamics

Calculation of labile and recalcitrant pools of SOM C cum (t) = C f * [1-( e –k f *t)] + (C total -C f ) * [1- (e –k s * t)]

Results

Calculation of pools and turnover times

Do microbes acclimate to changes? Is this important in terms of soil C emissions?

dCO2/dT = dqCO2/dT + d MB/dT K N dCO2/dT = dqCO2/dT

Maintenance respiration (F a ) =V max *[S]/K m + [S] (Q 10 = 3) Microbial growth () higher for r- than for K- strategy organisms. Assuming similar temperature sensitivities

 Plant presence associated to fast labile C in soil (exudates, symbiosis, both?)  Acclimation of microbial population to changing environment may play an important role on C dynamics  Do we have the right molecular tools to monitor microbial population dynamics? CONCLUSIONS

IDEAS FOR SHYNTESIS PAPERS (SOIL RESPIRATION WORKSHOP)  Detection and quantification of photosynthetic signal in soil respiration. J. Curiel Yuste  u* correction of nighttime NEE using nighttime continuous measurements of soil respiration. Bernard Longdoz  Vertical distribution of soil CO2 production in relation to soil CO2 efflux. Jukka Pumpanen

Data required from participants  NEE & continuous measurements (half-hourly, hourly) of soil respiration (chamber or soil profile probes at different depths)  Additional data from site –Ecological data –Meteorological data –Soil physical data

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