?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rft.title=Kohlenstofffl%C3%83%C2%BCsse+und+mikrobielle+Diversit%C3%83%C2%A4t&rft.subject=+Nutrient+turnover&rft.subject=+Soil&rft.description=Organic+farming+is+one+of+the+most+promising+alternatives+to+intensive+agriculture.+Crop+plant-soil+interactions+are+complex+and+influenced+by+agricultural+practice.+Many+efforts+have+been+done+to+elucidate+the+effects+of+different+farming+systems+on+crop+growth%2C+nutrient+availability%2C+soil+quality+and+biodiversity.+Many+studies+however+are+short-termed+and+rely+on+laboratory+rather+than+comparative+field+experiments.+The+DOK+field+trial+at+Therwil+(Basel-Land%2C+Switzerland)+is+one+of+the+few+long-term+field+trials+that+compare+organic+and+integrated+farming+systems+since+1978+(M%C3%83%C2%A4der+et+al.+2002%2C+http%3A%2F%2Fwww.fibl.org%2F).+Soils+of+this+field+trial+have+been+extensively+studied+with+respect+to+soil+nutrient+delivery%2C+soil+biology+and+microbial+biodiversity.+Organically+managed+soils+efficiently+produced+crops+at+lower+level+of+input+and+exerted+positive+effects+on+soil+quality+and+biodiversity.+Soil+microorganisms+are+important+in+the+cycling+of+carbon+and+plant+nutrients%2C+and+are+taken+as+bioindicators+of+soil+quality.+Results+of+the+DOK+trial+indicate+a+more+efficient+resource+utilisation+in+organic+treated+soils%2C+possibly+due+to+increased+soil+microbial+activity.+We+postulate+that+a+highly+diverse+and+active+microbial+community+may+accelerate+decomposition+of+plant+organic+matter+and+increase+turnover+of+carbon+uptake+in+organic+managed+soils+of+the+DOK+trial.%0D%0AIn+the+proposed+study+we+intend+to+measure+carbon+fluxes+from+the+crop+plant+to+the+soil+microbial+pool+under+field+conditions.+We+would+like+to+determine%2C+which+members+of+the+microbial+community+are+most+actively+involved+in+decomposition+and+plant+derived+carbon+uptake+in+different+farming+systems.+The+discrimination+of+plant+derived+carbon+from+native+soil+organic+carbon+is+now+possible%2C+since+maize%2C+a+C4-crop%2C+is+grown+for+the+first+time+in+the+long-term+DOK+field+trial+that+previously+has+been+dominated+by+a+C3-vegetation.+We+will+use+stable+isotope+techniques+to+identify+C4-crop+induced+changes+in+soil+carbon+pools+and+fluxes+by+calculating+the+difference+in+the+13C%2F12C-isotopic+ratio+of+the+crop+plant+and+the+soil.+Microorganisms+that+are+actively+involved+in+decomposition+and+uptake+of+plant+derived+carbon+will+be+traced+by+13C.+We+will+also+use+phospholipid+fatty+acid+(PLFA)+profiling+to+specify+microbial+groups+and+changes+in+the+microbial+community.+PLFA+are+specific+components+of+cell+membranes+only+found+in+intact+cells+and+are+indicative+of+major+microbial+groups.+Additionally%2C+the+12C%2F13C+signature+of+individual+PLFAs+will+determine+microorganisms+involved+in+active+uptake+of+maize+derived+13C.%0D%0ASince+13C+phospholipid+fatty+acids+have+hardly+been+investigated+by+the+use+of+a+natural+abundance+13C+approach%2C+the+application+of+this+technique+can+be+regarded+as+pioneer+work+in+the+field+of+microbial+ecology.+Assumably%2C+active+microbial+populations+can+be+distinguished+from+those+that+are+not+utilizing+the+plant-derived+carbon+sources.+The+outcome+of+this+project+will+provide+new+insights+in+functional+properties+of+the+microbial+community+in+soils+of+sustainable+farming+systems%0D%0AWe+would+like+to+determine%2C+which+members+of+the+microbial+community+are+most+actively+involved+in+decomposition+and+plant+derived+carbon+uptake+in+different+farming+systems.+We+will+use+phospholipid+fatty+acid+(PLFA)+profiling+in+combination+with+stable+carbon+isotope+techniques.+PLFA+profiling+will+allow+the+characterization+of+microbial+phylogenetic+groups+whereas+12C%2F13C+signature+of+individual+PLFAs+will+assign+specific+microorganisms+involved+in+active+uptake+of+plant+derived+carbon.+The+difference+in+the+13C%2F12C-isotopic+ratio+of+the+crop+plant+and+the+soil%2C+allows+for+identifying+C4-crop+induced+changes+in+soil+carbon+pools+and+fluxes.+Carbon+derived+from+the+maize+can+be+distinguished+from+Carbon+derived+from+soil+organic+matter+mineralization.+Root+exudates+are+partly+incorporated+into+soil+microorganisms+and+partly+mineralized+to+CO2.+The+flux+rate+and+pool+size+changes+will+allow+for+an+estimate+of+root+biomass+and+turnover+and+indicate+carbon+utilisation+efficiency+of+soil+microbes.+%0D%0AThe+contribution+of+root+exudates+and+plant+residues+to+soil+organic+matter+fractions+that+are+actively+involved+in+soil+processes+will+be+measured%2C+and+thus%2C+it+is+expected+to+substantiate+previous+findings+under+controlled+lab+conditions+of+higher+decomposition+rates+and+an+enhanced+incorporation+of+available+organic+carbon+to+microbial+biomass.+The+acquired+data+will+be+integrated+to+soil+carbon+modelling+approaches+with+respect+to+low+input+and+organic+farming+systems.%0D%0A&rft.type=Project+description&rft.type=NonPeerReviewed&rft.identifier=%7BProject%7D+Kohlenstofffl%C3%83%C2%BCsse+und+mikrobielle+Diversit%C3%83%C2%A4t.+[Soil+carbon+fluxes+and+microbial+diversity.]+Runs+1995+-+2006.+Project+Leader(s)%3A+Fliessbach%2C+Andreas%2C+Research+Institute+of+Organic+Agriculture+(FiBL)%2C+CH-5070+Frick.+More+information+online+at+%3Chttp%3A%2F%2Fwww.fibl.org%2Fde%2Fschweiz%2Fforschung%2Fbodenwissenschaften+%3Chttp%3A%2F%2Fwww.fibl.org%2Fde%2Fschweiz%2Fforschung%2Fbodenwissenschaften%3E%3E.&rft.relation=http%3A%2F%2Forgprints.org%2F6047%2F