The structural role of flowing carbon

Everybodyknowsthepresenceofcarbonisimportantforsoilstructure,however,italsohasastructuralrole.Thiscomesbacktocarbonbeingthemainbuildingblockofpastures.

Bystructuralrole,Imeanthewaypaddocksaremorewaterefficientandhaveincreasedcapacitytocaptureresourceswhenplantsarephysicallypresent.

Thewickeffect

Carbonhasastructuralroleaspartofplanttheroots.Roots,whichare45%carbon,actas“wicks”totakewaterdownthroughthesoilprofile,especiallyimportantwithhardersoils.

Thisisachievedbywatertravellingdownbesideroots.Bettermanagedplants,withmoreextensiverootsystems,distributewaterfasterthroughthesoilandtogreaterdepth.

Root response to different grazing pressure

1–Grazed6timesat1-leafstage

2–Grazed3timesat2-leafstage

3–Grazedtwiceat3-leafstage

Restingpasturesforashortperiodafterrainincreasescarbonflowsforrootconstruction,whichinturnimprovestheinfiltrationoffuturerain.

Withperennialgrasses,therootsgrowanddieback.Thisresultsincavitieswhererootshavepreviouslybeen.Thesecavitiesareveryeffectiveforwaterinfiltration.

Rootshelpsecurenitrogen

Wherepasturesarenotfertilised,thenitrogenpresentinthesoiloriginatesfromtheearth’satmosphere,whereitmakesupabout78%oftheair.Eachhectareoftheearthiscoveredbyabout84,000tonnesofnitrogenintheatmosphere.

Nitrogencomesinwithrain,soinfiltrationdeterminesplantavailablenitrogenfromthissource.InthetallgrasssavannahsoftheNorthernTerritoryofAustralia,eachyearrainbringsin2kgofnitrogenperhectare.Toputthisintoperspectiveinthisarea,attheendofthegrowingseasonthereis10-15kgofnitrogeninstandinggrass,whichislowcomparedwithmorefertileareas.

Thereseemstobeatrendtowardsmoreintenserainfallevents,whichiswhyimprovingwaterinfiltrationisevenmoreimportant.

Liftingwind&shading

Haveyouevergivenanythoughttowhyclothesonthelinedryquickeronawindydaythanonastillone?Goingbacktobasics,moistureisreleasedfromthewetclothesintothedrierairaroundthem.Whentheimmediateairbesidetheclothesissaturated,nomoremoistureisreleasedfromtheclothes.Thewinddriestheclothesbecauseitblowsawaythemoistairandreplacesitwithdrierair,whichthenabsorbsmoremoisturefromtheclothes.

Theclotheslineprincipleiscentraltoanotherstructuralroleofcarbon.Standingplantsliftwindoffthesoilsurfacewhichslowsthedryingofsoil.

Shadingbyplantsisanimportantcomponentofwateruseefficiency,asitslowsevaporationandmakesmorewateravailabletoplants.

Maintainingthepopulationofsoilmicrobesovertime

Alotofsoilmicrobesarelikeperennialgrasses,inthattheyhavetogointodormancywhenconditionsarenotfavourable.

Whenthesoildriesquickerthanitshould,thisdoesnotgivesoilmicrobestimetogothroughtheirnormalprocessofgoingintodormancyandsotheydie.

Thesoilremainingdryforalongtimeduringdroughtsisnotanissuefordormantmicrobes.MicrobesfoundinthetombsofEgypthavebeenreactivated.

Collectingdew

Anotherstructuralroleofcarboniscollectingdewinsomeenvironments.Thisreliesonthesurfaceareaofgrassbeingadequate.

Germanscientist,DrWihelmRiplexplainswhyplantsareresponsibleforgreateravailabilityofwatertothelandscape,“Watervapourintheloweratmosphereclosetovegetation,evenwithoutasinglerainevent,canbeprecipitatedbyleaves,needlesandotherstructureswithhighsurfacetovolumeratios.Theresultisaloweringofsurfaceenergyandawarmingofthesestructures.”

Inthecaseoffrosts,formoisturetoaccumulateonthesoilsurface,therehastobeenoughmoisturefrozenthenthawedasthesunrises.Inanareasufferingthedriestwinterinyears,Iobservedthattherewasregularlymoistureonthegroundatthebaseofplantsafterthesunhadrisen.Thisphenomenonwasonlyoccurringwherethegrasswasthickandtall.Itwasactuallymaintainingsomegreenleafatthebasewhereitwasprotectedfromfrost.

Conclusion

Thestructuralroleofcarbonreliesonthefastermovingcarbonresidinginplants,whichinturnreflectsthemanagementofcarbonflowsfromwhatraindoesarrive.

Managementthatleadstobetterwaterinfiltrationviaincreasedrootsandthenslowerdryingofthesoilsurfaceduetowindbeinglifted,increasesgermination.

RootsplayaveryimportantroleinReefprotection.Waterhasvolumeandifitgetstogetherandgathersspeed,thenthatiswhenitdoesdamagebyerodingsoilandcarryingnutrientsintowaterways.Gettingmorerainfallintothesoilreducesthisproblem.Also,morestandingpasturehelpskeepwaterapartandfromgatheringspeed.

30November,2017

Next week’s discussion: “Financial analogy”.