土壤养分循环

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1、土壤养分循环第一节：土壤碳素及循环与生物效应土壤碳对植物营养的直接作用不大，植物从大气中吸收CO2，但土壤有机碳的转化为大气补充CO2，是大气碳的源和库，调节大气中CO2浓度，特别是温室效应直接与土壤碳的转化有关。因此，土壤碳对植物营养、土壤肥力及环境都很重要。土壤中碳的形态、含量及转化1.土壤碳存在的形态:有机碳和无机碳。后者主要为碳酸盐，对环境影响不大。有机碳又分为水溶态和难溶态。水溶态有机碳包括：低分子量有机酸、AA、糖酸、羟圬酸高铁载体。难溶态有机碳包括胡敏酸、胡敏素、木质素、植物落叶等。土壤中含碳化合物的来源：最初源于光合作用2.土壤中碳的含量自然界碳库主要有三：（1pg=10

2、15g）海洋中碳：39000pg大气中碳：750pg陆地中碳：2200pg一般砂质土0-100cm含碳3.1kg/m2，而有机土含碳77.6kg/m2，土壤碳以有机碳表示，占总碳的58%左右有机质含量分级：一级:>40g/kg二级:30-40g/kg三级:20-30g/kg四级:10-20g/kg五级:6-10g/kg六级:<6g/kgEcologicalroleofSOMAggregationslowserosionSoilconditionerWaterholdingcapacityPermeabilityBulkdensity/penetrationresistanceSoilor

3、ganismfoodandfunctionNutrientreserveLeachingprotectionCarbonsinkLargestterrestrialpoolEffectsofSOMdepletiononenvironmentDecreasedyieldsIncreasederosion50%-90%savingsforNTvs.CTIncreasedleachingIncreasedfertilizeruseSoilcarbonequilibriumAffectedbymanyfactorsamountandtypeofbiomassinputsoilmicrobialc

4、ommunitymoistureregimeoxygensupplytemperaturesoiltexturesupplyofothernutrientsSOMdeclines20-40%afterconversiontocroplandWherewillbioenergybe?Hypothesis:bioenergyplantationsincreaseCAffectedbymanyfactorsamountandtypeofbiomassinputsoilmicrobialcommunitymoistureregimeoxygensupplytemperaturesoiltextu

5、resupplyofothernutrientsBiomasshasdegradationresistantlitterprovidesgoodsoilmicrobialhabitathashighwaterholdingcapacityprotectsfromoxidationcoolssoilbyshading/waterpromotesaggregationtightnutrientbudget3.土壤碳的循环转化TheCarbonCycle1.autotrophsfixcarbondioxidefromtheatmosphereduringphotosynthesis2.carb

6、ondioxideisreleasedbackintotheatmospherebyrespiration3.thecarboncycleisveryfast4.Othercarboncyclesareslowa.carbonisdivertedintowoodorotherdurableorganicmaterialb.canalsobelockedupincoalandoildeposits5.Theoceansmayactasabufferthatdonotallowthecarbondioxideamountintheatmospheretovarywidely6.carbond

7、ioxideisdissolvedinwaterandischemicallyconvertedtootherforms.Alltoldoceancontains50timestheamountofcarbonasisavailableintheatmosphere土壤碳循环土壤碳循环海洋中C空气CO2绿色植物光合作用石油煤沥青呼吸、燃烧、工业利用土壤有机质动物微生物矿化4.碳循环的调节自然恢复将一年生作物转为牧草或速生林种植深根作