我国土壤资源的现状及特点 (3).pdf

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1、土壤学Soil Science2.4.5 Soil Formation FactorsTime and human activity2.4.5 2.4.5 土壤形成因素土壤形成因素-时间及时间及人为因素人为因素1.Soil age2.4.5 Soil forming factorstime and human activityTimeSoil age refers to the time of soildevelopment and is usually dividedinto absolute age and relative age.Figure1The longer the time i

2、s,the deeper thesoil may develop.1.Soil ageTimeThe time to date since the soilbegan to develop on the local freshregolith or new parent material,which is usually expressed in years.Absolute age Fig.2 Time required for soils to reach stablestate(quasi-equilibrium).From Chang-yongHuang,Soil Science,20

3、002.4.5 Soil forming factorstime and human activitySteady stateSoil profile developmentTime(year)1.Soil ageTimeRelative age refers to the stage of soildevelopment or the degree of soildevelopment.The age usually refers tothe degree of soil development.I treflects the modern soil formingprocess.Soil

4、age usually refers to the degree ofsoil development,also known as theso-called relative age.Relative ageFigure 3 Stages of soil developmentFrom Chang-yong Huang,SoilScience,20002.4.5 Soil forming factorstime and human activityAluminium oxideTimeLaterite stageSenior stagePrime stageJunior stageC hori

5、zon(fresh volcanic ash)Mineral soil surfaceLitter and organic surfaceVegetationIron oxideA horizonLaterite stage2.Stages of soil formationTimeFive stages of soil formation in the tropic region:Early stageJunior stagePrime stageFinal stageSenior stage2.4.5 Soil forming factorstime and human activityS

6、ummary of natural soil forming factorsFigure 4 Soil formation factors and their interrelationsProvide minerals;determine physical andchemical properties,such as texture,pores,nutrients and acidityAdding organic matter,promotingstructure formation,enhancing water andnutrient retentionInput water and

7、heat,control parentmaterial weathering and plant growth,a ffec tma te ria lmi gra ti ona ndtransformationInfluence parent material,organisms andclimate,control the distribution ofmaterial and energy in different terrainAffect the intensity of parent material,organisms,climate and terrain,causeintern

8、al stratificationParent materialOrganismTerrainClimateTimePhysicochemical factorProvide material and energyDistribute matter and energyControl the process of influenceSpatial factorsTemporalfactor2.4.5 Soil forming factorstime and human activitySoil influencing factorsHuman activity has a unique rol

9、e in the process of soil formation.It is essentially different from the other five natural soil forming factors.Human Factors（Human activities）1Human activities are conscious with purpose and direction;2Human production is social;3The influence of human activities can affecte and changenatural facto

10、rs;The effect of manpower on soil has dual effects(Table 1).2.4.5 Soil forming factorstime and human activityTable 1 Effect of human activities on soil forming factors(From E.M.Bridges,1982)Human Factors（Human activities）Favorable effectHarmful effects1.Parent materiala.Increase mineral fertilizer;b

11、.Increase shell and skeleton;c.Increase ash locally;d.Transfer excessive substances such assalt;e.Apply mud ash;f.Apply sedimenta.Animal and plant nutrients are taken awayinstead of being recovered by harvest;b.Toxic substances that are harmful to animalsand plants are applied;c.Soil composition isc

12、hanged in the way of inhibiting plant growth2.Terraina.Increasesurfaceroughness,buildinglandandcreatingstructures to control erosion;b.Accumulate materials to improveland height;c.Leveling landa.Wetland trenching and mining promoteland subsidence;b.Accelerate erosion;c.Mining3.Climatea.Increase wate

13、r content from irrigation;b.Artificial rainfall;c.Industrial production releases CO2into the atmosphere and maymake the climate warmer;d.Heat the air near the ground;e.Heatthe subsurface soil with electricity or hot air pipe;f.Change thecolor of the surface soil and change the reflectance;g.Drainwat

14、er;H.Wind redirectiona.The soil is damaged by overexposure tosunlight,expansion of freezing,windwardand compaction;b.The appearance of thesoil is changed during the formation of theland;c.Making smoke;d.Removing andburning the organic cover4.Organisma.To introduce and control the number of animals a

15、nd plants;b.To use organisms to directly or indirectly increase the organicmatter in the soil,including human feces and urine;c.To loosenthe soil by ploughing to obtain more oxygen;d.Recreation;e.Tocontrol fumigation to eliminate pathogenic organismsa.Remove animals and plants;b.Reductionoforganicma

16、ttercontentbyburning,ploughing,overgrazing,harvesting,accelerated oxidation,leaching;c.Increase orreproduce pathogenic organisms;d.Increaseof radioactive substances5.Timea.The soil is renewed by adding new parent material or exposinglocal parent material due to soil erosion;b.Land reclamation bydrainagea.Accelerate the migration of nutrients fromthe soil and vegetation,resulting in soildegradation;B.soils locate under the solidfiller or underwater2.4.5 Soil forming factorstime and human activityTHANK YOU谢谢