Biotic And Abiotic interactions

Soil Microbiology

1. SOIL MICROBIOLOGY -
BIOTIC AND ABIOTIC INTERACTIONS
Dr. S. Anu Kiruthika
Bengaluru North University
Bengaluru.
1

2. INTRODUCTION
•SoilsareoneoftheEarth'sessentialnaturalresources,yettheyare
oftentakenforgranted.
•Mostpeopledonotrealizethatsoilsarealiving,breathingworld
supportingnearlyallterrestriallife.
•Soilsandthefunctionstheyplaywithinanecosystemvarygreatlyfrom
onelocationtoanotherasaresultofmanyfactors,includingdifferences
in.
Climate,theanimalandplantlifelivingonthem,soil'sparentmaterial,
thepositionofthesoilonthelandscape,andtheageofsoil.
2

3. Composition of Soil
Soilsarecomposedoffourmaincomponents:
1.Mineralparticlesofdifferentsizes.
2.Organicmaterialsfromtheremainsofdead
plantsandanimals.
3.Waterthatfillsopenporespaces.
4.Airthatfillsopenporespaces.
3

4. Uses of Soil
•Theuseandfunctionofasoildependsontheamountof
eachcomponent.
•Forexample,agoodsoilforgrowingagriculturalplantshas
about45%minerals,5%organicmatter,25%air,and25%
water.
•Plantsthatliveinwetlandsrequiremorewaterandlessair.
•Soilsusedasrawmaterialforbricksneedtobecompletely
freeoforganicmatter.
4

5. The Five Soil Forming Factors
Thepropertiesofasoilaretheresultoftheinteraction
betweenthefivesoilformingfactors.
Thesefactorsare:
1.ParentMaterial
2.Climate
3.Organisms
4.Topography
5.Time
5

6. 1.ParentMaterial
•Thematerialfromwhichsoilisformeddetermines
manyofitsproperties.
•Theparentmaterialofasoilmaybebedrock,organic
material,constructionmaterial,orloosesoilmaterial
depositedbywind,water,glaciers,volcanoes,or
moveddownaslopebygravity.
6

7. 2.Climate
•Heat,rain,ice,snow,wind,sunshine,andother
environmentalforcesbreakdownparentmaterial,
•moveloosesoilmaterial,
•determinetheanimalsandplantsabletosurviveata
location,
•andaffecttheratesofsoilformingprocessesandthe
resultingsoilproperties.
7

8. 3.Organisms
•Soilishometolargenumbersofplants,animals,and
microorganisms.
•Thephysicalandchemicalpropertiesofasoildetermine
thetypeandnumberoforganismsthatcansurvivein
thatsoil.
•Organismsalsoshapethesoiltheylivein.
8

9. •Forexample,thegrowthofrootsandthemovement
ofanimalsandmicroorganismsshiftmaterialsand
chemicalsaroundinsoilprofile.
•Thedeadremainsofsoilorganismsbecomeorganic
matterthatenrichesthesoilwithcarbonand
nutrients.
9

10. •Animalsandmicroorganismslivinginthesoilcontroltherates
ofdecompositionfororganicandwastematerials.
•Organismsinsoilcontributetotheexchangeofgasessuchas
carbondioxide,oxygen,andnitrogenbetweensoilandthe
atmosphere.
•Theyalsohelpsoilfilterimpuritiesinwater.
•Humanactionstransformsoilaswell,aswefarm,build,dam,
dig,process,transport,anddisposeofwaste.
10

11. 4.Topography
•Thelocationofasoilonalandscapealsoaffectsits
formationanditsresultingproperties.
•Forexample,soilsatthebottomofahillwillgetmore
waterthansoilsonthehillside,andsoilsonslopesthat
getdirectsunlightwillbedrierthansoilsonslopesthat
donot.
11

12. 5.Time
•Theamountoftimethattheother4factorslistedabove
havebeeninteractingwitheachotheraffectsthe
propertiesofthesoil.
•Someproperties,suchastemperatureandmoisture
content,changequickly,oftenoverminutesandhours.
•Others,suchasMineralchanges,occurveryslowlyover
hundredsorthousandsofyears.
12

13. The soil profiles
•Thefivesoilformingfactorsdifferfromplacetoplacecausingsoilpropertiesto
varyfromonelocationtoanother.
•Eachareaofsoilonalandscapehasuniquecharacteristics.
•Averticalsectionatonelocationiscalledasoliprofile.
•Whenwelookcloselyatthepropertiesofasoilprofileandconsiderthefive
soilformingfactors.
•Soilhorizonscanbeasthinasafewmillimetersorthickerthanameter.
•Individualhorizonsareidentifiedbythepropertiestheycontainthatare
differentfromthehorizonsaboveandbelowthem.
13

14. 14

15. 15

16. •Someonhorizonsareformedasaresultoftheweatheringofmineralsand
decompositionoforganicmaterialsthatmovedownthesoilprofileovertime.
•Thismovement,calledilluviation(accumulation),influencesthehorizon's
compositionandproperties.
•Otherhorizonsmaybeformedbythedisturbanceofthesoilprofilefrom
erosion,deposition,orbiologicalactivity.
•Soilsmayalsohavebeenalteredbyhumanactivity.
•Forexample,builderscompactsoil,changeitscomposition,movesoilfromone
locationtoanother,orreplacehorizonsinadifferentorderfromtheiroriginal
formation.
16

17. Moistureinsoil
•Moistureplaysamajorroleinthechemical,biologicalandphysicalactivities
thattakeplaceinsoil.
•Chemically,moisturetransportssubstancesthroughtheprofile.
•Thisaffectssoilpropertiessuchascolour,texture,pH,andfertility.
•Biologically,moisturedeterminesthetypesofplantsthatgrowinsoilandaffects
thewaytherootsaredistributed.
•Forexample,indesertareaswheresoilsaredry,plantssuchascactimuststore
water,orsendrootsdeepintosoiltotapwaterburiedtensofmetersbelowthe
surface.
17

18. •Plantsintropicalregionshavemanyoftheirrootsnearthesurfacewhere
organicmaterialstoresmuchofthewaterandnutrientstheplantsneed.
•Agriculturalplantsgrowbestinsoilswerewateroccupiesapproximately
one-fourthofthesoilvolumeasvapourorliquid.
•Physically,soilmoistureispartofthehydrologiccycle.
•Waterfallsonthesoilsurfaceasprecipitation.
•Thiswaterseepsdownintosoilinaprocesscalledinfiltration.
18

19. •Afterwaterinfiltratessoil,itisstoredinthehorizons,takenupby
plants,movedupwardbyevaporation,ormoveddownwardinto
theunderlyingbedrocktobecomegroundwater.
•Theamountofmoisturecontainedinasoilcanchangerapidly,
sometimesincreasingwithinminutesorhours.
•Incontrast,itmighttakeweeksormonthsforsoilstodryout.
19

20. •Ifasoilhorizoniscompacted,hasverysmallporespaces,oris
saturatedwithwater,infiltrationwilloccurslowly,increasingthe
potentialforfloodinginanarea.
•Ifthewatercannotmovedownintosoilfastenough,itwillflow
overthesurfaceasrunoffandmayrapidlyendupinstreamsor
otherwaterbodies.
•Whensoilisnotcoveredbyvegetationandtheslopeofthelandis
steep,watererosionoccurs.
20

21. •Deepscarsareformedinthelandscapeasaresultofthe
combinedforceoftherunoffwaterandsoilparticles
flowingoverthesurface.
•Whenasoilhorizonisdry,orhaslargeporespacesthat
aresimilarinsizetothehorizonabove,waterwillinfiltrate
thehorizonquickly.
•Ifsoilgetstoodryandisnotcoveredbyvegetation,wind
erosionmayoccur.
21

22. SoilTemperature
•Thetemperatureofasoilcanchangequickly.
•Nearearthsurface,itchangesalmostasquicklyastheairtemperature
changes,butbecausesoilisdenserthanair,itstemperaturevariations
areless.
•Dailyandannualcyclesofsoiltemperaturecanbemeasured.
•Duringatypicalday,soiliscoolinthemorning,warmsduringthe
afternoon,andthencoolsdownagainatnight.
•Overthecourseoftheyear,soilwarmsuporcoolsdownwiththe
seasons.
22

23. •Becausesoiltemperaturechangesmoreslowlythanair
temperature,itactsasaninsulator,protectingsoilorganismsand
buriedpipesfromtheextremesofairtemperaturevariations.
•Intemperateregions,thesurfacesoilmayfreezeinwinterand
thawinthespring,whileinsomecolderclimates,apermanent
layerofice,calledpermafrost,isfoundbelowthesoilsurface.
•Ineithercase,thegroundneverfreezesbelowacertaindepth.
23

24. •Theoverlyingsoilactsasinsulationsothatthe
temperatureofthedeeperlayersofsoilisalmost
constantthroughouttheyear.
•Temperaturegreatlyaffectsthechemicaland
biologicalactivityinsoil.
•Generally,thewarmerthesoil,thegreaterthe
biologicalactivityofmicroorganismslivinginthesoil.
24

25. •Microorganismsinwarmtropicalsoilsbreakdownorganic
materialsmuchfasterthanmicroorganismsincoldclimatesoils.
•Nearthesurface,thetemperatureandmoistureofsoilaffectthe
atmosphereasheatandwatervapourareexchangedbetween
thelandandtheair.
•Theseeffectsaresmallerthanthoseatthesurfacesofoceans,
seas,andlargelakes,butcansignificantlyinfluencelocalweather
conditions.
25

26. •Hurricanes(cyclone)havebeenfoundtointensify
whentheypassoversoilthatissaturatedwithwater.
•Meteorologistshavefoundthattheirforecastscanbe
improvediftheyfactorsoiltemperatureandmoisture
intotheircalculations.
26

27. BIOTIC/ABIOTIC INTERACTIONS AND REGULATION OF SOIL MICROBIAL
COMMUNITY
27

28. THE END
28