Ecology Lecture 3Ecology Lecture 3

Ralph KirbyRalph Kirby

What is soilWhat is soil

Before life invaded the land from the sea, there Before life invaded the land from the sea, there was probably little that looked like soil todaywas probably little that looked like soil today Dust like MarsDust like Mars Little organic matterLittle organic matter A few microorganisms perhapsA few microorganisms perhaps

However, soil is the basis of all terrestrial life and However, soil is the basis of all terrestrial life and without soil, there would be no plants, no soil without soil, there would be no plants, no soil microorganism and no land animalsmicroorganism and no land animalsPlants obtain many of their water and nutrients Plants obtain many of their water and nutrients from soil and it provides an place to attach to.from soil and it provides an place to attach to.

Definition of soilDefinition of soil

Soil is hard to define because it is so complexSoil is hard to define because it is so complex Soil is a natural product formed by the weathering of Soil is a natural product formed by the weathering of

rocks and the action of living organismrocks and the action of living organismDoes it include the ability to support lifeDoes it include the ability to support life

Soil is a collection of mineral and organic matter than Soil is a collection of mineral and organic matter than can support plant growthcan support plant growth

Does this include soil like material that does not support lifeDoes this include soil like material that does not support life

What if the climate at present does not support lifeWhat if the climate at present does not support life The stratum below vegetation and above hard rockThe stratum below vegetation and above hard rock

What if there is no vegetationWhat if there is no vegetation

Three dimensional matrixThree dimensional matrixSoil is a living system made up of a matrix Soil is a living system made up of a matrix of minerals and organic matter that includesof minerals and organic matter that includes plants, both roots and stemsplants, both roots and stems BacteriaBacteria FungiFungi ProtozoaProtozoa AlgaeAlgae Small animalsSmall animals Larger animalsLarger animals

A unit of soil large enough to define is A unit of soil large enough to define is calledcalled PedonPedon

Formation of soilFormation of soilProposed that five factors are involved in the formation of soilProposed that five factors are involved in the formation of soil

Parent MaterialParent MaterialIgneous rockIgneous rockSedimentary rockSedimentary rockMetamorphic rockMetamorphic rock

ClimateClimateTemperatureTemperatureRainfallRainfallElevationElevationLatitudeLatitude

Biotic FactorsBiotic FactorsInput factors from living organismsInput factors from living organismsDegradation by living organismsDegradation by living organisms

TopographyTopographyWater runoffWater runoffDrainingDrainingErosionErosion

TimeTimeWeathering, accumulation, decomposition and mineralization take timeWeathering, accumulation, decomposition and mineralization take timeInitial differentiation can be within 30 yearsInitial differentiation can be within 30 yearsFormation of true soil, 2000 to 20000 yearsFormation of true soil, 2000 to 20000 yearsSoil can ageSoil can age

Mechanical and Chemical WeatheringMechanical and Chemical Weathering Starting PointStarting Point

MechanicalMechanical WaterWater WindWind TemperatureTemperature Creates loose materialCreates loose material Sorted and movedSorted and moved

ChemicalChemical Acids produced by lichens and mossesAcids produced by lichens and mosses Addition of organic matterAddition of organic matter OxidizationOxidization etcetc

Living OrganismsLiving OrganismsWithout living organism there would be no soilWithout living organism there would be no soil Mars does not have soil as we know itMars does not have soil as we know it When plants colonized the land, they changed it by When plants colonized the land, they changed it by

producing soilproducing soil Plants introduce organic matter to soilPlants introduce organic matter to soil Microorganisms and small animals recycle the Microorganisms and small animals recycle the

organic matter to humusorganic matter to humus Humus can be on top of soil in some acidic Humus can be on top of soil in some acidic

environmentsenvironments Humus is usually mixed with the soil and changes it Humus is usually mixed with the soil and changes it

compositioncomposition Many microorganisms have evolved to fill this nicheMany microorganisms have evolved to fill this niche

ActinomycetalesActinomycetalesLignin degrading fungiLignin degrading fungi

Soil has many Soil has many layerslayers

OOOrganic layerOrganic layer

Fluctuates with seasonFluctuates with season

AAUpper layer of mineralized Upper layer of mineralized soilsoil

Large amount of organic Large amount of organic mattermatter

EEEluvial zoneEluvial zone

Maximum leachingMaximum leaching

BBIlluvial zoneIlluvial zone

Accumates leached Accumates leached material such as clays, material such as clays, silicates, etcsilicates, etc

CCUnweathered starting Unweathered starting materialmaterial

RRRock or parent materialRock or parent material

Soils show a great deal of Soils show a great deal of variationvariation

ColorColor No direct effect on how No direct effect on how

soil functionsoil function Allows classificationAllows classification

RedRed Possibly oxidesPossibly oxides

BlackBlack Possible high organic Possible high organic

contentcontent

TextureTexture Variation in size and Variation in size and

shape of soil particlesshape of soil particlesGravelGravel

>2mm>2mm

SandSand 0.05mm to 2mm0.05mm to 2mm

SiltSilt 0.002mm to 0.05mm0.002mm to 0.05mm

ClayClay <0.002mm<0.002mm

StructureStructure Space for roots etcSpace for roots etc Pore spacePore space

Amount of water heldAmount of water heldRate of water movementRate of water movementAerationAerationCompactionCompactionAggregationAggregation

Aggegates or pedsAggegates or peds

DepthDepth Depends onDepends on

SlopeSlopeWeatheringWeatheringParent materialParent materialVegetationVegetation

Grasslands are deepGrasslands are deep Forests are shallowForests are shallow

Water is essential for soilsWater is essential for soils

See lack (?) of water on MarsSee lack (?) of water on MarsSoil can become saturated if all Soil can become saturated if all pores filledpores filled

Normally at field capacityNormally at field capacityCapillary water is usually Capillary water is usually presentpresent

Extracted by plantsExtracted by plants Available water capacityAvailable water capacity Hygroscopic water unavailableHygroscopic water unavailable

DrainageDrainage Low drainage results in low Low drainage results in low

aerationaerationAll affected by soil textureAll affected by soil texture

Sand Sand Lower capacityLower capacity

ClaysClaysHigher capacityHigher capacity

Plants need minerals in the form of Plants need minerals in the form of ionsions

Cationic exchange resin Cationic exchange resin type structuretype structureChange in pH affects Change in pH affects binding capacity for ionsbinding capacity for ions ImmovableImmovable

HydrogenHydrogenAluminiumAluminium

Removable in orderRemovable in orderCalciumCalciumMagnesiumMagnesiumPotassiumPotassiumAmmoniumAmmoniumSodiumSodium

Soils vary with climate and vegetationSoils vary with climate and vegetation

EntrisolEntrisol MountainsMountains Where soil making process has Where soil making process has

been interupted by flooding etcbeen interupted by flooding etcInceptisolInceptisol

Mineral rich mountain soilMineral rich mountain soil Forests and pastureForests and pasture

AridisolAridisol Arid regionsArid regions Low in humusLow in humus Salinization due to low rainfallSalinization due to low rainfall

AndisolAndisol Volcanic in originVolcanic in origin Can be very fertileCan be very fertile

MollisolMollisol Dark organic rich A layerDark organic rich A layer Deep fertile Deep fertile

SpodosolSpodosol AcidicAcidic Coniferous forest soilConiferous forest soil

AlfisolAlfisol Temperate forestTemperate forest Organically richOrganically rich

UltisolUltisol Warm climate soilWarm climate soil Redish or yellowishRedish or yellowish Low nutriant contentLow nutriant content

OxisolOxisol Wet subtropical/tropical soil\Wet subtropical/tropical soil\ Lots of water movement through Lots of water movement through

soilsoil Low nutrientsLow nutrients

HistosolHistosol High water tableHigh water table Poor drainagePoor drainage PeatlandsPeatlands

GelisolGelisol PermafrostPermafrost

VertisolVertisol High % clayHigh % clay No B horizonNo B horizon Swell and shrinkSwell and shrink PasturePasture

Soil forms a biotic ecosystem on its ownSoil forms a biotic ecosystem on its own

Biotic System in soilBiotic System in soilNeedsNeeds

Living spaceLiving spaceVaries with soil typeVaries with soil type

OxygenOxygenVaries with water saturationVaries with water saturation

FoodFoodVaries with plant coverVaries with plant cover

WaterWaterCan vary with climateCan vary with climate

Environment is relatively constantEnvironment is relatively constant Water can change dramaticallyWater can change dramatically Mechanisms to survive droughtMechanisms to survive drought

Spores etcSpores etc

Only upper layer is really availableOnly upper layer is really availableDiversity is Diversity is very veryvery very large largeThe ecosystem is largely not understood in detailThe ecosystem is largely not understood in detail

Particularly the microorganismsParticularly the microorganisms

Man has an effect on soilMan has an effect on soil

Changes in plant coverChanges in plant cover EnglandEngland

1000 BC1000 BC ForestForest

20042004 Cities, towns, villages, farm land, monoculture forestsCities, towns, villages, farm land, monoculture forests

ErosionErosion Deforestation in AfricaDeforestation in Africa

Climate changeClimate change

DamsDams

Roads and storm drainsRoads and storm drains