Ecology 15Ecology 15Forests, Woodlands and Forests, Woodlands and

SavannaSavanna

Ralph KirbyRalph Kirby

Ecosystems where trees Ecosystems where trees are dominant or codominantare dominant or codominant

Forests, Woodlands and Forests, Woodlands and SavannasSavannas

ForestsForests– Where trees form Where trees form

a closed canopya closed canopy– Most widespreadMost widespread

Requires enough Requires enough moisture to moisture to support large support large treestrees

Specific bands – Specific bands – pole to equatorpole to equator

– ConiferousConiferous

– Temperate Temperate deciduous deciduous (warm and cool(warm and cool

– TropicalTropical

Warm aseasonal Warm aseasonal environmentenvironment– Tropical ForestTropical Forest– Evergreen broadleaf Evergreen broadleaf

treestrees

SeasonalitySeasonality– Dry tropical forestDry tropical forest– DeciduousDeciduous– ConiferousConiferous

Trees get smaller Trees get smaller as seasonality as seasonality increasesincreases– Actual Actual

Evapotranspiration Evapotranspiration raterate

Productivity and Productivity and Decomposition Decomposition increase as the increase as the places get places get warmer and warmer and wetterwetter

Note differencesNote differences– LitterfallLitterfall– Forest floor Forest floor

biomassbiomass– Turnover time for Turnover time for

decompositiondecomposition

Seasonality and Tropical ForestSeasonality and Tropical Forest

Tropical Forest has been divided into various typesTropical Forest has been divided into various types– Boundary not clearBoundary not clear– Not continuousNot continuous– Broken by lack of moistureBroken by lack of moisture

Tropical Rain ForestTropical Rain Forest– Lowland (<1000 m)Lowland (<1000 m)– Mountain (>1000 m)Mountain (>1000 m)– CloudCloud

Very high altitudeVery high altitude– SwampSwamp

Wet soilsWet soils– PeatPeat

Nutrient PoorNutrient Poor

Tropical and Semi-tropical seasonal forestsTropical and Semi-tropical seasonal forests– 2 to 4 month droughts2 to 4 month droughts

Results in 30% loss of leavesResults in 30% loss of leavesFruits at the staFruits at the sta

Tropical Rain ForestTropical Rain Forest– Very high diversity of microbial, plant and animal lifeVery high diversity of microbial, plant and animal life

10 square km10 square km– 1500 species of flowering plants1500 species of flowering plants– 750 species of trees750 species of trees– Richest – Malaysia – 7900 speciesRichest – Malaysia – 7900 species

– StratificationStratificationCan be difficult to define Can be difficult to define

– Crowns of emergent treeCrowns of emergent tree– Mop top treesMop top trees– Conical top treesConical top trees– Shrubs, young trees, tall herbs and fernsShrubs, young trees, tall herbs and ferns– Tree seedlings, low herbaceous plants and low fernsTree seedlings, low herbaceous plants and low ferns

Many plants use the trees for supportMany plants use the trees for support– All shallow rootedAll shallow rooted– Mycorrhirae are importantMycorrhirae are important– EpiphytesEpiphytes

NicheNiche– StranglersStranglers

Whole treeWhole tree– ClimbersClimbers

Usually where disturbedUsually where disturbed

Continuous changesContinuous changes– Trees dieTrees die– Trees fallTrees fall– Gap appear and disappearGap appear and disappear

StratificationStratification– Supports greater diversity of animal lifeSupports greater diversity of animal life

Above canopy groupAbove canopy group– Insectivorous and carnivorous birds and batsInsectivorous and carnivorous birds and bats

Canopy groupCanopy group– Birds, fruit bats, mammals who eat leaves and fruitBirds, fruit bats, mammals who eat leaves and fruit

Below canopy groupBelow canopy group– Flying mammals, birds and batsFlying mammals, birds and bats

Middle groupMiddle group– Squirrels and such that move between group and canopySquirrels and such that move between group and canopy

Forest FloorForest Floor– Large herbivores and carnivoresLarge herbivores and carnivores

Ground GroupGround Group– Small insectivorous, herbivorous, carnivorous and omnivorous ammalsSmall insectivorous, herbivorous, carnivorous and omnivorous ammals

Deciduous ForestDeciduous Forest

Once covered most of Europe, China, North and Once covered most of Europe, China, North and South AmericaSouth AmericaLargely cleared by humansLargely cleared by humansRemaining only semi natural with few exceptionsRemaining only semi natural with few exceptionsTwo TypesTwo Types– Beech-Oak-HornbeamBeech-Oak-Hornbeam– Oak-HornbeamOak-Hornbeam

More acid soilsMore acid soils

Temperate Evergreen Forests in Subtropical areasTemperate Evergreen Forests in Subtropical areas– AustraliaAustralia– New ZealandNew Zealand– PatagoniaPatagonia

Temperate Deciduous ForestTemperate Deciduous Forest– Four strata in uneven aged standsFour strata in uneven aged stands– Even aged stands show poor separationEven aged stands show poor separation

Canopy of dominant and codominant treesCanopy of dominant and codominant treesLower Tree CanopyLower Tree CanopyShrub LayerShrub LayerGround layerGround layer

– Animals inhabit various layers but less diversity than tropical forestAnimals inhabit various layers but less diversity than tropical forest– Light intensity in different areas varies with seasonLight intensity in different areas varies with season

Spring gives most light to groundSpring gives most light to groundDarkest for ground in midsummerDarkest for ground in midsummer

– Microclimate variationMicroclimate variationHighest temperatures in canopyHighest temperatures in canopy

– Humidity varies with seasonHumidity varies with seasonHighest in summerHighest in summerHigher during night than dayHigher during night than day

Coniferous ForestsConiferous ForestsWide variety of Wide variety of environemntsenvironemnts

– MountainsMountains– Cool Temperate RegionsCool Temperate Regions

Simple Vertical StructuresSimple Vertical Structures– Three types of crownThree types of crown

Straight cylindrical trunks Straight cylindrical trunks with varying crown densitywith varying crown density

– Scots pineScots pine

Spiral shapedSpiral shaped– Douglas firDouglas fir– CedarsCedars

Deciduous conifers with Deciduous conifers with pyramidal open crownspyramidal open crowns

– LarchLarch

Little vertical structureLittle vertical structure– Sharp reduction in lightSharp reduction in light– Does not changeDoes not change– Some stratification for birdsSome stratification for birds

Temperature variationTemperature variation– Changes with type of forestChanges with type of forest

Dominant in northern Dominant in northern latitudeslatitudes

Boreal ForestBoreal ForestConiferous Forest that dominates northern latitudesConiferous Forest that dominates northern latitudes– 11% of terrestial surface11% of terrestial surface– Highly influenced by seasonal freezing and thawingHighly influenced by seasonal freezing and thawing

Permafrost in northPermafrost in northWet in summer due to thawingWet in summer due to thawing

– Tundra southwardsTundra southwardsForest-TundraForest-TundraOpen borealOpen borealMain borealMain borealBoreal-mixed forestBoreal-mixed forest

– Simple StructureSimple StructureSpiral spruces and firsSpiral spruces and firsOpen pinesOpen pinesLarchLarchShallow rootsShallow rootsFire importantFire important

– Unique but simple animal communityUnique but simple animal communityLarge herbivoresLarge herbivoresGround birdsGround birdsSome large carnvioresSome large carnvioresHerbivorous insectsHerbivorous insectsNesting ground of many neotropical and tropical birdsNesting ground of many neotropical and tropical birds

Changes in Environment affect Changes in Environment affect ForestsForests

High results in change from deciduous to High results in change from deciduous to coniferousconiferousReduced soil moisture gives rise to woodlands in Reduced soil moisture gives rise to woodlands in temperate regionstemperate regions– Increased diversity of habitats and speciesIncreased diversity of habitats and species

Reduced soil moistures gives rise to savannas in Reduced soil moistures gives rise to savannas in tropicstropics– High biomass of grassesHigh biomass of grasses– Still lots of trees but spread outStill lots of trees but spread out– Driven by seasonalityDriven by seasonality– Unique herbivores Unique herbivores

Grassland, Shrubland, Grassland, Shrubland, Desert and TundraDesert and Tundra

Decrease in available Decrease in available water changes Forest to water changes Forest to Grassland in Temperate Grassland in Temperate zoneszones– 250mm to 800mm of 250mm to 800mm of

rainrainNote difference between Note difference between created and natural created and natural grasslandsgrasslands– Europe – stableEurope – stable– America – revert to America – revert to

forestforestGrasslands varyGrasslands vary

Tallgrass prairieTallgrass prairie– Near forestNear forest

Shortgrass prairieShortgrass prairie– Great plains of USGreat plains of US

Desert grasslandDesert grassland– 300-400 mm rain300-400 mm rain

SteppeSteppe– AsiaAsia– 500-600 mm rain500-600 mm rain

PampasPampas– South AmericaSouth America– 450-900 mm rain450-900 mm rain

VeldVeld– Southern AfricaSouthern Africa– 1500-2000 metres1500-2000 metres

Vertical structure of Vertical structure of grassland changes grassland changes with seasonwith seasonVarious layers Various layers containing different containing different plantsplantsAs plants grow out As plants grow out of winterof winter– At the groundAt the ground

Light Light decreasesdecreasesTemperature Temperature decreasesdecreasesHumidity Humidity increasesincreasesWind Wind decreasesdecreases

Thatch Thatch accumulatesaccumulates– Slow Slow

decompositiondecomposition3 to 4 years3 to 4 years

Burning importantBurning important– Removes thatch Removes thatch

and mulchand mulch– As does grazingAs does grazing

Complex root Complex root systemssystems– Half plant below Half plant below

groundground

Natural and domestic Natural and domestic grassland support a very grassland support a very wide diversity of lifewide diversity of life– Large ungulatesLarge ungulates

Example: bison in USExample: bison in US

Eurasian too originallyEurasian too originally

Africa: Zebra, Rhino, etcAfrica: Zebra, Rhino, etc

Productivity and nutrient Productivity and nutrient cycling controlled by cycling controlled by droughtdrought– Best >800mm rain and Best >800mm rain and

>15>15ooCC

All grassland have evolved All grassland have evolved under grazing pressure under grazing pressure together with droughttogether with drought

ShrublandShrublandDifficult to characterizeDifficult to characterize– Created by manCreated by man– Created by disturbanceCreated by disturbance– Part of arid gradientPart of arid gradient

Shrubs have an advantage over trees in arid areasShrubs have an advantage over trees in arid areas– Invest less energy above groundInvest less energy above ground– Better moisture collectionBetter moisture collection– Faster growthFaster growth

Mediterranean ShrublandMediterranean Shrubland– Winter rainfallWinter rainfall

Broad leaf shrubsBroad leaf shrubsDwarfed treesDwarfed trees

HeathlandHeathland– Cold type shrublandCold type shrubland– Nutriant poor, especially nitrogen and phosphorusNutriant poor, especially nitrogen and phosphorus– Usually high altitudeUsually high altitude– Dry TypeDry Type

Seasonal droughtSeasonal drought– Wet TypeWet Type

Seasonal waterloggingSeasonal waterlogging

Animal CommunityAnimal Community– Small animals and ground birdsSmall animals and ground birds– Distinct to regionDistinct to region

DesertDesert

Diverse set of ecosystemDiverse set of ecosystemWhere evaporation exceeds rainfallWhere evaporation exceeds rainfallSemi desertsSemi deserts– 150 to 300 mm rain150 to 300 mm rain

True desertsTrue deserts– 70 to 150 mm rain70 to 150 mm rain

Extreme desertsExtreme deserts– <70 mm rain<70 mm rain

Simple physical structureSimple physical structureMoisture limits productionMoisture limits productionPlants and animals adapt to aridityPlants and animals adapt to aridityLimited plant and animal diversityLimited plant and animal diversity

TundraTundraLow precipitationLow precipitationLow temperatureLow temperaturePermafrostPermafrost100% cover and moist100% cover and moistSimple structureSimple structure

– Low diversity of plants and animalsLow diversity of plants and animals– Animals and plants well adaptedAnimals and plants well adapted– Simple structureSimple structure

ProductivityProductivity– Low temperatureLow temperature– Extreme seasonalityExtreme seasonality

Also polar desertAlso polar desert