Plant-Environment Relationship

HO Pui-sing

Contents

Development of PlantsEquatorial / Tropical Rain ForestTropical Desert VegetationLocal Plant-Environment RelationshipThe Relationship of Biomes to Ecolines

Development of Plants

Classification of PlantsFactors affecting plants development

Classification of Plants

Life form of plantsTreesShrubsLianasHerbs

Vegetation structureForestWoodlandLichens

Factors affecting development

Plant habitatsWater availabilityTemperatureTimeHuman

Plant habitats

Plants affect landform and soil (Env.)Different conditions of slopes, drainage and soil type will create different plant environment = plant habitats

Water availability

Types of plantsXerophytesHygrophytesMesophytesTropophytesDeciduous plantsEvergreen plants

TemperaturePlant growth: photosynthesis, flowering, fruiting and seed germinationWater availability: rate of transpiration and evaporationDamage: damage the cell tissues for too coldFrontier: a boundary which a plant species cannot survive.

Time

Plant and animal communities succeed one another on the way to a stable endpoint, making up an ecological successionClimax vegetation (climatic control)Subclimax vegetation (non-climatic control)

Reason for succession

Results of species competition in a given environment.Populations of well-adapted species replace earlier ones now less well equipped to compete in the altered conditions.There is a gradual change in the community.

Process of succession

Pioneers (annual herbs, weeds)Grasses and shrubsPine seedlingsPine forestBroad-leaved deciduous trees (oak forest) Climax forestClimax community = balance between Vegetation and physical environment.

Process of succession

Deciduous forest (Climax)Pine seedingsGrasses & ShrubPioneers

Process of succession

Patterns in successional processesDevelopment of soil matureHeight of plants increases and strata clear developedBiomass (productivity) increaseSpecies increasesCreate new micro-climatesSpecies replace one another (succession)Climax community forms (stable, balance)

Human impact on vegetation

Clearing forest disturbs the climax vegetationIntroduce new plant diseaseExtinction of a original plant speciesChanging soil structure and propertiesReasons: farming, mining, urbanization and industrialization…….

Tropical Rain Forest

http://www.radford.edu/~swoodwar/CLASSES/GEOG235/biomes/rainforest/rainfrst.html

Amazon Basin

Congo Basin

South-east Asia

Natural EnvironmentHigh insolationMonthly temperature between 26oC and 27oCAnnual rainfall usually more than 2000mmConvection Rain is commonHot and wet throughout the year

Characteristics of TRF Vegetation

Evergreen forestVegetation LayersLeavesDrip-tipsRootsCauliflory

Evergreen

No Seasonal variationLeaf-growth, flowering, fruiting, leaf-fall…….go on continuouslyTrees can live to a great age

Vegetation layers

Middle Layer

Emergents Layer

Canopy Layer

Shrub Layer andUnderstorey

Vegetation LayersEmergent layer

very tall tree with broad crown (30-40m)few in number

Canopy layera continuous cover (20m)

Middle layeryounger trees (5-15m)

Shrub layer and undergrowthlittle growth because of shade

Leaves

Uniform, dark green, glossy, leathery, oval and broad-leavedStrong insolation and transpiration a heavy cuticle leathery.

Waxy Leaves and Drip-tips

Buttress Roots

Caulifory

Types of vegetationTree speciesEpiphytesParasitesTree FernsUndergrowthSaprophytesMangrove swamps (riverine)

Trees and Climbers

Epiphytes and Parasites

Undergrowth

Mangrove

Mangrove swamps Prop-roots

Radicle

Tropical Desert Vegetation

Natural EnvironmentAmong the driest places on earth (<250mm)Mean annual temperature above 18oC Low relative humidity Irregular and unreliable rainfall Highest percentage of sunshine of any climate Large diurnal temperature range Highest daytime temperature of any climate Annual precipitation < half the annual potential evapotranspiration

Tropical Desert Vegetation

Characteristics of the vegetation

Types of vegetation

Characteristics - MorphologicalExtensive root systems (vertical or horizontal)Deeply penetrating roots reach permanently wet soil or ground water storeHorizontal roots may extend for 5-20mLow shoot-to-root ratio (1:3.5 to 1:6)Special leaves (small, roll, spiny and shed foliage) for reduce transpiration and preserve water.

Characteristics - Anatomical

Cuticularisation produces a watertight and waxy-like surfaceLignification provides mechanical supportLow, rounded shapes can reduce damage by strong windMany hairs

Characteristics - others

Sparsely distribution for not enough water supplyLow biomass, few species, lack of competition

Types of vegetation

Ephemeral annualsSucculent perennialsNon-succulent perennials

Ephemeral annual50-60% of desert plantsComplete its full life cycle within 6-8 weeks (short life cycle)Small size, shallow rootsFast germinating, growing, flowering and seedingExtensive germination immediately after precipitationEg. Desert plantains, desert fescue

Ephemeral annual

Succulent perennials

Enlarge the parenchyma tissues with the addition of waterStems and leaves allow store water during rainy seasonStomata are closed during day and open at nightEg. Catus

Succulent perennials

Non-succulent perennials

Can be divided into three typesEvergreensDrought-deciduousCold-deciduous

Commonly found where a little water is available. (wadis, oases, perennial rivers)Eg. Tamarisks, acacias, grasses, palms

Non-succulent perennials

Local Plant-Environment Relationship

Altitude zones of vegetationThe local variation of vegetation in TRFThe local variation of vegetation in desert

Altitude zones of vegetationVegetation changes with an increase in elevation because the following reasonsTemperature dropsRelative Humidity increasePrecipitation increase Orographic rain in windward slopeRain shadow in leeward slope

continuesLight intensive and day time increaseOutgoing radiation at night increaseLarge diurnal range of temperaturePermanent snowcaps exist on very high Mts.Faster wind speedAspects – South facing slope vs. North facing slope

Altitude zones of vegetation

Altitude zones of vegetation

Tropical Mountains

Tropical Mountains

Hot country <1000m

Temperate country 1000-1800m

Cold country 1800-3500m

Snow country or frost country >3300m

Mid-latitude Mountains

Mid-latitude Mountains

Montane Zone (<2000m)Submontane, montane, high montane

Subalpine Zone (2000-2700m)

Alpine Zone (2700-3700m)

The Local variation in TFRPoor drainge (Swamp)

Various kinds of stilt rootsPeat soil

The local variation in Desert

Near Water courses more vegetationPlant can be established in stable sand dunesEphemerals grow in thin soilSucculent and non-succulent need a thick soil

Biomes to EcoclinesBiomes are “the world’s major communities, classified according to predominant vegetation (Climax) and characterized by adaptations of organisms to that particular environment.”Ecocline is a gradient along which communities and environments change.Ecotone is a transition zone between two ecosystems.

The main biomes

Tropical rain forestSavanna or tropical grasslandDesertTemperate forest (evergreen / deciduous)Temperate grasslandConiferous forestTundra

EcoclineTemperature change and water availability

are the most important factors affecting ecocline pattern.

Ecocline (Equator to North Pole)