EX 3 Ch 23 - Ecosystem Ecology: Terrestrial Ecosystems

Ecosystem

biotic community and its abiotic environment, functioning as a system

Ecosystem Examples

lakes, forests, tundra, tropical rain forests

Ecosystem Ecology

study of natural systems with emphasis on energy flow and nutrient cycling

Ecosystem Ecology Types

terrestrial, aquatic, wetland

Common Types of Ecosystem-Level Questions

focus on energy flow and nutrient cycling

Terrestrial Ecosystems

tropical and subtropical moist broadleaf forests, tropical and subtropical dry broadleaf forests, tropical and subtropical coniferous forests, temperate broadleaf and mixed forests, temperate coniferous forests, boreal forests/taiga, tropical and subtropical grasslands/savannas/shrublands, temperate grasslands/savannas/shrublands, flooded grasslands/shrublands, montane grasslands/shrublands, tundra, mediterranean forests/woodlands/scrub, deserts and xeric shrublands, mangroves

Primary Productivity

rate at which autotrophs convert CO2 (in atm and water) into organic compounds; energy fixed in process of photosynthesis

Gross Primary Productivity (GPP)

total rate of photosynthesis (E assimilated) by autotrophs

Net Primary Productivity (NPP)

rate of E storage as organic molecules after E is expended for cellular respiration (R); NPP = GPP - R

Climate & Nutrient Availability

primary controls on NPP in terrestrial ecosystems; specifically temp, water availability, nutrient availability; affects how much plants grow and what kinds of plants can grow (biomes)

Warm + Wet =

High NPP; plants can photosynthesize quickly and have enough water

Warm + Dry =

Low NPP; warm temps increase water demand, but lack of water limits growth

Cold =

Low PP; regardless of water, low temps slow down photosynthesis and growth

Longer Growing Seasons

have higher plant productivity because plants have more time to photosynthesize and produce biomass

More Available Nutrients =

Higher NPP

Decomposition & Nutrient Cycling

nutrients affect NPP; most nutrients are recycled; nutrients come from atm or rocks, enters soil or water and absorbed by plants, many nutrients stored in living organisms, when organisms die those nutrients return to soil as dead organic matter which feeds decomposers

Microbial Decomposers

part of nutrient cycling; mineralization of organic nutrients, minerals then available for autotrophs to take up and use to build new tissues

Key Decomposers

fungi & bacteria, mites/springtails, millipedes & earthworms

Decomposition Influences

quality of litter/organic material, soil/sediment properties (ex: pH), climate (temp, precipitation)

Biomes

biotic units that are classified by predominant plant types; at least 8 major terrestrial biomes

Tropical Rainforest - Location

rain forests restricted to equatorial zone; cover less than 2% of Earth’s surface

Tropical Rainforest - Climate

warm and very wet year-round

Tropical Rainforest - NPP

very high NPP

Tropical Rainforest

tall broadleaf evergreen trees, dense vegetation; high diversity of plant and animal life

Tropical Rainforest - Species

high diversity of plant and animal life; home to about 50% of all terrestrial species; most diverse and productive terrestrial ecosystems on our planet

Tropical Rainforest - Nutrients

most nutrients are stored in living plants, not in soil

Tropical Rainforest - Plants

evergreen trees, climbing vine, epiphytes, strangler figs; many trees grow buttresses that function as prop roots in shallow soil that offers poor anchorage; ground cover → understory → lower canopy → upper canopy → emergent canopy

Tropical Savanna - Climate & Location

warm, semiarid regions with seasonal rainfall; wet and dry seasons

Tropical Savanna - NPP

moderately high NPP

Tropical Savanna

grasses with scattered drought-resistant shrubs and trees; fire-maintained ecosystem

Tropical Savanna - Animals

large diversity of herbivores that graze or browse on vegetation; supports large number of insects, carnivores (lions, hyenas), scavengers (vultures)

Tropical Savanna - Plants

have 2-layer vertical structure (grasses and trees/shrubs); trees create small microenvironments (rescue hotspots)

Tropical Savanna - Microenvironments

“rescue hotspots;” support more biodiversity than surrounding grassland, soil is richer (more leaf litter and nutrients), shaded ground is cooler, soil holds more moisture

Temperature Deciduous Forest - Climate & Location

Moderate temp + rainfall, four seasons

Temperature Deciduous Forest - Plants

broadleaf deciduous trees dominate; seasonal changes affect plant growth; usually 4 vertical layers/strata: floor → shrubs → understory → canopy

Temperature Deciduous Forest - Nutrients

rich soils and understory of shrubs, ferns, and wildflowers

Temperature Deciduous Forest - NPP

moderate NPP

Temperature Deciduous Forest - Animals

seasonal changes affect animal behavior; diversity of animal life is associated with vertical stratification and plant growth forms; highest diversity occurs on and just below ground layer

Temperate Grasslands - Climate & Location

moderate temp, low precipitation; often experience drought as they occur in regions where annual precipitation is reduced as air masses more inland; original extent of shortgrass, mixed-grass, and tallgrass prairies in North America before arrival of Europeans

Temperate Grasslands - NPP

low to moderate NPP

Temperate Grasslands - Animals

dominated by herbivorous species; insects, large grazers, burrowing mammals

Temperate Grasslands - Grazing

grasslands evolved under selective pressures of grazing; stimulates primary production; moderate grazing can stimulate grass growth, but heavy grazing reduces productivity

Temperate Grasslands - Plants

3 strata in grassland: herbaceous plants, ground cover, and belowground root layer (can make up more than half of plant biomass and extends deep into soil

Shrublands - Climate & Location

hot, dry summers + cool, wet winters

Shrublands - Plants

shrubs and dwarf trees dominate; plants are adapted to fire and low nutrients; sclerophyllous plants are characteristic of shrublands

Shrublands - Sclerophyllous Plants

have thick, tough, and leathery leaves with waxy coating that helps reduce water loss

Shrublands - Nutrients

soils are generally deficient in nutrients

Shrublands - NPP

moderate NPP

Shrublands - Animals

drought-tolerant mammals, birds, and reptiles that use shrubs for food and shelter

Deserts - Climate & Location

very low precipitation, can be hot (Sahara) or cold (Gobi); high evaporation rates → extremely dry conditions

Deserts - NPP

low NPP

Hot Deserts - Plants

plants have adaptations to very arid climate; hot deserts range from those lacking vegetation to ones with some combination of herbs, dwarf shrubs, and succulents

Hot Deserts - Animals

animals have adaptations to very arid climate; animals avoid heat and conserve water; ex: Kangaroo rat gets water from seeds, never drinks

Cold Deserts - Plants

plants have adaptations to very arid climate; cold deserts range from vegetation dominated by sagebush, shadscale, woody shrubs and grasses adapted to cold, dry conditions

Cold Deserts - Animals

animals have adaptations to very arid climate; animals conserve heat and survive long dormant seasons; ex: Bighorn sheep has thick, insulated coat, can go long periods without drinking

Boreal Forest (Taiga) - Climate & Location

cold, long winters, short summers, about 6-10 wks warm enough to photosynthesize; primarily occupies formerly glaciated land; as temp decreases and growing seasons shorten toward Arctic, trees become fewer, shorter, and more widely spaced

Boreal Forest (Taiga) - Plants

dominated by evergreen conifers, needles prevent water loss, conical shape sheds snow; as temp decreases and growing seasons shorten toward Arctic, trees become fewer, shorter, and more widely spaced

Boreal Forest (Taiga) - NPP

low NPP

Boreal Forest (Taiga) - Animals

unique animal community; herbivores include caribou, moose, snowshoe hare, red squirrels, and porcupine; predators include wolf, lynx, pine martin, and owls

Tundra - Climate & Location

very cold, very low precipitation

Tundra - Plants

dominated by small shrubs, grasses, herbs, mosses, and lichens; vegetation structure is simple; few species and slow growth; only species that can withstand constant soil disturbance, buffeting by wind, and abrasion by wind-carried particles of soil and ice can survive; arctic plants propagate almost entirely by vegetative means

Tundra - Animals

low animal diversity, dominant vertebrates are herbivores

Tundra - NPP

very low NPP